Millimeter wave radio frequency chip ball grid array (BGA) packaging tube shell

Abstract

The invention belongs to the technical field of semiconductor packaging, and discloses a millimeter wave radio frequency chip BGA packaging tube shell which comprises a ceramic base, a kovar enclosure frame, a cover plate and a BGA ball. A first metal coating is plated on the upper surface of the ceramic base, a second metal coating is plated on the lower surface of the ceramic base, a top layer bonding pad is etched on the periphery of the first metal coating, a bottom layer ball mounting pad is etched on the periphery of the second metal coating, and the top layer bonding pad and the bottom layer ball mounting pad are arranged in a one-to-one correspondence mode; the ceramic pedestal is provided with a through hole, and the through hole is internally provided with a copper column which is used for connecting the corresponding top layer bonding pad and bottom layer ball mounting pad. The kovar enclosure frame is fixedly arranged on the peripheral edge of the upper surface of the first metal coating, and the cover plate is packaged on the top of the kovar enclosure frame. According to the invention, the isolation between the radio frequency interfaces is improved, the heat dissipation requirement of the chip is met, and the use cost of the product and the process assembly difficulty are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor packaging and relates to a millimeter wave radio frequency chip BGA packaging tube shell. Background Art

[0002] Microelectronic packaging is the process of reliably installing semiconductor integrated circuit chips on a certain casing. After the chip on the printed circuit board is packaged, the packaged casing has the functions of fixing, sealing, protecting the chip, and connecting the internal circuit and the external circuit. Printed circuit boards can be widely used in radio systems, including battlefield identification, communications, radar and guidance in the military, 5G communication equipment in the civilian field, automotive anti-collision radar equipment, etc.

[0003] In the prior art, millimeter wave RF chips are usually packaged in a metal cavity. However, due to the discontinuity of the transmission path of the RF signal of the millimeter wave RF chip, the transmission signal will generate spatial radiation on the input side of the millimeter wave RF chip, and the radiated electromagnetic signal will propagate through the metal cavity to the output side of the chip. It can be seen that when the existing packaging method is applied to millimeter wave RF chips, the spatial isolation performance is poor, which affects the RF performance of millimeter wave devices. Summary of the invention

[0004] The purpose of the present invention is to provide a millimeter wave radio frequency chip BGA packaging tube shell, aiming to solve the problem of poor spatial isolation performance of the existing millimeter wave radio frequency chip packaging method.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A millimeter wave radio frequency chip BGA packaging tube shell, comprising a ceramic base, a Kovar frame, a cover plate and a BGA ball; The upper surface of the ceramic base is plated with a first metal coating, the lower surface of the ceramic base is plated with a second metal coating, the first metal coating is etched with a top bonding pad around it, the second metal coating is etched with a bottom ball planting pad around it, and the top bonding pad and the bottom ball planting pad are respectively arranged in a one-to-one correspondence; the ceramic base is provided with a through hole, and a copper column for connecting the corresponding top bonding pad and the bottom ball planting pad is provided in the through hole; The kovable frame is fixed at the edges around the upper surface of the first metal coating, the cover plate is encapsulated on the top of the kovable frame, a chip cavity is opened in the middle of the first metal coating and penetrates the first metal coating for installing a millimeter wave RF chip, isolation copper columns are arranged around the upper surface of the first metal coating, the upper end of the isolation copper column does not contact the lower surface of the cover plate, and the distance between the upper end of the isolation copper column and the lower surface of the cover plate is less than 0.1mm; the lower surface of the second metal coating is provided with a solder resist layer, and the BGA ball is welded to the lower surface of the solder resist layer.

[0006] As a limitation, the horizontal spacing and vertical spacing of the BGA balls are both 0.8 mm.

[0007] As a second limitation, a circle of solder resist is provided on the upper surface of the first metal plating layer close to the inner side of the kovable frame.

[0008] As a third limitation, the thickness of the first metal plating layer is 0.2 mm, and the height of the isolated copper column is 0.8 mm.

[0009] As a fourth limitation, the BGA balls form twelve radio frequency interfaces and twelve low frequency interfaces.

[0010] Due to the adoption of the above technical solution, the present invention has the following technical advances compared with the prior art: (1) The present invention forms a packaging cavity for packaging a millimeter wave radio frequency chip by enclosing a ceramic base, a ferrite frame and a cover plate. A chip cavity groove penetrating through the middle of the first metal plating layer can be used to install and fix the chip. The internal space of the packaging cavity can be divided by arranging isolation copper pillars, which significantly improves the isolation between radio frequency interfaces, reduces crosstalk and coupling between radio frequency channels, and can better exert the performance of the millimeter wave radio frequency chip. (2) The thickness of the first metal coating in the present invention is 0.2 mm, that is, the thickness of the chip cavity is also 0.2 mm, which can be used to install a millimeter wave RF chip with a thickness greater than 0.3 mm. The use of this structure can reduce the height difference between the chip and the peripheral devices and the top bonding pad on the upper surface of the ceramic base, reduce the length of the bonding wire, and avoid the process operation difficulties caused by the excessive height difference of the bonding wire and the influence of the introduced parasitic parameters on the RF new energy; (3) The present invention provides a chip cavity groove, which penetrates the first metal plating layer. After the millimeter wave radio frequency chip is fixedly installed in the chip cavity groove, the chip contacts the ceramic base, thereby meeting the heat dissipation requirements of the chip itself; (4) The present invention adopts the BGA ball process, which has lower requirements for peripheral circuit board design and processing, while optimizing performance, reducing product use costs and reducing process assembly difficulty; (5) The present invention forms isolation through isolation copper pillars around the RF interface, and opens a chip cavity in the middle of the first metal plating layer to install the chip. By changing the size of the packaging cavity enclosed by the ceramic base, the ferrite frame and the cover plate to avoid the resonance frequency of the packaging cavity affecting the chip operating frequency, the problem of cavity resonance of the millimeter wave RF chip is solved.

[0011] In summary, the present invention improves the isolation between radio frequency interfaces, meets the heat dissipation requirements of the chip itself, and reduces the product use cost and process assembly difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Shown is a front structural schematic diagram of an embodiment of the present invention; Figure 2 The embodiment of the present invention is shown Figure 1 Schematic diagram of the cross-section structure of the AA surface; Figure 3 The figure is a schematic diagram of the structure of the upper surface of the ceramic base according to an embodiment of the present invention; Figure 4 The figure is a schematic diagram of the structure of the lower surface of the ceramic base according to an embodiment of the present invention; Figure 5 The figure shows a schematic diagram of a radio frequency interface and a low frequency interface according to an embodiment of the present invention; Figure 6 The figure shows the simulation result of isolation between radio frequency interfaces according to an embodiment of the present invention; In the figure: 1. Ceramic base; 2. Fellable frame; 3. Cover; 4. BGA ball; 5. First metal coating; 6. Second metal coating; 7. Top bonding pad; 8. Bottom ball planting pad; 9. Solder mask area; 10. Chip cavity; 11. Isolation copper pillar; 12. Solder mask; 13. RF interface; 14. Low frequency interface. DETAILED DESCRIPTION

[0013] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0014] Embodiment A millimeter wave radio frequency chip BGA packaging tube shell like Figure 1 As shown, this embodiment is a millimeter wave radio frequency chip BGA packaging tube shell, including a ceramic base 1, a Kovar frame 2, a cover plate 3 and a BGA ball 4; wherein the ceramic base 1 adopts LTCC, and the Kovar frame 2 and the cover plate 3 both adopt Kovar alloy.

[0015] like Figures 2 to 4 As shown, the upper surface of the ceramic base 1 is plated with a first metal coating 5, the thickness of the first metal coating 5 is 0.2 mm, and the lower surface of the ceramic base 1 is plated with a second metal coating 6; wherein the first metal coating 5 is etched with a top bonding pad 7 around it, and the top bonding pad 7 penetrates the first metal coating 5, and the second metal coating 6 is etched with a bottom ball planting pad 8 around it, and the bottom ball planting pad 8 penetrates the second metal coating 6, and the top bonding pad 7 and the bottom ball planting pad 8 are respectively arranged in a one-to-one correspondence; a through hole is provided on the ceramic base 1, and a copper column for connecting the corresponding top bonding pad 7 and the bottom ball planting pad 8 is provided in the through hole.

[0016] In this embodiment, the cuttable frame 2 is fixed at the edges of the upper surface of the first metal coating 5, the cover plate 3 is encapsulated on the top of the cuttable frame 2, and a circle of solder resist area 9 is provided on the upper surface of the first metal coating 5 near the inner side of the cuttable frame 2. By setting the solder resist area 9, the solder can be prevented from flowing into the upper surface of the ceramic base 1 when welding the cuttable frame 2.

[0017] A chip cavity 10 for installing a millimeter-wave RF chip is provided in the middle of the first metal coating 5. Since the thickness of the first metal coating 5 is 0.2 mm, the height of the chip cavity 10 is also 0.2 mm. The chip cavity 10 can be used to install a millimeter-wave RF chip with a thickness greater than 0.3 mm. The use of this structure can reduce the height difference between the chip and the peripheral components and the top bonding pad 7 on the upper surface of the ceramic base 1, reduce the length of the bonding wire, and avoid the process operation difficulties caused by the excessive height difference of the bonding wire and the influence of the introduced parasitic parameters on the RF performance.

[0018] Isolation copper pillars 11 are provided around the upper surface of the first metal coating 5, and the isolation copper pillars 11 are distributed in parallel on both sides of the top bonding pad 7 to realize the RF interface to radiate signals in the packaging cavity formed by the ceramic base 1, the ferrite frame 2 and the cover plate 3 and reduce the influence of the RF interface on the RF interface by the RF signal interference in the packaging cavity. The height of the isolation copper pillar 11 is 0.8 mm, the upper end of the isolation copper pillar 11 does not contact the lower surface of the cover plate 3, and the distance between the upper end of the isolation copper pillar 11 and the lower surface of the cover plate 3 is less than 0.1 mm; the number and spacing of the isolation copper pillars 11 can be specifically set according to the frequency of use. In this embodiment, the isolation copper pillars 11 are arranged close to the top bonding pad 7 and distributed on both sides of the top bonding pad 7.

[0019] In this embodiment, a solder resist layer 12 is provided on the lower surface of the second metal plating layer 6, and BGA balls 4 are welded on the solder resist layer 12. The horizontal and vertical spacings of the BGA balls 4 are both 0.8 mm. The BGA balls 4 form twelve RF interfaces 13 and twelve low-frequency interfaces 14. Figure 5 shown.

[0020] During packaging of this embodiment, the millimeter wave radio frequency chip is first installed and fixed in the chip cavity 10, and then after the chip and the peripheral circuit are assembled, the cover plate 3 is sealed on the top of the calender frame 2 using parallel seam welding.

[0021] like Figure 6 The figure shows the simulation result of the isolation between adjacent RF interfaces of this embodiment. According to the simulation results, within the simulation range of the DC-50GHz frequency band, the isolation between RF interfaces of this embodiment is >60dB. This result meets the working requirements of the millimeter-wave RF chip, and can avoid the influence of the packaging cavity on the chip indicators in the RF chip packaging test, which is conducive to promoting the application and promotion of RF chips, especially millimeter-wave RF chips.

[0022] It should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A millimeter wave radio frequency chip BGA packaging tube shell, characterized in that: Including ceramic base, Kovar frame, cover plate and BGA ball; The upper surface of the ceramic base is plated with a first metal coating, the lower surface of the ceramic base is plated with a second metal coating, the first metal coating is etched with a top bonding pad around it, the second metal coating is etched with a bottom ball planting pad around it, and the top bonding pad and the bottom ball planting pad are respectively arranged in a one-to-one correspondence; the ceramic base is provided with a through hole, and a copper column for connecting the corresponding top bonding pad and the bottom ball planting pad is provided in the through hole; The kovable frame is fixed at the edges around the upper surface of the first metal coating, the cover plate is encapsulated on the top of the kovable frame, a chip cavity is opened in the middle of the first metal coating and penetrates the first metal coating for installing a millimeter wave RF chip, isolation copper columns are arranged around the upper surface of the first metal coating, the upper end of the isolation copper column does not contact the lower surface of the cover plate, and the distance between the upper end of the isolation copper column and the lower surface of the cover plate is less than 0.1mm; the lower surface of the second metal coating is provided with a solder resist layer, and the BGA ball is welded to the lower surface of the solder resist layer.

2. The millimeter wave radio frequency chip BGA packaging tube shell according to claim 1, characterized in that: The horizontal spacing and vertical spacing of the BGA balls are both 0.8 mm.

3. The millimeter wave radio frequency chip BGA packaging tube shell according to claim 1, characterized in that: A circle of solder resist area is arranged on the upper surface of the first metal plating layer close to the inner side of the kovable frame.

4. The millimeter wave radio frequency chip BGA packaging tube shell according to claim 1, characterized in that: The thickness of the first metal plating layer is 0.2 mm, and the height of the isolation copper column is 0.8 mm.

5. The millimeter wave radio frequency chip BGA packaging tube shell according to claim 1, characterized in that: The BGA balls form twelve radio frequency interfaces and twelve low frequency interfaces.

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