JPH11330885A - Band-pass filter and manufacture of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact, light, and low-height band-pass filter using a thin film inductor with a small occupancy area and superior characteristics. SOLUTION: In this discrete thin film band-pass filter, a monolithic thin film structure is obtained by arraying a thin film inductor array 1 formed by gathering 6 thin film inductors, having magnetic cores on a thin film capacitor array 2 formed by gathering 12 thin film capacitors on a ceramic substrate 3 which is a pedestal at which 4 through-holes 5 are provided at the end parts of opposite sides and a conductor pattern, including 4 electrodes 6 in the surrounding of the through-holes 5 and 12 conductive electrodes 4 in the periphery of the center. This filter is constituted independent of a jointing technique required for the existing device, and mounting equipment or mounting process is not required, and this filter can be made compact and light by sharply reducing the height, and manufactured at low cost with a small occupancy area and superior characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mainly used as a filter for input / output signals in a cellular phone or the like, and a band pass filter (BPF) as an LC magnetic device having a monolithic thin film structure including a thin film inductor and a thin film capacitor. It relates to the manufacturing method.

[0002]

2. Description of the Related Art Conventionally, this type of bandpass filter has
The mainstream is a SAW (surface acoustic wave) type having a relatively high Q value of several hundreds and a dielectric type having a Q value of several tens to several hundreds. These two filters are effective in an applied frequency band of several hundred MHz to several GHz, and obtain a transmission frequency band having a narrow frequency band and a sharp rise to show a high Q value. On the other hand, the low frequency band is a weak area, and it is difficult to obtain a wide transmission frequency bandwidth.

[0003] The shape of these filters depends on the frequency band to be used, but for a SAW type filter, for example, the dimensions are 3.8 mm long x 3.8 mm wide x 2 mm thick.
While it is possible to make a small and thin surface mount component (SMD) package of about 3 mm, the dielectric type is manufactured by sintering, and its thickness is 3 to 4 mm due to its essential characteristics. A degree is needed.

When these filters are formed, SAW
In the case of the type, an aluminum comb-shaped electrode is arranged by the same technology as that for manufacturing a semiconductor element on a dielectric ceramic, and a metal or ceramic made of metal or ceramics so as not to hinder the protection of the surface state and the propagation of surface vibration waves. Although it is necessary to cover with a cover, in the case of a dielectric type, a ceramic resonator and L, C chip elements are arranged on a substrate.

[0005] Incidentally, in the case of a dielectric type band-pass filter, an LC lumped constant type is designed due to the configuration of the electric circuit, and the inductor used here is several m.
The main types are a bulk type in which a ferrite of m is wound, a chip element type in which a coil is embedded in a ferrite, and an air-core coil that does not use a magnetic material. These inductors have L in the high frequency band of several tens MHz to several hundred MHz.
When the value is large, the Q value is small because the resonance frequency is low. Conversely, when the L value is small, the resonance frequency is high, but because the L value is small, the Q value is small. In addition, a chip capacitor element, which is a surface mount component, is mainly used for a capacitor which is a component for a chip inductor.
0.8mm for 8 type, 0.5m for 1005 type
m. These chip capacitor elements have an efficiency of several
00, which is a standard, with the capacitance characteristics being determined by 100% screening.

On the other hand, when a thin film LC filter is manufactured, a copper coil is formed on a substrate made of glass, ceramics, Si or the like by a sputtering method or a plating method, and then a sputtering method using a metal target and an insulator target is performed. A semiconductor element is formed by forming a magnetic thin film, forming a resist pattern with a thickness of several μm by exposure using a photomask, forming a magnetic layer or conductor, and then processing using a lift-off method. The same process is applied as in the case where

Incidentally, a thin-film inductor made of a thin-film soft magnetic material has a low Q value, and is not applied to a thin-film bandpass filter.

[0008]

In the case of the above-mentioned dielectric type bandpass filter, the driving frequency is several tens of MHz.
In the ~ 100 MHz band, effective Q value cannot be obtained, the characteristics such as insertion loss and bandwidth are inferior to SAW filters, and the size of inductor is large despite the miniaturization due to higher frequency. Because the thickness of itself does not become thin,
Not only is there a problem that there is a limit to miniaturization of the device shape, but if the number of L and C chip elements increases, the area also increases, the price cannot be expected to be low, and there is no competitiveness with other elements. Due to various problems such as the above, the chances of adopting L and C lumped constant types in recent surface mount components tend to decrease. In the case of 1608 type and 1005 type chip capacitor elements, although the components themselves are small, an electrode portion for mounting the chip components is required, and furthermore, the chips cannot be extremely close to each other from the handling of the chip components, so that the size is reduced. And it is not suitable for area saving.

On the other hand, a thin-film inductor is not used in a bandpass filter. This is because the Q value of a thin-film soft magnetic material is low. The Q value of the soft magnetic material is represented by μ ′ (real part of magnetic permeability) / μ ″ (imaginary part of magnetic permeability), and the Q value of the inductor is ωL / R (where ω = 2πf: R is a resistance), and the Q value as a bandpass filter is proportional to ω, L and μ ′, and R and μ ″
Is inversely proportional to The loss of the soft magnetic material is determined by the precession motion of the magnetic spin, and the spin motion is essentially lost. Therefore, it is indispensable to reduce the resistance R in order to improve the Q value.

However, since the inductance is obtained by inserting a magnetic material into the coil due to the structure of the inductor, the loss of the magnetic material (iron loss) and the copper loss of the coil (DC loss and AC loss) are reduced. We have to reduce both,
The Q value of the prototype obtained so far is around 20 at the maximum.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its technical object a small, lightweight, low-profile bandpass filter using a thin film inductor and having excellent characteristics with a small occupying area. And a method for manufacturing the same.

[0012]

According to the present invention, several thin film capacitors having a magnetic core are assembled on a thin film capacitor array formed by assembling several thin film capacitors on a substrate serving as a base. A bandpass filter having a monolithic thin film structure provided with the thin film inductor array provided is obtained.

In this band-pass filter, the thin-film inductor array is arranged directly above the thin-film capacitor array, and furthermore, the operating frequency band is 10 MHz to 10 MHz.
Preferably, it is in the range of 500 MHz.

On the other hand, according to the present invention, a thin film capacitor array forming step of forming a thin film capacitor array by assembling several thin film capacitors on a substrate serving as a pedestal;
A method of forming a thin-film inductor array in which several thin-film inductors each having a magnetic core are assembled on a thin-film capacitor array to form a thin-film inductor array.

In the method of manufacturing a bandpass filter, in the step of forming the thin-film inductor array, it is preferable that the thin-film inductor array is disposed directly above the thin-film capacitor array.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows an equivalent circuit of a discrete thin-film bandpass filter according to one embodiment of the present invention. This equivalent circuit includes six spiral type thin film inductors L1 to L6 formed on a substrate serving as a pedestal to form a monolithic thin film structure and twelve overlay type thin film capacitors C1 to C12.
And two resistors R1 and R2 each having a resistance value of, for example, or 210Ω, and the LC circuit has a six-stage configuration. In this equivalent circuit, the inductor chip element comprises a thin film inductor array 1 as shown in FIG. 2, and the capacitor chip element comprises a thin film capacitor array 2 as shown in FIG.

The thin-film inductor array 1 has a width of 5
The thin film inductors L1 to L6 are formed by winding conductors in a spiral shape so that portions of 400 μm are exposed from both ends of a thin film magnetic core having a length of 00 μm and a length of 3700 μm. They are juxtaposed on the substrate so as to be aligned in the direction. That is, the thin-film inductor array 1 here is manufactured by collectively disposing the thin-film inductors L1 to L6 each having a magnetic core, and this assembly makes it possible to form a large inductor with a small area. Therefore, not only high efficiency can be obtained with high inductance, but also the thin film inductors L1 to L1
As compared with the case where L6s are manufactured individually, the labor and time required for mounting and cutting time are simplified, which is advantageous in terms of cost. Further, since the thin film inductors L1 to L6 here are arranged and manufactured at a low temperature, the structure of the thin film capacitor array 2 already formed on the substrate, which will be described later, can be formed without destruction by heat or the like. Is suitable for configuring a band-pass filter of FIG.

By the way, when the occupied area used in the case where a bandpass filter is formed by using such a thin-film inductor array 1 and in the case where a bandpass filter is formed using an existing chip inductor element are compared, Dimensions are 500 μm wide and 1600 μm long
When using the thin film inductor array 1 of
When the configuration is such that 10 pieces are arranged side by side, the total area S becomes S =
8.8 mm ² , which makes it possible to put ten inductor elements in an area of 1.6 mm × 5.5 mm, whereas when a chip inductor element is used, the element dimensions are 1600 μm × 800 μm, and the width of the solder land increases by 100 μm for soldering by SMT technology, and the length increases by 200 μm in addition to
Since the solder lands must be separated by at least 200 μm or more in order to facilitate handling according to the inclination of the element at the time of mounting, the total area S is 23.8 mm ² , and the mounting area is 2 mm × 12 mm. It occupies an area, and as a result, it is 2.7 parts to be configured using a chip inductor element.
It turned out that a twice as large area was necessary. Therefore, if an array element such as the thin-film inductor array 1 is used, it is effective to reduce the size of the filter.

On the other hand, the thin film capacitor array 2 has 12 conductor electrodes around the center, a ground (GND) location at one corner,
And a signal pattern (Signal) at one end of the opposite side.
Vertical 500 provided with a conductor pattern including -1, -2)
By applying a strip-shaped conductor pattern to a conductive portion on a substrate of 0 μm × 5000 μm in width, thin film capacitors C1 to C12 are collectively formed between the strip-shaped conductor patterns, thereby producing a thin film capacitor. The thin-film capacitor array 2 serves as a pedestal on which the thin-film capacitors C1 to C12 and the thin-film inductors L1 to L6 are mounted, in addition to being a solder-bonded board stage at the time of mounting. In the case of the thin-film capacitor array 2, as in the case of the thin-film inductor array 1, assembly labor and cutting time can be simplified by collective production, which is advantageous in terms of cost.

In a discrete thin film band-pass filter having a monolithic thin film structure in which the thin film inductor array 1 and the thin film capacitor array 2 are formed on a substrate, the total thickness of each array element and the substrate is 250 μm.
It is as thin as m to 300 μm, and can be arranged above, below, and around semiconductor elements and power supply elements.

Therefore, when a discrete thin film bandpass filter is constructed, as shown in FIG. 4, four through-holes 5 are provided at one end of one side facing each other, and four through-holes around the through-hole 5 are provided. The thin film capacitors C1 to C12 are formed on a ceramic substrate 3 on which a conductor pattern including the electrode 6 and the twelve conductor electrodes 4 at the central periphery is provided.
It is sufficient to arrange a thin-film inductor array 1 formed by assembling thin-film inductors L1 to L6 each having a magnetic core on a thin-film capacitor array 2 formed by assembling to form a monolithic thin-film structure. Figure 1
Is the same as the case shown in FIG.

By the way, the existing mounting element constitutes a device by using a surface mounting part technology and various bonding technologies, and the bonding method is a new technology other than soldering using a gold bonding wire. It is possible to perform thermocompression bonding using solder balls (containing copper nuclei) or ultrasonic thermocompression bonding using gold bumps, which is a technology under development, to perform pressure bonding. Since this is configured irrespective of such a joining technique, mounting equipment and a mounting process are not required, and it can be manufactured at a low cost as a small, lightweight, low-profile and excellent characteristic with a small occupying area.

Incidentally, the mounting height (height) of the discrete thin film bandpass filter having the monolithic thin film structure and the bandpass filter formed by using the existing chip inductor element and the 1608 type or 1005 type capacitor element. When the monolithic thin film structure was used, the thickness of the ceramic substrate 3 was 200 μm.
m, the thickness of the thin film capacitor array 2 is 15 μm, and the thickness of the thin film inductor array 1 is 15 to 70 μm.
While the overall thickness is within 230-300 μm,
In the case of the existing configuration, when a PC board is used, the thickness is 500 to 1000 μm, and the thickness of the mounting board is 2 μm.
Even if the thickness is 00 μm, the thickness of the electrode is 5 μm, the thickness of the solder is 30 to 50 μm, and the thickness of the chip inductor element is 800 μm at the maximum, so that the overall thickness does not become 1 mm or less, and as a result, the monolithic thin film In the case of the structure, the thickness is one third that of the existing structure, and the height is sufficiently low.

When manufacturing such a discrete thin film bandpass filter, a thin film capacitor array forming step of forming a thin film capacitor array 2 by assembling thin film capacitors C1 to C12 on a ceramic substrate 3 serving as a base. And a thin-film inductor array forming step of assembling the thin-film inductors L1 to L6 each having a magnetic core on the thin-film capacitor array 2 to arrange and form the thin-film inductor array 1. In the thin-film inductor array forming step, the thin-film inductor array 1 is formed. May be arranged directly above the thin-film capacitor array 2.

More specifically, first, a 200 μm-thick ceramic substrate 3 (alumina substrate, silicon substrate or the like) which has been subjected to a surface oxidation treatment is prepared, and a thin film capacitor array forming step is performed on the ceramic substrate 3. After assembling the thin film capacitors C1 to C12 of the overlay type as shown in FIG. 3 to form a thin film capacitor array 2, an insulating layer is formed on the electrodes. Next, a helical type thin film inductor L1 to L6 as shown in FIG.
Are assembled to form a thin-film inductor array 1.
In this state, the upper thin-film inductors L1 to L6 and the lower thin-film capacitors C1 to C12 are electrically connected to each other through the electrodes.

However, during these steps, a hole is formed in the ceramics substrate 3 with a laser processing machine to form a through hole 5, and thereafter an electrode 6 is formed around the hole. At this time, a conductor such as copper is formed from above and below the ceramic substrate 3, and a conductor is formed on the side wall of the through-hole 5 by the shadow effect by using the wraparound of plasma at the time of sputter deposition to short-circuit the upper and lower sides. To do. The reason why the thickness of the ceramic substrate 3 is set to 200 μm is to effectively use the shadow effect. However, it has been considered that if the thickness is large, it is difficult to short-circuit the upper and lower portions, and if the thickness is small, the strength is reduced. by.

In this manner, a compact, small-sized, low-profile discrete film bandpass filter having an operating frequency band in the range of 10 MHz to 500 MHz can be constructed.

FIG. 5 shows the attenuation (d) with respect to the frequency (MHz) in the discrete thin-film bandpass filter.
B) The results of measuring the characteristics (filter characteristics) are shown in comparison with those of the simulation results. FIG.
From the thin-film inductor L1 having a Q value of 18 indicated by a solid line.
It can be seen that the measurement results of the attenuation characteristics of the discrete thin-film bandpass filter including the thin-film inductor array 1 having L6 through L6 are in good agreement with the simulation results of the Q value 18 indicated by the dotted line.

FIG. 6 shows an attenuation (dB) characteristic with respect to frequency (MHz) in a filter including the thin-film inductor array 1 having the thin-film inductors L1 to L6 having different Q values 30 in the discrete thin-film band-pass filter of FIG. (Filter characteristics) are shown in comparison with those of FIG. 5 and those of the existing SAW type. From FIG. 6, the insertion loss when using the thin-film inductors L1 to L6 having a Q value of 30 shown by the dotted line is smaller than that using the Q value of 18 shown by the solid line, and is indicated by the broken line. It can be seen that the same characteristics can be obtained as compared with the SAW type shown, and that the frequency band is further extended. Further, in the case of a band pass filter having a monolithic thin film structure, the thickness is 300 μm, which is 15% smaller than that of the SAW type filter having a thickness of 2 mm, which is advantageous in terms of shape.

Incidentally, the Q value of the thin-film inductors L1 to L6 was about 20 before, but can be increased to about 30 recently. The condition for setting the Q value to 30 at about 100 MHz can be realized by reducing the loss of the magnetic material by 8/9 and reducing the DC and AC copper loss caused by the coil by 3/4. In order to reduce these, in the case of a magnetic material, it is only necessary to perform a composite multilayer in which the insulating layer of the multilayer film is partially thickened.In the case of a copper coil conductor, the DC resistance can be reduced by increasing the thickness of the conductor, and Dividing the conductor thickness into multiple layers by the insulating layer can reduce AC eddy current loss. As a result, loss at 100 MHz can be reduced, and a Q value of 30 or more can be obtained.

The number of the thin film inductors L1 to L6 of the thin film inductor array 1 and the thin film capacitors C1 to C12 of the thin film capacitor array 2 and the resistors R1 and R2 in the equivalent circuit in the discrete thin film bandpass filter according to the above-described embodiment. The number is not limited to this, and can be changed depending on the application and design.

[0033]

As described above, according to the bandpass filter of the present invention, a thin film inductor having a magnetic core is formed on a thin film capacitor array formed by assembling several thin film capacitors on a substrate serving as a base. By adopting a configuration in which a thin-film inductor array formed by assembling several devices is deployed, it can be configured regardless of the bonding technology as in the case of existing devices at the time of fabrication, and the mounting equipment and mounting process are not required. Since the elements can be formed in the same process after extremely reducing the number of elements, the yield of each element is improved, and the band-pass filter of a monolithic thin film structure having a small size, light weight, remarkably low profile and a small occupation area is simplified, and the cost is reduced. It can be manufactured with. As a result, the total thickness is 300
Since an extremely thin height of about μm is realized, it can be inserted into an IC card or the like, which is difficult with existing products, and can be applied to a card-type device. In addition, if a thin film inductor having a Q value exceeding 30 is used, the filter characteristics can be assured with an insertion loss equivalent to that of the existing SAW type, and the frequency band is extended to obtain excellent characteristics. Taking advantage of the advantages of cost and shape as compared with that of the semiconductor device, the semiconductor device and the power supply device can be arranged above and below and around the semiconductor device, thereby contributing to thinning and miniaturization of the device. Become like

[Brief description of the drawings]

FIG. 1 shows an equivalent circuit of a discrete thin-film bandpass filter according to one embodiment of the present invention.

FIG. 2 is a plan view showing a detailed configuration of a thin film inductor array used in the discrete thin film band pass filter shown in FIG.

FIG. 3 is a plan view showing a detailed configuration of a thin film capacitor array used in the discrete thin film band pass filter shown in FIG.

4 is a perspective view showing an external configuration of a discrete thin film bandpass filter manufactured as a monolithic thin film structure by applying the structure of the thin film inductor array shown in FIG. 2 and the thin film capacitor array shown in FIG.

FIG. 5 shows a result of measuring an attenuation characteristic (filter characteristic) with respect to frequency in the discrete thin film band-pass filter shown in FIG. 4, in comparison with a result of simulation.

6 is a graph showing a result of measuring an attenuation characteristic (filter characteristic) with respect to frequency in a filter including a thin-film inductor array having thin-film inductors having different Q values in the discrete thin-film band-pass filter of FIG. 5;
And in comparison with the existing SAW type.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thin-film inductor array 2 Thin-film capacitor array 3 Ceramic substrate 4 Conductor electrode 5 Through-hole 6 Electrode C1-C12 Thin-film capacitor L1-L6 Thin-film inductor R1, R2 Resistance

Claims (5)

[Claims] 1. A thin-film inductor array formed by assembling several thin-film inductors having a magnetic core on a thin-film capacitor array formed by assembling several thin-film capacitors on a substrate serving as a base. A band-pass filter having a monolithic thin film structure. 2. The band-pass filter according to claim 1, wherein said thin-film inductor array is disposed right above said thin-film capacitor array. 3. The band-pass filter according to claim 1, wherein an operating frequency band is 10 MHz to 500 MHz.
A band-pass filter having a range of z. 4. A thin film capacitor array forming step of forming a thin film capacitor array by forming several thin film capacitors on a substrate serving as a base, and collecting some thin film inductors having a magnetic core on the thin film capacitor array. Forming a thin-film inductor array to form a thin-film inductor array. 5. The method of manufacturing a band-pass filter according to claim 4, wherein in the step of forming the thin-film inductor array, the thin-film inductor array is disposed right above the thin-film capacitor array. Production method.