Method and apparatus for forming fine patterns on printed circuit board
US5834160A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 16, 1996 |
| Grant date | Nov 10, 1998 |
| Priority date | — |
| Expiry date | Jan 16, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05K3/0082
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
The present inventors have discovered that fine patterns of metal or insulator can be formed on printed circuit board using conventional lithographic steppers with inverted projection lenses. The inverted projection lenses act as enlargement lenses rather than reducing lenses and exhibit a large depth of focus sufficient to accommodate the deviations of PC board from planarity. The inverted lens reduces the size of the image needed at the mask, permitting multiple mask levels to be combined on a single glass. This reduces the cost of the mask set and permits the use of smaller glass masks having greater accuracy and dimensional stability than the convention mylar masks used for PC board. By inverting the projection lenses on near-obsolete steppers, applicants were able to form metal patterns on PC board of finer dimension than heretofore reported. Inverting a 5.times. ZEISS lens on a GCA 6300A stepper, applicants were able to form vias of less than 25 .mu.m diameter, pattern metal lines and spaces of less than 25 .mu.m, and obtain overlay registration accuracy of less than 25 .mu.m. The field size was larger than 1 in.sup.2, and the depth of focus was greater than 50 .mu.m.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.