Start by having your ve
Yes all finishes can go off even gold.



Start by having your vendor supply in shrink vac sealed packs of X (we

use packs of 10).



Then implement a control policy for board stock on low runners. This is

the basics of ours:





In-house board stock older than 6 months:



5.1 Board stock older than 6 months but less than 12 months; process one

board from the stock as a solder sample per Section 4.



5.2 Board stock older than 12 months:

* HASL finish: process one board from stock as a solder sample per

Section 4

* ENIG finish: return boards to vendor for acid clean etch and rinse



5.3 Board stock older than 36 months: dispose of stock - requires

approval of Production Manager.



5.4 Board stock age to be determined from packaging receipt label, where

this is not available use date code on PCB.



5.5 Solder sample failures to be referred to Production Engineering. In

some circumstances it may be possible to rework HASL boards to

rejuvenate the surface finish - seek advice from vendor.







Although we have started using IAg finish for RoHS product we have not

yet added this into the process.



If the ENIG boards are in a sealed pack and have been stored under

reasonable conditions they should easily be good to 12 months and can be

easily rejuvenated by a pcb vendor.



We have processed HASL boards after 5 years which have sat in a fairly

closely controlled environment without having them re-HASL'd.





Regards,

 

Chris

 



-----Original Message-----

From: Leadfree [mailto:[log in to unmask]] On Behalf Of Phil Nutting

Sent: 28 April 2006 14:03

To: [log in to unmask]

Subject: [LF] Shelf life of circuit board plating



Good Friday Morning All,

 

This topic may have been previously discussed, but let me try to phrase

my "problem" completely so the answer can be simpler.

 

I have a board vendor (Fab house) stating that for my ENIG boards the

plating only has a 6 month shelf life if the package is opened.  Did I

miss something here?  I thought Gold doesn't tarnish.

 

If this is true, then Immersion Tin, Immersion Silver and ENIG all have

storage issues.

 

OK, so I open a sealed package and take out half of the boards in the

package.  I may not need the rest of the boards for many months.  So how

do I protect the unused boards?  Should I vacuum seal them?  Add a

desiccant?  If I add a desiccant, are there different desiccants which

might damage the boards?

 

I'm sure I'll have more questions right after I send this.

 

Phil



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