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July 2000

Leadfree@IPC.ORG

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Subject:
From:
"Jen, Harry" <[log in to unmask]>
Reply To:
Leadfree Electronics Assembly E-Mail Forum.
Date:
Thu, 13 Jul 2000 07:56:38 -0400
Content-Type:
text/plain
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text/plain (62 lines)
In IPC-D-279 document "Design Guidelines for Reliable Surface Mount
Technology Printed Board Assemblies", page 22, it says that only gold,
silver and palladium should be used for finish if silver polymer is used.
The reason is other surface finish, even tin-lead, will form non-conductive
oxide and block the conduction path.  Silver oxide is conductive and gold
and palladium are quite noble.  Copper oxide, on the other hand, is not
conductive.  This is why a metallurgical bonding is required and silver
epoxy should not  be used on copper for more reliable process.

Hei-Ruey Harry Jen, Ph D
Principal Reliability Engineer
M/A-Com
1011 Pawtucket Blvd. G31
Lowell, MA 01854
[log in to unmask]
978-442-4804
978-442-4787 (FAX)

> -----Original Message-----
> From: James Canner [SMTP:[log in to unmask]]
> Sent: Wednesday, July 12, 2000 3:33 PM
> To:   [log in to unmask]
> Subject:      Re: [LF] lead free terminations
>
> There have already been a number of excellent responses, so I want to turn
> this around and consider the use of conductive polymeric terminations on
> passive devices.  How can they be attached to OSP copper board with out
> oxidation of the filler metal (usually silver ) and the circuit board
> metal
> usually copper.  It seems to me that each supplier is using what is
> necessary to make his product perform in usual application.  Therefore any
> new application method or material will possibly affect the total assembly
> process.
>
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