High reliability soldering for surface and mixed mount printed circuit board assembly
1Key Takeaways
Standard Name: High Reliability Soldering for Surface and Mixed Mount Printed Circuit Board Assembly Standard Number: QJ 3086A-2016 Scope: This standard specifies the technical requirements, inspection requirements, and reliability verification for high-reliability soldering of surface and mixed mount prin…
2Expert Interpretation
Comprehensive analysis of the high reliability welding technical requirements for surface and hybrid mounted printed circuit board assemblies in the QJ3086A-2016 standard, covering process flow, material selection, equipment specifications and inspection methods, which is applicable to welding quality control of aerospace electronic products.
Standard Evolution and Technology Upgrade
QJ3086A-2016, as the core standard for welding processes in the aerospace industry, has undergone 8 major revisions compared to the 1999 version: adding mixed installation selection principles, improving welding requirements for new packaging devices, introducing a reliability verification system, etc., reflecting the ultimate pursuit of process reliability by aerospace electronic equipment.
Key points of process control
| Control dimension | Surface mounting | Mixed mounting |
|---|---|---|
| Installation sequence | Single-sided/double-sided mounting | Surface mounting first, then through hole |
| Temperature control | 220-250℃ reflow | Dual process temperature coordination |
| Stress management | Thermal expansion coefficient matching | Dual control of mechanical + thermal stress |
Typical application cases
When a satellite control system used BGA packaged devices, it strictly followed the standard 4.1.3 to reserve 5mm of rework space, and used X-ray inspection to ensure that the solder ball offset was less than 15%, and successfully passed 200 -50~100℃ temperature cycle verifications.
Material selection specifications
- Solder: Sn63PbAA eutectic solder is preferred, and silver-containing devices use Sn62Pb36Ag2
- Flux: Rosin-based (R type) or medium-active rosin-based (RMA type)
- Cleaning agent: Non-corrosive solvents such as anhydrous ethanol and isopropyl alcohol
Reliability verification system
The standard innovatively establishes a three-level verification mechanism:
- Vibration test: sinusoidal vibration 5-2000Hz/20g, random vibration 7.1Grms
- Temperature cycle: -50~100℃/200 cycles
- Destructive analysis: Metallographic inspection crack area ≤25%
Implementation suggestions
Process optimization direction
1. For QFP devices, it is recommended that the lead forming angle be controlled at 45-90°, and the bending radius be ≥ the lead diameter
2. Adopt a step-by-step temperature curve management: preheating zone (120-150°C), insulation zone (150-180°C), reflow zone (220-250°C), cooling zone (＜100°C)
3. Establish a solder paste thickness control matrix:
| Lead spacing (mm) | Stencil thickness (mm) |
|---|---|
| ≥0.65 | 0.15-0.20 |
| 0.5-0.65 | 0.10-0.15 |
| <0.5 | 0.05-0.10 |