CCGA

CCGA (also called CGA) Column Grid Array IC packages are made with non-collapsible solder columns for surface mount soldering on printed circuit boards (PCB). Most CCGA packages have large ceramic substrates 21mm to 52.5mm. It is noteworthy to mention that there is increasing interest in replacing solder balls on (organic) Plastic Ball Grid Arrays (PBGA) with solder columns. CCGA packages are typically 1.0mm or 1.27mm pitch. Experimentation suggests the feasibility to use solder columns for narrower pitch CCGA packages down to 0.8mm and eventually smaller pitches.

Solder columns absorb CTE mismatch between the IC package and the PCB circuit board. CTE mismatch is inherent due to joining different material properties between the IC package and the PCB circuit board. The CTE mismatch differential between a ceramic IC package and PCB circuit board is 10ppm/°C in the X/Y axis. CTE mismatch rises above 50ppm/°C in the Z-axis as temperatures exceed the Tg rating of the PCB circuit board. As the IC package increases in size, the differentials of CTE mismatch become more significant, especially when the package is subjected to repeatedly wide temperature cycles from -40°C to +125°C.

Stress due to CTE mismatch results in eventual delamination and catastrophic electrical failure between a large ceramic BGA IC package and the PCB circuit board. The corner pads are most prone to fail as well as the corners directly under the silicon die mounted on (or in) the package.

Solder columns (nominally 2.2mm long) shown on the ceramic package in Figure 1 provide more compliancy than solder balls to reduce stress caused by CTE mismatch. Tall solder columns absorb stress and increase solder joint reliability under harsh operating conditions.