Printed Circuit Board Assembly
Printed circuit board assembly is an involved process that requires careful planning and attention to detail. This is especially true for flex circuits, which have special requirements due to their flexible nature. Using the right assembly techniques can ensure that your finished product meets industry standards and performs as designed. Here are some tips to help you get started.
The first thing you need to do is make sure that your flex printed circuit board assembly is capable of supporting the components that it needs to. This includes verifying the size and placement of each component and ensuring that all the necessary connections are present. You should also trim any excess component leads that are protruding from the flex circuit. This will reduce the chance of shorting during soldering.
Once you have verified that your flex circuit is capable of supporting the components, it is time to start the assembly process. This will involve baking the flex circuit, which is necessary to remove moisture from the copper and film substrate. This can take anywhere from one to several hours, depending on the thickness of the flex circuit. Once the flex circuit has been baked, it is ready for the solder paste printing stage. Solder paste is applied to the circuit board using a stencil and a tool called a squeegee. The squeegee is used to apply the proper amount of pressure on the paste so that it spreads evenly across the stencil.
Printed Circuit Board Assembly Techniques for Flex Circuits
Next, the flex circuit must be assembled and tested. You will need to place the through-hole components at their designated locations and check that all of the necessary connections are in place. You will also need to test the flex circuits to make sure that they are able to meet your design specifications and performance criteria.
When designing a flex circuit, you should use a minimum of two layers and minimize the number of traces. You should also avoid using solid copper pours, as they can lead to excessive stress in the copper during bending. A better choice is to use a hatched copper pattern, as this will reduce the stress on the copper when the flex circuit is bent.
Finally, you should avoid creating sharp corners on the flex circuit. This can cause the flex substrate material to tear, which will result in failure of the circuit board. Instead, you should use tangential curved corners to reduce the risk of this problem.
In addition, you should design your flex circuits to be as rugged as possible. This will reduce the chances of them failing in harsh environments, such as those with constant movement and vibration. This will require the use of a stronger substrate material, such as polyimide. This material is more versatile and tougher than epoxy resins, which makes it a good choice for flex circuits. It is also resistant to high temperatures, which is important for a flex circuit that will be used in demanding applications. Moreover, it is more durable than glass and aluminum, which are commonly used for rigid circuit boards.