The document analyzes the potential for lead cracking in a TQFP32 package under vibration testing. A Solidworks simulation modeled the package and circuit board to determine major resonances and peak lead stresses. The simulation found a package resonance at 50kHz from lead frame and package bending. HALT testing was predicted to induce a peak lead stress of 65,000 psi, above the copper alloy's endurance limit of 20,000 psi, indicating a potential for fatigue cracking in the leads from the hammer blows.

1. TQFP32 package
HALT vibration analysis
lead cracking potential ?
3/20/2018 rev A
Don Blanchet
3B Associates
dwb3298@verizon.net
Prepared for: MDA-IBM Burlington , MA
mm(inch)

2. Hand Soldering

3. Goals
 Determine major resonances and
stresses experienced in a test board
random vibration & HALT qualification
sequence.
 Estimate peak lead frame maximum
stress.

4. Method
 Solidworks 2018 Simulation -
frequency and dynamics FEA analysis
modules

5. Package model
Copper alloy leads (lead frame)
Molded plastic body

6. Test assembly model
meshed for FEA
BET ckt bd .062 thick
No underfill

7. Package resonance – 50khz lead
frame and package bending

8. HALT peak lead stress: 65,000
psi from board bending

10. HALT hammer blow testing
one hour cumulative
 50,000 cy/sec x 60 sec/min x 60 min/hr = 1.8
e+08 cycles
 70 Grms input >>Peak lead stress = 65,000 psi
 Copper alloy endurance limit ~ 20,000 psi
 Fatigue crack Damage potential is predicted
from hammer test