mkirk
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Pi 3B male 40 pin header - gold, nickel or tin plating?

Mon Feb 25, 2019 9:51 pm

Is there a part number or specification for the male 40 pin (2x20) header on the Pi 3B?

Is the mating surface gold plated? It is gold in color, but could be nickel plating or other material.

For long term reliability, we want to select a mating female connector for our HAT board that has compatible contacts.
Nickel on nickel or gold on gold .

Thanks
Mike

Some references:
https://www.microcontrollertips.com/gol ... -together/
https://www.connector.com/gold-or-tin-v ... d-and-tin/
https://blog.samtec.com/post/dissimilar ... onnectors/
Last edited by mkirk on Wed Mar 06, 2019 4:06 pm, edited 1 time in total.

Ebraheem Bambotia
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Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

Tue Feb 26, 2019 10:09 am

Mostly gold plated connectors are used in high precision and industrial electronic devices. I guess the GPIO is probably nickel or tin.

mkirk
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Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

Wed Mar 06, 2019 3:41 pm

I sent a query to the Pi Foundation support team to confirm - here is the response:

Thank you for your interest in Raspberry Pi.
It (header connector) is tin plated.
https://www.raspberrypi.org/products/ra ... 3-model-b/

Regards,
Nicola Early
Administrator

mkirk
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Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

Thu Mar 14, 2019 4:39 pm

Pi Foundation has update: header contact plating could be tin, gold or phosphor-bronze (copper-tin-phosphorus alloy)

Mike

It will depend on what version etc. It can be either tin plated, gold or phosphor bronze. We can't say which version will be on which Pi.

Regards
Nicola Early
Administrator
==========================================================
Sent: 07 March 2019 16:20
To: [email protected]
Subject: RE: Raspberry Pi enquiry - Something else #34820

Hi Nicola,

Is this tin plating on just the header tails (where it solders into the Pi PCB) - or over the full contact length of the header pins?
The contact portion of Pi header is yellow/gold in color, not silver. Tin plating is typically silver in color.

Our local Samtec engineer said Samtec sells a Pi connector kit with gold-flash contact plating, not tin.
So he was confused with your response saying tin plating was used on Pi.

A tin to gold contact has a high 1.64 volt galvanic potential, so long term reliability against corrosion/oxidation is not good.

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Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

Thu Mar 14, 2019 10:21 pm

mkirk wrote:
Wed Mar 06, 2019 3:41 pm
I sent a query to the Pi Foundation support team to confirm - here is the response:

Thank you for your interest in Raspberry Pi.
It (header connector) is tin plated.
https://www.raspberrypi.org/products/ra ... 3-model-b/

Regards,
Nicola Early
Administrator
Well, I'm not sure she understood the question, and I don't believe the contact areas of the pins are tin plated, only the solder area might be.
the contact area looks (flash) gold plated to me, but I am not a support team member, just a moderator, so what do I know. :geek:

the URL given does NOT point to a source of information that states the plating status of the header connectors.
But I have seen enough cheap tin plated pin headers, and they do not look the same as those of an RPI.

Ill try to contact Jamesh, he should know.

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Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

Thu Mar 14, 2019 10:26 pm

The type of plating will, from the post above, vary. We buy according to price, so depends on what fits the spec for the price at the time of purchase.

I don't think galvanic corrosion is going to be a problem.
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Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

Fri Mar 15, 2019 9:40 am

OK, quick poll round the office HW people.

If they look goldy, they will be gold flash plated. If they look tinny, they are tin plated. Somewhere in between probably phosphor bronze. i.e. it varies between models.

TBH, this is exactly what was posted above, so not sure why people didn't believe the post.
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Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

Wed Mar 20, 2019 9:08 pm

Jamesh, I am not questioning the post about the 3 types of plating. That is what I accept.

However, it will force us to buy 2 connector types (Gold and Tin plating ) to match the batch of Pi modules at the time of manufacture.
This increases our parts cost. (Phosphor bronze is copper-tin alloy and is compatible with tin plating).

The long term effects are what I am concerned about. We plan to use the Pi 3B in a product that comes with a 5 year warranty.
The enclosure will protected from the weather but will be subject to outdoor temperatures ( -20 C to + 50C ) and humidity.

This table from Samtec strongly recommends against mating gold to tin to prevent galvanic corrosion.
https://blog.samtec.com/post/dissimilar ... onnectors/

Can you disclose the part number and manufacturer of all the headers used on the Pi 3B?
I can review the data sheet for the parts and make an informed decision for our HAT module.

Regards,
Mike.

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Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

Wed Mar 20, 2019 9:13 pm

mkirk wrote:
Wed Mar 20, 2019 9:08 pm
Jamesh, I am not questioning the post about the 3 types of plating. That is what I accept.

However, it will force us to buy 2 connector types (Gold and Tin plating ) to match the batch of Pi modules at the time of manufacture.
This increases our parts cost. (Phosphor bronze is copper-tin alloy and is compatible with tin plating).

The long term effects are what I am concerned about. We plan to use the Pi 3B in a product that comes with a 5 year warranty.
The enclosure will protected from the weather but will be subject to outdoor temperatures ( -20 C to + 50C ) and humidity.

This table from Samtec strongly recommends against mating gold to tin to prevent galvanic corrosion.
https://blog.samtec.com/post/dissimilar ... onnectors/

Can you disclose the part number and manufacturer of all the headers used on the Pi 3B?
I can review the data sheet for the parts and make an informed decision for our HAT module.

Regards,
Mike.

May I ask why you are not using a Compute Module with Custom Baseboard for your product, that will allow you to know exactly the parts used ?
Rather than negativity think outside the box !

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Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

Wed Mar 20, 2019 10:51 pm

Primarily cost. Pi 3B is $35 and it includes WiFi/Bluetooth, Ethernet/USB, onboard antenna.

CM3 is $35 from Newark (USA) without WiFi/BT, Ethernet/USB chips
Plus the carrier board has the added cost of connectors: SIMM (CM3), Camera ribbon, Ethernet and USB.
All of these would add $15 to cost of CM3 to achieve same functionality as Pi3B.

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Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

Thu Mar 21, 2019 10:36 am

Many years ago, my employer sent me on a soldering course at Cranfield, where it was suggested that gold flashing was a really bad idea, and we should wash off the gold using copious amounts of solder.

It seems to me you have several choices.
Do nothing and live with the consequences.
Do as you suggest, buy 2 connector types (Gold and Tin plating ) to match the batch of Pi
Inspect the Pis and wash off the gold if necessary
- ditto - and change any connectors you don't like.

The pricing of your product must of course depend on production costs.
But any warranty you give is an integral part of your product, must be costed properly, and included in the price.
If whatever you choose to do results in a product that's likely to fail within your warranty period, resulting in replacements at your expense so eating into your profit, you can either increase your price to cover it, or reduce the warranty period to make it less expensive.

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Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

Thu Mar 21, 2019 10:49 am

Think it was stated above, but we cannot predict which header will be on which Pi at any one time. So you will have to assume you could be plugging in to any of the above.

For 5 years I do not think there will be problem anyway, with any of them.

Edit: Also, you pricing seems off. The CM3 should be loads cheaper than $35, in quantity, less than $20 each, unless you are getting the one with loads of EMMC.
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Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

Thu Mar 21, 2019 2:12 pm

Jamesh,

Thanks, I was not aware of the newly released CM3+ with the extra eMMC options.
I will bring this option up with our design team.

We started our design evaluation back in November 2017, the CM3+ was not available then.
The 4GB eMMC on the CM3 was not sufficient - we needed 16GB ( now available on CM3+).
Using CM3 lite would require us to add our own eMMC - pricing on eMMC for our target production (< 5K annual) was not cost-effective.
So we chose uSD cards and the 3B.

My other concern is thermal management for the CM3.
We need some type of heat spreader to conduct the heat to our external metal housing.
We do not have fan cooling option, just passive thermal management.

Our current plan with the 3B is using a mounting plate with circular bump-up under CPU
Non-electrically conductive thermal paste touches the 3B on the bottom - below the CPU.
Our preliminary tests show a 25C drop in CPU temperature vs. no heat sink/spreader when running the 3B CPU stress tool.

We would have to come up with a similar heat spreader design for the CM3.
Last edited by mkirk on Thu Mar 21, 2019 2:46 pm, edited 2 times in total.

Andyroo

Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

Thu Mar 21, 2019 2:35 pm

One thing that you may want to consider is the production life span of the units.

There is no guarantee that the Pi 3B will be available - where as the compute modules have an obsolescence statement (see https://www.raspberrypi.org/products/co ... plus-32gb/ for example).

The 3B for example has already had one change to the processor https://www.raspberrypi.org/app/uploads ... 3B-001.pdf and my guess is once the current crop of circuit boards are used up the supply will dry (TOTAL guess and I MAY BE WRONG - MYYW - YMMV)

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Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

Thu Mar 21, 2019 7:26 pm

mkirk wrote:
Wed Mar 20, 2019 9:08 pm
However, it will force us to buy 2 connector types (Gold and Tin plating ) to match the batch of Pi modules at the time of manufacture.
This increases our parts cost. (Phosphor bronze is copper-tin alloy and is compatible with tin plating).

The long term effects are what I am concerned about. We plan to use the Pi 3B in a product that comes with a 5 year warranty.
The enclosure will protected from the weather but will be subject to outdoor temperatures ( -20 C to + 50C ) and humidity.

This table from Samtec strongly recommends against mating gold to tin to prevent galvanic corrosion.
https://blog.samtec.com/post/dissimilar ... onnectors/
Hi Mike,

I believe your concern about the type of plating material on the header having to match your mating part may not be a big deal. Typically the concern with galvanic corrosion in something like a connector would be mostly with the change of the impedance of that connection. For typical uses of a Pi, I don't see this as an issue because the Pi can not work with analog inputs (trying to measure very small differences in voltages or currents) and typically won't be working with very high speed digital where the high speed switching behavior of digital signal could be effected by increased impedance through the connection.

Also note that the Samtec article you point to is purely speculation where they simply listed potential galvanic corrosion and then just simply state without data to back it, to avoid combinations outside their little colored areas that they seemed to have arbitrarily picked as being good or bad. Again I don't see any sort of backing data or study and their article to me looks a bit like a "we feel that" type article vs. a "we found in tests or studies that" type.

On the flip side, here is an actual study about this sort of thing...
https://www.digipas.com/documents/Effec ... ntacts.pdf

found that for the specific connectors they were checking, that gold plated contacts against tin plated contacts in ambient air didn't result in any measurable increase of contact resistance over the 1000 hours they ran their testing and certainly staying below the maximum contact resistance recommended. Granted this was a study done on a limited number of connector types and for only 1000 hours, but it is more than I see Samtec has referenced. And as I mentioned in the first paragraph for the types of typical applications you would use a Pi (not high speed, not instrumentation of analog signals), I don't see a gold plated connector used with tin plated contacts having a measurable impact on performance, even over five+ years.

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Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

Thu Mar 21, 2019 8:05 pm

If it's at all relevant, my TV aerial connector is gold plated and I"ve had a tin plated coaxial cable plugged into it for over ten years with no corrosion evident after checking it.
The gold was a little discoloured, but that was it.
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