Spoty solder paste dispenser manual

Prefered Chipquick solder paste

To be able to apply micro-dots of solder paste, the tip that I provide has a small diameter of 22G. This has the consequence that ticker solder paste that works with other dispensers doesn't work with the 22G blue tip.

I have tested several types of solder paste, but only the SMD4300AX10T4 soldering paste from Chip Quik works fine with the tiny 22G blue tip.
It is specially made for dispensing by a syringe. It is a thermally stable solder paste No-Clean Sn63 / Pb37 type-4 in a 35g Syringe:

You can buy it at Mouser, Digikey and Amazon.

The following solder pastes don't work well:

• TS391AX50 type 4 in jar 50g: it sticks badly to the PCB and is therefore difficult to apply.
• SMD4300AX10T5 type 5 in syringe 35g: when heated, the tin spreads out over the PCB and causes short circuits.
• SMD4300AX250T5 type 5 in jar 250g: same problem as SMD4300AX10T5 but slightly better.

ChipQuick Sn63Pb37 solder paste type 5 problem

How to fill the dispenser with solder paste

Normally the solder paste is packed in a thick syringe. Take the thin dispensing syringe and remove the plunger. Then spray a little paste into the thin syringe, 15 mm is usually sufficient. Then insert the plunger and push the pasta all the way down.
To easily fill the syringes I modified a nozzle:

Filling head for the syringe

Watch out for bad solder paste

• If the syringe was filled with paste a few days ago, you should squirt out the first part, without using it, as this may be unreliable.
• Solder paste is a critical product, if it has been stored too long or used too quickly after being refrigerated, it will no longer work properly. You can then mess up an entire PCB. If you are not sure if the paste is still good, first make a test PCB with a few SMD components.

Examples

I've used the syringe dispenser for assembling the Arduino SAMD21 board SAM 15x15: The SMD package 0402 is easy to do, see R1 and R2:

Manual assembling 0402 SMD parts

F.A.Q .

• How many pads are you able to tin with one filling?
  With 10mm of solder paste in the syringe you can already cover hundreds of SMD pads.
• How can I clean the dispenser tip?
  Immerse the tips in acetone to clean them.
• Can the solder stay in needle or clean each time? 
  You can leave it in the needle, but you should always squirt out and discard the first portion of tin before you start.

Bent needle tips

There are all kinds of needles for sale that are suitable for the syringe:

Steel tapered bends needle

Steel needles have a high resistance to the solder paste because they are thin over the entire length. Therefore, I use bend plastic tapered dispensing tips:

Plastic tapered bends needle

Needle diameter vs color

Needle colors are standardized according to Birmingham gauge.
Note that sometimes other colors are used, for example on AliExpress.
I recommend to use 22 - 27 Gauge tips for solder paste dispensing.

Smallest recommended dispense tips for solder paste T4

I recommend to use only solder paste T4 for dispensing. 
The needle inner diameter should be larger than seven solder ball diameters. 

Particle size 20-38 [μm]

• Gauge 22 
• Gauge 25 
• Gauge 27 

Sealing the dispense tip airtight

I used a piece of faucet rubber with a drilled hole for sealing:

Faucet rubber for sealing

Sealing a needle with tap rubber