Browse Prior Art Database

MECHANICAL "UNIBODY" STIFFENER APPLIED TO HOT CHUCK WAFER PROBING

IP.com Disclosure Number: IPCOM000008357D
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2002-Jun-10
Document File: 6 page(s) / 369K

Publishing Venue

Motorola

Related People

Bill Williams: AUTHOR [+2]

Abstract

The increased use of bare die to obtain packaging efficiency has necessitated the development of wafer probe technologies to supply tested die for use in DCA (Direct Chip Attach) applications. Methods of wafer testing at elevated temperatures are being developed for die that will not be individ- ually packaged but instead used in DCA boards. Because these die will not be traditionally "final tested" at Hot-Cold-Ambient, they must be adequately stressed and tested during wafer probe. We have evaluated multiple probe card technologies at elevated temperatures for testing a wafer while it is being heated by a hot chuck in a wafer probing machine.

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Page 1 of 6

MO7VROLA Technical Developments

MECHANICAL "UNIBODY" STIFFENER APPLIED TO HOT CHUCK WAFER PROBING

by Bill Williams and Eddie Lorenzo-Luaces

INTRODUCTION

  The increased use of bare die to obtain packaging efficiency has necessitated the development of wafer probe technologies to supply tested die for use in DCA (Direct Chip Attach) applications. Methods of wafer testing at elevated temperatures are being developed for die that will not be individ- ually packaged but instead used in DCA boards. Because these die will not be traditionally "final tested" at Hot-Cold-Ambient, they must be adequately stressed and tested during wafer probe. We have evaluated multiple probe card technologies at elevated temperatures for testing a wafer while it is being heated by a hot chuck in a wafer probing machine.

  Requirements of testing at elevated tempera- tures, i.e. 85°C 110°C or 135°C and above, have caused numerous test problems. Large deformations of solder bumps or damaged aluminum bondpads from excessive probe needle scrub are two major issues. Probe card deflection measurements relative to wafer chuck temperatures were collected and the effects of the increased force caused by the deflected probe cards observed. A major design improvement, which was a key contribution to our hot chuck probing success, comes from the identification of the need for, and design of, a stiffener plate to support probe cards to stabi)ize thermally induced deflections. This paper presents the design and

development of the invention we call a Mechanical Unibody Stiffener for Hot Chuck Probe. This inven- tion is a new design that provides a method of adding a tool steel support fixture to minimize or eliminate probe card deflections during hot chuck wafer probe.

BACKGROUND

  Figure 1 is a simplified cross-section through a traditional Cobra card clamped into the 5971 TesteriKLA Prober interface area including the Pogo Interface Board (PIB) and the Pogo Ring. Electrical contact is provided from the tester via spring loaded Pogo pins to the top side of the Probe Interface Board. Between the PIB and the Cobra probe card assembly, resides the Pogo Ring. This ring contains hundreds of spring loaded pogo pins which provide the electrical contact from the PIB to the Cobra card. A clamping mechanism locks together to provide the large force necessary to compress the pogo pins and to also fixture the alignment between all of the components shown in the Figure 1. The free standing arrows on the clamp areas indicate the forces to oppose the pogo pin force arrow shown on the pogo ring. There is a metal ring, the Teradyne Card Ring in Figure 1, which attaches to the pogo pin side of the probe card at the clamped area to oppose the forces of the

pogo pins.

0 Motorola, I"E. ,997 I96 September I997

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MOlVR0l.A Technical Developments

C4 bumped wafer

Beam" Cobra Pro

IBM Cobra Card Assy

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Fig. 1 IBM Cobra probe card w...