Browse Prior Art Database

Chip Pad Process

IP.com Disclosure Number: IPCOM000122100D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 44K

Publishing Venue

IBM

Related People

Morin, W: AUTHOR [+3]

Abstract

A high density of small chrome, copper, gold, plus lead-tin solder (C4) pads are made by a lift-off process for chrome, copper and gold and by screening or injection filling vias with solder paste. High efficiency of placement of a tightly controlled quantity of solder at pads is one highly desirable result of this process.

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Chip Pad Process

      A high density of small chrome, copper, gold, plus lead-tin
solder (C4) pads are made by a lift-off process for chrome, copper
and gold and by screening or injection filling vias with solder
paste.  High efficiency of placement of a tightly controlled quantity
of solder at pads is one highly desirable result of this process.

      Referring to the figure, final circuit metal line 2 is formed
and covered by insulating passivation coating 4 over insulating
surface layer 6 on semiconductor substrate 8 by conventional
processing.  Then, polyimide 10 is deposited and cured.  Next, via
holes are defined and formed by reactive ion etching (RIE) through
both polyimide 10 and insulator 4.  Chrome- copper-gold, shown as
layer 12, is vacuum deposited conventionally.  Lift-off is performed
by means of tape removal after thermal softening of photoresist used
in the RIE process.  Via holes are filled with solder paste by a
squeegee process or by injection using an apparatus such as that
described in U.S. Patent 4,519,760. Then, heat treatment forms
durable solder 14 and alloys it with underlying gold and copper.  RIE
removal of some of polymide 10 may be performed to cause protrusion
of solder 10 above the surface, as shown.

      Variations in the described sequence of operations and/or use
of planarization at one or more points in the process may be used to
accomplish special results.

      Disclosed anonymously.