Via plug is a PCB manufacturing technology in which the via is filled with solder mask or other non-conductive/conductive material. In this process, the via holes are closed partially or completely to improve reliability of the printed circuit boards during usage or soldering quality. Via plug is more and more commonly used in high standard PCBs, especially the ones with BGA assembly.

Viasion offers a variety of via plug requirement in our PCB production, such as vias tented by solder mask, vias plugged/filled by solder mask, vias plugged by conductive and non-conductive material, vias plated shut by copper (via-in-pad) etc.

Our experienced engineering team will be helpful to advise the best via plug options which are suitable to your products. To make sure your products to have best quality and most competitive pricing.

What is via in PCB

Vias are the small holes which are platted by copper to connect the copper traces between different layers. Vias can be plated through vias, blind vias or buried vias. 

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    What are the normal types of via plug

    There are different kinds of via plug. In Viasion, we can produce PCBs with Conductive via plug, non-conductive via plugging by solder mask or epoxy, and Via plated shut by copper. 

    Via tenting by LPI Solder Mask

    Plated through Vias are covered by LPI Solder Mas from one side or both sides of PCBs. There is not extra process than, just cover/tent the vias by LPI solder mask when printing solder mask.

    Advantages:

    • No extra cost
    • Helpfully to prevent solder leak in SMT process
    • Helpful to prevent dust or liquid in usage

    Disadvantages:

    • Vias may not be totally covered/tented
    • Not suitable for via plug in BGA area
    • Limit to vias, vias better less than 0.3mm, and max. 0.5mm.

    Via plugging by Solder Mask

    A extra process will be needed to plug the via especially. Vias can be plugged just one side or double side. Some times solder mask will be applied again on the vias which are already plugged.
    Advantages:
    • Very little extra cost
    • Almost 100% vias are plugged
    • Helpfully to prevent solder leak in SMT process
    • Helpful to prevent dust or liquid in usage

    Disadvantages:

    • Not suitable for via plug in BGA area

    Non-conductive via plug

    Vias are plugged by specially material, mostly epoxy, to make sure the vias are 100% plugged. Which is very commonly used in the PCBs which BGA area. Because the space in the BGA area is too small to add more vias and design “dog bone” , so via need be drilled directly into the BGA pad, then signals are transferred from the BGA pad to a via and then from the via to the other layers/traces. We also call these kinds of pads as “Active pad” and can the technology as “Via in Pad”.

    Advantages:

    • 100% prevent solder leak in SMT process
    • 100% prevent dust or liquid into vias in usage
    • Very good stability and reliability

    Disadvantages:

    • Extra cost
    • PCB manufacture should have enough experience and equipment

    Conductive via plug

    Comparing non-conductive via plug, the Vias are plugged by special conductive material to make sure the vias are 100% plugged.
    Advantages:
    • Good at heat sink or transfer
    • Better current carrying capacity due to higher thermal conductivity
    • 100% prevent solder leak in SMT process
    • 100% prevent dust or liquid into vias in usage
    • Very good stability and reliability

    Disadvantages:

    • Higher cost
    • Suitable plug material should be chosen to avoid via fracture
    • No high demand

    Via plated shut by copper

    Rather than filling the vias firstly by conduction or non-conductive material, vias are totally plated shut by copper. But due the difficulty in production and higher cost, this type of via plug are not commonly used any more.
    Advantages:
    • Good at heat sink or transfer
    • Better current carrying capacity due to higher thermal conductivity
    • 100% prevent solder leak in SMT process and dust/liquid run into vias
    • Very good stability and reliability

    Disadvantages:

    • Very high cost
    • Imitation in vias size and copper thickness
    • No high demand

    Introduction for IPC 4761-Guide for PCB via protection types

    In PCB manufacturing process, we always follow IPC 4761 for via plug standards. Please refer to the following explanation of IPC 4761, which is the ultimate Design Guide for Protection of Printed Board Via Structures. 
    IPC-4761  TypeDescriptionIPC-4761 IllustrationMaterial usedReliability Cost Available
    Type I-ATented Vias- Single-SidedDry FilmlowlowNO
    Type I-BTented Vias- Double-SidedDry FilmlowlowNO
    Type II-ATented And Covered via –Single-SidedDry Film/LPI Solder MaskmediumlowYES
    Type II-BTented And Covered via –Double-Sided Dry Film/LPI Solder MaskmediumlowYES
    Type III-APlugged via– Single SidedLPI Solder Mask Or ResinmediumlowYES
    Type III-BPlugged via- Double SidedLPI Solder Mask Or ResinmediumlowYES
    Type IV-APlugged And Covered via- Single-SidedLPI Solder Mask Or EpoxymediumlowYES
    Type IV-BPlugged And Covered via- Double-SidedLPI Solder Mask Or EpoxymediumlowYES
    Type VFilled via(Fully Plugged)Conductive Or Non-Conductive MaterialHighmediumYES
    Type VI-AFilled And Covered via– Single-SidedConductive Or Non-Conductive Material + LPI Solder Mask HighmediumYES
    Type VI-BFilled And Covered via  –Double-SidedConductive Or Non-Conductive Material + LPI Solder MaskHighmediumYES
    Type VIIFilled And Capped by copper Conductive Or Non-Conductive Material+Copper platingHighHighYES
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