X-Ray for defect detection in ceramic package substrates

With the development of GaN, SiC, AlN, and other third-generation semiconductor technologies, power devices have begun to develop rapidly in the fields of semiconductor lighting, power electronics, microwave RF, 5G communications, new energy, and new energy vehicles, as well as a surge in demand for the use of ceramic substrates.

In general, TPC, DBC and AMB ceramic substrates are only suitable for preparing single-sided circuit layers (or double-sided circuit layers, but the upper and lower layers are not conductive). If the upper and lower layers are to be connected, laser drilling (hole diameter usually greater than 200 μm) is required, followed by filling the holes with metal paste and then sintering. The metal layer in the hole has poor electrical and thermal conductivity and low substrate reliability. Integration means complexity in product inspection forms, so X-ray 3D tomography imaging can be used for package inspection of such electronic devices, and this inspection technique can effectively avoid image overlap and occlusion in highly integrated electronic devices.

DPC ceramic substrates use laser drilling and plated hole filling techniques to prepare through-hole metals. Since the holes are plated and filled with dense copper pillars, the electrical and thermal conductivity is excellent, thus enabling vertical interconnection of the circuit layers above and below the ceramic substrate.

The electrical properties of the ceramic substrate mainly refer to whether the metal layers in front and behind the substrate are conductive (good quality of the internal through-hole). Due to the small diameter of through-holes in DPC ceramic substrates, defects such as unfilled holes and vias may occur during the plating and hole filling process. Usually, quality checks can be performed using X-ray inspection equipment. the biggest advantage of X-ray non-destructive testing is that it is intuitive and fast.

Packaged IGBTs require X-ray non-destructive testing to identify and recognize defects in solder joints that may have occurred during the packaging process, thereby eliminating products with defects such as faulty soldering and solder leakage. With the continuous development of semiconductor technology, power devices will gradually develop in the direction of high power, miniaturization, integration, and multi-functionality. The performance of ceramic substrates used for packaging has also raised higher requirements, and their inspection has become more difficult.