Browse Prior Art Database

Solder Ball Connect Design with Improved Reliability

IP.com Disclosure Number: IPCOM000112140D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 4 page(s) / 60K

Publishing Venue

IBM

Related People

Corbin, JS: AUTHOR [+2]

Abstract

Disclosed is an enhanced SBC configuration which provides improved fatigue reliability and ease of assembly.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 86% of the total text.

Solder Ball Connect Design with Improved Reliability

      Disclosed is an enhanced SBC configuration which provides
improved fatigue reliability and ease of assembly.

      Solder Ball Connect (SBC) is an area array surface mount
attachment technology in which a solder-bumped ceramic chip carrier
is attached to an FR-4 card containing other surface mount and/or
pin-thru-hole components (Fig. 1).  The SBC module (Fig. 2) has a
full array of solder terminal connections instead of leads as in
conventional surface mount technology.  These solder terminal
connections consist of a .035 inch diameter high-temperature-melt
solder (90%Pb/10%Sn) ball which is attached to both the module and
card with eutectic (63%Pb/37%Sn) solder fillets.

      Because of the coefficient of thermal expansion mismatch
between the module and card, the solder ball joints experience a
shearing strain during power cycling of the device.  Some axial
strain is also present due to bending of the module-card assembly,
again due to the thermal expansion mismatch.  These deformation modes
are most pronounced at the corners where the
distance-to-neutral-point is a maximum.  Hence, the corner solder
ball joints are most susceptible to fatigue failure.

      The SBC design proposed herein uses corner pins instead of
balls (Fig. 3), which are soldered into through-holes in the card.
These pins provide improved mechanical coupling between the card and
the module, and inhibit the expansion/co...