BGA ball transition structure for interconnection of FCBGA packaging substrate and PCB and application of BGA ball transition structure

Abstract

The invention discloses an FCBGA packaging substrate and PCB interconnection BGA ball transition structure and application thereof.The structure mainly comprises a packaging substrate, a PCB and a BGA ball array connected between the packaging substrate and the PCB, the packaging substrate comprises a strip line and a BGA ball conversion structure, the PCB comprises a GCPW and a BGA ball conversion structure, the packaging substrate and the PCB are connected with respective conversion structure interfaces through the BGA ball array, and the BGA ball array is connected with the GCPW and the BGA ball conversion structure. And millimeter wave signal transmission between the packaging substrate and the PCB is completed. Compared with the prior art, the structure is simple, the occupied space is small, machining and implementation are easy, through the strip line-BGA ball-GCPW transition structure, good signal transmission between the FCBGA packaging substrate and the PCB is achieved, the defects that in the prior art, BGA ball connection loss is large, and the transmission bandwidth is narrow are overcome, and the service life of the FCBGA packaging substrate is prolonged. And the FCBGA packaging substrate has a good application prospect in the aspect of connection between the FCBGA packaging substrate and the PCB in the millimeter wave frequency band.

Description

Technical Field

[0001] The present application belongs to the field of millimeter wave technology, and specifically relates to a BGA ball transition structure for interconnecting an FCBGA packaging substrate with a PCB and its application. Background Art

[0002] Millimeter wave: Electromagnetic waves with a wavelength of 1 to 10 mm are called millimeter waves. They are in the wavelength range where microwaves and far-infrared waves overlap, so they have the characteristics of both spectra. Millimeter waves have extremely wide bandwidths. Compared with lasers, the propagation of millimeter waves is much less affected by climate and can be considered to have all-weather characteristics. Compared with microwaves, the size of millimeter wave components is much smaller; therefore, millimeter wave systems are easier to miniaturize. Millimeter waves are of great significance in communications, radar, guidance, remote sensing technology, radio astronomy, clinical medicine and spectroscopy.

[0003] With the rapid development of the semiconductor industry and the integrated circuit industry, millimeter-wave chip packaging technology has gradually become a frontier research field, and millimeter-wave signal transmission technology is a very critical part of it.

[0004] At present, the transmission of millimeter wave signals between the chip FCBGA package substrate and the PCB is completed through BGA balls. Since the impact of BGA balls on the transmission line becomes more and more obvious as the frequency increases, it is necessary to perform impedance matching on the BGA balls. Common matching methods include using quarter-wavelength impedance transformers and quasi-coaxial structures, but these methods can only achieve general matching effects within a narrow frequency band, which is not conducive to broadband and low-loss transmission of millimeter wave signals between the FCBGA package substrate and the PCB. Summary of the invention

[0005] In view of the above problems, the present application provides a BGA ball transition structure for interconnecting an FCBGA packaging substrate and a PCB, which can overcome the current shortcomings of large transmission loss and narrow transmission bandwidth of millimeter wave signals between the chip FCBGA packaging substrate and the PCB, and realize good transmission of signals between the FCBGA packaging substrate and the PCB.

[0006] In a first aspect, the present application provides a BGA ball transition structure for interconnecting an FCBGA packaging substrate with a PCB, comprising: a packaging substrate, a BGA ball array and a PCB, wherein the packaging substrate is provided with a strip line, a strip line matching segment, a disc transition structure, a BGA ball packaging pad connected in sequence, and a packaging substrate shielding hole arranged around the strip line, the strip line matching segment, the disc transition structure, and the BGA ball packaging pad; the PCB is provided with a BGA ball PCB pad, a GCPW matching segment, a GCPW connected in sequence, and a PCB shielding hole arranged around the BGA ball PCB pad, the GCPW matching segment, and the GCPW semi-enclosed; the BGA ball array is vertically interconnected with the packaging substrate and the PCB respectively up and down, the BGA ball array is connected to the packaging substrate by ball planting, and the BGA ball array is connected to the PCB by welding; the central BGA ball of the BGA ball array close to the GCPW side is connected to the BGA ball packaging pad and the BGA ball PCB pad respectively up and down, and the BGA ball array is provided with at least 4 BGA balls; the strip line is parallel to the GCPW transmission direction, and points in opposite directions with the BGA ball packaging pad as the center.

[0007] The BGA ball packaging pad is arranged close to the edge of one side of the packaging substrate, the strip line and the GCPW extend to the packaging substrate and the edge of the PCB respectively, and the diameter of the BGA ball packaging pad is larger than the diameter of the BGA ball.

[0008] The strip line, strip line matching section, and disk transition structure are formed by digging out part of the metal of the inner floor of the packaging substrate, and keeping a gap with the ground plate on the same layer; the BGA ball packaging pad is formed by digging out part of the metal of the surface layer of the floor close to one side of the PCB on the packaging substrate; the BGA ball PCB pad, GCPW matching section, and GCPW are formed by digging out part of the metal of the surface layer of the floor close to one side of the packaging substrate on the PCB, and keeping a gap with the ground plate on the same layer.

[0009] The line width of the strip line and the strip line matching section is not less than 20um, and the gap with the ground plane on the same layer is not less than 20um.

[0010] In some embodiments, the disk transition structure is provided with an outer disk and a plurality of transition metal holes distributed on the outer disk, the outer disk is connected to the BGA ball package pad directly below through the transition metal holes, and the transition metal holes are distributed around the center of the BGA ball package pad.

[0011] There is at least one transition metal hole.

[0012] In some embodiments, the package substrate shielding holes and the PCB shielding holes are both metallized holes, and the metallized holes respectively connect the three-layer metal floor on the package substrate close to the PCB side and the two-layer metal floor on the PCB close to the package substrate side.

[0013] The metallized holes may be copper metallized holes.

[0014] In some embodiments, the strip line is connected to the disc transition structure through a strip line matching segment, and the disc transition structure is vertically connected to the BGA ball packaging pad to realize a conversion structure for transmission from the strip line to the BGA ball.

[0015] In some implementations, the GCPW is connected to the BGA ball PCB pad via a GCPW matching segment to implement a conversion structure for transmission from the GCPW to the BGA ball.

[0016] In some embodiments, the GCPW matching section is provided with a first matching section and a second matching section connected to each other, the first matching section and the second matching section have different characteristic impedances, the first matching section is connected to the BGA ball PCB pad, and the second matching section is connected to the GCPW.

[0017] In some embodiments, the stripline, stripline matching segment, disc transition structure and BGA ball package pad are all tightly surrounded by the package substrate shielding hole; the BGA ball PCB pad, GCPW matching segment and GCPW are all tightly surrounded by the PCB shielding hole.

[0018] In some embodiments, a stacking hole layer is provided on one surface of the PCB side of the shielding hole of the packaging substrate, the packaging substrate shielding hole and the shielding stacking hole of the packaging substrate are respectively located in two dielectric layers adjacent to the strip line, and the shielding stacking hole is located in the dielectric layer close to the BGA ball side, and the packaging substrate shielding hole is located in the dielectric layer away from the BGA ball side, the packaging substrate shielding hole and the shielding stacking hole are aligned one by one in the center, and the shielding stacking hole is a metallized hole.

[0019] In some embodiments, the package substrate shielding holes and the PCB shielding holes are arranged with a minimum center spacing between holes and are close to the edge of the ground plane with a minimum spacing between the center of the shielding hole and the edge of the ground plane.

[0020] In a second aspect, the present application provides an application of a BGA ball transition structure for interconnecting an FCBGA packaging substrate and a PCB, which includes the above-mentioned structure for transmission of millimeter wave signals.

[0021] Beneficial effects of the present application: The transition structure of the invention mainly includes a packaging substrate, a PCB and a BGA ball array connected between boards. The packaging substrate includes a stripline and a BGA ball conversion structure, and the PCB includes a GCPW (grounded coplanar waveguide) and a BGA ball conversion structure. The packaging substrate and the PCB are connected to their respective conversion structure interfaces through the BGA ball array to complete the millimeter wave signal transmission between the packaging substrate and the PCB. Compared with the prior art, the present invention has a simple structure, occupies a small space and is easy to process and realize. Through the transition structure of the stripline-BGA ball-GCPW, a good transmission of signals between the FCBGA packaging substrate and the PCB is achieved, solving the shortcomings of the previously existing BGA ball connection, such as large loss and narrow transmission bandwidth; the loss of the traditional BGA ball connection structure is greater than 2dB, and the transmission bandwidth is less than 10%. In the 77GHz frequency band, the insertion loss of the BGA ball transition structure is less than 1.2dB, and the 15dB return loss bandwidth is about 12%; it has good application prospects in the connection between the FCBGA packaging substrate and the PCB in the millimeter wave frequency band.

[0022] The present invention proposes a BGA ball transition structure for interconnecting an FCBGA package substrate and a PCB, which has a simple structure, occupies a small space and is easy to process and realize. The disc transition structure improves the impedance continuity of the connection between the strip line and the BGA ball package pad, can reduce signal reflection, and make the 15dB return loss bandwidth of the overall structure reach 12%; the transition structure is surrounded by shielding holes, which ensures that the multi-layer floor is well connected and can reduce the leakage of signal energy.

[0023] The present invention realizes good signal interconnection between the FCBGA packaging substrate and the PCB through the connection between the stripline, the stripline matching segment, the disk transition structure, the BGA ball array, the GCPW matching segment and the GCPW, solves the previously existing problems of large transmission loss and narrow transmission bandwidth, and shows excellent performance in the millimeter wave signal transmission structure.

[0024] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0026] Figure 1 This is a schematic structural diagram of a BGA ball transition structure according to some embodiments of the present application;

[0027] Figure 2 A schematic diagram of a partial structure of a BGA ball transition structure according to some embodiments of the present application;

[0028] Figure 3 A schematic diagram of a partial structure of a BGA ball transition structure according to some embodiments of the present application;

[0029] Figure 4 A schematic diagram of a PCB structure of a BGA ball transition structure according to some embodiments of the present application;

[0030] Figure 5 A schematic diagram of a partial structure of a BGA ball transition structure according to some embodiments of the present application;

[0031] Figure 6 A schematic diagram of a partial structure of a BGA ball transition structure according to some embodiments of the present application;

[0032] Figure 7 A schematic diagram of a partial structure of a packaging substrate of a BGA ball transition structure according to some embodiments of the present application;

[0033] Figure 8 A schematic diagram of a partial structure of a packaging substrate of a BGA ball transition structure according to some embodiments of the present application;

[0034] Fig. 9 Schematic diagram of the packaging substrate and BGA ball array structure of the BGA ball transition structure of some embodiments of the present application.

[0035] The reference numerals in the specific implementation manner are as follows:

[0036] Package substrate 1; stripline 11; stripline matching section 12; disc transition structure 13; outer disc 131; transition metal hole 132; BGA ball package pad 14; package substrate shielding hole 15; shielding stacking hole 16; solder mask 17; BGA ball array 2; center BGA ball 21; PCB 3; BGA ball PCB pad 31; GCPW matching section 32; first matching section 321; second matching section 322; GCPW 33; PCB shielding hole 34. DETAILED DESCRIPTION

[0037] The following embodiments of the technical solution of the present application will be described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0039] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0040] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0041] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0042] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0043] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0044] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0045] Reference Figure 1-9 A BGA ball transition structure for interconnecting an FCBGA packaging substrate and a PCB, comprising: a packaging substrate 1, a BGA ball array 2 and a PCB 3, wherein the packaging substrate 1 is provided with a stripline 11, a stripline matching section 12, a disc transition structure 13, a BGA ball packaging pad 14 connected in sequence, and a packaging substrate shielding hole 15 semi-enclosed around the stripline 11, the stripline matching section 12, the disc transition structure 13, and the BGA ball packaging pad 14; the PCB 3 is provided with a BGA ball PCB pad 31, a GCPW matching section 32, and a GCPW 33 connected in sequence, and a PCB shielding hole 34 semi-enclosed around the BGA ball PCB pad 31, the GCPW matching section 32, and the GCPW 33; the BGA ball array 2 is vertically interconnected with the packaging substrate 1 and the PCB 3 respectively from top to bottom, the BGA ball array 2 is connected to the packaging substrate 1 by ball planting, and the BGA ball array 2 is connected to the PCB 3 by welding; the BGA ball array 2 is close to the GCPW The central BGA ball 21 on the side of 33 is connected to the BGA ball package pad 14 and the BGA ball PCB pad 31 respectively, and the BGA ball array 2 is provided with at least 4 BGA balls; the strip line 11 is parallel to the transmission direction of GCPW 33, and points in the opposite direction with the BGA ball package pad 14 as the center.

[0046] The number of metal layers of the package substrate 1 and the number of metal layers of the PCB 3 vary according to the application, and are usually 2, 4, 6, or 8 layers. For example, in a transition structure where the package substrate 1 includes 3 metal layers and the PCB 3 includes 2 metal layers, in actual applications, the metal layers of the package substrate 1 will increase to 4, 6, or 8 layers on the side away from the PCB 3, and the PCB 3 will increase to 4, 6, or 8 layers on the side away from the package substrate 1. The model of this application only displays the metal layers related to the inventive structure, and the metal layers added in actual applications do not belong to this structure.

[0047] The stripline 11, the stripline matching section 12, and the disk transition structure 13 are connected as a whole with the same metal layer; the disk transition structure 13 and the BGA ball package pad 14 are connected through the transition metal hole 132 inside the substrate; the GCPW 33, the GCPW matching section 32, and the BGA ball PCB pad 31 are connected as a whole with the same metal layer.

[0048] The stripline 11, the stripline matching section 12, and the outer pad 131 are arranged on the middle metal layer of the package substrate 1, and keep a gap with the ground plate on the same layer; the BGA ball package pad 14 is arranged on the metal layer of the substrate closest to the PCB 3 side, and keeps a gap with the ground plate on the same layer.

[0049] Design requirements for stripline 11: Taking the stacked structure and packaging process of this model as an example, the line width is not less than 25um, the gap between the line and the ground plane on the same layer is not less than 25um, the shielding holes 15 of the packaging substrate are arranged on both sides of the stripline 11 with a minimum center spacing of 140um between holes, and the shielding hole center is close to the edge of the ground plane with a minimum spacing of 70um between the edge of the ground plane, and the shielding stacking hole 16 is aligned with the center of the shielding hole 15 of the packaging substrate up and down; the characteristic impedance of the stripline 11 is designed according to application requirements, such as 50Ω.

[0050] Stripline 11, taking the characteristic impedance requirement of stripline 11 of 50Ω as an example, if the dielectric constant of the packaging board is 3.12, the loss tangent is 0.0043, the dielectric thickness below the stripline 11 is 30um, the dielectric thickness above the stripline 11 is 200um, the metal layer thickness is 18um, and the metal conductivity is 5.8e7S / m, the data is input into simulation software such as CST for modeling. The simulation optimization shows that when the width of the central conductor of the stripline 11 is 30um and the gap between the central conductor and the same floor is 44um, the characteristic impedance of about 50Ω can be met.

[0051] The diameter of the BGA ball is selected according to demand. Taking a BGA ball with a diameter of 350um as an example, according to the packaging process, the window diameter of the solder mask layer 17 of the BGA ball packaging pad 14 can be selected to be 85% of the BGA ball diameter, that is, approximately 300um. The diameter of the BGA ball packaging pad 14 can be 65um larger than the window diameter, so the diameter of the BGA ball packaging pad 14 can be set to 365um.

[0052] GCPW 33, taking the characteristic impedance requirement of GCPW 33 of 50Ω as an example, when the dielectric constant of PCB 3 board is 3.48, the loss tangent is 0.0037, the PCB 3 dielectric thickness is 0.102mm, the metal layer thickness is 50um, and the metal conductivity is 5.8e7S / m, the data is input into simulation software such as CST. The simulation optimization shows that when the width of the GCPW 33 center conductor is 0.174mm and the gap between the center conductor and the same layer of the floor is 0.156mm, the characteristic impedance is about 50Ω.

[0053] In order to make the BGA ball simulation model close to the actual shape after soldering, the diameter of the BGA ball PCB pad 31 is set to be the same as the window diameter of the solder mask layer 17 of the package substrate 1, that is, 300um, so that the diameters of the upper and lower surfaces of the BGA ball are as consistent as possible.

[0054] The transition metal hole 132 can have a numerical range of 1, 2, 3, or 4. There is a minimum processing spacing between the holes, and there is also a minimum processing spacing between the holes and the edge of the outer disk 131. The holes are evenly arranged around the center of the outer disk with the minimum rotation radius as the initial value, and the diameter of the outer disk 131 is the minimum value that can accommodate the selected number of holes. The appropriate number of holes, hole rotation radius, and hole position can be determined based on the simulation optimization results.

[0055] The number of BGA balls in the BGA ball array 2 is at least 4, and the arrangement is 3 BGA balls in the outer row and 1 BGA ball in the center of the inner row, the 3 BGA balls in the outer row are the BGA balls close to one side of the GCPW 33, and the center of the outer row is the center BGA ball 21. The number of BGA balls can be increased one by one based on this arrangement to form a larger array.

[0056] The center BGA ball 21 is connected to the BGA ball package pad 14 and the BGA ball PCB pad 31 at the top and bottom, respectively. The center BGA ball 21 is the outermost BGA ball, that is, close to the edge of the package substrate 1, reducing the impact of the package substrate 1 floor on the GCPW 33 and the GCPW matching section 32. The distance from the center BGA ball 21 to the edge of the package substrate 1 does not exceed the length of the GCPW matching section 32.

[0057] In practical applications, the stripline 11 structure is designed according to the characteristic impedance requirements and the material parameters of the package substrate 1; the size of the BGA ball package pad 14 is set according to the required BGA ball size; the length of the stripline matching section 12 is roughly calculated by one-quarter of the dielectric wavelength as an initial value, and the number and specific size of the stripline matching sections 12, the number of transition metal holes 132 of the disk transition structure 13, the rotation radius of the transition metal hole 132 around the center of the outer disk 131, the position of the transition metal hole 132, the distance between the outer disk 131 and the surrounding floor, and the distance between the BGA ball package pad 14 and the surrounding floor are all adjusted according to the simulated matching effect of the stripline 11 and the BGA ball.

[0058] Taking the transmission of a 77 GHz frequency signal as an example, when the dielectric constant of the plate is 3.12, the initial length value of the stripline matching segment 12 is calculated to be 0.55 mm according to the following formula.

[0059]

[0060] λ is one quarter of the wavelength of the medium, c is the speed of light in a vacuum, f is the frequency of the transmitted signal, and ε r is the dielectric constant.

[0061] Taking the matching of 50Ω stripline 11 as an example, the width of the stripline matching segment 12 takes the width of 50Ω stripline 11 30um as the initial value, and the spacing between the stripline matching segment 12 and the same-layer floor takes the spacing between 50Ω stripline 11 and the same-layer floor 44um as the initial value; the number of stripline matching segments 12 can be selected in the range of 1 and 2. When the matching effect of only one stripline matching segment 12 is poor, two stripline matching segments 12 are selected. Therefore, the number of stripline matching segments 12 is initially set to 1 segment.

[0062] The number of transition metal holes 132 can be selected in the range of 1, 2, 3, and 4. Taking a BGA ball with a diameter of 350um as an example, the number of transition metal holes 132 is 4 as the initial value. When the simulation matching of 4 holes is poor, 1, 2 or 3 holes are selected, and finally the optimal number of transition metal holes 132 is selected according to the simulation optimization results.

[0063] According to the stacked structure and packaging process of this model, the diameter of the transition metal hole 132 is 60um, the minimum spacing between the holes is 100um, and the minimum spacing between the hole center and the edge of the outer disk 131 is 50um. The four transition metal holes 132 are evenly arranged around the center of the outer disk 131 with 71um as the initial value of the rotation radius, and the center spacing of adjacent transition metal holes 132 is just about the minimum value of 100um. At this time, the minimum diameter of the outer disk 131 that can accommodate the four transition metal holes 132 is 242um. The four transition metal holes 132 are located in the axial direction of the strip line 11 with the centers of two transition metal holes 132 and the vertical direction of the axial direction of the strip line 11 as the initial position. The spacing between the outer disk 131 and the same floor is 44um, which is the gap between the 50Ω strip line 11 and the same floor. The spacing between the BGA ball package pad 14 and the same floor is also 44um, which is the gap between the 50Ω strip line 11 and the same floor.

[0064] The data was input into simulation software such as CST for modeling. After simulation optimization, it was found that when the number of stripline matching segments 12 was 1 and the number of transition metal holes 132 was 4, a better matching effect could be achieved. The length of the stripline matching segment 12 after simulation optimization (from the junction of the stripline 11 and the matching segment to the center of the outer disk 131) was 0.56mm, the width was 0.127mm, and the spacing between the matching segment and the same floor was 50um; the rotation radius of the optimized transition metal hole 132 was 80um, the hole position was still the initial position, and the diameter of the outer disk 131 was 260um; the spacing between the optimized outer disk 131 and the same floor was 94um; the spacing between the optimized BGA ball package pad 14 and the same floor was 81.2um.

[0065] If the BGA ball or the BGA ball package pad 14 has other sizes, one can also try to use 1, 2 or 3 transition metal holes 132 as the initial value for simulation optimization, and finally select the optimal structure.

[0066] According to the packaging process, the diameter of the package substrate shielding hole 15 is 80um, and the diameter of the shielding stacking hole 16 is 60um and aligned with the center of the package substrate shielding hole 15. The package substrate shielding hole 15 and the shielding stacking hole 16 are arranged around the structure with a minimum center spacing of 140um between the holes, and the minimum spacing between the center of the package substrate shielding hole 15 and the edge of the floor is 70um, close to the edge of the surrounding grounding floor, so as to achieve a tight encirclement of the strip line 11, the strip line matching section 12, the disc transition structure 13 and the BGA ball package pad 14.

[0067] In practical applications, the GCPW 33 structure is designed according to the characteristic impedance requirements and the PCB 3 material parameters; the size of the BGA ball PCB pad 31 is set according to the window size of the BGA ball solder mask layer 17; the length of a single GCPW matching section 32 is roughly calculated by a quarter of the dielectric wavelength as an initial value, and the number and specific size of the GCPW matching sections 32 and the spacing between the BGA ball PCB pad 31 and the surrounding floor are adjusted according to the simulated matching effect of the GCPW 33 and the BGA ball.

[0068] Taking the transmission signal frequency of 77 GHz as an example, when the dielectric constant of PCB 3 is 3.48, the initial length value of a single GCPW matching section 32 is calculated to be 0.52 mm according to the following formula.

[0069]

[0070] λ is one quarter of the wavelength of the medium, c is the speed of light in a vacuum, f is the frequency of the transmitted signal, and ε r is the dielectric constant.

[0071] The width of the GCPW matching section 32 takes the width of the 50Ω GCPW 33 as 0.174mm as the initial value, and the spacing between the GCPW matching section 32 and the same floor takes the spacing between the 50Ω GCPW 33 and the same floor as 0.156mm as the initial value; the number of GCPW matching sections 32 can be selected in the range of 1 and 2. When the matching effect of only one GCPW matching section 32 is poor, two GCPW matching sections 32 are selected, so the number of GCPW matching sections 32 is initially set to 1. The diameter of the BGA ball PCB pad 31 is set to be the same as the window diameter of the BGA ball solder mask 17, that is, 300um, and the spacing between the BGA ball PCB pad 31 and the same floor refers to the spacing between the 50Ω GCPW 33 and the same floor as 0.156mm as the initial value.

[0072] Input the data into simulation software such as CST. After simulation optimization, it is found that the matching effect of the GCPW matching segment 32 with one segment is poor. At this time, it is necessary to increase the number of GCPW matching segments 32 to two segments, namely the first matching segment 321 and the second matching segment 322. The initial values ​​of the sizes of the first matching segment 321 and the second matching segment 322 are the same as the initial values ​​when the GCPW matching segment 32 is one segment. After simulation optimization again, a better matching effect is achieved. The length of the first matching segment 321 after simulation optimization (from the junction of the first matching segment 321 and the second matching segment 322 to the center of the BGA ball PCB pad 31) is 0.53mm, the width is 0.127mm, and the spacing with the same floor is 0.1795mm; the length of the optimized second matching segment 322 is 0.53mm, the width is 0.232mm, and the spacing with the same floor is 0.127mm; the spacing between the optimized BGA ball PCB pad 31 and the same floor is 0.127mm.

[0073] According to the PCB 3 manufacturing process, a 0.15mm diameter via is used as the PCB shielding hole 34. The PCB shielding holes 34 are arranged around the structure with a minimum center spacing of 0.35mm between the holes, and the minimum spacing between the center of the PCB shielding hole 34 and the edge of the floor is 0.175mm, close to the edge of the surrounding ground floor, so as to achieve a tight encirclement of the BGA ball PCB pad 31, the GCPW matching section 32 and the GCPW 33.

[0074] The BGA ball package pad 14 is arranged near the edge of one side of the package substrate 1, and the strip line 11 and the GCPW 33 extend to the edge of the package substrate 1 and the PCB 3 respectively. The diameter of the BGA ball package pad 14 is larger than the diameter of the BGA ball. For example, taking a BGA ball with a diameter of 350um as an example, according to the packaging process, the window diameter of the solder resist layer 17 of the BGA ball package pad 14 can be selected as 85% of the BGA ball diameter, that is, about 300um. The diameter of the BGA ball package pad 14 can be 65um larger than the window diameter, so the diameter of the BGA ball package pad 14 can be set to 365um.

[0075] The strip line 11, the strip line matching section 12, and the outer plate 131 are formed by digging out part of the metal of the inner layer of the packaging substrate 1, and keeping a gap with the ground plate of the same layer; the BGA ball packaging pad 14 is formed by digging out part of the surface metal of the packaging substrate 1 close to the PCB 3 side; the BGA ball PCB pad 31, the GCPW matching section 32 and the GCPW 33 are formed by digging out part of the surface metal of the PCB 3 close to the packaging substrate 1 side, and keeping a gap with the ground plate of the same layer.

[0076] The line width of the strip line 11 and the strip line matching section 12 is not less than 20um, and the gap between them and the ground plane on the same layer is not less than 20um.

[0077] In some embodiments, the disc transition structure 13 is provided with an outer disc 131 and a plurality of transition metal holes 132 distributed on the outer disc 131 , and the outer disc 131 is connected to the BGA ball package pad 14 directly below through the transition metal holes 132 , and the transition metal holes 132 are evenly distributed around the center of the BGA ball package pad 14 .

[0078] The outer pad 131 and the BGA ball package pad 14 are two adjacent layers of metal in the substrate, and they are connected through a transition metal hole 132 inside the substrate.

[0079] There is at least one transition metal hole 132 .

[0080] In some embodiments, the package substrate shielding hole 15 and the PCB shielding hole 34 are both metallized holes, which respectively connect the three-layer metal floor on the package substrate 1 close to the PCB 3 side and the two-layer metal floor on the PCB 3 close to the package substrate 1 side.

[0081] The metallized holes may be copper metallized holes.

[0082] In some embodiments, the stripline 11 is connected to the disk transition structure 13 through the stripline matching segment 12, and the disk transition structure 13 is vertically connected to the BGA ball packaging pad 14 to realize a conversion structure for transmitting the stripline 11 to the BGA ball.

[0083] In some implementations, the GCPW 33 is connected to the BGA ball PCB pad 31 via the GCPW matching section 32 to implement a conversion structure for transmission from the GCPW 33 to the BGA ball.

[0084] In some embodiments, the GCPW matching section 32 is provided with a first matching section 321 and a second matching section 322 connected to each other, the first matching section 321 and the second matching section 322 have different characteristic impedances, the first matching section 321 is connected to the BGA ball PCB pad 31, and the second matching section 322 is connected to the GCPW 33.

[0085] The first matching section 321 and the second matching section 322 have different characteristic impedances, and both have lengths of one quarter of the medium wavelength of the transmission signal. Different widths represent different characteristic impedances.

[0086] In some embodiments, the stripline 11, the stripline matching segment 12, the disc transition structure 13 and the BGA ball package pad 14 are all tightly surrounded by the package substrate shielding hole 15; the BGA ball PCB pad 31, the GCPW matching segment 32 and the GCPW 33 are all tightly surrounded by the PCB shielding hole 34.

[0087] The package substrate shielding holes 15 and the PCB shielding holes 34 are arranged with a minimum center spacing between the holes and are close to the edge of the ground plane with a minimum spacing between the center of the shielding hole and the edge of the ground plane.

[0088] According to the processing technology of the package substrate 1, each thickness of the dielectric layer has a corresponding hole diameter, a minimum spacing between holes, and a minimum spacing between the hole and the edge of the metal layer.

[0089] The shielding holes are closely spaced to achieve the shielding effect that can be achieved by the minimum spacing corresponding to the hole.

[0090] The shielding hole diameter, the minimum spacing between holes, and the minimum spacing between the holes and the edge of the metal layer are determined according to the board factory process after selecting the material and thickness of the dielectric layer where the shielding holes are located. The shielding holes are closely arranged to maximize the shielding effect under the condition of a given minimum spacing between holes. The shielding holes are close to the edge of the floor to minimize the substrate area occupied by the overall structure.

[0091] In this embodiment, the shielding hole 15 of the package substrate has a diameter of 80 um, the minimum center spacing between holes is 40 um, the minimum spacing between the hole center and the edge of the metal layer is 70 um, and the shielding stacking hole 16 has a diameter of 60 um.

[0092] In this embodiment, the PCB shielding holes 34 have a diameter of 0.15 mm, a minimum center spacing between holes of 0.35 mm, and a minimum spacing between the hole center and the edge of the metal layer of 0.175 mm.

[0093] A stacked hole layer is provided on one surface of the PCB 3 of the package substrate shielding hole 15. The package substrate shielding hole 15 and the shielding stacked hole 16 of the package substrate 1 are respectively located in two dielectric layers adjacent to the strip line 11, and the shielding stacked hole 16 is located in the dielectric layer close to the BGA ball side, and the package substrate shielding hole 15 is located in the dielectric layer away from the BGA ball side. The package substrate shielding hole 15 and the shielding stacked hole 16 are aligned in center one by one, and the shielding stacked hole 16 is a metallized hole.

[0094] The metal layer of the package substrate 1 serves as a reference ground for the stripline 11, the stripline matching segment 12, the outer disk 131 and the BGA ball package pad 14 to improve the shielding performance; the dielectric layer of the package substrate 1 serves as a filling medium between the stripline 11, the stripline matching segment 12, the outer disk 131 and the reference ground, and as a filling medium between the outer disk 131 and the BGA ball package pad 14.

[0095] In different applications, the thickness of the dielectric layer of the package substrate 1 may be different, and the corresponding aperture of the shielding stacking hole 16 may be smaller than, equal to, or larger than the aperture of the shielding hole 15 of the package substrate.

[0096] A BGA ball transition structure for interconnecting an FCBGA packaging substrate with a PCB can be used for transmission of millimeter wave signals.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A BGA ball transition structure for interconnecting a FCBGA package substrate with a PCB, characterized in that: include: A packaging substrate, a BGA ball array and a PCB, wherein the packaging substrate is provided with a strip line, a strip line matching section, a disc transition structure, a BGA ball packaging pad connected in sequence, and a packaging substrate shielding hole arranged around the strip line, the strip line matching section, the disc transition structure, and the BGA ball packaging pad; the PCB is provided with a BGA ball PCB pad, a GCPW matching section, a GCPW connected in sequence, and a PCB shielding hole arranged around the BGA ball PCB pad, the GCPW matching section, and the GCPW semi-enclosed; the BGA ball array is vertically interconnected with the packaging substrate and the PCB respectively up and down, the BGA ball array is connected to the packaging substrate by ball planting, and the BGA ball array is connected to the PCB by welding; the central BGA ball of the BGA ball array close to the GCPW side is connected to the BGA ball packaging pad and the BGA ball PCB pad respectively up and down, and the BGA ball array is provided with at least 4 BGA balls; the strip line is parallel to the GCPW transmission direction, and points in opposite directions with the BGA ball packaging pad as the center.

2. The BGA ball transition structure for interconnecting the FCBGA package substrate and the PCB as claimed in claim 1, characterized in that: The BGA ball packaging pad is arranged close to the edge of one side of the packaging substrate, the strip line and the GCPW extend to the packaging substrate and the edge of the PCB respectively, and the diameter of the BGA ball packaging pad is larger than the diameter of the BGA ball.

3. The BGA ball transition structure for interconnecting the FCBGA package substrate and the PCB as claimed in claim 1, characterized in that: The strip line, strip line matching section, and outer plate are formed by digging out part of the metal of the inner layer of the packaging substrate, and keeping a gap with the ground plate of the same layer; the BGA ball packaging pad is formed by digging out part of the surface metal of the packaging substrate close to the PCB side; the BGA ball PCB pad, GCPW matching section, and GCPW are formed by digging out part of the surface metal of the PCB close to the packaging substrate side, and keeping a gap with the ground plate of the same layer.

4. The BGA ball transition structure for interconnecting the FCBGA package substrate and the PCB as claimed in claim 1, characterized in that: The line width of the strip line and the strip line matching section is not less than 20um, and the gap with the ground plate on the same layer is not less than 20um; the shielding holes of the package substrate and the shielding holes of the PCB are arranged with the minimum center spacing between the holes and close to the edge of the ground plate with the minimum spacing between the center of the shielding hole and the edge of the floor.

5. The BGA ball transition structure for interconnecting the FCBGA package substrate and the PCB as claimed in claim 1 or 3, characterized in that: The disc transition structure is provided with an outer disc and a plurality of transition metal holes distributed on the outer disc. The outer disc is connected to the BGA ball packaging pad directly below through the transition metal holes. The transition metal holes are distributed around the center of the BGA ball packaging pad. There is at least one transition metal hole.

6. The BGA ball transition structure for interconnecting the FCBGA package substrate and the PCB as claimed in claim 1 or 4, characterized in that: The package substrate shielding holes and the PCB shielding holes are both metallized holes, which respectively connect the three layers of metal floor on the package substrate close to the PCB side and the two layers of metal floor on the PCB close to the package substrate side.

7. The BGA ball transition structure for interconnecting the FCBGA package substrate and the PCB as claimed in claim 1 or 3, characterized in that: The GCPW matching section is provided with a first matching section and a second matching section connected to each other, the first matching section and the second matching section have different characteristic impedances, the first matching section is connected to the BGA ball PCB pad, and the second matching section is connected to the GCPW.

8. The BGA ball transition structure for interconnecting the FCBGA package substrate and the PCB as claimed in claim 1 or 3, characterized in that: The strip line, strip line matching section, disc transition structure and BGA ball package pad are all tightly surrounded by the package substrate shielding hole; the BGA ball PCB pad, GCPW matching section and GCPW are all tightly surrounded by the PCB shielding hole.

9. The BGA ball transition structure for interconnecting the FCBGA package substrate and the PCB as claimed in claim 1 or 4, characterized in that: A stacking hole layer is provided on one surface of the PCB side of the packaging substrate shielding hole. The packaging substrate shielding hole and the shielding stacking hole of the packaging substrate are respectively located in two dielectric layers adjacent to the strip line, and the shielding stacking hole is located in the dielectric layer close to the BGA ball side, and the packaging substrate shielding hole is located in the dielectric layer away from the BGA ball side. The packaging substrate shielding hole and the shielding stacking hole are aligned in center one by one, and the shielding stacking hole is a metallized hole.

10. An application of a BGA ball transition structure for interconnecting an FCBGA packaging substrate and a PCB, wherein the structure as described in any one of claims 1 to 9 is used for transmission of millimeter wave signals.

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