1、Lessons Learned Entry: 0561Lesson Info:a71 Lesson Number: 0561a71 Lesson Date: 1997-07-31a71 Submitting Organization: JPLa71 Submitted by: D. Oberhettinger/G. KunstmannSubject: Voyager Plated - Through Hole Failures (1976) Abstract: During initial testing of multi-layer circuit boards for Voyager, d
2、efective copper plating was found to have caused cracks in the barrels of plated-through holes. Recommendations involve monitoring of fabrication processes, performance of thermal cycling screening tests, and use of test coupons.Description of Driving Event: In January 1976, a problem became evident
3、 during initial testing of the earliest Command & Control Subsystem (CCS) subassemblies for Voyager. Detailed testing revealed multiple, often intermittent, functional failures. The failures were traced to the multi-layer boards (MLBs), specifically the plated-through holes (PTHs).refer to D descrip
4、tion DThe extent of the problem was determined by subjecting selected subassemblies to a detailed sequence of resistive measurements and temperature cycling. The sequence was designed to stress the PTHs without over-stressing the components installed on the MLBs. MLB fabrication documentation, test
5、history, and theoretical analyses were reviewed. Failure analysis of hard failures, PTHs that exhibited early signs of failures, and PTHs which had appeared acceptable, revealed PTH copper plating that was marginal - too thin and of insufficient ductility.This incident involved Viking board designs
6、inherited by Voyager. The Voyager boards were fabricated 3-4 months later in a follow-on contract in which the same contractor presumably used the same specification and process. However, micro-photographs of the Voyager boards showed insufficient plating, and metallurgical tests showed insufficient
7、 ductility. A metallurgical test was Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-subsequently performed on one of the earlier Viking boards: it showed the copper to be more ductile.Reference(s):a71 “MJS MLB Failure Investigation Report,“ June 197
8、6.a71 Voyager Problem/Failure Report No. 36970, Jet Propulsion Laboratory, opened 04/13/76, closed 01/18/77.a71 Gibbel, M., “Summary of JPL Printed Circuit Board Failures,“ Jet Propulsion Laboratory Document TETA-029, October 1995.Lesson(s) Learned: 1. If circuit board fabrication specifications or
9、processes fail to provide for copper plating of the proper thickness and ductility, internal interconnect failures (such as cracks in the barrels of plated-through holes) may occur after only a few thermal cycles.2. Since this incident, research has indicated that the frequency of barrel cracking in
10、creases with increasing aspect ratio of the PTH (depth/diameter) as well as with decreasing barrel wall thickness.Recommendation(s): 1. Manufacturing, fabrication, and assembly processes employing complex technology require constant monitoring, auditing, and review of the appropriate process paramet
11、ers despite repeated past successes. Even minor changes in processes or materials can result in the product falling below acceptable standards. Efforts must be made to increase the consistency and margin of all processes to preclude defects due to production variations.2. Thermal cycling screening t
12、ests should be performed on unpopulated printed wiring boards regardless of process maturity.3. Circuit board manufacturing processes should continue to use test coupons to determine individual board acceptability.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMissi
13、on Directorate(s): Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N/AAdditional Key Phrase(s): a71 Hardwarea71 Parts Materials & Processesa71 Test & VerificationAdditional Info: Approval Info: a71 Approval Date: 1997-08-13a71 Approval Name: Carol Dumaina71 Approval Organization: 125-204a71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
