Experimental board includes three layers of special tridirectionally woven fabric. Alumina particles play major role in reducing coefficient of expansion. They also serve as heat sink for heat-generating components

Patterson, W. J.

English

NASA Technical Reports Server

AjtiI 1975	
.	 B75-10039 
.NASA TECH BRIEF 
Marshall Space Flight Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Improved Printed-Wiring Boards for High-Reliability Circuits 
e
In some applications high-reliability electronic 
circuits are subjected to extreme temperature 
variations. The temperature variations cause cracked 
solder joints on the printed-wiring boards (PWB's). 
These failures occur because the joints and the boards 
have different coefficients of thermal expansion. A 
study was conducted to see if the reliability could be 
improved by changing the board coefficient of 
expansion. The results of this study are published in a 
report. 
The report evaluates three polyimide laminates as 
PWB's and compares them with the commonly-used 
epoxy board. Two polyimide boards are commercially 
used; the third is an experimental model. The basic 
problem to be resolved is to find a board with the 
lowest coefficient of thermal expansion normal to the 
board plane. 
Tests have been conducted on all three polyimide 
boards by subjecting them to temperature cycling 
between the temperatures of -55° to 100° C using 
different time intervals. The experimental board has 
indicated the lowest coefficient of expansion ranging 
from 1540- 6
 to 2040- 6 cm/cm-°C perpendicular to 
its plane. This value is less than half of those for the 
other boards. 
The experimental board includes three layers of 
special tridirectionally woven fabric. Each fabric layer 
is impregnated with approximately 75 percent resin 
solution, 24 percent high-fired alumina, and 1 percent 
silane coupling agent. The alumina particles play a 
major role in reducing the coefficient of expansion.
They also serve as a heat sink for the heat-generating 
components. Two layers of special glass cloth are 
placed on each side of the fabric core. Finally two thin 
sheets of copper are bonded to the top and the bottom 
of the board. 
The new board, described in detail in the report, 
has other desirable characteristics equivalent to those 
of the epoxy glass laminate boards. Its mechanical 
and electrical properties match those of the epoxy 
boards. In addition, it can be produced commercially 
using standard PWB technology. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Marshall Space Flight Center 
Code ATO1 
Marshall Space Flight Center, Alabama 35812 
Reference: B75-10039 
Patent status: 
Inquiries concerning rights for the commercial use 
of this invention should be addressed to: 
Patent Counsel 
Marshall Space Flight Center 
Code CCO1 
Marshall Space Flight Center, Alabma 35812 
Source: W. I. Patterson
Marshall Space Flight Center

(MFS-23147) 
Categories: 01 (Electronics - components and 
Circuitry) 
06 (Mechanics) 
08 (Fabrication Technology)
	 . 
This document was prepared under the sponsorship of the National
	
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Aeronautics and Space Administration. Neither the United States
	
information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19750000039 2020-03-19T20:02:22+00:00Z


Improved printed-wiring boards for high-reliability circuits

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