Drill comprised of hard metal for drilling contact holes in circuit boards and the like
US4231692A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 14, 1978 |
| Grant date | Nov 4, 1980 |
| Priority date | — |
| Expiry date | Sep 14, 1998 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T408/9097
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A hard metal drill is disclosed for drilling contact holes in multi-legend printed circuit boards formed of synthetic resin. The drill has a diameter of not more than 1.5 mm. and has main and secondary cutting edges and spiral-shaped flutes lying opposite the drill longitudinal axis. At least one of these edges has a different angle or a different legend with respect to a corresponding other edge. The amount of difference of the two cutting angles or lengths to be compared is selected such that a gap between the drill and an edge of the drill hole is at least 20 .mu.m and not more than 50 .mu.m. In order to produce such holes more readily, the two spiral-shaped flutes have different depths.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.