Browse Prior Art Database

Organometallic Lead Finish for Tape Automated Bonding

IP.com Disclosure Number: IPCOM000037458D
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Nguyen, DQ: AUTHOR [+2]

Abstract

Tape automated bonding (TAB) device leads are either tin plated or gold plated to enhance solderability to the substrate. Tin plating on the leads is susceptible to whisker growth, and gold plating can cause joint embrittlement depending upon the initial gold thickness on the leads, the solder volume, and the number of repairs experienced.

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Organometallic Lead Finish for Tape Automated Bonding

Tape automated bonding (TAB) device leads are either tin plated or gold plated to enhance solderability to the substrate. Tin plating on the leads is susceptible to whisker growth, and gold plating can cause joint embrittlement depending upon the initial gold thickness on the leads, the solder volume, and the number of repairs experienced.

The method described eliminates the use of tin and gold as the lead surface finish materials while retaining solderability. TAB device leads are precleaned with dilute sodium or potassium persulfate solutions, dilute hydrochloric acid, followed by a treatment of dilute sodium carbonate solution. The leads are then treated with dilute solutions of known heterocyclic organic compounds such as benzotriazole, imidazoles, etc. at about 50oC. The copper on the leads forms a thin layer of organometallic compound that acts as a barrier to the corrosive elements in the ambient. During soldering operation, the organometallic complexes volatilize or decompose at interconnection temperature on reaction with flux, and leave behind fresh copper surface for joint formation.

The advantages of this method include elimination of gold/tin plating and associated costs, longer shelf life, elimination of tin whisker growth, gold embrittlement, and a reliable solder joint.

Disclosed anonymously.

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