Attaching wires to an ICs on a mainboard (breakout board?) - Page 1
Forum section: electronics / general

author: analogix
author_rank: Frequent Contributor
timestamp: April 06, 2017, 12:26:51 pm
content: I need to attach some wires to a couple of ICs inside a vintage computer and hope to find some vias I can solder them on. Failing that, what's the best way to attach wires without being messy (e.g. soldering directly to the IC pins) or soldering underneath and having long wires go all the way around the computer's PCB? One of the ICs is socketed (24 pin, not sure if it's a normal or "narrow" type, but can check -it's a PAL22V10), the other one is a 20 pin IC (74F244) which I assume is a standard 20-pin DIL type IC.I've heard of "breakout boards" which I was expecting to be small PCBs with a long-legged IC socket, allowing for the IC to go on that board, and plugging it into the computer's IC socket, then getting solder pads/holes for attaching wires to any of its pins, but contrary to what I'd expect I haven't had any success finding anything like that online. Suggestions?

author: @rt
author_rank: Super Contributor
timestamp: April 06, 2017, 12:43:20 pm
content: That’s not really what a breakout board is. They usually just lead out the IC footprint to pads of better pitch for hand soldering.If you could get an unpopulated one, there are IC sockets with long legs you could use with it, so long as the computer’s ICs are socketed.It isn’t so bad to solder to the IC leg if the mod is permanent. The GALs are programmable arrays, so keep the dwell time low.The chips aren’t replaceable.

author: Nusa
author_rank: Super Contributor
timestamp: April 06, 2017, 12:49:44 pm
content: Temporary or permanent wires?If it's permanent, and if the wires are routed neatly, it's not that messy to go directly to pins. Remember you can do it on either side of the board, since I assume you're talking about through-hole tech. The backside is often easier than the front for many things, and may not be visible at all when you're done.

author: Ian.M
author_rank: Super Contributor
timestamp: April 06, 2017, 12:54:25 pm
content: --- Topside permanent mods ---Soldered chip: Clean pin shoulder with fibreglass brush, solder Kynar wirewrap wire direct to the pin.Socketed chip - find a high clearance turned pin socket, solder Kynar round the increased diameter base of each pin, then insert it between the chip and the board socket.Both are often neater than trying to pick up the signals at vias as the vias can be all over the place.In both cases it may be helpful to use two SIL strips of turned pin sockets as a plug and socket to allow the mod to be disconnected without soldering or cutting wires - you can solder wires into the socket end of a turned pin SIL strip to use it as a plug. Superglue the socket side of the connector down somewhere convenient e.g. on its side on top of the soldered chip, or to the side of the turned pin socket under the socketed chipDon't run wires from the bottom side unless you can keep them short and protect them where they go round the board edge. if there's space to do the whole mod bottom side, OK but otherwise best avoided.When it comes to mounting mods, 3M foam VHB tape is your friend - there's nothing worse than a mod board coming loose and shorting out,

author: analogix
author_rank: Frequent Contributor
timestamp: April 21, 2017, 11:07:52 pm
content: I decided to do it simple and soldered wires carefully directly to the TTL chip's pins.I read somewhere about using flux to ease soldering so I tried it out for the first time, putting a little bit (Weller LF-25 "soldering grease"-I hope I got the right type as I read somewhere about certain types with acid in them used for soldering water pipes etc. and not electronic components, which can in time destroy PCBs and components) on the IC pins and quickly soldering the wires. The solder seemed to flow easier, so I guess I did something rightFor the PAL chip I didn't want to solder directly on to the IC and I didn't have any wire wrap wire (truth be told I don't have any experience with wire wrapping), so I simply stripped a regular wire, tinned it ever so slightly and carefully wrapped it around the uppermost part of the IC's leg, finally covering it with a heat shrink tube (see image attached). I don't know if this is the best method though as I can't seem to get it to stay tight (it moved around when I moved the wires as I connected the other ends to their respective connectors).I had a quick look for "kynar" on eBay and foundthis. Are we talking about an insulated type of wire which is to be stripped, then the un-insulated wire is to be wrapped tightly around the IC's leg as you suggested, and will sit tightly unlike the regular electrical wire?I gave up soldering a wire to a via as they were so small -it'll probably be hard to get a strong connection and I fear the wire may get loose and rip up the via.As for turned sockets -did you that I geta wire wrapping socket like this, wrap a wire around the socket pin in question, "sandwiching" the wire between that wire-wrap socket and the existing socket? That sounds like a good idea except I found out that there is very little clearance above the socketed IC (there's another PCB a few mm above, partly covering the IC), so I can't raise it any further. But would wrapping Kynar around the IC's leg, then re-inserting it into its socket do a similar job?I looked up 3M VHB tape but here it seems to be available only for industrial use, besides there are many different types of VHB tape -which one are you referring to? Is it a special type of tape or will any "foam" type of tape hold loose circuit boards/modifications in place? I probably have to look for something else, or see if they have it on eBay or something if that's what will work.

author: Ian.M
author_rank: Super Contributor
timestamp: April 21, 2017, 11:42:23 pm
content: As log as you are *certain* that the flux you used was acid and halide free, great. However if you've used plumbers flux containing Zinc chloride, Ammonium chloride or other chlorides, you've just put your board on death row. The product description:Quotemeans you've almost certainly screwed the pooch as that DIN code specifies Ammonium chloride activated flux.

author: analogix
author_rank: Frequent Contributor
timestamp: April 21, 2017, 11:50:10 pm
content: Oh noI specifically said at the store that it would be used for electronics.Does this mean the surfaces I've used it for are slowly going to get eaten up by its acid? Is there anything I can do to stop the process and remove it? I haven't used it much yet, so I have a pretty good idea where to clean it up. I also used it on my soldering iron tip as I understood this would clean away any oxide and "restore" it (which it seems to have).

author: Ian.M
author_rank: Super Contributor
timestamp: April 22, 2017, 12:24:27 am
content: Cleanup is important as Ammonium Chloride contamination is equivalent to having a battery leak over your board.If you've only used it on the legs of a couple of chips like U1, you'll probably get away with desoldering the wires(they are FUBARed as it will have wicked up between the strands and you cant get it out), then washing the area thoroughly, scrubbing with a natural fibre bristle brush, first with Isopropyl alcohol (IPA) to remove rosin and grease, then with really hot water with a trace of unscented liquid dish detergent to attempt to remove the chlorides, then with distilled(or deionised)water to remove detergent and mineral traces, then with IPA again to remove as much water as possible. Blot up as much of the water as possible with a lint-free wipe before the final IPA rinse. Blot up the IPA and either dry for 24H in a warm place before you reapply power, or dry *THOROUGHLY* with hot air(no more than 95 deg C)once the residual IPA has evaporated.When you redo it, use the type of silver plated Kynar wire you found on Ebay,(for low voltage low current board patching, its much easier to work with than stranded), and use electronics grade liquid R or RMA rosin based flux(as the dry residue is nearly totally inert)- Do NOT use RA flux(acid and/or chlorides again),and I'd also avoid any paste or gel flux so you don't have to repeat washing the board. Due to the lack of vertical clearance, you *WILL* need to solder to the socketed chip pins, and for a novice this is best done with the chips out and tilted at 45 deg, legs up so the solder doesn't run down from the pin shoulder onto the pin itself, or worse, if done in-situ solder the leg into the socket. Take extreme care removing the chip(s) - if you bend a leg it weakens them considerably and you *really* don't want to break one.If you cant find electronics grade flux, so-called 'water white' grade lump rosin (colophony), which is actually a pale straw yellow to light amber colour, finely crushed and dissolved in Isopropyl alcohol to form a saturated solution can be substituted. That's basically what R type liquid flux is. Apply a drop at a time with a tiny artist's brush or a toothpick.(RMA flux is Rosin, mildly activated. However safe activators are difficult to come by in small quantities, and straight R flux is good enough if you are soldering to clean copper alloys or tinned surfaces.)3M VHB tape is most usually found as a black self-adhesive foam tape sold for exterior use. Its commonly used for attaching car numberplates. Unlike other foam tapes, its adhesive doesn't dry up and drop off as it ages.

author: Nusa
author_rank: Super Contributor
timestamp: April 22, 2017, 01:15:12 am
content: https://en.wikipedia.org/wiki/Wire_wrap, just so you know what it is. It's an old technique that isn't used much anymore, except in a few holdout applications like the telecommunications industry.That 30awg solid-core kynar (and similar) wires are commonly referred to as wire-wrap wire because it was used for wire-wrapping electronics. Nobody here is actually suggesting that you engage in actual wirewrapping, however. The modern use for that wire is as a point-to-point soldered patch cable between small pins.The wire you did use was an acceptable alternative, given the relatively wide spacing of 0.1" pins, except for your big mistake with the flux.

author: @rt
author_rank: Super Contributor
timestamp: April 22, 2017, 04:27:30 am
content: Ah yeah, wrap wire is often called mod wire now too.Here’s an example of what an Atari (and other retro) factory mod might look like:http://www.gauck.com/arcade/MH/MHconv.jpg... which I believe is actually an Atari arcade board.

author: analogix
author_rank: Frequent Contributor
timestamp: April 22, 2017, 12:55:02 pm
content: Quote from: Ian.M on April 22, 2017, 12:24:27 amI already have a bottle of isopropyl alcohol. I checked the safety datasheet and it says "more than 75%" purity. Is that good enough?Alternatively I can buy a spray cleaner calledPRF 6-68 Kontaktwhich is described as follows:Contact cleaner, removes all kind ofrosin flux, oxide, sulfide, dirt and oil. Non-conductive. Application: Television and VCR sets, telephone, electronics, office machinery. Brush is extra accessory.The safety datasheet says it contains 40-50% naphta.Alternatively there's another spray cleaner calledPRF IPAcontaining 40-60% isopropyl alcohol is described as follows:All-round cleaner for electronics.Pure isopropanol, which removes dirt, oil, grease and resin from printed circuits, magnet heads as well as from the parts of fine mechanics and optics. Brush is extraFinally I can buy a bottle of 99.5% pure isopropyl alcohol.Regarding distilled water -is that the same thing as sterile water which can be bought at the local pharmacy?How much time do I have between when I soldered using the (acidic) flux and when it actually does damage to the PCB/components? I probably won't be able to get my hands on the above until over the weekend, but I can start mechanically brushing away the remains with an old toothbrush and the isopropyl alcohol (75% purity) right away if that'll do for now.QuoteSo they're easier to solder on because the strands don't spread all over the place? And I'm guessing they're relatively stiff wires as used in the example Atari arcade board image posted by @rt, but in my case most of the wires go to a connector on an add-on PCB (plugs into a PLCC socket), so wouldn't basic stranded wires be better for that? I bought some "dupont jumper wires" and exchanged the single connectors with one 5-pin connector header similar to the one shows attached here and soldered the ends of each wire to the applicable IC pins on the computer PCB.Unfortunately I made another huge mistake apart from using the wrong flux. After soldering/wrapping the wires in place I secured everything using bathroom grade silicone. I just learnt that this is also harmful to the components/PCB, so I've mechanically removed it all (fortunately it wasn't totally cured so it was just sticky enough to remove easily. I suppose the liquids you've suggested above will remove any remains (I'm guessing there are invisible remains there even though the actual silicone has been removed). I also made the same mistake with some other PCBs a few weeks ago, so hopefully it's not so acidic that it'll create damage in that amount of time if I remove it now.QuoteGood advice! I'll be returning the flux I already bough as they ill-informed me. Thankfully there are forums like these aroundI don't know where I can get electronics graded flux locally but I'll ask around in some local electronics forum. Given all the fake, low quality stuff available on eBay (or similar sites) it's probably not worth ordering from there.QuoteThat's true. So wrap the wire around the top-part of the IC leg in question and quickly (as to not over-heat it) solder it? I should probably clean the IC leg thoroughly with a fibreglass pen etc. as I believe was suggested earlier as well, so solder attaches more easily (and thus less heat is transferred to the IC).QuoteDo you have a link or part number? I could contact 3M directly about it.Not drying up and dropping off is a good point which I would probably have overlooked. Good advice again!

author: analogix
author_rank: Frequent Contributor
timestamp: April 22, 2017, 01:01:50 pm
content: Quote from: Nusa on April 22, 2017, 01:15:12 amI understand. Thanks for clearing that up. Seems like a good option for a lot of modifications where the stiffness of the wire means I won't have to resort to hot-glue (or anything worse, such as my mistake of using bathroom silicone) to fasten it.I was hoping wire wrapping would be suitable for attaching wire to that (hard to replace) PAL22V10 chip so that I wouldn't have to solder anything to it. Would stripping such a wire, then wrapping it round the IC leg several times (using a plier), then carefully rotating the IC (removed from its IC socket) several times create a tight connection which I've been unable to get using regular stranded wires?Failing that I'll probably have to solder it to the ICs leg as Ian.M suggested.

author: Ian.M
author_rank: Super Contributor
timestamp: April 22, 2017, 02:02:40 pm
content: No. You cant wrap onto an IC leg with pliers. Wirewrap relies on a high pressure cold weld forming at each corner of a square pin. If you don't use the correct wrap tool which is specific to a particular wire size and pin size, you cant guarantee the pressure required to form a gas-tight cold welded contact.If you've got as little as 4mm vertical clearance, you could stick a turned pin socket in-between the PAL and its socket, looping and soldering the patch wire round the fat base of the extra socket pin. Otherwise your choices are: solder to the PAL or pick up that signal elsewhere on the board.

author: rdl
author_rank: Super Contributor
timestamp: April 22, 2017, 04:05:55 pm
content: Years ago I built a small DC power supply for a project, but ended up not using it. The 120v mains AC entered through a terminal block. On the bottom side, the short traces from the terminal block to the board mounted transformer were insulated by covering them with a small piece of sheet styrene plastic glued in place with silicone adhesive. This was not "electronics grade" silicone, just the usual hardware store variety with the very strong vinegar (acetic acid) smell when curing. Seven years later, I came across the board when searching boxes for something else. Out of curiosity, I removed the small sheet of plastic to check for corrosion. The traces looked as good as the day the glue was applied.

author: analogix
author_rank: Frequent Contributor
timestamp: April 23, 2017, 09:32:32 pm
content: I'm glad it hadn't damaged your board, but just to be on the safe side I'm going to remove it from my recent use (mostly for fastening coin-battery holders to replace soldered-in coin batteries which have a slightly different pin spacing). So mechanically removing the silicone then cleaning using the method Ian.M suggested should probably do it.I've already asked a bunch of questions about the materials needed, but here's another one: in my search for distilled water I found something called "battery water" at a car supplies store. It's meant for filling up car batteries and I've read in various forums that it's the same thing. Is it suitable for the use discussed here? Its datasheet says:Product description:Battery water is a demineralised quality water. All impurities and minerals are eliminated. Production method: Reverse Osmosis (RO)Applications:Batteries, steam-irons, humidors, water based cooling systems.

author: Ian.M
author_rank: Super Contributor
timestamp: April 23, 2017, 10:21:39 pm
content: Mechanical removal of silicones without use of a specialist silicone remover chemical to remove the last traces is unlikely to be very effective. On chemically clean glass, you can't even scrape it off totally successfully with a razor blade.OTOH if the board wasn't initially clean enough, it may just pop right off. I generally don't like silicone sealents because of the surface contamination issues - once you've used them, getting anything else to stick requires heroic cleaning effort - it wont even stick reliably to its own cured surface. However, sometimes when you are working on EHT circuits, or with plastics that have compatibility issues with other sealants, there is no realistic alternative to the neutral cure electrical grade ones.Yes. deionises/demineralised water is ideal for a final rinse when using water based cleaners. If your tap water is naturally soft, low in minerals, and free from organics, then boiled and cooled water would probably be good enough, but if you live in a hard water area or your water comes from a peaty stream, it wouldn't be, hence my recommendation to use purified water. If you've used any high concentration water based cleaners, or had a lot of battery leakage to clean up you'd rinse with boiled and cooled water before the distilled/deionised water, just to reduce the residual contaminates and save on the purified water.

author: tooki
author_rank: Super Contributor
timestamp: April 24, 2017, 07:43:06 pm
content: Quote from: Ian.M on April 21, 2017, 11:42:23 pmThe label says in German "Contains: Zinc chloride."Quote from: analogix on April 21, 2017, 11:50:10 pmWhat kind of store was it? (I've found that hardware stores generally know nothing about electronics soldering, and carry lots of heavy soldering supplies, for copper roofing, pipes, stained glass and the like, but at most have one electronics solder, typically some huge diameter rosin solder labeled "radio solder" or the like. Probably added to their catalog in 1945 and never updated…)

author: tiger99
author_rank: Newbie
timestamp: August 12, 2017, 07:07:43 pm
content: There are many things that you can do depending on the degree of robustness and permanence required, whether it has to look professional, a one-off or needing done on a batch of units, etc.You can get devices known as Winslow AdaptICshttp://www.winslowadaptics.com/productwhich are often used to adapt a SMD device to a DIL PCB, but some variants are for attaching test leads, logic analysers etc. Other manufacturers make similar things or you can make your own. Just a little PCB with a set of pins fitted that are male to fit the IC socket one end, female for the IC to plug into the other (Cambion?), so it sits as a sandwich between PCB and device. You would design it with pads to take all the wires that you need to attach, to do a real professional job.At least Aries Electronics, Ironwood Electronics and Aprilog are also active in this field.As already suggested, soldering wires to the pins of a standard IC socket and interposing that is almost as good. But if you will be doing a lot of this, not just a one-off, you could design some PCBs with the sizes of IC that you use on them, and get a cheap PCB supplier to make you a few. You would just put the pads and via holes to take the socket and external wires side by side with others of various sizes and order it as one board of a standard size for your chosen supplier to keep the costs down, and cut it up yourself as needed. You could do it on single side but as the cost is usually the same for double, it hardly matters. You might want to design in a midget connector of some suitable type to attach the wires instead of soldering them.If you were wanting to do this sort of thing regularly, you could design a row of vias into your PCBs. Not much help if it is someone else's design, of course!I generally just solder a piece of wire wrap wire to the IC pin, on the top side, and tack it down to the PCB with adhesive at suitable intervals to prevent it flapping about and probably breaking. DIL (0.1 inch pitch) are easy, in fact you can use stranded wire. If you lie the end of the solid wire wrap wire (not used much for its stated purpose nowadays) flat it will go on the pad for a SO package (50 thou pitch) reasonably easily. Closer pitches, you will need to work under a bench magnifier and I would suggest using a self-fluxing enamelled wire of suitably small gauge such as Roadrunner wire.http://www.roadrunnerelectronics.com/.

author: analogix
author_rank: Frequent Contributor
timestamp: August 19, 2017, 09:37:48 pm
content: I'm curious about those wire-wrapping wires. They also go by the name of "Kynar wire", right?I understand they're single-stranded and very strong (so they don't break when wrapping around components, hence the "wire wrapping wire" description), but are they also stuff so they stay in place without glue?I think I'm going to order a roll to try out anyway.These "modification" attachements are just for a PCB here and there, not a production run of 1000I've bought some "turned" sockets, where I assume I can easily wrap a wire around its leg, solder it and attach it into the normal IC socket as the extended round parts won't insert further anyway. That could be a nice solution for the "hard to find/unable to replace" type ICs which I don't want to solder wires directly to. I only putting the IC into the turned IC socket won't raise it excessively beyond the height putting the IC directly into the existing socket would do (as there's another PCB covering the area directly above this IC.If that's the case, maybe wrapping that wire-wrap wire around that IC's leg would allow it to still fit into the socket and without risking to heat up one if it's legs with a soldering iron. I'm of course assuming that the wire would allow tight-wrapping around an IC leg and keeping a firm connection.For ICs that are easily replaceable (i.e. TTL or CMOS chips), but soldered directly to the PCB I think I'm going to take my chances and carefully solder the wires directly to their IC legs, then use some sort of glue to further fasten the wires so they won't mechanically break off when I move them around while attaching them to the other end.After being alerted here that the bathroom silicone would damage my PCBs and having successfully removed it I'm not going back but have instead tried hot-glue which should be safe. But it takes a lot of luck to get a neat, clean and firm fastening, so are there other types of glue which are better suited for this?

author: Ian.M
author_rank: Super Contributor
timestamp: August 19, 2017, 10:15:56 pm
content: Wrapping a wire around a pin by hand will NEVER give you a reliable connection, and using a wrap tool will probably twist the pin off. Solder is actually safer. However for truly 'unobtanium' chips where there is no room to stack a socket, its probably safer to pick the signal up by soldering to the board.Kapton tape is your friend . . . .

author: KL27x
author_rank: Super Contributor
timestamp: August 20, 2017, 01:12:33 am
content: ^ I have once upon a time many years ago been involved in a project where we wire wrapped directly to DIP IC pins. This involved a lot of chips. Well, a LOT of chips.I'm not sure what all minor differences in wrapping tools and IC pins one might find in the entire world, but this was most excellent. And pins did not break off. Not a single issue. Note, this method of hookup was THEIR idea, not mine. They didn't want to hire solderer for this, and there was no time for doing a PCB with FPC ribbon connector or whatnot. But it ended up being more reliable than solder, by virtue of the built in strain relief which was useful for the application. In fact, I had the pleasure of having to disconnect many of them, and it is quite the chore removing the wires, after the fact. I would go so far to say, there is no way in hell the wire is going to fall off accidentally or thru vibration, short of something that will break the pin. I also gave support for many years, after the fact, and I handled many of these IC's years layer. There was no problem with oxidation. I would not trust the connection quite as much if the pins has been used and have enough excess solder to partially obscure the corners of the pins, though. I still have a bag of these IC's that have had the wires snipped, but with the wires still wrapped on them, in case I find a way to recycle them. Removing the wires is a task left for if and when, cuz it involves putting the chip in a vice and grabbing the end of the bare wrap with toothed needle nose pliers, and yanking straight up. (I know there are unwrapping tools, and you can also slip off the wire if you use a wrap tool in reverse, but in bulk, this is quite tedious.)Incidentally, I often make cables with pin header and wrap wire. I wrap even to the flat leads/nubs on the female sockets, in order to get the aforementioned strain relief. Oft, I put a smear of hot glue over top to ensure they don't easily loosen, cuz the leads are tapered and protrude fairly little. They hold very well, though, as long as the leads have good sharp square corners. (DIP IC pins are a little "too small" technically. But they do have nice sharp corners).

author: Ian.M
author_rank: Super Contributor
timestamp: August 20, 2017, 01:32:26 am
content: Yes, but given the scenario of a used 'unobtanium' chip, that has to be replaced in its original socket, the odds are that there isn't going to be enough excess pin length below the shoulder to get a satisfactory wrap, and if the wrap is disturbed by the side of the socket, its likely to fracture the cold weld at at least two of the corners, and the pin may be more fragile than a new chip's pin due to prior fatigue.