High frequency printed circuit boards are technologically unique models of dielectrics with operating frequencies from several MHz to tens of GHz.

Feature: they are used for high frequency equipment, even when the use of traditional FR4 glass cloth materials is impossible.

— Communication device in space atmospheric instruments
— Specialized high frequency equipment
— Special military devices
— Planar antenna equipment

— Analog high frequency

They work in the range of GHz. They are not susceptible to signal line irregularities. There is no signal energy loss in the dielectric plate.

— Digital high speed

They are designed to work in the range from tens to hundreds of MHz. They have high rates of transmission lines coordination. Often, they have a multilayer structure.

— Dielectric permeability: 2.2–10.2 GHz.
— Signal delay characteristics.
— Thickness criteria: 0.2–8 mm.
— Type of foil material.
— Tangents of dielectric loss angles: 0.0009-0.004.

When creating high frequency printed circuit boards, manufacturers use special laminates with a low dielectric permeability (<3 F). They have a stable, wide frequency range and insignificant dielectric loss indexes. Such materials are produced by Neltech, Taconic and Rogers and others.

Let us list the most popular microwave laminates:

— Reinforced PTFE type — ULTRALAM 2000.
— Ceramic — RT/duroid 6000.
— Thermostable, produced on the basis of hydrocarbon ceramics — TMM.
— Made on a combined basis (ceramics and PTFE) — Ro3200, and Ro3000 as well.
— Reinforced ceramic models with thermosetting polymer — Ro4000.

High frequency printed circuit boards are made based on fluoroplastics by several methods: a positive combined and tenting method. Note that the main significant difference between these methods is a stage of applying metal resist on a copper surface (a combined positive method).

In turn, the manufacture of high frequency printed circuit boards by tenting method greatly simplifies the production process, reducing time and money.

The main feature: when producing multilayer high frequency dielectrics, the laminates are used only as outer layers, and inner ones are filled with standard epoxy glass cloth materials.

Thickness mm

0,5−2

0,2−8

Maximum typical size, mm

300×400

800×1100

Number of layers

2-8

до 32

Tolerances:

– thickness %

±10

— sizes of plates, mm

± 0,1

— hole diameters (metallized), mm

± 0,1

± 0,076

— hole diameters (non-metallized), mm

± 0,1

± 0,058

— hole diameters for pressing in, mm

± 0,051

— conductor width,%

± 30

± 25

The ratio of boards thickness to the diameter of metallized holes

8:1

10:1

Minimum values:

— gap width/conductors, mm

0,15

0,1

— copper holes borders, mm

0,15

0,125

— through holes diameters, mm

0,3

0,2

— distance "conductors — masks opening", mm

0,1

0,075

— openings "masks — area", mm

0,075

0,5

— height of silkscreen text, mm

1,5

1,25

Width of silkscreen printing lines, mm

0,2

0,15

Liquid solder mask colour

Green, red, blue, yellow, white and black

Marking paint colour

Yellow, black, white