| 摘要 |
<p>PURPOSE: To prevent the leads of an electronic component from decreasing in soldering strength and separating off, even if the electronic component with the leads arranged at a narrow pitch and plated with Pb-containing solder is mounted. CONSTITUTION: The width of a solder 11, corresponding to a lead of the corner of a QFP chip or the width of an opening bored in a metal mask, is set larger than the width 0.2 to 0.4 mm of a land 4 by 0.1 to 0.25 mm, and the length of the opening of the metal mask is set larger than that of the land 14 by 0.1 to 0.2 mm. That is, the area of the opening provided to the metal mask, corresponding to the lead of the corner, is set larger than that of the land 14, by which solder paste filling the opening can be increased in volume. With this setup, the ratio of Pb to the total amount of solder used for soldering the lead can be reduced, even if the lead is plated with Pb-containing solder.</p> |
