Best lead-free solder paste - Page 1
Forum section: electronics / general

author: Koen
author_rank: Frequent Contributor
timestamp: April 19, 2016, 09:51:21 pm
content: Hello,pursuing my efforts to reduce "production" boards build/verification time, I was wondering if you'd have a lead-free solder paste to recommend ? At this point, quality/efficiency is much more important than price.I've been using ChipQuik SMD291SNL. I'm also using stencils.Thank you very much,KoenI've searched the forum but most threads give importance to wide availability, small volume availability or reasonable prices which aren't issues this time.

author: IconicPCB
author_rank: Super Contributor
timestamp: April 19, 2016, 10:45:14 pm
content: Koen,Good question...Do a bit of reading on more modern alloys such as Sn100Cwww.aimsolder.com/sites/default/files/alloy_sn100c_rev_8.pdf

author: JuKu
author_rank: Frequent Contributor
timestamp: April 20, 2016, 08:43:12 am
content: I haven't used this myself, but a user in my forum said:Quote

author: Koen
author_rank: Frequent Contributor
timestamp: April 20, 2016, 03:59:20 pm
content: Hello,I've added a piece of "LOCTITE GC 10 SAC305T4 885V 52K" in my Farnell cart yesterday. Problem is, I don't know any better so I'm just taking a gamble rather than making an educated choice. We'll see !

author: IconicPCB
author_rank: Super Contributor
timestamp: April 20, 2016, 07:52:55 pm
content: SAC305 is old alloy.Sn100C is a more modern alloywith better performance characteristics in my experience.Sn100C has shown itself to be almost equivalent to Sn/Pb alloy in terms of performance.There is no element of luck with Sn100C.Good luck with SAC305.

author: wraper
author_rank: Unknown
timestamp: April 20, 2016, 08:07:31 pm
content: Quote from: IconicPCB on April 20, 2016, 07:52:55 pmSN100C has 10oC higher melting temperature, so even higher care is needed to achieve that all of the paste melts and parts don't get overheated at the same time.

author: Koen
author_rank: Frequent Contributor
timestamp: April 20, 2016, 09:15:06 pm
content: I need a new lot for monday so I went with an easily obtainable one, for now.I do have a few FPC plastic connectors with levers who need care so I've been trying vapour-phase soldering at 230°C peak on the last few batches.

author: D3f1ant
author_rank: Frequent Contributor
timestamp: April 23, 2016, 04:02:49 am
content: I"m not sure 230deg would be high enough to attain a good intermetalic bond with lead free, it might look ok to the eye but it won't be good bond long term. Most modern connectors are more than capable of withstanding the high temperatures of a leadfree process.

author: wraper
author_rank: Unknown
timestamp: April 23, 2016, 06:42:37 am
content: Quote from: D3f1ant on April 23, 2016, 04:02:49 amIt's the right temperature for SAC305. The advantage of the vapor phase soldering is that all of the parts get heated evenly, so there are no cold spots. Also, as it is oxygen free atmosphere, wetting is greatly increased.

author: D3f1ant
author_rank: Frequent Contributor
timestamp: April 23, 2016, 09:43:56 am
content: I acknowledge I don't have experience with the vapour phase process, but would have thought it would require the same/similar temperature to achieve the correct chemical reaction to form that crucial intermetalic layer between the copper and solder. How the heat is applied shouldn't make a difference, I wouldnt have thought anyway. I'm probably just remembering the chemistry/physics wrong.SN100C is a great alloy.

author: Koen
author_rank: Frequent Contributor
timestamp: April 27, 2016, 02:14:58 am
content: Very happy with GC10 so far, thank you guys.

author: mazurov
author_rank: Frequent Contributor
timestamp: April 28, 2016, 06:36:20 pm
content: My current favorite is Kester NXG1.

author: wraper
author_rank: Unknown
timestamp: April 28, 2016, 06:50:28 pm
content: Got GC10 recently, it's a really good stuff. It can be stored at room temperature too. Warton Metals also have room temperature stable paste Microprint P2010 and it gives awesome soldering results, however it has some drawbacks. First of all it is not even closely as tacky as GC10 therefore parts do not stick to it so well. Also when applied through a stencil, flux/liquid part of it tend to drift to the paste which is left on the PCB through the openings in the stencil, while the remaining paste on the squeegee get drier and drier with each pass. So pain in the ass to apply compared to GC10. Also once applied it tends to dry quickly, therefore if you put a lot of parts by hand, the paste can be almost dry at the end of the job and parts won't stick to it. GC10 doesn't seem to dry out at reasonable time period at all. Left the boards for a few hours, pads seem to be as tacky as when the paste was freshly applied.

author: D3f1ant
author_rank: Frequent Contributor
timestamp: April 29, 2016, 07:39:27 pm
content: Thanks, I going to try GC10 myself now too, room temperature storage sounds appealing, as does the very long abandon time. It looks so shiney

author: cgroen
author_rank: Unknown
timestamp: April 30, 2016, 11:33:11 am
content: Is the GC10 available from somewhere in Europe ? I have not so far found a place that stocks it

author: tautech
author_rank: Super Contributor
timestamp: April 30, 2016, 11:50:51 am
content: Quote from: cgroen on April 30, 2016, 11:33:11 amLOCTITE GC 10 SAC305T4 885V 52KAsk your nearest Loctite agent/stockist to get it in for you.

author: cgroen
author_rank: Unknown
timestamp: April 30, 2016, 11:57:46 am
content: Thanks a lot, I had previously looked at Farnell, but somehow I must have been blind. A search with the exact type you wrote gave a hit from them:Not the cheapest place, but at least its available:http://dk.farnell.com/loctite/loctite-gc-10-sac305t4-885v-52k/solder-paste-t4-halogen-pb-free/dp/2476561

author: Spikee
author_rank: Frequent Contributor
timestamp: April 30, 2016, 10:13:36 pm
content: Quote from: cgroen on April 30, 2016, 11:57:46 am12 may is the date when mine expires. No issues, no mess works good. But.. quite expensive as you need to buy 500 grams.I have about 250 left in mine. Have done about 100 boards or so. If they could make a 250 gram version for half the price than that would be great.I use vapor phase.

author: D3f1ant
author_rank: Frequent Contributor
timestamp: May 01, 2016, 03:02:04 am
content: Don't stress about expiry dates to much, most pastes perform just fine well past the expiry date as long as it hasn't been left open for too long.

author: wraper
author_rank: Unknown
timestamp: May 03, 2016, 11:15:46 pm
content: Quote from: Spikee on April 30, 2016, 10:13:36 pmAs I've seen 250G jars of other pastes, they usually cost about 70-80% of 500g jar, so not too much sense to buy them.

author: harry4516
author_rank: Regular Contributor
timestamp: May 09, 2016, 11:07:53 pm
content: thank so much for the posts,I purchased the LOCTITE GC 10 SAC305.. from Farnell, tested it, and wowww, this is really good stuff.Harry

author: TJ232
author_rank: Frequent Contributor
timestamp: May 10, 2016, 11:55:31 am
content: Using also the LOCTITE GC 10 SAC305 and has become very quick the favorite choice of Pb-free solder paste. Price is higher but quality usually comes with a price...Attached a picture with a fresh new board done with LOCTITE GC 10 SAC305.

author: D3f1ant
author_rank: Frequent Contributor
timestamp: May 12, 2016, 05:30:15 am
content: I ran a few boards at the end of a run today to test GC10, its very stickyIt didnt end up any more shiney than other sac305, so might have tweak the profile a bit, suspect it likes a bit more heat. The sample profiles in datasheet are not very clear but it seems to be fairly flexible.update: Found the 'gc10 engineering manual' which has detailed profile details and sample photos. This stuff does seem to favour longer profiles, but the results are superb.

author: cgroen
author_rank: Unknown
timestamp: May 14, 2016, 05:54:05 am
content: D3,I got my can of GC10 yesterday. Can you maybe share what you have done regarding temp. profile ?I have looked in the "eng. manual":http://www.eis-inc.com/files/pdf/supplier_showcase_page_downloads/loctite_electronics/henkel_ae_gc10_engineering_manual.pdfand page 22 has some various profile examples(PS: about to do my first stencil/paste/oven session)

author: Spikee
author_rank: Frequent Contributor
timestamp: May 14, 2016, 09:05:22 am
content: with the GC10 i use the stock reflow profile of my vapor phase. It tops out at 225-230 or so.Never had any issues.

author: cgroen
author_rank: Unknown
timestamp: May 14, 2016, 12:00:18 pm
content: Thanks!

author: cgroen
author_rank: Unknown
timestamp: May 14, 2016, 04:28:48 pm
content: Well,I have been spending some time with my new china oven and GC10The feelings are a little mixed at the momentI know there is a steep learning curve for this, problem is I'm at the bottom of the curve at the momentI put the paste on a couple of boards and mounted some 0603 just to get started. I used one of the pre-configured profiles in the oven (QS-5100) and the paste didn't even flow.So selected the next profile, and it solderedI then tried the next one to see what would happen with 30 deg more, the picture below is the resultThe profile selected that gave "soldering" success was not quite perfect. I had (almost) shorts on the 0603 components. It seems that there are small "bridges" of solder creeping between the ends of the 0603 resistors creating the short. I'm pretty sure that I did not use too much paste on the pads.What can cause this ? I'm 110% sure that my temperatures and profiles are way off, can any of you give some concrete values you are using, temperatures and times ?The lab here has a smell thats not too comfy at the moment

author: D3f1ant
author_rank: Frequent Contributor
timestamp: May 14, 2016, 07:48:33 pm
content: Looks a little on the hot side.You need at least one, preferably several, thermocouples taped securely with kapton and spread around an unpopulated pcb and measure some real temperatures to do the profiling. A multimeter with a thermocouple probe will do, just mark the temp every 10 seconds on some graph paper.Most ovens report temperature at its sensor, but the sensor isn't on the PCB. There will be offsets and thermal lag, it will vary from board to board. When you get a profile that resembles the recommendations you can try a populated board and tweak accordingly if there is problems.Not in front of the oven to recall the exact profile, but aimed for somewhere between the 2 and 3 profiles given in the engineering manual.Ramp to 180 in 90s, soak for 90s, ramp to Peak 255 then cooling, total time about 6min.

author: D3f1ant
author_rank: Frequent Contributor
timestamp: May 14, 2016, 08:44:23 pm
content: Solder bridges are usually caused by stencil or paste application problems. If the paste is already bridging (or nearly so) before it goes into the oven you can sure of a bridge.Solder paste slumps (ie spreads out) slightly during soak, keep to recommended temperatures.If your hand placing, dont try and get parts perfectly aligned on the pads by sliding them around. If it's miss placed, pick it up and put it down again. Sliding or nudging it around will smudge the paste and increase chance of a bridge. Small parts will float into position due to surface tension. IC's do need to be placed fairly accuratly as they are usually to heavy to float into position.

author: harry4516
author_rank: Regular Contributor
timestamp: May 14, 2016, 11:04:17 pm
content: Quote from: cgroen on May 14, 2016, 04:28:48 pmI am currently using 2min to 185 degC and then 1min to 250 degC.This was my second try and works quite well.A problem of all these ovens are hot and cold areas, so a good fan is mandatory.

author: cgroen
author_rank: Unknown
timestamp: May 15, 2016, 04:21:05 pm
content: Thanks a lot for input guysI have had a thermocouple (and my Fluke) mounted in the oven, and sure enough the temperature is "a little" off, around 40 to 50 degC at the highest temp (oven shows too low temp). The funny thing is that when I selected "profile 3" in the oven, the paste would not even melt, even though the Fluke said 270 degC at maximum...I will need to do some more testing the coming days.Regarding the shorts, D3f were correct, I did "nudge" the components a little, and with further experiments after you wrote your reply I tried again to do the same and I could see the the paste was crawling under the resistorsSo, need to get the temperature correct, at least from the smelly board above I know the oven can reach "high enough" temperatures

author: cgroen
author_rank: Unknown
timestamp: May 18, 2016, 11:36:37 am
content: Now it seems a little more positive hereI will try and experiment a bit more with temperatures and do some measurements of the temperature profiles, but so far its looking betterA pic of two happy 0603 resistors with shiny ends

author: Koen
author_rank: Frequent Contributor
timestamp: May 31, 2016, 03:49:06 am
content: Quote from: D3f1ant on April 23, 2016, 04:02:49 amYou might be right. The solder sure looks dull at 230°C peak compared to GC10 datasheet pictures. I wonder if Galden 240 could help, now to find it...