Extending FFC cables without DIY-Beamer PCB connector
--- OR ---Soldering FFC cables without specialized equipment
A friend of mine once told me about a way to solder high-pitched surface mount chips safely with a standard iron and a few tricks. My idea is to leverage these tricks and setup a tutorial on how to extend 0.5mm FFCs cables without
using DIY-beamer so-called "pcb connector". Although the pcb connector is the easiest and safest approach, it does take more space in the build and it is dependent on actually finding that non-standard part!
Before I can talk to my friend again and get the precise details about this technique, I was Googling to see if somebody else wrote a similar technique. I have found the following text from "jcbklyny" in the forum at "DIYAudio.com". It is not the same technique but it is quite promising. It has much more chances of success than my thing (if you have access to the same stuff as him) - BTW, he tries to solve a very familiar problem...
topic: The Moving Image >DIY Projectors >Easy Solder Flex Cable Extension
I found a quick and easy way to extend the flex cables on LCD's using solder for a sure connection without driving yourself nuts!!
You simply use Solder Weld from your local Radio Shack. It's a liquid solder and bonds much easier and quicker then regular solder will. Simply dip the end of any 30 gauge wire into the solder weld. You'll hardly see any on the tip... you just want to coat it. Then all you have to do is line up the wire with the exposed copper of the flex (Extra Hands from radio shack makes this a snap) and touch the wire with the soldering gun for a matter of 2-3 seconds. Done.
Using the solder weld you dont have to cut out the tracks in the copper, use tape to line up the wires first or worry about the usual problems soldering 30 guage wire .05 mm apart. And I did this with one of those standard, big *** 35 watt pens from radio shack... so you dont need special tips or guns get this done.
I have heard people using a heat gun for this type of stuff or even a hair dryer -- it will probably also melt some of the plastic so be careful (and test as much as you can before attempting on the real thing).
"Solder Weld" is not the standard stuff you find everywhere. So I am looking for a technique using only standard and cheap iron, solder and "flux" (which is common everywhere soldering stuff is sold). You would essentially directly
solder a standard FFC cable to the LCD FFC that you can buy from a lot of online electronic parts stores.*** This is yet an untested technique, but I am writing it down in case somebody knows (or tries!) and can correct it ***
Some FFCs are nearly impossible to solder -- they will just melt because some of them are constructed using glue at near-room temperature! The stuff connected to the lcd panels might or might not work. It is imperative that you find a way to "test" its properties before attempting this. This is an extremely delicate operation and may totally ruin your lcd.***DISCLAIMER: Iron shape and temperature, dexterity, ffc cable pitch, LCD FFC material, distance to other electronic components are all variables that can make it to fail and even destroy your LCD Panel permanently. Best is to try with spare (or similar) parts first; I am certainly not responsible for broken FFCs and LCDs!! ***
- Prepare both sides with a small coat of flux.
- Apply solder on both sides separately: melt some solder onto the tip of your iron, and quickly touch the surface to solder -- the flux in there will make sure there is no bridging between the connections even if your iron touches many connections at once. Just put enough to have a thin coat of solder material everywhere. And I really mean a thin coat -- like "zero volume".
- Apply flux everywhere again -- you can put too much flux, although using a flux coming into pen seems nice
- Position, align and tightly secure the cables together (if you use tape, careful that the heat won't cause problem like melting it) -- Note that you need to position it in such a way that some metal is exposed to later heat it. (need to find the best approach here)
- Apply heat with the iron just enough for the bond to happen. Move the iron slowly across all the connections so it does not stay too long on the same area. You can touch multiple connections at the same time -- the flux is supposed to do its marvel.
- Carefully inspect the result. If you do not have a magnifier you can try using a camera that can take a picture up close. If you have a multimeter and good dexterity, try to test all connections and check for "bridging"/short circuits. Sometimes, you have exposed "test points" on the PCBs from which you can access the signals more easily than the cable.
- Once you know it works, secure the result. Make sure no stress is applied to the soldering directly. Use tape or whatever.
Use a wet sponge
to "clean" your iron. Some soldering kits come with a little sponge: you have to humidify the sponge to use it! Put some solder on the tip and quickly touch and scrub the sponge -- the water will prevent the sponge from burning or melting and it will help cleaning it too. Does not need much water, just enough so it is wet when you touch it.
You can also get some "flux remover" to remove all that flux that sticks everywhere -- although it is not really a problem, it is just to clean things up. Actually, once you used flux you can't re-use it. You have to apply fresh flux for another attempt, so cleaning will actually help here.
Another note: Make sure you do not flip the connections: soldering a FFC cable will probably require that you fold it. Note that if you are only extending a single FFC cable, you might get away with flipping the entire LCD controller board instead of making a tight fold on the wire. This little ASCII art diagram might help explaining it
(Some FFC cables have one end of the cable with the metal exposed on the opposite side so it would be perfect for this, but it is more difficult to find.)
/-----------folded extended FFC---------| LCD Panel
LCD Controller |====LCD FFC===========