Patent ID: 6053394
Filing Date: 2000-04-25
Classification: B23K,H01L,H05K,Y02P

Abstract:
In a system for connecting a substrate having a low coefficient of thermal expansion to a printed circuit board having a materially higher coefficient of thermal expansion using an array of solder columns and reflow bonding, a method for supporting the substrate when under compression to effectuate heat sink contact with a structural element of the substrate, comprising the steps of:attaching an array of high melting temperature solder columns of first cross-sectional area to an array of electrically transmitting pads on the substrate;attaching a set of high melting temperature solder columns of second cross-sectional area, the second cross-sectional area exceeding the first by a factor of five or greater, to pads at perimeter locations of the substrate;reflowing low temperature solder to connect first and second cross-sectional area solder columns to respective pads on the printed circuit board; andconnecting by compressive thermal contact a heat sink to a structural element of the substrate on a side opposite the solder column attachments.