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Subject:
From:
John Burke <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, John Burke <[log in to unmask]>
Date:
Wed, 10 Aug 2005 08:58:23 -0700
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text/plain (267 lines)
I have done this with a regular digital scale, you just have to use a large
board sample (10 - 20 - or a hundred depending on board size) to take
account of the scale last digit resolution.


------------------------------------
Avanex
John Burke
Senior Manager RoHS Compliance
[log in to unmask]
40919 Encyclopedia Circle
Fremont
CA 94538
tel: 510 897 4250
fax: 510 979 0189
mobile: 510 676 6312
------------------------------------


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Schaefer, Chris
Sent: Wednesday, August 10, 2005 8:49 AM
To: [log in to unmask]
Subject: Re: [TN] PCB Storage


Thank you... So do you know of a chemical cleaner that could be used in a
batch cleaner of other that could clean tin/ lead HASL plating? Oh and from
what I gather you use a precision scale to measure the suspect boards with
moisture versus boards that should not have any moisture - is this correct?
If true would the different materials used in manufacturing the boards and
the tolerances of weight +/- throw off your readings? or would it be so
minimal that it is not a factor?

Thank you for your help... Much appreciated

-----Original Message-----
From: Stadem, Richard [mailto:[log in to unmask]]
Sent: Wednesday, August 10, 2005 9:35 AM
To: TechNet E-Mail Forum; Schaefer, Chris
Subject: RE: [TN] PCB Storage


Get a copy of IPC-STD-030B. Read it. Read the part that says the bake
procedure is used to dry the board as well as the MSD components. Read
the part that says the times/temperatures are a guideline. Figure out
what temperature brings the moisture content down to less than 10%
(lease a precision scale) without sacrificing solderability (typically
105C for 8-12 hours depending on size and type). Perform a DOE to
determine what, if any, effect the baking has on solderability (DPMO
up?). Train the operators in proper handling for MSDs and PWBs in a
high-humidity environment. Get a McDry dessicator or two or three. Store
your boards and parts in them.
Baking of pwb's with ENIG finish to remove the moisture can cause the
nickel oxide layer (if present from poor plating processes) to become
worse. No way to tell except run a controlled lot and monitor the DPMO.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Schaefer, Chris
Sent: Wednesday, August 10, 2005 8:51 AM
To: [log in to unmask]
Subject: Re: [TN] PCB Storage

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
[log in to unmask]

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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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