Solder paste/flux manual syringe applicator

[Jeroen3]

Wouldn't this be possible using the air cardridges used by paintball guns?

[fivefish]

I saw a blog posting where the guy used ordinary compressed air (duster can). Of course, he had to rig coupling adapters to connect it to the unit. 

PS: The hose coupler that is originally installed in these units (from China) do not fit the USA standard shop compressor tank couplings/valves/whatever you call them. I had to cut mine and install a new quick-disconnect so I can hook it up to my air compressor tank.

[zapta]

I am looking around for DIY paste dispensers that don't require air pressure.  Found an older design that had once a board sold on Tindie and a new once with a video on you tube. Both use a small step motor and a screw to push the plunger. I don't think they pull back to avoid oozing but I see why a 3D printed plunger can't fit into the rubber plunger and pull it back.

http://www.thingiverse.com/thing:384680

[zapta]

I built a prototype based on Geir's design. The mechanical design is different and allows to motor to pull the plunger back to avoid oozing. I am now playing with the motor control parameters to see if I can get consistent drops. The design files are here though this is still a work in progress.  https://github.com/zapta/misc/tree/master/paste_injector

The controller is Arduino Pro Mini, the motor is 28BYJ-48, and I use the AccelStepper library to control it.

One thing I learned so far is that avoiding air bubbles in the syringe helps with the oozing presentation.

[zapta]

I am getting very good results with the prototype. Initially I tried generate individual drops, that is, on each button press, push the plunger forward N steps, then immedielty pull back M<N steps to avoid oozing but it was difficult to control the drop size, especially the the solder paste had a few air pockets as well as air between the rubber seal and the plunger.

The approach that is giving me good results is simply push the plunger in continuously and slowly. This way I place the needed on the pad wait a second or two and move to the next one. If a pad needs more paste I can just wait more. This way I could get very small drops. Also, having the needle orthogonal to the PCB such that the PCB touches the entire opening of the needle gets the paste to stick better.

Next step is to figure out the ergonomic, how many controls/buttons to use and at what location. I find it easier to hold the unit vertically with both hands, one at the top and the other at the bottom guide the needle.

So far it looks very promising. Always wanted one but didn't want to bother with an air compressor.

Cost is very low, the motor with the controller is about $2, and then just a ULN2003, a small AVR, buttons, etc, and it can operate on a standard 5V USB charger.

[PlainName]

Please do keep us informed of your progress. I am feeling the urge to justify a 3D printer for this

[Jeroen3]

Yes. If anyone has a link to where you can buy such a thing. Please share.
I've no room for a cnc or 3d printer 

[Psi]

Whats wrong with your typical syringe and its plunger.
As long as you get the right sort of solder paste (something that isn't too thick) it works well and you can repeatedly put a tiny bit of paste on pads pretty quickly.

Although it can be a bit tricky to hold if the syringe is very full, due to the length that the plunger sticks out.
But its easy fixed by removing some paste or getting less full syringes

[zapta]

Whats wrong with your typical syringe and its plunger.

I tried it in the past with CML/Kester EP256 and Chipquik T3 paste and didn't get good results. It was difficult to get consistent amounts and the paste didn't stick well to the board. Possibly a better flowing paste such as ChipQuik T5 will give better results.

With the motorized approach, the paste keeps flowing very slowly and pressing the needle vertically against the PCB creates a tiny drop of paste that is stuck well to the board.

[Psi]

I find chipquik paste is always far to thick to hand paste with a syringe.

The loctite paste I have atm is perfect for hand application. The label has worn off though so i can't give you a part number.

[zapta]

I find chipquik paste is always far to thick to hand paste with a syringe.

The loctite paste I have atm is perfect for hand application. The label has worn off though so i can't give you a part number.

I got recently ChipQuik T5 paste (finger solder balls) and it is runnier and stockier than their T3, at least when fresh.

Somebody also mentioned here Teflon coated needle that make the paste flow better.

[KL27x]

It's almost as easy to me to hand solder vs dotting every pad, placing every part (on a necessarily small panel), then messing up and bridging every SSOP. I can only get SSOP right half the time, even with a stencil.

But FWIW, if you want to manually paste, try this before getting super fancy:

1. 3cc syringes. Smaller diameter = more pressure/leverage with a given effort. Like putting the bike into first gear.
2. Plastic tips. The pink ones (I think 20 gauge?) A tapered plastic tip = more flow for a given pressure and less continuation after pressure is ceased.

Take a big bore needle and put it on your standard solder paste syringe. Stick it all the way down into the back of the 3cc syringe. Fill up, avoiding any air bubbles. Easy, peasy. Now take the plunger and a piece of stripped 30 AWG wire. Stick the end of the wire into the back of the syringe as you push the plunger in. This lets out the air. Once seated, remove the wire. Turn the syringe rightside up and squeeze out any air left in the tip.

Tip: Fill up all your 3mm syringes at once, until your main syringe is empty. But put the rubber piece, only, into the back, without the plastic plunger. That makes for more compact and secure storage. (Make sure to use luer lock syringes, and buy the black plastic caps). When you need a new syringe, pull the plastic plunger out of the old one and secure into the new syringe, before removing the black plastic cap.

You can also buy a luer lock-to-luer lock adapter for filling syringes point-to-point, so to speak. I bought one of those. Didn't really pan out. In fact, filling from the back left little to no air and was better.

[zapta]

Take a big bore needle and put it on your standard solder paste syringe. Stick it all the way down into the back of the 3cc syringe.

Do you mean forcing the needle into the syringe main chamber?

Now take the plunger and a piece of stripped 30 AWG wire. Stick the end of the wire into the back of the syringe as you push the plunger in. This lets out the air. Once seated, remove the wire. Turn the syringe rightside up and squeeze out any air left in the tip.

The wire trick is interesting, I will give it a try. Hopefully it doesn't damage the rubber.

I also noticed that some syringes have an air bubble by design. Noticed it for example with a Kester paste I got from CML. Look at the picture below, the plastic pusher has a flat end but the rubber seal is conic (on both sides) which creates an air bubble between the pusher and the rubber. Other syringes have a conic pusher end which fits the rubber seal.

... and buy the black plastic caps

Does it go over the needed?  Any link or picture?

2. Plastic tips. The pink ones (I think 20 gauge?) A tapered plastic tip = more flow for a given pressure and less continuation after pressure is ceased.

There are also needles coated internally with PTFE which result is smoother flow. Somebody mentioned them here once and mcmaster carrys them.

[KL27x]

Do you mean forcing the needle into the syringe main chamber?

No. I was just needlessly describing the obvious. Take the empty, open 3mL syringe without the gasket in the back and hold it nose down. And lower the supply syringe needle as far down into the back of the syringe as it will reach. And then fill the 3mL syringe from the bottom (nose) to the top (back).

Then insert the thin wire into the open back of the syringe before putting the rubber gasket in. The wire rides between the side of the gasket and the chamber, allowing a tiny imperfection to let the air out as you push the gasket in, so you don't get a spongy air bubble at the back of the syringe between the solder paste and the gasket, which would defeat the purpose of using a smaller syringe. When you press the plunger you want solder to come out, immediately. Any air that is inside the syringe will cause a delay when you press on the plunger, while the air is compressing. And any (now) compressed air inside is what causes the paste to continue dispensing after you let go of the plunger. You have to be careful to not make any air bubbles when filling the syringe.

The black screw on caps are luer lock. You take the needle off to use the caps.
http://www.amazon.com/Luer-Lock-Dispensing-Syringe-Pack/dp/B00BQ4IO84/ref=sr_1_1?ie=UTF8&qid=1441053085&sr=8-1&keywords=syringe+caps

If you leave the needle on, it doesn't matter how tiny the gauge is. The solder paste will dry out from the needle end, back up into the chamber, plugging the syringe with dried out solder paste cement. If you are going to use the syringe again within a day or two, you can leave the needle on. But if you're done, toss the needle and put the cap on.

[zapta]

Thanks KL27x, I will order a few caps.

Do you have also a link to the plastic needles that you use?

[KL27x]

http://www.amazon.com/Dispensing-Needle-Plastic-Tapered-0-024id/dp/B001QQ9QH0/ref=pd_sim_328_2?ie=UTF8&refRID=1S923AYQWAJQFNA2PQ7X&dpSrc=sims&dpST=_AC_UL160_SR160%2C160_

[KL27x]

These 3mL syringes and this particular plastic needle is also handy for dispensing liquid rosin flux. I leave the needle on with rosin, no problem. I can't seem to keep a rosin pen tip from clogging and/or fraying to shambles, and it's not very convenient to soak the pen in alcohol before I can use it.

Even if you habitually dispense 5 times as much flux as you wanted, it's still cheaper than using flux pens, and there's no such thing as too much flux. On a fresh board, you can squirt out a little puddle and wipe it around the board with a bit of paper towel.

[nanofrog]

These 3mL syringes and this particular plastic needle is also handy for dispensing liquid rosin flux. I leave the needle on with rosin, no problem. I can't seem to keep a rosin pen tip from clogging and/or fraying to shambles, and it's not very convenient to soak the pen in alcohol before I can use it.

Even if you habitually dispense 5 times as much flux as you wanted, it's still cheaper than using flux pens, and there's no such thing as too much flux. On a fresh board, you can squirt out a little puddle and wipe it around the board with a bit of paper towel.

Ever considered a refillable brush pen (Bonkote for example)?

[zapta]

Ever considered a refillable brush pen (Bonkote for example)?

The solder paste is probably too thick.

How good are those reusable Bonkote applicators for flex, for example Kester 951?  Do they get messy? Easy to clean?

Edit: is this too good to be true ?  http://r.ebay.com/csHxNd

[nanofrog]

Ever considered a refillable brush pen (Bonkote for example)?

The solder paste is probably too thick.

How good are those reusable Bonkote applicators for flex, for example Kester 951?  Do they get messy? Easy to clean?

Edit: is this too good to be true ?  http://r.ebay.com/csHxNd

Solder paste would be a total disaster (just meant for flux). 

As per applying flux, they're rather nice IME (beware of the fakes on eBay*; the lowest price I've seen here in the US is ~$15 for a single, with most places wanting ~$17 - $20).

• Unlike a disposable pen where you push the felt/nylon tip down to get flux, you control how much is delivered by squeezing the Bonkote pen body (measured amount per squeeze, not free flow). Combine this with how long you let the brush linger on the pads/holes, you get a lot more control IMHO.
• More tip styles & materials to suit the user/work at hand, which can offer further control.
• Because of it's internals (valve), it doesn't drip or spill all over the place, assuming you don't squeeze out more than the brush/tip can handle.

I've never actually had to clean one (entire unit), but running some alcohol through it wouldn't be that difficult (only swished the brush end around in some alcohol).

* The fakes actually can be used, but you'll likely have to remove the internal reservoir components (remove valve, as they only sort of work). Usable, but you'll have to keep the brush end up to keep the flux from dripping/spilling.

[zapta]

Thanks nanofrog. They have several tip models. Which one do you recommend for SMD work?

[nanofrog]

Thanks nanofrog. They have several tip models. Which one do you recommend for SMD work?

I only have the BON-102 (small fine point nylon brush), so I use it for everything. The brush tip truly does makes a very fine point when it's wet, so it's very nice for SMD work IME (you'll really appreciate it when drag soldering  ). Holds more than enough flux for PTH too (it's fine point, but the brush itself isn't micro sized, so can hold a decent amount of flux).

Prior to trying the Bonkote, I was just dipping inexpensive artist brushes into a tiny well of flux in a porcelain spot plate or using a needle bottle. Found the brush gave the most control, and I figure the brush versions will outlast the felt tips (assuming the felt used is equivalent). And all of it is less expensive than the disposable pens. 

[neslekkim]

Checked farnell now, and there are many called BON-102.. hm?

[nanofrog]

Checked farnell now, and there are many called BON-102.. hm?

No letter following the 102 is the model in the photo (original). A letter after the 102 = one of the newer styles they've come out with.

Unfortunately, it appears Farnell have stopped stocking the singles and only offer the 5 packs now (BON-102 5pack). There's also a kit (all 6 styles, here).

Fortunately, Ideal-Tek is a distributor and they're available on Amazon.de ("Ideal-Tek Dosing Pen" shows you all of them; just the BON-102). 

Datasheet might be of some use (.pdf; nice close-up photos to show the different tips available).

Hope this helps sort your import duty fees.   

[Augustus]

Edit: is this too good to be true ?  http://r.ebay.com/csHxNd

They seem to be heavily counterfeit, so yes, be careful... I bought one of the 102s from Banggood (SKU188447) and of course it was a fake, doesn't work at all. The flux doesn't flow to the tip, it leaks all over if you dare to squeeze it, the tip dries out...  So I threw it in the bin, lesson learned...