非金属化孔 meaning in English

unsupported hole

Printed boards . part 4 : specification for single and double sided printed boards with plain holes
印制板.第4部分:具有非金属化孔的单面和双面印制板规范
Printed boards ; part 4 : specification for single and double sided printed boards with plain holes ; amendment 1 to iec 60326 - 4 : 1980
印制板.第4部分:具有非金属化孔的单面和双面印制板规范.第1次修改
Printed boards ; part 4 : specification for single and double sided rigid printed boards with plain holes ; identical with iec 60326 - 4 : 1980 status as of 1989
印制电路板.第4部分:带非金属化孔单面和双面印制电路