I think resonant refrigeration is cool. Sounds to me like one of the
real innovations that may lead to actual useful products.
That stacking idea could actually work, having seen PCBs cut and
polished that is exactly what you get. You'd have to use suitably thin
prepregs or something between the copper to get the wanted pitch. But
how would you contact the "far side" of the conductor stack? Would you
just fan it out in some way?
Are you sure the die comes with solder bumps and not bond pads like
silicon chips? I know nothing about GaN.
ST
On Tue, Aug 2, 2011 at 7:35 PM, shoestring <don@...> wrote:
> Hello HPCBers,
>
>
> I've this special project that requires some innovation to be practical
> on my budget.
>
> The gallium nitride transistor is new, invented by a grad student in
> 2006, and used by the military. The cost of packages that exploit the
> ultra-fast dV/dt (4 volts per nanosecond) is upwards of $200 each. I've
> seen as high as seven-hundred dollars for a GaN in a high-current package.
>
> Good news... the raw die, with solder-bumps for reflow-soldering, is
> available for around $5 each (five bucks).
>
> However, standard circuit board surface mounts will not celebrate the
> GaN transistor's chiefest qualities --speed. My personal project (as a
> retired programmer), a resonant refrigerator, depends on short, high
> power pulses beyond what a MOSFET can do... enter the GaN transistor.
>
> I've a design that is innovative, I reckon. It involves producing the
> 0.025 millimeter circuit-board landing pads for reflow soldering by
> stacking copper foil of the same thickness, with the insulation path
> between pads filled with epoxy. The completed lamination is sawn into
> small strips and polished, and the laminations on the edge become the
> landing pads for the GaNs.
>
> I've 3D perspective illustrations if anyone is interested. What I'm
> hoping to find is an EE perspective of the necessary things, like solder
> masking the tiny buss, and things I'm unfamiliar with. I am proceeding
> slowly, shoestring budget in force.
>
> Testing is also needed, and I'm learning the details of RF as I go...
> all advise is special.
>
>
> Thanks,
> AZdon
>
>
>
>
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>
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