Homebrew PCBs

I understand the mounting concept you have described, but I don't know how to implement it, yet.  I do have a question though.  The die for the transistor is normally mounted in a package and then the package is mounted on a heatsink.  How do you plan to dissipate the heat in this application?  You will also need to cover the die with something, most likely a safe epoxy compound, to protect it from damage and contamination.

Stuart

  ----- Original Message ----- 
  From: shoestring 
  To: Homebrew_PCBs@yahoogroups.com 
  Sent: Tuesday, August 02, 2011 10:35 AM
  Subject: [Homebrew_PCBs] newbie toons


    
  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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