Hello Technet, I am looking to understand if there is an IPC standard where is specified the minimum number of prepreg foils that should be put between two PCB layers. I know that IPC 6012C (par. 3.6.2.15) specify that the minimum dielectric spacing is 90um and that the supplier choice the number of prepreg layers, but I was wondering if there are other standards that may specify this statement. I have a case where a Customer is expecting that a minumum of two prepreg foils should be put between copper layers. Does anyone know in which IPC standard I can find criteria where is stated that a minimum of two prepreg foils should be used and why ? Which benefits ? Thanks in advance for your help. Best Regards Francesco Francesco Di Maio GEST labs - Via Kennedy Ingresso 2, 20871 Vimercate (MB) - Italy E-Mail:[log in to unmask] ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________