Via Protection

Several technical or production-related demands for PCB manufacturing require via protection. These types of via covering are possible:

• Simply Covering: Via Tenting or Tented Vias
• Partially Filled: Via Plugging or Plugged Vias
• Completely Filled: Via Filling or Filled Vias

 

In the following, you will find a comparison of the technical capabilities of via covering protection. The reference is the IPC-4761 [Design Guide for Protection of Printed Board Via Structures]. The following chart is a summary of the different types of via plugs called out in this document, which reflects the IPC effort to standardize the via covering protection process:

 

 

Via Tenting

 

IPC-4761 Type I: Tented Via

Dry film solder mask is stretched over the Via. No other materials are added.

 

One-sided: Type I-a

Double-sided: Type I-b

 

IPC-4762 Type II: Tented & Covered Via

The via is completely covered with dry film solder mask and overprinted with normal solder mask, afterwards.

 

One-sided: Type II-a

Double-sided: Type II-b

 

Application

• Protect of solder paste floating up to the component side
• Enables vacuum-adaption for production
• Covering of critical vias, e.g. beneath BGA

 

Alternatives

You can apply Via Filling, alternatively in via protection.

Through cutting the solder mask clearance, you can ensure a sufficient solder mask bridge for BGAs. Using this method, the via annular rings will be partly covered with solder mask.

 

Parameters

 

Designation

It is sufficient to cover the vias within the solder mask layer.

 

Via Plugging

 

IPC-4761 Type III: Plugged Via

The via is partially filled with non-conductive paste.

 

One-sided: Type III-a

Double-sided: Type III-b

IPC-4761 Type IV: Plugged & Covered Via

The via is partially filled with non-conductive paste and overprinted with normal solder mask, afterwards.

 

One-sided: Type IV-a

Double-sided: Type IV-b

 

Multi-layer PCB recommends one-sided plugging (Type III-a / Type IV-a) as there is a chance of cracks through encapsulated gas while soldering double-sided plugged vias..

 

Application

• Protection of solder paste floating up to the component side.
• Enables vacuum-adaption for production.

 

Parameters

 

Designation

Copy the vias to be filled into an additional layer and define that layer with your PCB fabrication notes.

 

Via Filling

 

IPC-4761 Type V: Filled Via

The via is filled completely with non-conductive paste.

 

IPC-4761 Type VI: Filled & Covered Via

The via is filled completely with non-conductive paste and overprinted with normal solder mask, afterwards

 

One-sided: Type VI-a

Double-sided: Type VI-b

 

IPC-4761 Type VII: Filled & Capped Via

The via is plated-through and cleaned -afterwards a non-conductive paste is forced in and hardened -the ends are planarized, metallized and plated-over. Hence, the surface is planar and solderable.

Via Filled and Capped Technology is mostly used for Via-in-Pad (VIP) solutions and is also applied for stacked and staggered via & microvia in HDI boards. Via plugging facilitates routing of additional conductor traces between BGA vias amongst other things.

Filled & Capped Vias are also possible for Blind Vias.

 

Application

• Space saving
• Protection of solder floating up to the component side.
• Protection of solder floating up to the component side.
• Facilitates stacked and staggered Microvia for sequential build-up (SBU) multilayers.
• Facilitates Via-in-Pad Technology, e.g. for BGAs.

 

Parameters

*Filled & Capped Vias blind vias have an aspect ratio of 1:1.

 

Designation

Copy the vias to be plugged into an additional layer and define that layer with your solder paste.

MADPCB strongly recommends that all vias be tented, filled and/or capped, especially under BGA packages according to IPC-4761 covering protection.