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|Properties and Reliability of Silicon Nitride Substrates with AMB Copper Conductor|
|Keywords: silicon nitride, copper, reliability|
|This paper focuses on the properties of Si3N4 substrate material with AMB (active metal brazing) Copper Conductor. A recently developed type of tape cast, gas pressure sintered Silicon Nitride ceramic exhibiting a thermal conductivity three times higher than that of typical Silicon Nitride materials and with good flexural strength was used. The increase in thermal conductivity is the result of using different types of sintering aids as well as optimizing their content in the material. The high bending strength allows for the design of thinner substrates compared to other typical power electronics ceramic materials such as Aluminum Nitride. This thickness reduction leads to a decrease of the total substrate thermal resistance which improves the heat dissipation. For the AMB process a silver based active brazing solder optimized for Silicon Nitride was used. This optimization was achieved thanks to an investigation of the physical and chemical interactions between the brazing and the base materials. A void free joint without defect between adjacent structures was produced. The copper surface can be coated on request with Nickel or Nickel/Gold alloys for improved solderability and wire bondability as well as for corrosion protection. Tests results according to MIL-STD. 883G will be presented. The Silicon Nitride substrate with AMB Copper Conductor lines and fully plated back side ground shows a higher reliability than comparable substrates made out of typical ceramic materials. The heat dissipation is comparable to that of conventional AMB substrates made of high thermal conductive ceramic such as Aluminum Nitride, but the thermal cycling behavior easily surpasses the limits reached with AlN-AMB or AlN-DCB. The paper highlights the advantages of the Si3N4/copper material combination. The following physical data will also be presented: Si3N4 material, copper conductor, electrical values as well as the results of thermal cycling, solderability and bondability .|
|Ina Sichert, R&D Engineer