SOLDER CONNECTING METHOD FOR FINE PITCH PADS TO COMPONENT LEADS

摘要

PURPOSE: To improve an external appearance and to improve connecting reliability by using lead-rich precoating solder as to obtain a desired solder alloy composition resulting from fusion with tin and tin alloy plated on component leads. ;CONSTITUTION: In order to form solder for finally connecting component leads to pads to alloy composition (normally eutectic alloy) as a target, it is effective to use lead-rich precoating solder on the pad. The lead content in the solder is decided by considering sizes of component leads 1 and pads 2 and plated thickness of the leads. Thus, a quantity of a plating material of the lead and a quantity of the precoating solder are obtained. The composition of the precoating solder is so decided that the final connecting solder becomes a desired composition. When a substitution of organic acid lead salt with tine is utilized. even if the composition of the precoating solder is made constant, the composition of the final connecting solder can be controlled.;COPYRIGHT: (C)1994,JPO&Japio