Best Practices for Rivets

[eric.bumbalough]

I have a very high failure rate when hammering in the 1mm rivets. Either I don’t fully seat them and they don’t make a good mechanical connection or I over do it and the nearby ink shatters. I end up with a huge amount of continuity testing and hand soldering to do to get it to work. What are the best practices for riveting? This is a classroom setting, and I really want to keep the process as simple as possible.

Here’s what I’ve been thinking of trying:

• Increasing the size of the pad around the hole. Hopefully this will increase the strength and prevent the ink from breaking. Or maybe it will just break off in larger chunks.
• Press in the rivets instead of hammering them to eliminate the sharp impact of the hammer.
• Solder paste the bottom pads, then reflow. I assume the softer solder paste will absorb some of the impact of the hammer and improve the electrical connection.

[sneaks]

I’m not sure the correct way, but I will share what works well for me. Over time, I’ve fine tuned my process and I have a 99% success rate with rivets.

The thing that made the biggest difference for me was using a piece of 1/4in thick aluminum to put under my PCB/Rivets before hammering. I install the Rivets, put the aluminum on top and flip it. Before hammering, I tape the PCB to the aluminum with painters masking tape so PCB doesn’t bounce and rivets don’t fall out. Have a look at the picture to see how nice the rivets turn out (and how flat they are).

I make my holes a tight fit with the rivets .7mm drill for .4mm Rivets and 1.6mm drill for 1mm rivets. I find even going to a .10mm larger results in problematic rivets.

I found the actual hammer makes a huge difference. This Hammer - Nylon end for .4mm Rivets, and Copper end for 1mm. I’ve never overdone it with this hammer.

Lastly, I put the board by my ear and run my finger over all the rivets. If they are not in right you can hear a very quiet click when you run your finger over.

Hope this helps.

[eric.bumbalough]

After further testing and many failed student projects, I’ve learned a little more about riveting but still can not repeatably make a good connection. My students all tried with a hammer similar to what was recommended above with no success. I’ve tried to set the rivets with an arbor press and that was also unsuccessful.

What I have learned is that the baking processes cause discontinuities. On several occasions I’ve had continuity before heat treating (either reflow or baking repair ink) and not had continuity after.

[sneaks]

I’m curious - did you try putting a block of aluminum under the board when hammering the rivets? Since I started doing the above process I’ve had zero issues with rivets. I will say though, the aluminum beneath the board is key. If I do the exact process above on a wood workbench, half my rivets don’t work.

[mixer]

I just use one of the FR1 boards and put that underneath. 3 taps I’m done.

[eric.bumbalough]

Some of these were aluminum anvil, some were steel anvil, and some were on FR1 as Voltera suggests. I haven’t been playing close enough attention to which anvils led to the failures so you may be right.

I also notice from your photos that your pads under the rivets are much larger than ours.

[AlanDewey]

I do not have a block of aluminum to try as “sneaks” uses. But after considering how that helps, found my problem with rivets.

First I found a hammer with the plastic ‘head’ as suggested. Then I discovered that one workbench had a very high failure rate.

Now, I place the board on the heaviest workbench, directly above the 2x4 leg. What I am guessing is the shockwave from the hammer goes straight down through the leg into the concrete floor. Contrast this to my first workbench which has a bit of flex.

I can not explain it, but it made a big difference for me.