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no solder mask! — Parallax Forums

no solder mask!

lardomlardom Posts: 1,659
edited 2010-05-29 02:54 in General Discussion
I feel pretty dumb. I ordered ExpressPCB miniboards without solder mask and did not realize how difficult it would be to solder through-hole components without creating solder bridges to the ground plane... When I made the decision to go without solder mask I·only considered that·I wouldn't have problems bridging the pins of DIP components. Please, does anyone have any tips? I don't mind trashing the current board.

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Comments

  • mctriviamctrivia Posts: 3,772
    edited 2010-05-28 14:50
    you can buy solder mask pens. I use MG Chemicals 4190-GP

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    Lots of propeller based products in stock at affordable prices.
  • Erik FriesenErik Friesen Posts: 1,071
    edited 2010-05-28 14:50
    Go to the nearest radio shack and get some solder braid.
  • RobotWorkshopRobotWorkshop Posts: 2,307
    edited 2010-05-28 15:17
    lardom said...
    I feel pretty dumb. I ordered ExpressPCB miniboards without solder mask and did not realize how difficult it would be to solder through-hole components without creating solder bridges to the ground plane... When I made the decision to go without solder mask I only considered that I wouldn't have problems bridging the pins of DIP components. Please, does anyone have any tips? I don't mind trashing the current board.

    Are you using a wave soldering machine or other automated machine to do the soldering? I can see where some surface mount parts may be a bit more difficult to solder without a solder mask but most through hole parts should still be easy to solder. Could you post a picture of the board so we can see the issue? As someone already mentioned solder wick is great for cleaning up solder bridges.

    Robert
  • John R.John R. Posts: 1,376
    edited 2010-05-28 15:17
    What kind of soldering iron are you using? Can you put on a smaller tip?

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    John R.
    Click here to see my Nomad Build Log
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2010-05-28 15:38
    My advice is...flux is your friend. Solder-mask or not, having sufficient flux and just the right amount of solder on the tip and you can drag-solder most SMD ICs with a little practice.

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    Chris Savage

    Parallax Engineering
    ·
  • lardomlardom Posts: 1,659
    edited 2010-05-28 16:00
    Thanks for all the support. I was like a kid on Christmas day when UPS knocked on my door. I had already soldered both regulators before checking for shorts. I will use the first board for practice. I've attached a photo.

    I used a 20 watt iron and 62/36/2 rosin-core solder.

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    Bad solder joints.JPG
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  • John R.John R. Posts: 1,376
    edited 2010-05-28 16:23
    Where are the shorts you're concerned with. The only "bridges" I see are on the right most pin of the top regulator, and the left most of the bottom. Both of these pings are connected to the ground plane, even without the bridges, and in at least the case of the top pin, the "thermals" are a contributing cause of the bridge.

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    John R.
    Click here to see my Nomad Build Log
  • ElectricAyeElectricAye Posts: 4,561
    edited 2010-05-28 16:29
    lardom,

    those soldered pins look bad but they do not look unsalvageable. You might be able to simply reheat them one at a time and allow the solder to flow toward the pin. In cases like this, surface tension can be your friend. It might help a little to snip off some of the protruding legs of your component first so they do not act like thermal radiators that dissipate your soldering heat. But don't snip off too much of the leg: you want some of it to stick up so you can press your soldering iron up against it so it will conduct the heat down to the hole. Also, some of what you're looking at might be flux from your solder, which sometimes reflects light and looks metallic, and which can be scrubbed off with a clean toothbrush and pure ethyl alcohol, like the kind you get from Home Depot. If any solder whiskers remain after that, then try out solder wick, as several people have already suggested.

    If you're having troubles, it might be because your soldering tip is too fat. Or, if you can't really see what you're doing, you might try a magnifier of some kind with good lighting.
  • RobotWorkshopRobotWorkshop Posts: 2,307
    edited 2010-05-28 16:33
    You shouldn't have any problems cleaning that up. Compared to some of the robot boards I've had to repair for people you don't have any worries.
  • lardomlardom Posts: 1,659
    edited 2010-05-28 16:48
    John R., I may have wicked some of it away. The middle pin on the bottom regulator is still shorted. The photo helped me see it better. If you don't think it is a lost cause that's encouraging. When I first tested it I got 4 beeps when I only should've gotten two. I'm in the process of assembling my prototype and I am anxious to finish it. My circuit's been on a breadboard for several months. I took a picture of the enclosure I will put the PCB in with an LCD, keypad and an RJ45 connector.·

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  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-05-28 18:31
    Where you have access, you can always solder from the other side of the board. Next time, put the solder mask on the top side and the traces on the bottom. (Even this is not without it's risks if you have parts in TO-92 packages. When you push those parts into a board, the edge of the hole will often shave off slivers of plating as the leads spread, which can cause shorts topside.)

    -Phil
  • Dr_AculaDr_Acula Posts: 5,484
    edited 2010-05-29 00:57
    Solder wick is very handy.

    To cut the pins short before or after soldering? I'm still pondering the merits of either, but I do have some old components that are >20 years and they get oxide on the outside, and cutting before soldering at least gives some bare metal to join to. So my current philosophy is to cut before soldering on older components. New boards + new components are a pleasure to solder - if I'm in a good rhythm I can do two joints per second.

    If the join is visible on a photo but not to the naked eye - do you have a good lamp over the work area? I've found a 100W desk lamp right up close helps a lot - and I've gone for the compact flourescent globe as it does not get nearly as hot.

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    www.smarthome.viviti.com/propeller
  • lardomlardom Posts: 1,659
    edited 2010-05-29 02:54
    I have gotten an amazing amount of help here. I study everything. Wow... I was depressed last night. I can do this. I would have quit long ago if it were not for this electronic community. This forum gives us access to an incredible pool of talent. I'm still fairly new at this having written·one Pbasic app in '09'. Before that I'd never programmed anything. I had always thought programming was like painting a mural dot by dot by dot.·Spin has started·to click but I clearly still have an awful lot to learn.

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