Wear test strip and PCB device

Abstract

The embodiment of the present application relates to the technical field of PCB, and discloses a loss test strip and a PCB device, wherein the loss test strip comprises at least one signal layer, at least two pairs of differential transmission lines with different lengths are arranged on the at least one signal layer, and the outer surface of the loss test strip is provided with test areas corresponding to two ends of each pair of differential transmission lines, respectively, the two ends of each pair of differential transmission lines extend to the projection area of the corresponding test area towards the signal layer where the end is located, and the distance between the two test areas corresponding to one pair of differential transmission lines in the two pairs of differential transmission lines is equal to the distance between the two test areas corresponding to another pair of differential transmission lines. The loss test strip provided by the embodiment of the present application can simplify the loss test process of the loss test strip, and is conducive to realizing the automatic test of the loss of the PCB device.

Description

Technical Field

[0001] This invention relates to the field of PCB (Printed Circuit Board) technology, and particularly to a loss test strip and PCB device. Background Technology

[0002] With the continuous development of communication technology, the speed of SERDES (serializer / deserializer) transceivers on high-speed product boards such as core networks and bearer networks has reached 56Gbps (gigabits per second), and is currently moving towards 112Gbps. Meanwhile, standards organizations have also initiated work on the 224Gbps project. As SERDES speeds continue to increase, the loss margin of high-speed passive channels becomes very small. Fluctuations in transmission line loss caused by PCB manufacturing processes directly affect the operational stability of high-speed products. Therefore, for high-speed products, loss testing must be performed on the PCB after manufacturing to prevent PCBs with excessive loss from entering the product and causing potential quality issues.

[0003] However, due to the high density of high-speed PCB products, it is difficult to add dedicated loss test points. Directly using BGA (Ball Grid Array) pads or connector vias on the PCB for testing presents the following problems: 1. Direct testing using BGA pads or connector vias requires a probe method, which has low bandwidth and insufficient testing accuracy; 2. Directly testing BGA pads or connector vias with a probe will scratch them, affecting the reliability of subsequent chip soldering or connector crimping. Therefore, the current common practice is to design dedicated loss test strips and attach them to the board edge during PCB fabrication. This allows for the acquisition of loss information within the high-speed PCB through testing the loss test strips without affecting the PCB's quality.

[0004] However, since the number of PCB products processed in each batch is very large, the workload of manual testing would be quite heavy. Therefore, simplifying the testing process of the loss test strip is an urgent problem to be solved. Summary of the Invention

[0005] The main objective of this invention is to provide a loss test strip and a PCB device that can simplify the loss test process of the loss test strip and facilitate the automated testing of the loss of the PCB device.

[0006] To achieve the above objectives, embodiments of the present invention provide a loss test strip, comprising at least one signal layer, on which at least two pairs of differential transmission lines of different lengths are disposed. The outer surface of the loss test strip is provided with test areas corresponding one-to-one with the two ends of the extension path of each pair of differential transmission lines. The two ends of the extension path of each pair of differential transmission lines extend to the projection area of ​​the corresponding test area toward the signal layer where the end is located. In two different pairs of differential transmission lines, the distance between the two test areas corresponding to one pair of differential transmission lines is equal to the distance between the two test areas corresponding to the other pair of differential transmission lines.

[0007] To achieve the above objectives, embodiments of the present invention provide a PCB device, comprising:

[0008] The aforementioned loss test strip.

[0009] This invention discloses a loss test strip and PCB device. Two test areas, each corresponding to one end of the extension path of a pair of differential transmission lines, are equidistantly positioned. Specifically, in two different pairs of differential transmission lines, the distance between the two test areas corresponding to one pair is equal to the distance between the two test areas corresponding to the other pair. Thus, when testing the loss test strip, after testing the loss of one pair of differential transmission lines, the test ports of the test fixture do not need to be adjusted to directly test the loss of the other pair. This simplifies the loss testing process of the loss test strip, significantly reduces the complexity of designing automated testing equipment, and facilitates automated testing of PCB device losses. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the signal layer structure of the loss test strip provided according to an embodiment of the present invention;

[0011] Figure 2 yes Figure 1 Enlarged structural diagram at point A;

[0012] Figure 3 This is a front structural schematic diagram of the loss test strip provided according to an embodiment of the present invention;

[0013] Figure 4 It is along Figure 3 Schematic diagram of the cross-sectional structure along the BB direction;

[0014] Figure 5 yes Figure 3 An enlarged structural diagram of the area shown at point C in the middle;

[0015] Figure 6This is a schematic diagram of the back structure of the loss test strip provided according to an embodiment of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details are presented in the embodiments of the present invention to facilitate a better understanding of the invention. However, the technical solutions claimed in the present invention can be implemented even without these technical details and various variations and modifications based on the following embodiments. The division of the following embodiments is for ease of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined with and referenced by each other without contradiction.

[0017] Figure 1 The signal layer structure of the loss test strip provided in an embodiment of the present invention is shown. Figure 2 for Figure 1 Enlarged structural diagram at point A in the middle. Figure 3 The front structure of the loss test strip provided in an embodiment of the present invention is shown. Figure 4 For along Figure 3 Sectional structure along the BB direction, Figure 5 for Figure 3 An enlarged structural diagram of the area shown at point C. Figure 6 The back structure of the loss test strip provided in an embodiment of the present invention is shown. For example... Figures 1 to 6 As shown, the loss test strip includes at least one signal layer 10, on which at least two pairs of differential transmission lines 100 with different lengths are disposed. The outer surface S of the loss test strip is provided with test areas 200 corresponding one-to-one with the two ends 101 on the extension path of each pair of differential transmission lines 100. The two ends 101 on the extension path of each pair of differential transmission lines 100 extend to the projection area of ​​the corresponding test area 200 toward the signal layer 10 where the end 101 is located. Among the two different pairs of differential transmission lines 100, the distance between the two test areas 200 corresponding to one pair of differential transmission lines 100 is equal to the distance between the two test areas 200 corresponding to the other pair of differential transmission lines 100.

[0018] The loss test strip provided in this embodiment of the invention sets two test areas 200, each corresponding to one of the two ends 101 on the extension path of each pair of differential transmission lines 100, at equal intervals. That is, in two different pairs of differential transmission lines 100, the distance between the two test areas 200 corresponding to one pair is equal to the distance between the two test areas 200 corresponding to the other pair. Thus, when testing the loss test strip, after testing the loss of one pair of differential transmission lines 100, the test ports of the test fixture do not need to adjust the distance between the ports to directly test the loss of the other pair of differential transmission lines 100. This simplifies the loss testing process of the loss test strip, significantly reduces the complexity of designing automated testing equipment, and facilitates automated testing of PCB device losses.

[0019] It should be noted that existing loss test strips, due to different winding methods, will have some differences in the relative positions of the two test areas 200 corresponding to each pair of differential transmission lines 100. As a result, when testing the loss test strip with the testing equipment, the inconsistent relative distance between the two test areas 200 corresponding to each pair of differential transmission lines means that after testing the loss of one pair of differential transmission lines 100, the distance between the test ports of the test fixture needs to be adjusted before testing the loss of the other pair of differential transmission lines 100. This will significantly increase the design complexity and cost of the automated test fixture, and is not conducive to the automated testing of loss test strips.

[0020] Furthermore, at least two pairs of differential transmission lines 100 with different lengths are provided on at least one signal layer 10 because, in the test of the loss test strip, it is necessary to calculate the insertion loss on the PCB product (insertion loss refers to the loss of load power at a certain point in the transmission system due to the insertion of components or devices) based on the measurement difference between each pair of differential transmission lines 100. The difference in loss results obtained from the test of the two pairs of differential transmission lines 100 can be used to calculate the insertion loss per unit length of the PCB trace. This test method can avoid the influence of test probes and vias on the PCB, thus ensuring the reliability of the loss test results.

[0021] The differential transmission line 100 serves as the test object, and the arrangement of its corresponding test areas 200 directly affects the size of the loss test strip. To reduce the size of the loss test strip and improve the utilization rate of the board material used to manufacture it, in one possible implementation, multiple test areas 200 can be arranged along a first direction X on the outer surface S of the loss test strip, with the two test areas 200 corresponding to the same pair of differential transmission lines 100 positioned close to each other. The first direction X is parallel to the length direction of the loss test strip. This arrangement of multiple test areas 200 on the outer surface S along the length of the loss test strip avoids unnecessary space occupation due to a disorganized distribution of the test areas 200, thus improving the utilization rate of the board material used to manufacture the loss test strip. Simultaneously, the close proximity of the two test areas 200 corresponding to each pair of differential transmission lines 100 reduces the clutter when arranging multiple pairs of differential transmission lines 100, ensuring a close correspondence between the positions of each pair of differential transmission lines 100 and its corresponding two test areas 200.

[0022] When there are two pairs of differential transmission lines 100 on the signal layer 10, the longer pair of differential transmission lines 100 can be positioned in the middle of the signal layer 10. The two test areas 200 corresponding to one pair of differential transmission lines 100 are positioned along the first direction X on one side of the outer surface of the loss test strip, and the two test areas 200 corresponding to the other pair of differential transmission lines 100 are positioned on the other side of the outer surface of the loss test strip. This makes the layout of the multiple test areas 200 and the two pairs of differential transmission lines 100 on the signal layer 10 clearer, preventing obvious messy misalignment.

[0023] This place is Figure 2 Taking the loss test strip shown as an example, this loss test strip includes a signal layer 10, with planar layers 11 on both sides. The outer surface S of the loss test strip is the surface of the planar layer 11. Furthermore, the layout of the test area 200 and the differential transmission lines 100 is explained when there are two pairs of differential transmission lines 100 on the signal layer 10. Figure 1 As shown, a pair of relatively long differential transmission lines 100 on the signal layer 10 are bent at the middle of the signal layer 10, and the two ends 101 of the pair of relatively long differential transmission lines 100 extend to the corresponding test areas 200 projecting towards the signal layer 10. The outer surface S of the loss test strip has four test areas 200, with the two test areas 200 corresponding to the pair of relatively long differential transmission lines 100 located on the left side of the loss test strip (i.e.,...). Figure 1 As shown below, two test areas 200 corresponding to the shorter pair of differential transmission lines 100 are distributed on the right side of the loss test strip (i.e., at the lower position shown). Figure 1(As shown above). It can be seen that the layout of the two pairs of differential transmission lines 100 is relatively clear, and the layout of the two test areas 200 corresponds closely to the two ends 101 on the extension path of one pair of differential transmission lines 100, and the other two test areas 200 are the same.

[0024] It should be noted that this example illustrates the layout of each test area 200 on the loss test strip and the layout of each pair of differential transmission lines 100 on the signal layer 10. It is not a limitation on the number or layout of each test area 200 on the loss test strip or the number or layout of multiple pairs of differential transmission lines 100 on the signal layer 10. In other possible implementations, there may be other numbers or other forms of layout. For example, when there are three pairs of differential transmission lines 100 on the signal layer 10, the test areas 200 corresponding to different pairs of differential transmission lines 100 can be arranged at different positions on the outer surface S of the loss test strip in the same manner. For example, the two test areas 200 corresponding to the longest pair of differential transmission lines 100 can be arranged on the far left of the outer surface S of the loss test strip, the two test areas 200 corresponding to the second longest pair of differential transmission lines 100 can be arranged in the middle of the outer surface S of the loss test strip, and the two test areas 200 corresponding to the shortest pair of differential transmission lines 100 can be arranged on the far right of the outer surface S of the loss test strip. This still makes the layout of each test area 200 on the loss test strip and the layout of each pair of differential transmission lines 100 on the signal layer 10 relatively clear and avoids a messy layout. Alternatively, the test areas 200 on the loss test strip can be set on the same side of the loss test strip, and each pair of differential transmission lines 100 can be bent accordingly according to the projection area of ​​the corresponding test area 200 toward the signal layer 10 where the pair of differential transmission lines 100 is located.

[0025] Furthermore, when the loss test strip includes two or more signal layers 10, and when two or more signal layers 10 are provided with differential transmission lines 100, the test area 200 on the outer surface S of the loss test strip can still be arranged along the first direction X. In this way, it is only necessary to change the extension path of each pair of differential transmission lines 100 on different signal layers 10, so that each pair of differential transmission lines 100 on different signal layers 10 can extend to the corresponding test area 200. When setting up each pair of differential transmission lines 100 on different signal layers 10, the projections of each pair of differential transmission lines 100 on different layers can be staggered by a certain distance, thereby reducing mutual interference.

[0026] Meanwhile, each pair of differential transmission lines 100 here may include two transmission lines 110 with the same linewidth. The transmission lines 110 of two different pairs of differential transmission lines 100 have the same linewidth and spacing. That is, in two different pairs of differential transmission lines 100, the distance between the two transmission lines 110 of one pair is equal to the distance between the two transmission lines 110 of the other pair, and the linewidth of any transmission line 110 of one pair is equal to the linewidth of any transmission line 110 of the other pair. If a straight-line chamfered winding method with a certain angle is used during the bending setting of each pair of differential transmission lines 100, it will lead to impedance discontinuity and affect the loss test results. Therefore, in order to make the impedance change on each pair of differential transmission lines 100 more continuous, the bending position of each pair of differential transmission lines 100 can be set to an arc shape. Specifically, each transmission line 110 of each pair of differential transmission lines 100 may include a plurality of extension segments 111 extending along a first direction X, and an intermediate segment 112 connecting two adjacent extension segments 111, each intermediate segment 112 being arranged in an arc shape. In this way, compared to a straight-line winding form with a certain angled chamfer, the impedance changes on each pair of differential transmission lines 100 can be more connected.

[0027] In addition, when winding each pair of differential transmission lines 100, in order to avoid crosstalk caused by the small winding spacing of the transmission lines 110 of each pair of differential transmission lines 100, the distance between two adjacent extensions 111 of any transmission line 110 in each pair of differential transmission lines 100 can be greater than three times the line width of the transmission line 110. In this way, the impact of crosstalk between windings on loss testing can be reduced, and the accuracy of loss testing can be ensured.

[0028] When testing the loss on each pair of differential transmission lines 100, each pair of differential transmission lines 100 needs to be led to the outer surface S of the loss test strip so that the test probe of the test fixture can be connected to each pair of differential transmission lines 100, allowing each pair of differential transmission lines 100 to be connected to the test equipment during testing. Specifically, each pair of differential transmission lines 100 can be led to the outer surface S of the loss test strip through signal holes 210 provided in each test area 200. Two signal holes 210 can be provided in each test area 200, and the structure of the signal holes 210 can be referred to [reference needed]. Figure 5A ring of ground vias 211 is distributed around the signal aperture 210. Each transmission line 110 of each pair of differential transmission lines 100 is connected to a fan-out line 120 at one end. One of the signal apertures 210 in each test area 200 is connected to the fan-out line 120 at one end of one of the transmission lines 110 of the corresponding pair of differential transmission lines 100, and the other signal aperture 210 in each test area 200 is connected to the fan-out line 120 at one end of the other transmission line 110 of the corresponding pair of differential transmission lines 100. Thus, when testing the loss test strip using a four-port test device, the loss of one pair of differential transmission lines 100 is tested through the four test ports. The two test areas 200 corresponding to the pair of differential transmission lines 100 have four signal holes 210. Two ports used for output signals can be connected one-to-one to the two signal holes 210 in one test area 200, and the other two ports used for receiving signals can be connected one-to-one to the two signal holes 210 in the other test area 200, thereby testing the loss on one pair of differential transmission lines 100. Figure 1 As shown, at one end of each pair of differential transmission lines 100 connected to the signal aperture 210, it first fans out as a fan-out line 120 (i.e., a single-ended line), runs a short distance, and then merges into a pair of differential transmission lines 100. This avoids the situation where the sum of the impedances of the two transmission lines 110 is greater than the impedance of the differential transmission line 100 because the differential transmission line 100 has not been converted to a single-ended line, thus ensuring the impedance continuity of the entire transmission line 110 network.

[0029] Furthermore, the distance between two signal holes 210 within each test area 200 can be equal to half the distance between the centers of the two test areas 200 corresponding to the two ends 101 on the extension path of each pair of signal transmission lines 110. In this way, the distance between any two adjacent signal holes 210 in the four signal holes 210 within the two test areas 200 corresponding to the same pair of differential transmission lines 100 is the same, facilitating the arrangement of test ports on the test fixture. Here, the center of each test area 200 is the midpoint of the line connecting the two signal holes 210 within that test area 200.

[0030] Meanwhile, in order to increase the test bandwidth for loss testing, such as Figure 3 As shown, two signal holes 210 in each test area 200 on the front of the loss test strip can be connected to an SMA (Sub-Miniature version A) interface. Compared with using probe pads to test the loss of the differential transmission line 100, each signal hole 210 is encapsulated with an SMA interface 220, and subsequent testing can be performed using the SMA method, which greatly improves the test bandwidth.

[0031] In addition, at least one positioning hole 300 can be set on the loss test strip or at least one optical positioning point 400 can be set on the outer surface S of the loss test strip, which is beneficial to realize the automatic positioning of the test fixture.

[0032] This invention also provides a PCB device (not shown in the figure), which includes the loss test strips described in the above embodiments. The PCB device is formed by attaching the loss test strips to the edge of a PCB circuit board. This allows for loss testing of the PCB device without affecting its quality, enabling the acquisition of loss information within the high-speed PCB device through testing the loss test strips. Furthermore, the two test areas 200 on the loss test strip, corresponding to each pair of differential transmission lines 100, are equidistantly arranged, simplifying the loss testing process, significantly reducing the complexity of automated testing equipment design, and facilitating automated testing of losses within the PCB device.

[0033] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the present invention.

Claims

1. A loss test strip, characterized in that, The system includes at least one signal layer, on which at least two pairs of differential transmission lines of different lengths are disposed. The outer surface of the loss test strip is provided with test areas corresponding one-to-one with the two ends of the extension path of each pair of differential transmission lines. The two ends of the extension path of each pair of differential transmission lines extend to the projection area of ​​the corresponding test area toward the signal layer where the end is located. Among two different pairs of differential transmission lines, the distance between the two test areas corresponding to one pair of differential transmission lines is equal to the distance between the two test areas corresponding to the other pair of differential transmission lines.

2. The loss test strip according to claim 1, characterized in that: Multiple test areas are arranged along a first direction on the outer surface of the loss test strip, with two test areas corresponding to the same pair of differential transmission lines arranged close to each other, and the first direction being parallel to the length direction of the loss test strip.

3. The loss test strip according to claim 2, characterized in that: There are two pairs of differential transmission lines on the signal layer. The longer pair of differential transmission lines is located in the middle of the signal layer. The two test areas corresponding to one pair of differential transmission lines are located on one side of the outer surface of the loss test strip along the first direction. The two test areas corresponding to the other pair of differential transmission lines are located on the other side of the outer surface of the loss test strip along the first direction.

4. The loss test strip according to claim 2, characterized in that: Each pair of differential transmission lines includes two transmission lines with the same linewidth. In two different pairs of differential transmission lines, the distance between the two transmission lines in one pair is equal to the distance between the two transmission lines in the other pair, and the linewidth of any transmission line in one pair is equal to the linewidth of any transmission line in the other pair. Each transmission line in each pair of differential transmission lines includes a plurality of extension segments extending along the first direction, and an intermediate segment connecting two adjacent extension segments, each intermediate segment being arc-shaped.

5. The loss test strip according to claim 4, characterized in that: The distance between any two adjacent extensions of any of the differential transmission lines in each pair is greater than three times the linewidth of the transmission line.

6. The loss test strip according to claim 4, characterized in that: Each test area is provided with two signal holes. Each end of any transmission line in each pair of differential transmission lines is connected to a fan-out line. One of the signal holes in each test area is connected to the fan-out line at one end of one of the transmission lines in the corresponding pair of differential transmission lines, and the other signal hole in each test area is connected to the fan-out line at one end of the other transmission line in the corresponding pair of differential transmission lines.

7. The loss test strip according to claim 6, characterized in that: Each of the two signal holes in the test area is connected to an SMA interface.

8. The loss test strip according to any one of claims 1 to 7, characterized in that: The loss test strip is also provided with at least one positioning hole.

9. The loss test strip according to any one of claims 1 to 7, characterized in that: The outer surface of the loss test strip is also provided with at least one optical positioning point.

10. A PCB device, characterized in that, include: The loss test strip according to any one of claims 1 to 9.

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