Browse Prior Art Database

Localized Contamination Measurement System

IP.com Disclosure Number: IPCOM000038983D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Von Voss, WD: AUTHOR [+2]

Abstract

A method is described of extracting and measuring ionic contamination left around and under the small, compact Surface-Mounted Technology (SMT) components after the flux-cleaning/removal process. One of the important considerations for all circuit cards assembled is how well they have been cleaned. If the cards are not cleaned sufficiently, their reliability will be compromised. The small clearances under SMT components makes flux removal/cleaning difficult. Current contaminant measurement equipment utilizes a sizable quantity (>1 liter) of a deionized water and isopropyl alcohol solution to completely submerge an entire circuit card. As the solution dissolves the residual contamination from the card, a very dilute, slightly conductive solution is formed.

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Localized Contamination Measurement System

A method is described of extracting and measuring ionic contamination left around and under the small, compact Surface-Mounted Technology (SMT) components after the flux-cleaning/removal process. One of the important considerations for all circuit cards assembled is how well they have been cleaned. If the cards are not cleaned sufficiently, their reliability will be compromised. The small clearances under SMT components makes flux removal/cleaning difficult. Current contaminant measurement equipment utilizes a sizable quantity (>1 liter) of a deionized water and isopropyl alcohol solution to completely submerge an entire circuit card. As the solution dissolves the residual contamination from the card, a very dilute, slightly conductive solution is formed. The amount of contamination on the card is inferred from the conductivity of the solution; the very dilute solutions with low conductivity are difficult to measure accurately. The new method uses a small volume of solvent (50 cc) combined with strong agitation to dissolve all the residual contamination from around and under a single specific component, with the component still joined to the card. In general, the gentle agitation - soaking methods used by current contamination measuring systems do not effectively dissolve the residual contamination from assembled SMT or pin-in-hole cards. This method uses a "C" shaped frame, shown in Figs. 1 and 2, to clamp and seal a small solution cup over and around a single component on the assembled card. The size and shape of the cup is selected to fit the size and shape of the component. The opposing jaw of the clamp...