Removal of metal skin from a copper-Invar-copper laminate
US6228246A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 1, 1999 |
| Grant date | May 8, 2001 |
| Priority date | — |
| Expiry date | Jul 1, 2019 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05K2203/0361
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A method of removing a metal skin from a through-hole surface of a copper-Invar-copper (CIC) laminate without causing differential etchback of the laminate. The metal skin includes debris deposited on the through-hole surface as the through hole is being formed by laser or mechanical drilling of a substrate that includes the laminate as an inner plane. Removing the metal skin combines electrochemical polishing (ECP) with ultrasonics. ECP dissolves the metal skin in an acid solution, while ultrasonics agitates and circulates the acid solution to sweep the metal skin out of the through hole. ECP is activated when a pulse power supply is turned on and generates a periodic voltage pulse from a pulse power supply whose positive terminal is coupled to the laminate and whose negative terminal is coupled to a conductive cathode. After the metal skin is removed, the laminate is differentially etched such that the copper is etched at a faster rate than the Invar. To prevent the differential etching, a copper layer is formed on a surface of the substrate with an electrical resistance R.sub.1 between the copper layer and the positive terminal of the pulse power supply. Additionally, an electri…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.