Choosing solder paste and needles - Page 1
Forum section: electronics / testgear

author: sentry7
author_rank: Regular Contributor
timestamp: April 04, 2015, 04:56:49 pm
content: Hey guys,I'm shopping for my first tube of solder paste, and there are lots to choose from. Any suggestions? I'm also working with SMD components, and so, I'm going to need a relatively small applicator, are the needles interchangeable?

author: georges80
author_rank: Frequent Contributor
timestamp: April 04, 2015, 05:18:45 pm
content: Since you're in the US, I'd recommend Kester 256 from the vendor below. Decent price and quick delivery and it's GREAT solder paste.http://www.cmlsupply.com/kester-ep256-lead-solder-paste-63-37-syringe-dispenser/Comes in a syringe and with several tips that work just fine for 0603 size components.Store the paste in a SEALED ziplock bag in the fridge to extend the life.cheers,george.

author: zapta
author_rank: Super Contributor
timestamp: April 04, 2015, 05:23:34 pm
content: I never had luck applying solder paste with a syringe, it doesn't stick to the PCB, so I am using stencils. Do some solder pastes stick better than others?

author: georges80
author_rank: Frequent Contributor
timestamp: April 04, 2015, 05:50:27 pm
content: Kester 256 has "nice" flux (when fresh) and applies nicely to solder pads.cheers,george.

author: rx8pilot
author_rank: Super Contributor
timestamp: April 04, 2015, 07:16:32 pm
content: Quote from: zapta on April 04, 2015, 05:23:34 pmI had the same issue but continued to work on it. The technique is important as is the paste itself. The Kester is easier to work with IMHO. I have some cheap stuff that can get the job done, but harder to deal with. The savings on the cheap stuff is not worth the hassles to me.For me, it was very much worth getting the super fine Type 5 (I think that is right) to be able to push the smaller needles. A big needle can only make big blobs, where a small needle can make small or large. The pressure needed for the smaller needles can be considerable though eventually leading me to buy a pneumatic dispensing system which makes a WORLD of difference when using solder paste. I have and love my stencil printer, but when going through 2-3 rapid revisions of a PCB having a manual paste dispenser saves money and time overall. I can build the PCB in sections, do re-work, and don't have to order and wait for a stencil to arrive that may get used one time.So far, I have been able to get away with doing .4mm QFN's and up. 0402 is normal, QFP's, etc. The QFN's generally have a couple of bridges, but those are easily pulled up with a soldering iron.Short needles are easier to push paste through. Bent needles make it easier to apply under a microscope (highly recommended to use microscope). The tapered plastic needles can get clogged easier, guessing that it packs the balls at the tip. The metal tips are much thinner and generally easier to work with.

author: plazma
author_rank: Frequent Contributor
timestamp: April 04, 2015, 07:59:55 pm
content: I use a very thin and a quite short needle on my paste syringe. The needle have been lubricated with a special lubricant. I have to check the brand and code at work.Without the lubricant it would be impossible to use such a thin needle. Without such a thin needle it would be very hard to manually apply paste to small bga pads.With a pneumatic dispenser and the lubricated small needle it's surprisingly fast to add paste to a 100+ pad bga footprint.

author: rx8pilot
author_rank: Super Contributor
timestamp: April 04, 2015, 09:24:44 pm
content: look forward to hearing more about the needle....is it the teflon coated type?

author: Psi
author_rank: Super Contributor
timestamp: April 04, 2015, 10:17:25 pm
content: Quote from: zapta on April 04, 2015, 05:23:34 pmThe difference i found between using ChipQuic paste vs Loctite paste was like night and day.The Chipquik stuff was awful. It didn't stick to the pads much and keep oozing out of the needle after i let go the syringe.The loctite stuff i bought (its made by multicore, part 583489) was perfect. It stuck to the pads every time.I could go around the board putting daps of paste anywhere i wanted. It also didn't ooze out.I think the difference is to do with the size of the solder balls and the percentage of flux vs balls.For hand work you want smaller solder balls and more flux. This makes it easy to flow throw the needle and sticky so you can put it where you want.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 04, 2015, 10:30:46 pm
content: There are quite a few flavours of paste. The main thing is to use a paste designed for dispensing, not stencilling - the former is more runny and sticky.Another important thing is temperature - if it's too cold, it won't flow and it won't stick - trying to use it fresh from the fridge is hopeless.Old paste can sometimes be revived by adding some liquid flux and mixing thoroughly.I was told by one manufacturer that shelf life is as much to do with moisture absorbtion as temperature, so keeping it sealed, maybe with silica gel, is a good idea.I've found EFD SolderPlus paste has a very long shelf-life (many years) , but IME is hard to buy in small qtys.

author: Bud
author_rank: Super Contributor
timestamp: April 05, 2015, 12:49:34 am
content: Quote from: zapta on April 04, 2015, 05:23:34 pmI have been using Kester 256 for years, hundreds of boards done, good no-clean paste, no issues with non-sticking in about 1 year from purchase date, and that is when I finish the last year supply and buy a new one.

author: zapta
author_rank: Super Contributor
timestamp: April 05, 2015, 01:09:55 am
content: Quote from: Bud on April 05, 2015, 12:49:34 amI have a syringe of Kester 256 from cml, I will give it another try (now using small jars which work better than syringes with stencils)I wouldn't mind to buy a compact power dispenser but the ones I saw require shop air pressure which I don't have at home.

author: coflynn
author_rank: Regular Contributor
timestamp: April 05, 2015, 12:04:04 pm
content: QuoteIt is well worth getting a small compressor. I struggled to use paste reliably with a syringe, but once you get a proper dispenser you can use even year-old crappy paste and still get reliable dot sizes for placing resistors etc. You can see it running here:The small compressor is loud as hell unfortunately when charging, so if you live in an apt. you can't do anything late at night! Larger/more expensive units are supposed to have nicer/quieter motors, but that one was $50.As a side-note, if you haven't seen the Silhoutte Cameo it's a good investment for quickly making stencils, which is also very useful for solder paste dispensing (seehttp://hackaday.com/2012/12/27/diy-smd-stencils-made-with-a-craft-cutter/,I made some more recent notes about what worked for me athttp://colinoflynn.com/2014/11/smd-solder-paste-stencil-creation-with-silhouette-cameo/).

author: rx8pilot
author_rank: Super Contributor
timestamp: April 05, 2015, 05:24:24 pm
content: Quote from: coflynn on April 05, 2015, 12:04:04 pmI got this gem from Amazon. VERY quiet - enough to have right next to you and not be bothered.http://www.amazon.com/California-Air-Tools-CAT-1650A-1-6-Gallon/dp/B00889ZYEC/ref=sr_1_7?s=hi&ie=UTF8&qid=1428254576&sr=1-7&keywords=california+air+tools

author: coflynn
author_rank: Regular Contributor
timestamp: April 05, 2015, 05:46:33 pm
content: QuoteThat's good to know they exist! I run mine in another room, with ear protectors on. It's the crappiest cheapest model, so has a tiny piston and motor which of course means is super-loud.I see they are even on Amazon Canada, unfortunately with recent changes in exchange rate it's not a great value ($250 CAD) for how often I use it right now...

author: SteveyG
author_rank: Unknown
timestamp: April 05, 2015, 08:01:23 pm
content: Quote from: coflynn on April 05, 2015, 12:04:04 pmThat's a nice little dispenser. I guess I need to start looking for something like that in the UK, I already have a silent compressor under the bench for my desolder tool.Nice channel by the way, I've just subscribed - I see you also have the Metcal HCT2-120. I didn't find I have to have mine at 450°C though.

author: M4trix
author_rank: Frequent Contributor
timestamp: April 05, 2015, 08:41:08 pm
content: QuoteYou heard the man. He doesn't need the whole machinery (quiet or loud compressor).

author: skyjumper
author_rank: Regular Contributor
timestamp: April 05, 2015, 10:37:29 pm
content: I have never tried the needle approach, since I have hade great luck with caption stencils. There are several people who will cut them for you from your Gerber files rather cheeply. One guy even included a free plastic squegie. This method speeds application so you have more working time for placement. Most important thing whether you use stencil or a syringe is to make sure your board house puts soldermask between the pads on all components, even those with fine spacing. Not all do and I learned this the hard way.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 05, 2015, 10:54:00 pm
content: Quote from: coflynn on April 05, 2015, 12:04:04 pmI bought one of these a while on a bit of a whim - not yet had a serious play with doing stencils, but for a fairly simple job a while ago, I just exported a DXF from my PCB software & it cut it pretty well. Bit of pain clearing all the holes - sticky tape got most of them but needed some manual poking-out.

author: zapta
author_rank: Super Contributor
timestamp: April 06, 2015, 12:29:47 am
content: Quote from: mikeselectricstuff on April 05, 2015, 10:54:00 pmCan it so let's say 0.5mm pitch qfn?I tried once at work to cut a stencil with a laser cutter but it was not fine enough and I just got one big hole.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 06, 2015, 09:09:58 am
content: Quote from: zapta on April 06, 2015, 12:29:47 amIt would probably need some careful tweaking to get that fine.Should be doable on a laser cutter though - I buy lasercut plastic stencils which do 0.5mm pitch just fine. There was an articke on Hackaday a few days ago about lasering stencils - the trick is to use raster-scan engrave mode rather than vector cuts

author: coflynn
author_rank: Regular Contributor
timestamp: April 06, 2015, 12:27:19 pm
content: QuoteSee attached image - Spartan 6 LX9 TQFP footprint, which is 0.5mm pitch but QFP. This is after I've used the stencil once, and the caps around the side are mostly 0402 size. This is with zero tweaking to file... open gerber in GUI, hit buttons to start cutting. I've cut 0.5mm QFN stencils w/o issue before but don't have any around right now.Only thing to change is cutting pressure depending on the material, but there is a script which makes a bunch of test cuts. Once you dial that in shouldn't need to tweak.You might have to shrink apertures bit of course depending on thickness of material you use, but that would be the same for anything I assume. I'm using Eagle so that's easy to do when generating the stencil layer.Overall I was shocked how well it works, especially from what is a machine for crafting. I had little desire to spend time screwing around and just wanted stuff to come out ready to use, which is basically how it worked for me. The material is key... I mention in my link what I think was 3 mil Mylar Drafting Film from the local craft store worked far better than the transparencies other people seemed to recommend.QuoteMight need more pressure to improve cut through? Alternatively a different material... I've had great luck with drafting film (mylar). Almost all the cut-outs stick to the cutting pad, which can be scraped off easily.QuoteGood to know, thanks for the info! I'll have to play around with lower temps then... had trouble getting things to quickly flow at much lower than say 400. I might have just been impatient however! I think I was overall hoping to magically faster reflowing as their demo video seemed to show, so might have been partially psychological on my side why I wanted it faster ;-)

author: zapta
author_rank: Super Contributor
timestamp: April 06, 2015, 03:51:39 pm
content: Quote from: mikeselectricstuff on April 06, 2015, 09:09:58 amFound it, thanks,http://hackaday.com/category/laser-hacks/and it leads to thishttps://lowpowerlab.com/blog/2015/03/27/laser-etching-smt-stencils-tutorial/.I will try the engraving method.When I used the laser cutter I just tried to cut through. When it failed I just assumed that oshstencils.com, which I often use, has a finer laser.BTW, I prefer 5mil stencils over 3mil (oshstencils supports both) because they print more paste.

author: rx8pilot
author_rank: Super Contributor
timestamp: April 07, 2015, 12:08:08 am
content: I just got some PTFE/Teflon lined needles today. What a HUGE difference! I was able to get the paste through a tiny 25ga needle and successfully hand solder a .4mm QFN without the usual bridges. That is a big upgrade for me. Love these things.It requires way more pressure than practical by hand, so a dispenser is mandatory for these tiny needles. Being able to do small components without a stencil is fantastic though.

author: zapta
author_rank: Super Contributor
timestamp: April 07, 2015, 12:24:18 am
content: Quote from: rx8pilot on April 07, 2015, 12:08:08 amWhere did you get them?Apropos solder bridges, I found the beep mode of this producthttp://amzn.com/B0032JOAWAto be very useful for testing for solder bridges. Also, if two adjacent pads are intended to be connection, I make the connection outside of the IC's outline so it's visible.

author: rx8pilot
author_rank: Super Contributor
timestamp: April 07, 2015, 12:45:10 am
content: Quote from: zapta on April 07, 2015, 12:24:18 amMcMaster Carr 75165A135http://www.mcmaster.com/#catalog/121/3456/=wn2ots

author: neslekkim
author_rank: Super Contributor
timestamp: September 12, 2015, 02:49:09 pm
content: Quote from: rx8pilot on April 07, 2015, 12:08:08 amDoes it exists any guide for sizes of the needles that are usable?, or do you typically use same size for most of the jobs?

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: September 12, 2015, 04:18:57 pm
content: Quote from: coflynn on April 05, 2015, 12:04:04 pmHi coflynn,I have one of those units you showed in your Video lying around for a few years. My father got it from the trash of a dentists workshop that they renovated and I was about to put it back into the trash soon as I didn't know what it was and how to use it, so it was flying around from one corner of the shop to another. Mine is genuine build in germany, but looks totaly identical (except from a broken air connector). Could you send me a instruction manual or tell me how to use that? AND show some pictures of the syringe connector?Thanks!

author: plazma
author_rank: Frequent Contributor
timestamp: September 14, 2015, 08:27:27 pm
content: Quote from: plazma on April 04, 2015, 07:59:55 pmFinally remembered to take a photo of my syringes.I use Nordson ValvePurge for lubing the needle. It makes it possible to use really thin needles even though lubing is not the intended use of ValvePurge.The top most syringes are two different brand fluxes I use.The solder paste syringe got a thin enough needle to paste BGA pads manually.The bottom syringe got some heat activated epoxy. I use it to glue components into place (mostly bottom BGA chips of a package-on-package combo when changin the top RAM chip).

author: rx8pilot
author_rank: Super Contributor
timestamp: September 14, 2015, 08:40:18 pm
content: Quote from: neslekkim on September 12, 2015, 02:49:09 pmI believe there is a whole range of sizes available. I only use the PTFE needles to the fine pitch work so the 25ga is all I have. For larger pads, the steel needles flow just fine so I don't bother with the more expensive and fragile teflon ones.They have been so helpful, really saving some time when I needed it most.

author: KL27x
author_rank: Super Contributor
timestamp: September 14, 2015, 11:02:55 pm
content: QuoteHand solder? Hmm, wonder if you could do that easier with the right iron tip. This whole manual paste thing has me confused. Some very experienced people use it, but it doesn't make sense to me, especially on the ICs. (Other than BGA's, which I have no experience with.)I've seen some very impressive pasting on individual IC pads, but by the time they're done pasting just this one IC, I would have been done placing, soldering, and inspecting the chip. I find the pasting useful for the passives, in particular. If I'm hand-pasting, I'm usually hand soldering the IC's, first, and only pasting the passives, diodes, caps, trannys, etc. If those parts all had gull-wing leads, like an IC, I would never hand paste anything. You can touch a soldering iron tip to a point as fast and easy as you'll ever be able to hand apply solder paste.Even for assembling UQFN leadless protos, I find it most time-efficient to use regular solder. I flux, tin all the pads and "leads," more flux, put the chip on top and then hit it with the rework nozzle. Until I have an X-ray inspection machine, this will probably remain my preferred method for protos.FWIW, I find 18-20 gauge is good for all around use. And the main problem with the plastic needles is they take a lot of paste to prime, which doesn't all suck back into the syringe when done. So when you're done pasting, you lose a bit when you toss the tip and put the air tight cap back on. (I've tried plugging the needle with pins and/or hot glue, but the paste always finds a way to dry out). But they're dirt cheap in quantity and decrease drag.

author: rx8pilot
author_rank: Super Contributor
timestamp: September 15, 2015, 02:19:05 am
content: Quote from: KL27x on September 14, 2015, 11:02:55 pmBy 'hand solder', I really mean paste and hot air. For most of my applications, I have to be very careful not to damage a part. Soldering irons VERY rapidly heat up a joint and then it cools very fast because the surrounding material is rather cold. To place or replace a part that needs to be reliable in the future - I use manually applied paste and a hot air system to delicately do the job.First, if needed, I clean the pads where the part will be placed. Second, I apply the paste. For some parts, I will put a thin line down and for others I will use dots of paste. Next, I place the part itself. The last part is using the hot air system to slowly heat up the PCB, slowly concentrating the heat on to the part until it flows. Then I can slowly ease off the heat. It's not exactly a perfect reflow profile, but it is FAR better than shocking the parts with a soldering iron. For prototypes that only require a short life span, this can be fine. For parts that are going to work long term in the North Pole, it needs to be done gently.I solder with all available methods. Generally, for delicate fine pitch parts I use paste/hot air.

author: KL27x
author_rank: Super Contributor
timestamp: September 15, 2015, 03:49:30 am
content: QuoteIf you say so. I would like to see some data on that before I agree.

author: rx8pilot
author_rank: Super Contributor
timestamp: September 15, 2015, 04:11:19 am
content: I am not making this up, but I am not going to dig up any support for it either. There are a number of good reasons that commercial re-flow ovens have very delicately controlled temperature profiles that conform to the recommendations of the solder and component manufacturers. The manufactures of the solder and components have spent huge amounts of money and time learning how to do it. Contact a manufacturer of MLCC's and ask them what happens to iron soldered caps.If they simply blasted a ton of heat into the parts until the gray stuff melts - they would end up with all sorts of micro-fractures in the silicon and other areas. They might work on the first day, but the life span will be unpredictable.

author: KL27x
author_rank: Super Contributor
timestamp: September 15, 2015, 04:51:56 am
content: QuoteLogically speaking:1.What does this have to do with soldering by iron?2.Reflow ovens have to account for the most heat-sensitive components, of which there are many which are more heat sensitive than typical IC's. Pitch of the leads isn't a factor.QuoteThe silicon is on the other end of a very fine gold bonding wire. Gold is a pretty good conductor of heat, but a wire so thin does not transmit heat very fast. I'm not understanding how applying temperature and duration-controlled heat to the tip of the pins (which is the only place it's actually needed) necessarily has less of a margin for error than applying heat for a longer duration, over a larger area of the chip, while waiting for the entire chip and board around it to reach suitable reflow temp. Shouldn't the "reflow curve" of an iron be much more forgiving, acting directly on pad/pin interface as it does? I would think "blasting a ton of heat" is more descriptive of hot air and oven methods. Which is part of the reason reflow curves are so specific, maybe?Take the gold bonding wire and make it bigger. Let's say that if we increase the dimensions to where the wire is 1" thick, it's now 20 feet long and it weighs 100 lbs. On one end is a heat sensitive square of silicon about a couple yards square and weighs 100 lbs. On the other is a 6' by 1' cross section 1 ton pin. And let's flow it to a huge pad. We can use a finely tuned flamethrower (iron) to heat the end of the pin. Or we can put the whole thing under hot air until the joint flows. Which do you think would have more margin for error?

author: zapta
author_rank: Super Contributor
timestamp: September 15, 2015, 06:11:52 am
content: I got a needle sampler from this seller. Per my request, ge was nice enough to mark the guage of each color so I can reorder by guage #. Below is the picture I took at the time. Anybody knows if the color coding standard?http://www.ebay.com/itm/Blunt-end-dispensing-needles-syringe-needle-tips-1-2-30-pcs-14Ga-to-27Ga-/261457346230

author: neslekkim
author_rank: Super Contributor
timestamp: September 15, 2015, 06:42:13 am
content: I bought from ebay, various sellers, and bought from this place:http://www.proto-advantage.com/store/product_info.php?products_id=1200013All different colors, I was hoping for an standard, but it doesn't seem so..

author: Hellmut1956
author_rank: Contributor
timestamp: March 22, 2021, 10:35:33 pm
content: A couple of years ago I had the need for a way to solder 3x3 mm Ics with 6 pads. It was a temperature and humidity sensor from a swiss company called Sensirion. As I had already built myself the stuff to pass the circuitry printed on an overhead projector foil I had the need to apply solder paste and solder the devices onto the solder pads without creating bridges between pins while applying the device onto the pads.I decided to build myself an oven for reflow soldering. I did purchase an oven for pizzas:https://live.staticflickr.com/4471/37555329470_af54bfcac2_z.jpgAdditionally, I did purchase a multimeter with a temperature measuring function and a sensor that could monitor temperatures above 300° C. As I am sure you all are aware of in the datasheet of a surface mount device there is also a graphic that shows the temperature profile over time:What is interesting in this graphic is to look at the time a device in the reflow process I allowed to be without harm. First I had the intention to have an electronic circuit to monitor and drive the oven along the limits allowed in time and temperature. I was in a hurry so I decided to test if I could match the profile just by looking at the temperature. I succeeded to learn that it was no problem to just monitor visually the temperature on the display of my multimeter. The critical part of the profile is the time the reflow oven will remain in the peak temperature range. I had no problem staying within the allowed boundaries.The second aspect that took me even longer investigation and a learning process was the issue of the soldering paste for the reflow. Soldering paste needs to have a recent manufacturing date as it loses important characteristics that make the reflow process fail. So I had to make sure, besides the production date of the charge of paste, I had also to care about the temperature at which it will melt. Suppliers try to cheat you by delivering older paste or paste with less silver content.The next aspect is related to the needles and the dispenser. The paste is classified depending of the maximum size of the particle in it. Class 5 can be OK. but I did chose to buy class 6, the soldering paste with the smallest size of particles in it. The next aspect is related to the viscosity of the soldering paste when applied. The soldering paste that I got here in Germany comes in a cartridge that is a bit like the dispensing tools you have presented. So if I do remember it correctly the paste had to have a temperature of I think 60°C. At this temperature, it was as easy as possible to apply the paste thanks to its low viscosity.Finally, as I was managing the reflow process manually and visually I did apply paste to a small PCB, put it into the oven, and watched it to find out when it was melting. The paste not melted was opaque, once the paste melt it was brilliant. The temperature where the paste melted was in the range with peak temperature. To ensure it was properly melting, once I had the visual impact that it had melted, I did count from 1 to 10, switched the oven off, and opened the front door of the oven. So it really was not a challenge to reflow SMD parts. But I do like the dispenser shown in the video, I think I might purchase it later.

author: cdev
author_rank: Super Contributor
timestamp: March 22, 2021, 11:10:50 pm
content: Would pine rosin be an appropriate flux to add to old solder paste from the refrigerator?Do any pastes have both a long shelf life and represent fairly good value?Quote from: mikeselectricstuff on April 04, 2015, 10:30:46 pm

author: Hellmut1956
author_rank: Contributor
timestamp: March 25, 2021, 03:30:08 pm
content: @cdev: older soldering paste and soldering paste with a lower silver content are cheaper and can be used if where you plan to use it higher temperatures must be acceptable. if you see my temperature over rime diagram and you see how little time is allowed at a temperature range were soldering paste that is fresh and contains enough silver melts, you see what a critical factor the melting temperature of the soldering paste you want to use.