JP2003022911A - Thin film coil module, its manufacturing method and its using method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film coil module, its manufacturing method and its using method which is superior in heat radiation characteristic and hence allows a high current to flow. SOLUTION: The thin film coil module comprises a thin film coil array 1 of thin film coil elements C arranged in a two-dimensional matrix and buried in a coil insulation member, a diode array 3 of diodes D arranged in a matrix synchronous with the matrix layout of the coil elements, and a heat sink 2 made of a high heat conductive material. The heat sink is sandwiched between the arrays 1, 3. The coil insulation member is a diamond thin film 1i.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film coil module such as a sensor and an actuator to which a micromachining technique is applied, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A thin-film coil module in which thin-film coils are two-dimensionally arranged is applied to a magnetic sensor, a display device, a transfer device capable of two-dimensional transfer on a plane, or the like. In order to select and energize an arbitrary coil in the thin film coil, it is necessary to connect diodes or transistors in series and electrically separate the elements. FIG. 4 is an equivalent circuit of a two-dimensionally arranged thin film coil module. Coil C and diode D are connected in series and one row of coil C
Are connected to one common wiring (column) Lc, and the diode D is connected to one common wiring (row) Ld. Only the coils connected to the selected row and column are energized.

As an example of performing similar electrical element isolation,
For example, in a liquid crystal display device, the drive current is extremely small.
The m 2 thin film transistor array can be formed on the same glass substrate as the liquid crystal display section. However, in the application of actuators for thin-film coil modules, it is necessary to switch amperes of current, and the dimensions of transistors must be as large as mm, so this is realized on the same substrate as the coil using a thin-film process. It was difficult.

Therefore, the following structure and manufacturing process have been adopted. FIG. 5 is a perspective view of main components of a conventional thin film coil module. Thin film coils insulated from each other are two-dimensionally arranged on a ceramic substrate 2 having a good heat transfer property to form a thin film coil array 1. One end of the thin-film coil in each row arrangement is connected to the common wiring Lc, and the other end is connected to the wiring 12d penetrating the ceramic substrate 2. In the diode array 3, diodes are two-dimensionally arranged at positions facing each thin-film coil, and a common wiring Ld is connected to the array of diodes. A flexible printed (PFC) substrate 4 for wiring (not included in the thin-film coil module of the present invention) has a matrix corresponding to the front and back surfaces, and wiring having solder bumps 4c and 4d at the ends. The thin film coil array 1, the ceramic substrate 2 and the diode array 3 are bonded together to form a thin film coil module in which the circuit shown in FIG. 4 is formed. The flexible printed circuit board 4 for wiring may be connected later. FIG. 6 shows only one coil and a diode portion of a conventional thin film coil module, (a) is a plan view of the coil, and (b) is a sectional view taken along line XX in (a). In the conventional thin-film coil module, the thin-film coil C is embedded in the insulating layer 1p made of polyimide formed on the ceramic substrate 2.
Is formed, and is connected to the diode D 1 by a connection wiring 2e passing through a through hole provided at the central end of the coil C 1. With such a configuration, the heat generated in the thin film coil is diffused to the ceramic substrate to cool the coil.

[0005]

A thin film coil array in which the size of the thin film coil is several .mu.m to several tens .mu.m can be generally manufactured by using a photo process. For example, a coil can be manufactured relatively easily by combining a photo process using a photosensitive polyimide resin and a copper plating process. By using a polyimide resin, it is possible to increase the space factor by utilizing the heat shrinkability during curing, and to drive a large current by taking advantage of the high heat resistance temperature of about 400 ° C.

In order to improve the heat dissipation of the coil, there is a method of forming the coil directly on the ceramic substrate, but since the ceramic is a sintered body, the surface irregularities are large, and the copper coil pattern is directly formed at a pitch of several μm. Is difficult to form. Therefore, a conductor pattern is formed on the surface that is flattened by spin-coating a polyimide resin with a thickness of about 10 μm. For example, when a thin-film coil having a cross-sectional dimension of 20 μm × 7 μm and 17 turns is formed, the resistance value of the thin-film coil having an area of 1 mm ² is about 4 Ω. If the drive current is 1 A, the power is
It becomes 4W. On the other hand, the thermal conductivity of polyimide resin is about 0.2 W / m.
Since it is as small as / K, the thermal resistance up to the ceramic substrate is about 50K /
It was as large as W, and the average temperature rise of the entire coil was as high as 300 ° C.

It is an object of the present invention to provide a thin film coil module which has excellent heat dissipation characteristics and can therefore carry a large current, and a method of manufacturing and using the same.

[0008]

In order to achieve the object of the present invention, thin-film coils are embedded in a coil insulating member in an insulated, matrix arrangement, and at least one end of each thin-film coil is a coil. The thin film coil array connected to the connection terminals provided on the surface of the insulating member, and the diodes are arranged in a matrix in synchronization with the matrix arrangement of the thin film coils,
The diodes synchronized with the column arrangement of the thin-film coils are connected to the common wiring of the column arrangement, and the diode array insulated between the row arrangements sandwiches a heat sink made of a highly heat-conductive material, and is connected to the connection terminals of each coil. In the thin film coil module in which the respective diodes facing each other are connected by the connection wiring passing through the through hole of the heat sink, the coil insulating member is made of a diamond thin film.

A gap may be provided between the thin film coil array and the heat sink plate. It is preferable that the gap is formed by being separated by a metal bump interposed between the thin film coil array and the heat sink plate. The voids are preferably filled with an adhesive having high thermal conductivity.

The high thermal conductivity adhesive preferably contains diamond or silicon carbide powder. In the method for manufacturing the thin film coil module, a thin film coil, a diamond substrate covering the thin film coil, a silicon substrate on which a thin film coil array including the connection terminals is formed, and a connection wiring passing through the through hole are provided. The silicon substrate may be removed after joining the ceramic substrate, the connection terminals of the thin film coil array and the connection wiring of the ceramic substrate.

The metal bumps may be formed on the connection terminals of the thin film coil array. In the method of using the thin-film coil module, it is preferable that a heating medium be circulated in the gap. The heat medium is preferably water or freon gas. A diamond thin film with excellent thermal conductivity is used as the insulating material for the thin film coil. High cooling effect can be expected by converting the insulating material to diamond. Furthermore, a gap is provided between the diamond and the ceramic substrate, and this gap is cooled by a liquid, which enables efficient cooling.

[0012]

FIG. 1 shows only one coil and a diode portion of a thin film coil module according to the present invention,
(A) is a top view of a coil, (b) is a XX sectional view in (a). Since the structure of the thin film coil module is the same as the conventional one (see FIGS. 5 and 6), only the improved portion will be described.

The coil insulating member for covering the thin film coil C of the thin film coil array 1 is changed to a diamond thin film 1i instead of the conventional polyimide resin. Ceramic substrate 2
The diode array 3 and the diode array 3 have the same configuration as the conventional one. The thermal conductivity of diamond used for coating thin film coils is 1000 W /
Since it is as large as m / K, the thermal resistance can be reduced to about 1/5000 compared with conventional polyimide. Therefore, a large current can be applied.

FIG. 2 shows only one coil and diode part of another thin-film coil module according to the present invention, (a)
Is a plan view of the coil, and (b) is a sectional view taken along line XX in (a). The change from FIG. 1 is that the ceramic substrate 2
The point is that a gap G is formed between the thin film coil array 1 and the thin film coil array 1. By filling this gap G with a highly heat-conductive adhesive containing diamond powder or silicon carbide powder (also serving as adhesion), the thin-film coil array 1
The heat transfer between the ceramic substrate 2 and the ceramic substrate 2 can be enhanced.

Alternatively, a large current can be applied to the thin film coil by circulating a heat medium such as water or chlorofluorocarbon in the gap G for cooling. Hereinafter, a method of manufacturing a thin film coil module having a gap will be described by way of examples. Example 1 FIG. 3 is a cross-sectional view along the manufacturing process of a thin film coil module using a diamond thin film according to the present invention. The drawing numbers and the process numbers described below are matched.

(A) Rim etching A silicon wafer is used for manufacturing the thin film coil array.
When a diamond thin film is grown on a silicon wafer by microwave plasma CVD, the edge becomes high and the photo process becomes difficult due to the high growth rate at the edge of the wafer. To avoid this, a diamond thin film growth substrate, a silicon wafer with a diameter of 2 inches and a thickness of 3.2 m (0.125 inches), was rim-etched with a width of 5 mm at the outer peripheral portion of the wafer using a mixed solution of hydrofluoric and nitric acid by about 30 μ. A silicon wafer 11 was obtained. (b) The diamond thin film-forming rim-etched silicon wafer 11 was subjected to ultrasonic nucleation treatment for 30 minutes in a diamond abrasive grain-dispersed alcohol suspension having a particle size of 1 μm. Next, a polycrystalline diamond thin film 12 having a thickness of 10 μm was deposited using a diamond thin film forming apparatus. The film forming parameters were methane concentration 2%, substrate temperature 940 ° C., atmospheric pressure 14.7 kPa, and growth time 5 hours. (c) Plated seed layer deposition Copper was deposited to deposit a plated seed layer 13 having a thickness of 1 μm. (d) A negative photosensitive polyimide resin on the coil pattern forming plating seed layer 13.
(Asahi Kasei: G-7613N) was used to form the coil mold 14. Coil width (coil groove width) 20 μm, pitch 25 μm, height
It was 6.5 μm. (e) The coil forming diamond die is entirely coated with copper and then polished to form copper only in the groove portion of the coil die. In this example, copper was plated using a plating solution of a copper borofluoride bath. The energizing current was 0.1 A and the energizing time was 10 min. The groove of the coil was filled with copper to form the coil main portion 15. (f) Removal of polyimide Processed using oxygen ion beam etching. The polyimide coil mold was removed by etching at a beam energy of 400 eV and a current density of 1.1 A / cm ² for 80 minutes. (g) Seed layer removal was continued, and processing was performed using argon ion beam etching. Beam energy 1.0 keV, current density 1.1 A / cm ²
The entire surface was irradiated for 15 minutes, the seed layer between the coils was removed, and a coil C composed of the coil main portion 15 and the remaining portion of the plating seed layer 13 below it was formed. (h) Preparation of Interlayer Insulating Diamond Thin Film First, a diamond thin film deposition apparatus was used to deposit a diamond thin film for coil insulation. A diamond thin film was grown for 3 hours under the film forming conditions of a methane concentration of 2%, a substrate temperature of 740 ° C. and an atmospheric pressure of 14.7 kPa. Thus, coil C
It was possible to embed the diamond only in the gap.

Next, a diamond thin film forming device was used to deposit a diamond thin film for insulating coating of the coil. Carbonization treatment was performed under the film forming conditions of 10% methane concentration, 270 Pa atmosphere pressure, and 3 hours to form diamond core on copper. Continuously, methane concentration 2%, substrate temperature 830 ℃, atmospheric pressure 1
The diamond thin film was grown for 3 hours under the condition of 4.7 kPa. The mixed surface of copper and diamond could be completely covered with the diamond thin film 16. Diamond thin film
The surface of 16 had irregularities, and in particular, a protrusion of about 30 μm was generated near the boundary between the coil and the diamond. (i) Surface flattening Since the above-mentioned projections (unevenness) are not suitable for the photolithography of the next step or bonding to the surface of the ceramic substrate, they need to be flattened. 16 diamond thin film by vacuum thermal polishing
Surface was flattened. Pure iron plate heated at a temperature of 940 ℃,
It was pressed against the diamond surface with a pressure of 5 kPa and polished for 20 hours. As a result, the protrusions of about 30 μm were removed by polishing,
A surface roughness of 3 μm was obtained. The coil coating material covers the entire area of the diamond that covers the coil C and insulates between the coils.
1i. (j) A thickness of 1 is obtained by vapor deposition on the diamond thin film 16 after through hole formation polishing.
A μm aluminum (Al) film was deposited, and a pattern for a through hole (contact hole) of photosensitive polyimide was formed thereon. The Al film in the through hole was removed by wet etching.
Then, oxygen ion beam etching is performed, the beam energy is 400 eV, and the current density is 1.1 A / cm ² for 3 h.
Through hole 1H that reaches the surface of coil C in diamond thin film 16
Was formed. The etching selection ratio to Al was about 18. (k) Electrode terminal formation Copper plating is performed using a plating solution of copper borofluoride bath, the contact holes are filled with copper to form leads 1e, and further, the ceramic substrate (2b in the next figure (l)) and thin film coil array 1
A bump 1b (also serving as an electrode terminal) for forming a gap between and is provided. Energizing current is 0.1A, energizing time is about 30min
A bump 1b having a thickness of 20 μm was obtained. The thin film coil array 1 includes a coil C, a coil covering member 1i, leads 1e and electrode terminals.
It consists of 1b. (l) Board bonding Separately, 20 μm of lead is added to the ceramic board 2b with a through hole.
A heat sink 2 having a connection wiring 2e that has been plated with m and filled in the through hole has been prepared, and the thin-film coil array 1 that has been subjected to the above steps is overlaid and bonded at a heating temperature of 300 ° C for a heating time of 1 min. It was Gap thickness is copper bump 1b
Since it is specified by the thickness of, it becomes 20 μm. (m) Silicon substrate removal Adhesive is applied to the gap in order to protect the electrodes in the following steps, and first, using a diamond saw,
A 3 mm substrate was cut to leave a thickness of 500 μm. Then, after polishing to a thickness of 100 μm using a diamond lap plate, the silicon substrate was dissolved and removed using a heated potassium hydroxide solution. After that, ultrasonic cleaning was performed in an organic solvent to remove the adhesive between the gaps. (n) The protrusion T 2 on the outer peripheral portion of the shaped thin film coil array 1 was polished and removed.

A connection wiring penetrating the electrode of the diode array 3 and the heat sink 2 which are separately manufactured, to the thin film coil array 1 and the heat sink 2 formed by the above process.
The thin film coil module shown in Fig. 2 was obtained by heating and bonding 2e and connecting to diode element D. As described above, since the thin film coil array and the silicon substrate are bonded to each other while the thin film coil array and the heat sink 2 are bonded together, the silicon substrate acts as a reinforcing material for the thin film coil array, and the thin film coil array during the process is processed. No more damage.

The thin film coil module using the diamond thin film obtained through the above steps was evaluated as follows. The main factor that determines the performance of an electromagnetic actuator is the electromagnetic force that can be generated. Since the electromagnetic force is expressed by the product of the current and the number of windings, the relationship between the applied power and the coil temperature rise was investigated.
Since the time constant of the thin-film coil was about 10 ms, a stable current with a pulse width of about 100 ms was applied, and the temperature rise of the thin-film coil was estimated from the change in its resistance.

When the temperature rise was set to 40 ° C., the power input to the conventional polyimide insulating thin film coil module was 0.55 W. On the other hand, in the diamond-insulated thin film coil module according to the present invention, even when the gap is air-cooled.
It turns out that 11W and 20 times the electromagnetic force can be obtained. Also, when the gap is water-cooled, due to the specification limit of the drive circuit, 40 ℃
We could not reach the temperature rise, but the input power was 72W
It was found that the temperature rise could be suppressed to 20 ° C or less by (already 130 times electromagnetic force). Example 2 (l) In the substrate bonding step (l) of Example 1, an epoxy resin mixed with diamond powder was applied between the bumps of the ceramic substrate, and the thin film coil array 1 was superposed and bonded.

When the temperature rise is 40 ° C, the input power is 30W
It was confirmed that the high thermal conductive adhesion is effective.

[0022]

According to the present invention, a thin film coil array in which thin film coils are two-dimensionally arranged in a matrix in a coil insulating member and embedded, and diodes are arranged in a matrix in synchronization with the matrix arrangement of the thin film coils. Since the diode array uses a diamond thin film as the coil insulating member of the thin film coil module that sandwiches a heat sink made of a high thermal conductive material, the high thermal conductivity of diamond drastically reduces the thermal resistance between the thin film coil and the heat sink. It has become possible to increase the power input to the.

Further, since the air gap (gap) is formed between the thin film coil array and the heat sink, the heat medium can be circulated in the gap to cool the coil, further increasing the electric power supplied to the coil. I was able to do it. Further, since the thin film coil array and the silicon substrate to which the thin film coil is attached are bonded to the thin film coil array and the heat sink as they are, the silicon substrate acts as a reinforcing material for the thin film coil array, and No damage occurs and the manufacturing method yield is improved.

[Brief description of drawings]

1 shows only one coil and a diode portion of a thin-film coil module according to the present invention, (a) is a plan view of the coil, and (b) is a sectional view taken along line XX in (a).

FIG. 2 shows only one coil and a diode part of another thin film coil module according to the present invention, (a) is a plan view of the coil, and (b) is a XX sectional view in (a).

FIG. 3 is a cross-sectional view along a manufacturing process of a thin film coil module using the diamond thin film according to the present invention.

FIG. 4 is an equivalent circuit of a two-dimensionally arranged thin film coil module.

FIG. 5 is a perspective view of main components of a conventional thin film coil module.

FIG. 6 shows only one coil and a diode part of a conventional thin film coil module, (a) is a plan view of the coil, and (b) is a XX sectional view in (a).

[Explanation of symbols]

1 Thin film coil array 11 Silicon substrate 12 First diamond thin film 13 Plating seed layer 14 coil type (photosensitive resin) 15 Copper plating layer 16 Second diamond thin film 1i coil insulation material 1p coil insulation material (polyimide) 1h through hole 1e connection terminal / metal bump 2 heat sink 2b ceramic substrate 2e connection wiring 3 diode array 3e electrode 4 Flexible printed circuit board 4c solder bump 4d solder bump C thin film coil D diode G gap Lc coil (row) common wiring Ld diode (column) common wiring

Claims (9)

[Claims] 1. A thin film coil is insulated from one another in a coil insulating member, is arranged in a matrix and is embedded, and at least one end of each thin film coil is connected to a connection terminal provided on the surface of the coil insulating member. The thin film coil array and the diodes are arranged in a matrix in synchronization with the matrix arrangement of the thin film coils, and the diodes synchronized with the column arrangement of the thin film coils are connected to the common wiring in the column arrangement, and the row array is insulated from each other. In a thin film coil module in which a heat sink made of a high thermal conductive material is sandwiched, and the connection terminals of each coil and each of the opposing diodes are connected by a connection wiring that passes through a through hole of the heat sink. A thin-film coil module, which is made of a thin film. 2. A thin film coil module having a gap between the thin film coil array and the heat sink plate. 3. The thin film coil module according to claim 2, wherein the voids are formed by being separated by metal bumps interposed between the thin film coil array and the heat sink plate. 4. The thin film coil module according to claim 2, wherein the void is filled with an adhesive having high thermal conductivity. 5. The thin-film coil module according to claim 2, wherein the high thermal conductive adhesive contains diamond or silicon carbide powder. 6. A silicon substrate on which a thin film coil array comprising the thin film coil, the diamond thin film covering the thin film coil, and the connection terminals is formed, a ceramic substrate having connection wirings passing through the through holes, and the thin film coil. The method for manufacturing a thin film coil module according to claim 1, wherein the silicon substrate is removed after joining the connection terminals of the array and the connection wiring of the ceramic substrate. 7. The method of manufacturing a thin film coil module according to claim 4, wherein the metal bump is formed on a connection terminal of the thin film coil array. 8. The method of using the thin film coil module according to claim 2, wherein a heat medium is circulated in the gap. 9. The method of using a thin-film coil module according to claim 8, wherein the heat medium is water or CFC gas.