JP3308260B2 - Integrated circuit with EMI filter element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an integrated circuit (hereinafter referred to as an integrated circuit).
The present invention relates to an IC having a capacitance element (hereinafter, referred to as a decoupling capacitor) added to a pair of lines (plus line, minus line) for supplying DC power to a chip. With a through EMI filter between the decoupling capacitors,
By forming a filter element using a composite magnetic material on the inner lead, a suitable electromagnetic interference noise (hereinafter referred to as EMI) can be obtained.
Abbreviated as above) and an IC with an EMI filter element.

[0002]

2. Description of the Related Art Conventional methods for configuring a line for supplying DC power are roughly classified into the following three methods.

(1) A decoupling capacitor is formed in an IC chip by a semiconductor process (JP-A-6-120).
No. 072). Specifically, as shown in FIG. 11, a capacitor composed of a first electrode 2, an insulating film 3, and a second electrode 4 is formed on an IC chip 1 and used as a decoupling capacitor.

(2) A multilayer ceramic capacitor as a decoupling capacitor is mounted and connected to a lead frame portion having a die pad on which an IC is mounted (Japanese Patent Laid-Open No. 55-10 / 55).
8785, JP-A-59-143355).
Specifically, as shown in FIG. 12, a discrete multilayer ceramic capacitor 7 is mounted and connected between DC power supply lines on a lead frame part 6 with a die pad on which an IC chip 5 is mounted.

(3) A decoupling capacitor is mounted and connected to a printed circuit board on which an IC is mounted, and an inductor is formed and connected to the printed circuit board. Technical report EMCJ97-82 of the Institute of Electronics, Information and Communication Engineers (1997-12). JP-A-10-163636, "Multilayer printed circuit board and manufacturing method thereof". Specifically, as shown in the circuit of FIG. 13, the capacitor 11 is mounted on a printed circuit board on which the IC 10 is mounted.
Are mounted and connected, and as shown in the plan view of FIG. 14A and the cross-sectional view of FIG. Inductor 13
Is formed by connecting a plurality of upper and lower conductor patterns 14 in series around the ferrite layer 16 by via holes 15.

[0006]

However, the disadvantages of the method (1) include an increase in the manufacturing cost due to an increase in the chip area of the IC, and a hindrance to the degree of freedom of design (change of the capacitance of the capacitor, etc.). Can be

The disadvantage of the method (2) is that Z _IC << Z _PS is located between the impedance Z _IC from the decoupling capacitor to the IC side and the impedance Z _PS from the capacitor to the power supply. Is necessary, but it is not always satisfied. The reason why the relationship of Z _IC << Z _PS must be satisfied will be described with reference to FIG.

FIG. 15 shows a decoupling capacitor C₁To
This is a current path model focused on.₁Is IC₁To
Corresponding decoupling capacitor, C₂Is IC₂Compatible with
This is a decoupling capacitor. Loop A is C
₁And IC₁Minimum loop (or C₂And IC₂Made with
IC)₁(Or IC₂) Switch
The high-frequency current generated by the tuning operation is returned. Le
B is C₁And the preceding circuit (in this case, the DC voltage supply
Inn) loop, from the viewpoint of EMI suppression
Is an inherently unnecessary loop. Loop C is C₁And later
Road (in this case, C ₂, IC₂After that, it is included in the electric circuit
From the viewpoint of EMI suppression
Is an inherently unnecessary loop. IC₁(Or IC₂)
The high-frequency current generated by the switching operation of the minimum loop A
Ideally, only the state of reflux is_IC<<<
Z_PSIs not satisfied, the switching operation
The resulting high-frequency current flows widely through the DC power line
(It also flows through loops B and C) and the current path
Is an individual IC₁, IC₂Larger than the current loop of
You. As this loop grows,
The problem is that the level of EMI is high.

Furthermore, a bug point (3), to form an inductor (choke coil) to increase the Z _PS to the printed substrate, to the area of the printed circuit board is increased, the manufacturing cost of the printed circuit board Soaring.

The present invention has been made in view of the above points, and has been made in consideration of the aforementioned Z _IC <
<Allowed to satisfy the relation of _{Z PS,} IC is a source EM
An object of the present invention is to provide an IC with an EMI filter element which can enhance the effect of suppressing I, and in particular, has a high cost performance.

Other objects and novel features of the present invention will be clarified in embodiments described later.

[0012]

In order to achieve the above object, an IC with an EMI filter element according to the present invention comprises an integrated circuit chip and an inner lead pair for supplying DC power, which is connected to the integrated circuit chip. A capacitive element connected therebetween, a composite magnetic body provided around one of the inner lead pairs, and a composite magnetic body provided around the composite magnetic body and electrically connected to the other of the inner lead pairs. A through-type EMI filter having an external electrode and an external electrode, wherein the through-type EMI filter is disposed at a position closer to the outside than a connection point of the capacitance element of the inner lead. And

In the IC with an EMI filter element, a configuration may be employed in which a capacitance element is provided on the IC chip housed in the outer package.

The above-mentioned composite magnetic body is formed by molding a composite material comprising a powder of a ferrite sintered body and a resin binder, or by molding a composite material comprising a powder of a metal magnetic substance and a resin binder. Good.

It is desirable that the periphery of the integrated circuit chip be shielded by a conductor.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an IC with an EMI filter element according to the present invention.

A first embodiment of an IC with an EMI filter element according to the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram (schematic plan sectional view) of the first embodiment, and FIG. 2 shows models focusing on a DC current supply portion of an IC. FIG. 3 is a partial perspective view mainly showing the shield structure according to the first embodiment.

The IC with an EMI filter element shown in FIGS.
In the configuration in which the conductor leads (conductor pins) 25 are respectively connected by bonding wires or the like and housed inside the exterior package 30, the conductor leads (conductor pins) are penetrated between the decoupling capacitor and the DC power supply so as to be cascaded with the decoupling capacitor. A type EMI filter 50 is added inside the outer package 30.

The multilayer chip capacitor 40 as a decoupling capacitor has inner leads (inner pins) 26a, 26b located inside the outer package 30 of the conductor leads 25a, 25b for supplying a direct current.
Mounted and connected between the pair.

The through-type EMI filter 50 is provided with
One of the inner lead pairs (in this example, line V in FIG. 2)_CC
V to be connected to_DDInner lead 26 to be a terminal
a) forming a composite magnetic body 51 around the composite magnetic body
Method such as coating, curing or electroless plating on the outer periphery of 51
The external electrode 52 is provided by
The other of the inner lead pair (in this example, the line GN in FIG. 2)
V to be connected to D _SSInner lead 2 to be a terminal
6b) so that they can be electrically connected to each other.
You.

The feed-through EMI filter 50 is arranged in a cascade connection between the connection point (in this example, the inner leads 26a and 26b) of the multilayer chip capacitor 40 of the inner lead pair and the DC power supply point. . In other words, the feed-through EMI filter 50 is arranged at a position closer to the outside than the connection point of the multilayer chip capacitor 40 of the inner lead 26a. In addition, 25a and 26a are V _DD
, 25b and 26b indicate a conductor lead and an inner lead for Vss, respectively.

The composite magnetic body 51, which is the main element of the penetration type EMI filter 50, is formed by molding a composite material made of ferrite powder or metal magnetic powder and a resin binder so as to surround the inner lead. It will be described later.

The package 30 is made up of the IC chip 2
It is configured by resin molding using a resin mold or the like after the connection of the conductor leads 25 to each other, the connection of the multilayer chip capacitor 40, and the molding of the through-type EMI filter 50.

The periphery of the IC chip 20 is shown in FIGS.
It is surrounded by a conductor shield 55 as shown by a middle dotted line and as shown by oblique lines in FIG. The conductor shield 55 so does not contact the conductor leads other than V _SS terminal to be connected to the line GND, has a shield portion that covers the top and bottom of the IC chip 20, and if there is a side that is not pulled out of the conductor lead, Connect the upper and lower shield parts. And
The conductor shield 55, that is, the upper and lower shield portions are connected to _VSS
It is connected to a conductor lead 25b which is a terminal. Specifically, the conductor shield 55 may be formed on the inside or the outside of the exterior package 30 by using metal foil, conductive paint, electroless plating, or the like.

In the first embodiment, the impedance Z _IC from the decoupling capacitor 40 to the IC chip 20 side and the impedance Z _PS from the capacitor 40 to the power supply (between the line Vcc and GND)
When a comparison is made, the through-type EMI filter 50 is formed between the decoupling capacitor 40 and the line Vcc, so that the relationship of Z _IC << Z _PS is satisfied. In addition, by performing EMI countermeasures by separating zones using a penetration type EMI filter, the effect of reducing EMI can be exhibited.

FIG. 4 illustrates an EMI measure by separating zones using a through-type EMI filter. The functional unit portion of the device is a shield structure, that is, shield 1, and the electronic device zone 1 to the functional unit portion zone 2
EMI filters are mounted on power supply lines, signal lines, control lines, and the like. Further, a method can be adopted in which the zone 3 of the integrated circuit in the zone 2 is shielded by the shield 2 and the above-mentioned power supply line is provided with a through-type EMI filter. In the present embodiment, the IC chip 20 which is the narrowest area as the zone 3 is
This means that the EMI filter 50 is shielded and the through-type EMI filter 50 is disposed, which is excellent even when viewed as an EMI measure by separating the zones.

By configuring the IC with the filter element as described above, the following effects can be obtained.

(1) The current loop formed by the multilayer chip capacitor 40 as a decoupling capacitor and the IC chip 20 can be minimized. Thereby, the loop of the high-frequency current flowing with the switching operation of the IC can be reduced, and the EMI radiated from the loop can be reduced.

(2) The impedance in the IC chip 20 as viewed from the multilayer chip capacitor 40 as the decoupling capacitor can be made lower than the impedance of the DC power supply line as viewed from the capacitor 40, and is formed by the decoupling capacitor and the IC chip 20. The leakage of the high-frequency current from the smallest current loop to another loop can be reduced, and the EMI radiated from the other larger loop can be reduced.

(3) From the above (1) and (2), the IC chip 2
This is effective for stabilizing the DC current supplied to the IC and reducing simultaneous switching noise (sometimes referred to as ΔI noise) of multiple outputs of the buffer IC chip. The effect of suppressing the source EMI can be enhanced.

(4) The area of the printed circuit board does not increase because the area of the IC chip does not increase, the manufacturing cost increases, the degree of freedom in design does not decrease, and no inductor is formed on the device side. The manufacturing cost of the printed circuit board does not increase. Therefore, a high-performance decoupling circuit with good cost performance can be configured.

(5) The through-type EMI filter 50 has a structure in which the outer periphery of the composite magnetic body 51 is surrounded by an external electrode 52.
As compared with an impedance having a structure in which a magnetic material is simply provided in an inner lead, an insertion attenuation amount with respect to noise can be increased.

(6) As is clear from the EMI countermeasure by separating the zones using the through-type EMI filter shown in FIG.
EMI filter 5 that shields and targets
By disposing 0, it is possible to obtain an EMI reduction effect by separating the zones.

A second embodiment of the IC with an EMI filter element according to the present invention will be described with reference to FIGS. FIG. 5 is a configuration diagram (schematic plan sectional view) of the second embodiment, and FIG. 6 shows models focusing on a DC power supply portion of the IC.

[0035] In this case, _{V DD} conductor lead 25a for supplying DC power to the IC chip _20, between _{V SS} conductor lead 25b (in other words, the inner lead 26a, 2
6b), a decoupling capacitor 41 is provided in the IC chip 20. That is, V _DD
Use conductor leads _25a, between the bonding pads 21 on the IC chip _{20 V SS} conductor lead 25b are connected respectively, and a decoupling capacitor 41 is formed in the IC chip by a semiconductor process.

The through-type EMI filter 50 includes inner leads (inner pins) 26a, 26 located inside the outer package 30 of the conductor leads 25a, 25b.
The composite magnetic body 51 is formed around one of the pair b (in this example, the inner lead 26a serving as the _VDD terminal to be connected to the line _VCC in FIG. 6), and is applied to the outer periphery of the composite magnetic body 51. the external electrode 52 by a technique such as curing or electroless plating provided in an external electrode 52 other (this example of the inner lead pair, the V _SS terminal to be connected to the line GND in FIG. 6 inner It is configured to be electrically connected to the lead 26b).

The feed-through EMI filter 50 is arranged in a cascade connection between the connection point of the decoupling capacitor 41 and the DC power supply point (the conductor leads 25a and 25b in this example). In other words, the penetration type E
MI filter 50 is arranged at a position closer to the outside than the connection point of decoupling capacitor 41.

The other structure is the same as that of the first embodiment, and the same or corresponding parts are denoted by the same reference characters.

According to the second embodiment, in addition to the effects of the above-described first embodiment, the decoupling capacitor 41 is formed in the IC chip 20 in advance by a semiconductor process. The step of connecting the capacitor of the component to the inner lead pair can be omitted, the number of manufacturing steps can be reduced, and mass production is excellent.

As described above, the composite magnetic material for forming the feed-through EMI filter 50 on the inner leads 26a and 26b led out as the _VDD terminal and the Vss terminal for supplying DC power to the IC chip is as follows. A composite material obtained by mixing, kneading, and molding a ferrite sintered body powder having a complex relative magnetic permeability (real part μ ′, imaginary part μ ″) as shown in FIG. 7 and a resin binder, as shown in FIG. Mixing and kneading a metal magnetic material powder having a complex relative magnetic permeability and a resin binder,
The composite magnetic material is molded and fixed around the inner lead 26a by a resin molding technique.

In the case of a composite magnetic material molded from a composite material consisting of a ferrite sintered powder and a resin binder, the ferrite sintered material has a high complex relative magnetic permeability at high frequencies.
Zn-based ferrite is suitable. In this case, the Ni-Zn base material is pulverized, and the size of the particles is adjusted to about 30 µm. Examples of the resin binder for molding and fixing the ferrite sintered body powder to the inner lead portion include thermoplastic resins such as polyester, polyphenylene sulfide (abbreviation: PPS), and thermosetting resins such as epoxy and phenol. Resins and the like are suitable. The weight ratio of the ferrite sintered body powder is in the range of 50% to 85% in terms of magnetic properties and moldability. In other words, 50% ferrite sintered powder
If it is less than 85%, the magnetic properties are poor, and if it exceeds 85%, the moldability is impaired.

In the case of a composite magnetic material molded from a composite material composed of a metal magnetic material powder and a resin binder, an Fe—Si system having a large complex relative permeability at a high frequency is suitable. In this case, spherical or flat powder is used as the Fe-Si powder. The diameter of the spherical powder is adjusted to about 50 μm in width, and the dimensions of the flat powder are 50 μm in length and 0.1 μm in thickness.
It is processed to about 3 μm. The same thermoplastic or thermosetting resin as that used for the ferrite sintered body powder described above is used as the binder used for molding and fixing the metal magnetic material powder to the inner lead portion. In this case, the suitable mixing ratio of the metal magnetic powder is 40% to 80% in view of magnetic properties and moldability. That is,
If the metal magnetic material powder is less than 40%, the magnetic properties are inferior.
%, The moldability is impaired.

It should be noted that Mn-Mg based ferrite, Mn-Zn based ferrite and the like can be used in the above-mentioned ferrite sintered body powder.

Similarly, in the case of a powder of a metal magnetic material, Fe-
Naturally, Ni-based, Fe-Al-Si-based or the like can be used.

FIG. 9 is a structural example of the through-type EMI filter 50 shown in the first and second embodiments, and is a conductor lead using a 42 alloy alloy having a thickness of 0.15 mm and a width of 0.4 mm. Around the inner lead 26a, the F is formed so as to have a rectangular cylindrical cross section having a thickness of 1.8 mm, a width of 1.5 mm, and a length of 2.0 mm.
A composite material was prepared by mixing and kneading 80% of the e-Si-based flat powder and 20% of the binder material of the polyester-based resin at a weight ratio, molded and fixed as a composite magnetic body 51, and then attached to the outer periphery. An external electrode is formed.

FIG. 10 shows the frequency characteristics of the attenuation obtained when the characteristics of the feed-through EMI filter of FIG. 9 are measured with a measuring system having an impedance of 50Ω. As can be seen from FIG. 10, it has a function of blocking a high-frequency current in the GHz band generated during the high-speed switching operation of the IC, and can suppress EMI.

In particular, at frequencies of 1 GHz and higher, the composite magnetic material also exhibits a property as resistance (the imaginary part μr ″ of the complex relative magnetic permeability increases around 1 GHz as shown in FIG. 8), and thus EMI. It also has a function of consuming unnecessary high-frequency energy, which is a cause of the high frequency current, and is extremely effective in reducing high-frequency current in the inner lead portion.

Although the embodiments of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited to the embodiments and various modifications and changes can be made within the scope of the claims. There will be.

[0049]

In a circuit in which an IC is mounted on a printed circuit board, a high-speed switching operation of the IC generates a high-frequency current, which flows through a loop of a line for supplying DC power to the IC to emit EMI. Are known. In a circuit using such an IC, a DC power supply is supplied stably, and the high-frequency current is reduced.
And a decoupling capacitor between GND and GND (between the _VDD and Vss terminal pins of the IC). Although the capacitance value of the decoupling capacitor is determined by the high-frequency current to be bypassed, it is about 1,000 pF to about 0.1 μF.

In a practical circuit in which a number of ICs to which such decoupling capacitors are connected are connected, each I
Since the capacitance value of the decoupling capacitor differs due to the difference in the operation speed of C, the high-frequency current generated by the switching operation of the IC flows through the DC power supply line widely as shown in FIG. The current path is larger than the current loop (loop A) of each IC chip. As the loop gets larger, the level of EMI emitted from the loop increases.

As described in detail in the embodiment of the present invention, the EMI filter element according to the present invention is provided with a decoupling capacitor and a through-type EMI filter formed of a composite magnetic material in the inner lead portion. The following effects can be obtained by the IC.

(1) Since the loop through which the high-frequency current generated by the switching operation of the IC flows can be reduced, the electromagnetic interference wave radiated from this loop can be suppressed low.

Further, if the configuration is such that the periphery of the IC chip is shielded with a conductor, the IC chip can be separated from the outside by the shield and the penetrating EMI filter (zone separation can be performed). Become.

(2) Since the EMI can be suppressed at the inner lead portion, the EM is mounted on the printed wiring board on which the IC is mounted.
There is an effect that components for suppressing I are unnecessary or the number of members can be reduced, and the size of the substrate can be reduced, the wiring pattern can be simplified, and the economic effect is large.

(3) In a composite magnetic material obtained by molding a composite material comprising a metal magnetic material powder such as Fe—Si and a binder resin, the composite magnetic material is formed from a VHF band to an SHF band, and a ferrite sintered body powder. In a composite magnetic material obtained by molding a composite material composed of a binder resin, SHF
The band covers the EMI frequency spectrum where the complex relative magnetic permeability is large in the band and an IC is generated.

By the way, CPU (microprocessor)
Clock frequency exceeds 500 MHz, and the harmonic component of the clock frequency that becomes EMI is UHF
From band to SHF band. Further, the main clock frequency of the personal computer exceeds 100 MHz, and the harmonic component of the clock frequency serving as EMI ranges from the VHF band to the SHF band.

(4) A resin molding method using a mold can be applied to the through-type EMI filter formed on the inner lead portion, so that the degree of freedom in setting the shape and dimensions is large.

[Brief description of the drawings]

FIG. 1 is a plan sectional view showing a first embodiment of an IC with an EMI filter element according to the present invention.

FIG. 2 is an equivalent circuit diagram of a model focusing on a DC power supply portion of an IC in the first embodiment.

FIG. 3 is a partial perspective view illustrating a shield structure according to the first embodiment.

FIG. 4 is an explanatory diagram showing EMI measures by zone separation.

FIG. 5 is a plan sectional view showing a second embodiment of the present invention.

FIG. 6 is an equivalent circuit diagram showing a model focusing on a DC power supply portion of an IC in the second embodiment.

FIG. 7 is an example of a composite magnetic material for forming a through-type EMI filter, which is a complex relative magnetic permeability of a composite magnetic material obtained by molding a composite material composed of powder of a ferrite sintered body and a resin binder. FIG.

FIG. 8 is another example of a composite magnetic body for forming a through-type EMI filter, which shows a complex specific permeability of a composite magnetic body obtained by molding a composite material including a metal magnetic powder and a resin binder. It is a graph which shows a magnetic susceptibility.

FIG. 9 is an example of a structure of a through-type EMI filter using a composite magnetic body obtained by molding a composite material including a metal magnetic substance powder and a resin binder.

FIG. 10 shows a penetration type EMI using a composite magnetic body obtained by molding a composite material composed of a metal magnetic substance powder and a resin binder.
6 is a graph showing frequency characteristics of the amount of attenuation of a filter.

FIG. 11 is a sectional view of a first conventional example.

FIG. 12 is a perspective view of a second conventional example.

FIG. 13 is a circuit diagram of a third conventional example.

FIG. 14 is a structural view of a third conventional example.

FIG. 15 is a circuit diagram of a current return model focusing on a decoupling capacitor.

[Explanation of symbols]

 1, 5, 20 IC chip 10 IC 21 Bonding pad 25, 25a, 25b Conductor lead 26, 26a, 26b Inner lead 30 Outer package 40, 41 Decoupling capacitor 50 Penetrating EMI filter 51 Composite magnetic body 52 External electrode 55 Conductor shield

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashige Konno 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (56) References JP 2000-58740 (JP, A) 130453 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 23/50 H01L 25/00

Claims (4)

(57) [Claims] An integrated circuit chip, a capacitive element connected between a pair of DC power supply inner leads connected to the integrated circuit chip, and a composite provided around one of the inner lead pairs A through-type EMI filter having a magnetic body and an external electrode provided on the outer periphery of the composite magnetic body and electrically connected to the other of the pair of inner leads, inside the outer package; An integrated circuit with an EMI filter element, wherein the filter is arranged at a position closer to the outer side than the connection point of the capacitance element of the inner lead. 2. The integrated circuit with an EMI filter element according to claim 1, wherein the capacitance element is provided on the integrated circuit chip housed in the package. 3. The composite magnetic material is formed by molding a composite material composed of a powder of a ferrite sintered body and a resin binder, or a composite material composed of a powder of a metal magnetic material and a resin binder. 3. The integrated circuit with an EMI filter element according to 2. 4. The integrated circuit with an EMI filter element according to claim 1, wherein the periphery of said integrated circuit chip is shielded by a conductor.