About the SinkPad copper core PCB, all is known that convexity is very important, the height of convexity is about 0.2mm-0.25mm.To get more news about BT PCB, you can visit pcbmake official website.

We need to know what's the reasons caused the gap between the convexity and LED pad is big.

We make the copper core with convexity firstly, then make the circuit/panel board (FR4PCB/BT PCB) and finally do the lamination for cooper core and circuit board.
The tolerance for convexity is +/-0.05mm-0.075mm.
The tolerance for circuit/panel board is +/-0.13mm.
If we do negative tolerance for convexity and positive tolerance for circuit/panel board, then it will cause the gap very big.

See below picture and details.

For example, the size of convexity is 0.5mm, after negative tolerance -0.075mm, it will be 0.425mm and each side will be 0.0375mm smaller.

For the circuit/panel board, the gap between convexity is 0.2mm, after positive tolerance +0.13mm, it will be 0.33mm and each side will be 0.065mm bigger.

So finally, the gap will be 0.2mm+0.0375+0.065mm=0.3025mm. It is about 50% bigger than original size.For example, the size of convexity is 0.5mm, after negative tolerance +0.075mm, it will be 0.575mm and each side will be 0.0375mm bigger

For the circuit/panel board, the gap between convexity is 0.2mm, after positive tolerance -0.13mm, it will be 0.07mm and each side will be 0.065mm smaller.