JP2006261557A - Substrate for package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for a high-frequency semiconductor package which is hardly affected by parasitic inductance or parasitic capacity, accordingly exhibits small transmission loss, and exhibits a high degree of electromagnetic compatibility. <P>SOLUTION: The substrate for package is provided with: a core substrate 1 which is made of conductive metal and is provided with holes 1A into which coaxial cables 2 covered with a shield coating 2A can be inserted; the coaxial cables 2 whose ends are inserted into the holes 1A, and whose shield coating 2A is electrically connected to the peripheral borders of the holes 1A; an insulating resin 3 which fills the two faces of the core substrate 1 into which the ends of the coaxial cables 2 are inserted, and which has a surface exhibiting the same plane as the ends of the coaxial cables 2; and electrode pads 4 which are formed on the edges of center conductors 3B at the ends of the coaxial cables 2 which appear on the same plane as the insulating resin 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a package substrate that can mount a high-frequency semiconductor element and transmit a high-frequency signal with low loss.

  In the information communication field in recent years, high speed and large capacity are important issues, and a microwave band having a relatively large amount of information transmission and a millimeter wave band of 30 GHz or more are being actively used.

  For such wireless base stations and wireless terminals that perform high-frequency communication, microwave packages and millimeter-wave packages with high-frequency ICs are used, and vehicle collisions also occur in fields other than information communication. The millimeter wave band is used for in-vehicle radar (millimeter wave radar) and measurement sensors for the purpose of prevention.

  Under such circumstances, it is desired to realize an IC package having high mass productivity and low cost in addition to maintaining electrical characteristics at high frequencies.

  Usually, a millimeter-wave package on which a semiconductor element (IC chip) in the millimeter-wave band is mounted requires a low-loss transmission line for connecting the semiconductor elements or connecting the semiconductor package and the antenna.

  Generally, a microstrip line, a coaxial wiring, and a waveguide are mainly used for a signal line of a high frequency signal, and a semiconductor element is mounted on one end of the microstrip line on the same plane on the circuit board. When the antenna is equipped, the other end is coaxial-waveguide-converted with the microstrip line, and the signal propagates through the waveguide and is transmitted from the antenna connected to the waveguide. Radiated.

  FIG. 9 is a cutaway side view showing an example of a conventional high-frequency semiconductor package. As is clear from the figure, an oscillation circuit (Voltage Controlled Oscillator: VCO) 12 is mounted on one surface side of the package substrate 11, and On the same plane, a microwave integrated circuit (MMIC) 13 is mounted via an Au bump 14, and both are electrically connected by an Au wire 15 and an electrode / transmission line 16. Further, a waveguide 20 provided on the same plane and connected to the microwave integrated circuit 13 via the electrode / transmission line 17, via 18, and transmission line 19 is connected to the antenna 21, and the whole is a hermetic seal or the like. The can sealing portion 22 is sealed.

  In this conventional example, the signal is transmitted by the oscillation circuit 12 → Au wire 15 → electrode / transmission line 16 → Au bump 14 → microwave integrated circuit 13 → Au bump 14 → electrode / transmission line 17 → via 18 → transmission line 19. → Coaxial-waveguide conversion (via) 20 → antenna 21

  In the microwave band and the millimeter wave band, it is desirable to shorten the transmission line length as much as possible in order to reduce transmission loss. However, as shown in FIG. 9, in the high-frequency semiconductor package in which the circuit elements are mounted on the microstrip line in a plane, the portion where the cross-sectional shape of the conductor constituting the transmission line is discontinuous, that is, in the description of the transmission order described above. In the portion indicated by the arrow (→), mismatch occurs in the characteristic impedance, which causes transmission loss. The mismatch in characteristic impedance is caused by, for example, signal reflection at discontinuous portions and increase in parasitic inductance components at Au wires and vias.

  In addition, the signal transmission line is susceptible to electromagnetic interference such as electromagnetic interference and electromagnetic susceptibility due to the structure in which the microstrip line is mounted in a plane. Furthermore, there is a limit to downsizing the package in order to ensure isolation between semiconductor elements.

  By the way, the structure which shortens wiring length is known by the through-hole connection of a coaxial structure in a multilayer wiring board (for example, refer patent document 1). In other words, a double-cylindrical coaxial through hole consisting of an outer layer through hole and an inner layer through hole filled with metal is formed on the multilayer wiring board, and a filled via is disposed directly above the inner layer through hole to shorten the wiring length. To do.

  However, the configuration found in Patent Document 1 is an electrical connection between a semiconductor element (IC chip) mounted on one side of a multilayer wiring board and a daughter board connected to the other side of the multilayer wiring board via a coaxial through hole. It is intended to be connected to the semiconductor device and is not related to the double-sided mounting semiconductor package. No consideration is given to transmission loss in high-frequency transmission.

  In addition, in a high-frequency circuit module in which high-frequency circuit components are mounted on both sides of a multilayer dielectric substrate, loss in the millimeter-wave transmission line can be reduced by using a coaxial via hole extending in the vertical direction of the substrate as a part of the transmission line. The structure which reduces is proposed (for example, refer patent document 2).

  This configuration uses a vertical coaxial via that penetrates the substrate as part of the transmission line, but uses a microstrip line for transmission from the coaxial via to another high frequency circuit element located on the opposite side of the substrate. ing. Accordingly, in this case as well, the cross-sectional shape of the conductor becomes discontinuous between the via and the microstrip line as in the conventional technique described with reference to FIG. 9, resulting in mismatch in characteristic impedance.

  As described above, the conventional high-frequency semiconductor package has a problem in the wiring structure for transmitting a high-frequency signal between semiconductor chips, and in particular, transmission loss is reduced in the microwave band and the millimeter wave band. Must.

  Usually, in the semiconductor package of the microwave band and the millimeter wave band, the package substrate used for these has a semiconductor chip mounted in a plane in order to suppress the influence of the parasitic inductance due to the three-dimensional structure such as the via on the wiring structure. Yes.

  The wiring on the same plane, such as the microstrip line and coplanar waveguide line used in that case, is usually not shielded. For high-frequency signals that handle microwaves of 1 GHz or higher and millimeter waves of 30 GHz or higher, wiring Since the wavelength becomes significant with respect to the length, the wiring itself functions as an antenna, causing interference between the wirings due to the transmission and reception of electromagnetic waves, which causes a malfunction in the operation of the device.

Therefore, it is necessary to have a wiring structure that shields the wiring without generating parasitic inductance. However, due to the structure of the wiring, there is a portion where the cross-sectional shape is discontinuous at the boundary such as bump-wiring-via in the transmission line. Therefore, there is a problem that characteristic impedance mismatch occurs due to the parasitic capacitance due to the wiring, and transmission loss is likely to occur, and further, it is easily affected by electromagnetic interference such as electromagnetic interference and electromagnetic susceptibility.
JP 2002-305377 A JP 2003-133801 A

  The present invention seeks to provide a substrate for a high-frequency semiconductor package that is less affected by parasitic inductance and parasitic capacitance, therefore has less transmission loss, and that is excellent in electromagnetic environment compatibility (EMC).

  In a package substrate according to the present invention, a core substrate made of a conductive metal provided with a hole having a diameter into which a coaxial cable with a shield coating exposed can be inserted, and a tip inserted into the hole. And a coaxial cable having a shield coating electrically connected to the periphery of the hole, and the front and back surfaces of the core substrate into which the front end of the coaxial cable is inserted, and the surface side is flush with the front end of the coaxial cable. It is basically provided with an insulating resin and an electrode pad formed on the end face of the central conductor at the end of the coaxial cable exposed on the same plane as the insulating resin.

  A high-frequency semiconductor device mounted on a package substrate can be easily shielded with a coaxial cable, and a small package substrate with low transmission loss and excellent electromagnetic compatibility (EMC) has been realized. it can.

  FIG. 1 to FIG. 6 are fragmentary exploded perspective views (FIG. 1) showing the package substrate at the main points for explaining the first example of the process for manufacturing the package substrate according to the present invention. FIG. 2 is a side view (FIGS. 2 to 6), which will be described below with reference to these drawings.

See Fig. 1 (1)
A core substrate 1 made of a conductive metal is prepared, and the core substrate 1 is formed with a hole 1A having a diameter through which the coaxial cable 2 exposing the shield coating 2A can be inserted by removing the insulation jacket. Symbol 2B indicates the central conductor of the coaxial cable 2.

See Figure 2 (2)
The tip of the coaxial cable 2 is inserted into the hole 1A of the core substrate 1, the periphery of the hole 1A and the shield coating 2A of the coaxial cable 2 are soldered, and the core substrate 1 and the shield coating 2A are electrically grounded and machined. To fix.

See Fig. 3 (3)
The back surface and the front surface of the core substrate 1 to which the wiring composed of the coaxial cable 2 is attached are embedded and integrated with the insulating resin 3. As the insulating resin 3, a thermosetting resin material such as an epoxy resin can be used.

See Fig. 4 (4)
The insulating resin 3 on the front surface side is polished so that the central conductor 2B and the shield coating 2A of the coaxial cable 2 are flush with the surface of the core substrate 1.

Refer to FIG. 5 (5)
An electrode pad 4 made of a material selected from Au, Ag, Cu, or the like is formed on the center conductor 2B on the exposed end surface of the coaxial cable 2 by applying a plating method. The electrode pad 4 may be formed by using a conductive paste printing method instead of the plating method.

See FIG. 6 (6)
The semiconductor chip 5 is flip-chiped, the bumps are opposed to the electrode pads 4, and bonding is performed for mounting. As the bumps of the semiconductor chip 5, solder bumps or gold bumps are used.

  FIGS. 7 and 8 are cut side views of the main part showing the package substrate at the process points for explaining the second example of the process for manufacturing the package substrate according to the present invention. This will be described with reference to the drawings. In the first example, the manufacturing process described with reference to FIGS. 1 to 4, that is, the core substrate 1 is prepared, and then the central conductor 2 B and the shield coating 2 A of the coaxial cable 2 are attached to the surface of the core substrate 1. Since the process until polishing so as to be in the same plane is the same in the second example, it will be omitted and will be described from the next stage.

See Fig. 7 (1)
An electrode pad 4 made of a material selected from Au, Ag, Cu, etc. is formed on the center conductor 2B at the end face of the exposed coaxial cable 2 by applying a plating method and connected to the shield coating 2A. The electrode pad 4A is formed. In order to form the electrode pads 4 and 4A, a conductive paste printing method may be used instead of the plating method.

Refer to FIG. 8 (2)
The semiconductor chip 5 is flip-chiped, the bumps are opposed to the electrode pads 4, and the waveguide antenna 7 is opposed to the electrode pads 4 and 4 A via the coaxial cable-waveguide converter 6. Mount by bonding. The bumps used here may be solder bumps or gold bumps.

It is a principal part exploded slope view showing the package substrate in the process key for explaining the 1st example of the process of manufacturing the package substrate according to the present invention. It is a principal part cutting side view showing the package substrate in the process important point for demonstrating the 1st example of the process which manufactures the package substrate according to this invention. It is a principal part cutting side view showing the package substrate in the process important point for demonstrating the 1st example of the process which manufactures the package substrate according to this invention. It is a principal part cutting side view showing the package substrate in the process important point for demonstrating the 1st example of the process which manufactures the package substrate according to this invention. It is a principal part cutting side view showing the package substrate in the process important point for demonstrating the 1st example of the process which manufactures the package substrate according to this invention. It is a principal part cutting side view showing the package substrate in the process important point for demonstrating the 1st example of the process which manufactures the package substrate according to this invention. It is a principal part cutting side view showing the package substrate in the process important point for demonstrating the 2nd example of the process which manufactures the package substrate according to this invention. It is a principal part cutting side view showing the package substrate in the process important point for demonstrating the 2nd example of the process which manufactures the package substrate according to this invention. It is a principal part cutting side view showing an example of the conventional high frequency semiconductor package.

Explanation of symbols

1 Core substrate 1A Hole 2 Coaxial cable 2A Shield coating 3 Insulating resin 4 Electrode pad

Claims (3)

A core substrate made of a conductive metal provided with a hole having a diameter into which a coaxial cable having a shield coating exposed can be inserted;
A coaxial cable having a tip inserted into the hole, and a shield coating electrically connected to the periphery of the hole;
Filling the front and back of the core substrate into which the tip of the coaxial cable is inserted, and an insulating resin whose surface side is flush with the tip of the coaxial cable;
A package substrate, comprising: an electrode pad formed on an end face of a central conductor at a front end of a coaxial cable exposed on the same plane as the insulating resin. 2. A semiconductor chip comprising bumps electrically connected to electrode pads formed on an end face of a central conductor at the end of a coaxial cable exposed on the same plane as the insulating resin. The package substrate according to 1. An antenna comprising a waveguide connected to an electrode pad formed on the end face of a central conductor at the end of a coaxial cable exposed on the same plane as the insulating resin via a coaxial-waveguide converter The package substrate according to claim 1, further comprising:

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