Wire Pull Test – Process Overview

What is a Wire Pull Test?

Wire pull testing is a vital method for assessing the mechanical strength and reliability of wire bonds in semiconductor and microelectronic devices. It is widely used in R&D, production, and quality assurance environments to ensure the integrity of interconnects.

The wire pull test involves applying a controlled upward force to a bonded wire using a precision hook or tool. The wire is pulled until it either breaks or detaches from the bond site.

There are two main test methods:

• Destructive wire pull testing: Measures the ultimate strength of the bond by pulling until failure.
• Non-destructive wire pull testing: Applies a predefined load for a set duration to verify bond integrity

This process is used to evaluate wire bond strength, wire integrity and bond failure modes. Ideally, wires should break mid-span when pull tested but loop height, bond quality, bonding method and to a lesser degree operator or hook type, will all influence the test results. Other failure modes include wire breaks at bond heel or above a ball bond, which are normally classed as acceptable and bond lifts due to interface failure or metallisation lift, which typically classed as unacceptable.

Wire Pull Test to MIL-STD-883?

Wire bond pull testing is covered by the external standard MIL-STD-883 (Methods 2011.7 for destructive testing and 2023.5 for non-destructive). Nordson DAGE bond testers fully conform to or exceed these standards. The standards contain specifications for acceptance or rejection criteria.

Testing is typically performed on semiconductor and related microelectronic devices using the following wire bonded or gap welded interconnects:

• Fine wire diameters (typically 12.5 to 75 micron)
• Large wire diameters (typically 100 to 500 micron)
• Ribbons (typically up to 2000 x 250 microns)

Wire Pull Test Equipment & Capabilities

Inseto supplies wire pull test equipment from Nordson DAGE, including the STELLAR 4000 series and advanced 4000Plus series of bond testing systems for operator driven tests and the 4600 Bond tester, which automates the traditional manual bond testing processes.

These systems offer pull test cartridges with high-precision load measurements that cover a range of pull forces and allow destructive or non-destructive testing. Note, an appropriate hook should also be used, which in the case of wire bonds, is a minimum of 2x the wire diameter being tested.

Another popular pull test method is “Vector Wire Pull Testing”, which simulates a perpendicular test angle between the two wire bonds, when the surface heights for each bond are different. This is achieved by coordinating the X-Y and Z axis of the wire pull tester, so the test is performed at the required optimized angle.

Small geometry (Ultra Fine Pitch) applications are becoming more and more popular and as such Nordson DAGE offers equipment specifically for this function. A test can be performed manually or semi-automatically to a pre-programmed test routine.