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Method to rework silver sulfide corroded resistors

IP.com Disclosure Number: IPCOM000250312D
Publication Date: 2017-Jun-27
Document File: 1 page(s) / 17K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed are methods to rework the silver sulfide layer formed on corroded resistors to either enable their reuse, or to increase the life of the component and assembly that the resistors are apart of. The methods involve exposing the silver sulfide layers to aluminum in an electrolyte solution. A chemical reaction will occur where the silver sulfide is converted back to pure silver and the aluminum forms aluminum sulfide.

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Method to rework silver sulfide corroded resistorsDisclosed are methods to rework the silver sulfide layer formed on corroded resistors to either

enable their reuse, or to increase the life of the component and assembly that the resistors are a

part of. The methods involve exposing the silver sulfide layers to aluminum in an electrolyte

solution. A chemical reaction will occur where the silver sulfide is converted back to pure silver

and the aluminum forms aluminum sulfide.

The formation of silver sulfide (Ag2S) on resistors in environments with sulfur-bearing gases

can cause the resistors to fail. In order to reverse the formation of Ag2S and restore the function

of the resistor, the resistor can be exposed to aluminum following the chemical reaction below:

Ag2S(s) + Al(s) => Ag(s) +Al2S3(s). The chemical reaction will occur when taking place in an

electrolyte solution. An example electrolyte solution is NaCl and NaHCO3 in water. The

reaction can also occur with copper, instead of aluminum; however, an external voltage source is

required to drive the reaction due to the higher nobility of copper on the galvanic series. [*] To

implement this rework process, several methods could be employed:

1) Full card/partially depopulated card assemblies are exposed to the electrolyte solution. An

aluminum-containing probe then comes into contact with the corroded components triggering the

chemical reaction.

2) A unique probe design is deployed which contains the electrolyte in discrete regions on the

card assembly. The probe also contains an aluminum component which will come into contact

with the corroded components, triggering the chemical rea...