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Use of Wood on PCB Assembly Production floor ??

Ashok Dhawan

#4686

Use of Wood on PCB Assembly Production floor ?? | 9 March, 2000

I have a question (s) on ESD- all related to use of wood in a typical PCB Assembly line:

1. How a wooden mini stool if used for holding tote box ( card board with static protecive coat, black color) can affect static sensitive devices inside the tote box / shipping tubes/bags/ PCB assemblies parially bilt ? The wooden stool sits besides operators seat and operator is wearing wrist strap and attached to grounded table. The point of contension is : Wooden mini-table is coated with enamel paint. What kind of mini table / stool is used in general ? 2. To manual assembly, if woodem slide is used , can it affect components being hand inserted ? Wood is varnished but no enamel paint on this ? 3.For spot cleaning, if brushes with wooden handles are used ? What if bristles of brush are made of Nylon/plastic material ? - Assumption is that brush is soaked in solvent ISO-Propyl when used for cleaning. 4.For storage of Tape feeders on wooden stands -Partially used tapes carrying components on tape feeders. Can a wooden feeder stands affect ?

It might appear 4 questions in one, I will appreciate answers toching all aspects as mentioned above. Thanks in advance.

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#4687

Re: Use of Wood on PCB Assembly Production floor ?? | 9 March, 2000

Ashok: If I was to count, I'd guess there was more than 4 subquestions. Hey, but who's countin' anyway? I have answer (s) "on ESD all related to use of wood in a typical PCB Assembly line:"

Before pushing-on, it is only "a typical PCB Assembly line," if controlling your processes is NOT a priority.

|1. How a wooden mini stool if used for holding tote box ( card board with static protective coat, black color) can affect static sensitive devices inside the tote box / shipping tubes/bags/ PCB assemblies partially built ? The wooden stool sits besides operators seat and operator is wearing wrist strap and attached to grounded table. The point of contention is : Wooden mini-table is coated with enamel paint. What kind of mini table / stool is used in general ?

First, the wood construction has nothing to do with the ESD charging capabilities of your stool. (Put down those gloves, I am not bending over. No one get a look at my stool today!!!!;-)) The charge generation is developed between the coating on the surface of the stool and whatever dis-similar material is pushed/pulled/whatever across that surface. Varnish, enamel paint, who cares? They�re both insulators. Insulators do not dissipate charge. They store it!!!!

There�s a supplier of those stainless steel wire frame carts that varnishes the stainless. Why varnish stainless? "To make it more stainless of course!!!! You maroon!!!!" And to make it a ESD charge source. I�ve even seen those carts with drag chains. Talk about ... And then, some of those carts have those plastic "wedges" between the shelf and the vertical member (minds out of the gutter, yall!!!! ... I did that on purpose. ;-)) to make sure everything is isolated and very difficult to ground, even if it wasn�t coated. Or had rubber-like wheel covers. Not that I�m accusing Ashok of using those carts, I just drifted-off. ;-)

OK, I�m back. Second, operators� wrist straps, regardless of where they are connected, are totally ineffective for dissipating charges from insulators, such as the coating on your stool. You should do your level best to keep insulators from the production area.

Third, we prefer the conductive / connected to ground type mini-stool. Or if that is not available, the ESD dissipative mat connected to ground covered mini-stool. For those that you must allow, figure-out how to neutralize the charge.

|2. To manual assembly, if wooden slide is used , can it affect components being hand inserted ? Wood is varnished but no enamel paint on this ?

Yes. The friction from board / component / persons� clothing / whatever moving across the varnish generates a charge ... bzzzzap!!! Eeeeyow, that was a big one!!!!

|3.For spot cleaning, if brushes with wooden handles are used ? What if bristles of brush are made of Nylon/plastic material ? - Assumption is that brush is soaked in solvent ISO-Propyl when used for cleaning.

Well Ashok, that�s a bad assumption.

* Wood handles: If the wood is coated, go back to earlier comments. If the wood is not coated, it�s better than coated wood, but unfinished wood is difficult to control, because it�s turbocharging instincts vary as it absorbs moisture from the environment. * Nylon/plastic bristles: Yes, Walmart paint brushes are inexpensive. And Cascade will clean your boards. Hey!!! What about that guy here a coupla weeks ago that was cleaning his boards with Windex? * Brushes soaked in solvent: Have you ever watched one of your operators wipe dust from a board with a dry brush? If you have and he / she�s using their Walmart brush, your solvent argument is no good. If you haven�t, you�re not paying attention. All operators wipe-off their board, especially rework and touch-up (don�t get me started) types, when they finish with it. This happens beaucoup times a day.

Drifting-off again: What�s the deal on "spot cleaning?" Is anybody buyin� that "spot cleaning" is anything other than getting the flux into solution in the IPA and spreading it all over the board? I mean, how do you get the flux sodden IPA off the board? "Well Dave, you�re correct that the board is no cleaner than it would be if was never �cleaned,� but it sure looks a hellvalot better than having that big glob of flux sitting there burning a hole through the board to China." Yes, but what if your board fails and the plane goes down over Manhattan? Is anyone gonna buy that "looks nice theory?" Bla bla bla.

I know what you should do. Clean the IPA with Windex. Yeh, that�s da ticket!!!! Den we�ll clean the Windex with ... um er ... yeh Cascade!!!! Sorry, I�ll quit.

|4. For storage of Tape feeders on wooden stands -Partially used tapes carrying components on tape feeders. Can a wooden feeder stands affect ?

Yes, but of all the things we�ve discussed, this one makes me twitch the least.

Final advice: * Send the "whiny trouble maker" who is raising these questions to a ESD/EOS training course. Search the web. They�re fairly common. There�s "NEPCON West-like" convention for ESD-types every year. In fact coincidentally speaking Robin, er Ashok; the 22nd annual EOS/ESD Symposium is scheduled for September 26-28, 2000 at the Disneyland Hotel in Aneheim, CA. * Buy him / her Ted Dangelmayer�s book on ESD Program Management. It�s aimed at small to mid sized companies and referenced in the archives on SMTnet. * Get him / her to ESD/EOS society meetings. * Develop an ESD control program based on "ESD 20/20" (www.esda.org/pdf_files/s2020std.pdf) * And if you want to be gay and frivolous, buy the standards from ESD Association, 7900 Turin Rd Bldg. 3, Suite 2, Rome, NY 13440-2069 315-339-6937 Fax: 315-339-6793 www.eosesd.org eosesd@aol.com (Jack, by genetic predisposition, you�re exempt from this recommendation. Sorry, the McEwan�s didn�t help. ;-))

Finally, you didn�t ask about carrying assembled circuit cards on pieces of wood with slots cut in them so the cards would held at an angle to the bench. What�s the deal Ashok? Are you holding-out on us? ;-)

My2�

Dave F

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Nancy V

#4688

Re: Use of Wood on PCB Assembly Production floor ?? | 10 March, 2000

Dave,

Your response might have been helpful if you would have left off the extra, comical(?), comments. I am American and I still couldn't figure out what you were trying to say sometimes. Searching the web to find an ESD program and training seemed to be the best advice.

Good luck Ashok.

My 2 Cents Worth of Advice,

Nancy

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Boca

#4689

Re: Use of Wood on PCB Assembly Production floor ?? | 13 March, 2000

Dave,

Hey, don't mess with the slotted wood board racks, I worked for a shop that was totally commited to dem things! The focus was; they be CHEAP!

(You did get cryptic at times, I gots da same problem real often.)

Boca

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#4690

Nancy Boca, What??? | 14 March, 2000

Nancy & Boca: What did I say that was confusing, cryptic, uncomprehensible, whatever? Dave F

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