Verify a novel surface finish for PCB assemblies and assess the reliability of these assemblies and related soldering processes

 

The need to obtain better performance in telecom and RF applications requires the use of novel PCB surface finishes, such as NiPdAu (e.g. ENEPIG). Currently the European space community has limited knowledge and understanding of the manufacturing and reliability issues associated with these surface finishes.

Three PCB surface finishes with substantial commercial experience and market share are currently available: ENIG (Electroless Nickel Immersion Gold), ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold) and ENIPIG (Electroless Nickel Immersion Palladium Immersion Gold). The interconnect behaviour of all three surface finish depends on layer build up, surface cleanliness, process bath chemistry, chemical and thermal stability and pad geometry. The challenge is to find out failure root causes, to develop and investigate process technologies and to improve the process reliability.

The selected NiAu based surface finish shall be assessed in order to provide the needed surface planarity for soldering of HDI packages and for improved performance for high speed signals (e.g. above 6.25 Gbps) and RF functionality. In addition, the suitability of the selected surface finish for Cu wire bonding shall be assessed. Additional benefit of the NiAu based surface would be the avoidance of lead on the PCB (comply with the RoHS 2 directive 2011/65/EU) needed for enabling lead-free solder connections.

During this activity the contractor shall

- Perform a literature survey and define lessons-learned

- Establish in-process controls and coupon tests to monitor the quality of the selected surface finish

- Design a PCB test vehicle enabling to perform the required tests representative of the highest technological complexity under evaluation and test until failure (end of life)

- Establish test methods and assess the reliability under thermal and mechanical load as well as RF performance (in telecom environment) of the surface finish for assembly by soldering and for Cu wire bonding

- Compare ENIG/ENEPIG/ENIPIG chemistries, PCB manufacturers and provide recommendations for future use in space applications