Jinghui Industry Ltd.
At present, the main inspection of finished ceramic substrate cover the visual inspection, mechanical properties inspection, thermal properties inspection, electrical properties inspection, packaging properties (working performance) checking and reliability inspection.
The appearance inspection of ceramic substrates is regularly conducted by visual or optical microscopy, mainly including cracks, holes, scratches on surface of the metal layer, peeling, stains and other quality defects. In addition, the outline size of the substrates, the thickness of the metal layer, the warpage (camber) of the substrates, and the graphic accuracy of the substrate surface are needed to be tested. Especially for the use of flip-chip bonding, high-density packaging, the surface warpage is generally required to be less than 0.3% of dimensions.
In recent years, with the continuous development of computer technology and image processing technology, manufacturing labor costs continue to rise, almost all manufacturers pay more and more attention to the application of artificial intelligence and machine vision technology in the transformation and upgrading of the manufacturing industry, and the detection methods and equipment based on machine vision have gradually become an important means to improve product quality and improve the yield. Therefore, the application of machine vision inspection equipment to the detection of ceramic substrate can improve the detection efficiency and reduce the labor cost accordingly.
The mechanical properties of the ceramic substrate mainly refer to the bonding force of metal wire layer, indicating the bonding strength between the metal layer and the ceramic substrate, which directly determines the quality of the subsequent device package (solid strength and reliability, etc.). The bonding strength of ceramic substrates prepared by different methods is quite different, and the planar ceramic substrates prepared by high temperature process (such as TPC, DBC, etc.) are usually connected by chemical bonds between the metal layer and the ceramic substrate, and the bonding strength is high. In the ceramic substrate prepared by low temperature process (such as DPC substrate), the van der Waals force and mechanical bite force between the metal layer and the ceramic substrate are mainly, and the binding strength is low.
Test methods for Ceramic metallization strength onto substrate include:
1) Tape method: the tape is close to the surface of the metal layer, and the rubber roller is rolled on it to remove the bubbles in the bonding surface. After 10 seconds, pull the tape off with a tension perpendicular to the metal layer, and test whether the metal layer is removed from the substrate. Tape method is a qualitative test method.
2)Welding wire method: Select a metal wire with a diameter of 0.5mm or 1.0mm, weld directly on the metal layer of the substrate through solder melting, and then measure the pulling force of the metal wire along the vertical direction with a tension meter.
3)Peel strength method: The metal layer on the surface of the ceramic substrate is etched (cut) into 5mm~10mm strips, and then torn off in the vertical direction on the peel strength testing machine to test its peel strength. The stripping speed is required to be 50mm/min and the measurement frequency is 10 times /s.
The thermal properties of ceramic substrate mainly include thermal conductivity, heat resistance, thermal expansion coefficient and thermal resistance. Ceramic substrate mainly plays a heat dissipation role in device packaging, so its thermal conductivity is an important technical index. The heat resistance mainly tests whether the ceramic substrate is warped and deformed at high temperatures, whether the surface metal line layer is oxidized and discolored, foaming or delaminating, and whether the internal through hole fails.
The thermal conductivity of the ceramic substrate is not only related to the material thermal conductivity of the ceramic substrate (body thermal resistance), but also closely related to the interface bonding of the material (interface contact thermal resistance). Therefore, the thermal resistance tester (which can measure the body thermal resistance and interface thermal resistance of multi-layer structure) can effectively evaluate the thermal conductivity of ceramic substrate.
The electrical performance of the ceramic substrate mainly refers to whether the metal layer on the front and back of the substrate is conductive (whether the quality of the internal through hole is good). Due to the small diameter of the through hole of the DPC ceramic substrate, there will be defects such as unfilled, porosity and so on when filling holes in electroplating, X-ray tester (qualitative, rapid) and flying needle tester (quantitative, cheap) can generally be used to evaluate the through hole quality of the ceramic substrate.
The packaging performance of ceramic substrate mainly refers to weldability and air tightness (limited to three-dimensional ceramic substrate). In order to improve the bonding strength of the lead wire, a layer of metal with good welding performance such as Au or Ag is generally electroplated or electroplated on the surface of the metal layer of the ceramic substrate (especially the welding pad) to prevent oxidation and improve the bonding quality of the lead wire. Weldability is generally measured by aluminum wire welding machines and tension meters.
The chip is mounted on the 3D ceramic substrate cavity, and the cavity is sealed with a cover plate (metal or glass) to realize the airtight package of the device. The air tightness of the dam material and the welding material directly determines the air tightness of the device package, and the air tightness of the three-dimensional ceramic substrate prepared by different methods is different. The three dimensional ceramic substrate is mainly used to test the air tightness of the dam material and structure, and the main methods are fluorine gas bubble and helium mass spectrometer.
Reliability mainly tests the performance changes of ceramic substrate in a specific environment (high temperature, low temperature, high humidity, radiation, corrosion, high frequency vibration, etc.), including heat resistance, high temperature storage, high temperature cycle, thermal shock, corrosion resistance, corrosion resistance, high frequency vibration, etc. The failure samples can be analyzed by scanning electron microscopy (SEM) and X-ray diffractometer (XRD). Scanning sound microscope (SAM) and X-Ray detector (X-ray) were used to analyze welding interfaces and defects.
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