Browse Prior Art Database

Solder Bump Formation with Anti-Erosion Polyimide Brim

IP.com Disclosure Number: IPCOM000106336D
Original Publication Date: 1993-Oct-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Kan, Y: AUTHOR [+3]

Abstract

Disclosed is a simple and effective process to form solder bumps with polyimide brim structure. The polyimide brim prevents penetration or diffusion of tin in solder into PLM (Pad Limited Metal) during bonding or reflow step and improves reliability of the solder joint.

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Solder Bump Formation with Anti-Erosion Polyimide Brim

      Disclosed is a simple and effective process to form solder
bumps with polyimide brim structure.  The polyimide brim prevents
penetration or diffusion of tin in solder into PLM (Pad Limited
Metal) during bonding or reflow step and improves reliability of the
solder joint.

      In Fig. 1, the PLM layer 3 is blanket deposited on polyimide
layer 2 formed on chip 1.  The polyimide 2 has a contact opening.
Second polyimide layer 4 is deposited on the PLM 3 and patterned by
photoprocess so that a selected region of the PLM layer 3 is exposed.
Then, Pb/Sn solder 5 (Fig. 2), e.g., high melting point solder, is
deposited by electroplating with the polyimide layer 4 being used as
a plating mask.  The polyimide layer 4 and PLM 3 are etched using the
deposited solder as an etching mask (Fig. 3).  The PLM layer 3 is
preferably etched by ion beam milling.  Finally, the solder is
reflowed (Fig. 4).  The PLM 3 may be etched after the solder reflow
using the polyimide layer 3 as an etching mask.

      In chip bonding process, the chip 1 may be bonded to a
substrate by Sn-rich low melting point solder.  The polyimde brim
prevents molten solder from creeping to the side edge of the PLM
structure during the bonding or solder reflow.  Therefore, erosion of
the PLM by Sn can be prevented.