EXOTIC PCB MATERIALS

As a usual, we come across statements like the two most critical/flashing determinants that have an impact on the PCB performance; power and heat. The level and specifications of these two factors of your application dictate the appropriate material of your PCB’s substrate.

In addition, the following exotic materials — and the unique advantages each offers — can bring even more advantages to today’s cutting-edge PCB designs:

• Fluoropolymers: The PCB substrates having fluoropolymer resins or the fluoropolymers generally offer a high level of chemical and stress crack resistance along with high temperature resistance. Further they provide a low-COF, mechanically robust material that is suitable for electrical and cabling applications in pharmaceutical and biotech and food industries.
• Polyimide: Yet, one of the most interesting advancements in PCB design is the continually increasing use of flexible, and rigid-flex PCBs. These boards are opening a new vista to PCB applications because they can be folded and wrapped around other objects. As the name suggests, flex boards can be flexed while continuing to resolve a flow of electrical currents from one side of the board to the other side. This new generation of PCBs is generally prepared with a layer of polyimide that has very high heat dissipation property as well as has significantly consistent dimensions.
• Acrylic adhesives: Acrylic adhesives based on their performance are the one’s which can retain a degree of flexibility while the cure is an added advantage when one is searching for a good substrate material for diverse dynamic uses. But when flame retarding is an important factor, then chemical flame retarding agents have to be added in the acrylic adhesives for UL 94V-0 ratings but it lessens the dynamic performance of the part. Also, it has been ascertained that when the temperature gets to around 180°C, the acrylic adhesives used in the lay-up can start to melt and with this, separate any of the PCB layers that may be attached to the copper vias. Co-efficient of expansion of acrylic adhesives is also high to appear to be less of other exotic substrate material types.
• Epoxy adhesives: In contrast to the acrylic adhesives, epoxy adhesives form a hard skin, which excludes them in the great majority of dynamic joints. The expansion coefficient to some extent is lower but bond strength is very good, so its use is well justified in cases where multi-layer PCBs are to be exposed to high temperature conditions during operation. Besides, they exhibit high chemical and moisture resistance, and therefore epoxy adhesives are suitable for use in the manufacturing of PCB substrates dealing with sensors that are in touch with moisture, for instance, in medicine and healthcare.
• Liquid crystal polymers:LCP or liquid crystal polymers are a kind of thermoplastic that is frequently used in boards such as the multi-layer PCB when thin profiles are preferred. They are low density and can be bent as can be seen from the fact that they have brilliant electrical properties that leads to their suitability for high frequency applications, weight and thickness discourage.