How to screw up a PCB in one easy step - Page 1
Forum section: electronics / general

author: IO390
author_rank: Regular Contributor
timestamp: August 09, 2014, 08:26:48 pm
content: 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.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 09, 2014, 08:56:55 pm
content: 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...

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 09, 2014, 09:08:31 pm
content: But hey, the ceramic caps are still good!..Tim

author: IO390
author_rank: Regular Contributor
timestamp: August 09, 2014, 09:17:23 pm
content: Quote from: mikeselectricstuff on August 09, 2014, 08:56:55 pmWell the thing is I forgot, but it was at least 10 minutes. Probably more like 15.

author: c4757p
author_rank: Super Contributor
timestamp: August 09, 2014, 09:48:38 pm
content: Quote from: IO390 on August 09, 2014, 09:17:23 pmTen minutes?!?!On the bright side, the nuclear reflow oven test is a success! Just need to tweak the run time or power level...

author: Psi
author_rank: Super Contributor
timestamp: August 09, 2014, 09:52:27 pm
content: clean it off, see if it still works. Just for kicks

author: rob77
author_rank: Super Contributor
timestamp: August 09, 2014, 09:54:57 pm
content: Quote from: T3sl4co1l on August 09, 2014, 09:08:31 pmi'm sure one could find a working silicon die somewhere in that black goo

author: rs20
author_rank: Super Contributor
timestamp: August 10, 2014, 01:14:26 am
content: Quote from: rob77 on August 09, 2014, 09:54:57 pmWait, are you telling me thisisn'thow they make those chip-under-black-goo calculator PCBs!?!?

author: RyanAMT
author_rank: Contributor
timestamp: August 10, 2014, 02:33:29 am
content: Did you at least taste it?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 10, 2014, 02:55:23 am
content: Quote from: RyanAMT on August 10, 2014, 02:33:29 amBet it tastes at least as good as "drunk passing out" style frozen pizzaTim

author: SeanB
author_rank: Super Contributor
timestamp: August 10, 2014, 06:55:22 am
content: 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.

author: VK3DRB
author_rank: Super Contributor
timestamp: August 10, 2014, 09:10:53 am
content: 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.

author: tszaboo
author_rank: Super Contributor
timestamp: August 10, 2014, 10:08:50 am
content: OK Google... set alarm for 5 minutes.

author: Zbig
author_rank: Frequent Contributor
timestamp: August 10, 2014, 11:15:40 am
content: So, electronic circuits run on magic smoke AND magic epoxy? Oh boy, just when I thought I finally began to grasp it...

author: IO390
author_rank: Regular Contributor
timestamp: August 10, 2014, 12:15:51 pm
content: Quote from: Psi on August 09, 2014, 09:52:27 pmTried that. It doesn't.Quote from: VK3DRB on August 10, 2014, 09:10:53 amYeah, 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.Quote from: T3sl4co1l on August 10, 2014, 02:55:23 amI once attempted to make fried eggs whilst drunk. This tasted about the same.

author: sunnyhighway
author_rank: Frequent Contributor
timestamp: August 10, 2014, 07:26:13 pm
content: Seems like a perfect way to protect your design from reverse engineering......

author: SirNick
author_rank: Frequent Contributor
timestamp: August 11, 2014, 09:15:06 am
content: Sooo... what exactlywasthat 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.

author: IO390
author_rank: Regular Contributor
timestamp: August 11, 2014, 10:22:28 am
content: Quote from: SirNick on August 11, 2014, 09:15:06 amThat was the soldermask

author: Yago
author_rank: Frequent Contributor
timestamp: August 11, 2014, 10:26:55 am
content: Quote from: IO390 on August 10, 2014, 12:15:51 pmHehe, indeed you may have reinvented the game Partick Roulette :p

author: SeanB
author_rank: Super Contributor
timestamp: August 11, 2014, 05:40:27 pm
content: 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.