Just tossing this out there for general information:
http://www.edn.com/electronics-blogs/the-workbench/4421218/PCB-layout-tips-for-thermal-vias
http://circuitcalculator.com/wordpress/2006/03/12/pcb-via-calculator/
http://m.eet.com/media/1200036/XLamp_PCB_Thermal.pdf
Those are examples of standard industry practice reference items for thermal via design. Even if not explicitly specified in 'build-to-print' any CM should:
a. Knowing the thermal needs for the A1 assumed maximum thermal transfer is needed meaning; heavy-plated thermal vias at a minimum preferably filled as well, and a full complement of thermal contact bumps on the bottom of the board that are high enough to go past the gap created by green screen layer to make firm mechanical contact with the main heat sink. btw, that layer creates a 3mil air gap. If there are a few bumps but not a full complement - that gap just got increased to 8-10mil. Thermal compound is not going to make up for that...
b. Flagged the above concerns and asked their customer to verify what is needed to meet industry-standard practice for working with high-power packages. If the customer is unsure then follow Best Practice and overkill the issue.
Then there is the matter of basic Ohms law... If the value of 1 component in a divider network is changed while leaving all others the same - the result (output) from that network is vastly different. To keep the network balanced all components need to be scaled by the same percentage..
I will leave it up to the Peanut Gallery to figure how this applies to us here
I will say that a power chip missing over 50% of its expected cooling path combined with getting hit (very briefly) with excessive core voltage is not long for this world... These are all items that any CM with a design team should have found in initial design review and later design change reviews and known how to address properly.
http://www.edn.com/electronics-blogs/the-workbench/4421218/PCB-layout-tips-for-thermal-vias
http://circuitcalculator.com/wordpress/2006/03/12/pcb-via-calculator/
http://m.eet.com/media/1200036/XLamp_PCB_Thermal.pdf
Those are examples of standard industry practice reference items for thermal via design. Even if not explicitly specified in 'build-to-print' any CM should:
a. Knowing the thermal needs for the A1 assumed maximum thermal transfer is needed meaning; heavy-plated thermal vias at a minimum preferably filled as well, and a full complement of thermal contact bumps on the bottom of the board that are high enough to go past the gap created by green screen layer to make firm mechanical contact with the main heat sink. btw, that layer creates a 3mil air gap. If there are a few bumps but not a full complement - that gap just got increased to 8-10mil. Thermal compound is not going to make up for that...
b. Flagged the above concerns and asked their customer to verify what is needed to meet industry-standard practice for working with high-power packages. If the customer is unsure then follow Best Practice and overkill the issue.
Then there is the matter of basic Ohms law... If the value of 1 component in a divider network is changed while leaving all others the same - the result (output) from that network is vastly different. To keep the network balanced all components need to be scaled by the same percentage..
I will leave it up to the Peanut Gallery to figure how this applies to us here
I will say that a power chip missing over 50% of its expected cooling path combined with getting hit (very briefly) with excessive core voltage is not long for this world... These are all items that any CM with a design team should have found in initial design review and later design change reviews and known how to address properly.There is always room to optimize and info was presented to AMT (although the task was to build Bitmine designs "as is" because they had a proven working design); however, the boards can and do work fine "as is" when assembled properly from a mechanical/thermal standpoint (not PCB Assembly/soldering standpoint). This is something that this CM was not responsible for as we did not have the capacity.