Study consisted of an analytical approach, in which a mathematical model of existing printed circuit board component mounting techniques was analyzed, and an empirical investigation was performed to determine the extent of damage caused by temperature cycling of the printed circuit boards

Moore, R. L.

Vinson, R. J.

English

NASA Technical Reports Server

"a 
December 1969
	
Brief 69-10807 
NASA TECH BRIEF 
NASA Teèh Briefs are issued to summarize specific innovations derived from the U.S: space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Investigation of the Development of Cracks in Solder Joints 
.
r
The design of printed circuit board assemblies does 
not allow for the thermal stress produced on solder 
joints during operation in an environment with ex-
treme temperature ranges. The relative difference in 
the expansion and contraction of the printed circuit 
boards and the components or component parts (in-
cluding conformal coatings) used to fabricate the 
boards is reflected as a force in the component lead 
and causes stress and cracking in the soldered con-
nection. A study was initiated to investigate the de-
velopment of cracks in the solder joints and to recom-
mend solutions that could be implemented into exist-
ing hardware assemblies with no further design 
changes. The study consisted of two phases. In the 
first phase, an analytical approach was used in which 
a mathematical model of existing printed circuit board 
component mounting techniques was analyzed and the 
forces on critical components were calculated. This 
approach permitted an insight into the basic problem, 
and thus led to ideas that could provide solutions to 
the problem. Mathematical models utilizing the pro-
posed solutions were then analyzed to determine the 
theoretical validity of the solutions. 
The second phase, an empirical investigation, was 
performed to determine the extent of damage caused 
by temperature cycl,ing of the printed circuit boards 
under question and to determine the practical validity 
of the proposed solutions to the problem of the devel-
opment of cracked solder joints. During the empirical 
investigation, boards were fabricated and inspected 
in accordance with standard requirements. Several 
boards were fabricated totest both the normal pro-
cedures for mounting components and the proposed 
recommendations for mounting components that 
would rectify the problem. The results of the analytical 
and empirical investigations were compared to deter-
mine correlation of results achieved. The test data 
obtained in the empirical investigation confirmed that 
the use of a resilient pad greatly reduced the amount 
of force applied to a solder joint due to temperature 
changes; the use of the pad greatly reduces the number 
of cracked solder joints without redesign of the printed 
circuit boards. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B69-10807 
Patent status: 
No patent action is contemplated by NASA. 
Source: R. L. Moore, and R. J. Vinson of 
Sperry Rand Corporation 
under contract to 
Marshall Space Flight Center 
(MFS-20444) 
Category 01 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
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.
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Investigation of the development of cracks in solder joints

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