How to use this guide
It describes method, not a checklist we impose. On an audit the requirement is always
your specification and the supplier’s own control plan. Test methods and limits differ by
customer and package; where we name a standard below, it’s one that’s commonly used, not
one that applies by default.
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Bond program and parameter control
- We look at
- Whether the program on each bonder matches the released revision, who can change parameters, and how changes are approved and recorded.
- Good looks like
- Programs under revision control, edit access restricted by login, every change linked to an approved request.
- Common gap
- Parameters adjusted at the machine to clear a problem, and never written back into the released program.
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Capillary management
- We look at
- Capillary type against the program, life limits by touchdown count, and change records.
- Good looks like
- Life counters that reset only when a change is recorded, and the capillary lot traceable to the product bonded with it.
- Common gap
- Counters reset without a change, or capillary lot not recorded on the lot traveller.
-
Wire material
- We look at
- Wire type and diameter against the bill of materials, storage conditions, shelf life once opened, and lot traceability.
- Good looks like
- Opened spools labelled with an expiry, and stored as the wire maker specifies; copper wire handled to limit oxidation.
- Common gap
- Partly used spools returned to stock without an opening date.
-
Free air ball formation
- We look at
- How free air ball size and shape are checked, and when.
- Good looks like
- Checks after every capillary or wire change and after electronic flame-off adjustments, not only at set-up.
- Common gap
- Checks done at initial set-up only.
-
Bond strength monitoring
- We look at
- Ball shear and wire pull frequency and sample size against the control plan, the test method, and whether failure modes are recorded as well as force.
- Good looks like
- Tests at the stated frequency on every shift, failure mode recorded for each pull, results charted. Commonly referenced methods include JESD22-B116 for ball shear and MIL-STD-883 Method 2011 for bond pull.
- Common gap
- Testing less often than the control plan says, as in the finding in our sample report.
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Test equipment
- We look at
- Calibration of shear and pull testers, how shear tool height is set, and whether the test itself has been through measurement system analysis.
- Good looks like
- Calibrated testers, a defined shear height set-up, and a gauge study on the test.
- Common gap
- The tester is calibrated but the test method has never been studied, so operator-to-operator variation is unknown.
-
Reaction plan
- We look at
- What happens when a bond test fails: how far back product is held, and how it is dispositioned.
- Good looks like
- Hold everything bonded since the last conforming test, with a documented and approved disposition.
- Common gap
- Only the current magazine is held, not everything back to the last good test.
-
Non-stick detection
- We look at
- Whether non-stick-on-pad and non-stick-on-lead detection is enabled and verified, and how operators respond to alarms.
- Good looks like
- Detection enabled and periodically verified, a written response procedure, and alarm counts trended.
- Common gap
- Detection sensitivity lowered or turned off to reduce stoppages.
-
Pad damage and cratering
- We look at
- Whether pads are checked for cratering and damage at a defined frequency, especially with copper wire or thin pad metallisation.
- Good looks like
- A periodic cratering check, with results recorded and reviewed.
- Common gap
- Cratering checked only during qualification, not in production.
-
Copper wire controls
- We look at
- Forming gas flow and how it is verified, oxidation control, aluminium splash checks, and how the copper process was qualified.
- Good looks like
- Gas flow verified, not just set; splash measured; a qualification that matches the customer’s requirements. AEC-Q006 is commonly referenced for automotive copper wire qualification.
- Common gap
- Gas flow set at installation and never verified.
-
Heater block and work holder temperature
- We look at
- Whether bond-site temperature is measured, not just the set point displayed.
- Good looks like
- A periodic measurement with a calibrated probe, against a stated tolerance.
- Common gap
- Reliance on the controller display.
-
Loop profile and wire sweep
- We look at
- How loop height is measured, whether that measurement has been validated, and how wire sweep after moulding is monitored.
- Good looks like
- A validated measurement method, and sweep checked after moulding with its own limits.
- Common gap
- The measuring equipment changed without the measurement being re-validated.
-
Bonder-to-bonder matching
- We look at
- How a program is transferred between bonders, and how results are correlated.
- Good looks like
- A written matching method with acceptance criteria, used whenever a program moves to another machine.
- Common gap
- Matching depends on one experienced technician, with no written method.
-
Maintenance and ultrasonic system
- We look at
- Preventive maintenance records, and calibration of the ultrasonic system and transducer.
- Good looks like
- Maintenance on schedule, ultrasonic calibration recorded, and a post-maintenance check before production restarts.
- Common gap
- Production restarts after maintenance without a bond check.
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Visual inspection after bonding
- We look at
- Inspection criteria and magnification against the customer’s specification, boundary samples, and inspector qualification.
- Good looks like
- Criteria at the station, boundary samples for each defect type, and inspectors who can explain them.
- Common gap
- Criteria that differ from the customer’s current specification revision.
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Operator qualification and set-up
- We look at
- Who is allowed to set up and adjust bonders, and whether their qualification is current.
- Good looks like
- A qualification matrix by task, with set-up restricted to qualified people.
- Common gap
- Qualification expired, while the person still performs set-ups.
Need a wire-bond line audited? Our VDA 6.3 and supplier audits can include an auditor with hands-on wire-bond experience. Start an audit request or see the VDA 6.3 process audit.