JPH0658975A - Substrate test equipment - Google Patents

Abstract

PURPOSE:To obtain a conduction test equipment for substrate in which the substrate is protected against breakdown by utilizing electrooptic effect in place of a probe. CONSTITUTION:An equipment for testing conducting state of wiring 4 formed on a substrate 3 comprises a crystal 1 contacting with the substrate 3 and exhibiting both electrooptic effect and optical conductivity, and a transparent electrode 2 applied on the surface of the crystal 1 oppositely to the substrate 3. The test equipment further comprises a power supply 5 connected with the transparent electrode 2 and applying a voltage thereon, a writing light beam irradiating section for irradiating the wiring 4 to be measured with a light beam having such wavelength as exhibiting optical conductivity through the crystal 1, and an electrooptical image measuring section for irradiating the crystal 1 with a reading light having such wavelength as exhibiting electrooptic effect and observing an optical image feflected on the crystal 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a board testing device, and more particularly to a device for testing whether a wiring pattern on a board is connected as designed.

For example, since a semiconductor chip is used in a multi-chip module (MCM) and wiring is formed by a plurality of layers, it is necessary to conduct a continuity test (open / short) of a wiring pattern before mounting the chip.

[0003]

2. Description of the Related Art In order to test the continuity of wiring formed on a substrate, it is necessary to apply and measure a voltage at both ends of the wiring. In the conventional technique, a large number of probes are aligned and pressed against the substrate, wiring is selected by switching switches, and voltage is applied and measured.

On the other hand, in the field of optics, a voltage measurement technique utilizing the electro-optic effect of crystals is well known and has been applied to the measurement of high speed signals in recent years. For example, the present inventor has provided a method of measuring a signal waveform by bringing a detection electro-optic crystal close to a wiring portion of a mounting printed circuit board. If this detection method can be extended to conduct a continuity test of the substrate, it can replace the above-mentioned measurement by the probe.

[0005]

[Problems to be Solved by the Invention] In the conventional test method,
There is a problem that the substrate may be destroyed by the stylus pressure or the wiring end may be damaged by the stylus.

It is an object of the present invention to provide a continuity test device which utilizes the electro-optic effect without using a probe and which does not damage the substrate.

[0007]

[Means for Solving the Problems] A solution to the above problems is to provide an apparatus for testing the continuity of wiring formed on a substrate.
A crystal having both electro-optical effect and photoconductivity to be brought into contact with the substrate, a transparent electrode deposited on the surface of the crystal opposite to the substrate, and a voltage connected to the transparent electrode A power source to be applied, a writing light beam irradiation unit for irradiating the wiring to be measured with light having a wavelength exhibiting photoconductivity through the crystal, and read light having a wavelength exhibiting an electro-optical effect is irradiated to the crystal, And an electro-optical image measuring unit for observing the reflected light image of the substrate test apparatus.

[0008]

According to the present invention, in order to realize a substrate test without using a probe, voltage application by light and wiring voltage detection (specifically, reading of wiring voltage by electro-optical effect and application of voltage by photoconductivity). ).

FIGS. 1A and 1B are explanatory views of the principle of the present invention. A crystal 1 having an electro-optical effect and photoconductivity is placed on a substrate 3 to be tested, and light (writing light) having a wavelength λ ₁ (short wavelength) at which the crystal exhibits photoconductivity and a wavelength λ exhibiting an electro-optical effect.
_Two lights (reading light) of ₂ (long wavelength) are irradiated to the crystal [see FIG. 1 (B)]. Wiring pattern 4 of electro-optic crystal 1
A transparent electrode 2 is deposited on the surface opposite to the above, and a power source 5 is connected thereto to apply a voltage.

By irradiating the wiring pattern 4 to be measured with the writing light beam based on the design data,
A voltage is applied to this wiring pattern by utilizing photoconductivity. On the other hand, by irradiating the crystal with the reading light, the conduction of the wiring connected to the writing light irradiation pattern can be known by measuring the voltage distribution on the substrate by utilizing the electro-optical effect.

According to this method, the load applied to the substrate is only the crystal load, and the substrate is not destroyed.

[0012]

FIG. 2 is a sectional view for explaining an embodiment of the present invention. In the figure, the measuring unit is composed of a substrate mounting table 6, a crystal unit covering the entire surface of the substrate, a writing light beam irradiation unit capable of scanning the entire surface of the substrate, and an electro-optical image measuring unit capable of observing the entire surface of the substrate.

For the crystal 1, for example, GaAs covering the entire surface of the substrate is used. As a transparent electrode on the surface of this crystal opposite to the substrate
An ITO (InSnO) electrode 2 is deposited, and a voltage is applied to it from a power source 5.

The boundary between the wavelength region where the GaAs crystal exhibits photoconductivity and the wavelength region where the GaAs crystal exhibits the electro-optic effect is near 850 nm.
A He-Ne laser is used as the writing light source 7 of the writing light beam irradiation unit.
(Wavelength 633 nm) is used. The writing light beam can be applied to an arbitrary point on the crystal by a lens 9 and a scanner (for example, a galvano scanner) 8.

The reading light source 10 of the electro-optical image measuring unit may be an infrared lamp filtered or InGaA.
An sP semiconductor laser (wavelength 1.3 μm, 1.5 μm) is used. The light from the light source is made into, for example, a circularly polarized state by the polarizer and the phase shifter 11, and the reading light is applied to the entire surface of the substrate by the lens 9.

Here, when a voltage is applied to the wiring, an electric field is induced in the crystal and the polarization state of the light reflected back and forth in the crystal changes. By observing the reflected light image from the crystal with the CCD camera 13 through the analyzer 12, the change in the polarization state of the read light due to the wiring voltage is observed as the voltage distribution on the substrate.

In this embodiment, a method of collectively observing a two-dimensional image of reflected light is shown. However, even if the read light is made into a beam and scanned on the crystal, and the reflected light is measured by a photodiode or the like. Good.

FIG. 3 is a block diagram of the apparatus of the embodiment, and FIG. 4 is a diagram showing the operation flow of the embodiment. The operation of the embodiment will be described below with reference to FIGS.

The substrate to be tested is mounted on the substrate mounting base 6,
The substrate is brought into contact with the crystal according to the instruction of the control unit 14 (Figs. 4 and 41). Next, the coordinates of the writing light are calibrated while observing the image (Figs. 4, 42). Based on the design data, the control unit irradiates the coordinates of the edge of the wiring pattern to be measured with writing light (Figs. 4, 43). Since the photoconductivity causes conductivity between the transparent electrode 2 and the wiring pattern, a voltage is applied to the wiring pattern irradiated with the writing light.

Next, when the irradiation of the writing light beam is stopped and then the voltage application to the transparent electrode is stopped, the wiring pattern connected to the wiring irradiated with the writing light beam remains charged. At this time, the voltage distribution image acquired by the electro-optical image measurement unit (image processing unit 15) is imported into the control unit (Fig. 4, 44) and compared with the design data (Fig. 4, 45) to determine the writing light. A wiring pattern that is electrically connected to the irradiated wiring pattern is extracted. If the wiring is broken, the voltage is not detected in the pattern as designed, and if the voltage is detected in the pattern not as designed, there is a short circuit (Fig. 4, 46).

The continuity test for the wiring extending in the direction penetrating the substrate can be conducted by applying a voltage to the substrate mounting table and measuring the voltage distribution image by the electro-optical image measuring section.

[0022]

According to the present invention, the continuity test of the substrate can be performed without using the probe, and the test can be performed without breaking the substrate or the wiring.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is a sectional view illustrating an embodiment of the present invention.

FIG. 3 is a block diagram of the apparatus of the embodiment.

FIG. 4 is a diagram showing an operation flow of the embodiment.

[Explanation of symbols]

 1 Crystal with electro-optic effect and photoconductivity 2 ITO electrode with transparent electrode 3 Substrate under test 4 Wiring pattern 5 Power supply 6 Board mounting stand 7 Writing light source 8 Scanner 9 Lens 10 Reading light source 11 Polarizer and retarder 12 Analyzer 13 CCD camera

Claims (1)

[Claims] 1. A device for testing a conduction state of wiring formed on a substrate, comprising: a crystal having both electro-optical effect and photoconductivity, which is brought into contact with the substrate; and the substrate of the crystal. Irradiation of a transparent electrode adhered to the opposite surface, a power source connected to the transparent electrode to apply a voltage, and a writing light beam for irradiating the wiring to be measured with light having a wavelength exhibiting photoconductivity through the crystal. And an electro-optical image measuring unit for irradiating the crystal with a reading light having a wavelength exhibiting an electro-optical effect and observing a reflected light image from the crystal.