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Establishes a quantitative evaluation method on solder bridging in microsoldering using a printed wiring board with comb pattern conductors. Bridge tests were conducted by immersing the comb pattern board into a molten solder bath. The total length of solder bridge between conductors against the total length between conductors was measured as a measure of the occurrence of solder bridging. The occurrence of bridging depended on the number of immersions, flux activity including solid content, conductor spacing, solder bath temperature and solder composition. The increase in number of immersion enhanced bridging. The rosin flux without activators showed higher bridging than the activated flux. Sn‐37Pb solder showed lower bridging than Sn‐3.5Ag‐5Bi solder. Solder bridging was found to be closely correlated with wettability, therefore, the improvement of wettability could be effective to suppress solder bridging. The proposed method is believed to be suitable for the quantitative evaluation of solder bridging.

To determine the endurance of stainless steels used for wave soldering container materials in molten lead‐free solders.

A dissolution test on stainless steel wires in molten lead‐free solders was performed. The effects of the composition of the stainless steel, test period, and composition of the lead‐free solder on the dissolution rate were investigated. Dissolution was measured by cross‐sectioning the wires and measuring the reduction in radius.

The Sn‐Ag lead‐free solder showed faster dissolution than did the conventional Sn‐Pb eutectic. A severe dissolution rate was also observed for the Sn‐Zn system.

Quantitative data for the reaction rate between stainless steels and molten lead‐free solder is useful for the design of soldering machines and in planning their maintainance.

This paper shows the effect of basic factors on the dissolution rate of stainless steels in molten solder. It can give a basic understanding to engineers of the effect of lead free solders on wave soldering process equipment.

The dissolution rates of iron and alloyed steels in molten lead‐free solders were investigated in order to clarify the effect of erosion of iron plating on soldering iron tips. The dissolution rates of iron‐based alloys in lead‐free solders were found to be about three times greater than in conventional Sn‐Pb eutectics, indicating that the iron plating of a soldering iron tip is subjected to heavier damage when used with lead‐free rather than eutectic Sn‐Pb. Several steel alloys showed dissolution rates similar to that of pure iron, suggesting that compositional changes in the iron plating may have little influence on the erosion depth. Decreases in the reaction temperature and time, and a small addition of iron into the solder was found to be effective in suppressing both dissolution of iron wire and erosion of iron plating.