Technique for Measuring C4 Height
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
In a controlled collapse chip connection (C4) process, joining is achieved by reflowing the solder bumps (C4 joints) on a chip placed on tinned or untinned Cu pads on a substrate. The height of the C4 joints has an important impact on the thermal fatigue life of C4 joints because it is inversely proportional to the thermal strain during a thermal cycle. However, once a chip is joined to a substrate, it is difficult to measure the height of the C4s accurately and conveniently. This disclosure describes a new technique for measuring the height of C4s joined to ceramic cards.