Rigid and flexible PCB can replace the wiring harness and connector, thereby solving the problem of loose contact and heat dissipation, thereby improving the device’s reliability. The plastic part can be bent at any angle, and the entire PCB is excellent in electrical and mechanical properties. It may be produced through a series of rigid-flex PCB manufacturing techniques. We will introduce three types of production next so that you can understand this knowledge more clearly.
Window opening method
It is a method in which rigid-flex PCB with a core board structure makes the most out of mold punching to get rid of the rigid core in a flexible construction. It is the production of rigid-flex PCB with the help of lamination.
The copper foil etching method
It is another excellent method used to produce flex-rigid PCB. Here, PCB copper foil structures for making the flexible portion of the PCB. This is an exciting process.
The positive and negative depth control method
In this process, a blind groove was created in advance on the rigid board next to the flexible board. After proper lamination, the blind grove is combined during molding using the mechanical depth control method. Then remove the rigid plate in the window position, and the flexible portion is exposed.
What is the main factor about rigid flex PCB manufacturing?
As is the case with any other PCB, the performance of rigid-flex PCB, to no small extent, is also determined by their substrate material.
Typically, a flexible dielectric film made of polyester is in the low-end products. In contrast, more advanced products like those used in the military and aerospace purposes use fluoropolymer and polyimide.
If we compare these three types of flexible materials, polyimide tops the list for having the highest dielectric constant. It can also withstand high temperatures and offers excellent mechanical and electrical properties. However, it can absorb moisture quickly and is quite expensive.
Talking about polyimide, it also performs well, but polyester offers pretty bad temperature resistance. If you want to operate the product at high frequencies, polytetrafluoroethylene offers a low dielectric constant and serves the purpose well.
In terms of adhesive films, the best materials for this purpose include polyester, acrylic, and epoxy because of the high degree of flexibility. They also have excellent adhesion and are relatively resistant to heat and chemicals.
But here is the catch. These materials have a significant coefficient of thermal expansion, and this is why the internal thickness of the film should not exceed 0.05 mm.