REG NASA-LLIS-0275--1993 Lessons Learned Stressed or Damaged Solder Joints on Flight Hardware Due to Thermal Cycling.pdf

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1、Lessons Learned Entry: 0275Lesson Info:a71 Lesson Number: 0275a71 Lesson Date: 1993-07-09a71 Submitting Organization: JPLa71 Submitted by: T. Borden / B. WagonerSubject: Stressed or Damaged Solder Joints on Flight Hardware Due to Thermal Cycling Abstract: Over the years, numerous incidents of failed

2、 solder joints have occurred to electronic equipment at JPL and contractor facilities. The problem was traced to thermal cycling of conformal coatings.The lesson recommendations pertain to prediction of the thermal cycling environment, application of conformal coatings, packaging design reviews, and

3、 packaging design and fabrication processes, procedures, and documentation. Description of Driving Event: During recent years numerous incidents of failed solder joints in electronic equipment have been identified in hardware fabricated both at JPL and JPL Contractor facilities. Examples include:1.

4、GALILEO, PFR #52012, Command Data Subsystem: Intermittent failure in solder joints at flat pack lead attachment to the printed wiring board.2. ASTROS Star Tracker, PFR #33998, Electronic Assembly failure: Solder connection open at a Dual Inline Package Integrated Circuit (DIP IC) lead to the printed

5、 wiring board.3. MAGELLAN, PFR #55263, Data Formatter, Electronic Assembly failure: Solder connection open at a DIP IC lead to printed wiring board.4. WF/PC-1 PFR #53914 Microprocessor failure: Solder connection open at a DIP IC lead to printed wiring board.5. ACRIM II, PFR #44478: Electronic Module

6、 solder joints were observed to have stressing/cracking at the DIP IC lead to printed wiring board interconnect.6. MLS, PFR #43374: Solder joint on input bias wire had stress cracks.Investigation of the above items reveal a common element of cause. Conformal coating (polymeric Provided by IHSNot for

7、 ResaleNo reproduction or networking permitted without license from IHS-,-,-substance applied to protect from the environment) material filled the space between the printed circuit board and the bottom of the electronic component, and thermal cycling, and/or prolonged exposure to solvents, created t

8、he large forces required to cause solder joint fracture.Lesson(s) Learned: 1. Solder joints will be damaged due to fatigue stresses induced by thermal cycling in the presence of high thermal coefficient of expansion materials, or by the exposure of conformal coatings to some cleaning solvents.2. Exc

9、essive conformal coating material between the printed circuit board and bottom of the electronic component, combined with environmental factors, can create forces sufficient to cause solder joint fracture.Recommendation(s): 1. Solder fatigue life should be treated as a mission consumable for the pac

10、kaging design. Estimate the total mission thermal cycling expected in ground and flight operations, and compare with the demonstrated fatigue life capability of the hardware.2. The space between the printed circuit board and the electronic components must not be filled with conformal coat material u

11、nless thermal heat sinking is needed, and then the material must not exceed the thickness specified in approved documentation.3. Packaging design reviews should assure that approved design processes and procedures have been met.4. Electronic packaging design and fabrication must follow proven and qu

12、alified processes and procedures, and documentation must be regularly updated and maintained to meet current design needs.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): Provided by IHSNot for ResaleNo reproduction

13、 or networking permitted without license from IHS-,-,-a71 Environmenta71 Flight Equipmenta71 Hardwarea71 Industrial Operationsa71 Parts Materials & ProcessesAdditional Info: Approval Info: a71 Approval Date: 1992-07-16a71 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-,-,-