HMC8205 - How to keep the conductivity between PCB and heatsink strongly?

Hi RZM,

                  On the HMC8205 EVB, There is a milled pocked to accept the flange of the HMC8205. The HMC8205 rests on an Indium foil shim and the flange is screwed to the heat sink. The screws are fastened using a torque wrench to prevent over tightening and cracking the ceramic. 

During bench test we use thermal grease on the backside of the EVB heat sink/plate and clamp the EVB to a thermally controlled plate.

The mechanical plate used with the EVB has 4 thru holes and two threaded holes that can be used to mount an external heat sink. See attached.

Regards,

Jim B

Hi Jim,

Thank you for reply. I checked HMC1114 datasheet.

EVB is similer to HMC8205, but HMC1114 is CSP package and there is no GND flange (see below).

So, there is no cut out on PCB and heatsink needs not to have the role of connecting GND.

On the other hand, in HMC8205, heat sink is the only path for GND, so I am concerned about its connectivity.

Looking at the EVB picture, there is a silver substance attached between the PCB and the metal plate. Is it entirely soldered?

Hi Rzm,

                     I meant the HMC8205 data sheet. I edited my post above to reflect the HMC8205.

Regards,

Jim B

Hi RZm,

                  The PCB is either soldered to the plate or attached with conductive epoxy. The drawing specifies epoxy. The data sheet for the material is below. 

https://www.bondingsource.com/techdata/5025E.pdf

Regards,

Jim B

Hi RZm,

                  The PCB is either soldered to the plate or attached with conductive epoxy. The drawing specifies epoxy. The data sheet for the material is below. 

https://www.bondingsource.com/techdata/5025E.pdf

Regards,

Jim B

HI

As mentioned that the PCB is either soldered to plate or attached with conductive epoxy .

But the epoxy suggested here 5025E is not available with us , but we have an alternate product (datasheet  link attached) can we use this material for attaching HMC1114 PCB with heat sink ?

Looking forward to your response

https://www.epotek.com/docs/en/Datasheet/H21D.pdf

vidhi.raval,

                  The epoxy you reference is for die attach. I'm not sure this will be suitable for the board to heat sink application.

The epoxy  for EVB fabrication is a film epoxy sheet.

Regards,

Jim B

Hi

Thanks for the response.

We have checked for ABLEFILM® 5025E  but due to import constraint we are not able to indent the material.

Could you please suggest an alternate that is commercially available 

Looking forward to your response

Thanks

Hi,

      Solder is another alterative. Sheet solder 96.5 SN / 3.5AG. It comes in a sheet form. See attached photo.

Regards,

Jim B