HDI PCBS

Perfect for higher packing densities

Background

With High Density Interconnect (HDI) technology, higher packing densities can be realised for electronic components. HDI PCBs offer finer conducting structures and smaller plated through holes. The microvias create space as well as offering improved electrical properties in comparison with traditional plated through holes or blind vias.

Due to the connection of multiple layers, signals can be conducted to the inner layers and be rewired there without blocking the space for components with a high pin density. Depending on the layout, it is even possible to position these components on the PCB with an opposite overlap. Thin PCBs with structures of 100 µm and 125 µm enable controlled impedance conductors for high frequencies.

Applications

  • Battery switches
  • Power distributors
  • Motor controls
  • LED applications
  • Control, automotive, satellite, microsystems, and industrial technology
  • Communications electronics
  • Camera & video monitoring systems for autonomous driving

Benefits

  • FR4 or a higher quality base material
  • Microvias enable finer layout structures
  • Microvias can be used as single microvias, staggered vias, stacked vias, and skipped vias
  • Wide range of layout design possibilities
  • Precise and controlled mechanical deep drilling rounds off the technical possibilities for HDI

Special features

  • Can be enhanced with other SCHWEIZER products
  • Different layer connections possible using blind vias and buried vias
  • High layer density of up to 18 layers

Cross section of a 3-8b-3-HDI PCB with staggered vias, blind vias, and buried vias

Schematic layout of a 2-4b-2-HDI PCB with blind vias, stacked vias, buried vias, and via holes

Parameter

Standard

High standard

Number of layers

1-18

>18

HDI lay-ups

Up to 3 x 3

4 x 4

PCB thickness

0.6-3.2 mm

0.6-3.2 mm

Maximum PCB size

584*575 mm²

584*575 mm²

FR4 materials: Glass transition temperature

140°C, 150°C, 170°C

>170°C

Glass fabric

106, 1080, 2116, 7628

 

Copper foils

18 µm, 35 µm, 70 µm, 105 µm

210 µm, 400 µm

Inner layer thickness

75 µm, 100 µm, 150 µm, 200 µm, 360 µm, 510 µm, 710 µm, 1000 µm, 1300 µm, 1500 µm

50 µm

Min. track width and conductor spacing of outer layer*

70 µm / 70 µm

60 µm / 60 µm

Min. track width and conductor spacing of inner layer*

60 µm / 60 µm

50 µm / 50 µm

Smallest mechanical drill diameter

0.2 mm

0.15 mm

Aspect ratio

1:6

1:8

Min. laser drill diameter

125 µm

110 µm

Landing pad diameter

330 µm

250 µm

Laser via aspect ratio

1:1.5

1:1

Dimple

>25 µm

0 – 25 µm

Outer layer annular ring

150 µm

100 µm

Inner layer annular ring

200 µm

150 µm

Min. solder mask dam*

80 µm

50 µm

Solder mask color

Green, white, black

Blue, red

Final finishes

Imm. tin, OSP, imm. NiAu (ENIG), imm. NiPdAu (ENEPIG/ENEPAG), Plated NiAu, HAL, Bond Gold, Hard Gold

Imm. silver

Legend print color

Yellow, white, black

Blue, red

*: Values dependent on copper layer thickness

"Blind via" is a general term for a hole starting from the surface of the PCB that does not contact all the way through to the opposite outer layer. A common usage is a laser hole from layer 1 to layer 2, for example. Depending on the diameter, the laser holes are infused or completely filled with copper.

 

Design rules for laser blind via:

Parameter

Standard

High standard

Min. laser drill diameter

125 µm

110 µm

Landing pad diameter

330 µm

250 µm

Laser via aspect ratio

1:1.5

1:1

Stacked vias are blind vias layered on top of each other. They connect three or more layers electrically, e.g. laser holes from layer 1 to layer 3 but with connection of layer 2.

 

Parameter

Standard

High standard

Laser drill diameter: Layer 1-2

125 µm

110 µm

Laser drill diameter: Layer 2-3

200 µm

125 µm

Landing pad drill diameter: Layers 1 & 3

330 µm 250 µm

Landing pad drill diameter: Layer 2

425 µm 375 µm

Laser via aspect ratio

1:1.5

1:1

Staggered vias are stepped laser vias that electrically connect three or more layers.

Parameter

Standard

High standard

Min. laser drill diameter

125 µm

110 µm

Landing pad diameter

330 µm

250 µm

Laser via aspect ratio

1:1.5

1:1

A skipped via is a connection over at least two lay-up layers that directly connects the outer layer with an inner layer electrically without connecting the intermediate layer. Example: Laser hole from layer 1 to layer 3 without connecting layer 2.

Parameter

Standard

High standard

Min. laser drill diameter

200 µm

125 µm

Landing pad diameter

330 µm

250 µm

Laser via aspect ratio

1:1.5

1:1

A buried via is an inner layer plated through holes that does not connect the outer layers. Buried vias can be filled with resin from the surrounding prepregs. Alternatively, the holes can be plugged and, if required, plated over.

Parameter

Standard

High standard

Drill diameter

200 µm - 450 µm

<200 µm and >450 µm

Outer layer annular ring

150 µm

100 µm

Inner layer annular ring

200 µm

150 µm

Aspect ratio

1:6

1:8

Contact info

Rainer Jäckle