Author Topic: Card edge connectors...  (Read 1233 times)

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Offline bsudbrink

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Card edge connectors...
« on: November 30, 2018, 05:20:51 am »
Maybe I should ask this more generically somewhere, but I plan to use KiCad so I figured I'd ask here...

I'd like to "whip up" a bunch of these adapter boards (see below).  I have two questions:

1) Is there a way to indicate that the board edges need to be beveled?
2) Is there a way to indicate that the "fingers" need to be "hardened" (or whatever the correct term is) plating.

Thanks.

« Last Edit: November 30, 2018, 05:23:10 am by bsudbrink »
 

Offline ataradov

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Re: Card edge connectors...
« Reply #1 on: November 30, 2018, 05:33:30 am »
Both of those things are discussed with a board manufacturer directly. There is no standard way of doing this from the EDA tools.
Alex
 

Offline hermit

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Re: Card edge connectors...
« Reply #2 on: December 01, 2018, 01:19:43 am »
+1 to direct communications with the board manufacturer.  There are layers that you can use for comments that I'd include with the gerbers as my 'paper trail' though.
 

Online mark03

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Re: Card edge connectors...
« Reply #3 on: December 01, 2018, 05:44:53 am »
I always want to know (and have never found a definitive answer), if I am only making a handful of these, and I am going to do the bevel myself after receiving the boards, and the finish is only plain ENIG...  How reliable is the result for prototyping?  How many insertions/removals should I expect before problems arise?

Asking this because AFAIK getting the boards done the "right" way is pretty much out of reach for hobbyists.
 

Offline ataradov

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Re: Card edge connectors...
« Reply #4 on: December 01, 2018, 05:53:46 am »
That depends on the mating connector. I've used PCI connectors and boards made using normal process (gold plated, but light plating) with no bevel. It is hard to estimate the number of insertions, but it was probably close to 100 or so during the debugging. And there was no significant damage. You could clearly see wiper traces on the contacts, but no deep scratches or anything like that.

I'll try to make pictures later if I can still find the hardware.
Alex
 

Offline ataradov

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Re: Card edge connectors...
« Reply #5 on: December 01, 2018, 06:02:32 am »
Here is the connector after more than 100 insertions. It was used before and I just inserted it 100 more times.

As you can see there is a visible tarnish, but it appeared after about 10 insertions and did not seem to be any worse after that.
Alex
 

Offline helius

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Re: Card edge connectors...
« Reply #6 on: December 01, 2018, 06:30:35 am »
Asking this because AFAIK getting the boards done the "right" way is pretty much out of reach for hobbyists.
Not necessarily. You can add 3 microns of hard gold yourself using a brush- or pen-plating apparatus, a power supply, and chemicals.

The set-up for pen-plating gold fingers uses copper tape applied across the edge connector, making contact with the inner section of each contact. The remaining outer section of each contact will be plated onto. Then the pen is dipped in the chemical solution and passed over the contact area. You can use an electrocleaning step, then a plating step. Activation (with nickel) may not be necessary as the contacts already have ENIG gold from the fab.
 

Online mark03

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Re: Card edge connectors...
« Reply #7 on: December 02, 2018, 12:33:46 pm »
Thanks @ataradov and @helius!  And apologies to the OP for hijacking his thread.

Where do you recommend starting if I wanted to pursue the DIY hard gold plating?  I actually have another project where this might be interesting, if not too expensive.  I designed an electrostatic field mill using PCB material for both the blades and the sensor plate, with electronics on the back side of the sensor.  It works great, but I wonder how long it will last once I start using it outdoors to measure thunderstorms.  The blades and sensor plates are ENIG.
 

Offline helius

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Re: Card edge connectors...
« Reply #8 on: December 03, 2018, 05:52:16 pm »
There are various suppliers of plating tools: many targeting the jewelry or firearms markets. The largest I know about is Caswell Plating. One frustrating thing about this business is that most suppliers want to sell expensive "kits" and the tools themselves are either cheap crap or not even available.

However, I have located an actual proper plating pen for sale:
https://www.goldplating.com/collections/application-handles/products/standard-application-handle-with-lead-and-no-bit

The plating pen contains a cotton tip over an anode. This anode is stainless steel, but it can accept other anodes such as carbon or platinized titanium.

Gold plating solutions contain cyanide ions and consequently are hazardous. They must be treated as deadly poison and precautions followed.
 


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