Via Covering

Several technical or production-related demands require the covering / sealing of vias. In the following, you will find a comparsion of the technical capabilities. The reference is the IPC document IPC 4761, which can be purchased here: https://portal.ipc.org/Association/Index.htm.

Abstract

Type Description Covering-Material
I-a Tented one-sided Dryfilm solder-stop
I-b Tented double-sided Dryfilm solder-stop
II-a Tented & Covered one-sided Dryfilm solder-stop + LPI solder-stop
II-b Tented & Covered double-sided Dryfilm solder-stop + LPI solder-stop
III-a Plugged one-sided Plugging Epoxy (non-conducting paste)
III-b Plugged double-sided Plugging Epoxy (non-conducting paste)
IV-a Plugged & Covered one-sided Plugging Epoxy + LPI solder-stop
IV-b Plugged & Covered double-sided Plugging Epoxy + LPI solder-stop
V Filled Plugging Epoxy (non-conducting paste)
VI-a Filled & Covered one-sided Plugging Epoxy + LPI solder-stop
VI-b Filled & Covered double-sided Plugging Epoxy + LPI solder-stop
VII Filled & Capped Special Plugging Epoxy + plating

Via Tenting

  • IPC 4761 Type I-a: Tented Via one-sided
  • IPC 4761 Type I-b: Tented Via double-sided

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-a: Tented & Covered Via one-sided
  • IPC 4761 Type II-b: Tented & Covered Via doublesided

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

  Max. Drill-Ø
Via Tenting 300µm

Designation

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

Via Plugging

  • Via Plugging - IPC 4761 Type III-a
  • Via Plugging - IPC 4761 Type III-b

IPC 4761 Type III: Plugged Via

The via is partially filled with non-conductive paste.

One-sided: Type III-a
Double-Sided: Typ III-b

 
  • Plugged & Covered Via - IPC 4761 Type IV-a
  • Plugged & Covered Via - IPC 4761 Type IV-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

  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.

Via Filling

IPC 4761 Type V: Filled Via

IPC 4761 Type V: Filled Via

The via is filled completely with non-conductive paste.

 
  • IPC 4761 Type VI-a: Filled & Covered Via
  • IPC 4761 Type VI-b: Filled & Covered Via

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

IPC 4761 Typ 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.

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 via
Filled Via
filled capped via
Filled & Capped Via

Application

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

Parameters

  Min. Drill-Ø >> Pad-Ø   Max. Drill-Ø >> Pad-Ø
Via Plugging 100µm 300µm   500µm 700µm

Designation

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

Via-in-Pad

BGA without Via-in-Pad (Dog-Bone)
without Via-in-Pad
BGA with Via-in-Pad
with Via-in-Pad

The use of Via-in-Pad technology is increasingly influenced through the necessity of high-density BGAs (ball grid arrays) and the miniaturization of SMD chips.

With a reliable Via Plugging process, without enclosures of chemicals, it is possible to produce high-density PCB designs with Via-in-Pad technology, avoiding soldering errors.

Amongst other things, this faciliates additional conductor traces for BGAs (marked red in the picture).

We use this technology for years now and know how to ensure a reliable and safe production process.

Additional advantages:

  • Improved thermal dissipation
  • Increased voltage capability of the via
  • Provides a flat, coplanar surface
  • Lower inductance due to no dog-bone pads with traces
 

Pitch

Pitch for Via-in-Pad applications

The minimum pitch for Via-in-Pad solutions is 600µm.

This results of:

  • 200µm min. drill diameter
  • 400µm min. pad size
  •  50µm min. solder-stop clearance
  • 100µm min. solder-stop bridge
 

Workflow

  • Workflow Via Plugging - drilling
  • Workflow Via Plugging - plating-through
  • Workflow Via Plugging - selective plugging
  • Workflow Via Plugging - hardening
  • Workflow Via Plugging - polishing
  • Workflow Via Plugging - plating-over
  • Workflow Via Plugging - etching
  • Workflow Via Plugging - solder-stop

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