Reworkable Engineering Change Pad Metallurgy
Original Publication Date: 1983-Oct-01
Included in the Prior Art Database: 2005-Feb-07
This process uses a relatively thin Au layer on the engineering change pad, which reduces the cost of the pad and the cost of fabrication. High density modern semiconductor packaging technology utilizes engineering change pads on the surface of multi-device substrates, as disclosed in U.S. Patent 3,968,193. These pads are conventionally formed by screening a refractory base pad, sintering, and subsequently depositing a Ni layer, followed by electroplating a heavy Au layer with a thickness in the range of 9-12 mm. These pads are costly because of the Au content and the complex steps necessary to selectively electroplate the Au. In this process a Ni layer is deposited on the screened refractory pad, as described previously, but only a thin Au layer, of a thickness on the order of 3 mm, is deposited on the Ni layer.