Improved Method for C-4 Chip Join
Original Publication Date: 1988-Nov-01
Included in the Prior Art Database: 2005-Feb-15
One known method of attaching a controlled collapse chip connector (C-4) decal to a chip is shown in Fig. 1. The C-4 decal 1 is a thin polyimide film held by a frame (not shown) which serves as a tool to transport the decal film through various processing steps. Starting with metallization (sucessive layers of chromium, copper and chromium) on one side, the first photo process defines a select image in which the top layer of chrome serves as a solder dam for the C-4 pads. A second photo process defines the circuit conductor lines 2. The decal 1 is now ready for attachment to the chip 3. The C-4 joints 4 and the outside decal connections (not shown) are solder joined to the substrate by solder balls 5. Because of the decal's flexibility, electrical shorting occasionally occurs, causing a defective module.