If your solder paste tube comes with a 14 gauge needle, you can get some smaller solder paste dispensing tips from Lee Valley, the woodworking supplier.
Over the past six months, I have been working with surface mount components. To date, I have designed several circuits with KiCAD and ordered the boards from OSH Park. For soldering, I bought a tube of MG Chemicals 4860P No Clean Solder Paste from Amazon.
After a bit of practice, you will find hot air soldering SMD is fairly straightforward, as long as you have a good heat pencil and microscope. I settled on 1206 size SMD components.
The challenge with the MG Chemicals solder paste is the size of the stock needle provided with the dispensing syringe. Based on my measurements, the stock tip is 14 gauge, shown above right. This is a fairly large diameter needle with a 1.6 millimeter inner diameter. Quite often, you get too much paste extruded onto the PCB. Since the solder pads are quite small, especially for SOT23 transistor footprints, you end up with a mess. With too much solder paste, there is also greater risk of globs and bridges.
What I needed was some smaller gauge solder paste dispensing tips.
While browsing my local Lee Valley woodworking shop, I found a perfect solution. Turns out that woodworkers use syringes for applying small amounts of adhesive. You can find a collection of ten 18 and 20 gauge needles at Lee Valley for CDN $7.50. And, wonder of wonders, these tips fit perfectly into the MG Chemicals syringe.
Lee Valley is one of those wonderful gems that sells all sorts of neat stuff, especially useful for makers. For more information about different needle gauges you can use for solder paste dispensing tips, you can check out information on Birmingham Gauge.
Solder Paste Dispensing Tips – My Experience
I tried both the 18 and 20 gauge needles with my MG Chemicals paste. The 20 gauge is very small, with a 0.6 mm diameter. I found it very hard to extrude paste, lots of thumb pressure required.
So, I switched to the 18 gauge needle with its 0.8 mm diameter, approximately 50% smaller than the stock dispenser. Worked perfectly for dispensing small amounts of paste on the small pads.
Much less cleanup required, especially with the tiny SOT23 transistors in my LZ1AQ loop amplifier.