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50 pin FPC connectors
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50 pin FPC connectors

by carlosgr86 on Tue Jan 08, 2019 5:37 pm

Hi,
I am recycling TFT screen and I would like to use it for a new Arduino project.
The screen has a 50 pin FPC connector.

I Believe I can use:
50 pin 0.5mm pitch FPC Adapter (PRODUCT ID: 1492)
together with
50-pin 0.5mm pitch top-contact FPC SMT Connector (PRODUCT ID: 1773)
to connect to TFT screen to the Arduino.

Would this work?
I think I saw a pre assembled 50 pin Adapter+Connector to avoid the soldering step.
Is that still available, or did I just dream about it?

thanks.

carlosgr86
 
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Re: 50 pin FPC connectors

by adafruit_support_mike on Wed Jan 09, 2019 12:54 am

We have a 50-pin flex cable extender with two FPCs:

https://www.adafruit.com/product/2571

but I don't know if that will be useful for you.

PID 1773 (the FPC) does work with PID 1492 (the breakout PCB), and the breakout gives you pin-header and wire friendly connections.

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Re: 50 pin FPC connectors

by carlosgr86 on Wed Jan 09, 2019 10:04 am

Hi, Thanks for the reply.
I had seen the 50 pin extender. But it leaves me with the same problem.

It seems I will have to go for the soldering option. Fun times. Any tips for it?


Carlos

carlosgr86
 
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Re: 50 pin FPC connectors

by adafruit_support_mike on Thu Jan 10, 2019 1:54 am

Soldering SMT components by hand isn't as bad as it looks. There are some things to know, and a process to follow though.

First, at SMT scale the forces of gravity and friction are negligible. The major forces in play are:

- Any seating force you apply to hold the part down
- The force of the soldering iron touching the part
- The surface tension of the molten solder
- The mechanical strength of any joints that are solid

Solid joints have more mass and far more strength than the things connected to them. You'll rip the pins out of a chip and the endcaps off of passives before a solid joint even flexes, so don't try to fight existing joints.. the component will be the loser.

Correctly positioned solid joints are ideal part-holding devices though. Start by making exactly one joint, then tweak that joint until the part is lined up with the rest of the pads. For an FPC, use one of the big mechanical joints at the ends.

One of the bigger challenges in SMT soldering is that you have to hold three things to make the first joint: the part, the iron, and the solder. Mechanical hold-downs don't work, so break the job into two parts: start with just the solder and the iron, and tin the PCB pad where you want to make your first joint. Then put down the solder, place the component on the pad, and heat the tinned pad with the iron. The existing solder will melt and form a joint with the component. You can press the component down onto the PC while the solder is molten for good seating, but don't worry too much about the orientation of the pins and the pads at this point. Just get a stable joint.

Once you have an existing joint, you can re-melt it without actually touching the component with the tip of your iron. Move half a millimeter away from the part and just heat the solder. The surface tension of the solder will hold the part roughly in place while you nudge it into alignment with the PCB pads. A toothpick or bamoo skewer work well as a nudging probe.

If you need fine adjustment that's too delicate to get by nudging, you can walk a part across the PCB with two joints on opposite sides of the component. The idea is to melt one joint and use the other as a fixed pivot while you tweak the component's location slightly. Then you hold the component in place while the heated joint cools, melt the joint that served as the pivot, and tweak the component's position the other way. With a little practice, you can move a component anywhere within a couple square millimeters that way.

Once the part is fastened to the PCB mechanically and registered to the pads, it's all about surface tension.

Well-fluxed molten solder will naturally spread across exposed metal and form the smallest surface it can. You can melt a blob of solder onto the tip of your iron and drag it along the pins, and it will leave a row of nearly-perfect joints as it passes.

You might end up with a few bridges between pins, but those are easy to fix: give them a dab of flux, remove any excess solder from the tip of your iron, and reheat them. In most cases they'll spilt into two clean joints, and any small excess of solder will wick its way across the surface of the soldering iron's tip. If you have lots of bridged pads or blobs of excess solder, give the whole thing a coat of flux, lay the tip of your iron on a piece of solderwick, and run the solderwick along the row so it just touches the tips of the pins. The solderwick will pull away any excess metal it can, and what's left will form perfect joints between the pins and the PCB.

For a 50-pin FPC, making the 50 joints probably won't take much longer than getting the pins registered to the pads.

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Re: 50 pin FPC connectors

by carlosgr86 on Wed Jan 16, 2019 10:41 pm

Wow! Thanks for the great (and extensive list of) tips.
I will order the parts and let you know how I get on.

c

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