New Material And Construction Methods Deliver The Best Rigid-Flex Boards

PCBs are of two types; rigid and flex PCBs. The former has further sub-classifications that include single-sided, double-sided and multi-layer PCB. When classified against quality, there are three classes; Class 1, Class 2 and Class 3. Among these three, the features of a Class 3 board have the highest requirements. The differences in quality can lead to variations in terms of complexity, testing and inspection methods. Up until today, most electronic products make use of multi-layer and double-sided PCBs. Flex PCBs are unique and manufacturers use them under specific circumstances. However, the demand for portable electronic devices is constantly on the rise. That is why engineers focus on combining flexibility and functionality.

About rigid-flex circuits

It is possible to shape rigid-flex boards Capel Technology Co., Ltd to fit inside any electronic device. These integrated hybrid circuit boards are a mixture of rigid PCBs and flex circuit technology. Understandably, they possess the benefits of both types. The features of a rigid-flex circuit board allow greater freedom to manufacturers regarding packaging. It also reduces interconnections significantly but it retains precision, repeatability, and density of PCB technology. Rigid-flex circuits are now all over the electronic industry. The aerospace, military, and medical industries are some of the most demanding buyers of flex PCBs. Flexible circuit designs are now better than ever.

Modern designs

The designing procedure of rigid-flex boards evolved significantly with time. The designs of today require rigid areas to be exceptionally capable. The modern PCBs have the same limits of complexity and density. Some of these advancements resolved a few construction-related issues. The older methods incorporated the use of glues with a high thermal expansion coefficient. Due to the use of such adhesives, vias used to under significant stress during thermal cycles. Besides, the application of glue on the rigid areas can lead to cracks in the copper-plated areas. Adhesives used in rigid-flex designs come from three different sources. These are the copper-clad flex laminate, the coverlay construction method, and the material used to bind the rigid and flexible layers.

Constructions without adhesives

PCB designs without the use of glue appeared to replace its use in copper-clad flex laminates. As you may know, manufacturers used to combine the copper layers with the polyimide core using modified epoxy or acrylic. The adhesive laminate gad the copper attached to it directly on the polyimide core. Upon eliminating the use of glue to bind the layers, manufacturers started creating thinner PCBs. The design is much more flexible than before and the reliability of such PCBs increased tremendously. Apart from that, designers found that the copper-clad laminates became better in terms of performance without the application of glue.

To end

Coverlay constructions exhibited problems in rigid-flex designs. The older methods included the use of full coverage coverlays that occupied the entire rigid areas. The vias plated through holes would remain exposed to an excessive Z-Axis thermal expansion stress created by the coverlay adhesive. PCB designers developed selective coverlay constructions to solve the issue. It restricts the coverlays to the exposed flex regions. The PTH and the via holes also remain restricted from the interface zone.