Sourcing FFC cables - how the heck? - Page 1
Forum section: electronics / projects

author: Yansi
author_rank: Super Contributor
timestamp: October 22, 2020, 09:07:13 am
content: Hello,just in the middle of development of a new product, the need for a FFC cable emerged. I thought, simple, just pick one available, and use it. But nope.What I am looking for is a flexible FFC, 8 ckt, 1 mm pitch, 229 mm (9") long one with opposing side contacts. So I pick up the Molex product catalogue and pick suitable type, in this case Molex 15167-0240. A standard part. But looking everywhere I can, I found 0 stock. Okay, thinking I have chosen some odd part, so looking for neighboring part numbers - still 0 freaking stock everywhere. If I can find a part no. listed, I see MOQ of 1000 pcs (not to mention lead times like from USSR era behind the iron curtain).Okay, I understand there is half a thousand types of cables in each product series, so unlikely to all be in stock everywhere. But how the hell should one do any product prototyping? Even though, this is for a product with estimated 8000 pcs/yr production, is it expected to buy $1500 worth of cables just to use 10 maybe 30 pieces for development and testing? What if a change will be needed? Another box of $1500 worth of cables?I am kind of lost as how this stuff is done, what is the usual way. I have tried contacting a local distributor, but so far all I got is all I already knew: No stock anywhere, MOQ 1000.Thanks for any hints.

author: Pinkus
author_rank: Frequent Contributor
timestamp: October 22, 2020, 09:21:34 am
content: Look for one with more wires and cut the ones off you do not need.e.g. Digikey WM25094-NDhas 12 wires. Just use a sharp knife and cut away 2 wires on each side.or Digikey 0151670264: 10 wires but 10" long.

author: Yansi
author_rank: Super Contributor
timestamp: October 22, 2020, 09:26:22 am
content: That kind of hackery is maybe possible to do with on or two pieces. You wouldn't certainly be doing that with 30 cables. And still not sure, how that would work, as cutting off excess wires wil leave thinner cable, than the correct size should be, as there is more plastic tape on the sides than there is in between conductors.And I don't think this is really the manufacturer's recommended prototyping process.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 22, 2020, 09:35:27 am
content: Right, shop around for what's available first. The upside to new product development, you can change it now.Or if it's locked in because of some other component without alternatives, find the closest compatible thing and make an adapter to it. Hacky, maybe. Time-to-market doesn't care.Worse comes to worse, you can make a rigid flex PCB or something like that. Lead time will be better than begging a big mfg to do it, price is... whatever.Did that recently, just on a one-off mind, not that you'd do this in production -- couldn't find a cable for this somewhat oddball connector, so I made an adapter that fits its footprint:https://www.seventransistorlabs.com/Images/LCDHeaderAdapter2.jpgIn production, presumably you'd be able to convince the manufacturer to change it, whether that's with a board rev or adapter, or they have their own stock of cables or something, whatever. Heh, possible glacial lead times notwithstanding...Tim

author: BrianHG
author_rank: Super Contributor
timestamp: October 22, 2020, 09:44:12 am
content: Quote from: Pinkus on October 22, 2020, 09:21:34 amQuality bad-ass huge and sharp scissors will do a much better job. Begin straight right on top of the end conductor and taper off at an angle. And just so everyone else here is assuming such difficulty involved, we are only talking about snipping the ends of the cable, not the entire length of the cable. You will need to purchase 2x as many cables as you are going to use for mess-ups.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 22, 2020, 09:49:22 am
content: LCSC do quite a lot of FFC cables at very low prices- see if there's something close to what you need.Also lots on AliexpressI don't think the MOQ and tooling for custom FFCs is very high.Alos see if you can use a different connector to allow a same-side contact cable to give you more options.

author: Pinkus
author_rank: Frequent Contributor
timestamp: October 22, 2020, 09:50:26 am
content: You are right, the width will be a problem. You will need to set up a cutting template to get the correct cable width at the connector. Of course this is not professional, but for prototypes this is OK in my opinion.Or, as you are saying you are in the developing phase: design with a 10 or 12 pin connector as 10/12 wire cables are available. You then only need to change the connector back to the 8pin connector for the final product.Or look for different pitch cables. E.g. Digikey WM25068-ND: this 9" cable has 20 wires with 0.5mm pitch. You can use multiple wires as needed.Or use a 8 wire 10" cable with contactson the same side. With 2x45° and 1x90° bends, the contacts will be on the opposite side. I tried it with a piece of paper: you are loosing approx. length 1", thats why a 10" cable is needed.Note: Of course this is only recommended for prototyping, as bending FPC cables is not ideal.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 22, 2020, 10:34:33 am
content: If you can use 10 way, you will find this much more available.For small Qtys, Samtec do custom cables - FJ and FJH series, but only in multiples of 5 wayshttps://www.samtec.com/cables/discrete/idc/ffc

author: KE5FX
author_rank: Super Contributor
timestamp: October 22, 2020, 10:46:10 am
content: I never search for parts in the Molex or Samtec catalogs. You might as well shop for your next wife in the lingerie section of the Sears catalog. They don't make most of those products unless/until someone orders them.Just go to DigiMouse or your distributor of choice and see what's in stock. Sort by # available (at DigiKey) and don't specify anything that's in short supply unless you really have to.

author: drvtech
author_rank: Regular Contributor
timestamp: October 22, 2020, 10:46:14 am
content: LCSC do a 20cm and a 40cm 1.0mm reverse. C23861 and C61542

author: Yansi
author_rank: Super Contributor
timestamp: October 22, 2020, 11:41:35 am
content: Problem is, this is an upgrade to an existing product. Management is pushing for lowest possible cost, they are not willing to redesign any of the plastic parts, as that would cost money, while bitching design is taking too long. Also, it is tight ass corporate, so we are limited in suppliers. Nothing from china is accepted. Must be from EU. So here I am, complaining, of nothing available anywhere.The only thing, that can barely fit is 9mm wide FFC cable. Wider not possible, less wide not favourable, do to it being "flimsy" in the flexible bend, that may lead to some mechanical issues.Electrically, I need 7 conductors, so 8x1mm cable made sense to me. Nothing high current, some hundred mA tops in two conductors..I also thought about using a half pitch (0.5 mm), but that seems to be more expensive (about 1.4 times for 10ckt 0.5mm pitch cable) than the coarser pitched stuff.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 22, 2020, 12:27:30 pm
content: Classical distributors stock a few stupid sizes only and costs gazillion $ each.The solution: Aliexpress. Your own QC. BTDT. Good luck.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 22, 2020, 01:16:31 pm
content: Quote from: Yansi on October 22, 2020, 11:41:35 amMaybe someone should tell them that even from an EU supplier, it's going to have come from China anyway, just with the EU distributor's mark-upSeems like the management need a reality check.

author: alanambrose
author_rank: Frequent Contributor
timestamp: October 22, 2020, 04:25:23 pm
content: >>> You might as well shop for your next wife in the lingerie section of the Sears catalog.Hmm, interesting - I never thought of that

author: Yansi
author_rank: Super Contributor
timestamp: October 22, 2020, 05:06:51 pm
content: Quote from: mikeselectricstuff on October 22, 2020, 01:16:31 pmThere is a lot of stuff someone should tell them. But I think it'd be easier to change the employer, rather than changing the management. But that is a whole another story.Quote from: Siwastaja on October 22, 2020, 12:27:30 pmThat makes sense. But they couldn't care less. They can't afford to fail any testing. Hard to explain and not the point of discussion here. I'd rather not go into much detailQuote from: KE5FX on October 22, 2020, 10:46:10 amWell, unfortunately the situation is I need something, that is not in stock. The mechanical stuff is already done and unlikely to be redone in any helpful way.I wrote them (management) an email today, stating the obvious, so I'll see on Monday, how they'll decide. There are just two options: Either wait for the Molex cables to be shipped (will take months), or redesign the stuff at least partially so it can accept available cheap cables from China. Or even more expensive Molex ones, that are in stock at least few hundred pcs.I'll report back on Monday, what will they decide. Tomorrow I have a free day, so back to repairing my CMU200s. I'm done here.

author: chris_leyson
author_rank: Super Contributor
timestamp: October 22, 2020, 05:35:23 pm
content: Wurth have a good range of flat flex cables, 8way 1mm pitch 200mm long 686708200001 for type 1 and 686608200001 for type 2, type 1 has contacts on same side, type 2 on opposite sides. 200mm might be a little short for your application but I haven't seen 250mm cables. I've been here before and you have to do your homework up front, you can't assume there's an infinite range of available cable lengths. Anyway, you might get away with two cables and a single sided connector PCB, cheaper than custom FFC. Get some quotes for custom length FFCs from Molex or Wurth and then see what management have to say and while you're at it design a custom flex PCB and get some quotes for those as well. I work for a company where cost is a driver for everything, it's a pain in the arse they don't seem to understand real product design where performance and reliability should be drivers until it comes around and bites in the arse. I f***ing hate mass produced consumer goods but someone has to design them.EDIT: Nothing wrong with Chinese or any other far eastern manufactured parts and I think they account for the vast majority of what my employers use in manufacturing, some of the high end Silicon is Western in origin but that is only because the far east has to play catch up to some extent.

author: Yansi
author_rank: Super Contributor
timestamp: October 22, 2020, 05:57:41 pm
content: Well, as I've said: Mechanical stuff is already designed and done and we need to somehow with the utmost minimal modifications (only for mounting the FFC) embed the FFC cable into the product. And the only available length that fits is 9", which is a standard part from Molex. Unfortunately, nowhere in stock. 200mm (or 8") is too short, 10" (254 or 250 mm) likely too long for their liking, even though it wouldn't likely matter much. But neither of these is in stock.Flex PCB design - been there, done that in the first mockup design variant. Extremely expensive, I'd say even prohibitive cost. Not to mention that the corporate bound pcb assembly house wants a little fortune for assembling the flex PCBs, as they need their custom support tooling for that.(And flex rigid? No way in hell. Have you even once seen the prices?) Also note that the flexible PCBs are not meant to be repeatedly mechanically stressed by bending. The kapton base material combined with the copper on the outside is just not good for this.PCB joining two FFC cables together is also not an option - no room for it anywhere. The product is simply unsuitably built for the purpose of this.//EDIT: Have checked the Samtec website. Awesome stuff! Will take a note for my personal projects or future contracts. Not sure if it'd help us now.

author: chris_leyson
author_rank: Super Contributor
timestamp: October 22, 2020, 07:18:41 pm
content: Hi Yansi, so custom Kapton PCB never was an option it has to be flat flex because you need some mechanical dynamic wiggle room. I would talk to Molex to see if they have any sample stock that they can release, otherwise if you can get a cable from China on a shorter lead time then go for it, it's a prototype after all and not mass production.

author: Yansi
author_rank: Super Contributor
timestamp: October 22, 2020, 07:39:49 pm
content: I am not sure if I can speak with anyone from Molex directly, but I can try.BTW, contacting Molex directly was the task for the mechanical group, that should have discussed with them the mechanical needs of our product. Doubt they ever tried.