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Best Way to Connect 16x2 LCD to SMD Board - Advice, Please.

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Resistoid:
Hello People,

I am looking for some advice on the best way to connect a 16x2 LCD screen to an SMD circuit board for mass production.

I have designed such a board with all components on the top side.

The 16x2 LCD is also supposed to sit flat on the top side of the board. The LCD's connections to the circuit board can be permanent (in normal operation there should be no need for the user to disconnect it).

At this point, I plan to house the completed boards in plastic cases with cut-outs for the LCD, buttons and external connections.

I have already tried surface-mount header pins; unfortunately the plastic block used to hold the pins in rows was taller than the space between the underside of the LCD and the top surface of the circuit board, so that didn't really work.

My questions:

1) What is the most cost-effective means for connecting the LCD screen to the circuit board in a mass production setting?

2) How are such screens connected normally in mass production? (- I couldn't find anything at home with such a screen to dismantle and investigate myself).

Thanks in advance.

Resistoid.

mariush:
For mass production you would custom order lcd screens to fit a particular shape you need.

One option is for your box that holds everything would have plastic raised in the places where holes are in the corner of the lcd panel, to screw the lcd screen with self tap screws to the case and connect the screen to the board with wires or 0.1" pins
Another option would be... for connection, use 0.1" male header and female header to make the connection between the lcd screen and circuit board, or just use plain flat ribbon cable. If you use the 0.1" headers you already have a strong connection but it wouldn't hurt to lock the screen in place in the opposite corner or in several corners.

You ca use 1, 2 or 4 round or hex shaped spacers to get the lcd screen to a particular height... which look like these:

http://www.digikey.com/product-detail/en/V6622K/AE10789-ND/3511432
http://www.digikey.com/product-detail/en/V6622F/AE10791-ND/3511426
http://www.digikey.com/product-detail/en/V6622C/AE10793-ND/3511505
http://www.digikey.com/product-detail/en/24431/24431K-ND/1532163

There's all kinds of spacers, with smaller or longer screw (if you get the right length you could just straight solder them on the bottom side of the board)
Even one would probably be enough to keep the lcd screen in place, two will 100% keep it, four would be over the top and perfect.
There's also nylon spacers which are cheaper..

Here's a youtube video Dave has with a Turnigy charger that has this 16x2 style screen :



It's only held in place by the top pins which are soldered to the board.

In the same thread at the last page there's another teardown of such charger and you see there the screen is actually screwed to board with spacers like i described above :

https://www.eevblog.com/forum/blog/eevblog-397-turnigy-accucel-6-charger-teardown/msg200442/#msg200442

An inverter with custom 16x2 held in place by nylon spacers :

https://www.eevblog.com/forum/reviews/sma-sunny-boy-sb1700-solar-inverter/msg154810/#msg154810

Resistoid:
Hello mariush.

- Thanks for your reply: You've obviously gone to a lot of trouble and it was very informative.

For anyone else able to reply, I should have made clear that it's really the electrical connections between LCD module and circuit board I am concerned about.

For the first few units at least I intend to use off-the-shelf parts wherever possible since this may be the less expensive way to get started.

The way my board is designed currently requires that the highest point on its surface should be the buttons since these ought to protrude beyond the surface of the case. Everything else including the LCD module should be lower. - That's why the LCD sits flat on the circuit board.

I've already tried the 0.1" male header pins you mentioned (soldered to board and then direct to LCD), but as you know, they didn't allow the board to sit flat. Female header sockets were avoided to keep the LCD as low and close to the board as possible. I suppose I could use the flat cable you suggested or add some caps to the buttons to make them "taller".

As you can tell probably, I aim to have as much of the production as possible automated to lower my start-up costs: (This was recommended in one of the tutorials Dave produced about "Design for Manufacture").

I expect that the flat cable would have to be soldered by hand at both ends, whereas SMD header pins can be positioned by the pick-and-place machine.

Am I right in thinking that the electrical connections on the LCD would have to be hand-soldered regardless of using pins or cable?

Thanks again.

Resistoid.

notsob:
have a look at this sharp memory LCD, one version of it uses it uses a zebra 'elastomeric' connector, as the memory LCDs are probably too expensive for your project, try and find a 16 x 2 that uses a zebra strip for connection (as used on a few multimeters)

Cheers

Peter

notsob:
here's a bit more on a zebra connector strip

http://www.fujipoly.com/products/zebra-elastomeric-connectors.html

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