High Power PCB Design
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No matter you are an electrical engineer, a product designer, a system integrator or a maker looking for a high power PCB design, Venture high power design team will be here to help you.
The most important rule for high power PCB design is to know your power path. The location and number of power flowing through a circuit are a key factor when deciding the IC position and type and amount of heat dissipation.
Venture high power PCB design team have helped hundreds of customers on their high power PCB designs and high current designs, we ensure your board is both electrically sound and thermally balanced for proper operation and optimum efficiency.
- We at Venture paid Special care to route high-power paths between ICs and components.
- We know that resistance in copper traces can cause significant power loss and heat generation on board if not used appropriately.
- We keep traces between power components short and wide, and we use thicker copper traces for high current paths
- We also use large copper planes and vias in the board to remove heat from devices
- We design vias to transfer power from one layer on a board to another.
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As consumer devices continue to shrink in size become more and more portable, components inside are getting smaller but providing better performance, power, and current considerations and related thermal design become increasingly important for PCB designers and board layout engineers.
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High Power PCB Design: The Ultimate Guide
In this guide, we will delve into discussing high power PCB design. An introductory section with basic definitions and features sets as off.
This will be succeeded by the identification of some of the types of high power PCB design. We shall then discuss the advantages and disadvantages of the PCB.
We further look into the layout of this design and some of the safety requirements.
We then scrutinize the prototyping, fabrication and assembly processes, before concluding with manufacturer identification
Let’s get started:
- High Power PCB Design Basics
- Types of high power PCB Design
- Advantages of High Power PCB Design
- Disadvantages of High Power PCB Design
- High Power PCB Design Process
- High Power PCB Design Tips
- Step-by-step How to Design High Power PCBs
- Fabricating High Power PCB Process
- High Power Printed Circuit Board Material
- Precautions in High Power PCB Fabrication Process
- How to Fabricate High Power PCB
- High Power Printed Circuit Board Assembly Process
- Finding High Power PCB Manufacturer
High Power PCB Design Basics
High power PCB design has gained popularity in the recent past. Previously, the design was limited to military equipment.
In this section, let us look at the definition of the PCB.
We will also look at some of its features, pros and cons, and application.
What is High Power PCB
High power PCBs are printed circuit boards made of heavy copper. This enables them to handle higher rates of current compared to other boards.
High power PCB
They are also able to resist high temperatures for extended periods. As such, they provide strong connection points.
High Power PCB Features
High power PCB designs are fabricated for specific devices.
These devices require higher amounts of current flows and are often subjected to varying temperatures.
For them to perform effectively and efficiently, high power PCB design incorporates the following features:
The copper layer in high power PCB design is thicker and heavier compared to those found in other PCBs. This gives it the ability to conduct higher currents.
Thermal heat transfer in PCB – Photo courtesy: Taiyo
This ability to conduct higher currents is coupled with the ability to dissipate heat. This helps in ensuring that no short circuits occur during operations by devices made from the board.
For these reasons, high power PCB is able to resist and adapt to fluctuating temperatures that the device is used in.
Where to Use High Power PCB
Due to their ability to conduct high rates of currents and to accommodate fluctuating temperatures, high power PCBs has many applications. Let us have a go through some of these applications.
Solar power distribution PCB
1.Solar Power Distribution
Solar power distribution boards heavily rely on high power PCBs for efficiency.
Since solar power distribution boards transmit both higher currents and voltage, they rely on high-power boards. This enables them to transmit currents effectively.
In the military, most applications need high currents and also get subjected to fluctuating temperatures. As such, it is imperative to make them using PCBs that can handle these features. These qualities can only be found in high power PCBs.
Military applications such as communication devices, satellites and radar, therefore, rely on high power PCBs for efficiency.
They are also used in armored military vehicles and fighter jets used in military operations.
In the recent past, industries have heavily relied on high power PCBs. This is because within the sectors, there is heavy reliance on high currents and voltage.
The power distribution transformers within the industry also use high power PCBs. This enables them to transmit currents effectively for the performance of the industrial machines.
Airplanes and spacecraft are subjected to fluctuating temperatures and rely on high currents and voltage to perform effectively and safely. Failure to make considerations when identifying the most suitable board can result in fatalities.
Take, for instance, the current flow during the launching of a spacecraft. This cannot be handled with any other PCB owing to the high currents involved.
Communication devices in the industry also rely on high power PCBs since they get exposed to diverse environments. This is the same case with the radar used by the control tower.
Satellites are exposed to fluctuating temperatures. To effectively perform their functions, they also need high current flows.
Other PCBs cannot sustain these factors. High power PCBs are thus used in the industry.
Types of high power PCB Design
There are quite a number of high power printed circuit boards available in the market today. Let’s look at some of the most common classification criteria.
· Double-Sided High Power PCB
These are high power printed circuit boards which allow for mounting of components on both sides. They are the entry level into more complex applications made using high power PCBs.
Double sided PCB
Using vias, they alternate routing traces between the top and the bottom layers. This makes them more efficient and dependable compared to single-sided high power printed circuits.
·Rigid-Flex High Power PCB Design
Rigid-Flex high power printed circuits are made up of both rigid and flexible circuit substrates.
More often than not, rigid-flex high power boards are composed of multiple layers of flexible substrates. These flexible substrates are then attached to either one or more rigid boards.
Rigid flex PCB design
This attachment is done either internally or externally. The intended application for high power rigid-flex board is crucial in determining how the attachment is done.
Also, the flexible components are designed to be always flexible.
This flexibility is useful in corners and areas that need extra space. Rigid substrates are helpful in areas that require additional support.
With these capabilities, there is a surety that these high power rigid-flex boards can be curved during the manufacturing and installation processes.
Rigid-flex technology gives high power PCBs the ability to fit into smaller applications. This results in enhanced performance and convenience.
·Multilayer High Power PCB Design
Multilayer high power circuit boards have at least three conductive layers. Cross circuit board plated through hole is the most commonly used electrical connection strategy in these boards.
Depending on the purpose the board is being manufactured for, the conductive layers can be as many as twelve. However, there are some companies that are now fabricating PCBs with up to 100 layers.
Multi layer PCB
This gives room for the manufacture of some of the most complex high power PCB applications.
Advantages of High Power PCB Design
Advantages of high power PCB
1)Increased Endurance to Thermal Strains
The heavy copper endowed in the high power PCB gives it the ability to endure thermal strains that it is subjected to.
Devices made of high power PCBs are hence in a position to resist thermal fluctuations, making them reliable.
This explains their preference in the manufacture of military applications.
2)Increased Current Carrying Capacity
Heavy copper also gives high power PCBs the ability to conduct high currents without much strain. High currents on PCBs with lighter copper are susceptible to failure and malfunctioning.
Devices such as power transformers are exposed to very high currents. Without high power PCBs, they are likely to fail or cause disasters.
3)Increased Mechanical Strength at the Connector Sites and in PTH Holes
Heavy copper used in the manufacture of high power PCBs gives it mechanical strength. This is very important in supporting the components that are mounted on the board.
The connector sites are more strengthened in high power PCBs. This extends to the through holes which are also made stronger by the copper.
4)Reduced Product Size
High power PCB design also helps in the reduction of the product size. This is achieved through incorporation of multiple copper weights onto the same layer of the circuitry.
This explains its preference in military applications as most products have to be portable.
5)Heat transfer to External Heat Sinks
With heavy copper plated vias, high current transfer through the board is made possible. This helps in the transfer of heat to the external heat sinks.
It makes high power PCBs the most effective board for applications that require high currents to function effectively.
The heat sinks in the high power PCB design can also be directly plated on the board. This explains the reliance on high power PCB design in industrial applications.
Disadvantages of High Power PCB Design
High power PCB design is expensive to fabricate. This is because they demand heavier and thicker copper, which is very expensive, to be able to operate effectively.
The processes involved in high power PCB design can be time-consuming. The additional features that are imperative for the effective functioning of the PCB consume time. This is unlike other simpler PCBs.
High Power PCB Design Process
In this section, we first look into circuit board layout considerations before proceeding to discuss the design tips. We then discuss the steps involved in designing high power PCBs.
High Power Printed Circuit Board Layout Considerations
The first consideration that should be made during the design process is the board layout.
Power Considerations for the Board
Establishment of the power path is the most important rule for the high power circuits.
This will be of essence in coming up with the location and amount of power that should flow through the circuit. It further informs the position of the IC and the amount of heat dissipation that is required for the board.
There are a many of factors that inform the layout for a specified design. These are:
- The first consideration should be the amount of power that is intended to flow through the circuit
- Also important, is the ambient temperature that the device and the board are designed for
- You should also consider the expected amount of airflow around the device and even the board
- Your other consideration is going to be the board material that you will use
- The last factor that is equally important is the IC density of the board that you intend to use
In the past, analog and mixed-signal circuit boards were used. They included high-power and analog blocks.
Component placement – Photo courtesy: Stack Exchange
In other instances, they included sensitive digital analog blocks which had low power.
In the first step for the layout, you should design and place power blocks.
Ensure that you keep the connections within the individual power blocks. This applies to both short and wide blocks.
As you do this, make sure that you deter unwarranted ground loops and generation of noise. Generally, make the following considerations:
- Identify the current loops in the layout. It is more important to be keener with the high current paths. Reduce these loops.
- Secondly, it will be prudent to limit the possibility of resistive voltage.
- Ensure that you locate the high power circuitry away from any other sensitive circuitries
- Most importantly, ensure that the grounding techniques used are impressive.
Apart from the mentioned layout considerations, it would also be essential to avoid lumping together different power components on board.
For the board to achieve thermal balance, ensure that you distribute these heat components evenly across the board.
This will also effectively protect the board from warping. Thus, you can be assured of reduced heat on the board and protection of sensitive circuitry.
The signals will also enjoy equal protection during operation.
IC and Component Mounting
Whenever there is power flow within a circuit, it is obvious that all the components will generate heat.
When heat is generated in the passive components and the ICs, the heat will most likely be dissipated. This heat is dissipated to cooler ambient air that surrounds the device.
IC Component mounting
This dissipation is made possible by the device’s lead frame or through the package. Most IC packages are thus designed not to leave a lot of room through which external heat sinks can occur.
Also, this calls for a method through which heat can be extracted from the device. Exposed pad is one such method. For the thermal performance to be optimal, use a die inside the package.
This die should have an EP directly connected to it. These ICs can then be mounted correctly on the board. In so doing, heat transfer from the package to the board will be optimized.
In most instances, components found within the power path will always produce enormous amounts of heat. Thus, it is important to come up with strategies through which the generated heat can be dissipated to the ambient environment.
To achieve this, you have the option of adding an external heat sink onto the board. This will enable your board to expel the heat from the device and to dissipate it into the ambient air.
These heat sinks should be made from materials with high thermal conductivity capabilities. Such materials include metals such as aluminum and copper.
Heat sink – Photo courtesy: Wikimedia
It is advisable to put these heat dissipaters along the airflow path. This will lead to a faster dissipation rate.
The positioning of the IC should be in a manner that the heat sinks are fixed in a desirable location. You can then make heat transfer optimal from the IC to the heat sink by using thermal epoxy.
This will be essential in easing heat transfer between your devices. Ensure that you create enough room on the board.
However, this is never appropriate for smaller devices or even compact applications.
Take care when routing high power paths that exist between the ICs and even the components. In case of copper traces resistance, there is the likelihood that power will be lost. Alternatively, a lot of heat may be generated.
Ensure that the traces in between power components are kept short and wide. For paths that will carry high currents, it is advisable to use thicker copper.
PCB Layout – Photo courtesy: Autodesk
Always ensure that you use large copper traces as they are the most preferred for power traces. If you use small traces for the current, the general performance will be undermined.
Large copper planes can also be used together with the vias to remove excess heat from the device.
With large planes, you are assured that the area created is enough for heat dissipation from a device. These planes are supposed to be connected either on top or the bottom of the board’s layers.
This results in maximum heat transfer to the ambient environment. However, internal planes can also be used to dissipate heat.
You can also use vias to effectively transfer power across the board’s layers. They can transfer power from package to either another plane or even layer. With multiple vias will therefore signifficantly reduce thermal resistance.
The thickness of connections between components marks another aspect in the design of high power boards. Trace thickness is an important consideration since the copper traces are likely to have resistance.
PCB Traces – Photo courtesy: SCIENCING
Trace thickness will hence inform the way through which high power designs can perform.
High power PCB designs often use thickness of about 2oz. This helps the boards in delivering full output power and dissipation of excess heat that is generated during power delivery.
High Power PCB Design Tips
Just as any other circuit board, safety precaution is the first consideration that should be made for effective operation. This is crucial when handling high power PCBs.
There are, however, some unique factors that should be considered in the case of high power PCB design.
The main concern that can potentially lead to malfunctioning is heat. These boards produce a lot of heat compared to other standard boards regardless of how you design their layout.
During the fabrication process, it is imperative to create more external vents and fans in the housing.
There is also need to install a temperature sensor on the PCB. This is an essential failsafe firmware for the PCB.
When it detects an unusual increase in temperature, you will be able to respond to overheating. It is advisable that you choose components which have low resistance.
Short-circuiting also poses a safety hazard. Since the board is supposed to drive devices of high power, short-circuiting will result in undesirable effects. You will have to consider such an eventuality in the design phase of the high power PCBs.
To address short-circuiting, fuse all outputs that leave the board. You will also have to fuse the inputs.
You will then have to rate the fuses. This will help in ensuring that the wires used handle fewer currents than they should do.
The amount of current on the board traces should also be rated to carry less or equal amounts of current. It is necessary to employ drives with built-in short circuit prevention capabilities.
·Get a Plan
Before commencement of planning for a high power circuit, and sooner than running the first trace, understand the layout. This is important for other boards but more crucial for high power PCBs.
You can first break the board into, say, high power and low power sections. In so doing, you can move all the high power traces closer to the power source.
·Trace Width Calculator
In the design of circuit boards, ensure that you have an understanding of the required minimum trace width. This is essential, especially when you are handling high powered PCBs.
Absolute minimum widths should be arrived at using IOC-2221 formula. The minimum width required should be around 142 mils.
·Remember to Use Copper Pours
Regardless of the type of the board, it is advisable to use copper pours when designing all your power nets. In the designing of high power PCB, ensure that each high power carrying net is made of a pour.
The copper pours will be of great significance as they allow an increase of copper’s width, making them fit on the board.
·Double Up the Layers
Stitching up of double layered pours together using vias is one commonly used technique. This double layer effectively creates twice the area of copper within the same area.
The use of this technique leads to an increased opportunity of building current loops. This is made possible by the section that blocks the return of current flow.
This mainly helps the surrounding copper pour during soldering.
To achieve this, you should have less copper to enable currents to flow. This is a less important matter when designing standard PCBs.
However, the benefits of the thermals still overshadow the shortcomings. For the power nets in the high power PCBs, use thermals. Combine this with solid connections.
Step-by-step How to Design High Power PCBs
PCB design software interface
Step 1: Preparation of the base material.
Before the fabrication process starts, the laminate has to be cleaned thoroughly.
This pre-cleaning is essential since the copper coils used in high power PCB design usually have anti-tarnish features. These are usually done by the vendors to offer protection against oxidation.
Step 2: Generation of the Circuit Pattern
There are two main techniques that you will use to achieve this in designing high power PCBs. These techniques include:
Screen Printing – This is the most preferred method due to its ability to produce the desired circuit patterns. This can be attributed to the fact that it is capable of depositing accurately on the laminate’s surface.
Photo Imaging – this is the oldest technique ever used in designing high power PCBs. However, it is still a commonly used method in depicting circuit traces on laminate.
This technique helps in making sure that dry photoresist film which is composed of the intended circuitry is rested on the laminate.
The resulting material is exposed to UV light. Consequently, the pattern on the photomask is transferred to the laminate.
The film is expunged from the laminate chemically. This leaves the laminate with the intended circuit patterns.
Step 3: Etching the Circuit Pattern
In designing high power PCBs, this is usually achieved by dipping the laminate into an etch bath.
Alternatively, they can be sprayed using an appropriate etchant solution. To get the required results, etching is done to both sides concurrently.
Step 4: Drilling Processes
After etching, drilling is the next step. In this step, holes, pads and vias are drilled.
To come up with precise holes, you will have to ensure that the drilling tools is high-speed. Use laser drilling methods when creating holes that are ultra-small.
Step 5: Through-hole Plating
In designing high power PCBs, this is a step that must be handled with a lot of care and precision. After the desired holes have been drilled, copper is deposited in them.
Unlike in other circuit boards, this is done in large quantities and made thicker. They are then chemically plated. The result is the formation of electrical interconnections across the layers.
Step 6: Application of Cover lay or Covercoat
Protection of both sides of the board in high power design is essential. This can be achieved by applying a cover lay.
The importance of this is the provision of protection from hostile environments. This is essential for high power PCBs as they get subjected to fluctuating temperatures. This cover lay also protects against harsh chemicals and solvents.
Polyimide film buttressed with an adhesive is the most commonly used material as cover lay. Screen printing makes it possible to imprint the cover lay on the surface.
Using UV exposure, curing is achieved. Apply controlled heat and pressure during the lamination of cover lays.
There is a striking difference between cover lay materials and covercoats. Cover lay is a laminated film while covercoat refers to materials that can be directly applied on the substrate’s surface.
There are many factors that determine the type of covering. They include the method used in the manufacturing process, the materials used and the area of application.
Both coats are essential in augmenting the whole assembly’s electrical integrity.
Step 7: Electrical testing and verification
There is a range of electrical tests that the board goes through. Scrutinize factors like performance. You will also need to assess quality using the design specifications as the threshold.
Fabricating High Power PCB Process
Proper fabrication of high power PCB design is crucial as it determines the performance of the device the PCB will be used in.
It is necessary that you first come up with a prototype of the design before rolling out production.
You must also use the correct materials in the fabrication of high power PCB. Also, there are some serious precautions to take during fabrication.
Prototyping High Power PCB
Very sensitive applications take high power PCB design. These devices are used in different industries such as aerospace and military.
Operational flaw in the high power PCB design is, therefore, likely to result in fatalities.
This makes prototyping an essential aspect of production that can effectively deter failure. Let us briefly explore the prototyping process.
The first step involved in prototyping is to come up with the design of the intended high power PCB.
PCB Design software
You then conduct a preliminary check to assess whether there are defects in the board.
This is established by referring to the schematic design. The schematic design also details the intended size of the panel and the grid.
You should convert the schematic design into a netlist. This is important as it will be essential in conducting checks throughout the process.
The subsequent step is to come up with a bill of materials.
Normally, the BOM lists and describes the materials and components that you will use during the production of the high power PCB. It serves as your point of reference as extensive details of the components are inherent in this list.
Routing is then designed through the traces. This operates effectively to connect all elements in high power PCB design.
For effective functioning of the board, it is essential to continually assess the design before you shift your focus on the fabrication phase.
One of the major issues to address, especially in high power PCB design is thermal inconsistencies. If this is not addressed effectively, then there is the likelihood of unpredictable temperatures.
You can then move on to create the photo film. Use a plotter for every layer and the board’s solder mask.
After this, print the inner layers.
In this step, you can apply substrate material with copper.
In high power PCBs, the thickness of the copper layer should be at least 2oz. This is achieved by pre-bonding copper to the substrate. Consequently, a photoresist layer is applied.
You should then align and punch precise registration holes. This is essential since it is impossible to correct inner layers after the merging of the layers. Next, fuse the layers.
You can now proceed to drill the holes.
These drills are the ones that will be used in mounting the intended components. This should be done with precision. You can use an x-ray locator to get the hole locations right.
After this, deposit a copper layer onto the surface of the panel. This process is controlled by computers.
Outer laying imaging is the next step in the prototyping process. You add a layer of photoresist. The photoresist operates effectively to make sure that the targeted parts of the board are covered with copper deposits.
Tin plating is then done to protect the copper. In the final etching step, you can use chemical solutions to wash away excess copper.
You can then apply the solder mask using epoxy solder mask ink, then expose to UV light to harden the film. The unhardened parts are then removed.
Now proceed to apply a surface finish. In this, more plaiting is deposited. This ensures that the pads are uniform.
Proceed to apply silk screen onto the surface of high power PCB design. Do this using ink-jet writing. Obtain a high power PCB from the panel.
Attach all the components on the board. Apply solder paste on the board. This will mix with the flux. Solder melts away then gets bonded to the PCB surface.
Pick and place surface mount components. You can either resort to a pick and place machine or conduct SMD.
The next step is to reflow the soldering. This is achieved by putting the high power PCB board through a reflow oven. Heaters melt away the solder found in the solder paste.
After cooling off, melted solder solidifies. SMDs are then attached to the board permanently.
You can then proceed to inspect the board as a quality control measure. This is because this soldering can undermine connection quality. There is a likelihood of electric shorts if this is not checked.
You can then proceed to insert through hole components. There are a number of high power devices that need other components apart from SMDs.
Finally, conduct a functionality test of the prototype.
After Rigid Flex PCB Prototyping: Testing the Prototype
After prototyping your high power PCB design, the next stage is testing it before rolling out its full production.
The test is conducted in accordance with the reason why it was manufactured. You should ensure there are no design flaws and identify areas that will need improvement.
If you have different designs, run each of them, and make a comparison on their performance.
If you happen to detect problems during the tests, there will be need to either correct the flaw or create a new prototype.
If the performance of the prototype turns out to be effective, you can proceed to roll out full production of the board.
High Power Printed Circuit Board Material
When manufacturing high voltage PCB design, your first concern should be effective performance in whichever environment.
You should also consider the ability of the design to handle overvoltage throughout its lifespan. You can only achieve this by using the correct materials. You will need the following materials.
High power PCB material – Photo courtesy: Stack Exchange
·Board Material for High Power PCB
The board will provide a base on which all the functionality of the PCB will rely. You will have to first consider all the factors in the design before placing an order for the materials.
Higher dielectric breakdown qualities are essential for your board. This is usually found in FR4 laminate.
All round resistance can then be obtained from BT epoxy. Assess whether it fits the intended application as it usually has strong side walls. These laminates can be costly, but you are sure to get high performance.
In high power PCB design, the first consideration should be heavyweight and ability to endure high currents and resultant mechanical stress. These are the qualities that make copper preferable.
Copper materials used should be heavy. At a minimum, they should be 4-10 oz.
In extreme situations, it should be between 10-50 oz. This applies to all copper circuits and materials.
·Resin and Glass
This is not a major component of high power PCB design. However, both resin and glass inform the durability of high voltage situations.
To achieve the best dielectric results, ensure that the resin content on your board is high. This should be coupled with relatively small glass style.
Find the option of materials that can stand high voltage environments and other environmental factors. High standards of insulation must be coupled up with materials with the ability to stand high vacuum and pressure applications.
Precautions in High Power PCB Fabrication Process
The first precaution that you should note is that solder fumes have high lead content, thus you should not expose yourself to it.
Do the soldering within an area that is enclosed. This is important to avoid releasing the fumes into the open air.
Secondly, during the fabrication process, you should ensure that the enclosed area you are working in is well lit.
Components have to be placed on the board precisely. Slightest changes have the capability of resulting in flaws for the whole board.
When the lighting is inadequate, there is the likelihood that injuries will occur, including burns from soldering iron.
PCB Fabrication machine
It is also essential to wear safety hand gloves whenever you are doing the fabrication. The hazardous chemicals involved should be handled carefully to prevent chemicals from burning the skin.
Ensure that you use the soldering iron that reaches at least a hundred degrees. Without taking into consideration these precautions, the worker’s safety is compromised.
One of the last stages in the fabrication and assembly of high power PCB is inspection and testing. You should hire a specialist to help you do this successfully if you are fabricating on your own.
Also, you may use portable appliance apparatus in testing.
Further, when testing high power PCB design, ensure that the power and the voltage are functioning appropriately. Ensure that you check the connections before you plug the PCB into power.
If these factors are not taken into consideration, then there is the likelihood of short-circuiting.
Be sure to use the right engineering tools in the assembly process. One such tool is the exhaust hood. It will be imperative to check out on the hood monthly to ensure that they are fully functional.
The manufacturers should ensure that they train their employees regularly. This training should clearly spell out potential hazards.
The workers should know how to handle work-related. They should also be encouraged to report any emerging disease relating to the work they are doing.
Let the workers wear safety goggles during the working period. This will effectively prevent eye injuries that are commonly caused by metals involved and fumes emitted during the etching process.
These workers will indeed be exposed to several chemicals when fabricating the high power PCB design. When such diseases are reported, they can be easily handled since the cause will be identified.
Remember you are fabricating high power PCBs. You will, therefore, have to ensure that the copper used is thick enough. Failure to take this consideration will make high power PCB design obsolete.
How to Fabricate High Power PCB
The fabrication of high power takes a rather similar process as that of other PCBs. I have just listed the steps below, as most of them are already explained as part of the prototyping process.
However, at the end of the list, we shall discuss some special considerations that apply to the fabrication of high power PCBs.
So these are the steps involved
- Printing Inner Layers
- Aligning Layers
- Drilling Holes
- Copper Plating
- Outer Layer Imaging
- Copper and Tin Plating
- Final Etching
- Applying Solder Mask
- Applying Surface Finish
- Applying Silkscreen
- Cutting Board
Let us then look at some essential and special considerations when fabricating high power PCBs.
1.Heavy Copper Circuit Construction
In high power PCB design, heavy copper circuits are used. This usually requires special etching techniques.
Turnkey high power PCB design
The techniques used for plaiting here are also quite different than those used for other PCBs. Use high-speed plating and differential etching.
In the past, heavy copper qualities could not form straight lines. However, in the recent past, this has been addressed by combining plaiting and etching.
When you plate heavy copper circuit, you can proceed to increase the thickness of the board. You can also mix heavy copper with the standard features that can be found on the single board.
This is also referred to as a power link. This will translate into a number of advantages, including a reduced number of layers. Power will also be distributed efficiently.
This will also allow you to incorporate both high current circuits and control circuits on the board. Also, this gives you a simple board structure.
Another advantage that you will realize is that to the standard circuits, you can easily connect copper features.
2.Current Carrying Capacity and Temperature Rise
Estimate the maximum currents that can be easily carried by a trace. This can be established by finding out a way through which you can estimate the rise in heat. This is associated with the currents you apply.
The most desirable situation is that in which a stable operating temperature is reached. In this, the heating rate is equal to the cooling rate. You are good to go when your circuit can withstand temperatures of up to 100°C.
3.Circuit Board Strength and Survivability
You can choose from a number of dielectric materials. These include FR4, which has an operating temperature of up to 130°C. Another dielectric material is high-temperature polyimide, which can operate in temperatures of up to 250°C.
Higher temperatures calls for the use of exotic materials to enable them to survive the extreme conditions.
Several methods can be used to test and determine the thermal integrity of the finished products. One of these methods is the use of thermal cycle testing.
This helps in checking the resistance of circuits when going through air-to-air thermal cycling. This cycling is checked from 25°C to 260°C.
Increased resistance can result in a breakdown of the electrical integrity through the cracks found in the copper circuit. For this test, ensure that you use a chain of 32 plated through holes.
This is because they are considered as the weakest point within circuit, especially when they are subjected to thermal stress.
Heavy copper circuits usually reduce or eliminate the failures inherent in these boards. This is because the copper circuits can become impervious in the phase of mechanical stresses that occur as a result of thermal cycling.
Heat is usually generated during the operations of the electronics. This has to be dissipated from the source and gets radiated to the outer environment. If this is not done, then the components can overheat, resulting into failure.
Heavy copper can help reduce heat. It conducts heat away from the components, which reduces failure rates dramatically.
Employ heat sinks to achieve appropriate heat dissipation from the heat sources. Heat sinks will equally dissipate heat away from the source from which it is generated. This is done by conducting and emitting heat to the environment.
Connection is made using copper vias with the area with bare copper on one side of the board.
Classical heat sinks can be bonded on to the base surface of copper. This is achieved through thermally conductive adhesive. In other cases, they are riveted or bolted.
These heat sinks are usually made of copper or aluminum. Built-in heatsinks are created when manufacturing high power PCBs. This needs no additional assembly.
With copper circuit technology allows the addition of thick copper heatsinks on any part of the board’s surfaces.
High Power Printed Circuit Board Assembly Process
Assembly of high power PCBs leads us to the final product. This entails sourcing for various components to be used in the PCB.
This is succeeded with an elaborate PCB assembly technique.
High power PCB assembly
Sourcing Components for High Power PCB
High power PCB design components are the essential parts that you will need for proper functioning for your PCB.
You may not be able to produce all the required components on your own. This leaves you with the option of outsourcing.
For you to effectively source for the high power PCB design components, first come up with the bill of materials.
This will equip you with a comprehensive list of all the components that you are supposed to source for. This is also an important tool in mitigating chances of omissions.
Now proceed to source for the components. Several authorized dealers manufacture these components.
You can do a market survey by looking into turnover capabilities of respective companies.
With other considerations also, such as the ability to ship the components, you will settle on the best manufacturer or supplier.
Having considered all these factors, you are sure to get components that will meet your needs.
High Power PCB Assembly Techniques
There are two main techniques used in PCB assembly:
- Automated PCB assembly
- Manual PCB assembly
- The third option is a combination of the two techniques, called mixed PCB assembly.
Automated PCB Assembly
In automated PCB assembly, state of the art machines are used to mount and solder power PCB components into the board. One such machine is the pick and place machine.
It also involves sophisticated processes like reflow soldering and the application of automated solder stencil.
At the end of the assembly process, the inspection methods involved are also very hi-tech. They include Automatic Optical Inspection (AOI), and the use of X-ray inspection machines.
Due to the full high total mechanization of the process, it is usually highly efficient and, with very limited defects and inconsistencies.
However, this method is not perfectly effective on its own since high-power PCBs usually have some components that require manual soldering. Boards with through hole components on both sides will, for example, need manual soldering, especially on the second side of the board.
Manual PCB Assembly
As the name suggests, this method involves manually inserting through hole components’ leads into the through holes. The components are then soldered either manually or by wave soldering.
In this process, one person assembles one or a few components, then passes the board to another person, who also assembles some components. The human conveyor belt continues until all the components are assembled.
The inspection method here is purely manual, mainly depending on visual examination of the board.
This method is usually very slow. It also leads to relatively many mistakes since human are prone to error. Manual inspection is never perfect, and can lead to inferior PCBs getting into the market.
Mixed PCB Assembly
Because of these inadequacies of the two pure methods, the most widely used technique in high-power PCB assembly is the mixed method. This method combines the strengths of the two pure techniques to come up with the best possible outcomes.
The procedure for mixed High-power PCB assembly goes as follows:
High power PCB Assembly
Step 1: Solder Paste Stenciling
This is the first step in high power PCB design assembly. It involves the application of solder paste on to the board. So you first place a thin layer stainless steel layer over the high power PCB.
This gives you room to apply solder paste onto the intended parts of the high power PCB design. These are the parts on which you will mount the components.
The solder paste used is made of a grayish substance which contains tiny metallic balls, called solder. Mix the soldering paste with a flux — this aids in melting of the and subsequently leads to surface bonding.
You should make sure that you apply the solder paste at intended places with precision. To achieve this, you can use a mechanical fixture. This will enable you to hold the high power PCB design and the solder stencil in place.
By the aid of an applicator, place precise amounts of the solder paste in the predetermined areas.
The machine spreads the paste evenly on the stencil. You can then proceed to remove the stencil. The predetermined locations will be left covered by the solder paste.
Step 2: Pick and Place
After a successful solder paste application on the high power PCB design, the assembly process proceeds to a pick and place machine.
In this step, a robotic device is used to mount SMT components onto the high power PCB board.
Next, you then solder the SMDs onto the board’s surface.
You can do this by hand picking and placing, which was very popular popularity in the past. However, it is better to use a machine, as it guarantees a quicker turnaround time, and is never fatigued.
With a vacuum grip, the machine will place SMT components to the surface of the high power PCB.
You then place the PCB on a conveyor belt that moves it through an oven. This melts the solder to allow it to connect the components with the board.
Next, pass the PCB through cooler heaters, where the melted cools and solidifies. This creates permanent solder joints between the board and the components.
Step 3: Inspection and Quality Control
After the soldering of the surface mount components to the high power PCB, subject the board to functionality tests.
The movements on the PCB during reflow can result in connectivity issues. This can cause electrical shorts.
The inspection methods at this level include the following.
Manual checks-you can conduct a visual inspection after the reflow process.
This method is only feasible in instances that you have a small number of these PCBs to inspect. The method is, however, unreliable when handling a large number of boards.
Also, the second method is the automatic optical inspections. This is the most preferred inspection method when handling a huge number of high power PCB batches.
The machine applies high powered cameras to assess your high power PCB.
The cameras are strategically located to view the solder connections. In fact, the cameras use different light colors to depict the quality of the solder. This happens at a relatively high speed.
Normally, these capabilities make it faster, enabling the inspection of many boards within a short time.
Additionally, the third method is X-ray inspection. Although this method is not very common, it is the most effective for complex multilayer high power PCB boards.
This method grants the viewer an opportunity to visualize the lower layers. As a result, you will be able to detect potential flaws.
The subsequent step is the testing of the parts. This is done to ensure that all parts are performing as intended. The high power PCB connections are tested to ascertain quality.
Do this regularly after doing the reflow process. It will help you identify potential problems which you will have to address. This will save you time and labor.
Step 4: Through-Hole Component Insertion
In some instances, some high power PCB designs have components that may not be SMDs. These are the plated through-hole (PTH) components.
PTHs are holes plated through the board. This aids in the passing of signals from one side of the board to the other.
Solder paste cannot effectively stick on the holes, but instead goes through the hole. That is why component leads are the best means to help pass signals through the board.
There are many techniques that you will use to solder these components to the high power PCB design.
The first of these techniques is manual soldering. This is a straightforward process. You can have many people, each assigned a particular component, which he places and then passes the board to a different person. Alternatively, one person can place all the components.
The second method is wave soldering. This presents an automated version of the previous technique that involves a number of processes.
After positioning a PTH component in place, the board moves to another conveyor belt.
This runs the board through an oven in which the board’s bottom is washed with molten solder, applying it to all the component leads. This is restricted to single-sided PCBs. For double-sided PCBs, the second-side components will need manual soldering.
Step 5: Final Inspection and Functional Test
This step tests the functionality of the board. The high power PCB goes through simulations that are similar to the function it will perform.
Power and the simulated signals are run through the high power PCB. The electrical characteristics are tested using testers. Any fluctuations in the voltage signal output and other factors is an indication of failure.
When there is a failure, you will decide on the next step to take. It will all depend on your set standards and the severity of the fault. The failed high power PCBs can either be improved on or be disposed of.
Disposal means that you will have to restart the assembly procedure. That is why various tests are recommended before reaching this last stage.
Finding High Power PCB Manufacturer
High power PCB Manufacturer
Experience and Expertise
The total number of years of experience that a manufacturer has worked informs the quality of the high power PCB they can produce. Experienced manufacturers are likely to be well equipped owing to the years in service.
This will also inform the quality that the expert will produce. With expertise and experience, you are sure to get high-quality high power PCBs.
Being a special type of PCB, not all PCB manufactures fabricate high power PCBs. Many companies do not have the requisite production facilities. They also sometimes lack adequate manpower.
You should find one company that can do both the prototyping and production. Thus, it is imperative that you identify a manufacturer that specializes in this kind of PCB.
Technical expertise and specialization of staff in the manufacture of high power PCB design is one desirable quality. Getting a manufacturer with qualified staff who are accredited and experienced is essential.
After production, the manufacturer should be able to make follow-ups on whether the PCB is functioning as intended.
When they come in such instances, they will help you out with experienced hitches and shortfalls.
Market prices for the manufacture of high power PCB designs are accessible from different manufacturers’ websites. You can compare the prices to determine the cost range for these products.
With this knowledge, you can gauge and negotiate prices with the manufacturers.
Extremely high prices would be an indication of extortion. Extremely lower prices on the other end could be an indication of ineptness, leading to an incomplete BOM.
High Power PCB Packaging
In some instances, manufacturers sell high power design components in very large packages than you require. Every client desires to get a package they require. If you don’t consider this, then you will end up paying for what you don’t need.
Shipment of high power PCBs can be tricky. This is because they are delicate and very sensitive.
Packaging should hence be done with a lot of care before the PCBs are dispatched to you. Look for a manufacturer who provides shipping services for clients like you. There is a likelihood that such manufacturers can pack their products in order.
Provides PCB quote faster
With experience and expertise, it can never be difficult to quote costs faster. Manufacturers with these qualities can come up with the BOM quite soon and with precision. With this, they can provide the quotation fast enough.
In the recent past, high power PCB designs have gained popularity. We have discussed these PCBs detailing the processes involved in their fabrication.
We further looked into their design stages and identified the importance of prototyping of the PCBs.
With this comprehensive overview, you are now in a position to make informed decisions when it comes to issues like sourcing.
You are also able to choose the best type of high power PCB design that will offer you the optimum required performance.