Abstract:
A system for simultaneous frequency trimming of a plurality frequency devices such as oscillators, crystals and surface acoustic wave filters and resonators by removing intrinsic or previously deposited material through plasma ion bombardment is comprised of a plasma ion chamber, a magazine rack, a vacuum evacuator, a control console, a plasma power supply and a frequency evaluator. The system employs a shutter assembly and shutter control mechanism to individually regulate plasma ion bombardment of a plurality of frequency devices.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to adjustment or trimming systems for frequency devices such as oscillators, crystals and surface acoustic wave filters and resonators. Specifically, this invention is a system for trimming devices to a pre-determined frequency by removing intrinsic or previously deposited materials through a controlled plasma ion bombardment process. 
     2. Description of the Related Art 
     In the prior art, trimming of frequency devices such as oscillators, crystals and surface acoustic wave filters and resonators depended on several techniques. For those devices where material such as precious and semi-precious metal is deposited or sputtered on to the frequency device, the technique is to carefully control the deposition of material on the frequency device such that the target frequency is achieved without the necessity of the subsequent removal of the deposited material. A disadvantage to this technique is the requirement to constantly attend to the deposition apparatus to insure that an adequate supply of deposition material was available within the apparatus during the deposition process. Another disadvantage to this technique is that the deposition of material take place on a part by part basis, which is a time consuming, and thus costly process. Also, extreme care must be exercised not to over deposit the material on the frequency device. 
     A second technique relied on batch processing of the material deposition on several devices simultaneously. The batch processing aspect of this technique would require the over approximation of the target frequency by depositing perhaps slightly more material than required. Following the deposition step, each part would be individually trimmed to the target frequency by a plasma ion process or other suitable process to remove a small portion of the deposited material. For those frequency devices not undergoing deposition of material, the trimming of intrinsic material, e.g. material comprising the substrate, such as silicon dioxide, also requires a part by part process under the prior art. Again, the time consuming nature of trimming each part individually, whether trimming of deposited material or intrinsic material, is a disadvantage to this procedure. 
     Therefore, a solution to the costly and unproductive limitations imposed by the prior art was needed for trimming frequency devices to the target frequency. 
     BRIEF SUMMRRY OF THE INVENTION 
     It is an object of the present invention to provide a complete system for the simultaneous frequency trimming of a plurality of frequency devices such as oscillators, crystals and surface acoustic wave filters and resonators. 
     It is another object of the present invention to provide a plasma ion chamber for simultaneous frequency trimming of a plurality of frequency devices such as oscillators, crystals and surface acoustic wave filters and resonators. 
     It is another object of the present invention to provide a ionization station for the simultaneous frequency trimming of a plurality of frequency devices such as oscillators, crystals and surface acoustic wave filters and resonators. 
     It is still another object of the present invention to control the trimming of a plurality of frequency devices by permitting or restricting the effects of plasma ion bombardment on a device by device basis. Trimming control is provided by a shutter assembly comprised of a plurality of individual shutters, wherein each of the individual shutters corresponds to a frequency device. Plasma ion bombardment of a frequency device is permitted by selecting an open position for an individual shutter and plasma ion bombardment of a frequency device is restricted by selecting the closed position of an individual shutter corresponding to a particular frequency device. 
     It is still another object of the present invention to determine the frequency and acquire other data from the frequency device without having to remove the frequency device from the system or the plasma ion chamber. 
     It is still another object of the present invention to determine the frequency and acquire other data from the frequency device while plasma ion bombardment is occurring to the frequency device. 
     In accordance with one embodiment of the present invention, a system for trimming frequency devices, comprises a plasma ion chamber for ion bombardment of the frequency devices; a magazine rack coupled to the plasma ion chamber for storing a plurality of the frequency devices; a vacuum evacuator coupled to the plasma ion chamber for creating a vacuum in the plasma ion chamber; a plasma power supply coupled to the plasma ion chamber for providing power to an ion gun; a frequency evaluator coupled to the plasma ion chamber for determining the frequency of the frequency devices; and a control console coupled to the plasma ion chamber, the magazine rack, the vacuum evacuator, the plasma power supply and the frequency evaluator for controlling the operation of the system. 
     In accordance with another embodiment of the present invention, a plasma ion chamber for trimming frequency devices comprises a bell jar for providing a hermetically sealable chamber for conducting plasma ion bombardment; a bell jar hinge assembly coupled to the bell jar for opening and closing a surface of the bell jar; an insertion/extraction port coupled to the bell jar for inserting and removing the frequency devices from the plasma ion chamber; an ion gun coupled to the bell jar for conducting plasma ionization within the plasma ion chamber; a baseplate located internal to the bell jar for mounting a plurality of mechanical components; a drive assembly coupled to the baseplate for controlling the movement of a boat containing the frequency devices; an ionization station coupled to the baseplate for regulating the plasma ion bombardment of the frequency devices; and a shutter mechanism coupled to the baseplate for interfacing with the ionization station. 
     In still another embodiment of the present invention, an ionization station for trimming frequency devices comprises a contact mechanism coupled to a baseplate; a shutter assembly coupled to the contact mechanism for regulating plasma ion bombardment of the frequency devices; and a top etching shield coupled to the shutter assembly for protecting the contact mechanism from the plasma ion bombardment; wherein the contact mechanism comprises a probe assembly for acquiring data from the frequency devices; and a linear slide coupled to the probe assembly for controlling vertical movement of the probe assembly. 
     The foregoing and other objects, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiments of the invention, as illustrated in the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a block diagram of the present invention comprising a plasma ion chamber, a magazine rack, a vacuum evacuator, a plasma power supply, a control console, and a frequency evaluator. 
     FIG. 2 is a perspective view illustrating the plasma ion chamber including the plasma ion gun, the vacuum evacuator and the magazine rack. 
     FIG. 3 is a perspective view of portions of the magazine rack and certain internal components of the plasma ion chamber. 
     FIG. 4 is a perspective view of certain internal components of the plasma ion chamber including a baseplate for mounting a plurality of mechanical components, a drive mechanism for transporting the boats to and from the magazines, an ionization station and a shutter mechanism. 
     FIG. 5 is a perspective view of the ionization station illustrating the contact mechanism, the shutter assembly, the probe assembly, and the pallet retainer. 
     FIG. 6 is a perspective view of a decomposed ionization station without the shutter assembly and the pallet retainer thereby more clearly illustrating the probe assembly. 
     FIG. 7 is a top view of the shutter assembly which illustrates several of the shutters in an open position and several of the shutters in a closed position. 
     FIG. 8 is a perspective view of the bottom of the shutter assembly and the interface to the shutter mechanism. This figure illustrates the shutter mechanism actuator rod engaging one of the individual shutters at the shutter tab to close the shutter. 
     FIG. 9 is a top perspective view of an unpopulated boat. The illustrated boat is not populated with pallets or frequency devices. This figure illustrates the basic geometry of the boat and of the pallet apertures within the boat. 
     FIG. 10 is a top perspective view of boat populated with pallets. The pallets themselves are unpopulated, i.e. the frequency devices are absent. The device aperture matrix for each pallet is visible. The pallets are held in place on the boat by a series of tabs around the perimeter of the pallet aperture. 
     FIG. 11 is a top perspective view of a fully populated boat, i.e. the boat is populated with pallets and each pallet is populated with a full consignment of frequency devices. The fully populated boat is loaded into the magazine (not shown). 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a block diagram of the plasma ion trimming system (“system”)  10  for frequency devices is illustrated. The system  10  is comprised of a plasma ion chamber  100 , a magazine rack  200 , a vacuum evacuator  300 , a control console  400 , a plasma power supply  500 , and a frequency evaluator  600 . The plasma ion chamber  100 , the magazine rack  200  and the vacuum evacuator  300  are described in detail below. 
     The control console  400  is typically a personal or minicomputer with customized I/O interfaces to the plasma ion chamber  100 , the magazine rack  200 , the vacuum evacuator  300 , the plasma power supply  500  and the frequency evaluator  600 . The control console  400  executes custom software which oversees the operation of the system  10 . The system  10  is operated from the control console. 
     The plasma power supply  500  is typically an original equipment manufactured (OEM) device which supplies the appropriate power requirements of the plasma ion gun. The plasma ion gun, which is a component of the plasma ion chamber  100 , is the device which removes the intrinsic or previously deposited material from frequency devices via ion bombardment. The control console  400  is coupled to the plasma power supply  500  for controlling the power available to the plasma ion gun. 
     The frequency evaluator  600  is also an OEM device which is coupled to the plasma ion chamber  100  and to the control console  400 . The frequency evaluator  600  receives data from the frequency devices undergoing ion bombardment for the removal of intrinsic or previously deposited material. From the data received, the actual frequency of the frequency device, is determined while the frequency device is within the plasma ion chamber  100 . 
     That is, one aspect of the system  10 , is that the frequency devices can be evaluated on a real time basis while undergoing trimming and located within the system  10 . An improvement over the prior art, the frequency devices need not be removed from the system  10  for frequency evaluation. Even when plasma ion bombardment is taking place, the control console  400  and the frequency evaluator  600  are receiving data from the frequency devices. The data received from probing the devices may be output to the central console  400  and to the frequency evaluator  600 . 
     Referring to FIG. 2, wherein like numerals represent like elements from the preceding figure, a perspective view of several components of the present invention are shown including the plasma ion chamber  100 , the magazine rack  200 , and portions of the vacuum evacuator  300 . The control console  400 , plasma power supply  500 , and frequency evaluator  600  are not shown, but would reside in a cabinet, work station or other type of suitable station, adjacent to those components which are shown. 
     Ion bombardment, and thus frequency trimming which is the ultimate objective of the system  10 , occurs within the plasma ion chamber  100 . There are a variety of components, in terms of differing performance and capacity, such as the magazine rack  200 , the vacuum evacuator  300 , the control console  400 , the plasma power supply  500  and the frequency evaluator  600 , which may interface with the plasma ion chamber  100 . 
     The external portions of the plasma ion chamber  100  are shown in FIG.  2 . These include the bell jar  101  which is the vacuum tight casing for the chamber, the ion gun  102  (only the cover for the ion gun is visible in FIG.  2 ), the insertion/extraction port  103  and the bell jar hinge assembly  104 . The internal components of the plasma ion chamber  100  are discussed in detail below. 
     The bell jar  101  is typically a hermetically sealable metal case. On at least one surface of the bell jar  101  is a porthole  105  for viewing of the internal componentry of the plasma ion chamber  100 . In the embodiment shown in FIG. 2, several portholes  105  are shown. 
     The ion gun  102  is mounted on the top surface  106  of the bell jar  101 . The ion gun  102  projects down into the inside of the plasma ion chamber  100 . Existing, but not shown, are the electrical connections between the ion gun  102  and the control console  400  and the plasma power supply  500  of FIG.  1 . The ion gun  102  is typically OEM equipment. 
     In the preferred embodiment, the bell jar  101  is a rectangular box-like shape. That is, the two lateral sides, top  106  and bottom surfaces are rectangular and some what elongated as compared to the two end surfaces which tend to be more square-like, but not necessarily a perfect square. The bell jar  101  is shaped as such to accommodate the geometry of the boats  210 , discussed below, which contain the frequency devices, i.e. the subjects of the frequency trimming process. 
     The insertion/extraction port  103  is coupled to one end surface of the bell jar  101 . The function of the insertion/extraction port  103  is to provide an opening in the bell jar  101  for the insertion and extraction of the boat  210  which contain the frequency devices. FIG. 2 illustrates a boat  210  shown being inserted into or extracted from the plasma ion chamber  100  via the insertion/extraction port  103 . The insertion/extraction port  103  is also capable of sealing the opening in the bell jar  101  once the devices are inserted into the plasma ion chamber  100  so that a vacuum may be created. 
     The bell jar hinge assembly  104  is coupled to the opposite end of the bell jar  101  from the insertion/extraction port  103 . The function of the bell jar hinge assembly  104  is to provide a mechanism for opening or separating the top surface  106  of the bell jar  101  from the lateral and end surfaces. The bell jar hinge assembly  104  is comprised of a damped, pivoting hinge. In the embodiment shown in FIG. 2, the bell jar hinge assembly  104  is manually operated. However, in other embodiments a motorized bell jar hinge assembly  104  may be implemented. In such an embodiment, the operation of the bell jar hinge assembly  104  maybe automated from the control console  400 . 
     The top surface  106  of the bell jar  101  may be opened for servicing the internal components of the plasma ion chamber  100 . When there is no vacuum within the plasma ion chamber, the top surface  106  of the bell jar  101  may be lifted by a handle attached to the top surface  106  (not shown) and the bell jar  101  may be opened by pivoting the top surface  106  via the bell jar hinge assembly  104  away from the remainder of the bell jar  101 . The ion gun  102 , which is attached to the top surface  106  of the bell jar  101 , pivots accordingly when the top surface  106  is opened. 
     As part of the bell jar hinge assembly  104 , a dampener holds the top surface  106  in an open position and dampens the return of the top surface  106  to the closed position. When in the closed position, an O-ring (not shown) serves to create a seal as between the top surface  106  and the remainder of the bell jar  101  so that a vacuum may be effected. 
     The magazine rack  200  is comprised of a two station magazine elevator  201  and boat pusher assembly  202 . A magazine  203  is mounted at each station. One station is the active station, i.e. the station from which devices are fed into the plasma ion chamber from the magazine, shown as the upper station in FIG.  2 . The other station is the standby station, i.e. the station from which are loaded and unloaded from the magazine elevator, shown as the lower station in FIG.  2 . When trimming the frequency devices in the magazine  203  loaded on the active station is complete, the magazine elevator  201  toggles the active station to the standby station and the standby station to the active station. At the standby station, the magazine  203  containing the frequency trimmed devices is removed and a fresh magazine of devices requiring trimming is loaded. Thus, the magazine elevator  201  shuttles the loaded magazines  203  as between the two stations. 
     The vacuum evacuator  300  is coupled to the plasma ion chamber  100  for the purpose of creating a vacuum within the bell jar  101  prior to plasma ion bombardment. The vacuum evacuator is comprised of a gate valve  301 , a vacuum pump (not shown) and appropriate hardware to couple the gate valve  301  and the vacuum pump to the plasma ion chamber  100 . The operation of the vacuum evacuator of whether to create or release the vacuum within the bell jar  101  is effected by the control console  400 . 
     Referring to FIG. 3, wherein like numerals represent like elements from the preceding figures, portions of the magazine rack  200  and certain mechanical components which are internal to the plasma ion chamber  100  are shown. 
     Each magazine  203  may contain a plurality of boats  210 . In FIG. 3, only one boat  210  is shown, partially extended from the magazine  203 . However, the magazine  203  has the capacity for numerous boats  210 . A boat  210  is a rectangular shaped tray with a plurality of pallet apertures  211  as shown in FIG.  9 . The pallet apertures  211  are typically arranged in a sequential or linear fashion. Each pallet aperture  211  is capable of accommodating a pallet  212  as shown in FIG.  10 . The pallet  212  is positioned over the pallet aperture  211  and held in place by a plurality of tabs. Thus, the boat  210  is capable of accepting a pallet  212  for each of the pallet apertures. The illustrated boat  210  is shown with five pallets  212 , however, boats  210  of different configurations are possible. 
     Each pallet  212  as shown in FIG. 10 is comprised of a metal plate with a plurality of device apertures  213 . The device apertures  213  are typically arranged in matrix format, however, other formats, symmetrical or asymmetrical, including linear, are possible. In the preferred embodiment, a frequency device which requires frequency trimming is inserted into each of the device apertures  213 . 
     FIG. 11 illustrates a boat  210  with five pallets  212 . Each of the five pallets  212  is fully loaded with frequency devices  99 . Referring once again to FIGS. 2 and 3, one or more boats  210  are positioned laterally in each of the magazines  203 . The magazines  203  are loaded onto the magazine rack  200 . 
     One end of the magazine  203  interfaces with the insertion/extraction port  103  (FIG. 2) of the plasma ion chamber  100 . An opposite end of the magazine  203  interfaces with a boat pusher assembly  202 . With the magazine  203  at the active station, the magazine elevator  201  will precisely align the selected boat  210  with the insertion/extraction port  103  and with the boat pusher assembly  202  by vertically adjusting or moving the magazine  210  so that precise alignment is achieved. 
     Upon command, the boat pusher assembly  202  will couple to the selected boat  210  and insert the selected boat  210  into the plasma ion chamber  100 . Upon completion of the ion trimming process for all the devices contain in the boat  210 , the boat pusher assembly  202  will then extract the boat  210  from the plasma ion chamber  100 , returning the boat  210  to its assigned location within the magazine  203 . The magazine elevator  201  will then align the next selected boat  210  in the magazine  203  with the insertion/extraction port  103  and with the boat pusher assembly  202  by a vertical adjustment of the magazines&#39;s position. This alignment and insertion/extraction process is repeated for all boats  210  in the magazine  203  at the active station. 
     Several of the internal components of the plasma ion chamber  100  are shown in FIG.  3 . These components include a baseplate  110  for mounting a plurality of mechanical components, a drive mechanism  120  for transporting the boats to and from the magazines, an ionization station  130 , and a shutter mechanism  140 . Mounted on the underside of the baseplate  110  are several motor drives, typically stepper motors, for controlling the positioning of the selected boat  210  and the operation of the shutter mechanism  140 . 
     Referring to FIG. 4, wherein like numerals represent like elements from the preceding figures, many of the internal components of the plasma ion chamber  100  are further illustrated. The base plate  110  is rectangular shape and is horizontally located within the bell jar  101  (FIG.  2 ). 
     The drive assembly  120  is coupled to the baseplate  110 , and is comprised of a plurality of drive wheels  121 , boat positioning sensors  122 , fixed vee guide rollers  123 , friction drive motors  124 , friction drive pulleys  125 , and vee tension guide rollers  126 . The purpose of the drive assembly  120  is to accurately feed or index the selected boat  210  from the magazine  203  to the ionization station  130  and back to the magazine  203  after frequency trimming of the devices is complete. 
     Once the boat pusher assembly  202  (FIG. 3) inserts the selected boat  210  into the plasma ion chamber  100 , the drive assembly  120  assumes control of the boat  210  and feeds or indexes the selected boat  210  to the ionization station  130 , on a pallet by pallet basis. That is, the plasma ionization process which occurs at the ionization station  130  takes place with respect to one pallet at a time and sequentially for each pallet within the selected boat  210 . The pallet selected for plasma ion bombardment is maneuvered into the ionization station  130  by the assortment of drive assembly wheels  121 , guides  123  and  126 , motors  124 , and pulleys  125 . The selected boat  210  will be laterally positioned by the guide rollers  123  and  126 . The system  10  determines boat position within the plasma ion chamber  100  by one or more boat position sensors  122 . 
     Several components of the ionization station  130 , which is coupled to the baseplate  110 , are shown. These components include the top etching shield  131 , which serves to protect against inadvertent etching of the ionization station  130  itself and components adjacent to the ionization station  130  during plasma ion bombardment. The top etching shield  131  is typically fabricated from a low sputter yield material such as graphite or carbon. Also shown in FIG. 4 is a top view of the shutter assembly  140 , which is comprised of a plurality of individual shutters, and a partial view of the contact mechanism  150 . The shutter assembly  140  and the contact mechanism  150  are both discussed in greater detail below. 
     Additionally shown in FIG. 4 is the shutter mechanism  160 , which is coupled to the base plate  110 . The purpose of the shutter mechanism  160  is to effect opening and closing of the individual shutters within the shutter assembly  140 . The shutter mechanism  160  is discussed in greater detail below. 
     The electrical bulkhead  170  is located on the top surface of the baseplate  110 . The electrical bulkhead  150  serves as a connector for wiring (not shown) as between the ionization station  130  and the remainder of the system  10 , in particular the control console  400  and the frequency evaluator  600 . 
     Referring to FIG. 5, wherein like numerals represent like elements from the preceding figures, a more detailed view of the shutter assembly  140  and the contact mechanism  150  is shown. The drive assembly  120  (FIG. 3) indexes the selected boat  210  such that one of the pallets is aligned with the pallet retainer  141 . The aligned pallet is now in position for plasma ion bombardment. 
     The shutter assembly  140  comprises a plurality of individually controllable shutters which when in the open position permit passage of the plasma ion beam, thereby resulting in removal of material from the frequency device directly below and aligned with the open shutter. In the closed position, the passage of the plasma ion beam is restricted thereby resulting in no further removal of material from the frequency device directly below and aligned with the closed shutter. 
     One function of the contact mechanism  150  is to position the probe assembly  151  for contact with the frequency devices on the aligned pallet. The probe assembly  151  is comprised of a plurality of individual probes  152 , where each probe  152  corresponds to a frequency device. When the pallet is being aligned with the shutter assembly  140  and the pallet retainer  141  or when ion bombardment is underway, the probe assembly  151  is positioned at the bottom of its travel thereby not contacting the devices. On command from the control console  400 , the probe assembly  151  is elevated so that each individual probe  152  makes contact with electrodes on the underside of each of the frequency devices which have been mounted on the aligned pallet. Thus, the probe assembly  151  makes contact with the frequency devices from the underside of the pallet and the ionization process takes place via the shutter assembly  140  from the top side of the pallet. 
     When a probe  152  makes electrical contact with electrodes on one of the frequency devices, the probe  152  energizes the device to begin producing output data. Once the frequency devices are energized, an accurate measurement of frequency and other desired parameters can be ascertained from the data by the frequency evaluator  600  via the probe assembly  151  and the individual probes  152 . This data may be displayed and/or recorded by the control console  400 . After all of the frequency devices in the pallet at the ionization station  130  have been trimmed to the proper frequency, the probe assembly  151  is commanded to descend, thereby breaking contact with the frequency devices. 
     At least one connector  153  serves to electrically connect the contact mechanism  150  with the control console  400  via the electrical bulkhead  170  (FIG.  4 ). The control console  400 , through executing a software program, outputs commands in the form of electrical signals which positions the probe assembly  151  with respect to the frequency devices of the aligned pallet. The probe assembly  151  is electrically connected to the control console  400  and to the frequency evaluator  600  for the purpose of energizing or stimulating the frequency devices and outputing data read by the probes  152 . The probe assembly  151 , controlling each of the individual probes  152 , energizes each of the frequency devices and outputs data to the control console  400  and to the frequency evaluator  600 . 
     Referring to FIG. 6, the shutter assembly of FIG. 5 has been removed and the contact mechanism  150  and probe assembly  151  is more clearly illustrated. The probe assembly  151  is comprised of a plurality of individual probes  152  which are laid out in matrix form. Each probe  152  has one or more contacts  154  which may be electrically coupled to the electrode on the counterpart frequency device. The probe assembly  151  is mounted on a printed circuit board  155  (PCB). 
     The movement of the probe assembly  151  is briefly described. The probe assembly  151  and PCB  155  are coupled to mechanical components which include a linear slide  191 , cam followers  192 , cam blocks  193 , lift shafts  194 , a linkage arm  195  and a contact mechanism motor (not shown). Upon command from the control console  400 , the contact mechanism motor, which is typically mounted on the underside of the baseplate  110  (FIG. 4) drives the linkage arm  195  in with a rotary motion. The rotary motion causes movement of the linear slide  191  portion of the contact mechanism  150 . The cam followers  192  on either side of the contact mechanism  150  begin angled travel within the cam blocks  193 . The angled travel of the linear slide  191  causes a vertical travel of the probe assembly  151  and the PCB  155  along the lift shafts  194 . 
     It is the vertical travel along the lift shafts  194  that raises and lowers the probe assembly  151  to make and break contact with the frequency devices. Rotary motion of the linkage arm  195  in one direction causes a corresponding ascending motion of the probe assembly  151  and the PCB  155 . Rotary motion in the opposite direction will cause a corresponding descending motion of the probe assembly and PCB  155 . 
     Referring to FIG. 7, a top perspective view of the shutter assembly  140  is shown. The shutter assembly is comprised of a material plate with a plurality of apertures in matrix form and a corresponding plurality of individual shutters  142 , each of which shutter  142  resides within an aperture. Each of the shutters  142  may be mechanically opened or closed in a manner as described below. The shutter  142  rotates on an axle or pin (not shown) to achieve either an open or closed position. Shutter  142  illustrates a shutter in an open position. Shutter  142   a  illustrates a shutter in a closed position. 
     Note that the shutter assembly  140  (FIG.  5 ), the pallet and the probe assembly  151  share a common matrix configuration. In the embodiment shown in FIGS. 5 and 6, the matrix is 5 rows and 5 columns for a total of 25 devices. The apparatus can be engineered for a variety of different matrices depending upon process and other parameters. The matrix may be symmetrical as shown, i.e. equal number of rows and columns or asymmetrical, i.e. number of rows different from number of columns. Furthermore, a pallet may be fully or partially loaded with frequency devices thereby permitting increased flexibility of the frequency trimming process. 
     Referring to FIG. 8, a view of portions of the shutter mechanism and of the underside of the shutter assembly  140  is shown. The portion of the shutter mechanism shown comprises the actuator rod mount (“mount”)  161  and the actuator rod  162  which is mechanically connected to the mount  161 . The mount  161  is coupled to the X-Y direction stepper motors (not shown) which control the movement of the mount  161  and thus the actuator rod  162 . The X-Y direction stepper motors are connected to and controlled from the control console  400  (FIG.  1 ). 
     Each of the shutters  142  has a tab  143 . The actuator rod  162  has an angled end  163  which engages the tab  143 . Moving the tab  143  in one direction opens the shutter  142  by a partial rotation around the axle. Moving the tab  143  in the opposite direction closes the shutter  142 . In the preferred embodiment, moving the tab  143  away from the shutter mechanism  160 , also seen as pushing the tab  143 , has the effect of closing the shutter  142 . Conversely, moving the tab  143  toward the shutter mechanism  160 , also seen as pulling the tab  143 , will open the shutter  143 . The opposite mechanical process, i.e. push to open and pull to close, is readily foreseeable by, for example, rotating the shutter assembly  140 . 
     Referring to FIGS. 1-11, the operation of the system  10  is as follows. The pallets  212 , boats  210  and magazines  203  are loaded with frequency devices that require frequency trimming. The magazines  203  are loaded onto the magazine elevator  201 . From this point forward the system  10  is under the control of the control console  400  and manual intervention is typically not required until a completed magazine  203  is removed and replaced with a fresh magazine. 
     The magazine elevator  201  positions one of the magazines  203  at the active station. Fine positioning occurs so that the selected boat  210  is aligned with the boat pusher  202  and with the insertion/extraction port  103  of the plasma ion chamber  100 . The boat pusher  202  engages the selected boat  210  and begins pushing the selected boat  210  towards the plasma ion chamber  100 . 
     At the appropriate time, the control console  400  opens the insertion/extraction port  103  and the selected boat  210  enters the bell jar  101 . The selected boat  210  engages the drive assembly  120  and the drive assembly  120  takes control of the selected boat  210  from the boat pusher. Once the selected boat is fully within the bell jar  101 , the control console  400  closes the insertion/extraction port, thereby sealing the chamber  100 . 
     As the drive assembly  120  positions the first pallet  212  at the ionization station  130 , the vacuum evacuator  300  begins creating a vacuum in the bell jar  101 . Once the pallet  212  is aligned with the pallet retainer  141  within the ionization station  130 , the contact mechanism  150  activates the probe assembly  151  to make contact with the frequency devices  99 . 
     Each of the frequency devices is energized and output data from the frequency devices  99  is sent to the frequency evaluator  600  and control console  400  via the probe assembly  151 . The control console  400  will issue the appropriate commands to the shutter mechanism  160  to either open or close the shutters  142  of the shutter assembly  140 . After the shutter  142  position is complete, the control console  400  will command that the ion gun  102  be turned on and the ionization process begins. 
     As the frequency devices  99  are trimmed, the control console  400  will monitor frequency and other parameters and send commands to the shutter mechanism  160  to either open or close individual shutters  142 . An open shutter  142  results in ion bombardment for the corresponding frequency device  99  and thus the removal of intrinsic or previously deposited material. A closed shutter  142   a  prevents the occurrence of ion bombardment to the corresponding frequency device  99 . The plasma ion process continues until all frequency devices  99  on a pallet  212  are properly trimmed. 
     After the ionization process is completed for all the frequency devices  99  on a pallet  212 , the drive assembly  120  positions the next pallet  212  in the selected boat  210  at the ionization station  130 . This process repeats until all the pallets  212  in the selected boat  210  are completed. Once complete, the vacuum evacuator  300  restores normal atmosphere to the plasma ion chamber  100  and the insertion/extraction port may be opened. 
     The drive assembly  120  begins ejection of the selected boat  210  from the plasma ion chamber  100 . The boat pusher  202  engages the completed boat  210  and extracts it from the plasma ion chamber, thereby returning the boat  210  to its location within the magazine  203 . Thus, the bidirectional nature of the drive assembly  120  permits the selected boat  210  to enter and exit the plasma ion chamber  100  from a common port. 
     Once the completed boat  210  is fully secured in the magazine  203 , the magazine elevator  201  indexes the magazine  203  to the next selected boat  210 . The ionization process described above is repeated for the next selected boat  210  and for each remaining boat  210  in the magazine  203 . After the system  10  has completed trimming of all the frequency devices  99  for the magazine  203  at the active station, the magazine elevator  201  toggles the magazines  203  as between the active and standby stations. 
     The bombardment or sputtering technique of removing deposited material from the frequency devices  99  is implemented by ionizing argon gas. The detriment of the plasma gas technique in removing deposited material is that it also sputters material from other components in the plasma ion chamber  100 . For example, the shutters  142  are made of aluminum, which sputters when bombarded by the argon gas. 
     This inadvertent, undesirable and unintentional sputtering has negative effects. One effect is a reduction in the longevity of the aluminum shutters  142  and other components exposed to the argon gas. As the aluminum is sputtered off the shutters  142 , there is an increasing possibility of mechanical failure of the shutter assembly  140 . Also, although much of the sputtered aluminum is removed by the vacuum evacuator  300 , there is a possibility that at least some of the vaporized aluminum will migrate to the frequency devices  99  thereby producing anomalies in the process and defects in the frequency devices  99 . 
     To alleviate the problem of aluminum sputtering, oxygen is added to the argon gas. The ionized oxygen reacts with the aluminum to form an aluminum dioxide layer on the surface of aluminum components such as the shutters  142 . The aluminum dioxide layer serves to retard the undesirable sputtering of the aluminum components. 
     Similarly a similar problem exists with undesirable sputtering and migration of carbon based components such as the top etching shield  131 . The addition of the oxygen to the argon gas results in ionized oxygen reacting with the sputtered carbon to form carbon dioxide. The carbon dioxide is then removed from the plasma ion chamber  100  by the vacuum evacuator  300 . In the absence of the oxygen additive, the carbon would sputter and migrate to the frequency devices  99  and to exposed components in the plasma ion chamber  100  such as the shutters  142 , thereby reducing the performance of the system  10 . 
     Although the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that changes in form and detail may be made therein without departing from the spirit and scope of the invention.