What is a Flexible Circuit?
A flexible circuit is a printed circuit board manufactured that is naturally flexible.
Flex circuits are typically manufactured use a polyimide (Kapton) material and it’s one to multiple layers of copper.
Popular suppliers of flexible materials are DuPont and Panasonic.
What are the differences between Flex and Rigid boards?
Rigid boards are typically made out of FR4 (glass-epoxy compounds) while flexible circuits are made from polyimide.
There are cases when rigid boards are built with polyimide, but it isn’t as common.
What are benefits of Flex PCBs?
There are many benefits to make a flexible printed circuit board in your application:
Lightweight: Flex circuit’s polyimide material is more lighting than FR4 material.
Thin: A 2-layer flex can range thickness between 4.4 and 10 mils.
Flexible: This is obvious but with the ability to make it bends, you have more freedom space to decrease the overall mechanical footprint.
For more than 10 years of experience in the industry, Venture is one of the
leading and trusted manufacturer of PCB prototypes.
Venture offers high-quality and flexible PCB prototypes with competitive prices. We are providing the best flexible PCB prototypes for our customers.
We aim to provide our customers with the best flexible PCB prototypes so that the customer’s needs will be satisfied. We strived to achieve our aim.
If you are looking for a reliable and experienced manufacturer of flexible PCB prototypes, Venture is the right place for you.
Your Leading Flex PCB Prototype Stack-up Supplier in China
In China, Venture is one of the most experienced manufacturers of flexible PCB prototypes.
Flexible PCB is also variously referred to as flex print, flexible printed circuit boards, flex circuits, and flexi-circuits, and flexible circuits. Flexible PCB is an electronic component that is developed to allow electronic properties to become lighter and smaller.
Flexible PCBs consist of a thin insulating polymer film with conductive circuit patterns. To protect the conductor circuits, they are typically supplied with a thin polymer coating.
Flexible PCB is used to reduce weight and space, meet dynamic flexing requirements, flexing for easier installation and service, impedance control, increase reliability and repeatability, thermal management, improve aesthetics, eliminate connectors, provide uniform electrical characteristics for high-speed circuitry, and to reduce assembly cost.
Venture manufactures flexible PCB prototypes that have strong heat-resistance and excellent working efficiency so that it is widely used as a core component of all electronic properties such as mobile phones, computers and peripheral equipment, cameras, camcorders, satellite equipment, printers, DVD, video and audio units, military equipment, TFT LCD, medical instruments, and etc.
For more questions, please contact us.
Our goal is to prioritize our customers and make sure that all of their questions are answered properly.
Flex PCB Prototype: The Ultimate FAQ Guide
Before starting any flex PCB prototype, read this guide.
It has all information you need to know about PCB prototypes.
So, keep reading to learn more.
- What is a Flex PCB Prototype?
- Which Materials are used for Flex PCB Prototype Design and Fabrication?
- How do you Design a Flex PCB Prototype?
- How do you Fabricate a Flex PCB Prototype?
- What are the Specifications of a Flex PCB Prototype?
- Which Types of Flex PCB Prototypes are there?
- What are the Advantages of Flex PCB Prototype?
- What are the Disadvantages of Flex PCB Prototype?
- What Determines the Cost of a Flex PCB Prototype?
- What are the Design tips for flex PCB Prototype?
- What is your Turnaround Time for Flex PCB Prototype Designs and Fabrication?
- What are the Advantages of Flexible PCB Prototype over Conventional Wiring?
- What are the Disadvantages of Flex PCB Prototype over Conventional Wiring?
- How does Flex PCB Prototype compare to Rigid Flex PCB Prototype?
- What are the Considerations when Choosing Flex PCB Prototype Manufacturer?
- Is Flex PCB Prototype with Stiffeners same as Rigid-Flex PCB Prototype?
What is a Flex PCB Prototype?
Flex PCB Prototypes are flexible circuit boards manufactured for purposes of comparison against other parameters awaiting mass production.
The production of a Flex PCB Prototype can tell how valuable and usable the end product will be.
They can then decide whether alterations and modifications will be necessary in compliance with the set out standards and specifications.
Flex PCB Prototype
Which Materials are used for Flex PCB Prototype Design and Fabrication?
The main components of a Flexible PCB Prototype are as follows
Dielectric Substrate Film
The film is used as the base material for the Flex PCB Prototype. The material commonly used is polyimide [PI].
This is because of its characteristic high resistance to temperature and traction.
They allow for the free flow of electrical current. The most commonly use is copper while others include silver ink, aluminum, carbon etc.
They are usually made of copper. They represent the circuits traces.
The finish can be made with cover coat or coverlay. They are meant to prevent oxidation on the surface.
The application of the circuit will determine the final finish. Finishes commonly used include immersion in gold or nickel, solder, silver, carbon, tin etc.
Adhesive Material (Epoxy Resin or Polyethylene)
Its purpose is to bind the various components of the circuit together.
They are selected according to thickness of the conductor and the customer needs.
Some commonly used adhesives include acrylic, Pressure Sensitive Adhesives (PSAs) and epoxy. Circuits can also be built adhesive less.
The insulators serve the purpose of separating electrical conductors but don’t conduct the current themselves. They can also be used as support.
Some common insulators in use include polyethylene terephthalate, polyimide, solder mask, polyester and polyethylene naphthalene.
How do you Design a Flex PCB Prototype?
This process involves the creation of a Flex PCB based on a PCB design. The prototyping process involves many designs unlike the production process.
Reference cannot be made by the board fabricators for a suitable solution from past designs. This is because a new Flex PCB Prototype is specific to the intended system.
This results in the development of a variety of designs before the right combination of electrical and mechanical properties is arrived at.
The following are needed for design and layout of a Flex PCB Prototype;
- DXF structure drawing: this is a 2D drawing that is in AutoCAD format and can be used to build board size and position the device.
- Schematics (they must have a .DSN and .SCH suffixes)
- Specifications of the component: this has to be with the devices diagram size for the establishment and also a one-to-one physical corresponding package.
- Special requirements
Depending on production specifications, the Flex PCB Prototyping design generally has the following steps involved;
Initial Design Creation
Based on a client’s requirements and specifications, an initial design is created by a team of engineers. Clients detailed system information and end goal go a long way in easing the creation of a unique initial design that meets their standards.
Once an initial design is created by the team, it is sent for review to the PCB fabricator.
The aim of review is to determine every possible design failure points which includes manufacturing process failures as well as end application failures.
Client Follow Up
The team brings back the design to the client once it has undergone the review process.
It is at this point that the client’s concerns and questions about the design are addressed and alterations and additional elements looked into.
How do you Fabricate a Flex PCB Prototype?
The manufacturing process of the common double-side and the Multilayer Flex PCB Prototypes is as follows;
Flex PCB Prototype Fabrication
Materials Preparation (Blanking)
This procedure mainly includes cladding layer, flexible copper clad laminate and reinforcing plate.
For lamination, the main auxiliary materials used are conformal material or a silicon rubber plate, separation film, coated paper or ink absorption.
The cladding layer and flexible copper clad laminate are very thin and soft and thus difficult to drill. It is therefore necessary to stack them before drilling.
This means that a dozen pieces of copper clad laminate are stacked up together like a book then drilled. Laser drilling is also a new technology in use.
The holes will become vias for installing components and connecting traces. This procedure is also done to ease the access of the soldering pads.
Desmear and Pitting
Some dirt of resin may be found on the PCB holes just after drilling. In order to ensure superiority of a plated-through hole, all the dirt in the holes has to be completely removed.
Pre-cleaning and Imaging
The board surface must be roughened and cleaned first before imaging.
It is highly advisable to use electrolytic cleaning or chemical cleaning because the flexible substrate is easy to bend and deform.
Alternatively, a manual pumice stone wash or a specialized pumice stone paint contraption can be used. A dry film is then stuck, exposed and then developed.
The dry film becomes brittle after developing due to polymerization reaction thus decreasing its decreasing its binding strength with copper.
Position of Cladding Layer
Surface treatment needs to be done after etching so as to increase the binding strength before the progression to position of cladding layer. The flex PCB Prototype after etching and the cladding layer after drilling have different gradations of moisture absorption.
This requires the materials to be oven dried for 24 hours before being laminated. The stack-up height should not exceed 25mm.
There are two types of lamination;
Lamination of Flex PCB Prototype Cladding Layer
Different flexible substrates determine the heating rate, pressure, lamination time and other laminating procedure parameters. The process parameters are as below.
- Lamination time: under full pressure, the net pressure time is 60 minutes.
- Heating rate: within 10 to 20 min, the temperature needs to reach 173°C from the indoor temperature.
- Pressure:150-300N/cm², the full pressure has to be reached within 5-8 seconds.
Gasket Material Lamination
The lamination quality of a Flex PCB Prototype is highly dependent on the choice of the gasket material.
The ultimate gasket material should have low fluidity, good formability and does not shrink on the cooling process.
Gasket materials are divided into rigid and flexible systems.
Flexible systems majorly include radiation polyethylene film or PVC film while rigid system is primarily made of glass cloth armored by silicone rubber.
The sole reason why baking is carried out is to remove the moisture in the processing.
Hot Air Solder Leveling (HASL) or Hot Melting
After drying the Flex PCB Prototype, it should immediately be carried to the hot melting or HASL to hinder it from melting.
This is the use of a seamless accurate steel die to shape a Flex PCB Prototype. This can be a mold cavity or alternatively a multi-cavity mold.
Client Follow Up
The final Flex PCB prototype design is taken to the client once it has undergone the review process.
It is at this point that the client’s concerns and questions about the design are addressed and alterations and additional elements looked into.
What are the Specifications of a Flex PCB Prototype?
Certain specifications need to be considered after a Flex PCB Prototype fabricator has been identified. They include;
- Number of designs in panel – you can have one to several designs on a single panel and they can be different.
- Layers – the number of layers vary from 1, 2, 4, 6 and 8 layers. Stack-up is also available for Flex PCB Prototype.
- Board type – this can either be a single piece or in panel.
- Size – it is the length by width of the Flex PCB Prototype measured in mm or cm.
- Quantity – one can decide the number of similar prototypes needed to be made.
- Thickness – it Is usually less than a mm and does not comprise of the thickness of the stiffener.
- Pad size (diameter) / minimum hole size – measured in mm with the option of a no drill Flex PCB Prototype.
- Solder Mask (Coverlay) – a variety of colors (yellow, white or black) can be chosen for the coverlay. There is also the alternative of the Flex PCB Prototype not coming with one
- Silkscreen – it can be either black or white with an option of not having it at all.
- Edge Connectors – the Flex PCB Prototype can either have edge connectors or fabricated without.
- Stiffener – Apart from fabrication without stiffeners, it can either be applied on top or bottom of the Flex PCB Prototype or on both sides.
- Surface Finish and its thickness – options include Immersion Gold (ENIG), Organic Solderability Preservative (OSP), Immersion Silver (Ag) and Immersion Tin.
Which Types of Flex PCB Prototypes are there?
Flex PCB Prototypes come on a variety of types and designs. The major ones include;
Single sided Flex PCB Prototype: This is the most basic PCB Prototypes. Its composition includes a single layer of metal traces placed over a dielectric layer.
Polyimide or a polymer can be used as the dielectric. For insulation and also to protect the prototype from environmental degradation, a polyimide overlay is added.
Double sided Flex PCB Prototype: this type of prototype has single dielectric layer with multiple layers on both sides. In order to make connections, metalized through holes are used to plate the two layers.
Multi-layer Flex PCB Prototype: This consists of several copper layers which are separated by dielectric layers. Through holes are used to connect the metal layers.
Rigid Flex PCB Prototype: In rigid Flex PCB prototype, its circuitry consists of multiple circuit layers. The layers are connected by pre-peg epoxy bonding film.
Rigid Flex Prototypes have a higher component density. This is because they are a combination of Flex circuits and rigid circuits.
Multilayer Flexible PCB Prototype
What are the Advantages of Flex PCB Prototype?
Some of the benefits of flex PCB prototype include:
- Components costs are reduced by replacing PCB mounted connectors.
- Assembly errors are hugely reduced because the design is deemed accurate while production is fully automated.
- The risk of bad solder joints is greatly reduced at the connector pins on the Flex PCB Prototype.
- Flex PCB Prototypes can fit well into space-constrained enclosures on actualization.
- Vibrations, constant movement and mechanical stress can be easily withstood by the flex PCB Prototype.
- It decreases the assembly time cost of the final product.
- Due to its flexibility, it gives a variety of design freedoms and options.
What are the Disadvantages of Flex PCB Prototype?
The shortcomings of flex PCB prototype are:
- Repairing a Flex PCB Prototype is usually quite difficult due to nature of the fragile plastic material.
- Flex PCB Prototypes have a much higher one-time initial set up cost for manufacturing.
- It is very hectic and difficult to repair or modify a Flex PCB Prototype when it has to be reworked
What Determines the Cost of a Flex PCB Prototype?
- The most important factor that determines the cost of a Flex PCB Prototype is the number of layers. If a single side Flex prototype is enough, then more layers would prove costly.
- The type of flex board used also plays a role in the cost. Material utilization rate is considered whether a single piece or a panel is used.
- Diversity of prices occurs based on the types of components used to fabricate a Flex PCB Prototype. An example is the use of either photosensitive green oils or ordinary thermoset oils which serve the same purpose but cost different.
- Minimum track / Spacing should be approximately 2-3 mm. This is the limit for the cost of a Flex PCB Prototype and the eventual mass production to be deemed viable.
- Two options of the gold fingers used on the Flex Prototype have varied costs. The hard gold is much more expensive than immersion gold.
- Hole sizes have a way of influencing the cost. The smaller the holes, the less expensive the Flex PCB Prototype will be.
- Fabrication technology used by different manufacturers will bring about diversity in pricing. Fabricators have different types of equipment and levels of technology.
What are the Design tips for flex PCB Prototype?
Some of the Flex PCB Prototype design guidelines include:
- The components of a Flex PCB Prototype should not be placed near the bending lines. Both vias and pads in a Flex PCB Prototype should be placed away from the bend areas.
- To increase the ruggedness of plated holes, it is advisable to apply teardrops on them.
- The pads should be made a bit bigger than the drilled hole. This is due to the fact that Flex PCB Prototype is possibly subjected to varied angles of bending.
- When routing traces, they should always run perpendicular to the bend line. In case a bus is routed on the bend area, both top and bottom traces should alternately be staggered.
You should stagger the traces rather than placing them on top of each other. This will ensure an even distribution of the mechanical stress.
- To prolong the circuit lifespan of a Flex PCB Prototype, sharp and right-angled corners should be avoided.
- When designing a Flex PCB Prototype, a solid-filled polygon plane should be strictly avoided mostly on the bended areas. To ensure the circuit remains possible, a hatched polygon can be used for the ground plane.
- The application nature of where the Flex PCB Prototype will be installed should also be noted. Factors that will determine material thickness include size of the bend radius and whether it’s a dynamic or static bend.
Generally, a Flex PCBs bend radius should not be more than 10 times its thickness
What is your Turnaround Time for Flex PCB Prototype Designs and Fabrication?
The turnaround time for a Flex PCB Prototype varies depending on several factors. This can be between a day to weeks.
Taking shortcuts to fasten turnaround time may lead to lower quality products. This can lead to failures in industries with mission-critical applications such as the military electronics and medical equipment.
The factors that will affect the turnaround time include;
Extensive Manufacturing Evaluation Process
A good Flex PCB Prototype fabricator will carefully take his time to evaluate prototypes. This ensures that the final product will perform and operate as intended.
Some of the evaluations include whether the various elements on the board are correctly communicating with each other. Moreover, it is key to ascertain that the impedance is working correctly This is in addition to confirming if the signals are arriving on the chip at the accurate time.
Challenging Design Elements
The turnaround time of a Flex PCB Prototype mostly depends on the design. Many designs integrate elements that are challenging hence increasing lead time.
For example, buried vias mostly add two to three weeks on the overall turnaround time. If the design element is to allow the PCB Prototype to bend at very tight angles, then the turnaround time will increase significantly.
Multiple Lamination Cycles
Depending on design, some Flex PCB Prototypes go at least twice through the lamination process.
For every instance the prototype goes back through the process again, a significant time will be added to the process.
A significant time is added to production depending on the number of stiffeners used.
The Flex PCB prototype has to go back through lamination with temperature and pressure by use of a no flow prepreg.
This is in addition to extra time taken to manufacture the stiffener itself.
Pressure Sensitive Adhesives
They are used to apply stiffeners to the flex PCB Prototype (fastest way to yield stiffeners).
If the PSA is in the same final outline shape and is symmetrical, much time will not be added to production.
Otherwise, delays will be created due to laser cutting and tooling.
This happens when a selective PSA not covered in the specifications is required or when prototype requires different PSAs on same Flex PCB.
A huge number of disproportionately small hole sizes or use of asymmetrical layering in the flex region adds time.
The speed of processing needs to tone way down when such types of parts are manufactured.
What are the Advantages of Flexible PCB Prototype over Conventional Wiring?
Some of the main advantages include:
Flexibility during Installation
During execution, Flex PCB Prototypes can communicate between two or more planes therefore a third dimension can work with it. This is unlike conventional wiring which is normally end-to-end.
Improved Air Flow
Due to their streamlined design, the Flex PCB Prototypes offer improved flow of cooling air through an electronic device.
Conventional wiring will have to be supplied with an external cooling fan.
Increased Heat Dissipation
Due to its compact design and extensive surface-to-volume ratio, the Flex PCB Prototype ensures a shorter thermal path.
Heat dissipation is also possible from both sides of the circuit due to the thin design.
Flexible PCB Prototype
Components are evenly spaced in conventional wiring thus reducing the surface-to-volume ratio and increasing the thermal path.
Increased System Reliability
Most failures in the conventional wiring occurred majorly at interconnection points.
The design of a Flex PCB Prototype is such that reliability of a circuit is increased by a reduction in interconnections.
Ease of Point-to-point Replacement
Maintaining a conventional wiring circuit involves a point-to-point replacement of wires.
The Flex PCB Prototype that eliminates some (if not entirely all) of those interconnections.
Reliability and Durability
In designs having moving parts, Flex PCB Prototype results in a circuit that flexes and moves up to 300 million times without fail.
The circuit can also withstand extreme heat due to the thermal stability of the polyimide.
Simplified Circuit Geometry
The electronics on a Flex PCB Prototype are surface mounted directly on the circuit resulting in a streamlined overall design.
These patterns were rigid and unachievable on a conventional wiring circuit.
Package Weight and Size Reduction
Multiple systems in a conventional wiring utilize more space and create a lot of weight.
The thinness of a Flex PCB Prototypes dielectric substrates allows for a more streamlined and light design.
What are the Disadvantages of Flex PCB Prototype over Conventional Wiring?
Some of the limitations you need to know are:
High Initial Cost
Compared to conventional wiring Prototypes, the Flex PCB Prototype has a high initial one-time cost.
Unlike conventional wiring prototypes, their design has a specific application with specific components that don’t have alternatives.
Unlike conventional wiring circuit prototypes that can easily be modified on-surface, modifying and reworking a Flex PCB Prototype is difficult.
The protective film that wraps the circuit first has to be removed, an intervention performed and the protection restored.
How does Flex PCB Prototype compare to Rigid Flex PCB Prototype?
Flex PCB Prototypes differ from Rigid Board circuits in various circuit in the following ways;
For Rigid board materials, the range of relative permittivity (Dk) is very wide while for Flexible polyimide material, the range is typically 3.4.
Flex PCB Prototypes can either have coverlay or a flexible mask whereas for rigid board prototypes, a solder mask is typically used.
The openings are laser cut or routed when a coverlay is used.
The coverlay is adhered to the flex using an adhesive (1 or 2mm thick).
Rigid Board PCB Prototypes are basically made out of Glass-epoxy compounds. Flex PCB Prototypes are made from polyimide.
We have situations where rigid board PCB prototypes are built with polyimide though it is not as common.
Whereas Rigid Board PCB Prototypes do not need stiffeners, polyimide stiffeners are used in Flex PCB Prototypes to stiffen non-flexing regions.
Pressure sensitive adhesive (PSA) is used to adhere the stiffeners to the Flex or they can be laminated.
What are the Considerations when Choosing Flex PCB Prototype Manufacturer?
Before choosing flex PCB manufacturer in China, you should focus on the following:
How Long they have Been Providing Flex PCB Prototypes to Clienteles
Basic as it may seem, this question assists in evaluating the total experience of the manufacturer.
A Flex PCB Prototype fabricator having expertise and several years of experience is better equipped to comprehend your prototype needs than a startup.
What Quality Standards they are Implementing for a Functional and Efficient Prototype
Certification compliance and standards differ across the industry.
You should be aware of the quality standards that the fabrication shop follows.
Major standards such as ISO, IPC RoHS are clear indication of trustworthy production house that follows them.
How Long the Turnaround Time will Take
Turnaround time varies based on the manufacturers capabilities.
Research should be done on various manufacturers of Flex PCB Prototypes and their turnaround time compared and a sound judgement made.
What Methods they Use to Assure Quality
It is important for a manufacturer to impose very stringent inspections while producing Flex PCB Prototypes. Choose a manufacturer who stringently performs inspections while utilizing the best techniques.
Do they Own a Well-equipped Fabrication Facility that can Mass Produce after Prototyping
There are some PCB fabricators that specifically specializing in meeting prototype demands of customers.
Lack of advanced equipment, cutting-edge technology and manpower are some of the reasons for limiting operations.
You must confirm the scope of a manufacturer.
Is Flex PCB Prototype with Stiffeners same as Rigid-Flex PCB Prototype?
They are not the same.
To make a Flex PCB prototype rigid in certain areas, Polyimide stiffeners/FR4 are applied through pressure sensitive adhesive (PSA) or by lamination.
For Flex circuits with one-sided components, the stiffeners function appropriately.
Flex PCB Prototype Stiffener
On the other hand, a rigid-flex PCB Prototype involves a combination of a flex circuit and a rigid board.
No flow prepreg is used to sandwich the flexible layers between two rigid boards.
This type of flex works efficiently in circuits where components are two-sided.
At Venture Electronics, we will help with all your flex PCB prototypes.
Contact us today for all flex PCB prototype fabrication.