Method for attaching through-hole devices to a circuit board using solder paste

A process for attaching an electrical component having a plurality of electrical leads to a printed circuit board having a corresponding plurality of plated through-holes arranged in an array comprising one or more rows with each through-hole having a first end which opens to a first side of said circuit board and a second end which opens to a second side of said circuit board which process comprises:

• applying a layer of solder paste to cover the first ends of selected through-holes such that adjacent through-holes in the same row and opposing through-holes in adjoining rows of the array of through-holes are not both covered with solder paste;
• inserting the leads of an electrical component from the first side of the printed circuit board into the plated through-holes;
• heating the printed circuit board to a temperature and for a time sufficient to melt the solder paste;
• cooling the printed circuit board to a temperature below the melting point of the solder of the solder paste;
• applying a layer of solder paste to cover the second ends of the through-holes in the array of through-holes not covered with solder on their first ends;
• and,
• heating the printed circuit board to a temperature and for a time sufficient to melt the solder paste.

A process for attaching an electrical component having a plurality of electrical leads to a printed circuit board having a corresponding plurality of plated through-holes arranged in an array comprising one or more rows with each through-hole having a first end which opens to a first side of said circuit board and a second end which opens to a second side of said circuit board which process comprises:

• applying a layer of a first solder paste comprising solder having a higher melting point to cover the first ends of selected through-holes such that adjacent through-holes in the same row and opposing through-holes in adjoining rows of the array of through-holes are not both covered with solder paste;
• inserting the leads of an electrical component from the first side of the printed circuit board into the plated through-holes;
• heating the printed circuit board to a temperature and for a time sufficient to melt the solder comprising the first solder paste;
• cooling the printed circuit board to a temperature below the melting point of the solder of the first solder paste;
• applying a layer of a second solder paste comprising solder having a lower melting point to cover the second ends of the through-holes in the array of through-holes not covered with solder on their first ends;
• and,
• heating the printed circuit board to a temperature and for a time sufficient to melt the second solder paste but less than that required to melt the solder comprising the first solder paste.