The top and bottom components of double-sided printed circuit boards (PCBs) can have different thermal masses and therefore, absorb heat at different rates. During reflow soldering, the component with the smaller thermal mass rises and falls in temperature relatively fast, causing PCB warpage and damage of solder joints. This disclosure describes techniques to equalize the thermal masses of the top and bottom components of a printed circuit board by modifying the PCB and component geometry. Balancing of thermal masses can be achieved by adding or modifying the layers in the package substrate and the PCB to allow for a larger thermal mass to be ascribed to smaller components. The techniques enable highly reliable reflow soldering with well-soldered joints and a reduction or elimination of PCB warpage.
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n/a, "Reliable Assembly of Double-Sided or Clamshell BGA Devices", Technical Disclosure Commons, (June 12, 2022)