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Via Covering

Several technical or production-related demands require the covering / sealing of vias. A basic distinction is made between the following methods:

  • Via Tenting (covering) or overprinting the vias with-solder stop
  • Via Plugging (partially filled)
  • Via Filling (completely filled)

In the following, you will find a comparsion of the technical capabilities of Multi-CB.

The reference is the IPC 4761, which can be purchased here: https://shop.ipc.org/.

For the sake of completeness, via covering IPC 4761 Type I and II (tenting) are also listed below, which we do not offer. As the cost and benefit are disproportionate, we offer our customers the following alternatives:

  • Overprinting the vias with solder-stop (one-sided covering). To do this, simply do not set an exemption in the solder mask in your data.
    However, the vias can remain open and solder resist can get into the through-hole plating.
  • Filled & Covered Via IPC 4761 Type VI. Process-safe closure of the vias.

Instead of IPC 4761 type III / IV (plugging), we recommend IPC 4761 type V / VI (filling).

For via-in-pad and covering of blind vias, IPC 4761 type VII (filled & capped) should be selected.

Abstract

TypeDescriptionCovering-MaterialAvailableMulti-CB Recommendation
I-a / -bTented one-sided (a) / double-sided (b)Dryfilm solder-stop-I-a Not recommended, long-term reliabilty risk
I-b Not recommended, hollows may be a concern
II-a / -bTented & Covered one-sided (a) / double-sidedDryfilm solder-stop + LPI solder-stop-II-a Not recommended, long-term reliabilty risk
II-b Not recommended, hollows may be a concern
III-a / -bPlugged one-sided (a) / double-sided (b)Plugging Epoxy (non-conducting paste)o.r.III-a Not recommended, long-term reliabilty risk
III-b Not recommended, paste partially covers annular ring
IV-a / -bPlugged & Covered one-sided (a) / double-sided (b)Plugging Epoxy + LPI solder-stopo.r.VI-a Not recommended, long-term reliabilty risk
VI-b Recommended
VFilledPlugging Epoxy (non-conducting paste)+Recommended
VI-a / -bFilled & Covered one-sided (a) / double-sided (b)Plugging Epoxy + LPI solder-stop+Recommended
VIIFilled & CappedPlugging Epoxy + plating+Recommended

Via Covering Types according to IPC

Application

  • Protection of solder 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.

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

Parameters

Covering Max. Drill-Ø
Via Tenting 300µm

Designation

It is sufficient to cover the vias within the solder-stop layer.

Application

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

Parameters

Covering Min. Drill-Ø Max. Drill-Ø
Via Filling 250µm 500µm

Designation

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

IPC 4761 Type VII: Filled & Capped Via

The via is plated through and then cleaned. Afterwards, a non-conductive resin paste is then pressed in and cured. The resin paste is planarised and metallised at the entry and exit points of the copper sleeve. The surface directly above the via is therefore flat and solderable.

This technology is mostly used for Via-in-Pad solutions and is also applied for stacked und staggered (Micro-)vias. Via Plugging faciliates routing of additional conductor traces between BGA vias amongst other things.

Filled & Capped Vias are also possible for Blind Vias.

Application

  • Reliable, complete coverage of vias and annular rings with solder-stop
  • Space saving: enables via-in-pad technology, e.g. for BGAs
  • Protection against solder penetration to the component side
  • Enables stacked and staggered microvias for sequentially manufactured multilayers (SBU)

Parameters

Covering Min. Drill-Ø >> Pad-Ø Max. Drill-Ø >> Pad-ØAspect ratio
Filled & Capped
IPC 4761 Type VII
150µm350µm400µm600µm1:12
Filled & Capped
electroplated
100µm300µm--1:10

Designation

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