Browse Prior Art Database

Micro-Soldering Method for Die Bumping/Die Attach

IP.com Disclosure Number: IPCOM000120914D
Original Publication Date: 1991-Jun-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 38K

Publishing Venue

IBM

Related People

Gutierrez, BL: AUTHOR [+2]

Abstract

There is disclosed a universal, rapid, low-cost method for forming solder bumps on chips (die). These bumps have a solder volume of approximate 15-60 mils3 . They are formed by applying individual particles of solder to a pre-fluxed die, then optionally reflowing the solder using standard reflow equipment. The solder particles are uniform spheres of tightly controlled diameter (volume) and are readily available from typical solder powder production.

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Micro-Soldering Method for Die Bumping/Die Attach

      There is disclosed a universal, rapid, low-cost method for
forming solder bumps on chips (die).  These bumps have a solder
volume of approximate 15-60 mils3 .  They are formed by applying
individual particles of solder to a pre-fluxed die, then optionally
reflowing the solder using standard reflow equipment.  The solder
particles are uniform spheres of tightly controlled diameter (volume)
and are readily available from typical solder powder production.

      PROCESS STEPS
1.   Apply a tacky flux to surface of pads to be bumped.
2.   Place solder particles on die.  Solder may be, for example, tin,
tin/lead, tin/antimony, tin/bismuth, or tin/gold.
3.   (Optional) reflow solder to form solder bump on die using
conventional reflow method appropriate for solder alloy and flux
choices.  If solder is not reflowed, flux should be dried as to
remove volatiles, so powder is securely held.
4.   Attach die to carrier, placing on pre-fluxed carrier with
solder-coated or metallized pads and reflow.

      This process may be used to prepare chips for TAB inner lead
bonding (ILB) or for direct chip attach.  It has been found that
solder particles of 0.002" - 0.005" diameter give the desired volume
for pad sizes of 0.002" - 0.004" diameter on the chip.

      Disclosed anonymously.