Screen Tablet malarky => Tutorials and useful knowledge => Topic started by: Drewid on January 02, 2007, 08:53:05 PM

Title: Neat "how to solder" tutorial
Post by: Drewid on January 02, 2007, 08:53:05 PM

Title: Re: Neat "how to solder" tutorial
Post by: bernard on July 30, 2009, 07:54:32 AM
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 "". 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!! :P ***

  • 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.

Side note: 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  :P  (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===========


Title: Re: Neat "how to solder" tutorial
Post by: random-jimmy on February 05, 2010, 02:32:36 PM
Sorry to resurrect an old thread, but a few tips for those soldering for the first time, and for those who wish to solder FFC cables:

1) Buy a low-wattage (i.e. 15W) iron from a local electronics store. These cheap irons do not have a temperature control on them, and a 45W iron gets very hot, very quickly. As a plus, if you buy a small iron, it will have a small (either 0.5mm or 0.2mm) tip on it which will help with the soldering.

When soldering, do not hold the iron on the joint for too long, or for too short a period of time. Generally, this is the process: iron on, wait for 2 secs, apply solder until a nice joint is formed, remove solder, wait 0.5 secs, remove iron. If you do not hold the iron on there long enough, then you will not form a proper join. If you hold the iron on for too long, then you will end up damaging the circuit board and its components. Also, do not apply too much solder: look on the internet for what a "nice joint" looks like. The more you solder, the better you will get at judging how much solder to use and when to add it.

2) Buy the right solder for the job. If you are looking to solder large wires i.e. backlight cables or PSU wires, then use thick solder. If you want to solder FFC cables, then grab some extremely thin solder usually used for SMD rework. And whatever thickness solder you use, make sure it is a flux-cored 60/40 solder (i.e. 60% lead, 40% tin). This melts at a lower temperature, making it easier to solder with, and the flux core helps to make a nice, clean joint.

3) If this is your first time soldering, then I recomment two things. One, practice first: on scraps of wires or old motherboards/GPUs/etc you may have lying around. Do NOT attempt to go right into it (although I guess this is a common rule across the forum).

Also, make sure you have some "desoldering braid". This is basically a thick wire impregnated with flux that "soaks" up solder. To use this, simply place the braid inbetween the solder to be removed, and the iron, forming a sandwich of sorts. Apply heat with the iron for a little while until the solder begins to melt and get absorbed by the desoldering braid.

The reason I suggest having the desoldering braid is that you WILL make a mistake somewhere: it is only natural.

Title: Re: Neat "how to solder" tutorial
Post by: bernard on February 06, 2010, 07:37:09 PM
Yay! A true electronic guy! I also saw your other post about using a MAXIM and/or step-down resistor to get  3.3v
You also mentioned you lost your previous bongofish logon -- which one was it?

Title: Re: Neat "how to solder" tutorial
Post by: random-jimmy on February 07, 2010, 01:08:41 PM
My previous bongofish username was exactly the same as it is now: random-jimmy. I only just signed up for the forum.

Also, I may have some good electronics knowledge, but it's scratchy at best: I'm only starting university this year (lol). However, in four years time, we should be able to say hello to another (if there is already one) electronic guy on the forum (I don't plan to leave, although I may not be full time on here)

Title: Re: Neat "how to solder" tutorial
Post by: nilum on July 10, 2010, 05:26:42 AM
Can anyone suggest a good soldering iron? What wattage do I need, and how much should I be spending?

Thank you.

Title: Re: Neat "how to solder" tutorial
Post by: bernard on July 10, 2010, 05:28:52 PM
Like anything, it depends on your usage. Did you say what you wanted to do with it?

I assume you want to make precision electronic soldering? The best is to find something that you can control the temperature.  For unfrequent "hobby" usage, no need to spend the big money (200$+) on the big brands IMHO.

I spent around 100$ for a digital temp-controlled station (that also shows the current temperature) with one iron tip. Bought at a local electronic store -- the brand I never heard before. You can probably find a better deal. This is often named "soldering station". 

Just did a small search and found an interesting (recommended) site. Here's what looks a nice digital one with a good price (50$US):   On the site, you can get a fixed wattage soldering iron for like 5$ !  You can get an temp-controlled (analog) for 35$.

BTW, watch out in which country you are for matching the input voltage.