How to easily cut leads on DIP package - Page 1
Forum section: electronics / general

author: staze
author_rank: Frequent Contributor
timestamp: August 18, 2013, 09:20:20 pm
content: I'm attempting to diagnose an issue with a multimeter that's all through hole, and I'd like to be able to just cut/snip the negative rail lead on a DIP package or two, and am curious what people do. I have flush cutters, but they just ended up mangling the lead (tight space), and an x-acto knife didn't seem to work very well either (lot of "sawing"). Ideally I'd like to cut it so I can solder it back in place should it not be the issue. I've seen one instance of someone using a dremel, but I'm guessing that's more for removal, rather than potentially putting it back.So, what do people use?As a side question, if I remove the negative rail from an op-amp, and power the unit up, is that going to toast the op-amp? Should I ground that "pin" before powering it up so it's got that second "rail" rather than just being open?Thanks!

author: c4757p
author_rank: Super Contributor
timestamp: August 18, 2013, 09:25:29 pm
content: I use flush cutters as well, yours must be shit....Quote from: staze on August 18, 2013, 09:20:20 pmProbably not but possibly. You usually should not remove a power supply connection while other things are connected.

author: robrenz
author_rank: Super Contributor
timestamp: August 18, 2013, 09:32:04 pm
content: This isn't very practical if you don't have the Kapton (polyimide) tubing on hand but I will tell it anyhow. lots of flux on the pin you want to isolate. Use solder wick to remove all solder. Take a piece of kapton tubing that just fits over the dip lead and heat the pin and pad and force the Kapton tubing over the pin and through the board to insulate the pin from the thru hole plating. after testing remove the Kapton and re solder.Typicaltubing link here

author: mariush
author_rank: Super Contributor
timestamp: August 18, 2013, 09:32:28 pm
content: I use nail clippers from time to time.

author: SeanB
author_rank: Super Contributor
timestamp: August 18, 2013, 09:47:55 pm
content: I use a set of cheap flush cutters, and they work well.As to what the opamp will do, it depends on the design. NE5532's were very notorious to oscillate at around 1.6MHz if they lost the supply and still sort of work, 741's just stopped working. Most will just be unhappy and not work, not many will blow up out of spite, except for some chopper amps and comparators that can do so.

author: Dakota
author_rank: Newbie
timestamp: August 18, 2013, 10:00:50 pm
content: I use a pair of Tronex flush cutters and I have never been disappointed.

author: robrenz
author_rank: Super Contributor
timestamp: August 18, 2013, 10:06:51 pm
content: Love those Tronex

author: nanofrog
author_rank: Super Contributor
timestamp: August 18, 2013, 10:18:50 pm
content: Quote from: robrenz on August 18, 2013, 10:06:51 pmSame here!

author: KJDS
author_rank: Super Contributor
timestamp: August 18, 2013, 11:00:43 pm
content: I'll either use a pair of Lindstrom cutters or a scalpel

author: staze
author_rank: Frequent Contributor
timestamp: August 19, 2013, 01:54:21 am
content: I use some Xuron flush cutters, but they have a little added "bit" that holds the piece you cut afterward to prevent it from flying away... wondering if this is what's mangling stuff. Either way, though, the cutters seem a bit too wide to get into the space between pins, so maybe I'll look at something else. They do work great as flush cutters, though. So, just not sure. Was looking at the Hakko ones, or the other sub $25 ones on amazon. Anyone use something like that and like it?But crap, the Lindstrom and Tronex cutters are both pretty spendy. Do you have specific links to them (both produce a few things called flush cutters).I just bought some new x-acto blades, so I'll see if those work a bit better. They're just #11 fine point blades, for "light" use. Metal would seem to be outside of that, but no idea.

author: Someone
author_rank: Super Contributor
timestamp: August 19, 2013, 02:20:57 am
content: Quote from: staze on August 19, 2013, 01:54:21 amGet a Xuron 9200 for the fine work.

author: robrenz
author_rank: Super Contributor
timestamp: August 19, 2013, 02:24:02 am
content: Here is theTronex site. If you are not familiar with all the styles and cutting edge types you should read all the sections of the technology tab, it is a very informative section. These are typically in the $60 to $75 range. Definitely worth every penny but not a necessity if you have other items that are more important.

author: pickle9000
author_rank: Super Contributor
timestamp: August 19, 2013, 02:30:31 am
content: Assuming your cutters are "pointy" enough cutting right at the lead fold point helps. Ideally you will want to leave enough metal on the chip to resolder the lead, this is a troubleshooting operation after all. I hate cutting chips but time and looks are important and cutting a trace is ugly compared to replacing a chip.As for the Robrenz idea, I like it. You can get stainless steel tubes on ebayhttp://www.ebay.ca/itm/Repair-Tool-Set-Flux-Stainless-Steel-Hollow-Pin-Desoldering-Capacitor-Pin-8pcs-/121082071841?pt=LH_DefaultDomain_0&hash=item1c310dcb21.They are very handy for cleaning up holes after the fact. The handles are very crappy but the tubes work just fine.

author: robrenz
author_rank: Super Contributor
timestamp: August 19, 2013, 02:44:59 am
content: Quote from: pickle9000 on August 19, 2013, 02:30:31 amThe reason for the Kapton tubing was that it needs to electrically insulate the pin from the thru hole plating. The Kapton can stand the short solder temperature to displace any residual solder and is extremely thin wall (0.001" to 0.003") so it can fit over the dip pin and still fit in the pcb hole. The stainless tube would be conductive and are typically much thicker wall.

author: pickle9000
author_rank: Super Contributor
timestamp: August 19, 2013, 03:01:00 am
content: Yes I know, the stainless tubes are used to clear an area around a pin. Once clear you can slip on an insulator. I really like the idea or using kapton tubes as an insulator. I normally use nail polish and a couple of nylon fibers to hold the pin free of the hole.

author: robrenz
author_rank: Super Contributor
timestamp: August 19, 2013, 03:10:58 am
content: Sorry,I thought you missed the insulating part. I bought a whole selection of Kapton tubing from .002" up to about .070" from Small parts of Amazon long ago just to have on hand. But it seems they are stocking a lot less of the small lengths and the prices seem to be going up. It is very tricky but you can roll your own kapton tubing from Kapton tape by winding it on a lightly lubed pin of the diameter you want the ID to be and roll as many layers as you want the wall thickness to be then pull the pin out (not easy! even lubed)

author: pickle9000
author_rank: Super Contributor
timestamp: August 19, 2013, 04:36:48 am
content: Robrenz,Rolling tubes sounds very tough, I'll order what I can. I am used to my method 20 years ago we used needle tips from the hospital (did equip repairs for them).

author: dr_p
author_rank: Frequent Contributor
timestamp: August 19, 2013, 07:09:19 am
content: If the hole is not plated through then you can get away with just using wick to isolate it.

author: fpliuzzi
author_rank: Regular Contributor
timestamp: August 19, 2013, 04:36:30 pm
content: This is along the lines of the idea by robrenz for those who can't find Kapton tubing. If you have a plated thru hole with a diameter of at least 0.035" you can electrically isolate an IC pin after you remove the solder from the PTH by using a bit of insulation stripped off of a piece of 24ga CAT-5E "PLENTUM" wire. Here in the U.S. they sell this wire by the foot at Home Depot.The thin insulation on the plentum version of the wire is made of Teflon, so obviously it's very heat resistant. I measured its O.D. at 0.035". This insulation fits snugly onto the lead of an opamp I just test-fitted it on.We used Teflon tubing to isolate IC pins from their plated thru holes when I worked at GE, buy I do not know the source of that particular translucent, light blue Teflon tubing.(I also was supplied a pair of excellent ($$$) carbide tipped angled flush cutters that I wish I had on my home bench now).Regards,Frank

author: robrenz
author_rank: Super Contributor
timestamp: August 19, 2013, 04:47:53 pm
content: The Teflon Spaghetti tubing is an excellent idea. the only drawback is that it is usually thicker wall and not very rigid. So on tighter clearance holes it may not fit.I tried making a piece of tubing using the kapton tape and it was not that hard after all. Wound a piece of 1/4" wide tape around a .020" diameter piece of music wire until it was two layers thick (about .004" wall) and cut it off with scissors. Then I heated the music wire to have the tape adhesive let go of the pin while holding the tape tube in my fingers and slid it right off. the 1/4" length of tube is plenty long to isolate the dip leg. FWIW

author: fpliuzzi
author_rank: Regular Contributor
timestamp: August 19, 2013, 06:02:30 pm
content: Robrenz, thanks for the additional info about making tubing from Kapton tape. I'll certainly will use this idea when I need to produce a thin walled tube that's below the 0.035" O.D. of the plentum wire. I always have plenty of Kapton tape on hand.Regards,Frank