Wire Bond Pull and Shear Test Report Template
Wire pull and ball shear tests are the standard destructive checks on wire bond quality in an assembly line. This template gives you a clean report with the sample table, failure mode key and sign-off.
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Wire Bond Pull and Shear Test Report Template
Bond Test Report
Report no: WB-PT-2026-0319 Package / device: QFN-32 5x5, MCU-A2 Assembly lot: ASM-48812 Bonder: WB-14 Wire: Cu wire, 25 um (1.0 mil) Test performed: Wire pull and ball shear Test date: 2026-10-19
Acceptance Criteria
Wires sampled: 30 Minimum pull limit: 3.0 gf Minimum ball shear limit: 20 gf
Limits come from the customer specification or internal process control plan. Confirm the hook position and shear height settings are recorded on the equipment log.
Measurement Record
| Wire # | Pull (gf) | Pull failure mode | Shear (gf) | Shear failure mode |
|---|---|---|---|---|
| 1 | ||||
| 2 | ||||
| 3 | ||||
| 4 | ||||
| 5 | ||||
| 6 |
Failure Mode Key
| Code | Meaning |
|---|---|
| A | Wire break at neck above ball |
| B | Wire break mid-span |
| C | Bond lift at ball (ball lifted from pad) |
| D | Bond lift at stitch or second bond |
| E | Pad lift or cratering |
Result and Observations
Overall result: Pass
All 30 pulls above minimum. Lowest reading 5.1 gf. Failure modes: 28 neck break, 2 wire break mid-span. No lifted bonds. Shear mean 41 gf, no lifted ball.
Approvals
Use limits from your customer specification, the applicable method such as MIL-STD-883 test method 2011 or JESD22-B116, or your internal control plan. Pad lift or cratering results normally require engineering review even if the force is above the minimum. This template describes a typical record structure, not the text of any standard.
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How to use the report
Fill in the header fields from the assembly traveler: lot, device, bonder and wire. Enter the minimum pull and shear limits from the specification. Record each wire's force and failure mode in the measurement table, adding rows after export if you test more than six. Choose the overall result and write observations covering lowest reading, distribution of failure modes and any unusual findings. Export to PDF for the lot record or to Excel to add statistics. Complete the sign-off so the lot can proceed to molding.
- Copy limits from the control plan, not from memory
- Record every failure mode
- Note the hook position for pull tests
- Escalate any pad lift or cratering
Reading the failure modes
The force value alone is not enough. A pull reading above the minimum with a ball lift is a weak bond that happened to hold, while a neck break at a high force suggests a healthy process. Wire break modes indicate the interface is stronger than the wire, which is generally what you want. Bond lifts point toward process parameters such as ultrasonic power, bond force or temperature, or toward pad contamination and surface condition. Pad cratering shows excess energy or a fragile pad stack. Use the failure mode key so every technician reports the same codes.
Sampling and statistics
Sample size and frequency come from your control plan, often a set number of wires from several units at the start of each shift or after setup, capillary change or material change. Beyond pass or fail, compute mean and standard deviation by bonder and track them on a control chart. A mean that is drifting down while still above the minimum is an early warning. Cpk on pull strength is common in automotive programs, where a customer may set a minimum capability target for the characteristic.
Common mistakes
Frequent errors include hooking the wire off the loop center so the reading is lower than it should be, mixing pull results with different wire diameters in one average, and ignoring failure mode when force is acceptable. Others test only the first bond on each unit rather than a representative spread across the die. Calibrate the test equipment on schedule and record the calibration due date in the equipment log. Never discard a failing reading without an engineering reason on the record.
Frequently Asked Questions
What is a typical minimum wire pull value?
It depends on wire material and diameter and on the governing specification. Gold wire of 25 um diameter often has minimums around 3 gf in common standards, but you must use the value in your customer specification or process control plan.
What is the difference between pull and ball shear?
Pull testing hooks the wire and pulls upward to test the loop and bonds. Ball shear pushes a tool sideways against the ball to test the ball-to-pad interface. They find different weaknesses, so many programs require both.
Which failure modes are acceptable?
Generally wire breaks, at the neck or mid-span, above the minimum force are the preferred result. Bond lifts and pad lifts often require review even if forces are high. Follow the acceptance rules in your specification.
Does this work for copper and silver wire?
Yes, the report structure is the same. Change the wire field and the limits. Copper bonding is more sensitive to pad aluminum splash and cratering, so pay extra attention to pad lift observations.
If bond test results and equipment records are scattered across files and systems, Netray can help you consolidate and query them privately.
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