Process of making pad structure for solder ball limiting metallurgy having reduced edge stress
US5376584A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 31, 1992 |
| Grant date | Dec 27, 1994 |
| Priority date | — |
| Expiry date | Dec 31, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05K2203/043
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
Abstract
A two-step masking process is disclosed for forming a ball limiting metallurgy (BLM) pad structure for a solder joint interconnection used between a support substrate and a semiconductor chip. A solder non-wettable layer and a solder wettable layer are deposited on the surface of a support substrate or semiconductor chip which are to be connected. A phased transition layer is deposited between the wettable and non-wettable layers. A thin photo-resist mask defines an area of the solder wettable and phased layers which are etched to form a raised, wettable frustum cone portion. A second mask is deposited on the surface of the support substrate or semiconductor chip, and has an opening concentrically positioned about the frustum cone. Solder is deposited in the opening and covers the frustum cone and the area about its periphery. When solidified, the solder, acting as a mask, is used to sub-etch the underlying solder non-wettable layer thereby defining the BLM pad. When reflowed, the solder beads away from the surface of the solder non-wettable layer to form a ball which securely adheres about the frustum cone.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.