loading

How to remove and re-attach LCD Ribbon from a PCB with a Fine Pitch

Featured
Picture of How to remove and re-attach LCD Ribbon from a PCB with a Fine Pitch
IMGA0445.JPG
This instructable came about from a broken LCD control module out of a modern VW Camper Van. The LCD module is part of a control unit which was virtually unreadable and a replacement for a new unit was £400+. It really was a no lose option, either have a go at fixing it or end up buying a new unit.

The fault of the LCD was that it only displayed a couple lines of output on the LCD. The symptoms are caused by poor location of the LCD ribbon in manufacture and also the poor position of the whole module in the vehicle which exposes it to heat and is subject to vibration within the vehicle. This causes the ribbon to fail eventually and is a known common fault.
The ribbon in this display actually controls the Rows of the LCD matrix and the Columns were handled by a rubber standoff connection on the longest side of the LCD. There were no problems with the rubberized connection.

Some re-work on the LCD ribbon had already been tried with a little improvement but the poor registration of the ribbon pushed me to try a new attachment.

From the photos below you can see the LCD control unit and the state of the LCD ribbon before repair. You can just make out the offset placement and poor registration of the ribbon before repair.
The marks on the ribbon are my mistake of applying too much heat during re-work attempt (see my tips for applying heat and lessons learned later).

Do not under estimate the patience required for this repair as some delicate and nimble work is required and i cannot stress how important it is to take your time and not rush.  You may only get one chance with this sort of repair.

The registrations of the LCD ribbon in this repair was difficult. It took me and my friend 20 minutes just to line up the ribbon for re-attachment. The ribbon in this case is sub 1mm pitch OR less than 25.4 thousands of an inch. You may want to try a simpler ribbon repair on an old LCD clock for example before jumping in head first with fine pitch.

Also the removal of the LCD ribbon is a delicate process as you do not want to tear what is a good ribbon or damage the carbon printed lines. Also the PCB must be respected to avoid introducing other faults and the the re-attachment may need an extra pair of hands.

You may also want to review the last step for results and lessons learned from this instructable before jumping in head first but i believe this will give a you a good insight to some important factors of LCD ribbons and possible success.

Essential Tools:

1. Eyepiece - X10 minimum, X20 Preferred - For Viewing/Cleaning PCB pads and registration of ribbon
2. Scalpel with rounded blades - For ribbon removal and trimming.
3. Small Ruler - plastic or metal - For trimming and clamping of LCD ribbon
4. Solder Iron Or Hot glue gun - For applying heat, adjustable temperature solder iron would be preferred.
5. Small amount of Tinfoil - For wrapping over solder iron or glue gun nozzle
6. Cotton Wool Ear Buds - For cleaning PCB pads
7. Isopropanol Or Methylated Spirit - For cleaning PCB pads
8. Another pair of steady hands - For clamping the LCD ribbon in place
9. Tweezers - For removing leftover ribbon.

If you don't have X10 eyepiece to hand but you have an old scrap scanner you can pinch the lens out of it. The lens is close to X10 conversion.




 
Remove these adsRemove these ads by Signing Up

Step 1: Before you start, make an assessment of LCD Ribbon and Module

Picture of Before you start, make an assessment of LCD Ribbon and Module
IMGA0447.JPG
Before you can even begin to think about removing the ribbon you must make an assessment of what you have and what may or may not be possible.

So Before you start:

Have you tried reworking ribbon? There are already some good techniques for small repairs such as the hot air gun technique.
Other favorites of reworking the LCD connection that i have read here are the tinfoil on a heat gun. This has good temperature management but not so good in tight spaces. The solder iron with flat blade and tin foil is more precise but a 25 Watt iron can be too brutal on the ribbon.

If you have tried re-working the ribbon with no more improvement then these are my  next steps of LCD assessment.

1. Do you have enough spare ribbon to detach and re-attach? The more ribbon you have the more goes you may get but watch out for the mechanical caveat below.

2. Will you be mechanically constrained if you cut the ribbon. This is a tough one as some shortening of the ribbon may make it impossible to re-assemble the device!!

3. Is the Ribbon continuity visibly good, by that i mean the carbon connection lines are continuous and unbroken - Do check otherwise you may be wasting your time.

4. Is it really the ribbon causing the problem? The driver chip could be failing.

5. Finally the easiest call is made by the item is going to be trash and you got nothing to lose.

In the photos below you can see the available ribbon length was generous enough but do watch for mechanical constraints. In some cases you could find yourself not being able to lay down the LCD back down as it is too tight a radius to sit down.

The photo with the pencil pointing indicates how much ribbon was available.

Step 2: Remove Old Ribbon Connection

Picture of Remove Old Ribbon Connection
IMGA0449.JPG
IMGA0450.JPG
IMGA0451.JPG
IMGA0452.JPG
Ok so you got nothing to lose by re-attaching the ribbon.....Lets get going.

The ribbon removal needs careful thought depending on your device. It would be difficult to write a complete panacea solution for every device so please use some careful judgement on your device.

You do not want to pull at the ribbon as you will most likely damage what you already have. In my instance it was best to cut the ribbon free as close to the PCB pads as possible.I used a scalpel to slice parallel to the PCB board to remove the ribbon. Do make a good job of this as you may need to preserve as much extra ribbon to re-attach the LCD module.

Look carefully at what you have to detach and thing of what could improve your chances to make a good clean removal.
These were my observations and experiences:

Do not slice across the top! You will slice into the PCB tracks.

Do not pull the ribbon! It is likely to de-form, could tear OR break carbon connection as a result.

From my photos you can the LCD ribbon being cut. I should of used a rounded head blade and not a pointed blade as shown.
The LCD assembly was lifted off and put in safe place to avoid damage. The ribbon was then gently lifted and peeled back with tweezers to remove the bulk. You must not use force to remove the remainder ribbon especially if your PCB is off a cheap quality OR single sided cardboard type variety. The PCB pads can come off with the ribbon! If you have a double sided PCB of FR4
quality then LCD PCB pads should have better adhesion to the laminate but in fine pitch devices they still can come off so beware.






Step 3: Clean the PCB Pads

Picture of Clean the PCB Pads
IMGA0454.JPG
IMGA0455.JPG
IMGA0456.JPG
Having removed the ribbon, the PCB pads will need some attention to remove leftover ribbon material.

If you have a half decent PCB the connecting pads may be gold flashed (actually called Electroless Plated gold). This gold flashing is good as it provides a very good flatness to the PCB pads but they are not as mechanically strong as gold edge connectors (like you see on old PC adapter cards) which is a hard gold . The gold plate here is soft and also micrometer thin on the surface. 

If you have just tin solder pads the surface may be a bit rough. You can re-touch solder pads to improve flatness and hence the connection.

For either connection style  you need to remove any old glue from the ribbon and remaining carbon debris from the pads. I used isopropanol on a cotton wool bud. Do not flood the PCB with cleaning fluid as you may effect electro-mechanical elements in close proximity such as switches and other items on the PCB which are not sealed against cleaning!

The PCB pads must be thoroughly cleaned and no debris must exist. Use you X10 OR x20 eyepiece here to check how clean the  pads are. The PCB pads need to be pristine and nothing less.

From the photos you can see the PCB pads before cleaning through the eyepiece and the final photo shows the clean PCB pads with leftover cotton wool buds.




Step 4: Trimming and Preparing the LCD Ribbon for re-attachment

Picture of Trimming and Preparing the LCD Ribbon for re-attachment
IMGA0460.JPG
IMGA0463.JPG
The ribbon was then laid flat with a ruler and a scalpel was used to trim up the ribbon.

I found it was best to use a plastic ruler to view through to the ribbon so i could see how much i should cut off.
A metal ruler can be used and may have straighter edge to work against but a plastic ruler was sufficient.

Do use a rounded scalpel blade to prevent dragging the LCD ribbon while cutting.
Do use a flat cutting board or a cutting mat.
Do check the ruler is as perpendicular to the sides as much as possible.

Remember you may only have one chance at re-trimming so getting right first time is essential.

From the photos you can see that ribbon was trimmed with a rounded scalpel blade.  The ribbon also had extra green tape which adhered to the original heel of the PCB pad connection. This gave extra mechanical stability for the ribbon but has to be peeled off to allow for re-connection. Later in this instructable i will mention about putting back extra mechanical stability for ribbon support.

Step 5: Pre-Assembley and Registration of LCD Ribbon

Picture of Pre-Assembley and Registration of LCD Ribbon
IMGA0472.JPG
IMGA0473.JPG
After cleaning the PCB pads thoroughly and trimming the ribbon the re-registration of the LCD ribbon was the hardest.

If you have a fine pitch ribbon like i had this will cause you the most trouble. I needed an extra steady pair of hands to help and some patience before i got the the ribbon aligned. It took twenty minutes of nudging the PCB and ribbon to get a precise alignment. Our alignment was actually better than the original which was slightly skewed to one side.

If you do not have an extra pair of hands then i did think of using a large ball of Blu-tak to hold things in place but a second pair of hands is much better!

The trick to get good alignment is to allow some the gold pad fingers toes of  the PCB to be visible just beyond the carbon lines of the ribbon. You then get the pads toes to line up with the carbon lines of the LCD ribbon.

Do not continue until you have excellent alignment of the black carbon lines of the ribbon to the PCB pads. The finer the pitch of the ribbon the better registration is required.

Do use your X10 or X20 eyepiece to check registration continually

The photos below show how i handled the PCB and LCD and clamped the ribbon in place. The LCD display is being held by a plastic clamp above the PCB assembly. The PCB below which has components both sides is laying on some foam (try polystyrene). This allowed me to nudge the PCB under the ribbon into position. The plastic ruler acts as a LCD ribbon clamp. When you have got the registration get a steady handed friend to hold the ruler as a ribbon clamp in place so you can then apply the heat to stick the ribbon back down.

The photos actually do not show the good alignment but just poor alignment but you can see what nudging should happen to get alignment.

Check out the third photo and you can see what fine pitch means. There are two carbons tracks with a gap in every 1mm (25.4 thou). Now you see why it took twenty minutes to align!

You may want to skip forward to the next step to see the re-attached picture of the ribbon and to see how the alignment was achieved. You should see the gold PCB pad finger toes in line with the carbon of the ribbon

The best result is found on the right hand of the ribbon in the picture after alignment and heating. The left hand side had too much heat applied.





Step 6: Apply the heat to re-attach ribbon

Picture of Apply the heat to re-attach ribbon
IMGA0476.JPG
So you now have your pristine PCB pads and the ribbon is clamped in place we are ready to apply heat.

Some tips to applying heat:

1. Do not apply so much heat you obliterate the ribbon. Yes it sounds stupid but i over cooked one side of my ribbon and got away with it. You may want to test on the bit you trimmed off elsewhere to get correct amount of heat.

2. Only tack the ribbon down my pressing the heated tip down vertically and stroking from the heel to the toe. That is to say in the same line that the carbon lines flows.

3. Do not be tempted to apply heat with a broad swiping action! - The LCD ribbon with heat will drag or tear especially on fine pitch ribbons.

4. Avoid applying heat to other components you do not want to! If the work space is tight shield other components.

Tools for apply heating are up to you but i used a 25W Soldering iron with a wide flat tip covered in tin foil. Warning, the solder iron is too hot with tin foil so i cool it a little by dipping it into a wet sponge just before applying the heat. I used the solder iron tip method because i have more fine control but it did not have a regulated heat. If you have a good soldering iron with temperature control start low and work up to get the right heat.
You can also use a hot glue gun tip covered in tin foil which has a milder heat but the glue gun tip can be too large in confined spaces.

Applying the heat

The steps to apply your heat are as follows:

1. Do one final check of registration before heating

2. Tack down one end of the ribbon and re-check the registration.

3. If all good then tack down other end and again check registration.

4. With the LCD ribbon now tacked and registration is still maintained you can apply the Heat to the remaining ribbon.

Again Do not apply heat to the ribbon in one broad stroke. Work from the heel of the ribbon to the toe Or work by dabbing. By dabbing I mean hitting one spot on the ribbon with the heated tip and then lifted vertically again cooling the tip with the wet sponge before each dab.

You will know that the ribbon is attached as the glue in the ribbon changes its appearance on the PCB.

The first photo in this step is for demonstration purposes to show a solder iron with tinfoil attached.

The second photo in this step is the actual ribbon re-attached. You can see that the left hand side of the ribbon has not worked out as well as the right. I had too much heat in the solder iron. This is how i ended up cooling the solder iron with the wet sponge before applying heat.

Ideally i would like the whole ribbon to look more like the right hand side of the photo.

You can also see how the PCB gold pad toe is just visible. This is how the good registration is achieved.

Step 7: Optional Post Ribbon Attachment - Adding Extra Mechanical Support

This bit is optional but could help with mechanical stability of the LCD ribbon.

In our case the LCD ribbon was not only glued to the PCB pads but there was some additional tape at the heel of the ribbon to hold the ribbon in place. By holding at the heel the ribbon you get some good extra mechanical support.

I did not replace the heel taped to the ribbon so we added some mylar sticky tape across the ribbon pads to add some extra support.

You may want to consider some extra support depending on your LCD environment such as vibration.

I would not advocate hot gluing for obvious reason and do not know whether an epoxy glue would be advisable.

You would only apply LCD ribbon supplementary support after successful testing otherwise any re-work after attachment may be impossible.

Comments please...

Step 8: Re-Assemble your Device and Test

Picture of Re-Assemble your Device and Test
In our LCD module we partially assembled the device as best as possible so we could test it its operation.

From the photo you can see the LCD operation is much better than the couple of lines we had but is not ideal.

Step 9: Results and Lessons Learned

Picture of Results and Lessons Learned
Our result was a partial success and not 100%,more like high 90's%.

From the photo some lines were still not functional but considered against the two lines that we had it was a very good result.

I did not go further with more re-work as the VW LCD module was considered a good enough result and some other time pressures intervened. It was concluded that we could read the display well enough and operate items from the controller. It was also considered as one of those quit while your ahead things!

For some people this may not be good enough but i hope that some of the steps i have listed will get people going in the correct direction when considering this. I do believe with a little more time a 100% is achievable. I took two hours to dismantle and remove the ribbon, Most of this was thinking things through... and another two hours to re-register and re-attach ribbon.

On the Lessons learned from this there are many :

1. Most important was that you may only get one go.
2. The ribbon and PCB need the utmost respect to not introduce other problems.
3. Registration of the ribbon is difficult with fine pitch but not impossible.
4. You need a good set of eyes, an eyepiece, steady hands and patience.
5. Ideally you would like a temperature controlled heat application. (A compact heated metal roller to apply heat to the ribbon)

The technique for LCD ribbon removal and re-attachment are achievable certainly on simpler ribbons and fine pitch ribbons with careful preparation and thought. I hope this instructable is comprehensive enough for people to get some good results.

Thanks for following.

UPDATE 12-10-2012 - Background and Reference Material

The ribbon is know as a "Heat Seal Connection" OR "HSC". In the industry heat and pressure are used to make this type of connection. The material comes from a family of "Anisotropic Conductive Films" OR "ACF".
The material bonds at 180 DegreeC. Direct Ribbon connection is used for economy (i.e. no fancy connectors) and for the number of connections its offers in a small footprint which would not be possible through traditional connectors.
The other end of the ribbon that joins to the LCD is terminated on the glass on Indium tin oxide (ITO) which is one of the most widely used transparent conducting oxides.
If you want more information there are many different types of LCM assemby (LCD Display plus it driving chips) to look at but these are the main ones (increasing in density):

1. Elastomeric Connection
2. Heat Seal Connection - What was fixed in the instructable!
3. FPC - Flexible Printed Circuit as used on phones. Can be many layers and expensive.
3. Tab Connection
4. Chip on Glass
5. Chip on Films

In manufacture of these modules a machine is used for assembly which would compress HSC to the LCD Or the PCB and then apply the correct amount of heat.



















dustooff2 months ago

I have two items to add, kapton tape and sil-pads used to isolate heat-sinks from semiconductor devices. With kapton tape it brings the means to secure the ribbon to the board, place the tape over the whole connection area, and kapton resists heat very well, ( try and melt it with your soldering iron). This means an average soldering iron turned down will allow heat to be applied to each joint. With experience a rework can be done in a few minutes. The bond can also be renewed on the LCD glass as well, kapton also works here. Sil-pads allow heat to be passed to the joint with some pressure applied at the same time. The sil-pad can be dragged up and down all the ribbon connections allowing uniform heating. Once the bond is resurrected the sil-pad is discarded. http://goo.gl/mpZNkm

guischall2 years ago
Great job!!

I'm wondering if it wouldn't be easier, more accurate and reliable to place a real SMT connector on the board?

something like this one: http://www.digikey.com/product-detail/en/FH40-64S-0.5SV/HFW64CT-ND/2295757

It's pretty cheap and easier to solder, then you just have to clamp the cable into the connector. Maybe you are interested in reworking that to get all lines back.
Sorry, the connector on the link doesn't match the board design... you must search for FFC, FPC connectors with the number of vias of your cable and look for the real dimensions on the datasheet.

maybe this one is a closer match:
http://www.digikey.com/product-detail/en/5027906491/WM1449TR-ND/2356633

I just thought the same way, adding aLCD flat connector... then you can swap chinese or VDO oem screens. Seems the VDO LCD(as for Audi A3-Vw golf/jetta4) have 50 pins and the ribbons is 48mm width. Then you have to look to modify the metal bracket to avoid pressure on ribbon.

There is a v2.1 of this with a smaller ribbon cable but you have to solder the controler board instead ..it wouldnt fit the connector thought!

chaoticandrandom (author)  guischall2 years ago
i would not rule out a connector fix totally but its nice if you can fix for zero cost if possible. Also you then have to manage the mechanical constraints as well as choosing a suitable connector. Usually only the semi flexi PCB circuits ribbons go into connectors not the carbon screen printed sort so may not be so desirable.
DIVYA GARG2 years ago
I think........you are a good electronics engineer ...........but I am not as you ......rather I have damaged my 3 calculator by this action.....................!..........................................but you have written very good............!
billbbc2 years ago
Saw this and used the nozzle of a hot glue gun to reglue a display tape. Worked first time without retrimming the tape.

I simply lifted the clear tape off from the top of the ribbon, then slowly stroked the ribbon contacts in turn a couple of times with the hot glue gun tip. Not hot enough to cause any damage.

Unit I repaired with missing segments was a Honeywell CM907 controller. £65 UK saved. Thank you for posting this.
bwelkin2 years ago
This step surprised me! I am very unclear what that thing is that is heating the solder pads.

My recommendation is to use a T-iron (see eBay .. about $35USD) which has the added advantage of having a heat shield that protects the insulation leading up to the solder pads.
chaoticandrandom (author)  bwelkin2 years ago
In the photo i am only using a soldering iron covered in tin foil to heat the plastic ribbon. There is no solder used in this setup. The tin foil is there only to provide a better surface to apply heat to the ribbon (does not stick to the ribbon!!).
When heat is applied to the ribbon it melts like a glue which in turn bonds itself to the PCB and the ribbon becomes attached to the PCB as it cools.
Actual Electrical connectivity is provided by carbon lines which are printed in the ribbon. The carbon lines only make contact via the adhesion of the ribbon.

The solder iron method technique is actually too hot and so i dip the solder iron in a sponge to cool it down before pressing down on the ribbon. If you have a temperature controlled soldering iron it would be much better.
You can control the heat.

Hope that was a bit clearer :)

The T-tip iron you mention is a specially adapted solder iron for LCD ribbon.
It has a wide metal bar tip and distributes heat across it.
The T-tip one i saw on eBay was 40 Watt unregulated so again that is almost double my 25 Watt iron i used and that was too hot.
I haven't used one of these before so I can't really comment on it BUT It does look very useful. Thanks.

Anyway I was trying to use tools that most people have at home and with little or no extra cost.




detinu772 years ago
Is that an actual scalpel you're using? I haven't seen one of those in a while.
i have an alarm clock which doesn't have a ribbon, but instead some sort of rubbery contact strip against which the display should be pressed. You can find pics of it on google images for "lcd rubber contact strip", it seems to be called a zebra rubber. Any idea on how to glue/solder the display to that rubbery contact strip?
you just have to position the conductive rubber properly - this type of LCD is very popular and it's much easier to repair compared to what the author has described. If some of the bars/elements are still not working, you may try cleaning the contacts using the eraser. But
dasjeetu2 years ago
Thanks for the idea, perfect.


Thanks for sharing...
paddyart2 years ago
Great Instructable... It's fantastic to see people giving a fix a go, before buying a new one.
I'll be giving this one a try one day.
a2e2 years ago
There's always a guy who goes where everybody says "it cannot be done"... My admiration and respect fellow.
Treknology a2e2 years ago
Ditto. One day someone will come out with a "needle-point" soldering iron, so that it becomes possible to individually re-solder SMD connections.
snayl2 years ago
Very thorough, a pleasure to read. I haven't had the need for a repair like this as of yet, but I shall definitely bookmark/download/etc. this instructable for future reference!
artemff2 years ago
very detailed instructable, thanks for sharing.

I recall that in the old days when I was younger and digital multimeters were expensive, I broke the LCD of the multimeter I borrowed.
To fix it, I purchased LCD, which could be soldered and I used extra thin copper wires to connect it to the main board since this was a different type LCD and one-to-one connection was out of the question.

Returning to your instructable - in principle, I can imagine using the same approach in your case. One can avoid soldering to sub-mm spaced contacts by tracing the board and connecting to different parts of it. This gives more freedom since the wires can be checked individually. LCDs are far less expensive compared to the control module you named so one can worry a bit less :)
f5mando2 years ago
I wouldn't ever attempt this again after ruining two SID displays from a (GM) Saab.
There is a company here in the USA that repairs these for reasonable cost, and a lifetime warranty. I got it back fast, with 100% readout, and it continues to function perfectly three years later.
*I also took advantage of their electronic throttle rebuild under the same terms, also with a perfect result. Not sure if it's acceptable to post their name or link here, so I won't until I hear otherwise.
maxhuey2 years ago
I have seen this done by a kid (about 15 y/o) right on the sidewalk in the electronic district street of HK. He brush some kind of liquid on the ribbon and a small butane torch for heat source - several quick passes did not melt the ribbon. I can imagine my hand would shake like mad but some people just got the golden touch! You are one of them... Cheers
bahi2 years ago
Impressive and accurate work, never thought it could be possible to repair such kind of connections.

Thanks for sharing.
chaoticandrandom (author)  bahi2 years ago
Thanks, these connections are definitely repairable but the fine pitch on this ribbon is the hardest part. I suggest anyone having a go try something simpler before going with the more difficult projects. I had actually repaired an MP3 FM transmitter display before doing this one. That was easy only just about 10 or so connections and much larger pitch between them. It was good practise.
Not to disparage you or your (otherwise excellent) I'ble, but by my calculations, 1mm is about 39.37 mils (thousandths of an inch), not 25.4.

I've done a similar repair on Virtual Boy video game systems (although they have actual foil+Kapton cables, which can actually be soldered) so I know how hard this can be. Excellent work describing the process and pitfalls.
I have done a lot of SMD rework, and one item that REALLY helps is a flux pen. It will cost you about $7, and is about the size of a small felt tip marker, but it dispenses liquid flux. A little of this makes the solder flow much better, helps to avoid bridging, and lets you use the minimum solder necessary.
Along with the magnification you recommend, get PLENTY of light on the project.
I use a magnifying visor when I don't have access to a stereo microscope.
Get the smallest soldering tip you can. Sometimes in a pinch, you can wrap some small wire around a larger tip and extend the wire to form a new tip.
chaoticandrandom (author)  wa7jos2 years ago
Experienced SMD Re-work definitely helps with fine pitch but No need for flux here on this type of connection. There is no solder here just the plastic strip and carbon lines which bond with the gold pads. You are just softening the plastic strip to bond with the PCB.
chaoticandrandom (author)  DrNerdington2 years ago
Your right, i seem to have got my conversion wrong. Thinking too hard about everything else trying to get the info down. I will update and correct later. Thanks.
Spokehedz2 years ago
Wow, I would say that for spending zero dollars that is a darn fine job!
chaoticandrandom (author)  Spokehedz2 years ago
Yep,always good to fix things for zero dollars.
Judging by today's exchange rate i save my friend 600 bucks...
mario592 years ago
Ciao!

At least now, we have AN IDEA of what one needs to face such problems!
Each time I tried to repair, it failed mierabily.
Thanks for sharing!

I do have questions regarding the ribbon cable. Did your ribbon cable have insulation on both sides? If it has, did you strip or scrape a bit of insulation prior to connecting it on the board?
Oops okay I read the comment below and it seems that yours dont have insulation on the connecting side.
Fantastic instructable! This is one of the things that I've always wondered about. I thought some sort of conducting glue was in charge here, never thought it was even pressure and heat.

Great job there, thanks for sharing!

Koray
a lot of great info here! I've never worked with this type of ribbon before, does it have exposed leads on one side?
Thanks, glad you like, i really did want to get down everything i learned.
There are no exposed leads on the ribbon but it is not symmetrical.
The matt (non shiny) side has the carbon connection lines screen printed on and thats the delicate part. Its easy to scratch off.
The other side is shiny but it is not the side you connect.