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Identification of defective Package Ball Connectors

IP.com Disclosure Number: IPCOM000126652D
Original Publication Date: 2005-Aug-25
Included in the Prior Art Database: 2005-Aug-25
Document File: 2 page(s) / 313K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

In current DRAM manufacturing, several problems with quality of FBGA (Fine Ball-Grid Array) based memory modules are due to defective package balls. These are highly resistive and very hard to find efficiently by test measures since the functionality of DRAM modules may be given under test conditions but may later fail in application due to additional thermal and/or mechanical stress. Today, DRAM modules go through excessive test procedures at multiple temperatures and even that does not guarantee the complete detection of resistive solder balls. A new idea means to implement an on chip circuitry for direct comparison of two balls. That allows effective testing for resistive differences between these balls. On chip, a defined capacitance will be discharged on the pad connected to the ball regarded. A similar capacitance will be discharged on a reference pad/ball. This results in an initial raise of the pad potential which will discharge over time through the related ball. Length of the discharging process depends on the ball resistance. A comparison of pad voltage and reference pad voltage by e.g. a sense amplifier allows detection of ball resistance differences.

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Identification of defective Package Ball Connectors

Idea: Peter Poechmueller, DE-Munich

In current DRAM manufacturing, several problems with quality of FBGA (Fine Ball-Grid Array) based memory modules are due to defective package balls. These are highly resistive and very hard to find efficiently by test measures since the functionality of DRAM modules may be given under test conditions but may later fail in application due to additional thermal and/or mechanical stress. Today, DRAM modules go through excessive test procedures at multiple temperatures and even that does not guarantee the complete detection of resistive solder balls.

A new idea means to implement an on chip circuitry for direct comparison of two balls. That allows effective testing for resistive differences between these balls. On chip, a defined capacitance will be discharged on the pad connected to the ball regarded. A similar capacitance will be discharged on a reference pad/ball. This results in an initial raise of the pad potential which will discharge over time through the related ball. Length of the discharging process depends on the ball resistance. A comparison of pad voltage and reference pad voltage by e.g. a sense amplifier allows detection of ball resistance differences.

A scheme of the idea is shown in Fig. 1. Two similarly sized capacitors (3) are discharged on pad 2 that is connected to a ball and a reference pad 1 that is connected to a reference resistance.

Other approaches to...