Soldering SMA connectors to pcb - Page 1
Forum section: electronics / beginners

author: medical-nerd
author_rank: Regular Contributor
timestamp: May 04, 2017, 05:28:35 pm
content: HiyaI have development pcbs such as:http://www.ebay.co.uk/itm/Develop-PCB-for-Mini-Circuits-SYM-Series-Mixer-Qty-4-/400805154183?hash=item5d51d94d87:m:mY6k5fjCBY8TbrQDFFFRm3gpic below.I have tried to solder standard pcb sma connectors to these boards, changing iron temperature and trying liberal amounts of flux using standard 60/40 rosin filled solder.I have trashed the board each time due to excessive heat being applied for too long.How do you do this successfully?CheersSteve

author: CJay
author_rank: Super Contributor
timestamp: May 04, 2017, 05:33:01 pm
content: Test the SMA connectors will take solder.Your iron needs to have lots of heat capacity and the power to be able to maintain the tip at a set temperature, it's not enough to be able to turn the temperature up, what iron are you using?.

author: medical-nerd
author_rank: Regular Contributor
timestamp: May 04, 2017, 05:37:40 pm
content: I'm using an Antex 690SD with a 50W iron

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 04, 2017, 05:52:48 pm
content: How have you trashed the board? I try to start with the connectors as first component on your board. You do need a /good/ iron for this - anything else will be a pain to work with. Take your time. Let your iron really heat up everything well, and let everything bathe in flux. Flux is key to have to solder connect nicely to the connector.I've soldered may SMA connectors and never trashed a board.

author: Bud
author_rank: Super Contributor
timestamp: May 04, 2017, 05:57:53 pm
content: You should get a soldering iron with good thermal mass, it is unclear from the photo what that iron is. If you do not have one, find a way to preheat the board before right before soldering a connector.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 04, 2017, 06:06:57 pm
content: I would also like to quickly point out that those boards seem to have a very strange footprint and not at all what I'm used to seeing with edge-mount SMA connectors. Take this for example, from a board using SMA connectors I'm working on currently:

author: medical-nerd
author_rank: Regular Contributor
timestamp: May 04, 2017, 06:08:44 pm
content: HiyaI tried the connectors first as I didn't want to damage the mixers as I assumed that the connectors would absorb a significant amount of heat that might be dissipated through the board.The connectors do take solder - I tried 'tinning' them after my first attempt, but the solder layer then made the gap between the two sides too small to then fit onto the board. I tried to increase this gently but this snapped them.After my attempts the board was significantly discoloured as thought it had been burnt or exposed to a fire.Cheers

author: CJay
author_rank: Super Contributor
timestamp: May 04, 2017, 06:14:58 pm
content: I'd try it with the largest tip you have, don't wind the temperature up, just use whatever you'd set it for when working on a normal board, the controller and heating element should have enough power to keep the tip hot, if they don't then it's time to consider a new iron.These SMAs were done with nothing more than 60/40 Ersin Multicore, an old Weller thermostatic iron, no fancy temperature control but it does have bags of power and a chunky 3.2mm tip so it's got lots of heat capacity and the power to maintain it at temperature.

author: edpalmer42
author_rank: Super Contributor
timestamp: May 04, 2017, 06:17:34 pm
content: I totally agree with the other posters. You need a BIG iron. It's much easier to burn a board with a small iron than a big one. The big iron will hold the heat and raise the temperature quickly so you can melt the solder and go. A small iron takes a lot longer to heat the joint and the board suffers.Do you have an old soldering *gun* like a 100 watt Weller or similar. Try that. Otherwise, start looking around your local hardware stores.This one is probably overkill, but you get the idea.Ed

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 04, 2017, 06:18:50 pm
content: Quote from: medical-nerd on May 04, 2017, 06:08:44 pmIs it the actual board, or the flux? I've seen fluxes that turn all kind of horrible colors after a while, but when you clean the board after, it looks clean again. I've soldered all of mine with a weller 80w station with a 2.4mm chisel, set to 300C

author: medical-nerd
author_rank: Regular Contributor
timestamp: May 04, 2017, 06:59:02 pm
content: I'll give the board a thorough clean.I've been using a 1mm tip, which I now realise was too small. I have a few much larger tips to use.Seems that I was blinded by being too scared about damaging the board,If that doesn't work I'll get a cheap beefier iron for these.Many thanks to everyone for your excellent advice.

author: mmagin
author_rank: Frequent Contributor
timestamp: May 04, 2017, 08:05:41 pm
content: You don't necessarily need a large iron, but I would suggest at least a 3 mm or larger chisel tip on a 50+ watt iron that can quickly respond to the thermal demand. Every time I see people say to use a huge iron, I realize that a lot of people haven't used a really good modern soldering station.I've done these kinds of things easily with my old Metcal and a Thermaltronics M6LC650 5 mm chisel tip.Also, be sure to have the iron on the connector body, the pads on the board will get plenty of heat through it.

author: KL27x
author_rank: Super Contributor
timestamp: May 04, 2017, 09:23:31 pm
content: QuoteUnless it's a Metcal, there are times you need a huge iron. To a lot of people who have only ever used the default conical tip that came on the thing, a 3mm chisel tip IS huge.No iron can make up for tip size by response/power. The Metcal comes close. When you are soldering a huge thermal mass joint, there's nothing wrong with using a larger tip AND setting the temp higher. As high as you need. The initial tip temp + tip mass is a major factor in the equation. Where this number is not enough is when you need to start adding board heater or other strategy. Doesn't much matter how high the temp, other than the drawbacks of oxidizing the tip and burning up the flux. This is why we set the irons lower, most of the time.

author: medical-nerd
author_rank: Regular Contributor
timestamp: May 04, 2017, 09:50:58 pm
content: Would something like this be sufficient?ANTEX HP100 100W soldering iron'A general-purpose soldering iron from Antex. Ideal for industrial repairs and electrical work where a large tip mass is required'Its only £17, a replacement iron for my soldering station recently cost me £80 after I cracked its element after I unfortunately dropped it - separate elements are not available,

author: tautech
author_rank: Super Contributor
timestamp: May 04, 2017, 10:26:07 pm
content: Quote from: medical-nerd on May 04, 2017, 09:50:58 pmThat will more than likely do it but try your biggest and chunkyest tip with your station first.Make sure for jobs like these you also use PB solder, not that PB free muck.Low temp silver alloyed solder is good to have on hand for jobs like these too.

author: edpalmer42
author_rank: Super Contributor
timestamp: May 04, 2017, 10:51:22 pm
content: An iron like that is good to have around for big jobs like soldering on ground planes, desoldering, connectors, etc. But, of course, try your biggest tip first.Ed

author: DimitriP
author_rank: Super Contributor
timestamp: May 04, 2017, 11:01:11 pm
content: All these comments about a "big iron" make me feel like i've lived in the twilight zone. .I used to solder RG-8 coax on PL259 connectors using a 15 watt antex iron.But not with a 1mm conical tip!Use an 1102, 1109 or 1103 tip and it will make all the difference in the world.

author: tautech
author_rank: Super Contributor
timestamp: May 04, 2017, 11:10:39 pm
content: Quote from: DimitriP on May 04, 2017, 11:01:11 pmI inherited an Antex X25 (25W) and they most certainly box well above their weight.It's my goto "outside job" iron and probably will whip the 55W station on my bench but sadly the X25 has no real temp control so back to old school techniques when using it.

author: KL27x
author_rank: Super Contributor
timestamp: May 04, 2017, 11:52:56 pm
content: I have soldered similar connectors made from what looks like solid brass using a 65W hakko. But the PCB is the unknown variable. A thick ground pour with non-thermal pads can stump anything short of a metcal or preheater. Some boards are just meant to be oven reflowed. Until I've turned the dial all the way to the right, I wouldn't be buying a new iron for just a few boards, though. At that high of a temp, just make sure you clean and tin the tip exactly right before you attempt the joint.

author: CJay
author_rank: Super Contributor
timestamp: May 05, 2017, 07:00:33 am
content: Quote from: tautech on May 04, 2017, 11:10:39 pmThe original X25 (red handle right?) was and still is an excellent iron, I think I have one somewhere, I was persuaded to try the Weller W60D at a new job many years ago and never looked back, now I have several Wellers, all Magnastat types.I can believe you can solder RG8 into a PL259 centre pin with a 15W Antex, I think I've probably done that but I'm afraid I don't believe you can solder the screen of the coax to the body of the plug with one, you may be able to 'pigeon shit' solder onto the screen but not make a proper joint.

author: CJay
author_rank: Super Contributor
timestamp: May 05, 2017, 07:21:57 am
content: Quote from: medical-nerd on May 04, 2017, 09:50:58 pmIt's overkill, it'll work but you're missing the point and there's a very good chance you'll kill just as many boards, what you need is controlled temperature and thermal mass combined with available power to maintain the temperature.This is what I use (mine is ancient, it's dated 1980 something I think so it must be an earlier version):https://www.amazon.com/WTCPT-Temperature-Controlled-Soldering-Station/dp/B00004W463As mentioned earlier, try the largest tip you have, you've got at least one trashed board to practice on now so before you dig out a new board, experiment on that, scrape off the solder resist and try to tin the board.In my experience (and I know this will provoke all sorts of posts to the contrary) for soldering this sort of connector and board you *never* need more flux than that contained in the solder. Hell, I only *ever* add flux if I'm reworking SMD.Another board, sitting on top of the reel of solder used and soldered with my Weller, no extra flux and just a No.6 3,2mm tip, the board hasn't even been cleaned:

author: onesixright
author_rank: Frequent Contributor
timestamp: May 05, 2017, 08:28:26 pm
content: Use Metcal.

author: grifftech
author_rank: Frequent Contributor
timestamp: May 05, 2017, 09:03:52 pm
content: Quote from: edpalmer42 on May 04, 2017, 06:17:34 pmHOW MANY WATTS IS THAT!!!

author: edpalmer42
author_rank: Super Contributor
timestamp: May 05, 2017, 10:49:17 pm
content: Quote from: grifftech on May 05, 2017, 09:03:52 pmI'm not sure which one that is. They go up to 550 watts.https://americanbeautytools.com/Soldering-IronsEd

author: BMack
author_rank: Regular Contributor
timestamp: May 06, 2017, 03:46:38 am
content: Like others said, biggest tip you can fit. Bigger the tip, the better it holds in the heat and transfers the heat. High heat isn't needed with 60/40, just a good sized tip and flux.

author: wkb
author_rank: Super Contributor
timestamp: May 06, 2017, 09:03:48 pm
content: Fully agree!! No need for fusion-power irons, a Metcal will get this job done easily

author: max_torque
author_rank: Super Contributor
timestamp: May 07, 2017, 09:57:10 am
content: Just go an get a cheap DIY style hot air gun, the sort of thing used for paint stripping and other similar diy tasks. Ideally,, get one with two heat settings.Use this to heat up the pcb and connectors to around 100degC, then you'll find you can just solder everything together easily with a normal iron!(be careful, do not hold the hot air gun too close or in one place for too long, it will toast the pcb! Use it to warm the whole lot by holding it about 12" away and moving round in constant circular patterns. After a couple of min heating (you'll quickl get a feel for how long things take to heat up) put the hot air gun down, break out the soldering iron and solder away!)

author: janoc
author_rank: Super Contributor
timestamp: May 07, 2017, 01:32:58 pm
content: Quote from: wkb on May 06, 2017, 09:03:48 pmAnydecent station will do this easily. I have soldered both SMAs and BNCs to boards with my ERSA i-Con Nano, using a 2 or 3 mm chisel tip.And even your favourite Metcal will suck at it if you use a 1mm conical tip, as the OP attempted. Conical tips are pretty much useless for most soldering because they make it very difficult to transfer heat to the joint.