What is ipc 4671 Via? is divided into several?

 IPC 4671 Via have Type I-VII;IPC I-III ,IV,VI have type-a and type-b.Type-a means single side Type-b means both side

Tented Via (Type I Via a/b):A via with a dry film mask material applied bridging over the via where in no additional material in the hole,It may be applied to one side(Type-a)or both side(Type-b) of the via structure

Tented and covered Via(Type II Via a/b):A Type I via with secondary covering of mask material applied over the tented via,this process applied benefit will improved strength over Type I.

Plugged Via (Type III Via a/b):A via with material applied allowing partial penetration into the via

Plugged and Covered Via (Type IV via):A Type III via with secondary covering of material applied the via

Filled Via(Type V via)；A via with material applied into the via targeting a full penetration and encapsulation of the hole.This process(screemed roller-coated,or squeegeed) benefit will complete fill of conductive or non-conductive material which eliminates contaminants.Process prevent solder balling and useful in sequential lamination processes

Filled and covered Via(Type VI Via a/b):A Type V Via with secondary covering of material applied the via(liquid or dry film solder mask)

Filled and Capped Via(Type VII Via)；A Type V via with secondary metalized coating covering the via.The metallization is on both side.This process benefit in Via in pad and Ball on Via pad,Via stacking,Applicable where high density features are required