Sunday, January 25, 2009

More details on pcb desoldering centrifuge

So I did some more thinking about the pcb centrifuge. I've included some figures this time. The centrifuge rotor is a cup structure, likely made of high grade ductile (nodular) iron. There are 10-20 pcb compartments around the rotor. In each compartment, there is a clamp to hold the board in place, and the wall has blind stud/dowel holes for placement of "keeper" dowels or studs.On the wall there is stainless, brass, or copper gauze to act as both a part buffer and a sponge for dross/solder.

You put the board in, and then backfill the compartment with a low melting paraffin wax or a silicone oil. The wax or oil does 4 things:

  1. Prevents most solder oxidation.
  2. Acts as a viscous medium to slow part separation form board
  3. Prevents rapid temperature cycling of parts thereby minimizing risk of thermal shock.
  4. Acts as a heat transfer medium

See the figures:




And:


In the embodiment I'm thinking of, each compartment has an electrically resistive heater, either a potted into place heater or an element heater spot welded or brazed to the compartment walls.. Alternatively, you could circulate a heat transfer liquid through a "water jacket" machined/cast into the compartment housing.


1 comment:

  1. Hi

    I have thought about this for years, and considerable force is needed to remove through-hole components, like 10..100G. Filling the centrifuge with liquid would make it very heavy and expensive.

    Better use hot air, which can be blown into a spinning container.

    Also, each PCB would need a custom support structure to keep it in shape. This would best be done in a low-wage country where the components can be re-used.

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