JPH0781976B2 - Sample discrimination method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample discriminating method, and more particularly to a method for discriminating a semiconductor portion and an insulator portion in a ceramic containing a semiconductor and an insulator by a simple method.

2. Description of the Related Art Conventionally, thermal etching or chemical etching has been the mainstream for etching ceramics, and grain boundaries and portions having compositional differences are discriminated by heat treatment or nitric acid treatment. However, the etching method for discriminating between the semiconductor and the insulator is not suitable for the conventional method.

Problems to be Solved by the Invention In an electronic component to which a semiconductor ceramic is applied, it is necessary to observe and measure a shape because an insulator and a semiconductor are present in a minute portion adjacent to each other and their shapes determine electric characteristics. Is. However, in general, semiconductor ceramics often have almost the same composition as the adjacent insulator portion, and until the present time, there was no appropriate sample processing method, and it could not be distinguished.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention etches only a semiconductor portion by immersing a ceramic containing both a semiconductor and an insulator in an electrolytic solution and applying a voltage to the surface, This makes it possible to easily distinguish the insulating portion and the semiconductor portion during observation.

Effect According to the present invention, the surface of the conductive portion is electropolished and the shape is roughened (etched) by selectively flowing a current in the ceramic semiconductor portion to which a voltage is applied in the electrolytic solution. As a result, even if the semiconductor and the insulator are intricately intricate, only the semiconductor part will be etched and the optical reflection will change or irregularities will be created, which will be easy by visual observation, optical microscope observation and electron microscope observation. You will be able to determine.

Example As an example of the present invention, a method for discriminating a sample of a barium titanate ceramic disc in a surface layer type semiconductor ceramic capacitor will be described below with reference to the accompanying drawings.

FIG. 2 shows a schematic diagram of the structure of the surface layer type semiconductor ceramic capacitor. A silver electrode 2 and a lead wire 3 are attached to both sides of a barium titanate ceramic disk 1 to form a capacitor. The ceramic disc 1 is divided into a semiconductor portion 4 inside and an insulator portion 5 on the surface layer, but the boundary between them is indistinguishable. The lead wire 3 and the electrode 2 are removed from this capacitor, one end of the ceramic disk is shaved off to expose a cross section 6 as shown in FIG. 3, the internal semiconductor portion 4 is exposed, and the electrode 7 and the lead wire are newly added there. Attach 8. This is embedded in a resin 9 as shown in FIGS. 4 to 5, the portion to which the lead wire 8 is attached and the portion on the opposite side are scraped off, and polished until completely smooth. Ceramic cross section as well as the entire polished surface 10
11 is exposed and is actually divided into an internal semiconductor portion and a surface insulator portion, but no difference is seen on the polished surface.

This sample, as shown in FIG.
A DC power supply 17 is placed between the cathode 15 and the sample 15 as an anode, and a voltage is applied to perform electrolytic etching. As a result, the surface of the semiconductor portion 4 of the ceramic cross section 11 is etched, and the surface insulating material portion 5 remains as a polished surface, so that optical reflection and unevenness are different, and can be easily discriminated. Observing the optical micrographs of the polished surface before and after etching, the ceramic polished surface in the embedding resin shows that after electrolytic etching,
Since the internal semiconductor portion 4 is observed black and the surface insulator portion 5 is observed white on the polished surface, the shape and thickness can be clearly observed.

Further, also for the grain boundary layer type semiconductor ceramic capacitor, the same treatment can be performed by extremely thinning the sample and performing electrolytic etching.

EFFECTS OF THE INVENTION According to the present invention, the treatments according to the present invention, which can be easily discriminated by subjecting ceramics having substantially the same chemical composition and the same structure but different in conductivity only to the surface treatment according to the basic electrochemistry The method is simple, requires no special equipment, and has a high resolution that can withstand observation with an electron microscope, which is extremely useful.

[Brief description of drawings]

FIG. 1 is a diagram showing a pattern of electrolytically etching a sample, and FIG.
FIG. 4 is a partially cutaway perspective view of a surface layer type semiconductor ceramic capacitor, FIG. 3 is a perspective view showing a state where the capacitor is processed into a sample, and FIG. 4 is a perspective view showing a resin-embedded state of the sample, FIG. Is a bottom view of the same. 4 …… Internal semiconductor part, 5 …… Surface layer insulator part, 14 ……
Electrolyte, 15 …… sample, 16 …… cathode, 17 …… power supply.

Claims (1)

[Claims] 1. A ceramic containing a semiconductor and an insulator is dipped in an electrolytic solution, and a voltage is applied to electrolytically etch only the semiconductor portion. Depending on the etching degree, the semiconductor portion and the insulator portion in the ceramic are separated. A method for discriminating a sample, which comprises discriminating.