Weller non-wettable tips ?  - Page 1
Forum section: electronics / projects

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: November 13, 2016, 06:25:22 pm
content: Hello All,In the catalog of weller tipshttp://www.weller-toolsus.com/MagentoShare/media/mannuals/Soldering_Tip_Brochure.pdf,the thinest ones are "non-wettable" (RT1NW for example).What does it mean ?What are they used for ?I am in fact looking for the thinnest tips, so they can go between the pins of a 0.5mm chip to remove solder bridges.

author: wraper
author_rank: Unknown
timestamp: November 13, 2016, 06:59:26 pm
content: Quote from: JacquesBBB on November 13, 2016, 06:25:22 pmThat is not a proper way how to remove the solder bridges.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: November 13, 2016, 07:49:53 pm
content: Quote from: wraper on November 13, 2016, 06:59:26 pmI am sure someone would say that. But you should also provide the proper way to remove them, otherwise your comment is not very useful.In my case, I put a lot of flux, tried solder wick, but it did not work (this was a 100 pins 0.5mm chip). The problem was that the solder bridge wasdeep inside, close to the chip. Otherwise I can remove bridges just with the plain clean iron.

author: 2N3055
author_rank: Super Contributor
timestamp: November 13, 2016, 08:07:20 pm
content: Quote from: JacquesBBB on November 13, 2016, 06:25:22 pmMeans exactly that, non-wettable... Meaning they will not take solder, but work only by contact thermal transfer.... They are so small that smallest amount of solder would change it's size...They are not to be used for what you need..Also wick works by capillary action and therefore surface tension.. surface tension under the chip is obviously stronger so it won't go into the wick.. Maybe a vacuum pump...For 0.5mm raster, you can use pre-tinned boards and use only flux.. That tin on board is more than enough to solder on.. Or you can go one pass with solder tip, wick and again put flux...

author: wraper
author_rank: Unknown
timestamp: November 13, 2016, 08:20:26 pm
content: Quote from: JacquesBBB on November 13, 2016, 07:49:53 pmThe best would be using miniwave / MicroWell tip. But regular chisel tip can be used too. The trick is not trying soldering pins one by one but moving a solder blob to the end of the row of the pins, or outwards from the chip.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: November 13, 2016, 08:28:15 pm
content: I know this video. Very good video. I even posted it here on another thread.I have also the same Weller RT10GW tip. All this work very fine. But in the present case, I was changing the MSP432 on a Ti board, withnot much space, and some solder went under the pins, close to the chip.I was not able to remove it, either with the method mentioned in the video, or with solder wick. or with a fine tip (Weller RT1) which was not fine enoughto reach the solder.This is why I looked for an even thinner tip.

author: wraper
author_rank: Unknown
timestamp: November 13, 2016, 08:39:37 pm
content: Quote from: JacquesBBB on November 13, 2016, 08:28:15 pmEither there is a problem with your soldering technique or those pins have high thermal mass. In second case you should preheat the board. Thin tip won't save your day.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: November 13, 2016, 08:55:01 pm
content: Quote from: wraper on November 13, 2016, 08:39:37 pmI certainly can improve my soldering technique. This is what I am trying indeed. I have not much experience in 0.5mm pitch soldering.As a matter of fact, I have preheated the board. Also to remove the original chip with hot air, I preheat the board with a hot plate at about 90 C.

author: kxenos
author_rank: Frequent Contributor
timestamp: November 13, 2016, 09:04:31 pm
content: I'm afraid you will have to desolder the chip again. I haven't been able to find any other way. The last 5-7 years I use 0.5mm solder and a pen flux and I haven't had this issue since

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: November 13, 2016, 09:21:39 pm
content: I have already desoldered the chip. Indeed, there was too much solder close to the chip.I have cleaned everything, and tried again. It was much better, but still some small issue. But unfortunately, I lifted a trace and torn a pin. Probably too much stress on the pads. I think this board is really dead now, but I could try again with another one.

author: nctnico
author_rank: Super Contributor
timestamp: November 13, 2016, 09:23:27 pm
content: Quote from: JacquesBBB on November 13, 2016, 07:49:53 pmFor these situations you need a big tip and add extra tin to engulf the bridge and then use solder wick to remove the whole lot. But it is tricky and may take a couple of tries.

author: Pjotr
author_rank: Frequent Contributor
timestamp: November 13, 2016, 09:43:58 pm
content: B.t.w. do somebody already have any idea why Weller sells "non-wettable" tips and what those are intended for?

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: November 13, 2016, 10:40:26 pm
content: Thanks for going back to the original question, even if all the other discussion is interesting.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: November 13, 2016, 10:54:35 pm
content: Meanwhile,I have tried again on another board, and this time, although the placement was not perfect, the soldering was fine andthe board is working.So the discussion was useful, as it pushed me to try another time.Do you have any trick to place properly the chip ? I find it not obvious with these 0.5mm pitch chips.

author: 2N3055
author_rank: Super Contributor
timestamp: November 13, 2016, 11:13:50 pm
content: No just microscope and patience.. I have good precision with tweezers, two of them both hands... Vacuum holders don't work for me... I put flux on board (rosin type, no clean) and is sticky enough to hold it in place , tack diagonaly and then solder the lot....

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: November 14, 2016, 12:06:55 am
content: Quote from: 2N3055 on November 13, 2016, 11:13:50 pmMicroscope ... Maybe this is where I could find some improvement. I am just using a lousy 5$ magnifierlike this onehttp://www.ebay.com/itm/Third-Hand-Soldering-Solder-Iron-Stand-Helping-Magnifying-Tool-Magnifier-HS-/111707154760?hash=item1a0243e948:g:FrkAAOSwDNdVkebaNot always very practical. Up to 0.65mm, it was OK. But I find that there is a gap from 0.65mm to 0.5mm.

author: 2N3055
author_rank: Super Contributor
timestamp: November 14, 2016, 12:24:23 am
content: Quote from: JacquesBBB on November 14, 2016, 12:06:55 amOh yeah, get a microscope, it will change your life.. trust me.. Stereo microscope will give you proper depth perception, and no need to go crazy with magnification 10X is what I use most of the time..

author: nanofrog
author_rank: Super Contributor
timestamp: November 14, 2016, 03:34:19 pm
content: Quote from: Pjotr on November 13, 2016, 09:43:58 pmFWIW, I've seen such types used for melting the ends of plastic posts into rivets (slide PCB onto posts, then melt the ends of the posts).If there are other uses, I'd like to know as well.As per pulling out bridges, a very fine point bent conical does wonders as well IME.

author: Pjotr
author_rank: Frequent Contributor
timestamp: November 14, 2016, 05:10:31 pm
content: Found this on a RS DesignSpark application page which agrees with OP assumptions:"Gullwing, bucket or drag solder tips can make short work of surfaced mount components allowing multiple pads to be soldered whilst preheating the next allowing a “drag” of solder across more pads. The same tip can be used for cleaning up as the bucket can be used empty and will pull excess solder from potential bridges.Any further bridges can be removed with non wettable tips which won’t stick to components."https://www.rs-online.com/designspark/soldering-choosing-the-right-power-and-choosing-the-right-tip

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: November 14, 2016, 06:07:18 pm
content: Thanks Pjotr for quoting this,Looks like my question was not that stupid after all. My aim was indeed to remove solder bridges where the other methods (using the clean gullwing tip orsolder wick) had failed.

author: Pjotr
author_rank: Frequent Contributor
timestamp: November 14, 2016, 07:28:35 pm
content: My experience with bridging is that it is caused by heating the solder too long and/or lack of flux. Heating too long generates a lot of oxides that make the solder a sticky mixture. Difficult to remove. My remedy is to ad a lot of extra clean solder to "the place of accident" and then remove all the excessive solder with wick. Most time the oxide poisoned solder is then taken away with it and bridging cleared.

author: KL27x
author_rank: Super Contributor
timestamp: November 14, 2016, 08:16:48 pm
content: Tinned face-only bevel tips changed everything for me. I don't know if Weller has the same thing. For my hakko, it is T18-CF3. 3mm bevel tip with chrome jacket over the sides so only the face can hold solder. (I have them in all sizes, but 3mm is best for drag soldering and bridge removal, IMO).On a shoulder bridge, you touch the iron to the top of the pins by the chip and slide the tip down off the end of the pins. It sucks like a hoover. But unlike a conical, chisel, or regular bevel, the solder doesn't wick up the side of the iron where it must be wiped off. It forms a thin meniscus on the bottom of the iron, so you can put it back on the board where it is supposed to go. This sounds counterintuitive, but it works like black magic. Some kind of surface tension and gravity thing going that pulls/keeps most of the solder on the cut face of the iron and gives/leaves just about the right amount on the pads... as long as you have roughly the right amount of solder on there to begin with. This is why the 3mm works best... larger surface area makes it more forgiving and able to deal with larger amounts of solder; but the 4mm is too big (too large to maneuver for one thing. But it is also too large to hold a huge drop of solder... the surface tension isn't strong enough to hold the drop that forms when you get larger than the 3mm; and this ability is useful for other things like hand soldering of passives and SOT23 and the like; so while it can hold a wee bit more solder than the 3mm, it is easy to add too much and drop the bead, and it is not worth the decrease in maneuverability.)Other major benefit is the entire wettable surface can be kept with a layer of solder most of the time under use, on the bottom face where gravity naturally pulls melted flux. So the tip rarely needs cleaning. If you keep things moving, you don't have to stop to clean the tip, ever.The nonwettable tips sounds like they might be good for removing bridges post oven-soldering where the amount of solder is very small; where it doesn't have to be removed, just moved. If you're hand soldering to begin with, it is just an extra step...

author: nanofrog
author_rank: Super Contributor
timestamp: November 14, 2016, 09:43:27 pm
content: Quote from: KL27x on November 14, 2016, 08:16:48 pmFWIW, they do in the LT series at least (3mm & 4mm, and I've both). Definitely great tips to work with IME as well.