Solder tip radius for soldering 0402 resistors? - Page 1
Forum section: electronics / beginners

author: ocset
author_rank: Super Contributor
timestamp: May 09, 2018, 07:35:41 pm
content: Hello,We need to solder/desolder 0402 resistors on to 4 layer FR4 PCBs. The 0402 resistors are on minimal pads.Do you know what type of tip is ok for this? Is 0.5mm radius of the tip ok?For example, the following Tenma iron….(Part number 9SS-900N-SI)http://uk.farnell.com/tenma/9ss-900n-si/soldering-iron-of-ss-207b-no-logo/dp/2565327has a smallest tip which is part number 5SI-216N-Bhttp://uk.farnell.com/tenma/5si-216n-b/soldering-tips/dp/2565329?st=5si-216nbWill this be ok for soldering 0402 resistors?The tip radius is 0.5mm, and I believe that will be too thick for 0402’s?

author: PChi
author_rank: Frequent Contributor
timestamp: May 09, 2018, 07:50:56 pm
content: I think that it should be OK in my opinion but it depends on how closely spaced the components are. Also if any of the pads are connected to large planes it's difficult to get heat into the pad without using a high end soldering iron like a Metcal MX-5200 or JBC 245.

author: tautech
author_rank: Super Contributor
timestamp: May 09, 2018, 11:35:37 pm
content: For best heat transfer I'd suggest you look for small chisel or hoof tips instead of conical.For rework you might find K type tips useful as you can bridge both pads and sweep or lift passives from their pads.Have a look here to zero in on the tip shapes available:https://www.hakko.com/english/tip_selection/type.html

author: KL27x
author_rank: Super Contributor
timestamp: May 10, 2018, 12:20:54 am
content: Totally depends on the board, not the component. I solder 0402 with a 3mm TFO bevel tip if the board allows. Just pick up a nice dab of solder on the tip and turn the tip sideways to touch the bottom against the side of the component pad. Whether or not you can do this without reflowing unintended adjacent pads is the question, but since the tip is an oval, it only touches the board at one spot when you hold it like this. You might find there is a lot more clearance than you first think.The problem with thin conical tips like you have linked is that surface tension sucks the solder away from the tip. It only works when you feed solder with your off hand. These are the worse tips for SMD passives. You have to dot one pad with solder, first, then reflow the pad to stick the part, then finish the other side. You are adding a step and wasting a lot of time, IMO. With a minimal pad size and a 3MM TFO bevel, you can solder these parts until the cows come home without having to pick up more solder to the tip. Just apply flux to the board, first, rather than dotting one pad of each component with solder.Small tips are for debugging/modifying a board with fly wires. They are not necessary to rework/populate a board, in most cases. SMD parts and pads are for the most part (other than some connectors) designed to be compatible with wave soldering. The size of that "tip" is very large.

author: ocset
author_rank: Super Contributor
timestamp: May 10, 2018, 05:10:16 am
content: Thanks,Another point, is that we alweays get a number of boards that have dry jointed SOT363's and 0402's....we need to dab at the pads of these to re-wet them, so a nice fine tip (cheap too) for that would be good.Do you know what is the smallest pointed tip radius that you can get?Presumably there is smaller than 0.5mm as in the top post?Weller seem to be the only place that does 0.2mm tips......and with Weller, in order to avoid spending a small fortune, it looks like you have to select the cheapest power unit first, and then choose an iron and tip from there.

author: KL27x
author_rank: Super Contributor
timestamp: May 10, 2018, 05:32:03 am
content: http://uk.farnell.com/tenma/5si-216n-1c/soldering-tips/dp/2565338?st=5SI-216N1mm bevel tip. Yes, I know 1mm > 0.5mm. But bevel tips are cut at an angle and this will be finer and thinner and get into tighter spots than the tip you posted. (Also, 1mm is the diameter of the bevel. (Also, the number on a bevel tip is the diameter, not the radius; hakko, anyhow).If you really want a useless tip, here. The Field of Dreams tip. This looks exactly like what noobs want for 0402. If they make it, noobs will buy it. And add it to the nearest landfill.http://uk.farnell.com/tenma/5si-216n-i/soldering-tips/dp/2565342?st=5SI-216NKnife tip is where it's at for what you want to do, though. Thin and pointy enough to get in anywhere and get down to the edge of nonexistent pads.http://uk.farnell.com/tenma/5si-216n-k/soldering-tips/dp/2565343?st=5SI-216NNotice when you reflow these joints, there's no reason you can't touch multiple pads at once. If you put the flux on there, you won't leave bridges. So even if the surrounding joints don't need fixing, you won't necessarily do them any harmIf you want to see all the different tips they carry for this iron, put "5SI-216N" into the search engine.

author: BillB
author_rank: Unknown
timestamp: May 10, 2018, 03:27:17 pm
content: Quote from: KL27x on May 10, 2018, 05:32:03 am+1 for the bevel or chisel.Field of Dreams tip!so true.