How is the test performed?

A hook is placed under the wire bond loop at its highest point. The hook pulls upward at a controlled rate (typically 10-50 mm/min) while measuring force. The test records peak force and failure mode: wire break (mid-span), heel break (at bond foot), ball lift (at first bond), or wedge lift (at second bond). Wire break is the preferred failure mode, indicating good bonds.

Per MIL-STD-883 Method 2011: 25 micron (1 mil) gold wire requires minimum 3 gf (gram-force). 33 micron (1.3 mil) gold wire: 5 gf minimum. 25 micron aluminum wire: 2 gf minimum. 50 micron (2 mil) aluminum ribbon: 5 gf minimum. RF power devices using 50-75 micron gold wire may require 15-25 gf. Actual values should be 2-3x minimum for production margin.

Failure mode interpretation?

Wire break (mid-span): ideal, indicates bonds are stronger than wire. Ball lift: bond pad contamination, insufficient ultrasonic energy, or incorrect temperature. Heel break: excessive loop height stress, work hardening at bond foot. Wedge lift: insufficient bonding parameters at second bond. Any non-wire-break failure triggers process investigation.

Manufacturing

Bond Pull

Bond Pull is a destructive mechanical test that measures the force required to break a wire bond by pulling it upward with a hook at its loop apex. Defined by MIL-STD-883 Method 2011, it verifies bond integrity by recording peak force and failure mode (wire break, heel break, ball lift, wedge lift). Wire break at mid-span is the preferred failure mode, indicating bonds stronger than the wire itself. Critical for RF power devices where bond wires carry high currents.

Category: Manufacturing

Standard: MIL-STD-883 M2011

Understanding Bond Pull Testing

Wire bonds are the electrical interconnects between semiconductor dies and package leads. In RF power transistors, multiple parallel gold or aluminum bond wires carry the signal current and define the package inductance. Bond integrity is critical: a single failed bond wire increases current density in remaining wires, leading to cascading failure.

Bond pull testing is performed on sample bonds during production qualification and as a periodic process monitor. Results are plotted on control charts to detect bonding machine degradation (worn capillary, ultrasonic energy drift, temperature changes).

MIL-STD-883 Minimum Pull Forces

25 μm (1 mil) Au wire: 3 gf minimum
33 μm (1.3 mil) Au wire: 5 gf minimum
25 μm Al wire: 2 gf minimum
50 μm Al ribbon: 5 gf minimum

Production target: 2-3× minimum
Cpk ≥ 1.33 for production capability

Failure Mode Analysis

Mode	Location	Cause	Action
Wire break	Mid-span	Good bond (desired)	None
Ball lift	1st bond	Pad contamination	Clean/requalify
Heel break	Bond foot	Loop stress	Adjust loop profile
Wedge lift	2nd bond	Low US energy	Increase parameters

Common Questions

Frequently Asked Questions

Procedure?

Hook under loop apex, pull at 10-50 mm/min, record peak force and failure mode. Wire break = good. Bond lift = investigate.

Minimum force?

25 μm Au: 3 gf. 33 μm Au: 5 gf. 50 μm Al ribbon: 5 gf. Production target: 2-3× spec minimum.

Failure modes?

Wire break (ideal), ball lift (contamination), heel break (stress), wedge lift (low energy). Non-wire-break triggers investigation.

Related Terms

← Bond Line Thickness Bond Wire Inductance →

Wire Bonding

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