JPH04276540A - Thin-film impact tester - Google Patents

Abstract

PURPOSE:To make it possible to perform measurement quantitatively and precisely. CONSTITUTION:A hard ball which is made to hit a test piece 1 is made to be a small ball 4. A compressed-air cylinder 2 is an acceleration source which can destruct a thin film formed on the test piece with the small ball. Speed sensors 6 and 7 and a high-speed camera 8 for measuring the speed of the small ball 4 at the time of impact and the flying direction are provided. The elastic vibration wave and exo-electrons which are generated from the destructed part when the small ball 4 hits the test piece and the change in electric resistance between the thin film and the ground are collected. The data are analyzed, and the impact strength of the thin film is measured.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film impact tester for testing the impact strength of thin films such as protective films and wear-resistant coatings.

0002

BACKGROUND OF THE INVENTION In general, impact testing machines for bulk test pieces include a Charpy impact testing machine and an Izod impact testing machine. For example, a Charpy impact tester carries out a test by lifting a hammer to a predetermined angle, allowing the hammer to fall freely, colliding the hammer with a test piece, and measuring the degree of fracture. The Izod impact tester also conducted tests based on the same measurement principle.

On the other hand, mechanical parts, especially mechanical parts with sliding surfaces, are now required to have abrasion resistance due to their functionality, and abrasion-resistant films have been applied to them. became. Naturally, this wear-resistant film is required to have impact resistance.

An example of a mechanical component coated with such a wear-resistant film is a magnetic disk. In recent years, there has been a demand for these magnetic disks to shorten access time and increase recording/playback speeds, and the rotational speed has also increased to 5,000 rpm, for example.
It is about pm. With such high speed rotation,
The circumferential speed of a 5-inch magnetic disk is actually 25 m.
/min speed. Moreover, the distance between the magnetic disk and the magnetic head is as small as only 0.1 to 0.2 μm.
While the magnetic disk and magnetic head are in operation, there is a very high possibility that an impact force due to contact will be applied to the magnetic disk. In order to protect magnetic disks from mechanical damage, silicon dioxide films and carbon films have recently been applied to magnetic disks, and these protective films are now required to have high impact resistance.

However, a Charpy impact tester or an Izod impact tester cannot be used to test the impact strength of such a protective film. Therefore, for the impact test of the thin film, a simple device was prototyped using, for example, a steel ball drop test device used for the impact test of plate glass. This simple impact test device allows a steel ball to fall naturally and collide with the thin film of a test piece, and the degree of destruction is observed using a microscope to determine the impact strength.

[0006]

[Problems to be Solved by the Invention] However, in a simple impact testing device that uses natural falling, it is necessary to make the steel ball larger or to increase the falling height in order to obtain the impact energy. For this reason, when the steel ball is made larger, there is a drawback that a test piece of a size corresponding to the steel ball must be specially made, or that actual test values cannot be obtained. Also, if you want to make the steel ball smaller and increase the falling height,
Not only does it require a large amount of space, but it also has the drawback of causing the drop point to be incorrect. Furthermore, since the degree of destruction is determined by observing only the surface, the degree of peeling of the film cannot be detected and the actual impact strength cannot be precisely measured.

An object of the present invention is to provide a thin film impact tester that can quantitatively collect multifaceted fracture events and accurately measure impact strength, and that requires a smaller space to overcome these drawbacks. .

[0008]

[Means for Solving the Problems] The thin film impact tester of the present invention includes a small ball that collides with a thin film to be tested, an acceleration source that applies an accelerating force to the small ball, and when the small ball collides with the thin film. and a high-speed camera that detects the flying direction and speed of the small ball after the collision, and detects the elastic vibration waves generated by the destruction of the thin film caused by the collision of the small ball and It is characterized by testing impact strength by detecting exoelectrons and the electrical resistance of contact with the base of the thin film.

[0009]

[Operation] As mentioned above, compressed air or the explosive force of gunpowder can be used to apply a predetermined impact energy to the small ball. Further, the small ball may be made of a magnetic material, for example, an iron ball, and may be accelerated by magnetic force.

[0010] Collecting impact fracture event data involves collecting the elastic vibration waves generated by the deformation and fracture modes caused by the impact of the pellets. That is, by analyzing the collected elastic vibration waves, it is possible to determine the degree of deformation due to destruction and whether the deformation is elastic deformation or plastic deformation. Of course, the degree of destruction can also be observed using an optical microscope or an electron microscope after the test.

[0011] Another method of collecting destruction event data is to detect exoelectrons emitted by a new surface generated by surface deformation or destruction. The degree of deformation and destruction can be determined from the amount of exoelectrons emitted. That is, this is because these exoelectrons are not emitted during elastic deformation, but only during plastic deformation. This is because the amount released increases until it reaches destruction.

[0012] Furthermore, as another type of fracture event data, the electric resistance between the small ball and the test piece at the time of collision is determined. This is because if the base of the small ball and thin film is a conductor, the electrical resistance of the small ball/test piece upon impact will change depending on the state of destruction of the thin insulating film. The purpose is to focus on this phenomenon and detect deformation and destruction caused by the impact.

On the other hand, in order to precisely measure the impact energy applied to the thin film, it is necessary to measure the velocity of a small ball of known weight before impact. To do this, if you use a high-speed camera to photograph the small ball just before it collides, you can measure the flying direction and speed of the small ball. That is, it can be calculated from the relative velocity of the film feed speed and the velocity of the small ball, and the angle of impact with the surface of the test piece can also be photographed. Then, the impact energy can be quantitatively determined from the velocity of the small ball and the weight of the small ball.

As explained above, the thin film impact tester of the present invention has a means for measuring the impact energy when a small ball collides, and data on events that occur when a thin film is destroyed by this small ball impact. By providing a means for collecting impact strength quantitatively and accurately, it is possible to measure impact strength quantitatively and precisely.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a perspective view of a thin film impact tester showing an embodiment of the present invention. As shown in the figure, this thin film impact tester consists of a small ball 4 that collides with the thin film of a test piece 1, an acceleration tube 5 that regulates the flight direction of this small ball 4, and an acceleration force that applies an accelerating force to the small ball 4. A compressed air cylinder 2 and a valve 3, speed detection sensors 6 and 7 that detect the speed of the small ball colliding with the thin film of the test specimen 1, and a high speed sensor that more reliably measures the speed and flight direction of the small ball 4. Photographer 8 and A/E that detects elastic vibration waves generated by the destruction of the thin film caused by the collision of small balls.
It includes a sensor 9 and an exoelectron detection sensor 10 which is a solid sensor that detects exoelectrons.

Here, the test piece 1 was a magnetic disk. Generally, a magnetic disk consists of a substrate, a magnetic medium, a protective film, and a lubricant. CoN with a thickness of about 70 nm
An ip-plated magnetic medium is coated, and a protective film is sputtered with silicon dioxide having a thickness of 40 nm. and,
On this protective film, a lubricant is applied to a thickness of about 2 nm.

The small ball 4 is made of tungsten carbide and has a diameter of about 2 mm. The length of the acceleration tube 5 is 50 cm, and a compressed air cylinder is used so that the speed just before collision is 3 to 30 m. The pressure and volume were set to 2. The angle of the accelerating tube 5 can be varied from 10 degrees to 90 degrees. Furthermore, in order to measure the velocity of the small ball 4 immediately before the collision, two slits are provided on the end face side of the acceleration tube 5, and velocity sensors 6 and 7, which form a pair at the light emitting part and the light receiving part, are connected to the acceleration tube 5. attached to. These speed sensors 6 and 7 detect the time during which light is blocked when the small ball 4 crosses the slit.
, 7, calculate the final velocity of the small ball 4. Note that more accurate speed and flight direction measurements are made by analyzing images taken by the high-speed camera 8.

On the other hand, the exoelectron detection sensor 10 is a solid state sensor, and although it can be used in the atmosphere, it has higher sensitivity in a vacuum. Therefore, it is necessary to prepare a chamber surrounding the test piece and reduce the gap between the accelerator tube 5 and the small sphere 4 to reduce the amount of air leakage. In addition, in this case, if the explosive power of gunpowder is used as the source of acceleration of the small ball,
By changing the structure of the accelerating tube 5, the blast wave is instantaneous and can be released in the lateral direction of the accelerating tube. Furthermore, if magnetic force is to be used, the entire testing machine can be covered with a chamber and evacuated.

Further, in the thin film impact tester in another embodiment, although not shown in the drawings, in order to measure the electrical resistance at the time of collision, the small ball 4 is made of iron, and this steel ball has a diameter of 40 nm. Bonding aluminum wire of about
Changes in electrical resistance at the time of collision were detected.

[0021] Using such a thin film impact tester, we measured the impact strength of the protective film formed by changing the film formation conditions for the silicon dioxide film on the magnetic disk described above. It has been found that by increasing the pressure of a certain Ar gas, the speed at which plastic deformation and impact fracture begin decreases. That is, the impact strength of the protective film could be quantitatively and accurately measured using this thin film impact tester.

[0022]

Effects of the Invention As explained above, the present invention involves preparing a relatively small ball, an acceleration source that gives the ball an acceleration greater than that of a natural fall, and an elastic vibration generated by a thin film that is destroyed by the collision. By providing a means to collect waves, exoelectrons, changes in electrical resistance, etc., and analyzing these event data, it is possible to obtain a compact thin film impact tester that can quantitatively and precisely measure impact strength. be.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a thin film impact tester showing an embodiment of the present invention.

[Explanation of symbols]

1 Test piece 2 Compressed air cylinder 3 Valve 4 Small ball 5 Acceleration tube 6, 7 Speed sensor 8 High speed camera 9 A/E sensor 10 Exo electronic detection sensor

Claims (1)

[Claims] Claim 1: A small ball to be collided with a thin film to be tested, an acceleration source that applies an accelerating force to the small ball, a speed detector to detect the speed at which the small ball collides with the thin film, and a The device is equipped with a high-speed camera that detects the flight direction and speed of the small balls, and detects elastic vibration waves and exoelectrons generated by the destruction of the thin film caused by the collision of the small balls, as well as electrical contact resistance of the thin film with the base. A thin film impact tester that tests impact strength through detection.