Method to achieve robust solder bump height
US6486054B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jan 28, 2002 |
| Grant date | Nov 26, 2002 |
| Priority date | — |
| Expiry date | Jan 28, 2022 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01L2924/14
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
Abstract
The present invention teaches how greater solder ball height can be achieved without the need to sacrifice areal density. The mold in which the solder is formed, is created in two steps. In a first exposure, a negative photoresist (preferably DFR) is patterned to form a conventional cylindrical mold. However, exposure and development time are adjusted in such a way that a layer of unexposed and undeveloped resist of reduced thickness remains covering the floor of the mold. This residual resist layer is given a second exposure and, after development, forms an annular insert in the bottom of the first mold. After the mold has been filled with solder (either through electroplating or by using solder paste) it is removed, the result being a solder bump made up of two contiguous coaxial cylinders the upper one having the larger diameter. After remelt, bumps having this shape form oblate spheroids rather than spheres.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.