One HDI printed circuit board (High Density Interconnect) is a multilayer printed circuit board with at least four layers, which are interconnected in the Sequential Build Up (SBU) process is built up in several press cycles. Characteristic features are conductor track widths and spacing (line/space) from 75 µm and the use of Microvias (laser drilled), Buried Vias (buried boreholes) and Stacked or Staggered via structures. HDI technology enables higher packing densities than conventional multilayer PCBs and is the standard technology for miniaturized electronic assemblies with high pin density.
The KSG GmbH produces HDI printed circuit boards at two of its own production sites in Europe: in Gornsdorf (Germany) and Gars am Kamp (Austria). As one of the largest PCB manufacturers in Europe, KSG produces according to the quality standards IPC Class 2 & 3, ISO 9001, IATF 16949 and ISO 13485 and is therefore qualified for demanding industries such as automotive, medical technology and aerospace.
In the Sequential Build Up (SBU) process several multilayer cores are pressed together sequentially. Each pressing cycle adds new copper layers, which are electrically connected using various drilling processes. For structures with a high number of layers, the use of Base material with optimized Z-axis expansion (e.g. with low CTE) is recommended to minimize reliability problems due to thermal expansion.
| Parameters | Specification | Note |
|---|---|---|
|
Number of layers |
4 - 30 |
Can be designed as HDI-SBU from 4 layers upwards |
|
PCB thickness |
0.5 - 3.20 mm |
— |
|
Line / Space |
from 75 µm / 75 µm |
With modern direct laser exposure |
|
Materials |
FR4, high frequency materials |
Optimized CTE for HDI superstructures |
|
Glass transition temperature (Tg) |
135 / 150 / 170 / 180 °C |
Depending on material |
|
Aspect ratio through hole |
≤ 1:10 |
— |
|
Aspect ratio Laservia |
≤ 1,1:1 |
— |
|
Via filling technologies |
Filled and capped Type VII, Microvia-Copper-Filling |
Decisive for stacked microvias |
|
Surfaces |
ENIG, Chem. tin, ENEPIG, OSP, Galv. Ni/Au |
More on request |
|
Solder mask |
Green, red, blue, black (glossy/matt), white, yellow |
— |
HDI printed circuit boards are the right technology choice wherever High integration density, Small size and Signal integrity are required at the same time:
HDI printed circuit boards are the right technology choice wherever High integration density, Small size and Signal integrity are required at the same time:
| Criterion | HDI / SBU | Standard multilayer |
|---|---|---|
|
BGA / µBGA components (< 0.8 mm pitch) |
✓ Optimal |
✗ Limited |
|
Lack of space / miniaturization |
✓ Optimal |
✗ Limited |
|
Signal integrity for high-speed signals |
✓ Very good |
~ Conditional |
|
EMC-critical application |
✓ Recommended |
~ Restricted |
|
Standard application, non-critical density |
~ Possible |
✓ More cost-effective |
|
Production costs |
Higher (SBU process) |
Lower |
Standard multilayer PCBs are manufactured in a single press cycle and use only mechanically drilled vias. HDI PCBs are built up in several press cycles using the Sequential Build Up (SBU) process and also use laser-drilled microvias and buried vias. This enables finer track structures (from 75 µm), higher packing densities and the processing of components with very high pin densities such as BGAs with pitches of less than 0.8 mm.
HDI is recommended as soon as: (1) components with high pin density (BGA, µBGA, QFN under 0.5 mm pitch) have to be installed, (2) the installation space is very limited and the number of layers is to be minimized, (3) high-speed signals place high demands on signal integrity or (4) single-sided assembly with high density is desired. Standard multilayers are more economical for non-critical standard applications without miniaturization pressure.
Standard HDI structures use FR4 base material with an increased glass transition temperature (Tg 150-180 °C). For high numbers of layers, material with a low CTE in the Z direction is recommended. Special HF materials (e.g. PTFE-based) are available for high-frequency applications in combination with HDI.
Yes, KSG produces samples and express boards in identical series quality with the same materials, the same processes and the same test methods as in series production. Samples can be requested directly from the Technical Support expert team.
Microvias (lasered) on outer layers
Microvias (lasered) in combination with plated-through laminates (mechanically drilled)
Microvias (lasered) in combination with buried vias (mechanically drilled)
Staggered microvias (lasered) in combination with buried vias (mechanically drilled) - from L2 to Ln-1
Staggered microvias (lasered) in combination with buried vias (mechanically drilled) - from L3 to Ln-2
Stacked microvias (lasered) with microvia copper filling in combination with buried vias (mechanically drilled)
Double Core
"Talk to us in the early stages of development. Together we will find the solution that will make your product even better."
The Technical support from KSG accompanies your HDI printed circuit board from the initial design idea through to series production. The range of services includes: PCB design and layout check, impedance calculation, layer stack-up calculation, current carrying capacity analysis, thermal analysis as well as long-term and ageing tests.
About the Digital Design Compass all design rules, assembly variants and design-to-cost notes for all KSG technologies are available digitally around the clock - free of charge for registered users.
Tell us about your requirements. Our team of experts will get back to you within one working day.
Talk to us in the early development phases of your project and contact our team of experts. Together we will find the solution that will make your product even better.
From design and layout checks to various calculations and thermal analyses - the experienced, competent Technical Support team will be happy to help you.