using solder paste out of a tub - Page 1
Forum section: electronics / beginners

author: Simon
author_rank: Unknown
timestamp: April 10, 2014, 08:17:06 am
content: so I bought a cheap pot of solder paste ff ebay. I opened in and this guey lump was in there, not really liquid at all but creamy. I couldn't suck it into my siringe even with the biggest tip and pushing it back out again was also hard and not easy to dose. Result was that I got my parts soldered and not bad for my first attempt but gee that was hard work and not anything I'd feel happy presenting to anyone.How do you use solder paste out of a tub ?Should I just pay the money for a pre syringed one ? how liquid versus solid should the paste be ?

author: Fsck
author_rank: Super Contributor
timestamp: April 10, 2014, 08:24:36 am
content: pull out the plunger, pack it in, use a large enough nozzle st it doesn't require large amounts of pressure, replace plunger.can be a variety of viscosities, but the two extremes (liquid or solid) are bad. usually something tacky, sort of like freshly mixed 2-part epoxy is nice and holds stuff down quite well.probably personal preference, but I don't like pastes that aren't really pastey.

author: Monkeh
author_rank: Super Contributor
timestamp: April 10, 2014, 08:30:39 am
content: Quote from: Simon on April 10, 2014, 08:17:06 amWith a spatula and a stencil.

author: Kjelt
author_rank: Super Contributor
timestamp: April 10, 2014, 08:41:36 am
content: The paste from a tub is for stencil use, not for syringe use. The lead balls are much bigger and stiffer then paste from a syringe (look under the microscope).That is why the paste from a syringe is probably also more expensive per gram than from a tub.You can put it in a syringe (indeed pull the plunger out stick with a spatula some of the paste inside and press the plunger till all the air is out then apply the nozzle) but only if the nozzle is big enough, you can forget about the extreme small nozzles.The paste is going to be a bit more slimy (more usable) if it is at room temperature. Also I heard/read some people adding extra flux but I do not know which exact flux would work.Oh before I forget you should always mix the paste thoroughly in the tub for consistency that also helps make it more slimy.

author: Simon
author_rank: Unknown
timestamp: April 10, 2014, 08:50:52 am
content: ok I'll have to get a prefilled syringe, I used the biggest nozzle my syringe set had and it was still impossible and it's actually too bit a "needle".

author: amyk
author_rank: Super Contributor
timestamp: April 10, 2014, 09:12:39 am
content: It's called "solder paste" and not "solder fluid" for a reason.

author: Kjelt
author_rank: Super Contributor
timestamp: April 10, 2014, 09:14:11 am
content: You are sure the needles are for electronics application ?My gf works in a hospital and brought me a lof of different needles with luer lock which I thought at that time were just perfect but none (even the extreme big ones) worked with solder paste because they have some kind of filter inside blocking it

author: Simon
author_rank: Unknown
timestamp: April 10, 2014, 09:38:25 am
content: No filters in mine, it's just that it's rolling paste not syringe past I guess

author: peter.mitchell
author_rank: Super Contributor
timestamp: April 10, 2014, 09:47:01 am
content: Paste in a tub is fine for hand application with a syringe, as others have said, just get something to scoop it out and pack it into the syringe. Regardless the quality of solder paste you should have no troubles dispensing it out a syringe, the balls are far finer than the needle (provided you didnt get a tiny 32ga or something, you have pref 20~16ga needle), it will just require a bit of force pushing on the plunger...

author: Simon
author_rank: Unknown
timestamp: April 10, 2014, 09:54:40 am
content: well i did get some into the syringe and it was dire trying to dispense it, way too thick

author: Kjelt
author_rank: Super Contributor
timestamp: April 10, 2014, 10:36:12 am
content: Just from your description and if the paste is at room temperature i suspect it could be spoiled.Even the tub paste should be able to smoothly glide over a stencil without too much friction, might be mistaken your words but it sounds like it is pretty dry (dried out).

author: Simon
author_rank: Unknown
timestamp: April 10, 2014, 10:46:00 am
content: I think it was in ok condition and I had kept it in the fridge but I think it being cheap stuff off ebay was just not made for syringe use.

author: CTMS
author_rank: Newbie
timestamp: April 10, 2014, 11:00:02 am
content: The main difference between solder paste in a syringe and a jar is that amount of flux added when manufactured.Generally on a tub if solder paste you will see a metal content i.e. 90%, this means 90% metals / 10% flux. Solder paste in jars is generally used in manufacturing with stencil printers and companies do not want to have solder paste too runny and want minimal residue.When solder paste is manufactured for syringe dispensing it is generally made with a higher flux content for easier dispensing. You can always buy solder paste in jar and dispense into smaller syringes but generally it will dry out faster and can be messy.Regarding dispensing needles to use for syringes, you would be best to use a taper plastic tip as appose to a metal tip. You would not go any smaller than a 20 gauge tip. If you go smaller then the solder balls in the paste will not make it through the tip and you will struggle to dispense the paste.Element 14 have the paste available in syringes and small jars, both use the same ball size, only difference is the syringe mix has more flux mixed in it.http://au.element14.com/aim-products/ct-l63-s0515/solder-paste-63-37-183-c-15g/dp/2366335http://au.element14.com/aim-products/63nc257-2-j250/solder-paste-sn63-250g/dp/1827457

author: sleemanj
author_rank: Super Contributor
timestamp: April 10, 2014, 12:02:27 pm
content: Quote from: Simon on April 10, 2014, 10:46:00 amYou did allow it to warm up first before trying to dispense it though didn't you. Store in the fridge, but you must allow it to return fully to room temperature before using.You could always add in a little extra paste flux - it's not like you're in a high production setting where you need to adhere to exact specifications (otherwise you wouldn't have bought from ebay in the first place), so just experiment a bit.

author: Simon
author_rank: Unknown
timestamp: April 10, 2014, 12:06:19 pm
content: yes maybe although it was not like it was a tube that was 1/2 "full" it was in there as a blob so was in a blob before it even went in the fridge, not sure if that is right but yes i guess i should let it warm next time.

author: Teledog
author_rank: Regular Contributor
timestamp: April 10, 2014, 04:10:15 pm
content: I've had a couple of "tubs" of solder paste in the fridge for years.Like other posters have said, let it warm up first.I suck it up into a 1 ml syringe without the needle.The smaller the syringe, the easier it is to work with, ..but you may have to fill it more often.Then you might want to experiment exuding it with different needle gauges, depending on the ball size of your paste (#16-#18-#20?)Also (Very important!), make sure your needle is short ..a long needle is much more difficult to press goop through than a short one.If you cut it down, just make sure you don't pinch or have a burr blocking the needle tip/hole.G'luck!

author: Kjelt
author_rank: Super Contributor
timestamp: April 10, 2014, 05:23:50 pm
content: Quote from: Simon on April 10, 2014, 10:46:00 amDoes it have an extra plastick cover that goes inside to fully cover the paste from drying out? That is how the good brands have their paste packaged.If not I would suggest next time (if there is going to be a next time) cover it with a plastick sandwichbag or something like that so the flux does not evaporate and the paste does not dry out.If you look under an microscope can you still see the solderballs "swimming" in flux like in frog spawn or are the solderballs dry?Did you stir for a minute in the paste so it is good mixed?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 10, 2014, 05:31:59 pm
content: You can thin paste with flux if necessary, but as mentioned tubs are usually printing grade, not dispensing, and have a much thicker consistency

author: Simon
author_rank: Unknown
timestamp: April 10, 2014, 05:52:52 pm
content: Quote from: Kjelt on April 10, 2014, 05:23:50 pmswimming ? stir ? that's my point, it's too thick to.

author: Kjelt
author_rank: Super Contributor
timestamp: April 10, 2014, 06:03:06 pm
content: I thought let's make a picture of the two types of paste for Simon since I have both of them at the moment and show you the difference.To my surprise the size of the solderballs for this batch are both almost equal of size (that does not mean yours might not be much bigger as my previous brand was).The big difference is the amount of flux as you (hopefully because my usb microscope is bad quality) can see in the pictures, the paste from the syringe is literally swimming in flux and it is absorbed by the paper while the jar stuff is relatively pretty dry. The reason is that if you use a stencil you want the paste to stay vertically in place and not just collapse and make contact with the other isles of paste.So the solution for you is take a bit of paste from the tub, add thin as possible noclean flux (don't know what kind/brand) and stir till it is slimy.

author: Simon
author_rank: Unknown
timestamp: April 10, 2014, 06:46:22 pm
content: yes it does seem to be a flux versus solder problem.

author: ion
author_rank: Regular Contributor
timestamp: April 10, 2014, 08:02:35 pm
content: Quote from: Simon on April 10, 2014, 10:46:00 amI was a bit less optimistic with the cheap stuff on ebay. The solder ball test seemed to be a quick way to tell if the paste is any good:www.ipc.org/4.0_Knowledge/4.1_Standards/test/2.4.43.pdf?

author: fluxcapacitor
author_rank: Frequent Contributor
timestamp: April 11, 2014, 12:54:17 am
content: I use mechanic branded solder paste from ebay.It i quite solid the first time its opened.I dont keep it in the fridge just in a cool place, then i stir it up with a small screwdriver until its thin enough to use. I use an old syringe from an ink refill kit ,it does the job.

author: macboy
author_rank: Super Contributor
timestamp: April 11, 2014, 02:18:47 pm
content: I would think you can just thin it with IPA, since rosin flux is essentially just solid rosin dissolved in IPA.If it is too thick to stir the IPA into, just add a little (less than a mL), cap the jar, and let it sit for a day at room temp.

author: Simon
author_rank: Unknown
timestamp: April 11, 2014, 03:15:26 pm
content: got some flux from the radiator building shop at work and mixed it in.

author: macboy
author_rank: Super Contributor
timestamp: April 11, 2014, 03:53:17 pm
content: Quote from: Simon on April 11, 2014, 03:15:26 pmYou must use electrical soldering flux. The stuff used for pipes is often acid based and is far too corrosive for electrical work.

author: Simon
author_rank: Unknown
timestamp: April 11, 2014, 03:54:45 pm
content: oh, I thought flux was acid full stop

author: Kjelt
author_rank: Super Contributor
timestamp: April 11, 2014, 05:37:43 pm
content: You gotta be kiddin, i would think it was an april fools joke

author: BrianG61UK
author_rank: Regular Contributor
timestamp: January 17, 2023, 08:42:17 pm
content: Quote from: Simon on April 11, 2014, 03:54:45 pmAs I understand it, they are all acidic, but electrical/electronics flux is only slightly acid and only when it's hot.

author: tooki
author_rank: Super Contributor
timestamp: January 18, 2023, 02:23:38 pm
content: Quote from: Kjelt on April 10, 2014, 08:41:36 amThe size of the solder balls has nothing to do with whether it’s a jar or syringe type. The size is given by the screen size (think sifting): T3 is kinda standard. T4 and T5 are progressively smaller. I think there’s T6, too.For very fine stencils (for tiny pads), you need a finer screen. But you don’t want any finer than necessary, because finer balls oxidize faster (=shorter paste shelf life) and also tend to cause more satellites (little balls of solder after reflowing).

author: Infraviolet
author_rank: Super Contributor
timestamp: January 20, 2023, 01:59:48 am
content: As you mentioend trouble getting the paste to flow, a little tip regarding dispensing, get plastic concial needles rather than metal straight ones. The cone shape is much less prone to jamming up than the long thin region inside a metal needle.

author: tooki
author_rank: Super Contributor
timestamp: January 20, 2023, 07:57:16 am
content: Very true! The conical tips waste more paste (there’s more paste in it when you remove the tip) but indeed make dispensing far easier!

author: Kjelt
author_rank: Super Contributor
timestamp: January 22, 2023, 09:20:42 am
content: Old zombie topic.Plastick vs metal.With my multicore pneumatic / vacuum electronic paste dispenser the metal needle gives a 100% reproducable dispense result. The plastick ones differ but tend to post-ooze paste.Tried many settings longer vacuum post dispense time etc. but the metal needles work te best probably bacause there is less material to retract with the post vacuum.

author: Kjelt
author_rank: Super Contributor
timestamp: January 22, 2023, 09:24:52 am
content: Quote from: tooki on January 18, 2023, 02:23:38 pmYes correct if you can get the different varieties.Remember, this was an 8 year old topic, with for instance Farnell you only had a choice between jar and syringe. That was the difference back then, when I bought a jar it had the larger balls unfit to be dispensed with tiny needles.

author: Watth
author_rank: Frequent Contributor
timestamp: January 22, 2023, 04:27:47 pm
content: What I do to put grease in syringe:Use a spatula-like thing (I bought tongue depressors, they're cheap and have many uses) to put the grease in a small zip lock bag.Close the zip-lock bag and cut a small corner of the bag.Remove the syringe's plunger and press the bag to fill the syringe.