Newsletter: The Science of Bond Testing

28 December 2018

The Science of Bond Testing

We at XYZTEC look back at a great 2018 with many new innovations in bond testing and once again record breaking turnover, reaffirming our position as market leader worldwide. In the coming newsletters we will highlight some of the new key features of the Condor Sigma product line. This last newsletter of the year focuses on the science of bond testing in general.

The Science of Bond Testing is derived from decades of experience designing bond tests for the widest range of applications. It elevates bond testing to a science that takes you through the process of designing the optimum bond test for any process.

The Science of Bond Testing analyses the roots of bond testing and teaches what is required to design and perform the optimum bond test. When considering the optimum bond test there are a nearly infinite number of decisions to be made; these can be simplified into 4 parameters:

  • Test type
    • which type of test, pull or shear?
  • Test speed
    • what test speed?
  • Tool design
    • what is the best tool shape?
  • Tool alignment
    • where to apply the test load?

Find the Failure Modes of Interest

The test load must be applied to some part of the sample and transferred through the sample to the bond. If this part of the sample is the only option and is weaker than the bond itself, then it will fail. The bond will not be tested and the strength/quality will not be known. Ideally the bond test should produce some type of bond failure. This type of bond failure is known as the "Failure Mode of Interest".

A bond test is designed to produce the most Failure Modes of Interest by applying the test load most like the true load (if known) and with the highest force possible.

The Science of Bond Testing - how to design a bond test by getting the most failure modes of interestThe Science of Bond Testing - how to design a bond test by getting the most failure modes of interest (click on the image to zoom in)

You are testing with a load most like the true load (if it is known) and testing the bond at the highest force possible. This will give the earliest possible indication of a weakening in bond quality by a change in force and/or failure mode.

Example: Gold Ball Shear

In the case of Gold Ball Shear testing, the target failure mode is often Gold shear, because it indicates a reasonably good bond. But to know the bond strength the test should produce a failure in the IMC, a pad lift or pad crater. It should be noted that by changing the failure mode from Gold shear to a bond failure there will be a coresponding increase in the test force.

There are many different opinions on what the shear height should be, like for example 10% of ball height or a specific dimension. These may or may not be derived from an appropriate understanding but neither are the fundamental answer and both are capable of promoting a false truth. The best shear height is the one that produces the most Failure Modes of Interest. Similarly Gold ball shear is almost always tested with a Chisle Tool but a Cavity Tool will produce more Failure Modes of Interest and higher test forces.

The Science of Bond Testing states: Choose the test that gives the most Failure Modes of Interest using a test type most similar to the true loading condition (if it is known) and if you cannot get a Failure Mode of Interest, test the bond with the test settings that produce the highest load (force) on the bond.


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Other newsletters

Dec 2018 The Science of Bond Testing
Aug 2018 Is Fully Automatic Bond Testing Possible?
Jul 2017 Advances in Thin, 3D and MEMS Die Bond Strength Testing
May 2017 Shear testing copper pillar
Mar 2017 Fracture strength of thin wafers and die
Feb 2017 Centralized database for enhanced security and SPC options
Jan 2017 Full Automation with Improved Pattern Recognition, Fiducial Marks Analysis, Wire Detect and Failure Mode Analysis
Dec 2016 Coating and film testing
Nov 2016 Latest software release enables automatic grading
Oct 2016 Vision enhanced materials testing
Sep 2016 XYZTEC makes lid pull easy
Aug 2016 Condor Sigma W12 with large heater stage
Jul 2016 How to: Wire Pull
Jun 2016 Get 10% off your next tools order
May 2016 Pull testing bumped wafers
Apr 2016 SMD gull wing leads testing
Mar 2016 Automation: matrix bond testing made easy
Feb 2016 Fully integrated solution for automated wafer testing
Jan 2016 In bond testing, size does matter
Dec 2015 XYZTEC goes from strength to strength
Nov 2015 Automatic wire detect
Oct 2015 Highly reproducible stud pull tests are possible
Sep 2015 What is the quality of your coatings?
Aug 2015 Loading samples has never been so easy
Jul 2015 Axis accuracy of ±1µm: essential for automatic bond testing

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Bond testing seminars

Aiming to improve understanding of bond testing in the industry, XYZTEC organizes seminars to present and disseminate knowledge in a straightforward format. Click here to find out more about bond testing seminars.

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