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.
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.
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Signing UpStep 1: Before you start, make an assessment of LCD Ribbon and Module
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.
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.
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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.
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.
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.
Thanks for sharing...
I'll be giving this one a try one day.
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 :)
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.
Thanks for sharing.
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.
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.
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.
maybe this one is a closer match:
http://www.digikey.com/product-detail/en/5027906491/WM1449TR-ND/2356633
Judging by today's exchange rate i save my friend 600 bucks...
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!
Great job there, thanks for sharing!
Koray
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.