Criteria Labs has been providing void free die attach services since 2009 for demanding high power RF applications. High thermal CTE matched substrates include Copper Molybdenum (CuMo), tungsten and ultra high thermal conductivity diamond. Criteria Labs will design die attach tooling, develop the assembly process then provide process validation data. Void free die attach is possible for die sizes up to 18mm x 18mm.
Eutectic bonding of Au-backed MMIC (Monolithic Microwave Integrated Circuits) power amplifiers presents a unique challenge due to the thin, brittle nature of the device and the need for a virtually void free attachment of the backside of the device to CTE matched thermal spreader. Criteria Labs has developed advanced vacuum solder methods to achieve a void free die attach process.
The question is: how good is good enough? The concerns are more than just the total % of voids under the die but more specifically relate to where the voids are located (under power FET’s) and the size of the void which reduce the thermal conduction capability.
Flux-free vacuum soldering is used to form the void free eutectic bond. Graphite tooling is designed and fabricate to precisely hold the MMIC die in a place while the unit is exposed to various time/temperature/gas/vacuum profiles. Typical high thermally conductive substrates include copper molybdenum, tungsten and diamond substrates.
Void Free die attach can also be used for: