Print circuit board product with stencil controlled fine pitch s

Details Print circuit board product with stencil controlled fine pitch s Print circuit board product with stencil controlled fine pitch s

1996-09-09

1998-10-20

Sparks, Donald

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

174261, 22818021, 22818022, 361760, 361774, H05K 103, H05K 109, H05K 111, H05K 702

Patent

active

058256296

ABSTRACT:
A product created through the reflow of low melting point solder on select contacts of a printed circuit board. In one form, the printed circuit board has fine pitch devices, including flip-chip integrated circuits, connected to a board having conventional coarse pitch surface. The fine pitch contacts of the board are exposed through holes in a stencil characterized in its ability to withstand solder reflow temperatures, not be wettable by solder, and have a coefficient of thermal expansion relatively matching the printed circuit board. Low temperature solder paste is screen deposited into the stencil openings. With the stencil fixedly positioned on the board, the solder paste retained by the stencil pattern is reflowed to selectively form on the underlying contacts of the printed circuit board. Thereafter, the stencil is removed from the board and the board is subject to previously practiced depositions of flux and paste in preparation for fine and coarse pitch component placement and ensuing solder reflow. The fine contact pitch and coarse contact pitch differ by nominal factor of two or more.

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