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Board Assembly

A project log for Light Up Raccoons

A little coin cell powered raccoon with capacitive sensing to light up its eyes

savoSavo 02/02/2023 at 00:580 Comments

This was the first time I had ordered gold-plated boards (ENIG process), and damn were they more expensive, a scratch over triple what I usually pay per board. I think the cost was worth it though when I saw and held them.

The boards as they arrived.
The boards as they arrived.

Assembly

Assembling the boards was pretty basic, I just hand-soldered everything in place. In order to bring the DIP8 package for the ATtiny85’s close to the board I cut the leads a bit shorter with side cutters.

The assembled circuitry on the rear of the raccoon. Note: the wires were used for power delivery during programming.
The assembled circuitry on the rear of the raccoon. Note: the wires were used for power delivery during programming.

A minor side note, but I really like the look of parts on these gold-plated boards before soldering.

The ATtiny85 placed but not soldered
The ATtiny85 placed but not soldered

Plating the Belly and Eyes

Since we wanted the belly and eyes to be silver I had to hand coat them with solder. This was easier than expected although the belly cooled quickly so the soldering iron would leave “ripples” of solder as it moved across the surface, like a paint brush.

Hand soldered. Note the ‘brushes’ on the belly.
Hand soldered. Note the ‘brushes’ on the belly.

I found that if I applied hot air as I moved the iron I could prevent the rapid cooling and result in a smoother belly plating. The effect is quite similar to Hot Air Solder Levelling (HASL) typically done for cheaper boards.

Hot air used with soldering iron to result in a ‘smooth’ belly.
Hot air used with soldering iron to result in a ‘smooth’ belly.

I was a bit torn between the entirely hand soldered or air levelled belly coat. In the end, I hand soldered bellies for the ones I handed out since it was easier and I felt there really wasn't that perceptible a difference.

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