How to Melt a PCB

Today, I tried to master SMD soldering, but it didn’t went as expected. The first board I soldered I did by hand, which was a tedious job which required many tries, but in the end, it worked. However, I wanted a more simple way of soldering boards as I may need more boards in the future or as I just want to know that I can put together the final product. To do this, I used the stencil I bought from PCBWay and some solder paste. To put the solder on is not easy but also not impossible. After some practicing I knew how much paste I should apply, with what pressure, and other useful skills like focusing my eyes really short distances…

Burned

Burned

The first “batch” went into the oven, at 300 degrees Celsius. This is too hot as the solder paste has a melting point of 217 – 220 degrees. The human errors I made did not stop there, I also forgot it there, in the heat. I got a reminder when I saw white smoke coming out of the oven, tt turned out that the PCB had totally melted and could not be saved.

Melted

Melted

For the next try, instead of an oven, I used a torch to melt the solder paste. This way, I can see when the solder has melted and then remove the torch from the PCB. However, this did not work either; as the solder paste melted nicely, as so did the connector. And even if it haven’t melted, some of the pins had too much solder on them and where connected with each other.

So I really don’t know what to do next. I could still continue develop the prototype but I would have problems with moving on to a final product.

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Comments (10)

  1. Sir. you are my hero. I have been dreaming about a SBC laptop/Lenovo Thinkpad frankenputer for a while now.

    I was going to use a Banana Pi M2 Ultra. It has a real SATA (not usb 2.0 to sata).

    For the screen, I’ve found a few alibaba HDMI to LVDS boards, like this http://berb.ec/lvds, for resonable prices. That will handle the display.

    Power will be handled by a bank of 18650 batteries. I am going for multiples of 10 batteries, charged by an individual control board. A ten pack is under $4 shipped at http://berb.ec/18650

    Charging those boards I plan on wiring a set of micro usb cables to a 5V 10A charger like http://berb.ec/ac5v

    My big problem was getting the keyboard to work. Like you, I’ve hunted for an off-the-shelf solution. Since none seemed available, I was going to test the keyboard pin-by-pin with the GPIO connectors. Your work has given me hope this is possible. PS2 to USB adapters are $0.99 any day of the week. Even if that isn’t possible, just knowing it is possible to get the a breakout board made for the connectors is amazing.

    1. Sounds like a fun project 🙂 But isn’t the original computer more powerful than a Raspberry Pi? However, regarding the track point, I managed to get it to work with a PS/2-USB adapter. For the keyboard, I used a Holtek keyboard encoder, which seems to work fine 🙂

        1. The Holtek encoder does have a microcontroller embedded, but all is in one IC package, so it is somewhat smaller than the Arduino 🙂

          1. I got my design working perfectly with an Arduino. My problem is I don’t have a nice PCB like you – I soldered straight to the connector. This makes the joints very fragile. Any tips for a complete n00b to get a pcb like yours for a different connector?

          2. Sorry for a late answer. I answered you more recent comment and I will send you the schematics and footprint so you can modify it in KiCAD.

  2. The Thinkpad I’m looking at is a T60 which came, at best, with a Core Duo T7400 dual-core. The Udoo x86 comes with a Pentium N3710 quad core that boosts to 2GHz+. The NanoPC-T3 comes with an 8-core, 64-bit ARM. There is speed to be had in SBCs if you search!

    The final performance of the device, obviously, isn’t the goal – the journey is part of it!

    Regarding your work, did you use your custom board to plug into the keyboard module, and then wire some pins to the ps2-usb?

    The keyboard part, I assume it was a custom-programmed Holtek. Are there anymore details available?

    Again, thanks for all your work.

    1. I understand and hope that you succeed 🙂

      I only used the breakout board I made and then wired it directly to the Holtek encoder which in turn has a PS/2 interface that I connected to a USB-PS/2 adapter with some wires 🙂 I haven’t yet connected all of the columns/rows so I don’t know if it will work all the way without customizations.

      Holtek encoder: HT82K629A
      Adapter: http://www.ebay.com/itm/Dual-PS2-Female-to-USB-Male-Converter-Adaptor-Cable-F-M-for-Mouse-Keyboard-/171970217242?hash=item280a39451a:g:wbEAAOSwYHxWIGmo

  3. Buy a ‘hot air rework station’ that has a controllable airflow, or a reflow oven kit that uses an Arduino or similar microcontroller and relays to close-loop control the temperature of a small toaster oven to hit the right profile for the solder.

    1. The boards with the improved footprint where a little bit easier to solder by hand so I will go with them until I need bigger volumes 😉

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