best method to remove through hole DIP ICs without overheating? - Page 1
Forum section: electronics / repair

author: jaunty
author_rank: Regular Contributor
timestamp: February 06, 2016, 05:44:17 am
content: I have a severely battery corroded board I made a replica of - but there are some precious no-longer-made DIP IC packages (16 pin or so) that I'd like to save. I started with solder pump then was finishing up the holes with wick... but I'm afraid I probably overheated the last poor little sucker I did... I have some chip-quik on hand... as an option... I know most of you will tell me to get a hot air rework station - but barring that - can you recommend the best strategy for pulling these - in a way that will prevent heat damage?

author: Cloud
author_rank: Regular Contributor
timestamp: February 06, 2016, 06:08:37 am
content: What about holding it with a metal pliers which will distribute away some heat?

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: February 06, 2016, 07:22:52 am
content: Low melting point solder, can't remember a specific alloy.One of those ic shaped solder tips.Preheat the board, flux and new solder, then hold upside down and heat gun.

author: helius
author_rank: Super Contributor
timestamp: February 06, 2016, 07:37:27 am
content: Those are very good suggestions. A corroded IC will not reflow easily, as the corrosion prevents the solder from melting all around the pin. It can be useful to use more aggressive fluxes, or things like aspirin, along with careful bending of the pin during heating. As long as each pin has reflowed completely, removal is simple with any method (sequential solder sucker, simultaneous heating with tweezer or IC-tip, heat gun, or even with a solder fountain)Remember to clean the IC after removal if there could be any corrosive residues.

author: Smokey
author_rank: Super Contributor
timestamp: February 06, 2016, 08:19:51 am
content: I'd be super surprised if you actually thermally damaged a chip in the process of desoldering it with an iron. Unless it's something really exotic like a soft plastic housing that actually melts I would think you would be fine. I can't think of a single time I've thermally damaged a part with a soldering iron. With hot air you can set the temp to not cook things if you're careful, it just takes a while.I have thermally cracked a big QFP with really hot air before, but that's just me being stupid and impatient and not heating it up slow enough.

author: jaunty
author_rank: Regular Contributor
timestamp: February 06, 2016, 10:57:43 pm
content: thanks for the replies.... the SnBi (Bismuth?) alloy stuff sounds intriguing too... the chip quik was driving me a bit nuts seeing as I have nothing like an IC puller. By the time I changed concentration from heating with the iron in one hand and manipulating pliers or anything else in the other hand the solder had already re-hardened...can anyone recommend an IC puller for future use? or is that silly?thanks

author: Refrigerator
author_rank: Super Contributor
timestamp: February 06, 2016, 11:10:04 pm
content: A small butane torch is all you need, just put something under the IC to pry it up as you blast he pins from the other side.That's of course only if you don't need the board any more.I my experience the IC stays cold after popping it out, provided you don't fuss about for too long and pull it right out.But this is a poor man's way of doing things, i'm sure you can come up with something more "elegant".

author: IanB
author_rank: Super Contributor
timestamp: February 06, 2016, 11:13:17 pm
content: Quote from: jaunty on February 06, 2016, 05:44:17 amI had great success removing DIP packages with the Radio Shack heated de-soldering tool. It was a bargain too, only about $10. I don't know if you can still get it.

author: apelly
author_rank: Unknown
timestamp: February 06, 2016, 11:16:39 pm
content: Low temp solder seems common and cheap for model soldier makers. Apparently it's used to solder bits of castings together.

author: KL27x
author_rank: Super Contributor
timestamp: February 06, 2016, 11:16:49 pm
content: I use bismuth/tin alloy when I need to. But with a good solder sucker, I rarely need it on DIP ICs. If you need to "finish" with solderwick, the solder sucking was counterproductive and wick might not work very well on what's left. After solder sucking, the IC should fall out by itself and/or with just a little wiggling on the stuck pins.Good solder sucker = Edsyn Soldapult or clone. While not a complete replacement for, a good solder sucker is worth its weight in solderwick and will work every bit as good as a vacuum desoldering station but with no additional footprint/benchspace/cords. And it will last a lifetime for under $20.00. Even if you have hundreds of feet of solderwick and a $1000.00 desoldering station, there's still no reason to not have a good solder sucker at your disposal. I have purchased a Radio Shack bulb desoldering iron and a ZD985, and I threw them both away. Well, I threw the Rat Shack into the garbage and the ZD into storage. An Edsyn works so well for me that empty space is more useful to me than either of those tools.QuoteSolder sucker and iron, pin by pin, will be less thermally stressful to the chip than a hot air rework station, IMO. But on some boards you may need to use hot air (or torch) because of internal power plane pins that aren't thermally relieved and/or plated thru holes that are super tight. If you run into trouble and are really concerned, you can cut the PCB with a saw and sand it down until the holes are opened. Then heat and pull the pins out one at a time, through the side of the hole.

author: DimitriP
author_rank: Super Contributor
timestamp: February 06, 2016, 11:23:10 pm
content: Quote from: IanB on February 06, 2016, 11:13:17 pmAll the wayI 've been a lot happier with this than with just solder wickhttps://www.radioshack.com/products/radioshack-45-watt-desoldering-iron?variant=5717855877If I was desoldering on a regular basis or had a "desoldering project", I would spring the $ for something with a real honest-to-goodness noisy vacum pump.http://www.amazon.com/Aoyue-Digital-Desoldering-Station-Built-/dp/B00ABJ4AEC/ref=sr_1_5?ie=UTF8&qid=1454800731&sr=8-5&keywords=desoldering+ironAs far as I am concerned when it comes to removing leaded components, any discussion involving hor air, is just that ... hot air.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: February 06, 2016, 11:24:27 pm
content: I've also never killed a DIP IC by overheating.You used to be able to get heatsink clips to put on IC legs on the component side end of the legs, to stop heat flowing to the chip itself.A vacuum desoldering station would be definitely help.--Christoffer

author: arekm
author_rank: Unknown
timestamp: February 06, 2016, 11:33:35 pm
content: ZD985 or ... medical neddle (such one that would slide over pin and inside pcb hole). One by one pin and IC gets easily desoldered with such neddle.

author: apelly
author_rank: Unknown
timestamp: February 06, 2016, 11:47:43 pm
content: Quote from: arekm on February 06, 2016, 11:33:35 pmHoly crap! I donotwant to be on the receiving end of a vaccination in Poland!

author: arekm
author_rank: Unknown
timestamp: February 06, 2016, 11:53:10 pm
content: Hehe, smaller diameter needles are used for thathttps://en.wikipedia.org/wiki/Needle_gauge_comparison_chart

author: KL27x
author_rank: Super Contributor
timestamp: February 06, 2016, 11:55:14 pm
content: I think if there's room for a medical needle between the pin and hole, the part will probably be easy to desolder with regular iron plus either decent solder sucker or compressed air. Neat trick, though.

author: Qmulus
author_rank: Newbie
timestamp: February 07, 2016, 01:18:03 am
content: Over the last 30 or so years that I have been working on electronics I have used just about every method there is for removing through hole ICs. YES, you can easily burn an FR4 PCB. I see it all the time. Burning a PCB can/will carbonize the PCB, which is conductive. Any burned fiberglass must then be scraped out and repaired. On multi-layer boards this damage can be terminal as carbonized PCB in middle layers (often power and ground planes) is almost impossible to repair. I have seen a lot of PCBs destroyed when someone got careless with heat trying to "repair" boards.The best method I have found for through hole components is using regular old SnPb solder and an Edsyn Soldapullt. The key is to first add a bit of solder to each pin first, then heat (no more than 2 seconds unless it is on a ground plane), then immediately suck solder up. If you don't get it clean the first (or second or third) time, add more solder and try again until the barrels are clean. Keeping the pins straight and wiggling them slightly with the tip of the iron helps as well. If the pads/pins are dirty/previously burned/corroded you have to clean them up as good as possible before you start. Once all the through holes are cleaned out, I twist the IC to see if it is loose, repeat the desoldering procedure on any pins that are stuck (or just heat with the iron and pull if it is just one or two - usually on ground planes) and pull out the IC. I can now remove just about any through hole component without damaging the component or the board.You may find that with badly burned ICs where the solder is burned or ICs that definitely do not need to be saved, it is easy to cut each pin off the body of the IC, add a bit of solder, then pluck each pin out one by one with the tip of the iron and desolder with the SoldaPullt (best solder sucker ever!). This method takes a bit longer than just desoldering, but it is safer on delicate PCBs.For what it is worth, I almost never use solder wick when removing components. About the only time I use wick is to clean surface mount pads or remove solder shorts on surface mount parts.For my soldering station, I use a MetCal MX500. I have used lots of different irons, but once I found MetCal I was done. Due to the design, they heat up virtually instantaneously. I have about 20 different tips for the normal handpiece, a Talon (tweezer like tool) that is useful for some surface mount parts and the air powered MetCal desoldering tool. Although it works pretty well, it still isn't as good as a SoldaPullt and is much harder to clean.Just my $.02, YMMV.

author: vk6zgo
author_rank: Super Contributor
timestamp: February 07, 2016, 01:42:20 am
content: Quote from: jaunty on February 06, 2016, 05:44:17 amIn this particular case,where you have a replacement board,you don't need to save the old one.I would cut away as much of the board as I could,so that the amount of heat loss was minimised.Alternatively,heat the PCB with a heatgun,to reduce the work the iron has to do.Some boards make the holes an interference fit,probably to easily retain the components---these are the hardest to desolder.

author: aargee
author_rank: Frequent Contributor
timestamp: February 07, 2016, 12:59:06 pm
content: Solder pots work really well, especially if the board is disposable. The solder bath heats all pins nearly instantly and just pull the chip with some needle nose pliers.Quick and very low heat stress.

author: cdev
author_rank: Super Contributor
timestamp: February 07, 2016, 04:04:32 pm
content: Put an old small HEPA vacuum cleaner on a footswitch and focus its power with a small nozzle. To catch the gobs of solder before they get to the main filter, have the hose run into and then out of a glass bottle or jar trap where its own weight will prevent the solder from going any farther. Put something heavy in the bottom of the jar so it remains were its put. The foot switch (The kind used on industrial sewing machines work great) is the key to making it easy. People really need an extra hand in that situation. Being able to suck solder away by clicking a switch with your foot makes the whole desoldering process much easier.Hand solder suckers are nowhere near as good as a vacuum cleaner.In China sometimes I think they use heated oil in battered old woks to remove chips!

author: gadget73
author_rank: Regular Contributor
timestamp: February 07, 2016, 04:49:00 pm
content: I started using a desoldering gun for stuff, makes short work of it. Mine is a Hakko 808, but they have a newer version that is functionally similar now, FR300 or something. Its basically an iron with an electric vacuum pump in it. I put the tip over the lead until the solder melts, then hit the trigger to pull the solder out. It takes much less time than desoldering wick does, which means a lot less heat into your components.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: February 07, 2016, 05:31:02 pm
content: In theory, theory and practice should be the same. In practice, sometimes they are different.

author: macboy
author_rank: Super Contributor
timestamp: February 07, 2016, 11:26:09 pm
content: I recently acquired a used Hakko 470 which does short work of most joints. I need to get a larger tip than the 1.0 mm I have now, for larger components.I would remind all here that there are two very different reasons to desolder: 1, to remove/replace failed components, which requires saving the PCB, and 2, to remove good/rare/valuable components from a failed board in order to save the component. This is much less common in general but it is the use case for the OP of this thread. One may use very different techniques for the two cases since sometimes there is choice between stressing more the component or the PCB.

author: poorchava
author_rank: Super Contributor
timestamp: February 07, 2016, 11:31:30 pm
content: Blow with hot air gun from below. I've been doing it that way for a long time and haven't killed a single chip.Sent from my HTC One M8s using Tapatalk.