NDT of multicrystal electronics by impulse acoustic microscopy technique

It is shown that the method of pulsed acoustic microscopy can detect hidden defects in the multilayer crystal chips during the process of their build-up. The proposed methods allow identifying the adhesion defects at intercrystalline layer, defects of electrical contacts soldering, distribution and deformation of the heat-sinking layer (polyimide grid), and internal crystals cracks. The operating frequency of 50-100 MHz allows to perform acoustic imaging with a resolution of 30-50 mkm at the depth of two crystalline layers (2690 microns). Visualization of the structure at a greater depth is difficult because of the strong refractive index in silicon, and also because of the numerous internal structure elements forming the shadows in the images of the lower layers.