CN222464922U - A PCB structure based on reducing BGA fan-out trace via crosstalk - Google Patents
A PCB structure based on reducing BGA fan-out trace via crosstalk Download PDFInfo
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- CN222464922U CN222464922U CN202420807342.3U CN202420807342U CN222464922U CN 222464922 U CN222464922 U CN 222464922U CN 202420807342 U CN202420807342 U CN 202420807342U CN 222464922 U CN222464922 U CN 222464922U
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Abstract
本实用新型涉及一种基于降低BGA扇出走线过孔串扰的PCB结构，表层板设有信号焊盘和地焊盘，信号焊盘底部连接信号过孔，地焊盘底部连接地过孔，信号过孔的中心轴偏离所述信号焊盘的中心点设置，且信号过孔的中心轴偏离信号焊盘的方向与该信号过孔上扇出走线的扇出方向相反。本实用新型的信号过孔偏盘设计，信号过孔的中心轴偏离信号焊盘的方向与扇出走线的扇出方向相反，增加了信号过孔与旁侧的地过孔之间的空间，增加了扇出走线的布线空间，进而实现扇出走线即使保持原有的线宽，也能够在密集的阵列焊盘区域内避开地过孔，扇出走线的线宽处处相等，不存在窄线段和宽限段的线宽突变，因此能够有效改善高频信号在扇出走线上的串扰。
The utility model relates to a PCB structure based on reducing the crosstalk of BGA fan-out routing vias, wherein a surface plate is provided with a signal pad and a ground pad, the bottom of the signal pad is connected to a signal via, the bottom of the ground pad is connected to a ground via, the central axis of the signal via is set away from the central point of the signal pad, and the direction in which the central axis of the signal via deviates from the signal pad is opposite to the fan-out direction of the fan-out routing on the signal via. The signal via of the utility model is designed to be biased toward the disk, and the direction in which the central axis of the signal via deviates from the signal pad is opposite to the fan-out direction of the fan-out routing, thereby increasing the space between the signal via and the ground via on the side, increasing the wiring space of the fan-out routing, and thus achieving that even if the fan-out routing maintains the original line width, it can avoid the ground via in a dense array pad area, the line width of the fan-out routing is equal everywhere, and there is no sudden change in the line width of the narrow line segment and the wide limit segment, thereby effectively improving the crosstalk of high-frequency signals on the fan-out routing.
Description
Technical Field
The utility model relates to the field of circuit boards, in particular to a PCB structure based on reduction of BGA fan-out wiring via crosstalk.
Background
Printed circuit boards (Printed Circuit Board, PCB boards), which are important components of the physical support and signal transmission of electronic products, are more concerned in industry with the passing Kong Chuanrao of fanning wires in BGA chip areas after the signal transmission rate is higher and higher, and the integrated electronic technology has been developed rapidly from fanning wires in the surface layer of the circuit board to fanning wires in holes in a disc.
The BGA chip is a ball grid array chip, a dense array bonding pad is arranged in a region of the circuit board corresponding to the BGA chip and comprises a signal bonding pad and a ground bonding pad, a through hole penetrating through an inner layer plate of the circuit board is arranged at the bottom of the bonding pad, the signal through hole and the ground through hole are respectively, and the central axis of the through hole is overlapped with the central point of the bonding pad. The surface layer fan-out wiring means that the wiring is arranged on the surface layer plate of the PCB and is connected with the signal bonding pad, and the hole fan-out wiring means that the wiring is arranged on the inner layer plate and is connected with the signal via hole.
Some inner-layer boards of the circuit board are also provided with fan-out wires (hereinafter referred to as fan-out wires) with holes in the board, one end of each fan-out wire is connected with a signal via hole, and the other end of each fan-out wire is outside the area of the fan-out BGA chip from the dense array bonding pads. If the wirings are a pair of differential wirings, one ends of the two fan-out wirings are connected to the adjacent pair of signal vias, the two fan-out wirings fan out in parallel from the gap between the dense ground vias, in order to avoid the ground vias, the wiring sections in the BGA chip area need to be small in line width, and the original line width is restored after reaching the outside of the BGA chip area, so that the fan-out wirings have different line widths, although the phenomenon of effectively avoiding the ground vias can be caused, impedance mutation is caused at the line width mutation position, and obvious crosstalk exists when high-frequency signals are transmitted on the fan-out wirings.
The problems are worth solving.
Disclosure of utility model
In order to solve the problem of crosstalk in high-frequency signal transmission of the conventional fan-out wiring in the disc, the utility model provides a PCB structure based on reducing BGA fan-out wiring via crosstalk.
The technical scheme of the utility model is as follows:
A PCB structure based on BGA fan-out wiring via crosstalk reduction comprises a multilayer circuit board with a surface plate, an inner plate and a bottom plate, wherein the surface plate is provided with a signal pad and a ground pad, the bottom of the signal pad is connected with the signal via, the bottom of the ground pad is connected with the ground via, the signal via is connected with a fan-out wiring on one of the inner plates, the central axis of the signal via deviates from the central point of the signal pad, the central axis of the signal via deviates from the direction of the signal pad and the fan-out direction of the fan-out wiring on the signal via are opposite, and the line width of the fan-out wiring is a fixed value.
The utility model according to the above scheme is characterized in that a first distance is provided between the center point of the signal pad and the center axis of the signal via, and the first distance is greater than zero and smaller than the radius of the signal pad.
Further, the first distance is in the range of 0 to 5 mils.
The utility model according to the above scheme is characterized in that the circuit board is provided with an anti-pad hollowed-out area, and the signal via hole is positioned in the anti-pad hollowed-out area.
Further, in the width direction of the anti-pad hollow region, the distance from one side of the signal via hole to the anti-pad hollow region is equal to the distance from the opposite side of the signal via hole to the anti-pad hollow region.
The utility model according to the above scheme is characterized in that the wirings are a pair of differential wires, and the line width of a single wiring of the differential wires is 4.5mil.
The present utility model according to the above aspect is characterized in that the center axis of the ground via is offset from the center point of the ground pad, and the center axis of the ground via adjacent to the fan-out trace is offset in a direction away from the fan-out trace.
Further, the circuit board anti-pad hollowed-out area is far away from the ground via hole on one side of the fanout line, and the center line of the circuit board anti-pad hollowed-out area is deviated towards the direction close to the anti-pad hollowed-out area.
Still further, a second distance is provided between a center point of the ground pad and a center axis of the ground via, the second distance being greater than zero and less than a radius of the ground pad.
Further, the second distance is in the range of 0 to 4 mils.
The utility model according to the scheme has the beneficial effects that:
According to the utility model, the central axis of the signal via hole is deviated from the central point of the signal pad, the direction of the central axis of the signal via hole deviated from the signal pad is opposite to the fan-out direction of the fan-out wiring on the signal via hole, and the space between the signal via hole and the side ground via hole is increased, so that the wiring space of the fan-out wiring is increased, the situation that the fan-out wiring can avoid the ground via hole in a dense array pad area even if the original line width is maintained, the line width of the fan-out wiring is equal everywhere, and the line width mutation of a narrow line segment and a wide line segment does not exist, thereby effectively improving the crosstalk of a high-frequency signal on the fan-out wiring.
Drawings
FIG. 1 is a schematic diagram of the structure of the present utility model;
FIG. 2 is a schematic diagram of a prior art structure;
FIG. 3 is a graph comparing crosstalk of the present utility model with that of the prior art;
fig. 4 is a graph comparing return loss of the present utility model with that of the prior art.
In the drawing of the figure,
1. The circuit comprises a signal via hole, a signal bonding pad, a 2-ground via hole, a 20-ground bonding pad, a 201-first-ground via hole, a 202-second-ground via hole, a 3-fan-out wiring and a 4-anti-bonding pad hollow area.
Detailed Description
For a better understanding of the objects, technical solutions and technical effects of the present utility model, the present utility model will be further explained below with reference to the drawings and examples. It should be noted that like reference numerals and letters refer to like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures. Meanwhile, it is stated that the embodiments described below are only for explaining the present utility model and are not intended to limit the present utility model.
It will be understood that when an element is referred to as being "mounted" or "disposed" on another element, it can be directly on the other element or intervening elements may also be present, and when an element is referred to as being "connected" to the other element, it may be directly connected to the other element or intervening elements may also be present.
The direction or position relationship is based on the direction or position relationship shown in the drawings, or the direction or position relationship which is commonly put when the application product is used, or the direction or position relationship which is commonly understood by those skilled in the art, or the direction or position relationship which is commonly put when the application product is used, only for the convenience of describing the application and simplifying the description, but does not indicate or imply that the device or element in question must have a specific direction, be configured and operated in a specific direction, and therefore should not be construed as limiting the application.
The terms "first," "second," and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features. The meaning of "a number" is two or more, unless specifically defined otherwise.
As shown in fig. 1, in the conventional fan-out wiring circuit board structure with holes in a disk, the central axis of the signal via 1 overlaps the central point of the signal pad 10, and the central axis of the ground via 2 overlaps the central point of the ground pad 20, and the projected view of the circuit board is shown as concentric circles from the top view of the circuit board. The fan-out wiring of the signal via hole 1 is a narrow line segment in the dense array pad area, and is restored to a wide line segment after being fanned out in the area, so that the line width of the fan-out wiring inside and outside the BGA chip area is changed, and the impedance mutation is caused at the line width mutation position.
As shown in fig. 2, in order to solve the problem of crosstalk in the high-frequency signal transmission of the fan-out wires in the tray with the above structure, the present utility model proposes a PCB structure based on reducing the crosstalk of the fan-out wires in the BGA, and similarly, the circuit board is a multi-layer circuit board, including a surface board, a plurality of inner boards and a bottom board, and the signal pads 10 and the ground pads 20 are located on the surface board for soldering pins of electronic components. The signal via hole 1 is connected to the bottom of the signal pad 10, the ground via hole 2 is connected to the bottom of the ground pad 20, the signal via hole 1 and the ground via hole 2 penetrate through a plurality of inner layers, the number of layers of the inner layers penetrated by the via hole is designed according to actual requirements, and the number of layers can be 2, 3 or all the inner layers penetrated by the via hole. The signal via hole 1 leads out the fanout wiring at the position of a layer plate in a certain layer, and specifically, the fanout wiring is led out from the layer plate in which the fanout wiring is designed according to actual requirements.
The key improvement point of the utility model is that the central axis of the signal via hole 1 is arranged away from the central point of the signal pad 10, namely, the signal via hole 1 and the signal pad 10 are not aligned any more, but deviate from the structure of the signal pad, the projection circle center of the signal pad 10 and the projection circle center of the signal via hole 1 are not overlapped when the projection diagram is observed from the overlook angle. And the direction in which the central axis of the signal via 1 deviates from the signal pad 10 is opposite to the fanout direction of the fanout trace on the signal via 1, for example, the fanout trace of the signal via 1 fanouts from the left side in the figure, the central axis of the signal via 1 deviates to the right side in the figure with respect to the signal pad 10. The space between the signal via hole 1 deviated to the right and the ground via hole 2 on the left becomes large, and the wiring space of the fan-out wiring is increased, so that the fan-out wiring can maintain the original line width even in the dense array pad area, and the line width is maintained at a fixed value. Therefore, the line widths of the fan-out wirings are equal everywhere, and no line width mutation of the narrow line segments and the wide limit segments exists.
For convenience of distinguishing, the signal pads and ground pads of the surface board are indicated by dotted lines, and the signal vias and ground vias of the inner board are indicated by solid lines, so the fan-out traces indicated by solid lines in the figure should pass under the pads indicated by dotted lines.
In this embodiment, there is a first distance between the center point of the signal pad 10 and the center axis of the signal via 1, the first distance being greater than zero and less than the radius of the signal pad 10, e.g., 0 to 5 mils. The central axis of the signal via 1 is always located in the projection area of the signal pad 10, and a larger intersection area is still reserved between the signal pad 10 and the cross section of the signal via 1, so that the electrical connection stability of the signal pad 10 and the signal via 1 is ensured.
In this embodiment, the circuit board is provided with an anti-pad hollowed-out area 4, and the signal via 1 is located in the anti-pad hollowed-out area 4. The anti-pad hollowed-out area 4 forms a shielding insulation area around the signal via hole 1, the electric signal on the signal via hole 1 is stably transmitted, and the fan-out wiring and the signal pad 10 obtain stable electric signals through the signal via hole 1. The antipad hollowed-out area 4 is oblong, two signal vias 1 of a pair of differential lines are arranged along the length direction of the antipad hollowed-out area 4, and in the width direction of the antipad hollowed-out area 4, the distance from one side of the signal via 1 to the antipad hollowed-out area 4 is equal to the distance from the opposite side of the signal via 1 to the antipad hollowed-out area 4, for example, the distance from the left side of the signal via 1 to the antipad hollowed-out area 4 is equal to the distance from the right side of the signal via 1 to the antipad hollowed-out area 4, so that the signal via 1 is positioned at the middle position of the antipad hollowed-out area 4 in the width direction.
In this embodiment, the traces are a pair of differential lines, and the line width of a single trace of the differential line is 4.5mil or 4mil or 5mil.
Example two
In the PCB structure based on the reduction of crosstalk of BGA fan-out routing vias, as in the first embodiment, the central axis of the signal via 1 is offset from the central point of the signal pad 10, and on this basis, the central axis of the ground via 2 is offset from the central point of the ground pad 20, and the central axis of the ground via 2 adjacent to the fan-out routing is offset in a direction away from the fan-out routing. For example, the fan-out wire of the signal via 1 is fan-out from the left side in the figure, and the first ground via 201 on the left side of the fan-out wire is deviated to the left side relative to the corresponding ground pad 20, so that the distance between the first ground via 201 on the left side of the fan-out wire and the signal via 1 on the right side of the fan-out wire is further increased, thereby further increasing the wiring space of the fan-out wire, and ensuring that the fan-out wire still has a sufficient insulation space with the side vias under the condition of maintaining the line width unchanged.
In this embodiment, there is a second distance between the center point of the ground pad 20 and the center axis of the ground via 2, the second distance being greater than zero and less than the radius of the ground pad 20, for example, the second distance ranging from 0 to 4 mils. The central axis of the ground via hole 2 is always located in the projection area of the signal pad 10, and a larger intersection area is still reserved between the ground pad 20 and the cross section of the ground via hole 2, so that the electrical connection stability of the ground pad 20 and the ground via hole 2 is ensured.
Example III
A PCB structure based on BGA fan-out wiring via crosstalk reduction is similar to the second embodiment, the central axis of the signal via 1 is deviated from the central point of the signal pad 10, the central axis of the ground via 2 is deviated from the central point of the ground pad 20, and on the basis, the circuit board anti-pad hollow area 4 is far away from the ground via 2 on the fan-out wiring side, and the central axis thereof is deviated towards the direction close to the anti-pad hollow area 4. For example, the fan-out trace of the signal via 1 is fanned out toward the left in the figure, that is, fanned out from the left side of the antipad hollowed out area 4, and then the second ground vias 202 on the right side of the antipad hollowed out area 4 are offset toward the left to approach the antipad hollowed out area 4, so that the second ground vias 202 and the signal via 1 are closer together, and the plurality of second ground vias 202 have better wrappability for the signal via 1.
As shown in fig. 3, the conventional circuit board structure and the circuit board structure of the present utility model are compared in crosstalk, in which curve a is the present utility model and curve B is the prior art, and it is known from the figure that the PCB structure of the present utility model significantly improves the crosstalk of the high frequency signal.
As shown in fig. 4, the comparison of return loss of the conventional circuit board structure and the circuit board structure of the present utility model is shown in fig. C, and curve D is shown in the prior art, and it is known from the figure that the return loss of the high-frequency signal is significantly improved by the PCB structure of the present utility model.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The foregoing examples illustrate only a few embodiments of the utility model, which are described in detail and are not to be construed as limiting the scope of the utility model. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the utility model, which are all within the scope of the utility model. Accordingly, the scope of protection of the present utility model is to be determined by the appended claims.
Claims (10)
1. The PCB structure based on BGA fan-out wiring via crosstalk reduction comprises a multilayer circuit board with a surface plate, an inner plate and a bottom plate, wherein the surface plate is provided with a signal pad and a ground pad, the bottom of the signal pad is connected with the signal via, the bottom of the ground pad is connected with the ground via, and the signal via is connected with a fan-out wiring on one of the inner plates.
2. The BGA fan-out via crosstalk reduction based PCB structure of claim 1, wherein a first distance is between a center point of the signal pad and a center axis of the signal via, the first distance being greater than zero and less than a radius of the signal pad.
3. The BGA fan-out via crosstalk reduction based PCB structure of claim 2, wherein the first distance ranges from 0 to 5 mils.
4. The PCB structure of claim 1, wherein the circuit board is provided with anti-pad hollowed-out areas, and the signal vias are located in the anti-pad hollowed-out areas.
5. The PCB structure of claim 4, wherein a distance from one side of the signal via to the antipad void is equal to a distance from an opposite side of the signal via to the antipad void in a width direction of the antipad void.
6. The PCB structure of claim 1, wherein the traces are a pair of differential traces and the individual traces of the differential traces have a linewidth of 4.5 mils.
7. The PCB structure of claim 1, wherein a center axis of the ground via is offset from a center point of the ground pad and a center axis of the ground via adjacent to the fan-out trace is offset in a direction away from the fan-out trace.
8. The PCB structure of claim 7, wherein a circuit board anti-pad undercut area is offset from the ground via on a side of the fanout trace with its center line offset in a direction toward the anti-pad undercut area.
9. The BGA fan out via crosstalk reduction based PCB structure of claim 7 or 8, wherein there is a second distance between the center point of the ground pad and the center axis of the ground via, the second distance being greater than zero and less than the radius of the ground pad.
10. The BGA fan-out via crosstalk-based PCB structure of claim 9, wherein the second distance ranges from 0 to 4 mils.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202420807342.3U CN222464922U (en) | 2024-04-18 | 2024-04-18 | A PCB structure based on reducing BGA fan-out trace via crosstalk |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202420807342.3U CN222464922U (en) | 2024-04-18 | 2024-04-18 | A PCB structure based on reducing BGA fan-out trace via crosstalk |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN222464922U true CN222464922U (en) | 2025-02-11 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202420807342.3U Active CN222464922U (en) | 2024-04-18 | 2024-04-18 | A PCB structure based on reducing BGA fan-out trace via crosstalk |
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| Country | Link |
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| CN (1) | CN222464922U (en) |
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- 2024-04-18 CN CN202420807342.3U patent/CN222464922U/en active Active
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