LED PCB Design

LED PCB is a printed circuit board, mostly made of aluminum, on which light emitting diodes (LEDs) are embedded.

And, to buy high quality LED printed circuit boards, it is important to understand how they are made i.e. LED PCB design process.

Today’s guide focuses on the fundamental aspects of the LED PCB design process such as material selection, design software, thermal control, uses, and design guidelines among other fundamental aspects.

Let’s get started:

Advantages of LED PCB Design

LED PCBs is often the ultimate choice of many engineers and designers tasked to upgrade or revise the product.

These are the reasons behind its popularity.

LED PCB

• Allows for the generation of light without a lot of heat being generated in the process
• The design of LED membrane switches allows for simpler sourcing and assembly of products.
• Has high resistance to both moisture and dust effects
• The consumption of power is low and efficient, thus energy-saving
• There is a variety to choose from in terms of sizes, colors and intensity
• You can easily integrate it into assemblies of complex interface
• Has a very lightweight and is thus effortlessly portable
• Low profile and high stability
• LED PCB design offers the most affordable backlighting for symbols and icons
• Has a long lifetime and thus is cost-saving in terms of maintenance and replacement
• Backlit LED PCB design is lower cost, compared to other printed circuit boards
• Usable in both silver and copper flex membrane
• A lot of design freedom, even in complex assemblies

Disadvantages of LED PCB Design

LED PCB is usually designed with large locks of copper at the driver side of the board. This usually poses the risk of warping if not well checked.

Round LED PCB

The complexity of the LED PCB design, especially the high density of the pads, puts the board at many other risks.

The design also presents thermal limitations for LED lighting.

Also, the lifespan and efficiency of LED lights is determined by the temperature at which they operate.

There is, therefore, need for more efficient thermal management in the design of the LED PCBs.

Where to use LED PCB Design

LED flood light

1.LED Strip PCB Design

An LED strip is a flexible or rigid PCB with SMD-LEDs on its surface.

Critical factors in the design of LED Strip PCB include water resistance, and voltage and current considerations. The color difference and whether the LED is addressable also influences the design.

Options here include: Single color, non-addressable; Dynamic Tunable white, non-addressable; Multicolor, non-addressable and RGB, addressable

LED strip PCB design is important in applications such as decorative lighting and fluorescent lighting. LED strip is also used in the manufacturing process for ultraviolet inspections.

2.SMD LED PCB Design

SMT LEDs are used in a wide range of electronic equipment. These include computers (notebooks), network systems and cellular phones.

Like the other LED PCB design options, these PCBs have excellent heat dissipation.

3.LED Street Light PCB

These PCBs are explicitly designed for street lighting. The technology here includes variable message signing (VMS), which is useful in traffic guidance setups.

With LED lighting, it is easy to achieve uniformity of luminance. This helps in perfecting visibility in the night. They also help in traffic control

Therefore, LED street light PCBs are designed to ensure perfect street illumination and communication (signalization).

4.PCB Design for LED Bulb

Among the most common applications of LED PCB is in making LED bulbs. This is the technology behind most of our bulbs today.

The LED PCB design for bulbs is used in many LED light products, including LED panel light and LED floor light. This design also achieves LED ceiling light.

5.LED Matrix PCB Design

LED matrix is a type of dot matrix that presents a large display. It also exhibits low-resolution value.

It has a 2-d matrix of diodes with cathodes that are lined up in rows, while the anodes are joined in columns.

The PCBs are designed to ensure the LED matrix applications have a long lifespan of up to 50,000 hours.

They are also designed to enable easy control of color and brightness of the displays.

They are used in displaying information and animated images, for example in business premises. There are different types of LED matrix, including 8*8 dot matrix, 128*16 dot matrix, among others.

LED matrix displays have many applications, including in television sets, computer monitors, medical monitors and head-mounted displays.

6.COB LED PCB Board

Chip on board (COB) is obtained when many bare diodes come into direct contact with a metal core PCB (MCPCB) substrate. This results in an array of diodes.

COB MCPCBs have high thermal conductivity and perfect heat dissipation. They are also highly reliable, with good heat dispatch and limited number of solder joints.

COB MCPCBs also present simple high power LED assembly and reduced space consumption. They are also relatively cheap.

COB MCPCBs have a wide range of applications. They are used in backlight for LED TVs, street and parking lot lighting, Automotive, agriculture (horticulture) lighting, and high power LEDs.

7.Other PCB Design for LED Light Systems

There are several lighting applications for LED PCBs, and there are different design characteristics for each of them. An example is the LED lighting PCBs used in the telecommunication sector.

This LED design relies heavily on low weight and noise resistance. It is also designed to last long because of aluminum’s durability.

LED equipment used in telecommunications produce so much heat. This is where the excellent heat dissipation characteristic of aluminum base material comes in handy.

These PCBs are used in high-frequency equipment like filter circuits.

How to Choose LED PCB Board Material

LED Printed circuit board

Factors Determining Type of PCB Material

·Fire Retardant

The material used should be fire resistant. This material should be able to either slow or stop the spread of fire in case it breaks out.

This characteristic is brought about by reactions between chemicals. Such reactions make the fuels less flammable.

They also effectively prolong the combustion period for the fuels. This prevents the LED board from burning.

·Dielectric Constant

Another consideration should be the substance’s electrical energy storage capabilities.

Dielectric constant should also be able to tell you the strength of the electrical force. This is an important consideration to make.

Normally, all LED boards are designed for electrical appliances. Check on the electrical energy storage capabilities of the material.

·Loss Factor

The substrate material used also has dielectric loss as one of its functions. Dissipation factor is used to measure the difference in loss performance among different materials.

In instances that the dissipation factor is lower, it implies that the laminate has a low dielectric loss.

Ensure that the laminate material used in the substrate has a lower dielectric loss.

·Tensile Strength

This is a material’s ability to break when placed under tension. In simpler terms, it refers to the maximum sustainable load which the material used can hold.

This means that even in instances of stretching, no fracture will be reported.

Ensure that your LED PCB material has the required tensile strength.

·Glass Transition Temperature (Tg)

This is a very important property that should be considered in instances that polymers are considered for end-use.

At glass transition temperatures, the physical properties of plastics are transformed into crystalline or even glassy state.

When the same materials are placed above the glass transition temperature, they become rubbery.

In the LED PCB design, ensure you are using a material that offers a high enough Tg. This will help to ensure the board performs even in some otherwise harsh conditions (temperatures).

·Z-axis Expansion Coefficient

This refers to the changes in the size of the object when exposed to different temperatures. It can also be defined as thermal expansion.

At constant pressure, the coefficient of thermal expansion is measured.

In the recent past, several methods for measuring thermal expansion have been developed. They include volumetric, area and even linear.

LED PCB Board Material

You can consider the following materials for your LED PCB design:

i.CEM 1 and CEM 3

CEM-1 Composite material is usually made up of three components. These include woven glass fabric bound together with paper core. These two are then combined with epoxy resin.

This material is commonly used in the printed circuit board industry.  It is easy to punch and usually has exceptional electrical properties.

CEM 1 material for PCB

CEM also has greater flexural strength compared to paper-based grades. This results in outstanding mechanical and even electrical properties.

CEM-3 bears striking similarities with FR4. As an alternative to woven glass fabric, flies is usually used.

This material has a milky white color. Its surface is also very smooth.

Because of these, it has gained popularity in the Asian market. It is also preferred for its advantage of being a flame retardant.

They are usually used in the manufacture of both double-sided and multilayered LED PCBs.

CEM-3 is arguably a new PCB substrate material whose development is dependent on FR4’s technology. This explains why it has been used to replace FR-4 in the recent past.

ii.FR4

FR-4s performance in all the desired aspects of a good substrate makes it a preferred choice for most manufacturers.

FR4 Material for PCB

It has an excellent strength-to-weight ratio.

This material is also resistant to flame, making it very dependable in instances of fluctuating temperatures. In such cases, its physical properties remain unperturbed.

This also extends to mechanical and electrical capabilities.

High-performance FR-4 laminate is more reliable owing to its increased glass transition temperature.

It is also more accommodative for circuits of high frequency owing to its low dielectric properties.

These qualities are desirable in the manufacture of LED PCB designs.

iii.Aluminum

This refers to aluminum metal core PCB. In this PCB, the base material for the PCB is metal. This is as opposed to the normal FR4 or CEM-1 or CEM-3.

Aluminum PCB

As opposed to the other materials, aluminum metal core PCB has exceptional heat dissipation capabilities.

Thus, they can dissipate heat away from the components. This usually attained by the use of thermally conductive dielectric layer.

It is this thermal conductivity that makes aluminum the most widely used material for LED PCBs.

iv.Copper Alloy

These are metal alloys which are principally composed of copper. This gives them very high resistance against corrosion.

Heavy copper PCB

There are also traditional types used. Such include bronze, which has to be combined with tin as a very significant addition.

The other alternative is brass in which zinc is a significant addition.

LED PCB Design Guidelines

1.Do Not Place Vias at the End of SMT Pads

Vias, more so when they are not masked over, must not be placed so close to the SMT pads. This can usually lead to poor solder joints because the vias provide a means for the solder to move from the pads.

Always keep a distance of at least 0.025” between the via’s edge to that of the SMT pad. It is also prudent to mask over the via pad

2.Avoid Routing Wide Traces into Narrow SMT Pads

The surface mount pads should be wider than the traces that terminate thereat.

If the trace exceeds the pads, the available area for the surface finish will depend on the solder mask aperture.

This will, in turn, lead to inadequate paste cover. It can also reduce the heat sink effect. The surface finish area should instead be determined by the pad area.

3.Designing Sides of SMT Pads

Avoid routing traces along the sides of the SMT pads. They should instead be routed to the pads midway along the pad edge.

Allowing a gap between the pad and the trace can trap etchant, which will eat away the trace at the end of the rinse cycle.

Such connections are, in most cases, going to fail due to thermal shock at the assembly stage. It can sometimes lead to oversized pads. You may need to check and correct the routings in these connections.

4.Do Not Route Any Circuit Trace at an Acute Angle

Routing at angles less than 900 can lead to problems that can later cause failure. This is because acute angles usually pose the threat of concentrating stress.

You can solve this by rerouting such corners in a way that you end up with angles greater than 900.

5. Avoid Placing Components Too Close to the Board’s Outline

Placing components too close to the edge of the board may be too dangerous. Such components may suffer damage during de-penalization.SMT components should be kept at least 100” from the edge of the board.

When designing the PCB, you should include a reference tab location. This will help you to know whether a component is safely positioned, or if you need to adjust its position.

6.Avoid Exporting English Unit Gerber files at 2:3 Decimal

The 2:3 which was commonly used to move files on flexible disks is not appropriate for denser designs.

Normally, the problem is that such can truncate significant digits off the intended location. It also interferes with arc endpoints.

7.Consistency in Solder Mask Openings

When setting your pad stack definitions, ensure that you use similar over-sizing for the components. This will help to limit flaws with the design rule, hence making the PCB manufacturing process less troublesome.

8.Use Direct Connects for Vias

Just handling the circuit issues alone is not enough. You also have to ensure that the holes are well functioning.

The vias do not need location dots or thermal pads. Including this, especially for congested vias, may lead to an open circuit condition.

It is best if you avoid them as they are are not necessary during production, and can, in fact, lead to problems.

9.Thermal Pad Sizing

It is also important to ensure correct sizing of the component hole thermal pad.

Congested pads on component holes can also lead to an open. Therefore the inner diameter should resonate with that of the outer layer pads.

10.On the Through Holes

The space between a PTH and a trace should be at least 0.006”, especially for multilayer PCBs.

For multilayer PCBs, there are many factors that influence the accuracy of this space. They include:

• Material movement
• Drill run out
• Multiple pinning setup, and
• Artwork scaling

Controlling Thermal Issues in LED PCB Design

There are many strategies and approaches used to solve heat dissipation issues from LED PCBs.

·Use Heat Sinks on LED PCB Design

Heat sinks have been the most commonly used strategy, where a piece of metal which has a large surface area is used. This gives space for heat to flow out of the PCB into the air.

The heat sinks are also used to connect the source of the heat to a large area of conductive surface.

Heat sink on PCB

·Laminate Technology for Thermal Control

Laminate technology is also used as a heat dissipation measure in LED PCBs today. Here, you depend on a large copper coin, which serves as a heat dump.

The coin thus deposits and dissipates the resultant thermal energy. This makes the coin a thermal heat sink for LED PCBs.

These coins can also be replaced with local heat sinks, using IMS materials.

These thermally conductive IMs offer an array of solutions for a number of components on the LED PCB. They can effectively dissipate heat in thermally conductive laminates.

They also dissipate heat from glass reinforced prepregs, which happen to be thermally conductive.

Other areas where this is used include on thermally conductive dielectrics and isolated metal substrate materials.

When you compare coining and local heat sinks, you will realize that they are very specific solutions. However, IMS is never a focused solution hence you need a well thought out strategy. These considerations have to be made when designing your LED PCB.

For the purposes of effective selection of a heat dissipation strategy, you will have to involve the technical team. They will guide you in effectively selecting the best material for your specific need.

At the time of calculating the thermal reactions, you should seek to understand thermal configuration. This is as opposed to focusing on thermal resistance and conductivity alone.

Check also on the thermal impedance, which provides a more consistent and accurate measurement.

Another factor to consider is the environment within which the LED PCB will operate. Look at the air circulation.

Another environmental factor that you should consider is the surrounding products. You will have to assess the impact that this will have on thermal management.

If the LED PCB is dissipating heat in a way that affects the other products, you need to change the dissipation method.

You should also establish whether these other products will have an effect on the thermal performance of the LED PCB design.

It is also important to establish the mechanical properties and mechanical stresses that will be caused by material selection.

The manufacturing process will have to put these factors into consideration. Both the fabricator and the assembler will have to design their input into the best resolution.

At the end of it all, you must have arrived at, and used the best heat dissipation strategy.

Led PCB Defects and How to Overcome Them

In dealing with LED PCB, you may encounter some defects. Some of the problems are unique to LED PCBs, while others may cut across other printed circuit boards as well.

They need to be effectively and thoroughly addressed, to ensure that the efficiency of your PCB is not compromised.

Let me take you through some of these, and how you can overcome them.

LED PCB design

·Circuit Scratch

Densely packed pads usually cause recessive defects of a scratched circuit. A scratched circuit leads to the exposure of copper, which definitely is a deadly matter.

To overcome this, you should apply a lot of copper foil to reduce the open as well as short circuit scrap.

Exposed copper defect often goes unnoticed, until after the SMT procedure.

Making the line pitch to shrink by reducing the line and pad pitch is one way of dealing with circuit scratch. It causes an improvement that can help overcome the problem.

·Solder Mask Oil Peeling

When using black solder mask for your LED PCB design, you’ll require a lot of exposure energy. Similarly, you may decide to use solder mask oil that is a bit thicker than usual.

This makes it difficult for the oil at the bottom layer to gain complete exposure, leading to solder mask oil peeling.

To tackle this oil peeling issue, consider the application of secondary exposure energy. You should note that by so doing, you’ll also need to look into the consignment capacity of the solder mask.

·Bad Board Outline

This effect is common in the installation of LED holes in boards of smaller sizes that do not have margins.

Bulge of board angle of the board outline may occur due to loose marking-up screws. Board displacement can also occur in the process.

You can settle on margins that are suitable to assist the marking up process as a way of overcoming this defect.

·Solder Mask Oil Color Inconformity

Color inconformity is a common defect associated with printed circuit boards.

The LED side in an LED PCB displays color inconformity, which can’t be quantified to determine the right standards.

This is because there are currently no standards that are publicly accepted as being the right ones.

Oil color conformity is influenced by several factors.

To achieve oil color conformity, the manufacturing standards followed are stricter, compared to other circuit boards of ordinary nature.

Exploration of manufacturing methods and parameters of control that are suitable is the best way to achieve this.

This can only be made possible after years of experience in fabrication and the use of more advanced technologies.

·Board Angle Defects

When handling circuit boards with a thickness that is relatively high, it’s important to be aware of the fragility of the side angles.

Board angle defects tend to occur during the transportation of such boards.

To ensure you avoid such defects, handle the LED circuit board’s delicate side angles with utmost care.

Also, you should make the base plates somehow larger in size compared to the ordinary single-margin boards. An additional base plate also serves as a very critical protection measure in solving this problem.

·Warpage

LED circuit board warpage is normally attributed to the asymmetrical stress applied to it. This stress comes about as a result of so many high-density pads on the LED side of the board.

Another contributing factor is the large copper blocks arranged on the driver side of the board.

This defect can be solved by controlling the warpage under 0.5%, which helps to ensure that it remains reasonably flat.

·Pad Outline

Because of the complexity of matrix pad arrangement, errors of omission are often bound to occur during an inspection.

This is because of the visual strain and fatigue that this type of arrangement causes.

Prolonged time taken during inspection and a pass rate that is very low are the resultant problems associated with such.

In order to overcome pad outline problems, procedural control is vital. You should therefore make efforts to reduce the omission ratio by defining favorable manufacturing procedures.

As you know, if the visual inspector experiences visual fatigue, performance will obviously be poor.

·Degrading Functions

As you may have noticed this far, LED PCBs are technically different from other Printed Circuit Boards.

LED PCB is characterized by highly dense pads and solder mask in black. During the error analysis of Printed Circuit Boards Assembly, these features come about as obstacles.

Making accurate error analysis becomes very difficult, as no clear malfunctioning LED can be sighted.

In case of a failure in the board’s function, PCBA simply indicates, without really specifying the pad that has failed.

The PCBA demonstrates this defect as a problem of failure of the entire row of LEDs.

If you happen to face such a challenge, you may need to make an effort to determine the exact problem.

Identifying the specific LED facing a hitch could involve demolition of the components and removal of solder mask oil too.

Sourcing for LED Circuit Board Components

Before you start the sourcing components for PCB, it is important to prepare a bill of materials (BOM).

The BOM lists all the needed components to be used in the manufacturing process, in detail.

Here are some fundamental aspects you can consider:

Using BOM Templates

Most outsourcing companies provide BOM templates.

You might consider using this for your outsourcing, and fill in all the components required for your LED PCB. You will then depend on the BOM in determining the contents of your order.

BOM

In most instances, manufacturers outsource the function of buying these components. It means you entrust the purchasing responsibility on an outsourcing company.

These companies will supply you with excellent working units, giving you room to focus on other activities involved in the process. This guarantees you effective LED PCB components, translating into improved applications.

People have different points of reasoning when it comes to outsourcing the services of these intermediaries. However, the best LED PCB components outsourcing company is that which works best for you.

But it is no difficult task knowing who can provide the most desirable components to complete your manufacturing process.

Capacity for a LED PCB Component Manufacturer

One of the main qualities to look out for is the manufacturing capability. Is the manufacturer able to manufacture the volumes you require?

Secondly, it is imperative to assess whether the manufacturer has skilled labor. Assess and compare the cost of production, the turnaround time and even communication.

LED PCB components

These factors will help you ensure that you pick on the best manufacturer. Outsourcing from such a company will hence save you the hustle of manufacturing on your own.

Put in Place a Stable LED PCB Component Procurement Plan

There is also the need for a stable procurement plan. This is dependent on the ability of the company to identify the best manufacturer.

When there is modification done to the procurement plan, then this will impact on the products. This will affect the quality of the product, the time used in the production process and even the overall cost.

It is therefore advisable to source for your components from one manufacturer.

Besides, it is also important to see to it that the company is capable of meeting most of your needs.

In a way, sticking to one manufacturer when sourcing for LED PCB components can also be cheap. It allows you to negotiate for discounts owing to the volumes and frequency of purchase.

This still reflects on lower production cost which is to the benefit of your company, and is beneficial for long term progress.

For you to be able to conduct an evaluation on a component manufacturer effectively, you must establish their credibility.

Reliability is Key in LED PCB Component Sourcing

Reliability is also another component of effectiveness that you will have to assess. Make sure that the manufacturer is not a scammer.

In the PCB industry, there are companies which purport to manufacture components when in real sense they don’t.

They simply buy custom made components from manufacturers and resell them. This will mean that in case of defects, they will not be able to replace the components.

This kind of arrangement is also time-consuming and cost-intensive.

If possible, you can personally visit the manufacturer and establish whether they really manufacture the components you are interested in.

You also have the option of assessing the components by using them in the prototype.

LED PCB Design Software

Before you can design your LED PCB, it is important to choose the best design software. There are many software for PCB design, but you have to choose one that will give you the best design.

In this guide, we will discuss three different options you can choose from.

Interface of PCB design software

First though, let us look at some important considerations when choosing LED PCB design software. They include:

• Your Level of design
• The number of pages you need
• How much you are willing to spend
• Whether you require auto-routing
• The type of computer system that you are using
• The amount of space you have
• Whether you will be working online
• Whether you are buying components or you have a library to choose from

Having looked at these factors, we can now explore the different software that you can use to design your LED PCB. Among the many options available, the top 5 are:

·Eagle PCB Designs Software

Eagle is an acronym for Easily Applicable Graphical Layout Editor, a PCB design software common amongst professionals.

There is a free version you can opt for, or a more advanced version for $15 per month, which is quite affordable.

Some of its technical features include Modular schematic editor, Schematic rule check, Auto-router, Copper cladding and Design check ruling.

It also offers Online Annotation Function, both positive and negative as well as Script file for the execution of the batch command.

Apart from the simple interface, the language programs are flexible and user-friendly. If you need to export Gerber files to use on other boards, you can do so effortlessly on Eagle

·Kicad PCB Design Software

This software is very user-friendly, and you can use it to design your LED PCB. Kicad enables you to create a schematic easily, then convert it into the design for your PCB.

Using Kicad, you are also able to generate Gerber files, BOM, artwork and more.

Kicad usually has five parts:

1. Kicad
2. Eeschema

iii.   Pcbnew

1. Gerbview
2. Bitmap2component

It works on Microsoft Windows, Linux and Mac OS.

Kicad provides several component libraries, and also allows you to add your custom components.

This software is very affordable. It also allows you to work flexibly as you design your PCB. The other plus for Kicad is that it has a simple and straightforward installation procedure.

· Diptrace PCB Designs Software

This software is very convenient for beginners or designers who are pressed for time.

You can use it to quickly create schematics before converting to other formats like PCB. The simplicity and flexibility of Diptrace is what makes it very popular.

https://youtu.be/_yASVrjQZs0

Some of its features include:

• High-speed routing that is based on shapes
• Advanced and extensive capabilities for importing and exporting data
• 3D modeling
• Offers hierarchical circuits that are multi-level and multi-sheet
• Virtual high-speed signals for verifying accuracy of complicated projects
• Real-time DRC for correcting errors and improving project quality

·Altium PCB Design Software

You can use Altium to create multiple PCB designs for different applications. It is very famous among design engineers.

However, you need to have the Windows Operating System to be able to run it.

Some of its unique features include:

• 3D visualization features of high quality
• Settings that are easy to configure
• Many shortcuts for easy and efficient designing
• Offline operation, and is usable even in the absence of a license
• Library generator for the importation of data
• Advanced filtering features

·Pulsonix PCB Design Software

The professional package of Pulsonix yields marvelous results in PCB design.

It comes with an optional auto-router and the basic version with 1000 pins costs $1750. Though it’s more expensive, Pulsonix allows you to make your designs faster than any other software.

It has both PCB layout and schematic entry in one program. The Electrical Rule Check makes designing more accurate as you can use it to check on any anomalies present.

Types of LED Printed Circuit Boards

Some of the most common types of LED circuit board include the following:

Flexible LED PCB

This type of LED Printed Circuit Board is highly flexible.

Ceramic fillers are used alongside polymide resins, resulting in perfect insulation as well as the flexibility of the board. Aluminum thermal conductivity is not compromised at all in the process.

Flexible LED PCB

Flex LED PCBs are used in applications such as under the counter LED lights. This is mainly because it is easy to install in such “hidden” places, as opposed to the rigid LED PCB.

Rigid LED PCB

Rigid LED PCBs are LED printed circuit boards that are made stiff and compact. As opposed to the flexible LED PCBs, they cannot be bent or folded.

Rigid LED PCB

They are the most common type of LED PCBs, and are used in most hole and commercial applications.

Hybrid LED PCB

Just like the name suggests, this board is not purely made of Aluminum, which is the main material for LED PCB.

Rigid flex PCB

The material is obtained by merging a non-thermal material with aluminum. The non-thermal with which aluminum is merged is usually FR4.

The resulting material is known as hybrid aluminum because it brings together the strengths of both materials into one material.

Whereas aluminum ensures superb thermal conductivity, FR4 gives the material perfect rigidity. It is, therefore, used to reinforce the board’s rigidity without compromising the thermal conductivity of Aluminum.

Single Layer LED PCB

As the name suggests, these are LED PCBs with one layer of the base material, usually aluminum. As such, they can only have a limited number of components mounted on their surface.

They therefore present lower performance capacities than the multilayer LED PCBs. This makes them ideal only for lighter applications.

Single layer PCB

Multi-layer LED PCB

Multi-layer LED PCB is a complex type of PCB with multiple layers of aluminum, which ensures perfect thermal conductivity.

Having multiple layers of aluminum also ensures perfect heat transfer.

Figure 18 Multi layer PCB

Having multiple layers always comes with the advantage of bringing a highly functional PCB into a small board. In LED PCBs, these boards have present high efficiency and long life.

Led PCB Manufacturing Process

LED printed circuit board design

Step 1: LED PCB Design and Layout

The process of manufacturing your LED PCB begins with developing a design for the PCB. Let us look at how you can design your LED PCB using Kicad software.

• This step starts by downloading the Kicad Tutorial: If you already have the Kicad software in your computer then you will only need to update it. Otherwise, this is the first step towards designing your LED PCB. Be sure to get the software’s latest version.
• After installing the program, you must create a navigation window to help in opening other programs like PCB layout and schematic capture.
• Set Up the Project: You will need to unzip some files in your directory after downloading the Kicad design. These files include: Pro, CMP, Kicad PCB layout and Sch. These files share on the Kicad design.
• When you are using Kicad, you must define the footprint which will go with each of the components.
• Set Up the Component Library: Start by double-clicking on the component library.

Note that a schematic that loads while displaying a question mark means that the Kicad is not linked to the devices that contain the schematic. You will need to link your components to the libraries.

1. Add Components to Your Schematic: Click on add, which will open the components window, allowing you to select a component from the long list available.

Next, choose the device, and click Enter. Now place it in the schematic that follows.

After you have successfully placed it, click Esc to move from the placement mode back to the normal pointer. Now copy the component and place it at the correct location.

• Wire the Components: With the pointer over the bubbles, press W to wire the components.
• Finally, auto-annotate your schematic components by clicking the button for annotation. For settings, choose “default”, then click to confirm. Now verify the annotation, and the components will be added.

Step 2: LED PCB Fabrication Process

As we already mentioned, aluminum is the most commonly used material for LED PCBs. The process of fabricating this aluminum PCB usually has some slight difference compared to the other PCBs.

Aluminum PCB fabrication takes place in the following steps.

i.Cut Lamination

This is the cutting of the large incoming sheets of material into the required smaller sizes for production. The process involves picking, then cutting the sheets, just as the name suggests.

During cut lamination, you must be very keen on the size of the first piece to ensure it is perfect. Also, you must pay close attention to aluminum copper scrapping, and watch out for blisters.

ii.Drilling

After cut lamination, you now need to drill holes on the holes for the through-hole components.

When drilling, ensure that the number and sizes of the holes are in accordance with the design. Also, ensure the sheet does not scratch as you drill.

The other important precaution is to check the burr of the aluminum surface. Check also whether there is hole deviation.

To achieve the best results, always inspect and replace the drill tool in time to ensure it is working perfectly.

iii.Dry/Wet Film Imaging

Here, you will grind the plate, then expose the film and finally develop it. the reason for doing this is to highlight the parts that will be needed to make the circuit on the sheet.

Ensure you always check for open circuits after development. You should also watch out for any deviations in the alignment of the development. This can potentially prevent the generation of dry film.

You should also watch out for bad circuits. These can occur especially if there is a surface scratch.

Avoid air residue during exposure. If this occurs, it can lead to poor exposure. Upon completing the exposure, allow about fifteen minutes before developing.

iv.Acid/Alkaline Etching

Basically, the idea here is to retain the required circuit portion while removing any excess. You will therefore etch, strip, dry, and finally inspect the board.

In acid/alkaline etching, you must always stay keen on the circuit width and space. Also, do not allow oxidation of the copper surface, or even scratching.

v.Solder mask, Silk Screen Process

You apply solder mask to protect the parts of the board that do not need to solder, thus preventing short-circuiting.

In this process, ensure you thoroughly check the board and remove any foreign materials. Also make sure the stencil you are using is clean.

When you are through with silk screening, procure for at least thirty minutes to ensure the circuit has no bubbles. Cool the procuring plate to ensure it does not stick to the film.

The whole solder mask and silk-screening process can therefore be summarized as: silk-screening, procuring, exposure, development and legend.

vi.V-Cut, Rout Out

This step is basically meant to separate the individual circuit units to enable easy packaging and transportation. Routing also helps to remove the excess parts of the board.

When doing the V-cut, be keen to ensure that the depth of the “V” is appropriate. Check also for any defects along the edges. Also watch out for route deviations.

Again, just like we said of the drill tool, here also you need to keep checking the routing tool. Service or replace accordingly to ensure they are working perfectly.

As you remove the burr, ensure you don’t scratch the board.

vii.Electronic Test, OSP

This step is useful in checking whether the circuit is working properly. You also get to confirm that the circuit is able to withstand the prescribed voltage environment. Finally, it is also to make sure that the soldering of the circuit is perfect.

You should be sure to properly distinguish between good products and those with defects. Ensure there is no damage to the circuit whatsoever.

viii.Packaging and Shipping

This is where you do the final overall quality check on the board to confirm that it is of good quality. It involves taking a few samples from the completed boards, and verifying their quality.

Using visual inspection, separate outboards whose appearance does not show perfectness.

Finally, the boards that pass this check are packaged and shipped to the respective buyers. When packaging, be keen not to mix good and bad boards or package wrong boards for a customer.

Ensure the boards are stored according to the industry standards for storing aluminum substrates.

Step 3: LED Circuit Board Assembly Process

LED PCB assembly, just like the fabrication process, needs some special attention to produce perfect results. If carelessly done, the result will be boards with poor solder joints and misalignment.

This is especially because of the sensitivity of the metallic base material.

LED PCB assembly

Different LED PCBs will need different considerations during the assembly process. It is therefore important consider the purpose for which the board is required.

The process of LED PCB assembly takes the following steps:

viii.Preparation of the Materials

Thoroughly check the bare boards, the components, PCB stencil and solder paste.

Also check the tools to ensure that they are all in perfect condition. Remember any slight deviation in PCB assembly can cause total malfunction of the final product. Therefore ensure the soldering iron, wire stripper, pliers, and tin, among others, are perfect and ready.

You must also put have your BOM list and Gerber file on the table. You will continuously refer to them during the assembly process.

 i.Bare Board Baking

You must ensure that the bare board is dry before you start assembling components onto it.

ii.Solder Paste Application

The solder paste printing machine applies solder paste onto the required places on the board. You must thoroughly inspect to ensure that the soldering is perfect.

iii.Component Mounting

The pick and place machine picks and attaches SMT components to the PCB with a lot of accuracy. However, you must still manually inspect the board before reflow to ensure that the placement is accurate.

iv.Reflow Soldering

Run your LED printed circuit board into the reflow machine. The machine solders the SMT components and cools the joints to strengthen them.

After soldering, use the AOI instrument to check for any problems with the soldering.

v.Through-hole Component Insertion

Insert the leads of the through-hole components into the through holes on the board. Ensure each component is inserted at its right position.

vi.Wave Soldering

Now put your LED PCB in the wave soldering machine. The machine uses spray welding flux, preheating, soldering and finally cools the joints to strengthen them.

 vii.Final Inspection and Packaging

Once you are through with assembling all the components, you will need to first clean the board. Next, run the finished board through the final quality check to rule out all quality issues.

All the PCBs that have passed the final tests are now ready for packing and shipment.

How to Make Custom LED PCB Designs

From our discussion on the manufacturing process above, you now know the entire process of making LED PCBs.

However, you may want to make custom LED PCB Designs, thus calling for a few changes in the manufacturing process.

All you need is to be familiar with the design software of your choice.

LED PCB

Now follow the correct procedure in designing your LED PCB.

The procedure is usually the same for most of the common design software, except for a few differences. You will therefore follow these steps:

• Download and install the softwarwe
• Set Up the Project:
• Set Up the Component Library:
• Add Components to Your Schematic:
• Wire the Components: With the pointer over the bubbles, press W to wire the components.
• Annotate your schematic components

What to Look for in LED PCB Design Services Provider

Now that you know all about LED PCB, the next question that is probably bothering you is how to find the best designer for your product.

Here are some tips on what to look for before hiring a service provider to handle your LED PCB Design.

Experience – Would want your product to be a control experiment for a practicing designer? Definitely not!

Consider a service provider who is established and has massive experience in the field, especially with regards to LED PCB Design.

Lead time – The faster the lead time, the better for you since you’d be able to have your product sooner.

Specialization – Hiring a service provider handling all types of PCBs is acceptable, especially if you need designs of other PCBs too. Otherwise, it’s better to go for one specializing in LED PCB design if possible, for more precision and high quality.

Expertise – If you need your product designed using specific software, it’s best to ensure your designer is well conversant with it.

Customer support – A service provider with reliable customer support in place and useful information for the customer’s use can be trusted.

Conclusion

LED PCBs impact our day-to-day lives in many ways. After going through this guide, you are now all set to make your own LED PCB design.

You have also gained an elaborate understanding of the fabrication and assembly of these PCBs.

Out of our discussion, you are able to choose the best option of LED PCB for your application.

In general, this guide leaves you perfectly fit to handle every matter concerning LED PCB.