With this tool you can precisely dispense very small dots of solder paste. Although this solder paste dispenser is cheap and uncomplicated, it works better for small SMD parts than many automatic dispensers.

There are many solder paste dispensers on the market, often motor controlled or pneumatically. But can you use them for very small solder dots? It is important that you are able to dispense micro-dots of solder paste, else it will easy lead to solder bridges. The problem with SMD soldering is always the excess of tin. That’s why I invented this hand-tool solder paste dispenser.

FOR SALE

Manual solder paste syringe dispenser with spare parts.
You can buy it on my shop here

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:

In de video below, I'm soldering 0603.

Bent needle tips

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

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:

 

The following diameters are useful:

• Pink 0.60mm
• Blue 0.41mm
• Red 0.26mm

Plastic has also the advantage that you can increase the diameter with a needle:

Cleaning the dispenser tips

Immerse the tips in acetone to clean them.

Dispenser assembly

Mounting the syringe with spring requires some practice, be careful not to force the holder:

Note that you have to increase the diameter of the plastic tips with a needle.

Nanoliter / microliter pipette for laboratories

The micro-dot solder paste dispenser can also be used as a pipette to handle very small volumes of liquids in laboratories. For use for solder paste, it must be possible to accurately dose a volume from 10nL to 100nL.

Can we do 0201, 01005 and ball grid arrays manually?

With the dispenser we can handle SMD components with a package 0402 and larger easily. I was curious if even smaller components such as the 0201 could still be done with the dispenser. I have made a try, it was difficult but, in the end, it worked, I’m hopeful. But 0201 parts are hardly used anyway.

It is more important whether ball grid arrays can be done, then an expensive stencil may not be necessary anymore. I found out that the plastic bended tapered tip is too large for 0201 and BGA and the viscosity of the solder paste must be just right. I don't have time to investigate this further, but there may be people who see this as a challenge…

See my try here for the tiny 0201:

Low viscosity solder paste for the dispenser

The viscosity of solderpase is very critical to be able to apply micro-dots with a dispenser. We need low viscosity paste, this also sticks better to the PCB.
Common cheap solder paste that works fine for stencils doesn't work with a dispenser, it is too syrupy:

Normally, you have to make the solder paste thinner by mixing it with for instance no-clean Topnik flux RF800. Note that you need very little flux, less than a drop. The solder paste may not be too liquid.

Because of the mixing with flux, the solder paste will dry out in the syringe after some time.

Solder paste info

• Solder paste is thixotropic, to lower the viscosity, it may be needed to stir the paste.
• The paste must be at room temperature before use.
• Note that the volume of the soldered joint is about half that of the solder paste applied.
• There are special solder pastes for dispensing and stenciling

Solder pastes are classified based on the particle size, from type1 (160 µm) to type8 (11 µm), see Wikipedia.

Here you can see the solder paste with the solder ball particles very well here:

I don’t have evaluated different solder pastes, who want to do this?

Kester has a special solder paste for dispensing: Kester R500 solder paste. This is a water-soluble solder paste formula specifically made for dispensing. It maintains its activity and tackiness characteristics for up to 8 hours.

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:

After the components have been placed, you can solder the board as you like, with a reflow oven or hot air. I use the Atten AT858D to solder SMD parts, it is important that you can control both the temperature and the airflow.

Assembling 0402 SMD parts

Loupe

I use a loupe with 10x magnification. But keep in mind: the loupe must have a double lens to see the small SMD components well. Unfortunately, almost all loupes use just one lens.

Tweezers

Small SMD parts such as the 0402 require tweezers with a curved pointed tip:

FAQ 

• What type of solder paste do you use?
  I used Sn63/Pb37 25-45um from Eleshop in the Netherlands.
• 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.