Browse Prior Art Database

Method of Reworking Electronic Cards or Circuit Surfaces using Polymer Thick Films and Tin Lead

IP.com Disclosure Number: IPCOM000104672D
Original Publication Date: 1993-May-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Duncan, SA: AUTHOR

Abstract

Disclosed is a method for connecting two or more electrically conductive areas on an electronic card or circuit surface using polymer thick films to both insulate and define a conductive path on an existing card or circuit being reworked. As seen in the accompanying figure, in STEP 1, an insulating Thick Film Polymer soldermask is deposited over the copper via pads or land tracks (B,C,D) over which the new electrical connection will be traversed. This soldermask is used as a dielectric to insulate the existing copper electrical connections from the new layer of solderable nickel or copper polymer deposited in STEP 2. This solderable metal polymer is silkscreened over the soldermask in order to electrically connect the two via pads or land tracks A and E being connected.

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Method of Reworking Electronic Cards or Circuit Surfaces using Polymer Thick Films and Tin Lead

      Disclosed is a method for connecting two or more electrically
conductive areas on an electronic card or circuit surface using
polymer thick films to both insulate and define a conductive path on
an existing card or circuit being reworked.  As seen in the
accompanying figure, in STEP 1, an insulating Thick Film Polymer
soldermask is deposited over the copper via pads or land tracks
(B,C,D) over which the new electrical connection will be traversed.
This soldermask is used as a dielectric to insulate the existing
copper electrical connections from the new layer of solderable nickel
or copper polymer deposited in STEP 2.  This solderable metal polymer
is silkscreened over the soldermask in order to electrically connect
the two via pads or land tracks A and E being connected.  As shown in
STEP 3, SnPb plating would be fused onto the copper polymer during
the solder paste deposition for the copper component side, or wave
soldering would fuse the SnPb on the circuit side assembly for PIH
components.  Tin lead is used to compensate for the high resistivity
of the copper polymer and to complete the electrical connection
between the two via pads or land tracks being connected.

      This method is similar to the IBM Polymer Thick
Film-Engineering Change (PTF-EC) method.  However, this method only
requires two masks and thus two passes whereas the PTF-EC method
requires...