Hot plate reflow test 1 and 2

in #liveupdates, tools by Ian | 10 comments

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Reflowed two 0805 caps on two qfp protoboards. One at 250 and one at 240c.p Both took about 30 seconds to reflow. Anyone know the optimal temp for crappy old lead solder paste? Board at 250 looks scorched but that could be from the reflow oven instead. Will do a second test to find out.

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Comments

  1. neslekkim says:

    Did you mix the old paste with new flux to revitalize it?

  2. royco says:

    I usually preheat at 150C then bump it up to 206 after a minute. I see it starting to flow at 180C for the smaller parts. I think above 225C your PCB will have some discoloration of the mask or start to scorching. This is with an unmodified black and decker oven tho.

    • ScottD says:

      210 to 220C should be about right for hotplate and leaded solder. It depends somewhat on how even the heating is on your hotplate. Also, I’ve noticed that the heat transfer through the PCB can vary a lot. It seems like boards with ground pours on top and bottom transfer heat a lot better and reflow quicker. I generally start out around 100C for a minute or so to drive off any moisture, then raise the temperature to around 160C for a soak phase of 60 to 90 seconds and then go up to around 210 and watch for all the solder paste to melt. If it seems like the paste isn’t melting then I prefer to raise the temperature instead of letting the board stay longer at a high temperature (unless there are some particularly temperature sensitive parts on the board)

  3. JuKu says:

    You can find one manufacturer’s recommended profile here:
    http://dangerousprototypes.com/forum/viewtopic.php?f=2&t=4471#p43907

  4. Peter says:

    I saw a video once where they used a heater (infrared if I recall) to prewarm the board to below melting temp. Then they used a hot air wand to go over the board and reflow all the parts. Because everything was prewarmed, it went very fast. I have been meaning to try it using a clothes iron and hot air reflow station. Perhaps low to mid 100s might be a good prewarming temp. I think this might get around the scorching problem.

  5. Macpod says:

    I use an old pc-35 corning hot plate I got off ebay. It takes a long time to heat up so I just crank it to 215, check the temp with a thermocouple attachment that Came with my Fluke 87V, then shut it off when it hits that temp after I see everything has reflowed.

    My biggest regret with the corning is the small heat platform and heat pattern. This looks pretty good for 50$. Any idea where to get one without having to leave the U.S.?

    • Macpod says:

      Er, clarifications.. pre-heat it before cranking it up that high if your board heats up quickly. 110 will do for 30-45 sec.. and my measurements are in C.

    • Ian says:

      You should be able to find a dozen different brands that look exactly the same on Aliexpress. They will probably cost about twice as much ($100 range).

  6. Brian says:

    Old post and not great video quality but here is my procedure:

    http://teholabs.com/2011/09/making-a-cygni-in-4-parts/

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