Cheap newbie solder paste for hot air reflow learning - Page 1
Forum section: electronics / beginners

author: paulca
author_rank: Super Contributor
timestamp: February 21, 2018, 11:07:21 am
content: Hi,So I looked on RS Components and they are either expensive, out of stock or lead free. They are looking for £15-20 for a syringe.Is there a cheaper option anyone knows of in the UK?Is this stuff even likely to work?https://www.ebay.co.uk/itm/MECHANIC-XG-Z40-Liquid-Solder-Soldering-Paste-10cc-Leaded-SMD-BGA-SMT-Stencil/162677306065?hash=item25e052b2d1:g:g4QAAOSwTQtZ75EP

author: ZomBiE80
author_rank: Contributor
timestamp: February 21, 2018, 11:34:31 am
content: That stuff might work. I would be interested to see how your first SMD experience went. When i started, i made my own paste by crushing cold new years tin with a car jack and mixing it with flux.

author: Vic20
author_rank: Contributor
timestamp: February 21, 2018, 11:42:41 am
content: It will probably workI'd recommend to store it, well sealed, in the fridge, when not in use to prevent its degradation, as solder paste expires quite fast compared with normal solder wire.Expired solder paste can be quite nasty.Leave it to come to room temperature for some hours before use.

author: ZomBiE80
author_rank: Contributor
timestamp: February 21, 2018, 11:55:11 am
content: Expired solder paste can be revived with isopropyl alcohol, when used in small quantities.

author: ZomBiE80
author_rank: Contributor
timestamp: February 21, 2018, 11:59:19 am
content: Mostly solder pastes just dries out, but drill it with a pocket screwdriver to a suitable surface, add 2 drops of IPA (and i do not mean beer) and stir... You are ready to go.

author: plazma
author_rank: Frequent Contributor
timestamp: February 21, 2018, 12:05:16 pm
content: Is Locktite GC10 available in small syringes? It ia the best paste I have tried for manual rework.

author: paulca
author_rank: Super Contributor
timestamp: February 21, 2018, 12:53:18 pm
content: Actually while I'm here... can anyone also recommend some good rosin core solder that gets sold on a spool which doesn't cost a fortune?My last ebay off cut has started to become a ball of tangles and is running out. Time to get a proper reel.

author: alanb
author_rank: Frequent Contributor
timestamp: February 21, 2018, 12:57:11 pm
content: Julian Illett was using something cheap in this videohttps://youtu.be/Iid6yahz-dsHe may have said who the supplier was.

author: Ian.M
author_rank: Super Contributor
timestamp: February 21, 2018, 01:17:39 pm
content: If you are just starting out with reflow, you probably want the most forgiving paste you can find. That's going to be a 1st world brand of Sn63Pb37 paste with a no-clean or RMA flux from a supplier that has enough turnover that you get fresh stock. (N.B. Sn63Pb37 is unsuitable for ROHS BGAs)Unless you are only assembling breakout boards or similar small low component count low value PCBs, bad paste could cost you far more in boards and parts (or in rework time and materials if they are salvageable) than you will save by going cheap on the paste, and you wont yet have the experience to tell if the problems are due to bad paste, contamination or poor technique. Once you have some known good paste and enough experience, you can evaluate cheap pastes in comparison to the good stuff, before the good stuff goes out of date.

author: bitwelder
author_rank: Super Contributor
timestamp: February 21, 2018, 01:39:30 pm
content: Quote from: Vic20 on February 21, 2018, 11:42:41 amQuite nasty in what sense?

author: Vic20
author_rank: Contributor
timestamp: February 21, 2018, 01:44:16 pm
content: Quote from: bitwelder on February 21, 2018, 01:39:30 pmSmall solder balls all over the PCB, for instance.

author: Fred27
author_rank: Unknown
timestamp: February 21, 2018, 01:45:48 pm
content: I've used the cheap stuff. It should be fine if you're just playing around. It may be a bit harder to work with with than the good stuff but it'll do the job. I found that adding some flux worked for reviving old paste.Obviously if you want to make your like easier or need a good yield of working boards, then it may be worth spending more on good quality.

author: paulca
author_rank: Super Contributor
timestamp: February 21, 2018, 01:48:50 pm
content: I'm just going to have a play with it. I bought a heat gun, mostly for heat shrink, but I figured I'd have a play with reflow soldering to see if I prefer it to SMD soldering with an iron.

author: plazma
author_rank: Frequent Contributor
timestamp: February 26, 2018, 10:12:27 am
content: Quote from: paulca on February 21, 2018, 01:48:50 pmA heat gun may work but it misses temperature control and a useable selection of nozzles.

author: paulca
author_rank: Super Contributor
timestamp: February 26, 2018, 12:05:22 pm
content: Quote from: plazma on February 26, 2018, 10:12:27 amSorry, it's an 858D clone. So it is temp and flow controlled and comes with 3 nozzles, so I should be grand.

author: tautech
author_rank: Super Contributor
timestamp: February 26, 2018, 01:29:50 pm
content: Quote from: paulca on February 21, 2018, 01:48:50 pmTo add your signature and answer it:You'll blow components all over the PCB. Medium+ heat and little air......use a gently gently approach.I tried air and paste and went back to hand soldering. Too furking fiddly. By the time you've applied pastecleanlyand populated the PCB you'd have them mostly hand soldered !Now, with stensils and a reflow oven..................well, that's a different story.

author: plazma
author_rank: Frequent Contributor
timestamp: February 26, 2018, 01:34:58 pm
content: I apply paste with a tooth pick, place the component and heat it with hot air. Use medium size nozzle and air flow and blow from straight above. The smallest nozzle is useless because it needs too high flow and will blow components away.

author: plazma
author_rank: Frequent Contributor
timestamp: February 26, 2018, 01:36:56 pm
content: I once got good practice at my ex work place. I had to change 67 0402 resistors per pcb. I could fix 6 pcbs per shift.

author: paulca
author_rank: Super Contributor
timestamp: February 26, 2018, 04:05:52 pm
content: Well.... The 858 arrived today, coinciding with the arrival of an SMD practice board. 0805, 0603, PQFP44 all seemed, well, easy!Solder paste applied with a needle in little blobs on each pad. It can be tricky to control the flow rate as the rate it comes out has a lag behind when you apply pressure so you have to keep moving.I got a few bridges on the PQFP44 but I would have got that anyway soldering by hand.A few of them 0805 (out of about 40 of them) tome stoned on me, but I was able to poke them back down with the tweezers.The one thing that does concern me and why I didn't finish the board (another PQFP44, 2x SOIC16, SOT23s and a few MELFs)... is the fumes. The flux off the solder paste has a horrid smell to it, as does the cutting mat under the board when it gets hot. A real nasty platsic acidic smell that I could feel attacking my lungs. So I stopped there.Will need to find an old PC fan to keep a good air current across the desk. I normally get away with when soldering as I use a magnifying lamp which places my nose and mouth away from the solder fumes, but I was using the hot air gun with the jewelers visor thing and even through the gun was blowing it away it was still getting to me.Anyway, I call that a success. Lots got soldered and seem to test on the board via the test pads though I'm not exactly sure what the values should be. Nobody got burnt and the smoke alarm didn't go off.

author: rstofer
author_rank: Super Contributor
timestamp: February 26, 2018, 09:23:41 pm
content: Most of my boards are small (2.5"x3.8") and I can cook them on a hot plate. I just put the populated board on the plate, turn the temp all the way up and wait for the solder to flow. I gently take the board off the hotplate and set it down.I also have a Black & Decker Infra Wave Toaster Oven converted to a reflow oven. It works pretty well.It turns out that I'll be assembling some SMDs this afternoon. I ordered some solder paste from Amazon this morning and it will be here later today.When the pld solder paste turns to clay, I dump the syringe into my Hazardous Waste box and I dispose of it later when I make a HazMat Disposal run. Fluorescent lights, paint, those kinds of things.For today's work I haven't decided which way to go. I just need to solder 2 ICs and 10 0805s. I'll probably use the hot plate approach.I have a hot air gun and have never really used it for anything. There are easier ways to solder things.