Broadband power amplifier package with integrated protrusion heat sink structure for optimized bonding wire length

Abstract

A power amplifier package is disclosed. The power amplifier package includes: a heatsink having a protruding heat dissipation structure; a transistor die disposed on the surface of the protruding heat dissipation structure; an insulating substrate formed on the surface of the heatsink and having an opening that exposes the protruding heat dissipation structure upward; and an input and output impedance matching network formed on the surface of the insulating substrate and electrically connected to the transistor die by a bonding wire.

Description

Technology Field

[0001] The present invention relates to a high-output power amplifier package, and more specifically, to a power amplifier package capable of realizing broadband characteristics and high-efficiency operation across the entire operating frequency band by optimizing the internal matching circuit and heatsink structure in a high-output power amplifier package that incorporates a transistor die. Background Technology

[0003] Conventional high-power amplifiers have a structure that integrates an impedance matching network inside the amplifier to operate in high frequency bands such as the Ku band (a frequency range of approximately 12 GHz to 18 GHz). When designing such internal matching circuits, a low Q-factor matching network is required to satisfy the wideband operation and high-efficiency characteristics of the power amplifier.

[0004] However, under high frequency band and high output power conditions, the Q-factor of the matching network increases due to the large parasitic capacitance of the transistor, making it difficult to achieve wideband characteristics. In particular, in existing package structures, long bonding wires are used due to the height difference between the transistor die and the matching circuit board, which leads to an increase in wire inductance and a rise in the Q-factor, resulting in narrowband characteristics. The problem to be solved

[0006] The present invention, aimed at solving the aforementioned problems, is to achieve broadband impedance matching and broadband high-efficiency operation characteristics by applying a protruding heatsink structure and a heatsink having excellent thermal conductivity characteristics to a high-output power amplifier package.

[0007] More specifically, the purpose is to obtain broadband impedance matching and broadband frequency characteristics by implementing a low Q-factor matching network through the reduction of the height difference between the die and the matching substrate by increasing the transistor die attachment area and minimizing the bonding wire length.

[0008] In addition, the purpose is to realize high-efficiency wideband operation by applying a heatsink that possesses excellent thermal conductivity characteristics and a thermal expansion coefficient similar to that of the substrate, thereby enabling stable heat dissipation even at high output power.

[0009] By achieving these objectives, it is possible to simultaneously realize broadband expansion and high efficiency of high-output power amplifiers operating in high frequency bands such as the Ku band. means of solving the problem

[0011] A power amplifier package according to one aspect of the present invention for achieving the above-described purpose comprises: a heat sink having a protruding heat dissipation structure; a transistor die disposed on the surface of the protruding heat dissipation structure; an insulating substrate formed on the surface of the heat sink and having an opening that exposes the protruding heat dissipation structure upward; and an input and output impedance matching network formed on the surface of the insulating substrate and electrically connected to the transistor die by a bonding wire.

[0012] In the embodiment, as the height difference between the transistor die and the input and output matching network is reduced by the protruding heat dissipation structure, the length of the bonding wire connecting the transistor die and the input and output matching network is minimized.

[0013] In an embodiment, the thickness of the protruding heat dissipation structure is designed according to the thickness of the transistor die and the insulating substrate.

[0014] In an embodiment, the heat sink has a metal cladding structure.

[0015] A power amplifier package according to another aspect of the present invention comprises: a heat sink comprising a lower metal layer, an upper metal layer having a protruding heat dissipation structure, and an intermediate metal layer disposed between the lower metal layer and the upper metal layer; a transistor die disposed on the surface of the protruding heat dissipation structure; an insulating substrate formed on the surface of the upper metal layer and having an opening that exposes the protruding heat dissipation structure upward; and an input and output impedance matching network formed on the surface of the insulating substrate and electrically connected to the transistor die by a bonding wire.

[0016] In the embodiment, the lower metal layer and the upper metal layer comprise a copper-based material, and the intermediate metal layer comprises a molybdenum-based material.

[0017] In the embodiment, as the height difference between the transistor die and the input and output impedance matching network is reduced by the protruding heat dissipation structure formed on the upper metal layer, the length of the bonding wire connecting the transistor die and the input and output matching network is minimized. Effects of the invention

[0019] According to the present invention, by eliminating the height difference between the transistor die and the matching circuit board and minimizing the bonding wire length, a wideband impedance matching network with a low Q-factor can be implemented, thereby obtaining wideband frequency characteristics. In addition, by applying a heatsink having excellent thermal conductivity and a thermal expansion coefficient similar to that of the substrate, stable heat dissipation is possible even during high-power operation, allowing high-efficiency characteristics to be maintained over a wideband.

[0020] As a result, broadband impedance matching and high-efficiency characteristics can be simultaneously realized in high-output power amplifiers operating in high frequency bands such as the Ku band, thereby enabling broadband expansion and high efficiency of the high-output power amplifier.

[0021] In particular, since broadband characteristics are significantly improved through low Q-factor matching resulting from the minimization of bonding wire length, stable broadband operation becomes possible even under high frequency and high output power conditions. Brief explanation of the drawing

[0023] FIG. 1 is a plan view of a power amplifier package with a protruding heat dissipation structure applied according to an embodiment of the present invention. Figure 2 is a side view of area A of Figure 1. Figure 3 is a side view of a power amplifier package to which the protruding heat dissipation structure of Figure 2 is not applied. Figure 4 is a photograph of a Ku-band power amplifier package actually fabricated by applying a protruding heat dissipation structure according to an embodiment of the present invention. Figure 5 shows the results of the measured operation performance and simulation performance of the power amplifier package of Figure 4. Specific details for implementing the invention

[0024] Preferred embodiments of the present invention are to be described in more detail. In describing the present invention, to facilitate overall understanding, the same reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0025] The terms used in this specification are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as “comprising” or “having” are intended to indicate the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0026] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0028] The present invention relates to a protruding heatsink structure and a heatsink material with excellent thermal properties applied to a high-power power amplifier package (e.g., a high-power GaN HEMT power amplifier package). Hereinafter, specific embodiments for implementing the present invention will be described in detail with reference to the drawings.

[0030] FIG. 1 is a plan view of a power amplifier package with a protruding heat dissipation structure applied according to an embodiment of the present invention, and FIG. 2 is a side view of area A of FIG. 1.

[0031] Referring to FIGS. 1 and 2, a power amplifier package (100) according to an embodiment of the present invention is designed to operate in the Ku frequency band with a protruding heat dissipation structure. To this end, the power amplifier package (100) includes a heat sink (110), an insulating substrate (120), a transistor die (130), an input impedance matching network (140), and an output impedance matching network (150).

[0032] The heat sink (110) serves to effectively transfer and dissipate heat generated in the power amplifier package (100), particularly heat generated in the transistor die (130). To this end, it may be configured to include a plurality of layers (111, 112 and 113). The plurality of layers (111, 112 and 113) may include a lower metal layer (111), an intermediate metal layer (112), and an upper metal layer (113). The lower metal layer (111) is the lowest layer and may include, for example, a copper (Cu)-based material with excellent thermal conductivity. The upper metal layer (113) is the uppermost layer and may include, for example, a copper (Cu)-based material similar to the lower metal layer (111). The intermediate metal layer (112) is a layer placed between the lower metal layer (111) and the upper metal layer (113), and may include, for example, a molybdenum-based material with excellent thermal conductivity. On the surface of the upper metal layer (113), a mounting area (MA, hereinafter referred to as the 'die mounting area') is defined for attaching (mounting, placement, or forming) a transistor die (130). Above all, the die mounting area (MA) of the upper metal layer (113) has a structure protruding upward (113A, hereinafter referred to as the protruding heat dissipation structure), and the transistor die (130) is attached to the surface of the protruding heat dissipation structure (113A). By attaching the transistor die (130) to the surface of the protruding heat dissipation structure (113A) in this way, the length of the bonding wires (162, 164) described later can be reduced. The thickness (height) of the protruding heat dissipation structure (113A) can be appropriately designed by taking into account the thickness (height) of the transistor die (130) and the thickness (height) of the insulating substrate (120) described later. For example, the thickness of the protruding heat dissipation structure (113A) can be designed as the value obtained by subtracting the thickness of the transistor die (130) from the thickness of the insulating substrate (120).

[0033] An insulating substrate (120) is placed (formed) on the heatsink (110) or the upper metal layer (113) of the heatsink (110). The insulating substrate (120) may be an aluminum-based (e.g., Al2O3) or ceramic-based substrate. The insulating substrate (120) has an opening (AP (Aperture)) that exposes the die attachment area (MA) to the top. Accordingly, a protruding heat dissipation structure (113A) of the upper metal layer (113) is placed in the opening (AP). The shape of the opening (AP) is determined by the shape of the transistor die (130). For example, if the shape of the transistor die (130) is rectangular when viewed from above, the shape of the opening (AP) is rectangular. The area of ​​the opening (AP) is designed to be slightly larger than the area of ​​the protruding heat dissipation structure (113A) when viewed from above.

[0034] The input impedance matching network (140) and the output impedance matching network (150) are placed (formed, patterned, deposited) on an insulating substrate (120) with an opening (AP) in between. That is, a transistor die (130) attached to the surface of a protruding heat dissipation structure (113A) exposed upward by the opening (AP) is placed between the input impedance matching network (140) and the output impedance matching network (150). The input impedance matching network (140) is a circuit pattern that performs input impedance matching and the output impedance matching network (150) performs output impedance matching. The input matching network (140) and the output matching network (150) are electrically connected to the transistor die (130) by bonding wires (162 and 164). Specifically, the input matching network (140) is electrically connected to the input terminal of the transistor die (130) by an input bonding wire (162), and the output matching network (150) is electrically connected to the output terminal of the transistor die (130) by an output bonding wire (164).

[0035] Meanwhile, in an embodiment of the present invention, a gallium nitride high electron mobility transistor (GaN HEMT) die may be used as the transistor die (130).

[0037] Figure 3 is a side view of a power amplifier package to which the protruding heat dissipation structure of Figure 2 is not applied.

[0038] Referring to FIG. 3, in the case of a power amplifier package in which the protruding heat dissipation structure (113A) of FIG. 2 is not applied, the length of the bonding wires (162 and 164) becomes longer because there is a difference between the surface height of the upper metal layer (113) of the heat sink (110) and the surface height of the insulating substrate (120).

[0039] However, as shown in FIG. 2, in the case of a power amplifier package with the protruding heat dissipation structure (113A) of FIG. 2 applied, since the transistor die (130) is attached to the surface of the protruding heat dissipation structure (113A) protruding upward, the height difference between the transistor die (130) and the input / output impedance matching network (140, 150) formed on the surface of the insulating substrate (120) is eliminated, so the bonding wire length (162 and 164) can be minimized.

[0040] When the length of the bonding wire is shortened, the parasitic inductance component caused by the wire is reduced, which allows the Q-factor of the input / output matching network to be lowered. A low Q-factor enables broadband impedance matching, thereby allowing the power amplifier to achieve broadband operating frequency characteristics.

[0041] Table 1 below compares the bonding wire height and corresponding bonding wire inductance modeling values ​​within the package before and after the application of the protruding heat dissipation structure, and these values ​​are example values ​​at an operating frequency of 13.2 GHz.

[0043] Protruding heat dissipation structure not applied Application of protruding heat dissipation structure Bonding wire height 180 µm 50 um Bonding wire inductance 41 pH 33 pH

[0045] Meanwhile, in the embodiments of the present invention, a material having excellent thermal conductivity and a value similar to the coefficient of thermal expansion of the substrate is used as the heatsink material. Specifically, a metal (copper-molybdenum-copper) cladding structure can be applied.

[0046] In this cladding structure, the copper layer provides high thermal conductivity, and the molybdenum layer has a low coefficient of thermal expansion. A nickel barrier can be inserted between the two layers to increase interfacial bonding strength.

[0047] This structure allows for the simultaneous achievement of excellent thermal conductivity and a coefficient of thermal expansion similar to that of the substrate, enabling stable heat dissipation even during high-power operation. Improved thermal performance enables the high-efficiency characteristics of the power amplifier to be maintained across a wide bandwidth.

[0049] Figure 4 is a photograph of a Ku-band power amplifier package actually fabricated by applying a protruding heat dissipation structure according to an embodiment of the present invention, and Figure 5 is a result showing the measured operation performance and simulation performance of the power amplifier package of Figure 4.

[0050] As shown in FIGS. 4 and 5, through the protruding heatsink structure of the present invention and the heatsink with excellent thermal conductivity characteristics, it becomes possible to simultaneously achieve broadband impedance matching and broadband high-efficiency operation in a high-output Ku-band power amplifier.

[0052] Although the present invention has been described with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as described in the following claims.

Claims

Claim 1 A power amplifier package comprising: a heatsink having a protruding heat dissipation structure; a transistor die disposed on the surface of the protruding heat dissipation structure; an insulating substrate formed on the surface of the heatsink and having an opening that exposes the protruding heat dissipation structure upward; and an input and output impedance matching network formed on the surface of the insulating substrate and electrically connected to the transistor die by a bonding wire, wherein the thickness of the protruding heat dissipation structure is configured as the thickness of the insulating substrate minus the thickness of the transistor die, and the heatsink comprises a copper-based lower metal layer, a copper-based upper metal layer, and a molybdenum-based intermediate metal layer disposed between the lower metal layer and the upper metal layer, and a nickel barrier disposed between the lower metal layer and the intermediate metal layer and between the upper metal layer and the intermediate metal layer to increase interfacial bonding strength. Claim 2 A power amplifier package according to claim 1, characterized in that the length of the bonding wire connecting the transistor die and the input and output matching network is minimized as the height difference between the transistor die and the input and output matching network is reduced by the protruding heat dissipation structure. Claim 3 A power amplifier package according to claim 1, wherein the thickness of the protruding heat dissipation structure is designed according to the thickness of the transistor die and the insulating substrate. Claim 4 A power amplifier package according to claim 1, wherein the heatsink has a metal cladding structure. Claim 5 delete Claim 6 delete Claim 7 delete

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