Equibiaxial Bend Testing of Silicon Wafer Material

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Equibiaxial Bend Testing of Silicon Wafer Material

Microprocessors are being added to products more and more every day. Mobile electronics and smartphones are everywhere. Processor chips are getting larger and thinner, while the products they are going into are getting thinner and more flexible. The silicon wafer material these processors are made of is brittle material. This means that microprocessor engineers need to do more and more mechanical testing of the silicon wafer materials and the processor chips to ensure these new products can hold up well in the varying dynamic environments of mobile product usage.

Bend tests are the most common type of mechanical test of silicon wafer materials. The simplest bend test of silicon wafer material or microprocessor component is a 3-point bend test. This type of test presents concentrated uniaxial bending stress at a specific location of interest on the material or product which is directly under the upper middle bend roller. 4-point bend testing provides uniform uniaxial bending stress over an area of interest on the test sample, which is the area between the upper bend rollers.

Some applications require knowledge of bending stress in more than one axis simultaneously. For example, when the owner of a large thin smartphone puts the phone their back pocket and sits on it. The pressure creates a complex multiaxial bending stress situation. Biaxial or multiaxial bending stress can be imposed on the silicon wafer material or processor component via the use of an equibiaxial bending stress fixture, commonly known as a ring-on-ring fixture.

The test fixture for the equibiaxial test consists of two compression platens, each with a circumferential ridge of different diameters. When each platen pushes on the test specimen, this creates an evenly distributed multiaxial bending stress region within the area of the smaller of the two circumferential ridges.

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