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Electric/Electronic Property Evaluation Technology

For reliable evaluation of mobile phones, etc., using high frequencies in the GHz range.

As electronic devices, such as mobile phones, use frequencies in the GHz range, there are calls for materials that have no effect on signal transmission. This is especially true with respect to the flexible printed circuit boards (FPCs), etc., used as circuit materials to transmit signals. Precisely measuring and evaluating high frequency characteristics (dielectric loss tangent, relative dielectric constant and characteristic impedance) is extremely important as even the slightest change has the potential to affect signal transmission.

A typical flexible printed circuit board.

A typical flexible printed circuit board

A circuit integrated suspension (CIS).

A circuit integrated suspension (CIS)

Meeting the strict demands for precision evaluation of electrical characteristics.

As electronic parts become smaller and smaller, demands regarding the electrical characteristics of process materials are becoming more strict, with calls for the precision evaluation of space charge and surface potential, etc. An example of the application of this technology is in the evaluation of the electrical characteristics of the semi-conductive polyimide film used in color photocopiers, etc., where precision control of electrical characteristics is required.

Polyimide belts.

Polyimide seamless belts

Cover tape for electrical components.

Cover tape for electrical components

Evaluation of Characteristic Impedance

This technology helps to prevent signal reflection, which can be a major problem in circuit boards.

In circuit boards used in high frequency applications, signal reflection, crosstalk and noise, etc., can be major problems. In order to prevent signal reflection, it is necessary to design the characteristic impedance of transmission circuits to be the same as the specification impedance of connected devices. Characteristic impedance is measured using Time Domain Reflectometry (TDR).

TDR overview
TDR overview

With TDR, step pulse voltage is input into the transmission circuit and the voltage reflected in the transmission circuit is measured over time. The characteristic impedance of the circuit board is then calculated from the voltage drop in the reflected voltage. By seeking the effective dielectric constant in the circuit board it is also possible to compare relative locations in the transmission circuit.

TDR overview

Evaluation of Transmission Characteristics

Using S parameters that can be measured in the MHz to GHz band it is possible to determine transmittable signal frequencies.

Scattering parameters (S Parameters) are an important factor to be measured in circuit boards. S parameters are elements that determine circuit characteristics according to the size and phase of incoming and outgoing transmission circuit voltage and can be measured in the MHz to GHz range using a vector network analyzer. Transmittivity (Transmissivity) characteristic |S21| shows output power, which can be used to evaluate the degree of transmission loss, etc., while reflection characteristic |S11| shows reflected power, which can be used to evaluate the size and influence of reflected waves. By measuring such S parameters it is possible to determine transmittable signal frequencies and evaluate changes in transmission loss.

Measuring overview
Measuring overview

A vector network analyzer consists of a sine wave generator and directional couplers and uses a minimum of two ports to evaluate incoming voltage at various frequencies and measure the items shown below.
(1) Reflected voltage and transmitted voltage at the time of input from port 1.
(2) Reflected voltage and transmitted voltage at the time of input from port 2.

S parameters that can be evaluated
S parameters that can be evaluated.

Space Charge Evaluation

Observing the dispersion, transfer and accumulation of space charge within films in real-time.

Using our proprietary space charge evaluation technology it is possible to observe the dispersion, transfer and accumulation of space charge (ion carriers) within polymer film in real-time.

Space charge observation overview
Space charge observation overview

When space charge exists within a sample, when a pulsed electric field is applied to the space charge, the coulomb force generates an elastic wave. This is converted to voltage by the piezoelectric element on the back of the electrode and the resulting charge density is measured.

An example of adhesive tape space charge measurement
An example of adhesive tape space charge measurement.

From these real-time measurement results it is clear that a charge slowly accumulated on the boundary between the PET film and the adhesive. Furthermore, we can see that there is a tendency for the dielectric charge that accumulates on the surface of both electrodes to cause a drop on the negative electrode and that after the voltage was removed, the charge that had accumulated slowly dissipated.

　

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