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Eutectic Solder Preform for Solder Ball Connected Card Repairs

IP.com Disclosure Number: IPCOM000111386D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 67K

Publishing Venue

IBM

Related People

Foo, E: AUTHOR [+4]

Abstract

Disclosed is a preformed solder mesh tailored to fit the hole pattern pitch of a Solder Ball Connected (SBC) card, when replacing damaged or absent chips on an otherwise good card. Conventional repair techniques such as hand solder are not applicable with the chip face down and the site inaccessible to screen printing. Controlling the volume of solder at the rework site is difficult. This method is reliable and easy to control the quantity of applied solder in advanced SBC module rework. Benefits are the elimination of several process steps, reduced card waste, and testing time at each joint is guaranteed.

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Eutectic Solder Preform for Solder Ball Connected Card Repairs

      Disclosed is a preformed solder mesh tailored to fit the hole
pattern pitch of a Solder Ball Connected (SBC) card, when replacing
damaged or absent chips on an otherwise good card.   Conventional
repair techniques such as hand solder are not applicable with the
chip face down and the site inaccessible to screen printing.
Controlling the volume of solder at the rework site is difficult.
This method is reliable and easy to control the quantity of applied
solder in advanced SBC module rework.  Benefits are the elimination
of several process steps, reduced card waste, and testing time at
each joint is guaranteed.

      An SBC structure is shown in Fig 1.   A card 1 with via holes 2
connects to an MLC substrate 3 by SBC balls 4 and solder pads 5.
The problem is re-soldering solder points 5 on one small site under
the MLC 3 without disturbing the surrounding good card joints.

      The use of a eutectic solder preform Ring Grid Pattern shown in
Fig 2 is the key feature of the repair process.   The dimensions for
a 25 x 25 grid pattern are designed to to match different
requirements of pitch and pattern ball diameter and solder volume
required per site.  Also, it is applicable for other SMT components
such as Quad Flatpacks.

      When a faulty SBC module is to be repaired, it is removed from
the circuit card, the site is cleaned, and excess solder is removed.
New solder must be applied to the site to form reliable electrical
a...