2. Solder Fatigue Analysis
For Intermediate Users
Dr. Natalie Hernandez

3. Agenda Introduction Fundamental theories Examples
What’s the problem we’re all trying to solve?
What’s the cause?
Fundamental theories
Engelmaer
the Blattau model
Examples
Modeling leaded components
Surface mounts
BGA (simple array and non-traditional array)
Through-hole
Radial
Modeling leadless components
QFN

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5. WHAT’S THE PROBLEM

6. UNEXPECTED SOLDER FAILURES
Increasing number of companies reporting early life failures during the manufacturing process or during testing or in the field
UNEXPECTED SOLDER FAILURES
Classic solder fatigue approaches do not seem to be capturing these risks

7. WHAT’S THE CAUSE?

8. With the advance of technology…
Electronics are shrinking and becoming denser and more complex
iPhone 8
Space Controller

9. Fundamental Theories

10. STRAIN RANGE + CLOSED FORM EQUATIONS
𝑁 𝑓 = ∆𝛾 2𝜀 𝑓 𝑐
∆𝛾=𝐶 𝐿 𝐷 ℎ 𝑠 ∆𝛼∆𝑇
𝜀 𝑓 =0.325
Distance to neutral? Brilliant
Deriving key constants based on flawed test conditions (Wild)? Problem
Isothermal mechanical (not actual behavior)
Between 25C and 100C (overestimates creep)
4 to 300 cycles per hour (underestimates creep)
𝑐= −0.442 − 6𝑥 10 −4 𝑇 𝑠 +(1.74𝑥 10 −4 )[ ln 1+𝑓 ]
Engelmaier, W.; , "Fatigue Life of Leadless Chip Carrier Solder Joints During Power Cycling," Components, Hybrids, and Manufacturing Technology, IEEE Transactions on , vol.6, no.3, pp , Sep 1983

11. STRAIN ENERGY + FINITE ELEMENT ANALYSIS (FEA)
Strain energy (work) used to predict crack initiation and crack propagation
𝑁 0 =𝐾1 ∆𝑊 𝑎𝑣𝑔 𝐾2
𝑑𝑎 𝑑𝑁 =𝐾3 ∆𝑊 𝑎𝑣𝑔 𝐾4
𝑁 𝑓 = 𝑁 0 + 𝐷 𝑑𝑎 𝑑𝑁
Darveaux, R., “Solder Joint Fatigue Life Model,” Proceedings of TMS Annual Meeting, Orlando FL, February 1997, pp

12. STRAIN ENERGY + CLOSED FORM EQUATIONS
Closed Form, PCB Stiffness, Strain Energy, E (T), Tg, Die Shadow
N. Blattau and C. Hillman, “An Engelmaier Model for Leadless Ceramic Chip Devices with Pb-Free Solder,” Journal of the Reliability Information Analysis Center, First Quarter 2007, 6-11

13. Solder Fatigue Tool

14. Defining your environments

15. Life Cycles User guide Webinar Edit Properties: Defining Phases
Edit Properties:
Define reliability metric
Defining Phases
Environment: MIL-217 or TR-332
Duration of Phase must cover all events
Temperature cycle must begin and end at same temperature

16. Closer Look at Thermal Cycles
Example of a generic temp cycle (-10 to 100°C)
The whole board is changing temperature
But the Min and Max temps of the board can be different than (-10°C) od 100°C
Let’s look at a demo!

17. Thermal Maps Sources: Apply thermal maps
IR camera
Board side
Thermal analysis
MIN and MAX
Direct measurement
You can have 4 maps for 1 temp cycle
Any Picture
Align the board and legend
Legend orientation
Let’s look at a demo!

18. Defining your materials

19. Laminate Manager

20. Material Manager

21. Package Manager

22. Defining your leads

23. Lead Modeling C-Lead, J-Lead, Gullwing, Stub, leadless QFP FETS
BGA Balls
More details provided in user guide

24. BGA Ball Modeling “Ball” tab in the part editor
Ball Modeling: Enabled
One or two elements
Patterns
Full
Perimeter
Channel
Island
Corner depopulate balls
Using the ball count
Only works for regular patterns
Use mount point method for specialized patterns
Use with “Potting”
Underfill
Corner staking
Edge bonding

25. Examples

26. LIFE CYCLE Test condition
-40°C to +125°C, dwell 20 minutes hot and cold, 15°C/min ramp rate
Field conditions
Standard day: 15°C to 50°C, 90-min hot dwell, 360-min cold dwell, 2300 cycles
Tropical day: 32°C to 70°C, 90-min hot dwell, 360-min cold dwell, 800 cycles

27. MPC5554 – PACKAGE DIMENSIONS

28. MPC5554 – BALL DIMENSIONS
Provided by cross-section results

29. MPC5554 – 3D MODEL CONFIRMATION

30. MPC5554 – DIE DIMENSIONS Die Size Die Thickness
35% of exterior dimensions: 0.35 x 27 = 9.45mm
Die Thickness
Overmold thickness – 0.2 (for wire bond) – 0.1 (for die attach) = 0.3mm

31. RESULTS – MPC5554 Cycles to failure (TEST): 4263
Board CTE: ppm/C
Damage: 19.9
Cycles to failure (FIELD): 117,299
Damage: 0.02

32. TPS54622 – PACKAGE DIMENSIONS

33. Tg Correction of effective CTE & E
Elastic Modulus

34. TPS54622 – PAD DIMENSIONS

35. TPS54622 – FLAG DIMENSIONS

36. TPS54622 – DIE DIMENSIONS Die Size Die Thickness
Equivalent to the thermal pad
2.05 x 2.05
Die Thickness
0.9 – 0.2 (leadframe) – 0.2 (for wire bond) – 0.1 (for die attach) = 0.4mm

37. RESULTS – QFN Cycles to failure (TEST): 10682
Board CTE: ppm/C
Damage: 7.94
Cycles to failure (FIELD):
Damage: 0.014

38. Dr. Natalie Hernandez, Product Manager
Questions?
Dr. Natalie Hernandez, Product Manager