This application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2020-026370, filed Feb. 19, 2020, which is incorporated by reference.

TECHNICAL FIELD

The present invention relates to a housing case for crystal oscillators each being adapted for use in monitoring a film thickness of a thin film to be formed on a surface of each of the crystal oscillators, the monitoring being carried out by measuring the resonance frequency during the film formation in a vacuum atmosphere. This invention relates in particular to an arrangement in which the crystal oscillators can be easily set in position (transferred) into a holder of a sensor head of a crystal oscillator type of film thickness monitor.

BACKGROUND ART

At the time of forming a predetermined thin film on a substrate as an object for forming a film thereon, e.g., by vacuum deposition method, a crystal oscillator type of film thickness monitor is generally used for monitoring the film thickness of a vapor deposition material that has been adhered to the substrate. This kind of crystal oscillator type of film thickness monitor is known in, e.g., patent document 1 (Japanese Patent Gazette P3953505). The film thickness monitor in question has a sensor head. The sensor head is provided with: a sensor head main body having a driving means such as a stepping motor (vacuum pulse motor) and the like; and a holder in which a plurality of crystal oscillators are disposed on an imaginary circle at a distance from one another so as to be driven for rotation by a driving means. Provided that the direction from the sensor head main body to the holder is defined to be upper, on an upper surface of the holder having disposed each of the crystal oscillators, there is disposed a mask body in a manner to cover the holder. At a predetermined position of the mask body there is opened a film-forming window which faces the main surface (the surface to which the deposited material gets adhered) of a single crystal oscillator.

At the time of film forming processing in the vacuum atmosphere, the thickness of a thin film to be formed on the main surface of the crystal oscillator is monitored through the film-forming window by measuring the resonance frequency of the crystal oscillator. Then, for example, when the measured resonance frequency varies beyond a predetermined range as a consequence of an increase in the thickness of the thin film to be formed, the crystal oscillator in use is judged to be the end of lifetime. When the crystal oscillator in use as a monitor has reached the end of the lifetime, the holder is rotated by the stepping motor to the phase in which the next crystal oscillator and the film-forming window come into vertical agreement with each other. When all of the crystal oscillators that are disposed in the holder of the sensor head have reached the end of the lifetime by repeating the above-mentioned operations, the film-forming operations are suspended, and an operator in charge removes the holder, in the atmospheric conditions, off from the sensor head main body so that each of the crystal oscillators is replaced. The crystal oscillators of this kind will ordinarily be carried in a state of being housed in a specialized housing case.

Such a housing case for a plurality of crystal oscillators as is arranged to be capable of holding a plurality of crystal oscillators is known, e.g., in patent document 2 (U.S. Pat. No. 6,991,110). This housing case has: a case main body (tray portion) in cylindrical shape; and a cap body (cover portion) which is rotatably mounted on the case main body from an upper side thereof. On an upper periphery of the case main body there are formed in a recessed manner a plurality of supporting slots (housing or containing parts) at a circumferentially predetermined distance from one another. Then, crystal oscillators each having a circular profile are housed into each of the supporting slots from an upper side in a vertical posture in which the main surface of the crystal oscillator is at right angles to the vertical direction. In this manner, the crystal oscillators are arranged to be supported only by the respective outer peripheries.

The cap body is provided with a slot opening which is vertically in alignment (i.e., in alignment in the vertical direction) with any one of the supporting slots. It is thus so arranged that a single crystal oscillator that is housed in one of the supporting slots can be picked up (or removed) by using a pickup tool such as a pair of tweezers and the like. In the above-mentioned known art, however, when the operator tries to pick up a crystal oscillator from the supporting slot by using the pickup tool, it is necessary to pinch with the pickup tool both the front surface and the rear surface, inclusive of the main surface, of the crystal oscillator. There is thus a problem in that the surfaces of the crystal oscillator are likely to be damaged by the pickup tool. In addition, in case a plurality (e.g., 12 pieces) of crystal oscillators are set in position into the holder, each of the crystal oscillators must be set one piece at a time, while picking up each of the crystal oscillators from respective supporting slots, thereby taking much time and effort.

PRIOR ART DOCUMENTS

Patent Documents

Patent Document 1: Japanese Patent Gazette P3953505Patent Document 2: U.S. Pat. No. 6,991,110

SUMMARY OF THE INVENTION

Problems that the Invention is to Solve

In view of the above points, this invention has a problem of providing such a housing case for a crystal oscillator as is capable of suppressing to the best extent possible damages to the main surface of the crystal oscillator when it is picked up (taken out) by using a pickup tool, and as is also capable of improving the workability even at the time of setting in position a plurality of crystal oscillators into the housing case for a crystal oscillator.

Means for Solving the Problems

In order to solve the above problems, this invention is a housing case for a crystal oscillator, the crystal oscillator being adapted for use in monitoring a film thickness of a thin film to be formed on a surface of the crystal oscillator, the monitoring being performed by measuring a resonance frequency during film formation in a vacuum atmosphere. The housing case of this invention comprises: a case main body having disposed on an upper surface thereof a plurality of first recessed parts each being capable of housing therein a crystal oscillator in a horizontal posture with a main surface of the crystal oscillator facing in an up-and-down direction, the first recessed parts being disposed on a first imaginary circle at a distance from one another; a first cap body detachably mounted on the case main body from an upper side thereof; and an engaging means for engaging the first cap body relative to the case main body, wherein the engaging means is so constructed and arranged that, in a state in which the first cap body is engaged with the case main body, the engaging means restrains the crystal oscillators housed in the first recessed parts from jumping out of position.

According to this invention, each of the crystal oscillators is housed in a horizontal posture in each of the first recessed parts disposed on an upper surface of the case main body. Therefore, in case the operator in charge removes the first cap body in order to pick up a single crystal oscillator that is housed in the first recessed part, the outer periphery of the crystal oscillator can be pinched with a pickup tool such as a pair of tweezers and the like. In this manner, the main surface of the crystal oscillator can be suppressed, to the best extent possible, from getting damaged. In addition, at the time of carrying or transporting the crystal oscillators, the first cap body is engaged with the case main body by the engaging means. In this state, jumping out of the crystal oscillators can be restrained, e.g., by such a surface of the first cap body as lies opposite to the upper surface of the case main body in which a plurality of first recessed parts are formed. As a result, there will occur no disadvantage in that the crystal oscillators get damaged due to the vibrations and the like at the time of carrying them. By the way, in this invention, the description of “the crystal oscillators are housed in a horizontal posture” includes not only the case in which the crystal oscillators are, in the strict sense, in parallel with the horizontal surface when the case main body is installed on the horizontal surface, but also the case in which the crystal oscillators are housed in a state of inclination relative to the horizontal surface.

In this invention, the housing case for a crystal oscillator preferably comprises second recessed parts smaller in area than that of the first recessed parts, the second recessed parts being disposed around, and in continuation to, the first recessed parts. According to this arrangement, at the time when the operator tries to pinch the outer periphery of the crystal oscillators with a pickup tool such as a set of tweezers and the like, the second recessed parts serve the purpose of receiving the front end portion of the pickup tool without the contact of the pickup tool with the crystal oscillators. It is thus possible to further restrain damaging to the main surface of the crystal oscillators. By the way, each of the second recessed parts can be provided in two pieces symmetrically around the first recessed part. Alternatively, it may, for example, be so arranged that a single second recessed part may uniformly be provided on the diametrically inside or the outside of each of the first recessed parts. In this case, in order to downsize the housing case, preferably, each of the second recessed parts shall be provided only on the diametrically inside of each of the first recessed parts. On the other hand, for example, the second recessed parts may be positioned on the first imaginary circle. At this time, it may be so arranged that the adjacent first recessed part and the second recessed part are brought into communication with each other (in other words, by means of an annular groove by which the first recessed groove and the second recessed groove are circumferentially in communication with each other). Otherwise, the diameter of the first recessed part may be dimensioned to be able to accept the front end portion of the pickup tool and, by cutting away outer periphery as described hereinafter, the second recessed part may be formed.

Further, in this invention, an arrangement may be employed such that a supporting piece may be formed in each of the first recessed parts, the supporting piece being adapted to support such a crystal oscillator at an outer periphery thereof as has been dropped into the first recessed part from an upper side. According to this arrangement, the main surface and the rear surface of the crystal oscillator can advantageously be suppressed from getting damaged by the vibrations and the like at the time of carrying the crystal oscillator. In this case, an arrangement may be made such that the horizontal movement of the crystal oscillator that has been dropped from the upper side into the first recessed part can be restrained by the supporting piece. On the other hand, an arrangement may be made that, when the supporting piece supports the outer periphery of a crystal oscillator that has been dropped from an upper part into the first recessed part, the horizontal movement of the crystal oscillator is restrained by an inner surface of the first recessed part (or by another element formed on the inner surface thereof).

In addition, in this invention, the housing case for the crystal oscillator may comprise: a second cap body that can be detachably inserted, from an upside, into the case main body prior to insertion of the first cap body into the case main body. The second cap body has formed, in such a surface thereof as lies opposite to an upper surface of the case main body, a pickup opening that faces any one of the first recessed parts so as to enable to pick up a crystal oscillator housed in the first recessed part. According to this arrangement, when a single crystal oscillator that has been housed in the first recessed part is picked up, there can be maintained a state in which each of the other crystal oscillators housed in other first recessed parts is restrained from jumping out of position. Therefore, at the time when the operator picks up a single crystal oscillator, there can be avoided a disadvantage in that other crystal oscillators are damaged by mistake.

Further, the housing case preferably further comprises a holder of a sensor head for monitoring a film thickness of a crystal oscillator, the holder being provided with installation recessed parts in which a plurality of crystal oscillators are installed on a second imaginary circle with a center thereof being the center of rotation, at a distance from one another, the holder being arranged to set in position unused crystal oscillators. Provided that the holder has formed, on a surface of installing crystal oscillators, a boss part having an axial line passing through the center of rotation, the first cap body has: on an upper surface thereof a fitting recessed part in which the boss part gets fitted so as to coaxially coincide the first imaginary circle and the second imaginary circle; and a phase determining means for determining the phase of the first cap part relative to the holder such that the first recessed part and the installation recessed part vertically coincide with each other.

According to the above-mentioned arrangement, when all of the crystal oscillators placed in the sensor head have reached the end of the lifetime, the operator takes out the holder from the sensor head main body so that each of the used crystal oscillators is removed out of the holder. Then, after having taken out the first cap body (when the second cap body is present, both the first and the second cap bodies) from the case main body, the holder is set in position from an upper side thereof while fitting the boss part into the fitting recessed part. At this time, by means of the phase determining means, the first recessed part and the fitting recessed part are brought into a posture of vertically coinciding with each other. Then, by turning the holder and the case main body integrally upside down, each of the crystal oscillators housed in the first recessed part is transferred to the installation recessed part. Finally, after lifting upward the case main body on the holder for separation, the holder will be installed once again on the sensor head main body. As described above, according to this invention, without particularly using a pickup tool such as a pair of tweezers, and the like, a plurality of crystal oscillators housed in the case main body can be set in position (transferred) respectively into the installation recessed parts at a single processing. As a result, as compared with the arrangement in the above-mentioned known art, the workability can be dramatically improved. Still furthermore, there will be no disadvantage such as damaging the main surface of the crystal oscillator.

