How to connect tiny 18 connector flat cable to a much larger connector ? - Page 1
Forum section: electronics / general

author: Milacron
author_rank: Contributor
timestamp: August 14, 2011, 05:40:15 pm
content: I should have some photos but hopefully you can visualize the situation after the following description. I need to replace a (1996 vintage) 5.7 inch LCD monitor on a CNC control with another make, as the original LCD has ceased to exist anywhere in the NOS market. I have found another 5.7 LCD with near identical specs...except for two issues-1. The new LCD uses much smaller cable... 18 connector, .5mm spacing flat cable. The original monitor uses 16 connector, round flat ribbon cable, with a two level connector on the end (i.e 8 holes on top, 8 holes below) to connect to the control. (not sure of wire spacing but probably at least 1mm)2. Although the basic LCD specs are the same, the arrangement of connectors for what spec does what, are different. In other words, the connector for logic power supply on the old monitor is "pin" 5, whereas on the new one it is pin 14.So, even if by some miracle an appropriate adapter connector existed, I doubt I could use it anyway due to all the wires I have to lap over each other to achieve same functions at the plug end.(FWIW, I only need 15 of the wires of either cable, so for purposes of this discussion, don't concern yourself with the 18 vs 16 aspect)Bottom line is the 18 wire, .5mm spacing cable terminals, even under stereo microscope, are just too close together to solder the wires from the old cable to. So all I can figure to do, is cut out an inch or so of each of the 18 wires with Exacto razor under microscope and then seperate each wire enough to solder appropriate wires from the old ribbon cable. Then to insulate, create a potting compound around the width of the ribbon cables at the joints.Even with Hakko 936 iron and some experience in soldering tiny components, I'll bet it will be difficult as hell to actually do it however. Therefore wondering if anyone else had a better idea ? For example, I suppose a custom PCB could be created that would utilize one of the many 18 wire .5mm connector possiblities and expand the connections out via traces to solder eyelets for the old cable. But how on earth are those .5mm flat cable connectors actually soldered to a PCB in the first place ? Seems like it would be beyond human capabilites, and have to be an automated situation....but you tell me ?

author: ejeffrey
author_rank: Super Contributor
timestamp: August 14, 2011, 06:33:03 pm
content: Probably the cable on the new device is a flat-flex cable. You can get connectors for it pretty easily:http://eu.mouser.com/Interconnects/Rectangular-Connectors/FFC-FPC-Connectors/_/N-7auq6?P=1z0wxoxZ1z0wxjxHand soldering them is possibleInstead of just breaking out the flat-flex to solder pads, I would snap an IDC connector on the end of the ribbon cable. Then do all the wire crossing on the PCB.

author: Chet T16
author_rank: Frequent Contributor
timestamp: August 14, 2011, 08:54:44 pm
content: You could use one of these:http://www.seeedstudio.com/depot/lcd-ext-breakout-of-05mm-fpc-p-200.html

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 14, 2011, 09:19:41 pm
content: What's wrong with the old one ? If it's just the backlight, replacement tubes are available.

author: Milacron
author_rank: Contributor
timestamp: August 15, 2011, 01:17:28 am
content: Quote from: ejeffrey on August 14, 2011, 06:33:03 pmYes, but wouldn't the solder pins be .5mm center to center also and therefore very difficult to hand solder simply due to such tight spacing ?Or is the situation that the vertical versions of these connectors have half pins out one side and the other half out the other side, such that pin spacing is 1mm ? If so, that might be the solution .... 0.5mm between pins would be extremely difficult to hand solder, but 1mm spacing might be managable.

author: Milacron
author_rank: Contributor
timestamp: August 15, 2011, 01:19:04 am
content: Quote from: Chet T16 on August 14, 2011, 08:54:44 pmNow that is very interesting...had no idea such existed. Is 05mm-FPC the same spacing as .5mm ??

author: Milacron
author_rank: Contributor
timestamp: August 15, 2011, 01:23:21 am
content: Quote from: mikeselectricstuff on August 14, 2011, 09:19:41 pmBacklight is fine, monitor has a strange "halo" such that everything inside the halo is just barely legible. The halo shows even when monitor is off. On the theory that polarization material worn off I even tried a sheet of polarized material I had lying around to no good effect whatsoever.I've had techs tell me the monitor looks like it was "punched" in the middle. But there is a glass shield in front of it, so that is impossible. I have yet to encounter anyone that has seen a small LCD have this particular problem. It actually looks better in the photo than it does in real life. In real life it is extremely difficult to read the characters inside the halo. Brightness and contrast adjustments help very little.

author: Milacron
author_rank: Contributor
timestamp: August 15, 2011, 02:28:38 pm
content: Quote from: Milacron on August 15, 2011, 01:17:28 amIt is curious that on this forum, folks provide some great answers, but then if you go a bit further with the posts, things just die.... tumbleweeds blowing across the thread, crickets chirping...But on the theory no one replied because no one knows the answers..... if anyone is curious for their own purposes, I now know the answer to questions I asked in quote above and can supply some interesting suggestions. So, if anyone cares, let me know and I'll spill the beans

author: ciccio
author_rank: Frequent Contributor
timestamp: August 16, 2011, 03:24:39 pm
content: Quote from: Milacron on August 15, 2011, 02:28:38 pmI read and re-read all the preceding posts, I still do not understand how is the new display's made.Is it a flat cable, flexible PCB type, compatible with the AMP connectors proposed by ejeffrey?In this case, it is possible (I've done it) to make an adapter by "cannibalizing" the old display cable and soldering it's wires to the new connector's pins, one-to-one. I'ts an hard work, but can be done.A maybe stupid question: have you tried to directly contact the BIESSE service department? I'm not sure they have a spare display of the original type, but maybe they have adapters.This is the website (I suppose that it's an Italian BIESSE woodworking center):http://www.biesse.com/Corporate/en/Services/SpareParts.cmsregards

author: IanB
author_rank: Super Contributor
timestamp: August 16, 2011, 08:01:43 pm
content: Quote from: Milacron on August 15, 2011, 02:28:38 pmOK, I will ask. I have often wondered how to solder small wires to small connectors with close pin spacing and have never figured it out. How might it be done?

author: Unknown
author_rank: Unknown
timestamp: August 16, 2011, 09:54:09 pm
content: I think it would be nice if you could post the answers you found/figured out. Nothing's more frustrating than having a problem, searching for solutions, finding someone asking the same question, and reading a final post like 'never mind, solved it'.

author: IanB
author_rank: Super Contributor
timestamp: August 16, 2011, 10:28:28 pm
content: Here is one possible answer:Tin each wire end heavily with solderApply flux to the pins of the connectorSlip a length of transparent heat shrink tubing over each pin, slightly longer than the pinInsert each of the tinned wires inside the heat shrink tubing to overlap the pinApply heat from a hot air gun to shrink the tubing and reflow the solder onto the pins

author: Milacron
author_rank: Contributor
timestamp: August 17, 2011, 03:50:07 am
content: Quote from: ciccio on August 16, 2011, 03:24:39 pmYes, of course..first thing I did. They can not supply a monitor for this control*. Also they were amazingly unhelpful, even refusing to supply schematics of the control to help me figure out alternatives. Their only "solution" is to sell me a whole new control (newer model with different monitor)....which at around $8,000 for a machine worth in todays market perhaps $12,000 is out of the question. So the only realistic choice comes down to reverse engineering for an alternative monitor or scrap a $12,000 machine....all over the lack of a $300 monitor ! It's nuts.... I could go into a Dave style rant over Biesse, but you get the picture*FWIW, this is via info from both Biesse USA and the headquarters in Italy. In fact the USA tech was reasonably helpful up to the limits of his knowledge on the subject, but it was Biesse in Italy that was amazingly UN-helpful. Back when this machine was new they even offered a method of connecting a standard monitor in addition to the built in LCD (it's mentioned in the manual). But a request for further info on that fell on deaf ears as well (something about the software being long gone or obsolete). Believe me, I've tried everything.

author: Milacron
author_rank: Contributor
timestamp: August 17, 2011, 03:55:28 am
content: Quote from: IanB on August 16, 2011, 08:01:43 pmOK, on the better quality "third hand" device....www.grstools.com/And re alternative idea to not need third hand... solder paste.http://parts.digikey.com/1/parts/955917-solder-paste-no-clean-63-37-5cc-smd291ax.htmlAs an aside, one unexpected characteristic of solder paste is it needs to be refrigerated. As such, if you are more than 2 days UPS from DigiKey, they typically insist on shipping it UPS blue (with cold pack)...which can add $26 to a $13 item. But I talked them into shipping it regular ground UPS with the other items I ordered....difference being they say 6 months shelf life if not refrigerated, 12 months if it is. They throw in the "cold pack" regardless.And yet another possiblity....allbeit a bit expensive one....http://www.micromark.com/100W-120v-Complete-Resistance-Soldering-Outfit-with-Tweezer-Handpiece,7473.html.html

author: Milacron
author_rank: Contributor
timestamp: August 17, 2011, 03:57:58 am
content: Quote from: IanB on August 16, 2011, 10:28:28 pmInteresting idea, but I wonder if they even make heat shrink tubing that small...would have to be a pretty tight fit even before shrinking to not fall off.

author: IanB
author_rank: Super Contributor
timestamp: August 17, 2011, 04:17:54 am
content: Quote from: Milacron on August 17, 2011, 03:57:58 amApparently, they do:http://www.heatshrink.com/a2.htm

author: Milacron
author_rank: Contributor
timestamp: August 17, 2011, 04:34:57 am
content: Quote from: IanB on August 17, 2011, 04:17:54 amMaybe I'm missing something but the smallest heatshrink "ID before shrinking" I see on that page is 1.2mm. The contacts I need to solder are only .2mm diameter. Evenaftershrinking 1.2mm shrink tube would be loose.

author: Milacron
author_rank: Contributor
timestamp: August 17, 2011, 04:42:47 am
content: Quote from: ciccio on August 16, 2011, 03:24:39 pmThat is essentially what I am trying to do, except it would seem easier to insert the end of 18 wire flat into a new connector and solder that connectors SMT pins to old display cable that retains the old connector (to the PCB) That way I'm seperating, manipulating and soldering individual wires of the larger round ribbon cable instead of the microscopic .5mm flat ribbon cable.I guess at this point my thread title is a little confusing as the original ideawasto solder the .5mm flat cable to the old connector as you suggest. But since someone mentioned the .5mm connectors with staggered pins, that seemed like a better idea....for all the soldering to involve the larger round ribbon and leave the .5mm flat cable as plug in (at monitor) to plug in (at intermediate connector) only.

author: IanB
author_rank: Super Contributor
timestamp: August 17, 2011, 05:09:49 am
content: Quote from: Milacron on August 17, 2011, 04:34:57 amI have not seen a picture of your particular cable and connector, but I'm just putting an idea out there for a soldering job I've struggled with in the past, where the connector has bare round pins closely spaced (no cups or hollow centers) and each wire has somehow to be soldered to each pin.In your particular case though, once the bare wire end is placed beside the pin the combined diameter would be wider than 0.2 mm? Also it doesn't matter if the heat shrink is loose once the solder has made the joint. The heat shrink tube is mainly to hold the wire near to the pin during soldering and to provide insulation afterwards.But probably I am not visualizing your connector correctly. I thought most often fine pitched ribbon cables used special mechanical connectors rather than soldering? For example, when I took an old laptop apart there were some of these tiny ribbons with 0.1 mm spacing between conductors connecting the keyboard to the main board. The cables fitted into a special press fit socket on the board.

author: Milacron
author_rank: Contributor
timestamp: August 20, 2011, 10:35:04 pm
content: Yesterday I got in a couple of 18 conductor vertical FPC connectors I ordered from DigiKey on Monday. I only needed one, but got an extra just in case I screwed up one. Even with the terminals staggered, such that 9 on one side and 9 on the other...I just flat out couldn't solder the way larger round ribbon cable ends to those tiny .2mm SMT terminals without excess solder shorting out the next pin or other problems. Under the microscope the round wire strands looked like suspension bridge cables !So, I gave up and decided to forget the intermediate connector idea and just split the .5mm flat cables into individual wires as best I could under the mircroscope (with Exacto knife) and soldered up the mess you see in photo below. I used solder paste to solder., and epoxy to insulate each solder joint afterwards.If I had it to do over again, I would use one of those top of the line "third hand" devices that I previously referenced (but have not bought yet), the smallest solder tip that Hakko offers, the smallest solder diameter I could get, and the smallest shrink tubing available (to avoid the epoxy tedium and to look neater)The solder paste worked well but it was a bit more trouble to get it to "stick" to wires before heating than I expected, plus the corrosion concerns.... so I think I'd prefer to use regular solder if possible.I have checked and rechecked continuity between the ends of appropriate connections at each end and all is well. But it will be next week before I get it connected back up to the control for the ultimate test.If you are wondering why all the overlaps and generally strange looking arrangement of wires, see point no. 2 in my original post.The fragility of those tiny flat cable wires does worry me though. I can just imagine when I hook this up having to twist or bend the joint such that one breaks internally and I don't realize it. That's why it might be better to go with the PCB breakout board idea really, as the ultimate solution to this sort of crazy Frankenspice saga.