Hello All,
Hope you are all having just a wonderful day in the land of Milk and Honey!
HELP PLEASE...
We are currently in a situation in which we have little to no control of the humidity or temperature within our facility, and probably never will. We also do not have complete compliance to our procedures from the board vendors - so we do not receive the boards as we would like them (MBBag, appropriate desiccant and volume of desiccant, HICard, solderability test results, and ionic or other cleanliness test results from each lot/ date code set). This will not change in the near future either due to the fact that we need the boards so desperately we accept almost anything. Internally we have little if any discipline when storing/ handling the boards so we are constantly baking boards and performing solderability tests (especially during the summer months). We try to keep all board packaged in an MBB with HICard with a maximum of 20 boards per bag (zip-lock), but still have humidity failures (We are in Kansas - currently 50-85%RH depending on the day). How should this be done properly? Most of the boards are Class 3 products and we are required to use 2% no-clean flux with most product, so it is difficult to solder anyways.
My first question is: Can you clean the tin/ lead HASL plating with a type of chemical to remove oxides so that we do not have to send the boards back to the vendor for cleaning or re-plating? If so what is the chemical? We have tried using A4512P (Kyzen product), but this does not work well. I have been told to get something with MEK in the mixture, but I don't know for sure.
My second question is: When I have Gold Immersion plated boards and they are found in the packaging to have a failed HICard, how do you remove the moisture in the board? I have read that baking this type of plating actually reduces the solderability of the board. Is this true?
Please HELP...
I appreciate any support I can get. Thank You.
Chris Schaefer
Suntron Corporation
Process Engineer
540 N. Rogers Road
Olathe, Kansas 66062
913.393.5878
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Joe Russeau
Sent: Tuesday, August 09, 2005 3:14 PM
To: [log in to unmask]
Subject: Re: [TN] PCB Storage
Hi Paul,
This is one of those "It Depends" questions.
Most of the studies I have read with respect to storage of tin-lead HASL
boards suggests a shelf life of up to twelve months. I have not seen any
studies for boards with that surface finish being stored for that extended
period of time (2 years). In my opinion, the ideal situation would be to
purchase the boards as you need them and eliminate the issues surrounding
extended storage. But since you already have the boards that is not an
option.
My 2 cents are to make sure that if you plan on storing them, that you
package for the long term (2 years) and not for the short term (6mos). I
would suggest vacuum packaging them in a clean, moisture and debris
resistant container (e.g. Kapak heat-sealable bag). Depending on how many
boards you have to store and their dimensions, it may be advisable to store
them in a dessicated environment after vacuum sealing them. Controlling the
humidity is going to be key to reducing the oxidation rate. Unless you use a
nitrogen blanket to store the boards, you will not eliminate oxidation, but
by controlling the humidity, you should be able to slow the process a bit.
It is hard to say what will happen after long term storage, but I would
suggest checking a few boards (provided you have extra) for solderability.
If the boards solder as you expect, then you may be safe to continue to
assembly. If you have problems, you may want to consider a mild saponified
wash to remove any oxidation or debris that has accumulated from storage and
repeat the solderability. Best of luck!
Joe Russeau
Process Analyst
Precision Analytical Laboratory, Inc.
4106 Cartwright Dr. Ste. A
Kokomo, IN 46902
P: 765-455-1993
F: 765-455-1996
E: [log in to unmask]
----- Original Message -----
From: "Black, Paul" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, August 09, 2005 2:31 PM
Subject: [TN] PCB Storage
> Hi All,
>
> I have some bare PC boards that may be built up in the future, but not in
the near future. I would like to put them into storage until needed
(anywhere from 6 months to 2 years). The boards are .062" FR-4 HASL boards.
What would you recommend for protection, assuming that the storage
conditions are typical of an office environment? Would I have to do anything
special to them when they are removed from storage? Any suggestions would be
greatly appreciated.
>
> Thank you,
> Paul Black
> Manufacturing Engineer
> Kronos
> E-mail: [log in to unmask]
>
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