Shielding film electrical property verification transmission device

Abstract

The invention discloses a shielding film electrical property verification transmission device, a plurality of through holes are formed in the left side and the right side of the shielding film electrical property verification transmission device in a penetrating mode, and the shielding film electrical property verification transmission device comprises a test layer, a base material and a first grounding layer which are connected in sequence; a to-be-tested shielding film is attached to the first grounding layer and the base material, so that the test layer, the base material, the first grounding layer, the to-be-tested shielding film, the first grounding layer, the base material and the test layer form a loop; the test layer is provided with a test interface. During verification, a to-be-tested shielding film is attached to the first grounding layer and the base material, the to-be-tested shielding film is adopted to replace the reference layer, meanwhile, it is guaranteed that the impedance of the transmission line is uniform, an upper-layer medium (including a covering film) is omitted, and only the base material is adopted; the functions of other structures in the whole verification process are weakened (the influence of reflection, a covering film, a signal line, a reference layer and a base material on signals is weakened).

Description

Background Art

[0001] Shielding film (EMI) is a replacement material for copper foil, especially in the field of flexible printed circuits (FPC). It is thinner and has better bending performance while reducing signal interference, and its application scenarios are very wide. However, as modern electronic products develop towards high frequency and high speed, the shielding film not only plays a shielding role, but also acts as a reference layer, which cannot be ignored, and plays the role of signal return; however, in order to be thin and soft, the shielding film usually uses conductive glue or extremely thin conductors (usually less than 0.3μm). At this time, the shielding film is a poor conductor of the signal return path, causing a significant increase in conductor loss in the signal transmission process of the circuit board, which has a great impact on high-frequency transmission performance and is even the main cause of eye closure.

[0002] like Figure 1a and Figure 1b As shown in the figure, due to the complex structure of the conductive particles of the shielding film, there is little research on the effect of the shielding film on the loss. At present, manufacturers mainly verify the transmission performance of the shielding film in the following ways: 1. Test the far-field shielding effectiveness. This method actually only verifies the shielding effect of the shielding film and has no direct connection with the transmission performance of the shielding film. The shielding effectiveness is directly affected by the conductive particle coverage rate of the shielding film in the z-axis direction and the thickness of the conductive layer;

[0003] And from Figure 2 It can be seen that the signal transmission performance is affected by the continuity of the conductor in the xy direction and the roughness of the conductive layer close to the signal line, but the effect of shielding effectiveness on signal transmission is indirect, and only in some cases there is a causal relationship; 2. The insertion loss value is tested by impedance line. The impedance line type 1 commonly used by manufacturers is interfered by too many variables, such as covering film, substrate medium, copper thickness, metal roughness changes, etc., which jointly affect the transmission performance of the impedance line, and part of the electric field energy is between the signal line and the ground copper, which weakens the influence of the shielding film and interferes with both qualitative and quantitative analysis; such as Figure 3 and Figure 4 As shown, impedance line type 2 reduces the interference of reference layer metal compared to type 1, but the shielding film needs to be opened at the port position. As shown in the figure, this type of impedance line only has the shielding film acting as a reference layer, and there is no shielding film at the test window position, and there is no reference layer. The capacitance at this position is reduced, and there is an obvious increase in impedance, and the impedance continuity is poor, making it difficult to accurately measure high-frequency performance; in addition, the impedance of this type of impedance line is also greatly affected by the copper thickness, which is not conducive to controlling variables. The square resistance test in the xy direction requires separately designed samples, resulting in a waste of resources. Summary of the invention

[0004] In order to overcome the above-mentioned technical defects, the present invention provides a shielding film electrical property verification transmission device, which can weaken the effects of other structures of the shielding film electrical property verification transmission device.

[0005] In order to solve the above problems, the present invention is implemented according to the following technical solutions:

[0006] A shielding film electrical performance verification transmission device, wherein a plurality of through holes are provided on the left and right sides of the shielding film electrical performance verification transmission device, and the shielding film electrical performance verification transmission device comprises: a test layer, a substrate, and a first grounding layer connected in sequence;

[0007] The shielding film to be tested is attached to the first grounding layer and the substrate, so that the test layer, the substrate, the first grounding layer, the shielding film to be tested, the first grounding layer, the substrate, and the test layer form a loop;

[0008] The test layer is provided with a test interface.

[0009] As a further improvement of the present invention, the test layer includes: a signal line, two second ground layers;

[0010] The two grounding layers are disposed on different sides of the substrate, and two ends of the signal line are disposed close to the two second grounding layers respectively.

[0011] As a further improvement of the present invention, the test interface comprises: a loss GSG probe test port;

[0012] A first slot and a second slot are connected to each other on one side of the second ground layer close to the signal line;

[0013] The signal line extends from the first slot into the second slot;

[0014] The outer periphery of the second slot is plated with a copper layer, and the portion of the signal line extending into the second slot is plated with a copper layer;

[0015] The second ground layer and the portion of the signal line located at the second slot constitute the lossy GSG probe test port.

[0016] As a further improvement of the present invention, the copper layer contains an ultra-soft high-frequency substrate.

[0017] As a further improvement of the present invention, the first ground layer is provided with a third slot at a position corresponding to the first slot and the second slot, and the width of the first slot and the third slot is greater than three times the width of the signal line.

[0018] As a further improvement of the present invention, the test interface comprises: at least two internal resistance test ports;

[0019] The internal resistance test ports are arranged sequentially on the second ground layer from outside to inside.

[0020] As a further improvement of the present invention, the dielectric loss factor of the substrate is less than or equal to 0.003, and the thickness is greater than or equal to 50 microns.

[0021] As a further improvement of the present invention, the first grounding layer and the second grounding layer are both copper foils.

[0022] As a further improvement of the present invention, the roughness of the copper foil is less than or equal to 1 micron.

[0023] As a further improvement of the present invention, the shielding film to be tested is tightly bonded to the first grounding layer and the substrate by vacuum pressing.

[0024] Compared with the prior art, the present invention has the following beneficial effects: by setting through holes, a loop is formed among the test layer, the substrate, the first grounding layer and the shielding film to be tested. When testing, the test signal return path can pass through the shielding film to be tested normally. When verifying, the shielding film to be tested is attached to the first grounding layer and the substrate. The shielding film to be tested is used instead of the reference layer to ensure uniform transmission line impedance, eliminate the upper medium (including the covering film), and only use the substrate, thereby weakening the effect of other structures in the entire verification process (weakening the influence of reflection, covering film, signal line, reference layer and substrate on the signal). BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings, wherein:

[0026] Figure 1a , Figure 1b A schematic diagram of a test structure used in the prior art for testing far-field shielding effectiveness;

[0027] Figure 2 It is a structural schematic diagram of impedance line type 1 in the prior art;

[0028] Figure 3 It is a structural schematic diagram of impedance line type 2 in the prior art;

[0029] Figure 4 It is another structural schematic diagram of the impedance line type 2 in the prior art;

[0030] Figure 5 This is a schematic diagram of the overall structure of the shielding film electrical performance verification transmission device of the present invention;

[0031] Figure 6 An exploded view of the transmission device for verifying the electrical properties of the shielding film of the present invention;

[0032] Figure 7 It is a structural schematic diagram of the test layer of the present invention;

[0033] Figure 8It is a partial schematic diagram of the test interface of the present invention;

[0034] Fig. 9 is a schematic structural diagram of the first grounding layer of the present invention;

[0035] Fig.10 It is a schematic diagram of the structure of the shielding film to be tested after being attached to the shielding film electrical performance verification transmission device of the present invention.

[0036] Explanation of the accompanying drawings: 1. Test layer; 11. Signal line; 12. Second ground layer; 121. First slot; 122. Second slot; 2. Substrate; 3. First ground layer; 31. Third slot; 4. Through hole; 5; Test interface; 51. Loss GSG probe test port; 52. Internal resistance test port; 6. Copper layer; 100. Shielding film to be tested; 1001. Concave portion; 1002. Protrusion. DETAILED DESCRIPTION

[0037] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0038] The present invention provides a shielding film electrical performance verification transmission device, such as Figure 5 and Figure 6 As shown, a plurality of through holes 4 are provided on the left and right sides of the shielding film electrical performance verification and transmission device, and the shielding film electrical performance verification and transmission device includes: a test layer 1, a substrate 2, and a first grounding layer 3 connected in sequence; the shielding film 100 to be tested is adhered to the first grounding layer 3 and the substrate 2, so that the test layer 1, the substrate 2, the first grounding layer 3, the shielding film to be tested, the first grounding layer 3, the substrate 2, and the test layer 1 form a loop; the test layer 1 is provided with a test interface 5.

[0039] like Figure 7 As shown, the test layer 1 includes: a signal line 11 and two second grounding layers 12 ; the two grounding layers are disposed on different sides of the substrate 2 , and both ends of the signal line 11 are disposed close to the two second grounding layers 12 .

[0040] like Figure 8 As shown, the test interface 5 includes: a loss GSG probe test port 51, which also confirms the conductor loss introduced by the shielding film; the second ground layer 12 is close to the side of the signal line 11, and is provided with a first slot 121 and a second slot 122 that are connected; the signal line 11 extends from the first slot 121 to the second slot 122; the outer periphery of the second slot 122 is plated with a copper layer 6, and the portion of the signal line 11 extending into the second slot 122 is plated with a copper layer 6; the second ground layer 12 and the portion of the signal line 11 located at the second slot 122 constitute a loss GSG probe test port 51.

[0041] The copper layer 6 comprises an ultra-soft high-frequency substrate, such as porous PI, and copper plating is performed at the lossy GSG probe test port 51 to disperse stress and prevent parasitic capacitance mutation caused by collapse during the port test process.

[0042] like Fig. 9 As shown, the first grounding layer 3 is provided with a third slot 31 at the corresponding position of the first slot 121 and the second slot 122. The width of the first slot 121 and the third slot 31 is greater than three times the width of the signal line. Based on this, the signal loop in the test process can only pass through the shielding film to be tested but not through the original copper foil of the substrate 2. Among them, the first slot 121, the second slot 122, and the third slot 31 can be obtained by etching.

[0043] like Figure 8 As shown, the test interface 5 includes: at least two internal resistance test ports 52; the internal resistance test ports 52 are arranged on the second grounding layer 12 from the outside to the inside, and are used to obtain the conductivity or square resistance of the shielding film in the pure horizontal direction.

[0044] The dielectric loss factor of the substrate 2 is less than or equal to 0.003, and the thickness is greater than or equal to 50 microns. The first grounding layer 3 and the second grounding layer 12 are both copper foils; the roughness Rz of the copper foil is less than or equal to 1 micron, so that the conductor loss of the copper foil plus the dielectric loss is less than or equal to 3db / dm, that is, the impact on power reduction is less than one-half.

[0045] like Fig.10 As shown, the shielding membrane 100 to be tested is tightly fitted to the first grounding layer 3 and the substrate 2 through vacuum pressing, and the concave portion 1001 and the convex portion of the shielding membrane 100 to be tested are formed by the first grounding layer 3 and the substrate 2. Through vacuum pressing, the portion of the shielding membrane 100 to be tested that is fitted with the first grounding layer 3 forms a convex portion 1002, and the shape of the convex portion 1002 is the same as that of the first grounding layer 3. The portion of the shielding membrane 100 to be tested that is fitted with the substrate 2 forms a concave portion 1001, so that the shielding membrane 100 to be tested has a groove with the same shape as the third groove 31.

[0046] Next, the present invention is further explained in conjunction with the specific use process, as follows:

[0047] 1. Sheet resistance test:

[0048] The block resistance test is mainly implemented through the internal resistance test port (i.e., using a milliohm meter to connect the internal resistance test port, or using the four-wire method for testing). Taking two internal resistance test ports as an example, the test process is described as follows:

[0049] Define the internal resistance test port close to the second grounding layer as the far-end internal resistance test port, and the internal resistance test port close to the signal line as the near-end internal resistance test port. The distance difference between the far-end internal resistance test port and the near-end internal resistance test port is ΔL. The width of the shielding film to be tested is W. When the test layer, substrate, first grounding layer, shielding film to be tested, first grounding layer, substrate, and test layer form a loop, the resistance values ​​of the far-end internal resistance test port and the near-end internal resistance test port can be obtained as R1 and R2, respectively. At this time, the block resistance R sq The calculation formula is:

[0050]

[0051] When the precise thickness of the conductive layer is measured, the conductivity of the shielding film material can be further calculated.

[0052] 2. VNA test:

[0053] For the loss GSG probe port dual-channel test, use the S parameter mode to view the S11, S22, and S21 results in log format; S11 / S22 must be less than -10dB in the range of 0 to 40GHz (if S11 / S22 does not reach -10dB, it means that the impedance line design is unreasonable and needs to be further optimized according to the design results); save the S2P format file, select 2x thru (path) mode for de-embedding in AFR mode, set the long line s2p file to Fixtured DUT, and the short line s2p file to thru to obtain the de-embedded S parameter file; at this time, calculate the loss of its corresponding length, and you can get the S21 curve that uniformly decreases with increasing frequency per unit length, which can be used for high-resolution qualitative comparison (the performance of the two shielding films is very close and the difference can be distinguished) or quantitative calculation and analysis. In addition, based on the block resistance / copper foil roughness test, the conductor attenuation is calculated. (where α c : Attenuation of an ideal smooth conductor, α c ': attenuation after correction for surface roughness, △: root mean square value of surface roughness) and dielectric loss (where f is the sine wave frequency, tan(δ) is the loss angle factor, ε r is the real part of the dielectric constant), the additional attenuation α caused by different shielding films can be calculated EMI ≈|S21|-α diel -α c ', and then conduct quantitative control, the shielding film causes attenuation α EMI The smaller it is, the better the high-frequency transmission performance.

[0054] In summary, compared with the ordinary enhanced electric field strength between the electromagnetic film and the signal line, the present invention highlights the influence of the shielding film on the signal loss, eliminates the interference of the covering, substrate copper foil reference layer, etc. on the EMI electrical performance characterization of the shielding film, and the performance is not sensitive to the influence of the processed copper thickness. It can simplify the loss analysis caused by the shielding film, and combine the square resistance and scattering (S) parameter test data to separate the conductor loss caused by the shielding film when the substrate dielectric constant Dk / dielectric loss Df is known.

[0055] The shielding film electrical performance verification transmission device of the present invention makes the near-field performance of the shielding film better reflect its influence on the signal; the role of the shielding film to be verified in the shielding film electrical performance verification transmission device is: weakening the effect of other structures (weakening the influence of reflection, covering film, signal line, reference layer, substrate on the signal), the structural structure of the shielding film to be verified includes grooving, replacing the reference layer with the shielding film to be verified while ensuring the uniform impedance of the transmission line, eliminating the upper layer medium (including the covering film), and using only a low dielectric constant substrate, etc.

[0056] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A shielding film electrical performance verification transmission device, characterized in that: The shielding film electrical performance verification transmission device is provided with a plurality of through holes on both sides thereof, and the shielding film electrical performance verification transmission device comprises: a test layer, a substrate, and a first grounding layer connected in sequence; The shielding film to be tested is attached to the first grounding layer and the substrate, so that the test layer, the substrate, the first grounding layer, the shielding film to be tested, the first grounding layer, the substrate, and the test layer form a loop; The test layer is provided with a test interface.

2. The shielding film electrical performance verification transmission device according to claim 1, characterized in that: The test layer includes: a signal line and two second ground layers; The two grounding layers are disposed on different sides of the substrate, and two ends of the signal line are disposed close to the two second grounding layers respectively.

3. The shielding film electrical performance verification transmission device according to claim 2 is characterized in that: The test interface includes: a loss GSG probe test port; A first slot and a second slot are connected to each other on one side of the second ground layer close to the signal line; The signal line extends from the first slot into the second slot; The outer periphery of the second slot is plated with a copper layer, and the portion of the signal line extending into the second slot is plated with a copper layer; The second ground layer and the portion of the signal line located at the second slot constitute the lossy GSG probe test port.

4. The shielding film electrical performance verification transmission device according to claim 3 is characterized in that: The copper layer contains an ultra-soft high-frequency substrate.

5. The shielding film electrical performance verification transmission device according to claim 3 is characterized in that: The first ground layer is provided with a third slot at a position corresponding to the first slot and the second slot, and the width of the first slot and the third slot is greater than three times the width of the signal line.

6. The shielding film electrical performance verification transmission device according to claim 1, characterized in that: The test interface includes: at least two internal resistance test ports; The internal resistance test ports are arranged sequentially on the second ground layer from outside to inside.

7. The shielding film electrical performance verification transmission device according to claim 1, characterized in that: The dielectric loss factor of the substrate is less than or equal to 0.003, and the thickness is greater than or equal to 50 microns.

8. The shielding film electrical performance verification transmission device according to claim 2, characterized in that: The first ground layer and the second ground layer are both copper foils.

9. The shielding film electrical performance verification transmission device according to claim 8, characterized in that: The roughness of the copper foil is less than or equal to 1 micron.

10. The shielding film electrical performance verification transmission device according to claim 1, characterized in that: The shielding film to be tested is tightly adhered to the first grounding layer and the substrate through vacuum pressing.

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