How is it made - Page 1
Forum section: electronics / general

author: Jane
author_rank: Frequent Contributor
timestamp: June 16, 2014, 06:44:11 pm
content: Does any one know how the flat cable is connected with the glass screen in the picture below? I red circled it.What working process is used? Soldering , using glue or another procedure?

author: nanofrog
author_rank: Super Contributor
timestamp: June 16, 2014, 11:15:32 pm
content: Anisotropic Conductive Film(ACF) most likely.

author: Jane
author_rank: Frequent Contributor
timestamp: June 18, 2014, 10:10:10 am
content: Thank you for your explanation.As far as I understand ACF must remain pressed ALL the time otherwise it stops being conductive.But when hot bar goes up, does ACF remains pressed /conductive? Or must there be used additional ( epoxy) glue and it was not covered by your video?And where can I buy ACF ?

author: nanofrog
author_rank: Super Contributor
timestamp: June 18, 2014, 11:53:04 am
content: Quote from: Jane on June 18, 2014, 10:10:10 amIt stays compressed (heat cures it while under pressure, so conductive particles retain their position once the bar is lifted).Past this, do be aware there are different versions for the different connection types (flex-flex, flex-glass, ... and different sizes in each type).3M's ACF Tape Page.As to specific sources, that would be easier to do if you're nation's flag was displayed under your userID as a general rule (go into your profile and set your country). Really helps when posting links.ACF tape is rather on the pricey side though (i.e. see things like MOQ = 20 rolls at ~175 - 250USD per roll), so your best bet would be to search for the specific type you need on eBay. 9703 is rather commonly used for cell phone repair (i.e. flex-flex, flex-pcb), and is available this way (example).If you need say 7371 OTOH (i.e. flex-glass), you may be out of luck in small quantities, and have to try and find an alternative repair method, including sending it out.

author: Jane
author_rank: Frequent Contributor
timestamp: June 19, 2014, 05:20:59 am
content: Thanks for your reply.I checked 3M's ACF Tape Page.For. example for 7371 3M saysShelf Life 4 weeks. Does it really mean that after 4 weeks it stops its function?Also it says:Connection Type: Flex to Flex, Flex to Glass, Flex to PETFor 9703 3m saysConnection Type: Flex to Flex, Flex to LCD, Flex to PCBSo, if I need to make a connection between flex and LCD( which is of course made of glass), which must be used?7371 should work with Flex to Glass while 9703 should work with Flex to LCD.

author: nanofrog
author_rank: Super Contributor
timestamp: June 19, 2014, 06:16:52 am
content: Quote from: Jane on June 19, 2014, 05:20:59 amIt means they cannot guarantee it will function 100% within specification beyond 4 weeks. Things can still function after this period, even long after, but things outside of the manufacturer's control will affect it, such as storage conditions.Flux is a good example. Kester gives an expiration date 3 years after the date of manufacture (DOM), yet there are flux core rolls of solder (i.e. Kester 44) out there that are decades old, and it still works. Perhaps not quite as good as brand new, but worst case, a little extra fresh flux will take care of any issues (metal doesn't expire, just need to get any oxides off).Quote from: Jane on June 19, 2014, 05:20:59 amThere is no one-size-fits-all ACF tape as there are differences between the joint types listed (flex to glass, flex to PET, flex to LCD). Glass itself is nonconductive, so there's something on it. PET, LCD, or even metalized film, and they're bonding requirements aren't exactly the same, hence the different products.Fortunately, there's usually some cross-over with the types of joints a product will handle, which is one of the reasons 9703 has become available on places like eBay. I would advise you to read over the data sheets (you'll notice differences, such as particle sizes aren't the same, tape may actually be different material, cure times, cure temps, ...).A pic of the actual screen you're trying to repair, and where you need to bond would help, but the biggest issue IMHO, is going to be availability and cost. I'm hoping 9703 will do you, as it's the easiest to get in small quantities. Going with a distributor (i.e. 20 roll minimum order) is just too much money out of pocket to fix an occasional phone.

author: Jane
author_rank: Frequent Contributor
timestamp: June 19, 2014, 10:54:22 am
content: Thank you for the reply.So, if I need to repair/replace a flat cable( flex) according to my picture( Digitize.jpg) I posted,what kind of connection type of ACF tape do I need?Will 9703 work or I really need 7371 for that repair?And do you have any experience with that kind( or similar) of repairs?

author: amyk
author_rank: Super Contributor
timestamp: June 19, 2014, 01:41:58 pm
content: Keep in mind that the alignment is critical - the trace widths on assemblies mated with ACF are usually in the <1mm range.

author: Jane
author_rank: Frequent Contributor
timestamp: June 19, 2014, 04:48:34 pm
content: @amyk: sure the alignment IS critical. But how does it relate to my question about the connection type, in other words what kind of ACF I should use?

author: nanofrog
author_rank: Super Contributor
timestamp: June 20, 2014, 12:27:18 am
content: Quote from: Jane on June 19, 2014, 10:54:22 amI'm hoping there's actually a metalized film on the glass that's used to make contact with the copper traces in the flex PCB (to provide more surface area for bonding & good electrical contact than the conductive traces deposited on the glass).Assumingthis is the case, then 9703 would actually work. Problem is, I can't be 100% sure based on your stock photo.I'd really need to see a detailed photo/s of the screen to be repaired with the flex PCB carefully removed to have any real chance of making the correct ID (*might* be able to see enough with the flex connector still on, but I'm not confident of this). Being able to rock/sway it under a good light source helps reveal what's on the glass if it's not obvious.There are some other alternatives.1. Try to track down a datasheet from the manufacturer (need a P/N for this). Unfortunately, there's a strong chance this uses a custom P/N (if not an actual custom part), making locating a datasheet difficult to impossible to locate. Best hope for this is if the screen uses the screen manufacturer's P/N, and you can get it from them (may need to request it; goes to #2).2. Contacting the screen and/or phone manufacturer is yet another possibility, but the odds are not in your favor if it's using a custom P/N, even if it's actually a stock part.Visual is the easiest, and most effective way to get the right material to perform the repair IMHO.Sorry it's not such an easy answer, but this sort of bonding isn't really meant for rework/repair outside of the manufacturing facility.Not impossible to do, but it's certainly not as feasible as being able to solder in a part for example, due to the supplies and equipment needed.All of this said, it's not exactly cellophane tape (i.e. just stick it on), as it requires heat and pressure to make it conductive only where required. So even if 9703 is an appropriate tape, how do you plan to apply it so it bonds properly?