Browse Prior Art Database

Corrosion Free Lead (Pb) Rich Solder Bump

IP.com Disclosure Number: IPCOM000123582D
Original Publication Date: 1999-Jan-01
Included in the Prior Art Database: 2005-Apr-05
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Umemoto, K: AUTHOR [+3]

Abstract

Disclosed is a manufacturing process for Pb rich solder bump which is not corroded by dicing water used in the next dicing process. The material for Controlled Collapse Chip Connection (C4) bump is Pb rich with high melting temperature. But the material is usually corroded by water.

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Corrosion Free Lead (Pb) Rich Solder Bump

   Disclosed is a manufacturing process for Pb rich solder
bump which is not corroded by dicing water used in the next dicing
process.  The material for Controlled Collapse Chip Connection (C4)
bump is Pb rich with high melting temperature.  But the material is
usually corroded by water.

   This invention comprises a step for covering the C4 bump
surface with tin (Sn) rich thin layer in order to protect from
corrosion caused by the dicing water.

   Fig. 1 shows conventional C4 process flow from a step of
"reflow" to a step of "dice".  Sn rich thin layer is formed on the C4
surface during the reflow step.  Pb is exposed by flowing the Sn rich
thin layer out with flux during flux removing.  The exposed Pb is
dissolved with water during the step of dicing.

   Fig. 2 shows the developed C4 process flow.  C4 baking is
implemented before the dicing step.  Sn rich thin layer is reformed
in the C4 surface during a following baking step.  In the dicing
step, the C4 bump surface is not corroded because the Sn rich thin
layer protect the C4 bump from corrosion.

   Typical C4 baking operation process is following.
    Baking time                       :    20 a  30  min.
    Baking temp                       :   125 a 135  deg.
    Thickness of Sn rich thin layer   :    25  a 50  A