Soldering header to RPi zero - heard a 'ding' noise while soldering

I know there is a plethora of information regarding soldering. I know how to solder and solder well. I have no problem soldering generally.

However in the case of soldering the header, despite cleaning the pads of the RPi Zero with iso-propyl alcohol (sold in 1L bottle by Core) and drying it, I had difficulty in having the solder to stick to the header and pad.

Yes, I used blu-tack to ensure that the header is flat, and soldered the top end and bottom end pads.

For some reason unique to soldering RPi board headers, I had difficulty in applying the heat and solder on the header and pad and having ugly soldering joints. I managed to remove the excess solder without “Solder wick”, but by a gentle tap of the board.,

Inspecting the final soldering job, there are no blobs and shorts between the headers pins. The solder joints appear satisfactory.

At the same time, I am concerned that on one occasion during the difficulty of soldering some pads, I heard a ‘ding’ sound while soldering. I am concerned that heating may have caused an open circuit inside one of the PCB 's layers.

My question is: I have a diagram of the 40-pin pinout of the header. BUT want to know where on the RPi zero are the pinouts connected to. I want to use a multimeter to check for any open circuits.

Again I would like to know how the header is connected to the rest of the PCB so I check for open circuits. I don’t know if I can get a lead or a pigtail (from a component) to use as a lead when taking measurements. Any advice on small enough leads?

Thank you
Anthony of Sydney

Hi Anthony,

It sounds to me like you need a hotter soldering iron, but its hard to say without seeing the results or seeing you in action.

I think you will be hard pressed to check the pins for open circuits. Your best bet is to plug it in and see if it still works. You can find the wiring diagrams here:

I would use some regular jumper wires to use as pigtails.

Thanks Stephen the reply.
One question and one point please.

On the question of soldering, I had the temperature set to 312degrees Celsius. Should I increase that to say 330?

On the GPIO connections. amongst other connections, the GPIO has the pinouts. What I wanted was the diagram between the IC handling the GPIO and the GPIO in order to check for continuity. My search has resulted in a lot of pinout diagrams but not schematics showing the pintout of the GPIO and the devices.
That would be appreciated.

Thank you,
Anthony of Sydney


I would keep the temperature between 330 and 350 degrees. Start at 330 and see how it goes and increase it if needed. I personally like to use a hot soldering iron with very short contact time, but that can be a higher risk.

I don’t think you will find a diagram that will allow you to do resistance checks on the pins. While the software is open source, the hardware is not. There is too much going on internally to check your Pi that way anyway I think. The schematic that I shared with you is probably the best that you will find.

I tend to prefer a temperature around the 330-350 mark as well, however you have to be careful not to keep the soldering iron on the pads too long or you can easily overheat them and cause the track to seperate from the board. (I have done this on more than one occasion and it is never fun.) I wonder if the ding Anthony heard was the track pinging loose?

A suggestion might be to use some extra flux before soldering. I use a flux pen (Core Electronics sell a couple of different types) to “paint” a little flux on the pads and that can really help the solder stick.

Another suggestion for the Pi Zero is to use the Pimoroni Hammer Headers - dead easy to use and relatively inexpensive.

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Assuming you are using leaded solder, I would recommend 350C.
To test for continuity/damage, I would write a simple program that just toggles each pin.

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