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PCB Resin Distribution Fibers for Resin Starvation Prevention

IP.com Disclosure Number: IPCOM000243576D
Publication Date: 2015-Oct-01
Document File: 4 page(s) / 305K

Publishing Venue

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Disclosed is a method to prevent resin starvation during the lamination process for printed circuit boards.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 51% of the total text.

Page 01 of 4

PCB Resin Distribution Fibers for Resin Starvation Prevention

As printed circuit boards (PCBs) become more complex, the need to reduce and eliminate hollow glass fibers and resin starvation is needed in order to ensure reliability of the final assembled PCB. When hollow fibers exist, conductive filament formation (CFF) can occur. "CFF is an electrochemical process that involves the transport (usually ionically) of a metal through or across a non-metallic medium under the influence of an applied field. CFF can result in either leakage currents which reduce performance or catastrophic shorts that cause complete failure".
[1] Further, when resin starvation occurs, the PCB laminates are susceptible to severe stress that can lead to crack propagation. In Figure 1 below, resin starvation and hollow fibers both exist, causing the PCB to be rejected. Boxed area has both hollow (glistening) fibers and resin starvation.


Disclosed is a method to eliminate CFF and prevent resin starvation using resin distribution fibers in PCB laminate manufacturing. The core idea of the invention is as follows: hollow glass fibers are generated and then modified to incorporate holes along the length of the fibers. Next, the newly generated fibers are filled with a low viscosity, liquid epoxy such as those available from the Dow Chemical Company. [2] The epoxy resin contains a photoacid generator [3] curing agent which allows for photolatent curing. The ends of the hollow glass fibers are then capped by locally curing the ends of the fibers. After the filled resin distribution fibers are manufactured, they can be woven into mesh, impregnated with resin, and used in PCB laminate manufacturing.

The invention works as follows: hollow fiber manufacturing is known to those skilled in


Page 02 of 4

the art. The hollow fibers after production are cut to length and then further modified to incorporate holes along the length of the fibers. One method of generating the holes is via laser but other methods may be chosen by those skilled in the art. The holes along the length of the fiber are small enough to prevent leaking of the low viscosity, liquid epoxy resin that will fill the hollow fiber. The holes along the length are of a size that provides capillary forces preventing...