How much current each FPC connector can handle?

[ali_asadzadeh]

Hi,
I have a product that needs 5V @1.2A and I should use these FPC connectors and Flat cables to power them, I just wonder how much current each pin can carry?

https://lcsc.com/product-detail/FFC-FPC-Connectors_Made-in-China-FFCCable-FFCCable20Ppitch0-5mmlength8CM-In-the-same-direction_C122342.html

https://lcsc.com/product-detail/FFC-FPC-Connectors_JUSHUO-AFC11-S20ICC-00_C11073.html

Any Ideas or experience?

[Berni]

You can find FPC connectors rated for about half an amp per pin but i never felt comfortable with that.

But something like 250mA per pin sounds about reasonable to me and is commonly used for powering LCD backlights from such 0.5mm pitch FPC strips.

So yeah for 1.2A you will need quite a few pins.

[dzid_]

This topic comes up on Google first regarding FPC current rating.

I did some tests with the 0.5 pitch fpc ribbon.

0.5A - Δ1°C
1A - Δ7°C
1.5A - Δ18C
2A - Δ36C

Surely the connector can handle 0.5A as well.

And if one runs multiple power lines next to each other, the temperature rise is somewhat additive. It might be a good idea to insert ground in between signal lines anyway.

The last thing to lookout for then is the voltage drop.

[ali_asadzadeh]

thanks for sharing! how long does it get to the 50C temp at how much current?

[ajb]

Always cool to see some empirical data 

And if one runs multiple power lines next to each other, the temperature rise is somewhat additive. It might be a good idea to insert ground in between signal lines anyway.

Using more conductors for a given amount of current will always be better, but it's worth noting that the allowable dissipation per conductor would go down as the number of conductors used increases.   As the temperature of the FPC/FFC goes up, so does the resistivity of the conductors, and therefore so does total dissipation.  It's also harder to reject the increased amount of heat to the environment, so temperature rise will be increased anyway.  The connector is of course a big variable, and I would expect contact temperature to be the main limiting factor in terms of thermal performance, since a failing contact can cascade rapidly.  Ensuring that the power contacts have solid thermal connections to board copper can help there, but will probably not help much with cable temperature.   Thermal limits like this can be hard to generalize -- just about any connector datasheet will warn you that their current ratings are guidelines and you should do your own engineering based on your application. 

[Berni]

Very nice test there.

From the thermal image is is clear the weakpoint is the resistance of the FPC traces. There doesn't seam to be any hotspots at the connector so it could in theory handle even more if you had a thicker FPC cable.

But yeah contact resistance is not always perfect. So even if it might work in this case, it might not be reliable once you produce 100 such products and some of the pins oxidise or get dirty trough their lifetime.