Windows 10 installation using Boot Camp crashes in iMac with 'system thread exception not handled (igdkmd64.sys)'
I would recommend downloading BlueScreenView or WhoCrashed to scan for minidump files and find out what caused this BSOD error. Based on the igdkmd64.sys, it's actually related to Intel Graphics driver.

carrona.org/drivers/search.php?id=igdkmd64.sys

But if you have tried uninstalling this driver and still getting this problem due to Windows forces itself to redownload and reinstall, then I would recommend you do it manually. That means go to:

downloadcenter.intel.com/Default.aspx

find for the driver, download and reinstall manually.

Besides, in some other cases, corrupted system files are also the cause that creates this BSOD error.

Source: How To Fix System Thread Exception Not Handled Error