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
| Type | Description | Covering-Material | Available | Multi-CB Recommendation |
|---|---|---|---|---|
| I-a / -b | Tented 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 / -b | Tented & Covered one-sided (a) / double-sided | Dryfilm solder-stop + LPI solder-stop | - | II-a Not recommended, long-term reliabilty risk II-b Not recommended, hollows may be a concern |
| III-a / -b | Plugged 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 / -b | Plugged & Covered one-sided (a) / double-sided (b) | Plugging Epoxy + LPI solder-stop | o.r. | VI-a Not recommended, long-term reliabilty risk VI-b Recommended |
| V | Filled | Plugging Epoxy (non-conducting paste) | + | Recommended |
| VI-a / -b | Filled & Covered one-sided (a) / double-sided (b) | Plugging Epoxy + LPI solder-stop | + | Recommended |
| VII | Filled & Capped | Plugging Epoxy + plating | + | Recommended |
Via Covering Types according to IPC
IPC 4761 Type I: Tented Via
The via is completely covered with dryfilm solder-stop.
One-sided: Type I-a
Double-sided:Typ I-b
IPC 4761 Type II: Tented & Covered Via
The via is completely covered with dryfilm solder-stop and overprinted with normal solder-stop, afterwards.
One-sided: Type II-a
Double-sided:Type II-b
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.
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-stop, afterwards.
One-sided: Type IV-a
Double-sided: Type IV-b
Multi-CB 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 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 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-stop, afterwards.
One-sided: Type VI-a
Double-sided: Type VI-b
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.
Parameters
| Covering | Min. Drill-Ø | >> Pad-Ø | Max. Drill-Ø | >> Pad-Ø | Aspect ratio | |
|---|---|---|---|---|---|---|
| Filled & Capped IPC 4761 Type VII | 150µm | 350µm | 400µm | 600µm | 1:12 | |
| Filled & Capped electroplated | 100µm | 300µm | - | - | 1:10 |
Designation
Copy the vias to be plugged into an additional layer and define that layer with your order.