Hi Guys,
It was a total failure that my chip was COB packaged for the first time. The package house ensured that they can do COB even if the pad pitch is as small as 35um. So we used stagger I/O to put more pads on the chip. Then we found most chips were short or open after they are COB packaged.
It is a little lucky that the COB package successed for the second time. I chose inline I/O, and make the pad pitch is about 120um. 3 chips are COB packaged in another package house. One was short between power and ground. I didn't check it. The other two works fine.
I found the requirements are so different for each package house. And they use different material, like the glue covering the chip. Sometimes they don't cover the chip. Would you please introduce any literature, application notes, books on COB technique? Especially the material's effect on the electrical performance, the relative PCB layout, etc.
Best regards,
Yawei