BGA type SiP packaging structure based on defected ground structure and high-resistance line design method thereof

Abstract

The invention relates to the field of microwave and millimeter wave circuits, and provides a high-resistance line design method based on a BGA type SiP packaging structure of a defected ground structure, and the design method comprises the steps: removing a part of large-area metal ground of a BOTTOM layer in the BGA type SiP packaging structure, and enabling the lower reference ground of an RF layer radio frequency strip line to be a TOP layer of a PCB composite substrate. According to the method, the defected ground structure is designed on the BOTTOM layer, so that the radio frequency strip line with higher characteristic impedance can be realized on the premise that the size and the thickness of the SiP packaging structure are not additionally increased, the process processing capability is kept unchanged and the wiring space is not influenced.

Description

Technical Field

[0001] This invention relates to the field of microwave and millimeter-wave circuits, and more specifically, to a defect-ground structure BGA (Ball Grid Array) type SiP package structure and its high-resistivity line design method. Background Technology

[0002] Currently, defective ground technology is mostly used in the design of filters, couplers, and power dividers. There are few cases of using defective ground in the design of transmission structures such as horizontal transitions and vertical transitions. Chinese patent with publication number CN107834233A discloses a vertical transition structure, specifically describing a method of using a defective ground structure to reduce parasitic capacitance effects to improve the vertical transition performance of the millimeter-wave band. However, this method does not involve the design method of high-impedance lines in the transition structure, and since a defective structure needs to be manufactured on the ground plane, it will cause changes in the ground plane, which will affect the wiring density. Summary of the Invention

[0003] The present invention aims to provide a defect-ground structure-based BGA-type SiP package structure and its high-resistivity line design method to solve the above-mentioned problems.

[0004] In a first aspect, the present invention provides a high-resistivity line design method based on a defective ground structure BGA-type SiP package structure, comprising: In the BGA-type SiP package structure, a large area of ​​the BOTTOM layer is removed, so that the lower reference ground of the RF layer radio frequency strip is the TOP layer of the PCB composite substrate.

[0005] Furthermore, the BOTTOM layer typically includes RF signal pads, control signal pads, and a large area of ​​metal ground; the removed portion of the large area of ​​metal ground in the BOTTOM layer does not include the area near the RF signal pads.

[0006] Furthermore, the BGA-type SiP package structure includes several alternating layers of SiP metal layers and SiP substrate dielectric. Below the alternating portions, a SiP metal layer and a SiP solder mask layer are sequentially used to solder BGA solder balls, which are then connected to the PCB composite substrate through the BGA solder balls. The bottom three layers of the SiP metal layers are, in order, a GND layer, an RF layer, and a BOTTOM layer.

[0007] Furthermore, the GND layer and the BOTTOM layer are connected by metallized vias.

[0008] Furthermore, the PCB composite substrate includes a superimposed PCB metal layer and a PCB dielectric layer.

[0009] Secondly, the present invention provides a defect-ground structure BGA-type SiP package structure, comprising several alternating layers of SiP metal layers and SiP substrate dielectric, with BGA solder balls soldered to the bottom of the alternating portions through a SiP metal layer and a SiP solder mask layer, and connected to the PCB composite substrate through the BGA solder balls; the bottom three layers of the SiP metal layers are, in order, a GND layer, an RF layer and a BOTTOM layer. The large area of ​​the BOTTOM layer has a hollowed-out region, so that the lower reference ground of the RF layer radio frequency strip is the TOP layer of the PCB composite substrate.

[0010] Furthermore, the GND layer and the BOTTOM layer are connected by metallized vias.

[0011] Furthermore, the PCB composite substrate includes a superimposed PCB metal layer and a PCB dielectric layer.

[0012] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: This invention provides a method for achieving higher characteristic impedance RF striplines by designing a defective ground structure in the BOTTOM layer, without increasing the size and thickness of the SiP package structure, maintaining the same processing capability, and without affecting the wiring space. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a common BGA-type SiP packaging structure and a PCB composite substrate stack-up.

[0014] Figure 2 This is a top view of the BOTTOM layer and RF layer radio frequency stripline of the defective ground structure SiP package structure in an embodiment of the present invention.

[0015] Figure 3 The figure shows the simulation results of the characteristic impedance of a 0.1mm linewidth transmission line in a common BGA-type SiP package structure.

[0016] Figure 4 This is a simulation result of the characteristic impedance of a 0.1mm linewidth transmission line based on a defective ground structure SiP package structure in an embodiment of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0019] Example Figure 1 This diagram illustrates a common BGA-type SiP package structure and its stack-up on a PCB composite substrate. The BGA-type SiP package structure comprises several alternating layers of SiP metal layers and SiP substrate dielectric. Below the alternating layers, a further SiP metal layer and a SiP solder mask layer are used to solder BGA solder balls, which are then connected to the PCB composite substrate. The PCB composite substrate comprises stacked PCB metal layers and PCB dielectric layers. The bottom three layers of the SiP metal layers are, in order, the GND layer, the RF layer, and the BOTTOM layer. The RF layer houses the radio frequency (RF) stripline. The upper and lower ground planes for the RF stripline are the GND layer and the BOTTOM layer, respectively. The GND layer and the BOTTOM layer are connected via metallized vias to ensure the continuity of the RF ground plane. The BOTTOM layer typically includes RF signal pads, control signal pads, and a large area of ​​ground. The large area of ​​ground is separated from the BGA solder balls by solder mask. Generally, except for the area near the RF signal pads, the large area of ​​ground can be removed according to actual design needs.

[0020] Therefore, the high impedance line design method based on the defective ground structure BGA SiP package structure provided by the present invention is as follows: In the BGA SiP package structure, a large area of ​​the BOTTOM layer is removed, so that the lower reference ground of the RF layer radio frequency strip is the TOP layer (i.e., the PCB metal layer) of the PCB composite substrate. Figure 2 This is a top view of the BOTTOM layer and RF layer radio frequency stripline of the SiP package structure based on the defective ground structure. After removing a large area of ​​metal ground in the BOTTOM layer, there are no BGA solder balls in this area. Therefore, the lower reference ground of the RF layer radio frequency stripline changes from the BOTTOM layer of the SiP package structure to the TOP layer of the PCB composite substrate. Thus, the thickness of the lower dielectric layer of the RF layer radio frequency stripline is indirectly increased without increasing the overall product thickness. At the same time, since air has the lowest dielectric constant, the equivalent dielectric constant of the lower dielectric layer of the RF layer radio frequency stripline is also reduced, ultimately achieving the goal of higher characteristic impedance under the same linewidth conditions.

[0021] Therefore, the defect-based BGA-type SiP package structure designed based on the above design method is roughly similar to the common BGA-type SiP package structure, which includes several alternating layers of SiP metal layers and SiP substrate dielectric. Below the alternating sections, a SiP metal layer and a SiP solder mask layer are sequentially soldered to BGA solder balls, which are then connected to the PCB composite substrate. The bottom three layers of the SiP metal layers are, in order, the GND layer, the RF layer, and the BOTTOM layer. The difference is that the large area of ​​the BOTTOM layer has a cutout region, so that the reference ground below the RF layer radio frequency strip is the TOP layer of the PCB composite substrate.

[0022] Taking a typical stack-up of an HTCC (High Temperature Co-fired Ceramic) SiP package structure as an example, assuming the dielectric constant of HTCC is 9.2 and the dielectric thickness of a single-layer ceramic substrate is 0.3 mm, due to the high dielectric constant of ceramic, when both the upper and lower dielectric layers of the RF stripline are 0.3 mm thick ceramic, the 50 ohm transmission line width is approximately 0.1 mm. Simulation results are shown below. Figure 3 When using the high-resistivity line design method based on the defective ground structure BGA-type SiP package structure proposed in this invention, assuming the height of the BGA solder ball is 0.4mm, the upper dielectric layer of the RF layer radio frequency stripline remains unchanged at 0.3mm thick ceramic, and the lower dielectric layer is 0.3mm ceramic + 0.4mm air. At this time, the line width remains unchanged at 0.1mm, and the characteristic impedance increases from 50 ohms to 59 ohms. However, if the defective ground method is not used, to achieve a transmission line with a characteristic impedance of 59 ohms, the line width needs to be reduced to 0.06mm, which will lead to a sharp increase in processing difficulty.

[0023] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-resistivity line design method based on a defective ground structure BGA-type SiP package structure, characterized in that, include: In the BGA-type SiP package structure, a large area of ​​the BOTTOM layer is removed, so that the lower reference ground of the RF layer radio frequency strip is the TOP layer of the PCB composite substrate.

2. The high-resistivity line design method based on defective ground structure BGA-type SiP package structure according to claim 1, characterized in that, The BOTTOM layer typically includes RF signal pads, control signal pads, and a large area of ​​metal ground; the removed portion of the BOTTOM layer's large area of ​​metal ground does not include the area near the RF signal pads.

3. The high-resistivity line design method based on a defective ground structure BGA-type SiP package structure according to claim 1, characterized in that, The BGA-type SiP package structure includes several alternating layers of SiP metal layers and SiP substrate dielectric. Below the alternating parts, a SiP metal layer and a SiP solder mask layer are sequentially soldered to BGA solder balls, which are then connected to the PCB composite substrate through the BGA solder balls. The bottom three layers of the SiP metal layers are, in order, the GND layer, the RF layer, and the BOTTOM layer.

4. The high-resistivity line design method based on defective ground structure BGA-type SiP package structure according to claim 2, characterized in that, The GND layer and BOTTOM layer are connected by metallized vias.

5. The high-resistivity line design method based on a defective ground structure BGA-type SiP package structure according to claim 1, characterized in that, The PCB composite substrate includes a superimposed PCB metal layer and a PCB dielectric layer.

6. A defect-ground-based BGA-type SiP packaging structure, characterized in that, It includes several alternating layers of SiP metal layers and SiP substrate dielectric. Below the alternating parts, a SiP metal layer and a SiP solder mask layer are sequentially soldered to BGA solder balls, which are then connected to the PCB composite substrate through the BGA solder balls. The bottom three layers of the SiP metal layers are, in order, GND layer, RF layer and BOTTOM layer. The large area of ​​the BOTTOM layer has a hollowed-out region, so that the lower reference ground of the RF layer radio frequency strip is the TOP layer of the PCB composite substrate.

7. The defect-ground-based BGA-type SiP packaging structure according to claim 6, characterized in that, The GND layer and BOTTOM layer are connected by metallized vias.

8. The defect-ground-based BGA-type SiP packaging structure according to claim 6, characterized in that, The PCB composite substrate includes a superimposed PCB metal layer and a PCB dielectric layer.

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