Embedded filter QFN (Quad Flat No-lead) tube shell applicable to miniaturized SIP (Session Initiation Protocol)

Abstract

The invention relates to the technical field of packaging tube shells, and discloses an embedded filter QFN (Quad Flat No-lead) tube shell applicable to a miniaturized SIP (Session Initiation Protocol), which comprises a shielding cover, a filter, a ceramic substrate, a bottom bonding pad and a chip, the bottom bonding pad is a QFN packaging bonding pad and is located at the bottom of the ceramic substrate. A filter is integrated in a ceramic substrate through an LTCC method, the periphery of the filter is a grounding plane, the grounding plane enables layers of the ceramic substrate to be connected with a bottom bonding pad through metal via holes, and a radio frequency input end and a radio frequency output end of the filter are led out from the interior of the ceramic substrate to the outside. The radio frequency input end and the radio frequency output end are arranged on the upper surface of the ceramic substrate; a plurality of chips are arranged on the upper surface of the ceramic substrate, and the chips are communicated with the filter through the radio frequency input end and the radio frequency output end; and the shielding case and the ceramic substrate are fixedly connected to form a closed space for packaging the chip. According to the invention, the filter is integrated in the tube shell, so that the layout space is saved, and the requirement of miniaturized SIP can be met.

Description

Technical Field

[0001] The invention relates to the technical field of packaged tube shells, and in particular to a QFN tube shell with an embedded filter which can be applied to a miniaturized SIP. Background Art

[0002] In today's highly integrated information age, how to take up less space to achieve as many functions as possible has become the direction of the electronic components industry. The manufacturing of chips requires the protection of the packaging shell, and the traditional plastic packaging process is difficult to meet the requirements of high-frequency environments. The LTCC (Low Temperature Co-fired Ceramic) packaging method, which is more convenient to layout and has lower losses, has begun to enter the industry's sight. The traditional LTCC packaging ceramic substrate is usually not fully utilized. Using LTCC to integrate more functions into the QFN (Quad Flat No-leads Package) tube shell to meet the needs of miniaturized SIP (System In a Package) is in line with the direction of taking up less space and achieving multiple functions. Summary of the invention

[0003] In view of this, the present invention provides a QFN tube shell with an embedded filter applicable to a miniaturized SIP, wherein the filter is integrated into the tube shell, thereby saving layout space and meeting the requirements of a miniaturized SIP.

[0004] The present invention is realized by the following technical scheme: an embedded filter QFN tube shell applicable to miniaturized SIP comprises a shielding cover, a filter, a ceramic substrate, a bottom pad and a chip; the bottom pad is a QFN package pad and is located at the bottom of the ceramic substrate; the filter is integrated into the ceramic substrate by the LTCC method, the filter is surrounded by a ground plane, the ground plane is connected to the bottom pad between the layers of the ceramic substrate through metal vias, the radio frequency input end and the radio frequency output end of the filter are led outward from the inside of the ceramic substrate, and the radio frequency input end and the radio frequency output end are arranged on the upper surface of the ceramic substrate; a plurality of chips are arranged on the upper surface of the ceramic substrate, and the chips are connected with the filter through the radio frequency input end and the radio frequency output end; the shielding cover is fixedly connected to the ceramic substrate to form a closed space to package the chip.

[0005] Furthermore, the filter is composed of several stages of resonators, and signals are transmitted between the resonators through spatial coupling. Each stage of the resonator is provided with several upper electrodes and several lower electrodes, one end of each electrode is short-circuited to the ground and the other end is left open. The upper and lower electrodes are arranged alternately, and the open ends of the upper and lower electrodes partially overlap to form capacitive coupling. The upper electrodes of the first and last resonators are respectively led to the RF input end and the RF output end through taps.

[0006] Furthermore, a plurality of placement cavities are provided on the upper surface of the ceramic substrate for placing the chip, and the placement cavities are respectively arranged on both sides of the RF input end and the RF output end.

[0007] Furthermore, a protrusion is provided on the inner side wall of the shielding cover, and the protrusion is located between the radio frequency input end and the radio frequency output end.

[0008] Furthermore, the bottom pad is provided with a central pad, and the central pad is an array composed of square pads, and the square pads are cut by standard QFN package pads.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] 1. The present invention integrates the filter into the ceramic substrate through LTCC, and the package integrates the function of the filter, which can isolate other stray signals, save the overall layout space, and meet the miniaturized SIP requirements.

[0011] 2. The two sides of the protrusion of the present invention are the RF input end and the RF output end respectively. The protrusion can reduce the coupling between the two ends and reduce the risk of internal self-excitation.

[0012] 3. The bottom pad and the central pad of the present invention can reduce the welding area, facilitate the welding and installation of the tube shell without affecting the performance, and improve the efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is an exploded view of the QFN tube shell of the present invention.

[0014] Figure 2 FIG. 1 is an overall schematic diagram of the QFN tube shell of the present invention.

[0015] Figure 3 Schematic diagram of the shielding cover.

[0016] Figure 4 The overall schematic diagram of the filter.

[0017] Figure 5 Filter decomposition diagram

[0018] Figure 6 This is a schematic diagram of the bottom pad.

[0019] Among them, 1 is a shielding cover, 2 is a filter, 3 is a ceramic substrate, 4 is a bottom pad, 5 is a placement cavity, 6 is a radio frequency input terminal, 7 is a radio frequency output terminal, 8 is a tap, 9 is an upper electrode, 10 is a lower electrode, and 11 is a protrusion. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0021] like Figure 1 , 2 As shown, the present invention provides a QFN tube shell with an embedded filter that can be applied to a miniaturized SIP. The device includes a shielding cover 1, a filter 2, a ceramic substrate 3, a bottom pad 4 and a chip; the bottom pad 4 is a QFN package pad and is located at the bottom of the ceramic substrate 3; the filter 2 is integrated into the ceramic substrate 3 by the LTCC method, and the filter 2 is surrounded by a ground plane. The ground plane is connected to the bottom pad 4 between the layers of the ceramic substrate 3 through metal vias, so that the ground plane inside the tube shell and the use environment of the tube shell are the same reference ground. The RF input terminal 6 and the RF output terminal 7 of the filter are led out from the inside of the ceramic substrate 3, and the RF input terminal 6 and the RF output terminal 7 are arranged on the upper surface of the ceramic substrate 3; a plurality of chips are arranged on the upper surface of the ceramic substrate 3, and the chip is connected to the filter 2 through the RF input terminal 6 and the RF output terminal 7; the shielding cover 1 is fixedly connected to the ceramic substrate 3 to form a closed space to package the chip, shield the electromagnetic signal, and suppress the out-of-band RF signal.

[0022] like Figure 4 , 5 As shown, the filter 2 is composed of several stages of resonators, each stage of the resonator is provided with several upper electrodes 9 and several lower electrodes 10, and the upper electrodes 9 of the first and last resonators are respectively led out to the RF input terminal 6 and the RF output terminal 7 through the tap 8, and the RF input terminal 6 and the RF output terminal 7 are arranged on the upper surface of the ceramic substrate 3. In this embodiment, the filter 2 is composed of six stages of resonators, and the resonators of each stage are placed side by side at a certain interval. The signals are transmitted between the resonators through spatial coupling, and the bandwidth of the filter can be adjusted by adjusting the interval between the resonators; each stage of the resonator is provided with five electrodes to adjust the frequency of the filter 2 to the required frequency, and the five electrodes are respectively three upper electrodes 9 of the same size and two lower electrodes 10 of the same size, one end of each electrode is short-circuited to the ground, and the other end is suspended and open-circuited, the upper and lower electrodes are alternately arranged, and the open-circuited ends of the upper and lower electrodes are partially overlapped, and the alternately overlapping parts of the electrodes form capacitive coupling, and the resonant frequency of the resonator can be adjusted by adjusting the size of the overlapping part; the open-circuited ends of the three upper electrodes 9 of the first and last resonators are connected to the tap 8 to lead out the RF input terminal 6 and the RF output terminal 7.

[0023] In a specific implementation, the size of each level of resonator and the number of electrodes can be adjusted according to the actual frequency used, the distance between each level of resonators can be adjusted according to the actual required frequency bandwidth, and the positions of the taps 8 at the RF input terminal 6 and the RF output terminal 7 can be optimized and adjusted according to the actual calculation results.

[0024] The filter 2 is embedded in the multilayer ceramic substrate 3 through LTCC technology to make a functional module with integrated filter, which can further miniaturize and increase the density of the circuit. That is, the filter 2 is integrated into the ceramic substrate 3 to meet the needs of miniaturized SIP; the filter 2 can use other forms of filters, such as comb-line bandpass filters, cross-finger lines, and vertical resonant cavities.

[0025] like Figure 3 As shown, a protrusion 11 is provided on the inner side wall of the shielding cover 1, that is, a concave groove is formed inside the shielding cover 1, and the protrusion 11 is located between the RF input terminal 6 and the RF output terminal 7, and is used for coupling between the RF input terminal 6 and the RF output terminal 7, reducing the risk of self-excitation after the internal packaging of the tube shell. In this embodiment, the shielding cover 1 is 4.8mm long, 4.8mm wide, 0.5mm thick, 0.5mm chamfered outside (the outer corner of the shielding cover 1 is processed into an arc shape with an arc radius of 0.5mm), and 0.3mm chamfered inside (the inner corner of the shielding cover 1 is processed into an arc shape with an arc radius of 0.3mm). A protrusion 11 of 0.4mm*1.125mm is provided inwardly on the left side wall of the shielding cover 1, and the protrusion 11 is 0.2mm away from the middle of the left side wall. After the shielding cover 1 is inverted on the upper surface of the ceramic substrate 3, the protrusion 11 is located between the RF input terminal 6 and the RF output terminal 7. The shielding cover 1 is made of metal material according to actual use requirements, and may be aluminum, copper, gold or other metal materials. The shielding cover 1 and the ceramic substrate 3 may be connected and fixed together by bonding or welding to form a closed space and meet airtight requirements.

[0026] The upper surface of the ceramic substrate 3 is provided with a plurality of placement cavities 5 for placing various chips, further meeting the requirements of miniaturized SIP. The placement cavities 5 are respectively arranged on both sides of the RF input terminal 6 and the RF output terminal 7. The specific layout positions of the plurality of placement cavities 5 can be adjusted according to actual requirements. One or more chips to be packaged are placed in the placement cavity 5, and bonding wires are applied to the bonding points of the RF input terminal 6 and the RF output terminal 7 on the chip and the pads on the upper surface of the ceramic substrate 3 to cascade the chip with the filter 2 inside the ceramic substrate 3. The closer the placement cavity 5 on the upper surface of the ceramic substrate 3 is to the RF input terminal 6 and the RF output terminal 7, the shorter the bonding wires required for assembly.

[0027] like Figure 6As shown, the bottom pad 4 is provided with a central pad, and the central pad is an array composed of square pads, which are cut by standard QFN package pads. In this embodiment, the bottom pad 4 can be used to fit the 29-pin 5mm×5mm standard QFN package pad, and the large pad of the 29th pin is cut into a number of square pads, and the square pads form a square array arranged on the bottom pad 4. That is, in this embodiment, the bottom pad 4 retains the 29-pin 5mm×5mm standard QFN package pads No. 1 to No. 28, and the large pad No. 29 is cut to form a central pad. The array composed of square pads can reduce the welding area, so that the flux is more evenly distributed between the pads, and at the same time avoids large-area solder from lifting the middle of the tube shell, so that the surrounding pins are suspended, which is convenient for the welding and installation of the tube shell and improves efficiency.

[0028] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A QFN tube shell with embedded filter applicable to miniaturized SIP, characterized in that: It includes a shielding cover, a filter, a ceramic substrate, a bottom pad and a chip; the bottom pad is a QFN package pad located at the bottom of the ceramic substrate; the filter is integrated into the ceramic substrate by the LTCC method, the filter is surrounded by a ground plane, the ground plane connects the layers of the ceramic substrate with the bottom pad through metal vias, and the RF input and RF output of the filter are led out from the inside of the ceramic substrate, and the RF input and RF output are arranged on the upper surface of the ceramic substrate; a plurality of chips are arranged on the upper surface of the ceramic substrate, and the chips are connected to the filter through the RF input and RF output; the shielding cover is fixedly connected to the ceramic substrate to form a closed space to package the chip.

2. The QFN tube package with embedded filter applicable to miniaturized SIP as claimed in claim 1, characterized in that: The filter is composed of several stages of resonators, and signals are transmitted between the resonators through spatial coupling. Each stage of the resonator is provided with several upper electrodes and several lower electrodes. One end of each electrode is short-circuited to the ground and the other end is left open. The upper and lower electrodes are arranged alternately, and the open ends of the upper and lower electrodes partially overlap to form capacitive coupling. The upper electrodes of the first and last resonators are respectively led to the RF input and RF output ends through taps.

3. The QFN tube package with embedded filter applicable to miniaturized SIP as claimed in claim 1, characterized in that: The upper surface of the ceramic substrate is provided with a plurality of placement cavities for placing chips, and the placement cavities are respectively arranged on both sides of the radio frequency input end and the radio frequency output end.

4. The QFN tube package with embedded filter applicable to miniaturized SIP as claimed in claim 3, characterized in that: A protrusion is arranged on the inner side wall of the shielding cover, and the protrusion is located between the radio frequency input end and the radio frequency output end.

5. The embedded filter QFN tube shell applicable to miniaturized SIP as claimed in any one of claims 1 to 4, characterized in that: The bottom pad has a central pad, which is an array of square pads, and the square pads are cut through standard QFN package pads.

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