Homebrew PCBs

Wait a minute, how would you solder this?
If the pitch goes below a certain minimum it ough to be tricky to
solder without bridges?

ST

On Tue, Aug 2, 2011 at 9:08 PM, Stefan Trethan <stefan_trethan@...> wrote:
> 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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>>
>>
>>
>>
>