Browse Prior Art Database

Chromium Solder Masks for Flex and Rigid PCB

IP.com Disclosure Number: IPCOM000115575D
Original Publication Date: 1995-May-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Appelt, B: AUTHOR [+3]

Abstract

This article describes a modified process for producing a chromium solder mask for printed circuit cards or boards.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 53% of the total text.

Chromium Solder Masks for Flex and Rigid PCB

      This article describes a modified process for producing a
chromium solder mask for printed circuit cards or boards.

      When producing printed circuit cards or boards, a solder mask
is produced in a photolithographic step.  A polymer film (e.g.,
probimer) having a thickness of about 40 &mu.m is exposed and
developed.  The part of the polymer which has not been removed now
forms a closed wall around the soldered joints.  This wall, in turn,
prevents bridging of the solder material to adjoining soldered joints
in the subsequent solder process and also prevents flowing of the
solder material along the pattern.

      The technology of future printed circuit cards or boards using
Direct Chip Attach (DCA), however, calls for essentially finer
arrangement of soldered joints at the positions where the chip
contacts the PCB.  The conventional photolithographic process
described above can only be applied for forming standard solder
masks, since on the one hand the resolution of the optics used is not
sufficient for the necessary structuring, and, on the other hand, the
granularity of the photopolymer is too great.

      Contrary to the photographic treatment of the polymeric
material by means of photo masks and the granularity of the light-
sensitive photosensitizer, no thick photo resist, but a high-
resolution commercially available photo-plating film can be used when
applying a chrome mask.  Thereby the e...