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larryp
Joined: 24 Jan 2012
Posts: 252
Location: eden prairie mn
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 Link Posted: Thu Jun 01, 2017 9:41 pm Post subject: Handling a Circuit Board |
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I'm going to be putting in a new circuit board, and wondering if I need to ground anything or myself?
How do you guys handle them?
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jbltecnicspro
Joined: 23 Apr 2016
Posts: 512
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| Link Posted: Thu Jun 01, 2017 11:07 pm Post subject: |
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I lick some of the capacitors with my tongue to give them a taste test first as you can tell how much life is left by their taste.
I'm just kidding. I don't do anything special. Just pick them up by their edges, making sure my hands don't come into contact with the underside of any large caps. I haven't grounded myself in... Forever. Maybe I should?
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Tim in Phoenix
Joined: 21 Oct 2006
Posts: 4378
Location: Phoenix
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| Link Posted: Fri Jun 02, 2017 12:47 am Post subject: |
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Hello
If your new board did not arrive in an anti-static bag, find a new supplier. Touch the chassis of the machine with the anti-static bag just before installing.
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24301
Location: Langley, BC
TV/Projector: All of them!
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| Link Posted: Fri Jun 02, 2017 2:00 am Post subject: |
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No, you don't need to do anything. Once static sensitive parts are installed in a PC board, it's virtually impossible to kill them with static electricity.
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jbltecnicspro
Joined: 23 Apr 2016
Posts: 512
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| Link Posted: Mon Jun 05, 2017 9:37 pm Post subject: |
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| Curt Palme wrote: | | No, you don't need to do anything. Once static sensitive parts are installed in a PC board, it's virtually impossible to kill them with static electricity. |
So did my computer servicing instructor lie to me then when he made us wear grounding straps all the time? Or are PCB's different?
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24301
Location: Langley, BC
TV/Projector: All of them!
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| Link Posted: Mon Jun 05, 2017 11:02 pm Post subject: |
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For raw chips, yes, it's mandatory, but we were told in college that once a chip is inserted to a board, the components around it create resistance between the various pins, effectively giving a short circuit to any static hitting any pin. Also, the immunity to static on current chips is far greater than it was in the 1970s.
Put it this way: For manufacturing, it's mandatory for people dealing with stuffing PC boards. An ex g/f gave me a tour of a small PC board manufacturing facility in January, and I went to pick up a stuffed board, and she freaked. (no static sensitive chips on the board I was about to pick up). She gave me crap, saying that there's no way I'd be able to pick up a board without a ground strap on. Point taken.
In the 45 or so years I've dealt with all sorts of chips, I've never worn a ground strap, and have never blown up a chip due to static. Smoking chips because I didn't find the secondary fault that caused the chip to blow in the first place.. yeah, I've done that! 
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mp20748
Joined: 12 Sep 2006
Posts: 5681
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Link Posted: Tue Jun 06, 2017 7:45 am Post subject: |
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| Curt Palme wrote: | | In the 45 or so years I've dealt with all sorts of chips, I've never worn a ground strap, and have never blown up a chip due to static. Smoking chips because I didn't find the secondary fault that caused the chip to blow in the first place.. yeah, I've done that! |
About the same time here, with me only finding one IC that actually was static sensitive. Don't remember what is was but it was a real flake and based later discoveries and experiences, it was most likely a poorly designed chip that unlike the 99.9% of all other manufactured chips, any need for protection was included inside the chip itself.
On everything else, the use of ground straps and special pads etc, were totally a waste of time. Much like trying to understand to use of Static Bags for boards..
I think the logic behind this is the sensitivity known of the CMOS device that's so common in chip design. This was solved when they put shock-diodes directly inside the chips on almost every pin of the chip. The same is true on all the common op-amp and other not so known to be static sensitive chips. And according to the data sheets from the top chip manufacturers, they all have been using these diodes included in the chips themselves. So maybe at some point years back, static could have been problem. But as Curt pointed out, the past 45 years or so, my experience says this static thing is a hoax at best.
And several years back, one of the chip manufactures if you ordered just standard Op Amps from them, they would come in huge special aluminum and other special packaging. Three video IC's could come in a box that was two feet long, that was maybe 4 inches wide...you open the box and there was a special aluminum looking plastic air shrunk casing...you get out the scissors and cut open the special air-tight xray protect looking cover...inside you would pull out this long SOIC plastic storage piece...with there being only three IC's at one end of the long plastic casing.
Now the IC's come in a very small and static looking bag.
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jbltecnicspro
Joined: 23 Apr 2016
Posts: 512
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| Link Posted: Tue Jun 06, 2017 11:59 am Post subject: |
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Good to know. Thanks for the input guys! I guess for computers the only raw chips we're handling are probably the CPU's. Other than that, they're all PCB's.
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24301
Location: Langley, BC
TV/Projector: All of them!
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| Link Posted: Tue Jun 06, 2017 1:54 pm Post subject: |
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I won't go as far as saying it's a hoax, I believe that every manufacturer still does it, I am just speaking from a practical point. BTW, my shop in winter is full of static electricity with no issues.
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cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
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| Link Posted: Tue Jun 06, 2017 2:16 pm Post subject: |
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Any commercial repair shop or any circuit manufacturer will use grounding systems just as a precaution. It may not really be necessary but it's cheap insurance in an industry where the cost of repairing a static-damaged board can be quite high.
They want to avoid any possibility of CAUSING static damage.
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larryp
Joined: 24 Jan 2012
Posts: 252
Location: eden prairie mn
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| Link Posted: Wed Jun 07, 2017 9:02 pm Post subject: |
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Replaced my board without any explosions or meltdowns.  )
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