Surface mount !!!!!!!!!!! - Page 1
Forum section: electronics / beginners

author: Unknown
author_rank: Unknown
timestamp: July 09, 2013, 11:56:22 am
content: I really need to learn surface mount, any advice on where to start I have some components, do I need to get a "solder reflow kit", I have a huge magnifying lens on a stand, thought I might start with making a 50 ohm attenuator for my scope, or something like that. any words of wisdom would be appreciated .PaulPS I've just watched this video by Alan excellent

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 09, 2013, 12:19:26 pm
content: what have you? minimum requirement is a soldering iron and solder lead. (i rub my ear coz you shouted too loud)

author: KTP
author_rank: Frequent Contributor
timestamp: July 09, 2013, 01:00:49 pm
content: Here are the essential items you need for smt work:very sharp good quality tweezers (I use some swiss made model..forget the name)flux pen (I use Kester)very very thin flux core solder..not the stuff you would use for connecting copper pipes on your sink.small flat soldering iron tip on quality iron (I use a Weller)Not absolutely required but very very nice is a binocular microscope, 10x and 30x total magnification. I actually solder everything under the scope. Can go cheap here...$200 ebay chinese model.

author: madworm
author_rank: Frequent Contributor
timestamp: July 09, 2013, 01:02:04 pm
content: Thin Sn60Pb40 solder, decent iron, flux (pen / paste), clean tip, practice.

author: Unknown
author_rank: Unknown
timestamp: July 09, 2013, 01:04:50 pm
content: Quote from: Mechatrommer on July 09, 2013, 12:19:26 pmYES I HAVE A VARIABLE SOLDERING IRON, was that loud enough

author: Unknown
author_rank: Unknown
timestamp: July 09, 2013, 01:07:22 pm
content: Quote from: KTP on July 09, 2013, 01:00:49 pmI have all of that except my magnifier isn't that big, so guess I just got to get on with it

author: Unknown
author_rank: Unknown
timestamp: July 09, 2013, 01:08:52 pm
content: Quote from: madworm on July 09, 2013, 01:02:04 pmgot all this except Paste Hmmm, won't go for the wun hung lo type, guessing quality is bets, practice , guess i'll start with small and easy.

author: KTP
author_rank: Frequent Contributor
timestamp: July 09, 2013, 01:44:06 pm
content: You don't need solder paste. If I am placing a 144 pin TSSOP part on a circuit board which has been finished with a hot air knife (so the pads are relatively flat), I will just press the rosin flux pen to all of the pads making sure they are covered. I then position the part using the tweezers, making sure pin 1 is in the correct spotand making sure all four sides are evenly spaced on the pads and that the part pins are centered on each pad on all four sides. I then (under the microscope) touch my soldering iron to the edge of a pad, but not the chip pin. This is why I use a microscope and steady hands...you have about 0.2mm to work with. Usually the flux will start to boil and the residual solder on the pad will bond with the chip pin. If not, you can either try to feed your very fine solder into the pad without moving the chip (tricky) or you can start with a very tiny dot of solder on the end of your soldering iron and allow that to flow into the boiling rosin and pad/pin. You can always go back and reflux/reheat that pin later when other pins are tacked down. I check position of the chip to make sure it has not moved and then repeat the same process tacking down at least the other 3 corners of the chip. I reapply flux from the pen to the chip leads/board pads on the joints I have soldered, then proceed to touch each pad along a side with the soldering iron, boiling the flux and feeding in a tiny bit of solder like you are TIG welding. I can attach a 144 pin TSSOP package this way in about 4 minutes and I know every pin will be correctly soldered with no cold joints or solder bridges.

author: w2aew
author_rank: Super Contributor
timestamp: July 09, 2013, 01:52:00 pm
content: Quote from: Telequipment on July 09, 2013, 01:08:52 pmSolder paste is nice, but it can have a limited shelf life too. Fine gauge rosin core solder will last years (or decades!). I've used paste at work, but never at home. I've also found that liquid flux in a dispenser works great. You can also apply it with a needle or probe when necessary. A good selection of different shape and size solder tips is always helpful. I prefer an iron that has a short working distance (about 2" from finger grip to solder tip). This makes it much easier to keep the iron steady. Definitely a decent lighted magnifier and a nice pair of tweezers. Don't skimp on the tweezers. I've used the cheap ones from Amazon/Ebay, and they're really poor compared to the high quality ones like Janel out of Switzerland.Thank you for mentioning my drag soldering video. This is the prior video that shows hand soldering of an SO-8 package. This shows soldering each lead individually, rather than the drag soldering shown in the video mentioned above.

author: Unknown
author_rank: Unknown
timestamp: July 09, 2013, 02:00:13 pm
content: Quote from: w2aew on July 09, 2013, 01:52:00 pmOh Hello Alan, good advice thank you, it was your video I was watching, there brilliant you know, teaches me lots

author: Psi
author_rank: Super Contributor
timestamp: July 09, 2013, 02:07:43 pm
content: In the first video.. Bonus points to anyone with a good eye who can spot the solder bridge remaining at the end of the video which w2aew doesn't notice. (there are two)

author: AlfBaz
author_rank: Super Contributor
timestamp: July 09, 2013, 02:24:47 pm
content: These blokes make it seem easy. What you don't see in these videos is the tedium of unpacking, identifying, picking and placing the parts that tests your patience.This was my first attempt with 0402 discretes and 0.5mm pitch IC's. I was surprised it worked first time

author: w2aew
author_rank: Super Contributor
timestamp: July 09, 2013, 03:09:38 pm
content: Quote from: Psi on July 09, 2013, 02:07:43 pmGood eye, but no! I thought they were bridges too, but it's just leftover flux that didn't get cleaned out, and looks shiny in the reflection of my magnifier's light. The error that IS in there is that I didn't get my little solder strips lined up right, and there is a little offset between the leads and the pads on the first (far) side that I soldered.

author: madworm
author_rank: Frequent Contributor
timestamp: July 09, 2013, 04:21:56 pm
content: I wasn't suggesting to buy solder-paste, but quality paste-flux - quite a difference!It's just an n=1 study, but from my experience paste-flux sticks around much longer than the flux-pen stuff. Quite important when dealing with unpleasant IC packages, as there's no need to constantly add new flux.But maybe I just have an exceptionally bad flux-pen.

author: MacAttak
author_rank: Unknown
timestamp: July 09, 2013, 05:35:14 pm
content: Don't drink coffee (or other caffeinated drinks/foods) for at least 6 hours prior to doing any smd work. Or for a full day prior if you're like me and sensitive to it.Work in a fairly large, cleared space with a white (or other light colored) surface. You're going to drop a few parts. You're probably also going to squeeze the tweezers too much and fling a few parts around the room. Some of them might not be lost if they happen to land on the work surface in a clear area. But you probably want to keep an extra 20% to 50% parts on hand when you go to make something, at least until you get some practice with it.

author: Unknown
author_rank: Unknown
timestamp: July 09, 2013, 05:37:53 pm
content: Quote from: madworm on July 09, 2013, 04:21:56 pmOK I mis read , I have some flux paste, so later on when it's quite at home I'm going to have a play see what happens, I'm sure it's a practise makes perfect operation. thanks everyone for your pearls of wisdom.

author: WarSim
author_rank: Frequent Contributor
timestamp: July 09, 2013, 07:00:31 pm
content: A flux pen basically contain flux cut with IPA.I personal prefer using liquid flux cut with IPA from a bottle and needle.How much I cut depends on the tasks.Also get the smallest tip for your iron. Even if you do not use it all the time it will be there when you do. It is much better to use the right size, instead of the size at hand. Having to stop mid assembly to wait for the tip you need is aggravating.I don't have PCB 3d render. I missed one hight and made a iron entry gap smaller that intended, had to use an iron tip I didn't have. So I had to either wait for a new tip or disassemble. I tried disassemble and got caught in a catch 22. I have the .4mm conic tip now.

author: Unknown
author_rank: Unknown
timestamp: July 09, 2013, 07:11:16 pm
content: Quote from: WarSim on July 09, 2013, 07:00:31 pmI love all this help, hopefully will stop me making a monumental cock up, so I've ordered some new tips for my iron some liquid flux and a bottle, with a needle on it, all from RS spares , will pick up on the way to work tomorrow.

author: marshallh
author_rank: Unknown
timestamp: July 10, 2013, 03:38:08 am
content: For small passives buy 20% overage when hand assembling. You never know when your nervous hands smack the reel of 0402 caps and the entire thing flies across the room and you inhale the remainder of the parts.

author: WarSim
author_rank: Frequent Contributor
timestamp: July 10, 2013, 05:01:58 am
content: Makes for expensive vacuuming.

author: metalphreak
author_rank: Frequent Contributor
timestamp: July 10, 2013, 12:26:14 pm
content: Quote from: WarSim on July 10, 2013, 05:01:58 amGenerate enough static when vacuuming and my carpet would probably light up from all the 0603 LED's i've dropped over the years...