Importance

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Abstract

An improved vapor phase soldering machine includes a pair of separate vessels having an open fluid communication path in a wall separating the two vessels. The first vessel contains a liquid mixture of a primary vapor and a secondary vapor, while the second vessel contains a liquid mixture of the primary vapor and a tertiary vapor. Heating means continuously boils the two mixtures to create corresponding vapors within the vessels. The secondary vapor is disposed on top of the primary vapor in the first vessel, while the tertiary vapor is disposed on top of the primary vapor in the second vessel. The printed circuit board with surface mounted devices attached thereto by solder paste is introduced into the secondary vapor of the first vessel for preheating the board and the devices. Then, the board is moved into the primary vapor which is at a temperature high enough to melt the solder paste, thereby forming a bond between the devices and the printed circuit board. Then the circuit board is routed through the opening in the wall separating the two vessels and into the primary vapor of the second vessel and then into the tertiary vapor within the second vessel. The tertiary vapor is held at, near or below ambient temperature to provide rapid cooling and hardening of the soldered connections.

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First Claim