Electroless deposits NiP and NiB were investigated for their feasibility as a diffusion barrier between solder and Al pad. Solder was selectively deposited on the aluminum pad by dipping. With the aid of scanning Auger microscopy (SAM) and X-ray diffraction (XRD), it was found that Ni3Sn4 is the only phase formed between the electroless NiP or NiB deposit and the solder after heat treatment. The phosphorus content of the electroless NiP deposit did not tend to affect the barrier performance of the deposit. However, the electroless NiB deposit is effective as a diffusion barrier only when the boron content is less than 3 wt.%. The tin of the solder can penetrate the electroless NiB layer at higher boron contents.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Metals and Alloys
- Materials Chemistry