CN1387396A - Impedance measuring structure - Google Patents

Abstract

An impedance measuring structure is suitable for a circuit substrate and is provided with a first measuring welding pad and a second measuring welding pad which are both arranged on the surface of the circuit substrate. The impedance measuring structure is also provided with a measuring trace which is arranged on the surface of the circuit substrate, and one end of the measuring trace is connected to the second measuring welding pad. The circuit substrate is provided with a patterned circuit layer which is positioned on the surface layer of the circuit substrate, and the impedance measuring structure is formed by the patterned circuit layer. In addition, the circuit substrate is provided with a grounding circuit, and the first measuring welding pad is electrically connected to the grounding circuit. In addition, the circuit substrate is divided into a reserved area and a cut-out area, and the impedance measuring structure is positioned in the cut-out area.

Description

Impedance measurement structure

technical field

The present invention relates to an impedance measurement structure, and in particular to an impedance measurement structure that can be fabricated on the surface of a circuit substrate.

Background technique

Since the signal of the integrated circuit (Integrated Circuit, IC) chip (Die) passes through the internal circuit of the chip packaging substrate (Substrate) and the printed circuit board (Printed Circuit Board, PCB) in sequence, and then is transmitted to the remote external electronic device, Therefore, these substrates and printed circuit boards responsible for transmitting signals have a decisive impact on the signal integrity (Signal Integrity). With the increasing operating frequency of the system, when the error of the line width, line height, line spacing or dielectric layer thickness of the internal circuit of the substrate or printed circuit board is too large, and the problem of impedance mismatch (Impedance Mismatch) occurs, it will lead to Severe voltage reflection (Reflection) phenomenon, thus causing errors in the interpretation of high-level or low-level signals, and in severe cases, it may even make the entire system device unable to operate normally. Therefore, in the manufacturing process of substrates and printed circuit boards used for chip packaging, how to accurately control the line width, line height (line thickness), line spacing and dielectric layer thickness of the internal circuits of the substrate and printed circuit boards, and It is very important to accurately control the electrical impedance value of its internal circuit.

As far as it is known, the substrate or printed circuit board used for chip packaging is designed for practical applications, and the line width, line height, line spacing and dielectric layer thickness of the internal circuit of the substrate or printed circuit board must be designed at the same time. Furthermore, the electrical impedance value of the internal circuit of the printed circuit board is controlled. It is worth noting that due to slight deviations in the process of the substrate or printed circuit board used for chip packaging, there may be relative errors in the line width, line height, line spacing or dielectric layer thickness of the internal lines, making the internal lines The electrical impedance value exceeds or falls below the tolerance range (tolerance) of the originally designed electrical impedance value.

As mentioned above, after the substrate or printed circuit board for chip packaging is completed, the electrical impedance value of its internal circuit is not tested, that is, the next stage of assembly work is carried out, and the electrical impedance value is only tested on the final actual product. value detection. Once the electrical impedance value of the substrate or the internal circuit of the printed circuit board does not meet the design requirements, it will inevitably reduce the production pass rate of the final actual product. Therefore, after the substrate or printed circuit board for chip packaging is completed, it is necessary to detect the electrical impedance value of its internal circuit in advance, so as to exclude the substrate or printed circuit board for chip packaging whose electrical impedance value does not meet the standard, so that it cannot be processed. The assembly operation in the next stage can improve the production qualification rate of the final actual product and reduce its manufacturing cost at the same time.

Contents of the invention

The object of the present invention is to provide a kind of impedance measurement structure, when making circuit substrate (such as substrate or printed circuit board for chip packaging), can utilize the patterned line layer of circuit substrate surface layer, and this impedance measurement structure can be made on The surface of the circuit substrate. After the circuit substrate is manufactured, the electrical impedance value of the measurement trace of the impedance measurement structure can be detected to determine the line width, line height, line spacing and dielectric layer of the patterned circuit layer of the circuit substrate. Thickness, whether it meets the requirements of the original design.

Based on the above purpose of the present invention, the present invention proposes an impedance measurement structure suitable for a circuit substrate. The impedance measurement structure has a first measurement pad and a second measurement pad, both of which are arranged on the surface of the circuit substrate. . Moreover, the impedance measurement structure further has a measurement trace disposed on the surface of the circuit substrate, and one end of the measurement trace is connected to the second measurement pad. Wherein, the surface of the circuit substrate has a patterned circuit layer, and the impedance measurement structure is formed by the patterned circuit layer. In addition, the circuit substrate has a ground circuit, and the first measurement pad is electrically connected to the ground circuit. In addition, the circuit substrate has a reserved area and a cut-off area, and the impedance measurement structure is arranged on the surface of the cut-out area.

Description of drawings

Fig. 1 is a kind of impedance measurement structure of the embodiment of the present invention, and it is applied to the schematic diagram of a circuit substrate;

2A and 2B are schematic diagrams of an impedance measurement structure of an embodiment of the present invention, which is applied to a single transmission line;

3A and 3B are schematic diagrams of another impedance measurement structure of the embodiment of the present invention, which is applied to a differential signal transmission line; and

FIG. 3C and FIG. 3D are schematic diagrams of yet another impedance measurement structure according to the embodiment of the present invention, which is applied to a differential signal transmission line.

Explanation of reference signs:

10: Circuit board 12: Excision area

12a: Board edge 12b: Cutting path

14: Reserved area 16: Grounding circuit

100: Impedance measurement structure 102: The first measurement pad

104: Second measurement pad 106: Measurement trace

200: Impedance measurement structure 202: The first measurement pad

204: Second measurement pad 206: First measurement trace

212: The third measurement pad 214: The fourth measurement pad

216: Second measurement trace 222: Fifth measurement pad

Detailed ways

Please refer to FIG. 1 , which is a schematic diagram of an impedance measurement structure applied to a circuit substrate according to an embodiment of the present invention. After the circuit substrate 10 is manufactured, the excess board edge 12 a of the circuit substrate 10 is usually cut off, and only the central part of the circuit substrate 10 is reserved. In addition, in order to reduce the manufacturing cost of small-sized circuit boards, the circuits of multiple small-sized circuit boards are usually designed in each reserved area 14 of the same large-sized circuit board 10 at the same time, and then these reserved areas 14 are removed from the circuit board. 10 were cut down separately. In order to facilitate the cutting operation, a cutting line 12 b is usually designed between two adjacent circuit areas 14 , and the board edge 12 a and the cutting line 12 b of the circuit substrate 10 together constitute the cutting area 12 of the circuit substrate 10 .

Please also refer to FIG. 1. The circuit substrate 10 is usually formed by interlacing and stacking multiple patterned circuit layers and multiple insulating layers. In order to determine the conductive traces of the patterned circuit layer of the circuit substrate 10, the line width and line height (line thickness), line spacing and dielectric layer thickness are all within the tolerance (tolerance) range, therefore, while making the circuit substrate 10, the present invention utilizes the patterned circuit layer on the surface layer of the circuit substrate 10 to form an impedance measurement structure 100. In addition, in order to increase the convenience of the impedance detection operation, the impedance measurement structure 100 is usually designed on the surface of the circuit substrate 10 . In addition, since the impedance measuring structure 100 loses its function after measuring its electrical impedance value, the impedance measuring structure 100 can be designed to be located in the cut-out area 12 of the circuit substrate 10, including the edge 12a or the cutting line 12b, and They are respectively adjacent to the respective reserved areas 14 , ie next to the uncut circuit structures.

Please refer to FIG. 1, FIG. 2A, and FIG. 2B at the same time, wherein FIG. 2A and FIG. 2B are schematic diagrams of an impedance measurement structure of an embodiment of the present invention, which is applied to a single transmission line (Single End). First, as shown in FIG. 2A, the impedance measurement structure 100 is mainly composed of a first measurement pad 102, a second measurement pad 104 and a measurement trace 106, wherein the first measurement pad 102 is arranged on the circuit substrate 10 and is electrically connected to the grounding circuit 16 of the circuit substrate 10 through winding wires, such as a sheet-like grounding structure (ground plane), and the second measurement pad 104 is also arranged on the surface of the circuit substrate 10 and is adjacent to it. On the first measurement pad 102 , the measurement trace 106 is disposed on the surface of the circuit substrate 10 , and one end of the measurement trace 106 is connected to the second measurement pad 104 . Therefore, after the circuit substrate 10 in FIG. 1 is manufactured, the probes of the impedance measuring instrument can be respectively contacted with the first measurement pad 102 and the second measurement pad 104, and the resistance of this section of the measurement trace 106 can be measured. resistance value. In addition, as shown in FIG. 2B , in addition to the first measurement pad 102 of the impedance measurement structure 100 being electrically connected to the ground circuit 16 through wire winding, the other end of the measurement trace 106 may also be electrically connected to the ground through wire winding. In such a connection mode, the circuit 16 can also use an impedance measuring instrument to measure the electrical impedance value of this section of the measurement trace 106 through the first measurement pad 102 and the second measurement pad 104 .

Please refer to FIG. 1 and FIG. 2A again. Since the magnitude of the electrical impedance value of the measurement trace 106 corresponds to the line length, line width and line height of the measurement trace 106, the measurement trace 106 can be pre-designed to have a specific line length. , line width and line height, and correspond to the line length, line width and line height of this section of the measurement trace 106, and set the tolerance range of its electrical impedance value, therefore, in the case of producing the circuit substrate 10 of Fig. 1 in large quantities , the impedance measurement structure 100 of the circuit substrate 10 can be sampled and detected. Once the electrical impedance value of the measurement trace 106 of the impedance measurement structure 100 is found to exceed the originally set electrical impedance value range, it means that there is a problem with the process of the circuit substrate 10, for example Process problems such as decreased alignment accuracy or changes in etch rate.

Due to the increasing integration of the components and circuits inside the chip, in order to prevent the signal from being interfered by the electromagnetic field during the transmission process, the signal interpretation error occurs, so the known technology produces a differential signal (Differential Pair) Dual transmission line design. Please refer to FIG. 3A and FIG. 3B , which are schematic diagrams of another impedance measurement structure applied to a differential signal transmission line according to an embodiment of the present invention. First, as shown in FIG. 3A, the impedance measurement structure 200 is designed for detecting the electrical impedance value of a pair of conductive traces of a differential signal. The impedance measurement structure 200 is mainly composed of a first measurement pad 202, a second measurement pad 204 and The first measurement trace 206 , the third measurement pad 212 , the fourth measurement pad 214 , and the second measurement trace 216 can all be composed of the patterned circuit layer on the surface layer of the circuit substrate 10 in FIG. 1 .

Please also refer to FIG. 3A, the first measurement pad 202, the second measurement pad 204 and the first measurement trace 206 are all arranged on the surface of the circuit substrate 10 in FIG. It is electrically connected to the ground circuit 16 , and the location of the second measurement pad 204 is adjacent to the location of the first measurement pad 202 , and one end of the first measurement trace 206 is connected to the second measurement pad 204 . In addition, the third measurement pad 212, the fourth measurement pad 214 and the second measurement trace 216 are all configured on the surface of the circuit substrate 10 in FIG. The positions of the two measurement traces 216 correspond to the positions of the first measurement pad 202, the second measurement pad 204, and the first measurement trace 206, respectively, and the third measurement pad 212 can be electrically connected to the ground circuit through winding. 16.

Please also refer to FIG. 3A , the lengths of the first measurement trace 206 and the second measurement trace 216 can be designed to be the same, so the first measurement can be measured through the first measurement pad 202 and the second measurement pad 204 using an impedance measuring instrument. The electrical impedance value of the trace 206 is measured, and the electrical impedance value of the second measurement trace 216 is measured through the third measurement pad 212 and the fourth measurement pad 214 at the same time. In addition, please refer to FIG. 3B , the other end of the first measurement trace 206 and the other end of the second measurement trace 216 can also be electrically connected to the ground circuit of the circuit board through winding wires respectively. An impedance measuring instrument can be used to measure the electrical impedance value of the first measurement trace 206 through the first measurement pad 202 and the second measurement pad 204 , and at the same time measure through the third measurement pad 212 and the fourth measurement pad 214 The electrical impedance value of the second measurement trace 216 . Similarly, the electrical impedance values of the first measurement trace and the second measurement trace measured through the above-mentioned impedance measurement structure cannot exceed the tolerance range of the originally set electrical impedance value, and the difference between the two cannot be too large, otherwise That is, it indicates that there is a problem in the process of the circuit board 10 .

Since the first measurement pad 202 and the second measurement pad 212 of Fig. 3A and Fig. 3B are all electrically connected to the ground circuit 16, the first measurement pad 202 and the third measurement pad 212 can be integrated into Fig. 3C, Fig. The fifth measurement pad 222 of 3D can be located in the middle of the second measurement pad 204 and the fourth measurement pad 214, while the other second measurement pad 204, the fourth measurement pad 214, the first measurement pad The relative position between the trace 206 and the second measurement trace 216 does not change, so the electrical impedance value of the first measurement trace 206 can be measured through the fifth measurement pad 222 and the second measurement pad 204, and The electrical impedance value of the second measurement trace 216 can be measured through the fifth measurement pad 222 and the fourth measurement pad 214 . It should be noted that the preferred location of the fifth measurement pad 222 may be equidistant from the second measurement pad 204 and the fourth measurement pad 214 , so that the best measurement effect can be obtained.

The impedance measurement structure of the embodiment of the present invention is fabricated on the surface of a circuit substrate, such as a substrate for chip packaging or a surface of a general printed circuit board, and is composed of a patterned circuit layer on the surface of the circuit substrate. Wherein, the impedance measurement structure is composed of a first measurement pad, a second measurement pad and a measurement trace, wherein the first measurement pad and the second measurement pad are arranged on the surface of the circuit substrate, and the first measurement pad The pad is electrically connected to the ground circuit of the circuit substrate through winding wires, and one end of the measurement trace is connected to the second measurement pad. Therefore, the impedance measuring instrument can be used to measure this section of the measurement trace through the two measurement pads respectively. Electrical impedance value. In addition, in addition to designing an impedance measurement structure 100 in Fig. 2A and Fig. 2B that can correspond to the detection of a single transmission line, another kind of impedance measurement structure 100 in Fig. 3A, Fig. 3B, Fig. 3C, and Fig. 3D that can correspond to the detection of differential signal transmission lines is also designed. The impedance measurement structure 200.

In summary, the impedance measuring structure of the present invention is suitable for detecting the electrical impedance value of a circuit substrate (such as a substrate for chip packaging or a printed circuit board). Whether the electrical impedance value of the measurement trace of the impedance measurement structure is within the tolerance range of the originally set electrical impedance value is used to indicate the line width, line height, line distance and dielectric layer thickness of the internal circuit of the circuit substrate. Whether it meets the requirements of the original design, so as to avoid unqualified circuit substrates from continuing to the next stage of assembly process, which will effectively reduce the process cost of the final actual product and improve its process qualification rate.

Although the present invention has been described above with an embodiment, it is not intended to limit the present invention. Any person familiar with the art can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall be determined by the claims.

Claims (13)

1. an impedance measuring structure is applicable to a circuit substrate, and wherein this circuit substrate has an earthed circuit, it is characterized by: this impedance measuring structure comprises:

One first measures weld pad, is disposed at the surface of this circuit substrate, and is electrically connected this earthed circuit;

One second measures weld pad, is disposed at the surface of this circuit substrate; And

One measures trace, is disposed at the surface of this circuit substrate, and an end of this measurement trace is connected to this second measurement weld pad.

2. impedance measuring structure as claimed in claim 1 is characterized by: the other end of this measurement trace is electrically connected this earthed circuit.

3. impedance measuring structure as claimed in claim 1 is characterized by: this circuit substrate has a patterned line layer, and this impedance measuring structure is made of this patterned line layer.

4. impedance measuring structure as claimed in claim 1 is characterized by: this circuit substrate has a reserve area and an excision zone, and this impedance measuring structure is positioned at the surface of this cut-away area.

5. an impedance measuring structure is applicable to a circuit substrate, and wherein this circuit substrate has an earthed circuit, it is characterized by: this impedance measuring structure comprises:

One first measures weld pad, is disposed at the surface of this circuit substrate, and is electrically connected this earthed circuit;

One second measures weld pad, is disposed at the surface of this circuit substrate;

One first measures trace, is disposed at the surface of this circuit substrate, and this first end of measuring trace is connected to this second measurement weld pad;

One the 3rd measures weld pad, to should first measuring the position of weld pad, and is disposed at the surface of this circuit substrate, and is electrically connected this earthed circuit;

One the 4th measures weld pad, to should second measuring the position of weld pad, and is disposed at the surface of this circuit substrate; And

One second measures trace, to should first measuring the position of trace, and is disposed at the surface of this circuit substrate, and this second end of measuring trace is connected to the 4th and measures weld pad.

6. impedance measuring structure as claimed in claim 5 is characterized by: this first other end and this second other end of measuring trace of measuring trace is electrically connected this earthed circuit.

7. impedance measuring structure as claimed in claim 5 is characterized by: this circuit substrate has a patterned line layer, and this impedance measuring structure is made of this patterned line layer.

8. impedance measuring structure as claimed in claim 5 is characterized by: this circuit substrate has a reserve area and an excision zone, and this impedance measuring structure is positioned at the surface of this cut-away area.

9. an impedance measuring structure is applicable to a circuit substrate, and wherein this circuit substrate has an earthed circuit, it is characterized by: this impedance measuring structure comprises:

One first measures weld pad, is disposed at the surface of this circuit substrate, and is electrically connected this earthed circuit;

One second measures weld pad, is disposed at the surface of this circuit substrate;

One first measures trace, is disposed at the surface of this circuit substrate, and this first end of measuring trace is connected to this second measurement weld pad;

One the 3rd measures weld pad, to should second measuring the position of weld pad, and is disposed at the surface of this circuit substrate; And

One second measures trace, to should first measuring the position of trace, and is disposed at the surface of this circuit substrate, and this second end of measuring trace is connected to the 3rd and measures weld pad.

10. impedance measuring structure as claimed in claim 9 is characterized by: this first other end and this second other end of measuring trace of measuring trace is electrically connected this earthed circuit.

11. impedance measuring structure as claimed in claim 9 is characterized by: this circuit substrate has a patterned line layer, and this impedance measuring structure is made of this patterned line layer.

12. impedance measuring structure as claimed in claim 9 is characterized by: this circuit substrate has a reserve area and an excision zone, and this impedance measuring structure is positioned at the surface of this cut-away area.

13. impedance measuring structure as claimed in claim 9 is characterized by: this first better position of measuring weld pad is configured in this second measurement weld pad and the 3rd and measures the weld pad equidistant.

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