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Process and Jig for Electroplating Pin Grid Arrays without Defects Caused by Electrical Contact Areas

IP.com Disclosure Number: IPCOM000117510D
Original Publication Date: 1996-Mar-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 115K

Publishing Venue

IBM

Related People

Boecker, J: AUTHOR

Abstract

In the case of Pin Grid Arrays (PGAs) on which very high requirements are imposed in subsequent use, it is not possible to dispense with goldplating the visible, exposed conductor tracks and the connecting pins. This plating is carried out chemically or, preferably, by electrodeposition. For the electrodepostion of gold or other metals like nickel from corresponding metal salt baths, an electrical contact is essential between all the areas to be plated and the cathode.

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Process and Jig for Electroplating Pin Grid Arrays without Defects
Caused by Electrical Contact Areas

      In the case of Pin Grid Arrays (PGAs) on which very high
requirements are imposed in subsequent use, it is not possible to
dispense with goldplating the visible, exposed conductor tracks and
the connecting pins.  This plating is carried out chemically or,
preferably, by electrodeposition.  For the electrodepostion of gold
or other metals like nickel from corresponding metal salt baths, an
electrical contact is essential between all the areas to be plated
and the cathode.

      A considerable hazard in electroplating is that electrical
contact has to be made to all areas to be plated.  All kinds of
electrical contacts, such as metal needles or seed layers, have the
disadvantage of generating non-plated areas at the contact points.
Due to the fact that all contact pins are electrically circuited with
corresponding wire bond pads an electro-plating process in two steps
is carried out avoiding any plating defects caused by electrical
contact areas.

      In the first step, the pins serve as electrical contact to
electroplate the wirebond-pads, the die-area and the sealband of the
PGA which are electrically connected to ground.  To avoid undesired
extraneous plating on the pins itself, the pins are sealed to the
plating solution.  In the second step the current is supplied via the
wirebond-pads to electroplate the pins.  In both steps the electrical
supply is achieved by a stamp of conductive silicon rubber, which is
before molded from a PGA.  In order to prevent electroplating on the
contact areas and on the conductive silicon rubber the contacting
stamp is encapsulated in non-conductive silicon rubber which serves
as isolation and additionally as sealing material.

      To set an example, the production of the two needed contact
stamps for a cavity substrat...