Author Topic: How to screw up a PCB in one easy step  (Read 7197 times)

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Offline IO390

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How to screw up a PCB in one easy step
« on: August 09, 2014, 08:26:48 pm »
Easy! Leave it in the oven...

I've been reflowing PCBs for a while with a toaster oven. I just slowly heat/cool the board and I've had no issues.

That is, unless you stick a board in the oven and then fucking walk off and forget about it.

I came back to the lab and saw a load of smoke coming out of the oven and thought "oh blast", or words to that effect. Nothing went too badly considering, but my lab stinks now.  :palm:
 

Offline mikeselectricstuff

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Re: How to screw up a PCB in one easy step
« Reply #1 on: August 09, 2014, 08:56:55 pm »
How long did this take...?

I've over-reflowed a board for 7 mins instead of the normal 3-4 and the only issue was a discoloured silkscreen.

I now use the original timer on the oven as a failsafe - must get round to adding an automatic occasional reminder beep while cooking and a "go look at it NOW" alarm...
 
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Offline T3sl4co1l

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Re: How to screw up a PCB in one easy step
« Reply #2 on: August 09, 2014, 09:08:31 pm »
But hey, the ceramic caps are still good!.. ::)

Tim
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Offline IO390

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Re: How to screw up a PCB in one easy step
« Reply #3 on: August 09, 2014, 09:17:23 pm »
How long did this take...?

Well the thing is I forgot, but it was at least 10 minutes. Probably more like 15.
 

Offline c4757p

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Re: How to screw up a PCB in one easy step
« Reply #4 on: August 09, 2014, 09:48:38 pm »
Well the thing is I forgot, but it was at least 10 minutes. Probably more like 15.

Ten minutes?!?!

On the bright side, the nuclear reflow oven test is a success! Just need to tweak the run time or power level...
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Offline Psi

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Re: How to screw up a PCB in one easy step
« Reply #5 on: August 09, 2014, 09:52:27 pm »
clean it off, see if it still works.  Just for kicks
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Offline rob77

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Re: How to screw up a PCB in one easy step
« Reply #6 on: August 09, 2014, 09:54:57 pm »
But hey, the ceramic caps are still good!.. ::)

Tim

i'm sure one could find a working silicon die somewhere in that black goo  :-DD
 

Offline rs20

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Re: How to screw up a PCB in one easy step
« Reply #7 on: August 10, 2014, 01:14:26 am »
But hey, the ceramic caps are still good!.. ::)

Tim

i'm sure one could find a working silicon die somewhere in that black goo  :-DD

Wait, are you telling me this isn't how they make those chip-under-black-goo calculator PCBs!?!?  :P
 

Offline RyanAMT

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Re: How to screw up a PCB in one easy step
« Reply #8 on: August 10, 2014, 02:33:29 am »
Did you at least taste it?  ;D
 

Offline T3sl4co1l

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Re: How to screw up a PCB in one easy step
« Reply #9 on: August 10, 2014, 02:55:23 am »
Did you at least taste it?  ;D

Bet it tastes at least as good as "drunk passing out" style frozen pizza :)

Tim
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Offline SeanB

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Re: How to screw up a PCB in one easy step
« Reply #10 on: August 10, 2014, 06:55:22 am »
Take one of the caps, solder a wire on each end and measure every day to see how the ceramic behaves with time, seeing as it is now in an "As new" state fresh from sintering.

You can reuse the inductors though after rewinding them.
 

Offline VK3DRB

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Re: How to screw up a PCB in one easy step
« Reply #11 on: August 10, 2014, 09:10:53 am »
Hopefully you evacuated the home and opened all the doors and windows to de-fume the place for safety reasons.

It is likely there were toxic fumes in the kitchen. PCB assemblies usually have high levels of bromides, used as flame retardants. They are carcinogenic. At IBM, if one printed circuit board was "cooked" in one of the reflow ovens, the plant was evacuated and de-fumigated.
 

Offline NANDBlog

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Re: How to screw up a PCB in one easy step
« Reply #12 on: August 10, 2014, 10:08:50 am »
OK Google... set alarm for 5 minutes.
 

Offline Zbig

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Re: How to screw up a PCB in one easy step
« Reply #13 on: August 10, 2014, 11:15:40 am »
So, electronic circuits run on magic smoke AND magic epoxy? Oh boy, just when I thought I finally began to grasp it... :-//
 

Offline IO390

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Re: How to screw up a PCB in one easy step
« Reply #14 on: August 10, 2014, 12:15:51 pm »
clean it off, see if it still works.  Just for kicks

Tried that. It doesn't.

Hopefully you evacuated the home and opened all the doors and windows to de-fume the place for safety reasons.

Yeah, took the whole oven outside before opening it too. I've got one of those high voltage air fresheners so I left that on for a few hours. Seemed to clear it up.

Did you at least taste it?  ;D

Bet it tastes at least as good as "drunk passing out" style frozen pizza :)

Tim

I once attempted to make fried eggs whilst drunk. This tasted about the same.
 

Offline sunnyhighway

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Re: How to screw up a PCB in one easy step
« Reply #15 on: August 10, 2014, 07:26:13 pm »
Seems like a perfect way to protect your design from reverse engineering......  >:D
 

Offline SirNick

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Re: How to screw up a PCB in one easy step
« Reply #16 on: August 11, 2014, 09:15:06 am »
Sooo... what exactly was that puddle of black goo?  Electrolytic caps?  Just wondering what disintegrated that spectacularly in a dozen minutes.

BTW, I love it when people post this kind of stuff.  There's something therapeutic about getting to laugh at each other's mistakes.  :-+
 

Offline IO390

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Re: How to screw up a PCB in one easy step
« Reply #17 on: August 11, 2014, 10:22:28 am »
Sooo... what exactly was that puddle of black goo?  Electrolytic caps?

That was the soldermask  :-DD
 

Offline Yago

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Re: How to screw up a PCB in one easy step
« Reply #18 on: August 11, 2014, 10:26:55 am »
clean it off, see if it still works.  Just for kicks

Tried that. It doesn't.

Hopefully you evacuated the home and opened all the doors and windows to de-fume the place for safety reasons.

Yeah, took the whole oven outside before opening it too. I've got one of those high voltage air fresheners so I left that on for a few hours. Seemed to clear it up.

Did you at least taste it?  ;D

Bet it tastes at least as good as "drunk passing out" style frozen pizza :)

Tim

I once attempted to make fried eggs whilst drunk. This tasted about the same.

Hehe, indeed you may have reinvented the game Partick Roulette :p
 

Offline SeanB

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Re: How to screw up a PCB in one easy step
« Reply #19 on: August 11, 2014, 05:40:27 pm »
Reminds me of getting aircraft computers into the shop, and getting that CBB smell even though it was sealed in a plastic bag, closed in a box and hermetically sealed with 84 screws on the 2 covers ( yes I did invest in an electric screwdriver to undo those 84 hex cap screws after a month, and had to buy new gearsets for it as well after a year, which was great as Black and Decker ( now known as Blows and Dumpem) still kept spares and sold them for a very reasonable cost) and then removing the top to see the black goo spread over 3 cards where the fan manfully moved it until the mains fuses ( 3A) finally popped. Still have the paper of the cost of the new power supplies, never seen so many numbers in a price before, and that was an each price. Platinum was cheaper.
 


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