To build the dispenser, we just need a 1mL injection syringe, a wooden stirrer, a glue gun and strong yarn. Drill 1.5mm holes in the wooden stirrer for the yarn. Mount the yarn and glue everything together with a glue gun, the picture explains everything. The needle should be shortened. Do not cut it, but bend it with two pliers back and forth until it breaks.
Precisely dispense the smallest amount of solder paste
The main thing that goes wrong with soldering surface-mounted devices is the excess of solder. On this extremely small PCB from an iPod touch, which contains 0201 size SMD, you can see how little solder paste is used:
Fine-pitch packages easy lead to solder bridges, unless you are able to dispense a minimal amount of solder paste. Solder paste dispensers often use pneumatics or a motor drive with electronics, but I wondered: can it be made simpler? So I invented this hand-tool, henceforth called the Albert solder paste dispenser. The tool is easy to handle and you can precisely dispense the smallest amount of solder paste:
After the components have been placed, you can solder the board as you like, with a reflow oven or hot air.
Assembling 0402 SMD parts
I've used the syringe dispenser with great success at assembling the prototype of the SAM 15x15:
Fill the syringe by sucking the solder paste out of its container, 10mm is sufficient.
You can use the solder paste in the syringe no longer than a few days. Due to the pressure, the components in the solder paste separate themselves from each other. Initially, there appears a very thin solder paste, with an abundance of flux. Thereafter the syringe will be clogged with thick paste without flux.
Purchase 10 syringes that you throw away every time the solder paste is no longer good.
- What type of solder paste do you use?
I used Sn63/Pb37 25-45um.
- What is the diameter of the needle?
I used an outer diameter of 0.5mm.
- How many SMD are you able to tin with one filling?
You can fill thousands of SMD pads until the syringe is empty. However, the life span is more defined by the drying out of the solder.