JP2006129303A - Manufacturing method of piezoelectric oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a piezoelectric oscillator providing a small-sized piezoelectric oscillator with simple handling and excellent productivity. <P>SOLUTION: The manufacturing method of the piezoelectric oscillator includes steps of: preparing a mother substrate comprising a plurality of oscillator substrate regions and marginal substrate regions and forming monitor electrode pads for measuring piezoelectric vibration elements to the oscillator substrate regions and the marginal substrate regions respectively; mounting the piezoelectric vibration elements on a front principal side of the oscillator substrate regions, measuring the frequency characteristics of the piezoelectric vibration elements, finely adjusting the frequency of the piezoelectric vibration elements and thereafter cutting off wiring patterns from the monitor electrodes formed to the marginal substrate regions of the mother substrate; placing and joining covers sealing the piezoelectric vibration elements onto the oscillator substrate regions and mounting spacer members and oscillation integrated circuit elements on a rear principal substrate of the oscillator substrate regions; and obtaining a plurality of the piezoelectric oscillators by cutting off the oscillator substrate regions along their outer circumferences. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a piezoelectric oscillator used in an electronic device such as a portable communication device.

  Conventionally, a piezoelectric oscillator has been used as one of electronic components used in electronic devices such as portable communication devices. As one of such conventional piezoelectric oscillators, for example, as shown in FIG. 5, a first container body 23 in which a crystal resonator element (not shown) is housed is disposed in a cavity portion 25 of the crystal resonator element. An integrated circuit element 26 that controls oscillation output based on vibration and a structure attached to a second container body 21 in which an electronic component element (not shown) such as a capacitor is accommodated are known. The temperature compensated crystal oscillator is placed on an external wiring board such as a mother board, and an external terminal (not shown) provided on the lower surface of the second container body 21 is soldered to the wiring of the external wiring board. It is mounted on the external wiring board by bonding.

  Note that the first container body 23 and the second container body 21 are usually formed of a ceramic material, and a wiring conductor is formed inside or on the surface thereof, and a conventionally known ceramic green sheet lamination method or the like is used. It is manufactured by adopting.

  The integrated circuit element 26 is provided with a temperature compensation circuit for correcting the oscillation output of the crystal oscillator based on the temperature compensation data created according to the temperature characteristics of the crystal resonator element. After assembling the compensation type crystal oscillator, in order to store the above-mentioned temperature compensation data in the memory of the integrated circuit element 26, writing for temperature compensation data writing is performed on the lower surface and the outer surface of the second container body 21. A control terminal 27 was provided. The temperature compensation data is stored in the memory of the integrated circuit element 26 by applying the probe needle of the temperature compensation data writing device to the write control terminal 27 and inputting the temperature compensation data to the memory in the integrated circuit element 26. The

  The following prior art documents are disclosed about such a piezoelectric oscillator.

Japanese Patent No. 2960374

  The applicant has not found any prior art documents related to the present invention other than the prior art documents specified by the prior art document information described above by the time of filing of the present application.

  However, in the above-described conventional piezoelectric oscillator, usually, only the first container body 23 and the second container body 21 are manufactured by the “multiple picking” technique, and the individual pieces (the first pieces obtained after the division) A crystal resonator element and an integrated circuit element 26 are individually mounted on the container body 23 and the second container body 21), and both are joined to assemble a product.

  However, when the integrated circuit element 26, the first container body 23, and the like are mounted on the second container body 21 after the second container body 21 is divided into pieces, until the operation is completed, It is necessary to individually hold the second container body 21 with a carrier or the like, and the assembling work is complicated, and additional manufacturing equipment such as a carrier is required, which also reduces the productivity of the piezoelectric oscillator. Had the disadvantage of

  However, in the above-described piezoelectric oscillator, the planar shape is reduced from 7 mm × 5 mm to 5 mm × 3 mm, and further 3 mm × 2 mm, and accordingly, the integrated circuit element 26 is strongly required to be reduced in size. As a result, the arrangement region of the integrated circuit element 26 is reduced, the interval between the electrode pads 28 must be reduced, the bonding reliability is lowered, and the routing wiring conductor 29 connected to the electrode pad 28 is further reduced. There was a problem that the degree of freedom was restricted.

  Further, in order to flatten the oscillation output by the oscillation control of the integrated circuit element 26 according to the specific temperature characteristic of the crystal vibrating element 24, before the integrated circuit element 26 is arranged, the specific characteristic of the crystal vibrating element 24 is previously set. It is necessary to measure temperature characteristics. It is difficult to perform this measurement due to the miniaturization of the electrode pad, and the productivity is greatly reduced.

  The present invention has been devised in view of the above-mentioned drawbacks, and an object of the present invention is to provide a method of manufacturing a piezoelectric oscillator capable of obtaining a small piezoelectric oscillator that is easy to handle and excellent in productivity. is there.

In the piezoelectric oscillator of the present invention, an upstanding side wall is formed at the edge of one main surface of a rectangular and flat oscillator substrate, and piezoelectric is formed in the inner wall of the side wall and the recessed space surrounded by the one main surface. After mounting the vibration element and hermetically sealing the recessed space with a lid, an integrated circuit element and a chip-type electronic element that are electrically connected to the piezoelectric vibration element are arranged on the other main surface side of the oscillator substrate, and the oscillator After forming a base on which the external connection electrode terminal is formed at the edge of the other main surface of the substrate, control signals are input / output from / to the integrated circuit element to match the specified numerical values of the piezoelectric oscillator to the desired numerical values. In the manufacturing method of the piezoelectric oscillator,
A replacement substrate region is integrally formed on the outer peripheral side surface of the oscillator substrate region, and an excitation electrode film and an electric electrode formed on the front and back main surfaces of the piezoelectric vibration element are respectively formed on the other main surface of the oscillator substrate region and the replacement substrate region. Each of a pair of monitor electrode pads connected in series is formed, and a plurality of oscillator substrate regions each having a discarded substrate region formed on the outer periphery are arranged in a matrix to form a single substrate. And a process of
Piezoelectric vibration element in a recessed space formed by a side wall portion formed on one main surface of each of the oscillator substrate regions and one main surface of the discarded substrate region and one main surface of the substrate oscillator region Is mounted on the top of the side wall, and a mother lid body integrally including a plurality of outer peripheral lid areas similar to the individual oscillator board areas and discarded board areas of the mother board is disposed, and each concave space is formed as a mother board. A process of hermetically sealing with a lid,
Various characteristics of each piezoelectric vibration element are measured from the monitor electrode pad, and an integrated circuit element is arranged on the other main surface of each oscillator substrate region of the mother substrate on which the piezoelectric vibration element having a desired characteristic value is mounted. Further, a spacer member in which an external connection electrode pad is formed on the other main surface of the oscillator substrate region is disposed and fixed, and each external connection terminal of the integrated circuit element, the piezoelectric vibration element, and the external connection electrode pad are electrically connected. Connecting to
And a step of cutting and dividing the integrated mother substrate and mother lid into individual piezoelectric oscillators along a boundary line between the base oscillator region and the base discarding substrate region. Is the method.

  The method of manufacturing a piezoelectric oscillator as described above, wherein the spacer member is made of a metal post.

  The above-described method for manufacturing a piezoelectric oscillator is characterized in that the spacer members are arranged at the four corners of each oscillator substrate region.

  The integrated circuit element mounted on the mother board is potted with a resin material, and the piezoelectric oscillator manufacturing method is also described above.

  According to the present invention, since the mother board is divided after the oscillation integrated circuit element is mounted on the mother board, the mother board itself accommodates the oscillation integrated circuit element and the crystal vibration element during the manufacturing process. It functions as a carrier for mounting the container body that is mounted, and there is no need for complicated operations such as holding individual mounting substrates obtained by dividing the mother board with the carrier. Thereby, the productivity of the piezoelectric oscillator can be improved.

  Furthermore, according to the present invention, since the spacer members are arranged at the four corners of each oscillator substrate region, each can be used as a terminal after division, so that productivity can be improved. .

  Furthermore, according to the present invention, the extension portion of the write post located in the replacement substrate region is connected to the via conductor embedded in the replacement substrate region of the mother substrate, so that the write post The extending portion can be firmly attached to the discarded substrate region of the mother substrate. Therefore, peeling of the writing post extension due to a difference in linear expansion coefficient or the like is effectively prevented.

  Furthermore, according to the present invention, before mounting the container body in the process, the mounting surface of the oscillation integrated circuit element mounted on the mother substrate is covered with a resin material, so that the oscillation integrated circuit on the mother substrate is covered. As well as improving the fixing strength of the element, it satisfactorily covers the circuit forming surface of the oscillation integrated circuit element, effectively preventing the electronic circuit on the circuit forming surface from being corroded by moisture in the atmosphere, High reliability of the piezoelectric oscillator can be maintained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a partially exploded perspective view of a piezoelectric oscillator manufactured by the manufacturing method of the present invention. The piezoelectric oscillator shown in these drawings is used as an external connection terminal on the lower surface of a container body 1 having a rectangular main surface shape. A plurality of spacer members 9 and an oscillation integrated circuit element 7 (not shown in FIG. 1) are fixed and mounted, and a quartz resonator element 5 is accommodated in a recessed space formed on the upper surface of the container body 1. Has the structure.

  FIG. 2 is a plan view of the piezoelectric oscillator during the manufacturing process as viewed from the direction in which the spacer member 9 and the integrated circuit element are mounted. Including the contents shown in FIG. 1, the container body 1 includes, for example, a substrate 2 made of a ceramic material such as glass-ceramic and alumina ceramic (consent to the oscillator substrate region in the manufacturing process), 42 alloy, Kovar, phosphor bronze. And a lid 4 made of the same metal as the seal ring 3, and the seal ring 3 is attached to the upper surface of the substrate 2, and the lid 4 is placed on the upper surface. The container body 1 is configured by being fixed, and the crystal resonator element 5 is mounted on the upper surface of the substrate 2 located inside the seal ring 3.

  The container body 1 is for hermetically sealing the quartz resonator element 5 in its interior, specifically, in a space surrounded by the upper surface of the substrate 2, the inner surface of the seal ring 3, and the lower surface of the lid body 4. A pair of element connection electrode pads connected to the excitation electrode films formed on the front and back main surfaces of the crystal resonator element 5 are provided on the upper surface of the substrate 2, and a spacer member 9 is provided on the lower surface of the substrate 2. These pads and electrodes are electrically connected to each other through wiring patterns on the surface of the substrate 2 and via hole conductors embedded in the substrate 2.

  On the other hand, the crystal resonator element 5 accommodated in the container body 1 is formed by depositing and forming a pair of excitation electrode films on both main surfaces of a crystal piece cut along a predetermined crystal axis, so that the fluctuation from the outside When a voltage is applied to the crystal piece via a pair of excitation electrode films, thickness shear vibration is caused at a predetermined frequency. The crystal resonator element 5 is fixedly mounted on the upper surface of the substrate 2 by electrically connecting a pair of excitation electrode films to corresponding element connection electrode pads on the upper surface of the substrate 2 through a conductive adhesive. Thus, the electrical connection and the mechanical connection between the crystal resonator element 5 and the container body 1 are simultaneously made.

  Here, if the lid body 4 of the container body 1 is connected to a spacer member 9 for a ground terminal, which will be described later, via the wiring conductor 8 of the container body 1, the lid body 4 made of metal is set to the reference potential during use. Since the shield function is provided by being connected, the crystal resonator element 5 and the oscillation integrated circuit element 7 can be protected better than unnecessary electrical effects from the outside. Therefore, the lid body 4 of the container body 1 is preferably connected to the ground terminal spacer member 9 via the wiring conductor 8 of the container body 1.

  The container body 1 has spacer members 9 arranged at the four corners on the lower surface thereof, and is used as four external connection terminals (power supply voltage terminal, ground terminal, oscillation output terminal, oscillation control terminal). A flip-chip type integrated circuit element 7 for oscillation is disposed in the central area of the lower surface. The spacer member 9 used for the four external connection terminals provided on the lower surface of the container body 1 functions as a terminal for connecting the piezoelectric oscillator to an external wiring board such as a mother board. When mounted on a wiring board, it is electrically connected to the circuit wiring of the external wiring board via a conductive bonding material such as solder.

  Further, the plurality of spacer members 9 provided on the lower surface of the container body 1 ensure a predetermined interval necessary for arranging the oscillation integrated circuit element 7 between the external wiring board and the container body 1. It also has a function. Furthermore, a plurality of integrated circuit element connection electrode pads are provided on the lower surface of the container body 1 described above, and external connection terminals of the integrated circuit element 7 are connected to these integrated circuit element connection electrode pads by Au bumps or solder. The integrated circuit element 7 is attached to a predetermined position on the lower surface of the container body by being electrically and mechanically connected through a conductive bonding material such as an anisotropic conductive adhesive.

  The oscillation integrated circuit element 7 has, on its circuit forming surface (lower surface), a temperature sensing element (thermistor) for detecting the ambient temperature state, a memory for storing temperature compensation data for compensating the temperature characteristics of the crystal resonator element 5, A temperature compensation circuit that corrects the vibration characteristics of the crystal resonator element 5 according to a temperature change based on the temperature compensation data in the memory, an oscillation circuit that is connected to the temperature compensation circuit and generates a predetermined oscillation output, and the like are provided. The oscillation output generated by the oscillation circuit is output to the outside and then used as a reference signal such as a clock signal.

  A resin material 14 made of epoxy resin or the like is interposed in the space for mounting the integrated circuit element 7 formed by the lower surface of the container body 1 and the spacer member 9 described above. Thereby, the fixing strength of the integrated circuit element 7 to the container body 1 is improved, the circuit forming surface of the oscillation integrated circuit element 7 is satisfactorily covered with the resin material 14, and the electronic circuit on the circuit forming surface is in the atmosphere. Corrosion due to moisture or the like can be effectively prevented.

  Next, a manufacturing method of the above-described piezoelectric oscillator will be described with reference to FIG. Here, FIG. 3 (a), FIG. 3 (b), FIG. 4 (a) and FIG. 4 (b) are perspective views for explaining an embodiment of the manufacturing method according to the present invention in this order.

(Process A)
First, as shown in FIG. 3A, in the final product form, a mother board 10 constituted by an oscillator board area A to be a container body 1 in which the crystal resonator element 5 is housed and an abandon board area B integrally formed therearound. And prepare. When the mother substrate 10 is made of a ceramic material such as glass-ceramic, for example, a wiring conductor and a surface of a ceramic green sheet obtained by adding and mixing an appropriate organic solvent or the like to the ceramic material powder. The conductive paste is applied by screen printing or the like known in the art, and a plurality of the pastes are laminated and press-molded, and then fired at a high temperature. FIG. 3B is a perspective view of FIG. 3A viewed from the back side. The front and back main surfaces of the piezoelectric vibration element 5 are respectively formed on the back main surfaces of the oscillator substrate area A and the discarded substrate area B. One of the pair of monitor electrode pads 11 electrically connected to the excitation electrode film formed above is formed.

(Process B)
The mother substrate 10 is formed by arranging a plurality of rectangular oscillator substrate regions A adjacent to each other, and a concave space in which a crystal resonator element 5 is formed in each oscillator substrate region A on the front main surface thereof. Install in. In the crystal resonator element 5, a pair of excitation electrode films are electrically connected to corresponding element connection electrode pads on the inner bottom surface of the recess space (the same as the upper surface of the substrate 2 in FIG. 1) via a conductive adhesive. Accordingly, the quartz resonator element 5 and the oscillator substrate region A are electrically connected and mechanically connected at the same time. Next, as shown in FIG. 3 (b), a frequency measuring device is connected to the monitor electrode pad 11, the frequency of the mounted crystal vibrating element 5 is measured, and an ion beam or the like is used. By adjusting the film thickness of the excitation electrode film, the oscillation frequency of the crystal resonator element 5 is finely adjusted to a desired frequency.

(Process C)
From the same metal as the seal ring 3 on the upper surface of the seal ring 3 made of a metal such as 42 alloy, Kovar, phosphor bronze or the like formed in the recess space opening formed in the oscillator substrate region A on which the crystal resonator element 5 is mounted. The lid body 4 is arranged. The seal ring 3 and the lid 4 are manufactured by adopting a conventionally known metal processing method and molding a metal such as 42 alloy into a predetermined shape. The seal ring 3 is the uppermost surface of the oscillator substrate region A. Is fixed to the oscillator substrate region A by brazing to a conductor layer previously deposited on the substrate. Further, as described above, when the seal ring 3 and the lid 4 are joined by resistance welding, a Ni plating layer, an Au plating layer, or the like is previously deposited on the surfaces of the seal ring 3 and the lid 4.

  Next, as disclosed in FIG. 4A, the integrated circuit element 7 incorporating the spacer member 9 and the oscillation circuit is mounted in each oscillator substrate region A of the mother substrate 10. The integrated circuit element 7 is mounted on one of the monitor electrode pads 11 formed on the back surface of the oscillator substrate area A. As described above, the integrated circuit element 7 is a rectangular flip-chip type integrated circuit element having a plurality of connection terminals on the joint-side surface. In the integrated circuit element 7, a plurality of connection terminals provided on the bonding surface thereof are connected to corresponding integrated circuit element connection electrode pads in each oscillator substrate region A via a conductive bonding material such as solder. The conductive bonding material is placed on the back surface of the mother board 10 so as to come into contact, and then the conductive bonding material is melted by application of heat or the like, and the connection terminals and the integrated circuit connecting electrode pads are bonded to the conductive bonding material. The integrated circuit element 7 is fixed and mounted on the mother board 10 by bonding through the base board 10. A plurality of spacer bonding electrode pads are provided on the back surface of the oscillator substrate region A, and the spacer bonding electrode pads are applied to the corresponding spacer member 11 via a conductive bonding material such as solder. Then, the conductive bonding material is melted by applying heat or the like, and the electrode pad for spacer bonding and the spacer member 11 are bonded to each other through the conductive bonding material. It is fixed.

(Process D)
Finally, as shown in FIG. 4B, the mother board 10 is cut along the outer periphery of each oscillator board area A to divide each oscillator board area A and each discarded board area B. . The mother substrate 10 is cut by dicing using a dicer or the like, and the mother substrate 10 is divided into individual oscillator substrate regions A (containers 1) through such a cutting process. In the present embodiment, since the mother board 10 is divided after the integrated circuit element 7 is mounted on the mother board 10, the mother board 10 itself is integrated with the integrated circuit element 7 when the integrated circuit element 7 is mounted. Therefore, the carrier for mounting an integrated circuit element as described in the section of the conventional example is unnecessary, and individual container body pieces obtained by dividing the mother board 10 are used as carriers. No complicated work such as mounting is required. As a result, the productivity of the piezoelectric oscillator can be kept high. In addition, this invention is not limited to the above-mentioned embodiment, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention.

  In the embodiment described above, the lid 4 is joined to the recess space opening in the oscillator substrate region A via the seal ring 3. Instead, the lid 4 is joined to the recess space opening in the oscillator substrate region A. Alternatively, a metallized pattern may be formed and the lid 4 may be directly welded to the metallized pattern. In the above-described embodiment, the seal ring 3 is directly formed in the recessed space opening of the integrally formed oscillator substrate region A. Instead, the oscillator substrate region A is formed on the upper surface of the flat substrate. In addition, a frame made of the same ceramic material as that of the substrate may be fixed, and the seal ring 3 may be attached to the upper surface of the frame.

  Further, in the embodiment described above, for example, the lid 4 is attached on the container body 1 using the seal ring 3, but instead of this, a bonding conductor such as Au—Sn on the upper surface of the container body is used. On the other hand, the lid body 4 may be directly attached to the container body 1 by bonding, and this case is also included in the technical scope of the present invention. Furthermore, in order to use a piezoelectric oscillator as a temperature compensated oscillator, the plurality of writing posts are provided on the lower surface of the container body 1, and the plurality of writing posts are arranged along two parallel sides of the container body. Each is arranged symmetrically with respect to the center line parallel to the two sides, and one end thereof is electrically connected to the connection pad of the integrated circuit element 7 through the wiring conductor of the container body. It doesn't matter. In the above embodiment, the process of covering the recess space openings formed in the individual oscillator substrate regions of the mother board with the lids and sealing hermetically is disclosed. However, the lids are respectively arranged in the respective recess space openings. Rather, a mother lid that integrally has a plurality of outer peripherally shaped lid regions similar to the individual oscillator substrate regions and the discarded substrate regions is placed on the main surface of the mother substrate and individually sealed. After the integration with the substrate, it may be a step of cutting at a desired cutting location together with the mother substrate.

  Furthermore, the mounting surface of the integrated circuit element 7 may be covered with an insulating resin, and this case is also included in the technical scope of the present invention. Further, in step B, the wiring pattern from the monitor electrode pad 11 formed in the discarded substrate region B is cut. In step C, after the lid 4 is disposed and joined, the crystal resonator 5 is again formed. After the above measurement, the wiring pattern may be cut.

FIG. 1 is an exploded perspective view of a piezoelectric oscillator manufactured by the manufacturing method of the present invention. FIG. 2 is a plan view of the piezoelectric oscillator being manufactured by the manufacturing method of the present invention as viewed from the side of the integrated circuit element mounting surface. FIG. 3A is a perspective view for explaining the method for manufacturing the piezoelectric oscillator of the present invention. FIG. 3B is a perspective view for explaining the next step of FIG. 3A in the method for manufacturing a piezoelectric oscillator of the present invention. FIG. 4A is a perspective view for explaining the next step of FIG. 3B in the method for manufacturing a piezoelectric oscillator of the present invention. FIG. 4B is a perspective view for explaining the next step of FIG. 4A in the method for manufacturing a piezoelectric oscillator of the present invention. FIG. 5 is an exploded perspective view showing one embodiment of a conventional piezoelectric oscillator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Container body 4 ... Cover body 5 ... Crystal oscillation element 7 ... Integrated circuit element 9 ... Spacer member 10 ... Mother board 11 ... Monitor electrode pad 12 ... Resin material A ・ ・ ・ Oscillator board area B ・ ・ ・ Disposal board area

Claims (4)

An upstanding side wall is formed on the edge of one main surface of the rectangular and flat oscillator substrate, and a piezoelectric vibration element is mounted in the recess space surrounded by the side wall and the main surface. Is hermetically sealed with a lid, and an integrated circuit element and a chip-type electronic element that are electrically connected to the piezoelectric vibration element are disposed on the other main surface side of the oscillator substrate, and the other main surface of the oscillator substrate is disposed. Manufacturing a piezoelectric oscillator that forms a base on which external connection electrode terminals are formed on the edge of the surface, and then inputs / outputs control signals to / from the integrated circuit element from the outside to match the specified numerical value of the piezoelectric oscillator to a desired value In the method
An exciter substrate region is integrally formed on the outer peripheral side surface of the oscillator substrate region, and an excitation electrode film formed on each of the other main surfaces of the oscillator substrate region and the surrogate substrate region on the front and back main surfaces of the piezoelectric vibration element; A mother comprising a plurality of oscillator substrate regions, each of which is formed of a pair of electrically connected monitor electrode pads and in which a plurality of the oscillator substrate regions are formed on the outer periphery. Forming a substrate;
In a recess space formed by a side wall portion formed on one main surface of each oscillator substrate region and one main surface of the discarded substrate region, and one main surface of the substrate oscillator region Mounting a piezoelectric vibration element, disposing a lid on the top of the side wall, and hermetically sealing each of the recessed spaces with the lid;
Various characteristics of each piezoelectric vibration element are measured from the monitor electrode pad, and are integrated on the other main surface of each oscillator substrate region of the mother board on which the piezoelectric vibration element having a desired characteristic value is mounted. A circuit element is arranged and fixed, and a spacer member having an external connection electrode pad formed on the other main surface of the oscillator substrate region is arranged and fixed, each external connection terminal of the integrated circuit element, the piezoelectric vibration element, Electrically connecting the electrode pad for external connection;
A step of cutting and dividing the integrated mother substrate and the mother lid into individual piezoelectric oscillators along a boundary line between the base oscillator region and the base replacement substrate region. A method for manufacturing a piezoelectric oscillator.   The method for manufacturing a piezoelectric oscillator according to claim 1, wherein the spacer member is made of a metal post.   3. The method of manufacturing a piezoelectric oscillator according to claim 1, wherein the spacer members are arranged at four corners of each oscillator substrate region. 4.   4. The method for manufacturing a piezoelectric oscillator according to claim 1, wherein the integrated circuit element mounted on the mother substrate is potted with a resin material.

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