抄録
The solderability of electroless nickel-tungsten-phosphorus alloy films deposited from baths of caustic alkalin citrate (C-C) and of ammonia alkaline citrate (A-C) were studied using quantitative contact angle measurement of the solder ball.
Two kinds of solder balls, 60/40 (tin/lead), 1mm in diameter were used for solderability at 210°C. One is containing 2% resin and the other was dropped sufficent flux on it.
It was found that films deposited from the C-C baths provided improved solderability deteriorated when was dropped sufficient flux on them. In amorphous films, the greater the phosphorus content. Crystalline films with low phosphorus content deposited from A-C baths provided very good solderability with sufficient flux, but solderability was bad with solder balls containing 2% resin because of the formation of an oxide films.
The solderability of all films using solder balls containing 2% resin gradually deteriorated under heat-treatment in air at 200°C, but when sufficient flux was used there was no change whatever.
