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I'm redesigning a product for automatic assembly (DFA / DFX). The current product includes a lithium polymer battery with solderable leads, very similar to this:

enter image description here

Right now the leads are hand-soldered.

How do I make this into something that can be assembled automatically?

I don't think there is any battery like this that can survive reflow, so it has to be added after the main pcb is assembled. There are batteries with JST connectors (adds cost, and still wouldn't be easy to automatically plug in), and batteries with metal foil tabs (no protection circuit - it would have to be on the other pcb; and the tabs probably have to be hand soldered anyway).

I'm sure this is a very common problem in the manufacture of small wearable devices like mp3 players and bluetooth headsets, but how do people usually solve it?

P.S. It turns out everything else in the product can be assembled by (essentially) pick and place: picked up with a vacuum tip and dropped in from above. The parts drop onto alignment pins in the bottom half of the case, then the top half of the case snaps on.. the battery is the one headache.

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Ask the battery supplier to provide the battery protection PCB (the PCB at the end of the battery) with contacting areas, and use "pogo pins" (i.e. "spring-loaded contacts") on your PCB. You'll then only need to make sure that the enclosure of your device presses the board onto these pins without exerting pressure on the cell itself (don't mechanically stress Lithium batteries for explosive reasons).

But really, I'd presume that, yes, the cheapest way here is hand-soldering. I don't know how your PCB ends up integrated mechanically in the end product, to be honest, and that's the step where an additional attachment action probably could happen, anyway, so I like the connector idea – especially since batteries with connectors are produced in large quantities, so you could benefit from economics of scale and don't come out that much more expensive.

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  • \$\begingroup\$ Thanks! I was thinking along similar lines. It's too bad to have plugging in the connector be manual, but maybe unavoidable. Re: "how your PCB ends up integrated mechanically in the end product" - it drops onto four alignment pins in the case, has four pogo pins for electrical contacts, and some push button covers dropped on top of it, then the top of the case presses it down. \$\endgroup\$ – Alex I Nov 18 '18 at 22:44
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Typically, cells with tabs or pigtail wires are hand-soldered. This holds for coin cells with tabs, pouch cells with tabs.

The rest are only brainstorm thoughts. I've never implemented any of this in a project.

  • It may be possible to do selective wave soldering for a coin cell with throughole tabs.
  • It may be possible to spot-weld the tabs, if you can find a contract manufacturer with right equipment.
  • It may be possible to glue the cells with conductive epoxy.

Discrete wires [aside from the temperature limit imposed by the cell] can be wave-soldered to the PCB. Before the wave, however, wires are inserted into the PCB by hand.

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