Another attempt at doing a hotplate reflow with manually applied solder paste, but on a custom PCB with solder resist this time. JLC PCB (not a sponsor) delivered these PCBs in just 6 days. I think that's the fastest I've had a batch of PCBs delivered.
This is a version of the Gallium PCB that fits into a standard 6" by 4" (about 100 by 150mm) picture frame and powers 54 independent LEDs from a standard USB power supply.
I've made a few of these before, but this one is part of an experiment with hand application of solder paste diluted with flux. It worked, but the flux evaporated quickly and caused some of the solder to crack and ping before it had melted. Only one of the resistors failed to solder properly, and was easily fixed with a soldering iron and touch of flux.
Next test will be hand soldering in a few different ways.
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10 thoughts on “Reflow attempt 2 on a custom led art pcb with resist .”
  1. Avataaar/Circle Created with python_avatars Andrew Meredith says:

    I just received those from JLCPCB today can't wait to put it together. The quality is amazing! To took about a week to get mine in the divided states

  2. Avataaar/Circle Created with python_avatars Odd One Out says:

    Right. Who else has started blowing on their screen when the fumes started rising?

  3. Avataaar/Circle Created with python_avatars Peckelhaze says:

    Turned out very nice. Is the hotplate specially for reworking?

  4. Avataaar/Circle Created with python_avatars Jumbo Egg says:

    Looked to me that board was getting hotter in the middle because that was the hottest part of the hotplate, where the heater element is.

  5. Avataaar/Circle Created with python_avatars Daniel Horne says:

    try making one with 200 leds on it the normal 5mm leds

  6. Avataaar/Circle Created with python_avatars Ian Leitch says:

    Are the smd resistor packages 0402? I have flashing yellow LEDs on the slow boat already.
    Many thanks.

  7. Avataaar/Circle Created with python_avatars pjtruslow says:

    Hey Clive. I hope you see this
    I used the hotplate reflow method yesterday on a massive 400 pin connector 40×10 array surface mount, 0.05" spacing. it is a Searray connector with solder charges on the pins, and I used solder paste with a cheap stencil from JLC and a credit card. I heated a plate of aluminum on the hot plate to 550F, placed the board on, waited until the solder began to melt and waited 30 seconds, then removed the board.
    It looks absolutely beautiful, and was a connector that is completely impossible to solder without a good reflow oven, or so I thought. no melted plastic on the connector, and every joint looks beautiful.
    It did take a few attempts to get a good solder paste application, and i specifically selected everything with a lead/tin alloy to make life easier.
    Thanks for showing the method.

  8. Avataaar/Circle Created with python_avatars Regelos says:

    An idea for a future lighting/pcb project is I hobby (warhammer 40k for me) and a nice painting light that's bright. I've tried a couple less expensive ones, and you get what you pay for sometimes so they weren't great, I'd love to see your take on one.

  9. Avataaar/Circle Created with python_avatars Lewis Heard says:

    Could someone educate me on why each LED needs it's own resistor, could we not just use a buck converter to provide the entire circuit with exactly the correct voltage? (since all the LEDs are the same and connected in parallel)
    I'm sure there's a good reason, but I'm new to all of this 🙂

  10. Avataaar/Circle Created with python_avatars Twotone says:

    JLPCB orders office opens post: "Stop everything, we have an order from Big Clive."

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