Self-cleaning mold
US4741507A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 20, 1987 |
| Grant date | May 3, 1988 |
| Priority date | — |
| Expiry date | Aug 20, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01L2924/0002
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
The formation of flash during plastic encapsulation of electronic devices may be reduced or eliminated and the mold made substantially self-cleaning by modifying the mold chases so that the edges of the channels, runners, gates, and/or other locations containing plastic have a wedge shaped edge region extending to the parting plane of the mold. The wedge angle is desirably in the range 15-30 degrees, measured with respect to the parting plane. The length of the wedge should be sufficient to provide for heating of the thermosetting plastic flowing therein, with about 0.05 inches (1.3 mm) being useful for typical dual-in-line, surface mount, flat pack, or other types of semiconductor device and integrated circuit package molds. The plastic flowing into the wedges shaped region solidifies more rapidly than the plastic in the main channel, thereby damming the wedge to prevent flash formation at the mold parting line at the edges of the plastic containing regions. A method for using the mold to encapsulate electronic devices is described. Mold wear is substantially reduced.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.