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Descriptive Plateau Profile Curve for Multi-Chip Rework

IP.com Disclosure Number: IPCOM000101654D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 70K

Publishing Venue

IBM

Related People

Wazni, W: AUTHOR

Abstract

Disclosed is a plateau temperature profile curve for multiple-chip site rework, using copper blocks to clean excess solder after chip removal from the substrate C4 microsockets.

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This is the abbreviated version, containing approximately 52% of the total text.

Descriptive Plateau Profile Curve for Multi-Chip Rework

       Disclosed is a plateau temperature profile curve for
multiple-chip site rework, using copper blocks to clean excess solder
after chip removal from the substrate C4 microsockets.

      The specified plateau curve setting is at 245 degrees
centigrade (+,-) 20 degrees centigrade for a dwell time of 4 minutes
(+) 3 minutes, (-) 2 minutes.

      One typical C4 solder ball composition is 97% lead and 3% tin.
The copper blocks utilized by this invention are 0.05 mm thick, and
are coated with two layers of 63% tin, 37% lead and 37% tin,
respectively.  The specified plateau curve allows a stabilization and
relaxing period in which the temperature of the substrate
microsockets are set equally just prior to the solder reflow.  The
temperature and time requirement for the solder reflow is usually
specified at 320 degrees centigrade to 365 degrees centigrade for a
period of 2 + 1 minute.

      Stabilizing the temperature prior to the solder reflow point
allows for high efficiency and uniformity in the solder removal
process.  The temperature variation between sites on the same
substrate through the furnace can be as much as 20 degrees
centigrade.  The plateau curve stabilizes the substrate temperature,
and brings the site temperatures to be more uniform across the
substrate prior to the reflow point, thereby cutting the peak
variation by at least 50%. The four-minute span of the copper block
tin/lead coating interaction with the excess solder on the C4
microsocket at a temp...