Home » KnowledgeCenter » Pull tests » Cold bump pull (CBP)
CBP stands for Cold Bump Pull or Cold Ball Pull. To grip a ball we have to reform it to the shape something like a mushroom. This is done with special tweezer jaws that have cavities that reform the ball when they close. If we get a higher test force by “over gripping” the ball so that the reforming cuts over the bond this is better than a lower force with a ductile or extrusion where the bond was still not tested but at a lower force.
Ideally, the “stem” of the mushroom shape is the larger or the same diameter as the bond but if over gripping tests the bond at a higher force, it is a better test. We might still get a ductile or extrusion when we over grip, but the bond has been tested to the highest force possible.
Cold bump pull testing with the xyztec USB Tweezers provides unparalleled precision and control. The bond of many solder balls is at the bottom of a cavity formed by the solder resist layer. In a shear test, this supports the bond, resulting in a predominance of solder shear failure modes.
In a pull test, the bond is not supported in this fashion, leading to more relevant failure modes. Special jaws are required to grip the ball. This reform the upper part of the ball to enable the pull load to be applied without disturbing the bond.
We aim to spread knowledge about bond testing in the industry. That is why we have an extensive “how-to” on Cold Bump Pull (CBP) on our website.
During use, solder builds up in the cavity in cold bump pull (CBP) jaws. This reduces their grip efficiency and affects the quality of your measurements. Cleaning the cavities is very difficult and small ball cavities can be damaged easily.
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