Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Unique Pad Geometry for Optimum Solder Application

IP.com Disclosure Number: IPCOM000120900D
Original Publication Date: 1991-Jun-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Nguyen, DQ: AUTHOR [+4]

Abstract

Ordinarily, circuit pads designed for surface-mount and flip-chip attachment applications follow commonly known shapes of rectangles, squares or circles, all of them lined up along a row. However, when the pitch between the component leads or chip terminals approaches around 0.012", designing large enough pads that would hold adequate solder volume for reflow joining, poses severe problems with area availability on the carrier. This article provides a method for overcoming this problem via the use of diamond- and triangular-shaped pads.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 80% of the total text.

Unique Pad Geometry for Optimum Solder Application

      Ordinarily, circuit pads designed for surface-mount and
flip-chip attachment applications follow commonly known shapes of
rectangles, squares or circles, all of them lined up along a row.
However, when the pitch between the component leads or chip terminals
approaches around 0.012", designing large enough pads that would hold
adequate solder volume for reflow joining, poses severe problems with
area availability on the carrier.  This article provides a method for
overcoming this problem via the use of diamond- and triangular-shaped
pads.

      Shown in Fig. 1 is a design configuration suitable for
flip-chip bonding.  The design comprising of staggered diamonds or
rhombi, 0.010" on the side and 0.013" pitch can accommodate either a
chip terminal configuration of 0.005" diameter bumps on 0.013"
centers along a row, or two such rows on the chip separated 0.0085"
to 0.0115" apart.  In the former case, odd numbered terminals would
rest on the top half of the diamond and the evens would rest on the
bottom. In the latter case, all terminals would rest on the same half
of the diamond on account of the staggered terminal layout on the
chip itself.  In any case, a pad area of 87 square mils (0.001" x
0.001" = 1 square mil) is obtained, compared to around 50 square mils
achievable with a 0.008" diameter circular pad.  Use of a diamond
with 0.0012" on the side would provide 125 square mils of pad area.

      Fi...