Detection method of copper thickness of vias on flexible circuit boards

Abstract

The present invention discloses a method for detecting the thickness of copper holes in a flexible circuit board, comprising providing a flexible substrate, the flexible substrate comprising an effective area and a waste area; setting at least one copper hole detection area on the waste area of ​​the flexible substrate, each copper hole detection area being used to make a detection component for detecting the copper hole thickness of the effective area, the detection component comprising a plurality of copper-plated holes connected in series; making a hole to be detected on the effective area, and making corresponding detection components in each copper hole detection area respectively; performing electrical measurement on the hole to be detected, and performing electrical measurement on each detection component respectively, and obtaining the copper hole thickness detection result of the hole to be detected according to the electrical measurement results of all detection components. The present invention makes full use of the space of the waste area, combines the production process of the effective area to produce and electrically measure the detection component, does not need to add additional materials and process flow, realizes the detection of copper hole thickness, the process is simple and convenient, easy to implement, small workload, does not need to invest a lot of manpower cost, and is highly efficient.

Description

Technical Field

[0001] The invention relates to the technical field of flexible circuit board manufacturing, and in particular to a method for detecting the thickness of copper vias on a flexible circuit board. Background Art

[0002] Flexible printed circuit board (FPC: Flexible Printed Circuit Board, referred to as FPC) is a highly reliable and extremely flexible printed circuit board made of polyimide or polyester film as the substrate. Flexible circuit boards have the characteristics of high wiring density, light weight, thin thickness and good bendability. Flexible circuit boards are divided into single-sided boards, double-sided boards and multi-layer boards according to thickness and number of layers. FPCs with two or more layers require holes (blind holes / through holes) to conduct between different layers of boards. The quality of copper plating in the holes is becoming more and more important. If the copper plating in the holes is not good, there will be no copper in the holes or only a very thin layer of copper, which will affect the function of the product. Therefore, the detection of hole copper thickness is very important.

[0003] However, at present, the thickness of the copper plating in the hole cannot be visually inspected directly, and the only way is to set up a separate slicing process and confirm the hole wall thickness under a metallographic microscope through sampling slicing. The operation is inconvenient and inefficient, and it is necessary to invest in a separate process and manpower cost to do sampling slicing. In mass production, there is no way to slice each board to confirm the hole copper thickness. The process is cumbersome and the workload is large. Summary of the invention

[0004] In view of this, the present invention provides a method for detecting the thickness of via copper on a flexible circuit board to solve the problems of inconvenience, low efficiency and unsuitability for via copper thickness detection in mass production in the prior art of detecting via copper thickness by sampling and slicing.

[0005] The present invention provides a method for detecting the thickness of copper vias on a flexible circuit board, comprising:

[0006] Providing a flexible substrate, the flexible substrate comprising an active area and a waste area;

[0007] At least one copper hole detection area is arranged on the waste area of ​​the flexible substrate, each of the copper hole detection areas is used to make a detection component for detecting the copper hole thickness of the effective area, and the detection component includes a plurality of copper-plated holes connected in series;

[0008] Making holes to be inspected on the effective area, and making corresponding inspection components in each hole copper inspection area;

[0009] The holes to be inspected are electrically tested, and each of the inspection components is electrically tested at the same time, and the copper thickness test results of the holes to be inspected on the effective area are obtained based on the electrical test results of all the inspection components.

[0010] Optionally, the holes to be inspected are made on the effective area, and corresponding inspection components are respectively made in each hole copper inspection area, including:

[0011] Performing drilling processing on the effective area, and at the same time, performing drilling processing on all the hole copper detection areas according to a preset drilling layout, and forming a plurality of initial holes in each hole copper detection area;

[0012] Performing copper plating treatment on the effective area after drilling and all the hole copper detection areas at the same time;

[0013] The effective area after copper plating is etched to form the hole to be detected on the effective area; at the same time, according to the preset etching layout, all the hole copper detection areas after copper plating are etched to form a corresponding plurality of serially connected copper-plated holes on each hole copper detection area.

[0014] Optionally, the preset drilling layout includes a preset number of drilling holes, a drilling hole diameter, a drilling hole spacing and a drilling layout pattern; wherein the preset number of drilling holes is specifically the total number of all the initial holes formed by drilling processing in each hole copper detection area, the drilling hole diameter is specifically the hole diameter of each initial hole in each hole copper detection area, the drilling hole spacing is specifically the hole spacing between each adjacent two initial holes in each hole copper detection area, and the drilling layout pattern is specifically the pattern shape formed by all the initial holes in each hole copper detection area.

[0015] Optionally, the preset number of drilling holes in each of the hole copper detection areas is greater than or equal to 6.

[0016] Optionally, the preset number of drilling holes in each of the hole copper detection areas is greater than or equal to 20.

[0017] Optionally, the bore diameter of each of the copper hole detection areas is greater than or equal to 0.1 mm.

[0018] Optionally, the drilling hole spacing of each of the copper hole detection areas ranges from 0.37 to 0.1 mm.

[0019] Optionally, the drilling layout pattern of each of the copper hole detection areas includes any one of a strip shape, a U shape, a V shape and an L shape.

[0020] Optionally, the etching process is performed on all the copper-plated hole copper detection areas according to a preset etching layout, and a corresponding plurality of serially connected copper-plated holes are formed on each of the copper-plated hole detection areas, including:

[0021] According to the preset etching layout, the copper layer between every two adjacent initial holes in all the copper-plated hole detection areas is etched to form a corresponding plurality of serially connected copper-plated holes in each of the copper-plated hole detection areas.

[0022] Optionally, the preset etching layout includes an etching position and an etching spacing; wherein the etching position is specifically a position where the copper layer needs to be etched away between each adjacent two initial holes in each hole copper detection area; and the etching spacing is specifically a width of the copper layer that needs to be etched away between each adjacent two initial holes in each hole copper detection area.

[0023] Optionally, the etching spacing of each of the hole copper detection areas ranges from 0.05 to 0.1 mm.

[0024] Optionally, for any hole copper detection area after copper plating, starting from the first end of the hole copper detection area, the etching position between the first initial hole and the second initial hole is located on the copper layer of the first surface of the hole copper detection area, the etching position between the second initial hole and the third initial hole is located on the copper layer of the second surface of the hole copper detection area, the etching position between the third initial hole and the fourth initial hole is located on the copper layer of the first surface of the hole copper detection area, the etching position between the fourth initial hole and the fifth initial hole is located on the copper layer of the second surface of the hole copper detection area, and so on;

[0025] or

[0026] For any of the hole copper detection areas after copper plating treatment, starting from the first end of the hole copper detection area, the etching position between the first initial hole and the second initial hole is located on the copper layer on the second surface of the hole copper detection area, the etching position between the second initial hole and the third initial hole is located on the copper layer on the first surface of the hole copper detection area, the etching position between the third initial hole and the fourth initial hole is located on the copper layer on the second surface of the hole copper detection area, the etching position between the fourth initial hole and the fifth initial hole is located on the copper layer on the first surface of the hole copper detection area, and so on.

[0027] Optionally, the electrical measurement result includes a resistance change rate;

[0028] The electrical measurement of the holes to be inspected and the electrical measurement of each of the inspection components are performed simultaneously, and the copper thickness detection results of the holes to be inspected on the effective area are obtained according to the electrical measurement results of all the inspection components, including:

[0029] Performing immersion gold processing on the holes to be inspected, and at the same time performing immersion gold processing on all the inspection components according to a preset immersion gold layout, forming an electrical measuring point at both ends of each inspection component;

[0030] Electrically test the holes to be tested after the immersion gold treatment, and use the two electrical measuring points at both ends of each testing component to respectively electrically test all the copper-plated holes connected in series in each testing component to obtain the resistance change rate of each testing component;

[0031] The hole copper thickness detection result of the hole to be detected on the effective area is obtained according to the resistance change rate of all the detection components.

[0032] Optionally, the hole copper thickness detection result includes abnormal hole copper thickness and normal hole copper thickness;

[0033] The method of obtaining the hole copper thickness detection result of the hole to be detected on the effective area according to the resistance change rate of all the detection components includes:

[0034] comparing all of the resistance change rates with a preset electrical measurement threshold;

[0035] When at least one of the resistance value change rates is greater than the preset electrical measurement threshold, it is determined that the hole to be detected has an abnormal copper thickness;

[0036] When all the resistance change rates are less than or equal to the preset electrical measurement threshold, it is determined that the hole to be detected has a normal hole copper thickness.

[0037] Optionally, the preset immersion gold layout includes an immersion gold pattern and an immersion gold center distance; wherein, the immersion gold pattern is specifically a pattern shape formed after each detection component is processed by immersion gold, and the immersion gold center distance is specifically the distance between the center of the immersion gold pattern and the center of the copper-plated holes at both ends of the corresponding detection component.

[0038] Optionally, the gold-plated pattern of each detection component includes any one of a circle, a triangle and a rectangle.

[0039] Optionally, the center distance of the immersion gold of each detection component ranges from 0.85 to 5 mm.

[0040] Optionally, the flexible substrate is composed of one or more flexible circuit boards, and the flexible circuit board is any one of a single-layer board, a double-layer board and a multi-layer board.

[0041] Optionally, the number of the flexible substrates is one or more.

[0042] Beneficial effects of the present invention: the flexible substrate is provided with an effective area and a waste area, the effective area is an area for making a core circuit, and in order to realize the normal function of its core circuit, it is usually necessary to make holes (including through holes and blind holes) in the effective area and perform copper plating, and the copper-plated holes are also the objects of hole copper thickness detection, so the holes made in the effective area are holes to be detected; by setting at least one hole copper detection area in the waste area, and making corresponding detection components in each hole copper detection area while making the holes to be detected in the effective area, there is no need to add a separate production process of the detection component, and the detection component includes a plurality of copper-plated holes connected in series, which are consistent with the copper-plated structure of the holes to be detected, and can be used to detect the hole copper thickness of the holes to be detected made in the effective area; since the holes to be detected made in the effective area usually need to be detected, the present invention can detect the hole copper thickness of the holes to be detected made in the effective area by performing electrical measurement on the holes to be detected and each detection component is also tested separately, thereby screening out flexible board products with poor hole copper thickness (i.e., thin hole copper thickness), without adding a separate electrical measurement process of the detection component;

[0043] The method for detecting the thickness of copper holes on a flexible circuit board of the present invention can make full use of the space of the waste area, and combine the production process of the effective area to carry out the production and electrical measurement of the detection component, without adding additional materials and process flow, the detection of the thickness of the copper holes can be realized, and products with poor copper hole thickness can be detected; compared with the method of observation by sampling slices in the traditional technology, there is no need to add a slicing process, the operation process is simple and convenient, easy to implement, and efficient; by arranging the detection component on each flexible substrate, the copper hole thickness detection of each board in batch production can be realized according to the same method, the process is simple, the workload is small, and a large amount of manpower cost does not need to be invested. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the present invention in any way. In the accompanying drawings:

[0045] Figure 1 A flow chart of a method for detecting the thickness of copper vias on a flexible circuit board according to an embodiment of the present invention is shown;

[0046] Figure 2 A schematic diagram showing the layout design of the flexible substrate and the detection component in an embodiment of the present invention is shown;

[0047] Figure 3 It shows a flow chart of making a hole to be inspected and a detection component in an embodiment of the present invention;

[0048] Figure 4-1 A schematic cross-sectional structure diagram of the drilling hole diameter, drilling hole spacing, etching spacing, etching position and immersion gold center distance in the first implementation manner in the embodiment of the present invention is shown;

[0049] Figure 4-2 A schematic diagram of the three-dimensional structure of the drilling hole diameter, drilling hole spacing, etching spacing, etching position and immersion gold center distance in the first implementation manner in the embodiment of the present invention is shown;

[0050] Figure 4-3 A schematic cross-sectional structure diagram of the drilling hole diameter, drilling hole spacing, etching spacing, etching position and immersion gold center distance in the second implementation manner in the embodiment of the present invention is shown;

[0051] Figure 5-1 A schematic diagram showing a first drilling layout pattern in an embodiment of the present invention is shown;

[0052] Figure 5-2 A schematic diagram showing a second drilling layout pattern in an embodiment of the present invention is shown;

[0053] Figure 6 A flow chart of obtaining a hole copper thickness detection result in an embodiment of the present invention is shown;

[0054] Figure 7 A cross-sectional structural diagram of a single blind hole in an embodiment of the present invention is shown;

[0055] Figure 8-1 A schematic diagram showing electrical measuring points obtained after the copper-plated holes under the first drilling layout pattern are treated with immersion gold in an embodiment of the present invention;

[0056] Figure 8-2 A schematic diagram of electrical measuring points obtained after the copper-plated holes under the second drilling layout pattern are treated with immersion gold in an embodiment of the present invention is shown.

[0057] Description of reference numerals:

[0058] 1. Board, 2. Flexible circuit board, 3. Flexible substrate, 4. Detection component, 5. Copper layer, 6. PI layer, 7. Initial hole, 8. Copper-plated hole. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0060] Example

[0061] A method for detecting the thickness of copper vias on a flexible circuit board, such as Figure 1 As shown, the following steps are included:

[0062] S1, providing a flexible substrate, wherein the flexible substrate comprises an effective area and a waste area.

[0063] Specifically, the flexible substrate is composed of one or more flexible circuit boards, and the flexible circuit board is any one of a single-layer board, a double-layer board and a multi-layer board.

[0064] By using one or more flexible circuit boards as a flexible substrate, and making the holes to be inspected and the inspection components respectively based on the effective area and the waste area of ​​a flexible substrate, a suitable number of inspection components can be better arranged according to the layout space of the plate. On the one hand, the space in the waste area can be utilized to the maximum extent, and the hole copper thickness detection of all flexible circuit boards in the flexible substrate can be realized, and the hole copper thickness detection of mass production can be realized. On the other hand, there is no need to set a hole copper detection area and make inspection components for each flexible circuit board, which can effectively avoid the waste of materials caused by making too many inspection components.

[0065] Specifically, the number of the flexible substrates is one or more.

[0066] When there is one flexible substrate, and the flexible substrate is composed of one or more flexible circuit boards, the copper hole thickness detection of each flexible circuit board in the single flexible substrate can be realized; when there are multiple flexible substrates, and each flexible substrate is composed of one or more flexible circuit boards, the copper hole thickness detection of each flexible circuit board in the multiple flexible substrates can be realized. The above-mentioned setting method of the flexible substrate can more flexibly realize the copper hole thickness detection in mass production according to the layout space of the plate, greatly reducing the workload and improving production efficiency.

[0067] For example, in a specific embodiment, when there are many flexible circuit boards on the board in batch production, every four flexible circuit boards are used as a flexible substrate, such as Figure 2 As shown, in the waste area of ​​each flexible substrate ( Figure 2 Two hole copper detection areas (not shown in the figure) are set in the corner area of ​​each flexible substrate, and two detection components are made accordingly. By electrical testing each of the two detection components, it can be achieved Figure 2 Hole copper thickness detection of all flexible circuit boards in mass production; Figure 2 In the figure, 1 is a plate, 2 is a flexible circuit board, 3 is a flexible substrate, and 4 is a detection component. Figure 2 When the layout space of the plate shown is insufficient, multiple flexible circuit boards can be used as a flexible substrate in other ways, and multiple detection components can be made. For example, every 6 flexible circuit boards can be used as a flexible substrate, and 2 hole copper detection areas are set in the waste area of ​​each flexible substrate, and 2 detection components are made accordingly; Figure 2When the layout space of the plate shown is sufficient, multiple flexible circuit boards can be used as a flexible substrate in other ways, and multiple detection components can be made. For example, every two flexible circuit boards can be used as a flexible substrate, and two hole copper detection areas are set in the waste area of ​​each flexible substrate, and two detection components are made accordingly, or each flexible circuit board can be used as a flexible substrate, and one hole copper detection area is set in the waste area of ​​each flexible substrate, and one detection component is made accordingly. Of course, other reasonable design methods can also be adopted. The specific design method depends on the specific situation. The hole copper thickness detection method of the flexible substrate in different design methods is the same, which will not be listed here.

[0068] In this embodiment, the effective area of ​​the flexible substrate refers to the area where the circuit layer needs to be laid out, and the waste area generally refers to the corner area where the circuit layer does not need to be laid out. The effective area of ​​all flexible circuit boards in a flexible substrate is the effective area of ​​the flexible substrate, and the waste area of ​​all flexible circuit boards in a flexible substrate is the waste area of ​​the flexible substrate.

[0069] A single-layer board is specifically a single-sided copper-clad substrate composed of a single-layer copper foil and a flexible insulating base film (PI layer). A double-layer board is specifically a double-sided copper-clad substrate composed of a double-layer copper foil and a PI layer, and the double-layer copper foil is located on both sides of the PI layer. A multi-layer board is a double-sided copper-clad substrate with more than two layers, specifically a combination of a single-layer board and a double-layer board.

[0070] This embodiment takes a single 12-25-12 double-layer board (i.e., the thickness of the middle PI layer is 25 mm, and the thickness of the copper foil on both sides is 12 mm) as an example of a flexible substrate. The hole copper thickness detection of single-layer boards and multi-layer boards is similar to this, and will not be repeated in this embodiment.

[0071] like Figure 1 As shown, S2, at least one copper hole detection area is set on the waste area of ​​the flexible substrate, each of the copper hole detection area is used to make a detection component for detecting the copper hole thickness of the effective area, and the detection component includes a plurality of copper-plated holes connected in series.

[0072] By setting a copper hole detection area in the scrap area of ​​the flexible substrate, it is used for the subsequent production of detection components for detecting the copper hole thickness, without increasing the investment in materials and equipment, which can significantly save costs. At least one copper hole detection area is set in the scrap area, and according to the actual situation of the flexible substrate, the copper hole thickness of the flexible substrate can be more accurately detected through electrical measurement of a reasonable number of detection components.

[0073] The number of detection components is the same as the number of copper hole detection areas, and the number of copper hole detection areas is designed to be determined according to specific circumstances. For the convenience of description, this embodiment is described by taking an example of setting a copper hole detection area on the waste area of ​​the flexible substrate.

[0074] like Figure 1As shown, S3, making holes to be inspected on the effective area, and at the same time making corresponding inspection components in each hole copper inspection area.

[0075] Preferably, if Figure 3 As shown, S3 includes:

[0076] S31: drilling the effective area, and drilling all the hole copper detection areas according to a preset drilling layout, forming a plurality of initial holes in each hole copper detection area;

[0077] S32: performing copper plating on the effective area after the drilling process and all the hole copper detection areas at the same time;

[0078] S33: etching the effective area after the copper plating treatment to form the holes to be detected on the effective area; and etching all the hole copper detection areas after the copper plating treatment according to the preset etching layout to form a corresponding plurality of serially connected copper-plated holes on each hole copper detection area.

[0079] The drilling, copper plating and etching of the effective area are all conventional manufacturing processes on the effective area. While performing the conventional manufacturing process, each copper hole detection area is also drilled, copper plated and etched in turn to produce a detection component including multiple copper-plated holes in series. The detection component can be fully combined with the manufacturing process of the effective area without adding additional process flows. The process is simple and efficient. Among them, drilling the copper hole detection area according to the preset drilling layout and etching the copper hole detection area according to the preset etching layout can facilitate the formation of multiple copper-plated holes in series for detecting the copper hole thickness, and then facilitate the subsequent electrical measurement of multiple copper-plated holes in series to realize the detection of copper hole thickness and the screening of products with poor copper hole thickness.

[0080] It should be noted that the type of the initial hole formed by the drilling process in this embodiment can be a blind hole or a through hole. In this embodiment, the blind hole is taken as an example for description.

[0081] Preferably, in S31, the preset drilling layout includes a preset number of drilling holes, a drilling hole diameter, a drilling hole spacing and a drilling layout pattern; wherein the preset number of drilling holes is specifically the total number of all the initial holes formed by drilling processing in each hole copper detection area, the drilling hole diameter is specifically the hole diameter of each initial hole in each hole copper detection area, the drilling hole spacing is specifically the hole spacing between each adjacent two initial holes in each hole copper detection area, and the drilling layout pattern is specifically the pattern shape formed by all the initial holes in each hole copper detection area.

[0082] The preset drilling layout including the preset number of drilling holes, drilling hole diameter, drilling hole spacing and drilling layout pattern makes it easy to simultaneously produce multiple initial holes that meet the requirements during the drilling process in the effective area, thereby facilitating the production of a detection component that meets the requirements.

[0083] Preferably, the preset number of drilling holes in each of the hole copper detection areas is greater than or equal to 6.

[0084] Preferably, the preset number of drilling holes in each of the hole copper detection areas is greater than or equal to 20.

[0085] By drilling according to the preset number of holes in each hole copper detection area, the corresponding number of copper-plated holes in each detection component can be obtained, that is, the number of copper-plated holes is greater than or equal to 6, and further, the number of copper-plated holes is greater than or equal to 20. The preset number of holes can facilitate subsequent electrical testing to detect a large resistance change when the hole copper is thin, thereby more conveniently detecting flexible board products with poor hole copper thickness.

[0086] Specifically, the preset number of drill holes in this embodiment is 20, and correspondingly, the number of copper-plated holes formed in the detection component is also 20.

[0087] Preferably, the bore diameter of each of the copper hole detection areas is greater than or equal to 0.1 mm.

[0088] Since the aperture of the holes to be inspected in the effective area is usually greater than or equal to 0.1 mm, the above-mentioned drilling aperture is convenient for making initial holes similar to the aperture of the holes to be inspected in the effective area, thereby facilitating accurate detection of holes to be inspected with poor copper thickness, thereby screening out poor quality flexible substrates.

[0089] Specifically, the drilling hole diameter of this embodiment is 0.1 mm.

[0090] Preferably, the drilling hole spacing of each of the copper hole detection areas ranges from 0.37 to 0.1 mm.

[0091] By using the drilling hole diameter within the above range, sufficient space can be provided in the waste area to make a plurality of copper-plated holes in series.

[0092] Specifically, the drilling hole spacing in this embodiment is 0.37 mm.

[0093] Specifically, the schematic diagram of the drilling hole diameter and the drilling hole spacing in this embodiment is as follows: Figure 4-1 and Figure 4-2 As shown, in Figure 4-1 and Figure 4-2 In the figure, a1 is the drilling hole diameter, a2 is the drilling hole spacing, 5 is the copper layer, 6 is the PI layer, and 7 is the initial hole. It should be noted that in order to facilitate the display of the drilling hole diameter and drilling hole spacing, Figure 4-1 and Figure 4-2 Only 4 initial holes are shown, and the rest of the initial holes are omitted.

[0094] Preferably, the drilling layout pattern of each of the copper hole detection areas includes any one of a strip shape, a U shape, a V shape and an L shape.

[0095] By drilling the layout pattern, the detection components can be flexibly made according to the layout space, making full use of the waste area of ​​the flexible substrate.

[0096] Specifically, in a specific implementation of this embodiment, the drilling layout pattern is a long strip, such as Figure 5-1 In another specific implementation of this embodiment, the drilling layout pattern is U-shaped, such as Figure 5-2 As shown; in both embodiments, the number of initial holes is the same, which is 20. Figure 5-1 and Figure 5-2 Only 11 of the initial holes are shown, and the remaining initial holes are omitted; the wire width is also the same, all 0.9 mm (not shown in the figure).

[0097] Preferably, in S33, etching is performed on all the copper-plated hole copper detection areas according to a preset etching layout, and a corresponding plurality of serially connected copper-plated holes are formed on each of the copper-plated hole detection areas, including:

[0098] According to the preset etching layout, the copper layer between every two adjacent initial holes in all the copper-plated hole detection areas is etched to form a corresponding plurality of serially connected copper-plated holes in each of the copper-plated hole detection areas.

[0099] According to the preset etching layout, etching is performed on the copper layer between each two adjacent initial holes, thereby ensuring the formation of a plurality of serially connected copper-plated holes.

[0100] Preferably, the preset etching layout includes an etching position and an etching spacing; wherein the etching position is specifically a position where the copper layer needs to be etched away between each two adjacent initial holes in each hole copper detection area; and the etching spacing is specifically a width of the copper layer that needs to be etched away between each two adjacent initial holes in each hole copper detection area.

[0101] By etching the etching position and etching spacing, it is possible to accurately produce detection components with high detection accuracy.

[0102] Preferably, the etching spacing of each of the hole copper detection areas ranges from 0.05 to 0.1 mm.

[0103] Preferably, for any of the hole copper detection areas after copper plating treatment, starting from the first end of the hole copper detection area, the etching position between the first initial hole and the second initial hole is located on the copper layer on the first surface of the hole copper detection area, the etching position between the second initial hole and the third initial hole is located on the copper layer on the second surface of the hole copper detection area, the etching position between the third initial hole and the fourth initial hole is located on the copper layer on the first surface of the hole copper detection area, the etching position between the fourth initial hole and the fifth initial hole is located on the copper layer on the second surface of the hole copper detection area, and so on;

[0104] or

[0105] For any of the hole copper detection areas after copper plating treatment, starting from the first end of the hole copper detection area, the etching position between the first initial hole and the second initial hole is located on the copper layer on the second surface of the hole copper detection area, the etching position between the second initial hole and the third initial hole is located on the copper layer on the first surface of the hole copper detection area, the etching position between the third initial hole and the fourth initial hole is located on the copper layer on the second surface of the hole copper detection area, the etching position between the fourth initial hole and the fifth initial hole is located on the copper layer on the first surface of the hole copper detection area, and so on.

[0106] By alternately etching the copper layer between each two adjacent initial holes on the two surfaces of the hole copper detection area, it is possible to ensure that multiple copper-plated holes in series are produced in the hole copper detection area, which is convenient for subsequent electrical testing and detection of flexible board products with poor hole copper thickness.

[0107] In a specific implementation of this embodiment, Figure 4-1 and Figure 4-2 The four initial holes in the hole copper detection area shown (for ease of display, Figure 4-1 Only 4 initial holes are shown, and the remaining initial holes are omitted), and the etching spacing is 0.05mm. Figure 4-1 and Figure 4-2 In a4, starting from the first end (i.e., the left end) of the hole copper detection area, the etching position between the first initial hole and the second initial hole is located on the copper layer of the first surface (i.e., the upper surface) of the hole copper detection area, the etching position between the second initial hole and the third initial hole is located on the copper layer of the second surface (i.e., the lower surface) of the hole copper detection area, the etching position between the third initial hole and the fourth initial hole is located on the copper layer of the first surface (i.e., the upper surface) of the hole copper detection area, and the etching positions between each adjacent two initial holes not shown are similar.

[0108] In another specific implementation of this embodiment, Figure 4-3The four initial holes in the hole copper detection area shown (for ease of display, Figure 4-3 Similarly, only 4 initial holes are shown, and the remaining initial holes are omitted), and the etching spacing is 0.05mm. Figure 4-3 a4 in the figure, starting from the first end (i.e., the left end) of the hole copper detection area, the etching position between the first initial hole and the second initial hole is located on the copper layer of the second surface (i.e., the lower surface) of the hole copper detection area, the etching position between the second initial hole and the third initial hole is located on the copper layer of the first surface (i.e., the upper surface) of the hole copper detection area, the etching position between the third initial hole and the fourth initial hole is located on the copper layer of the second surface (i.e., the lower surface) of the hole copper detection area, and the etching positions between each adjacent two initial holes not shown are similar.

[0109] It should be noted that, in this embodiment, when manufacturing the holes to be inspected and the inspection components in S3, in addition to the process flow of drilling, copper plating and etching, it also includes the conventional process flow in the field of flexible circuit board manufacturing, which includes but is not limited to plasma treatment and dry film development treatment of the holes after drilling. The specific operation methods of the above-mentioned process flows of drilling, copper plating and etching and conventional process flows are all implemented by conventional operation methods. For example, the drilling process can be implemented by laser drilling, which is not listed here.

[0110] like Figure 1 As shown, S4, the holes to be inspected are electrically tested, and each of the inspection components is electrically tested respectively, and the copper thickness test results of the holes to be inspected on the effective area are obtained based on the electrical test results of all the inspection components.

[0111] Preferably, the electrical measurement result includes a resistance change rate;

[0112] like Figure 6 As shown, S4 includes:

[0113] S41: performing immersion gold processing on the hole to be inspected, and performing immersion gold processing on all the inspection components according to a preset immersion gold layout, and forming an electrical measuring point at both ends of each inspection component;

[0114] S42: Electrically test the holes to be tested after the immersion gold treatment, and use the two electrical measuring points at both ends of each testing component to respectively electrically test all the copper-plated holes connected in series in each testing component to obtain the resistance change rate of each testing component;

[0115] S43: Obtaining the hole copper thickness detection result of the to-be-detected hole on the effective area according to the resistance change rate of all the detection components.

[0116] Since immersion gold treatment is a conventional process for the holes to be inspected in the effective area, the detection components are simultaneously subjected to immersion gold treatment during the immersion gold treatment of the holes to be inspected, without the need to separately add immersion gold materials and immersion gold treatment processes; at the same time, electrical measurement of the holes to be inspected after immersion gold treatment is also a conventional process in the field of flexible circuit board manufacturing. While conducting electrical measurement of the holes to be inspected, electrical measurement points that can be connected to electrical measurement tools are formed at both ends of the detection components for electrical measurement, without the need to separately add electrical measurement processes, and the detection components can be used to detect the hole copper thickness of the holes to be inspected; since normal copper-plated holes and abnormal copper-plated holes (i.e., copper-plated holes with thin hole copper) will have different resistance values ​​due to different hole copper thicknesses, the resistance change rate is obtained through electrical measurement, and the abnormality of the hole copper thickness in the copper-plated holes can be intuitively judged based on the resistance change rate, thereby screening out flexible board products with poor hole copper thickness, thereby improving product yield.

[0117] The principle of electrical testing based on the detection component in this embodiment is as follows:

[0118] like Figure 7 As shown in the figure, for a single blind hole in the detection component, the calculation formula for its resistance during electrical measurement is: The meanings and units of the letters in the above formula are shown in Table 1, where: Figure 7 The d in the figure is the hole copper thickness.

[0119] Table 1 Meaning and unit of each letter in the single blind hole resistance formula

[0120]

[0121] During electrical measurement, it is necessary to connect wires for electrical measurement. The calculation formula for the resistance of the connected wires is: The meanings and units of the letters in the above formula are shown in Table 2.

[0122] Table 2 Meaning and units of letters in the wire resistance formula

[0123]

[0124]

[0125] When the preset number of drilling holes is 6, the resistance change comparison of the 6 copper-plated holes in series formed subsequently when the hole copper is bad (i.e., abnormal blind hole with thin hole copper thickness) and the hole copper is normal (i.e., normal blind hole with normal hole copper thickness) is shown in Table 3.

[0126]

[0127] It can be seen from Table 3 above that the normal blind hole copper thickness is 10 μm. If the blind hole is abnormal after copper plating, the hole copper is only 5 μm thin. If the detection component set in this board has only one blind hole, the resistance change rate of a single blind hole when the hole copper is abnormal and the hole copper is normal is only 3.09%, and the resistance change rate is calculated by (7-6.79) / 6.79, which is much lower than the 15% resistance change rate control threshold in the electrical measurement. Therefore, the electrical measurement at this time cannot detect and control the hole copper thickness based on the resistance change rate caused by the thin hole copper; if a detection component with 6 copper-plated holes (specifically copper-plated blind holes) in series in this embodiment is designed separately, the resistance change rate can reach 15.50%, and the resistance change rate is calculated by (9.17-7.94) / 7.94. Then, the electrical measurement at this time can control such a large resistance change, thereby detecting the flexible substrate with thin hole copper.

[0128] When the preset number of drilling holes is 20, the resistance change comparison of the 20 copper-plated holes in series formed subsequently when the hole copper is bad (i.e., abnormal blind hole with thin hole copper thickness) and the hole copper is normal (i.e., normal blind hole with normal hole copper thickness) is shown in Table 4.

[0129]

[0130]

[0131] It can be seen from Table 4 above that if a detection component with 20 copper-plated holes (specifically copper-plated blind holes) in series in this embodiment is designed separately, the resistance change rate can reach 20.98%, and the resistance change rate is calculated by (23.64-19.54) / 19.54. At this time, the resistance change rate is greater than the resistance change rate control threshold of 15% in the electrical measurement, which is more convenient for electrical measurement control and detection of flexible substrates with thin copper holes.

[0132] Preferably, the hole copper thickness detection result includes abnormal hole copper thickness and normal hole copper thickness;

[0133] S43 includes:

[0134] comparing all of the resistance change rates with a preset electrical measurement threshold;

[0135] When at least one of the resistance value change rates is greater than the preset electrical measurement threshold, it is determined that the hole to be detected has an abnormal copper thickness;

[0136] When all the resistance change rates are less than or equal to the preset electrical measurement threshold, it is determined that the hole to be detected has a normal hole copper thickness.

[0137] By comparing the resistance change rate obtained by electrical measurement of each detection component with the preset electrical measurement threshold, the size of each resistance change rate and the preset electrical measurement threshold can be obtained. When at least one of the resistance change rates is greater than the preset electrical measurement threshold, it means that the copper-plated hole in the corresponding flexible substrate after copper plating has a large change in resistance due to the phenomenon of thin hole copper. The copper plating process of the copper-plated hole and the copper plating process of the hole to be detected in the flexible substrate are carried out synchronously, so it can further reflect the phenomenon of thin hole copper in the hole to be detected, that is, it is determined that the hole copper thickness of the hole to be detected is abnormal; conversely, when all resistance change rates are less than or equal to the preset electrical measurement threshold, it means that the hole copper to be detected does not have a thin hole copper phenomenon, that is, it is determined that the hole copper thickness of the hole to be detected is normal.

[0138] The preset electrical measurement threshold, i.e., the resistance change rate control threshold in the electrical measurement, is 15% in this embodiment.

[0139] Preferably, the preset immersion gold layout includes an immersion gold pattern and an immersion gold center distance; wherein, the immersion gold pattern is specifically a pattern shape formed after each detection component is processed by immersion gold, and the immersion gold center distance is specifically the distance between the center of the immersion gold pattern and the center of the copper-plated holes at both ends of the corresponding detection component.

[0140] Preferably, the gold-plated pattern of each of the detection components includes any one of a circle, a triangle and a rectangle.

[0141] Preferably, the center distance of the immersion gold of each detection component ranges from 0.85 to 5 mm.

[0142] Through the above-mentioned immersion gold center distance, the immersion gold area can be accurately positioned. On the one hand, it can form an electrical testing point that is convenient for the electrical testing tool to connect, so that the electrical testing can be carried out smoothly; on the other hand, it can avoid occupying a large layout space and avoiding the waste of immersion gold materials; the above-mentioned immersion gold pattern has a simple shape and is easy to implement, which can ensure better implementation of subsequent electrical testing.

[0143] In a specific implementation of performing immersion gold treatment on the detection component to form two electrical measuring points, the area not requiring immersion gold is covered by a dry film, and when the immersion gold area is exposed according to the immersion gold pattern, the immersion gold area is further immersed gold treated to achieve the formation of two electrical measuring points.

[0144] It should be noted that, in this embodiment, the process of performing immersion gold treatment on the detection component in S4 is carried out simultaneously with the process of performing immersion gold treatment in the effective area. The effective area is provided with the core circuit layer of the flexible board, and its corresponding immersion gold treatment is a conventional process in the field of flexible circuit board production. Therefore, while performing immersion gold treatment on the effective area, the area in the hole copper detection area that does not require immersion gold is covered with a dry film, and the immersion gold area is exposed according to the immersion gold pattern, so that the electrical test points required for electrical testing can be formed by using only the conventional production process of the effective area, without the need to set up a separate production process.

[0145] Specifically, in this embodiment, the immersion gold pattern is circular, forming two circular electrical measurement points, respectively as follows: Figure 8-1 and Figure 8-2 A and B in Figure 8-1 and Figure 8-2 The 8 in the figure is a copper-plated hole. Figure 8-1 and Figure 8-2 Only some copper-plated holes are shown, and the rest are omitted; the center distance of immersion gold is 0.85mm, such as Figure 4-1 , Figure 4-2 and Figure 4-3 a3 shown.

[0146] In the above detection method of this embodiment, the flexible substrate is provided with an effective area and a waste area. The effective area is an area where a core circuit is made. In order to realize the normal function of its core circuit, it is usually necessary to make holes (including through holes and blind holes) in the effective area and perform copper plating. The copper-plated holes are also the objects of hole copper thickness detection. Therefore, the holes made in the effective area are holes to be detected; by setting at least one hole copper detection area in the waste area, and making corresponding detection components in each hole copper detection area while making the holes to be detected in the effective area, there is no need to add a separate production process of the detection component, and the detection component includes a plurality of copper-plated holes connected in series, which are consistent with the copper-plated structure of the holes to be detected, and can be used to detect the hole copper thickness of the holes to be detected made in the effective area; because the holes to be detected made in the effective area usually need to be detected, the present invention can detect the hole copper thickness of the holes to be detected made in the effective area by performing electrical measurement on the holes to be detected and each detection component is also tested separately, thereby screening out flexible board products with poor hole copper thickness (i.e., thin hole copper thickness) without adding a separate electrical measurement process of the detection component.

[0147] The method for detecting the thickness of copper vias on a flexible circuit board of the present embodiment can make full use of the space in the waste area, and combine the production process of the effective area to manufacture and electrically test the detection component, without adding additional materials and process flow, to realize the detection of the thickness of the copper vias, and detect products with poor copper via thickness; compared with the method of observation by sampling slices in the traditional technology, there is no need to add a slicing process, the operation process is simple and convenient, easy to implement, and efficient; by setting the detection component on each flexible substrate, the copper via thickness detection of each board in batch production can be realized in the same way, the process is simple, the workload is small, and a large amount of manpower cost does not need to be invested.

[0148] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for detecting the thickness of copper vias on a flexible circuit board, characterized in that: include: Providing a flexible substrate, the flexible substrate comprising an active area and a waste area; At least one copper hole detection area is arranged on the waste area of ​​the flexible substrate, each of the copper hole detection areas is used to make a detection component for detecting the copper hole thickness of the effective area, and the detection component includes a plurality of copper-plated holes connected in series; Making holes to be inspected on the effective area, and making corresponding inspection components in each hole copper inspection area; Electrically test the holes to be tested, and at the same time, electrically test each of the detection components, and obtain the hole copper thickness detection results of the holes to be tested on the effective area according to the electrical test results of all the detection components; The method of making a hole to be detected on the effective area and making a corresponding detection component in each hole copper detection area includes: Performing drilling processing on the effective area, and at the same time, performing drilling processing on all the hole copper detection areas according to a preset drilling layout, and forming a plurality of initial holes in each hole copper detection area; Performing copper plating treatment on the effective area after drilling and all the hole copper detection areas at the same time; The effective area after copper plating is etched to form the hole to be detected on the effective area; at the same time, according to the preset etching layout, all the hole copper detection areas after copper plating are etched to form a corresponding plurality of serially connected copper-plated holes on each hole copper detection area; The electrical measurement results include resistance change rate; The electrical measurement of the holes to be inspected and the electrical measurement of each of the inspection components are performed simultaneously, and the copper thickness detection results of the holes to be inspected on the effective area are obtained according to the electrical measurement results of all the inspection components, including: Performing immersion gold processing on the holes to be inspected, and at the same time performing immersion gold processing on all the inspection components according to a preset immersion gold layout, forming an electrical measuring point at both ends of each inspection component; Electrically test the holes to be tested after the immersion gold treatment, and use the two electrical measuring points at both ends of each testing component to respectively electrically test all the copper-plated holes connected in series in each testing component to obtain the resistance change rate of each testing component; The hole copper thickness detection result of the hole to be detected on the effective area is obtained according to the resistance change rate of all the detection components.

2. The method for detecting the thickness of copper vias on a flexible circuit board according to claim 1, characterized in that: The preset drilling layout includes a preset number of drilling holes, a drilling hole diameter, a drilling hole spacing and a drilling layout pattern; wherein the preset number of drilling holes is specifically the total number of all the initial holes formed by drilling processing in each hole copper detection area, the drilling hole diameter is specifically the hole diameter of each initial hole in each hole copper detection area, the drilling hole spacing is specifically the hole spacing between each adjacent two initial holes in each hole copper detection area, and the drilling layout pattern is specifically the pattern shape formed by all the initial holes in each hole copper detection area.

3. The method for detecting the thickness of copper vias on a flexible circuit board according to claim 2, characterized in that: The preset number of drilling holes in each hole copper detection area is greater than or equal to 20.

4. The method for detecting the thickness of copper vias on a flexible circuit board according to claim 2, characterized in that: The bore diameter of each of the copper hole detection areas is greater than or equal to 0.1 mm.

5. The method for detecting the thickness of copper vias on a flexible circuit board according to claim 2, characterized in that: The drilling hole spacing of each of the copper hole detection areas ranges from 0.37 to 0.1 mm.

6. The method for detecting the thickness of copper vias on a flexible circuit board according to claim 2, characterized in that: The drilling layout pattern of each hole copper detection area includes any one of a long strip shape, a U shape, a V shape and an L shape.

7. The method for detecting the thickness of copper vias on a flexible circuit board according to claim 1, characterized in that: The etching process is performed on all the copper-plated hole copper detection areas according to the preset etching layout, and a corresponding plurality of serially connected copper-plated holes are formed on each of the hole copper detection areas, including: According to the preset etching layout, the copper layer between every two adjacent initial holes in all the copper-plated hole detection areas is etched to form a corresponding plurality of serially connected copper-plated holes in each of the copper-plated hole detection areas.

8. The method for detecting the thickness of copper vias on a flexible circuit board according to claim 7, characterized in that: The preset etching layout includes an etching position and an etching spacing; wherein the etching position is specifically a position where the copper layer needs to be etched away between each adjacent two initial holes in each hole copper detection area; and the etching spacing is specifically a width of the copper layer that needs to be etched away between each adjacent two initial holes in each hole copper detection area.

9. The method for detecting the thickness of copper vias on a flexible circuit board according to claim 8, characterized in that: The etching spacing of each hole copper detection area ranges from 0.05 to 0.1 mm.

10. The method for detecting the thickness of copper vias on a flexible circuit board according to claim 8, characterized in that: For any of the hole copper detection areas after copper plating, starting from the first end of the hole copper detection area, the etching position between the first initial hole and the second initial hole is located on the copper layer on the first surface of the hole copper detection area, the etching position between the second initial hole and the third initial hole is located on the copper layer on the second surface of the hole copper detection area, the etching position between the third initial hole and the fourth initial hole is located on the copper layer on the first surface of the hole copper detection area, the etching position between the fourth initial hole and the fifth initial hole is located on the copper layer on the second surface of the hole copper detection area, and so on; or For any of the hole copper detection areas after copper plating treatment, starting from the first end of the hole copper detection area, the etching position between the first initial hole and the second initial hole is located on the copper layer on the second surface of the hole copper detection area, the etching position between the second initial hole and the third initial hole is located on the copper layer on the first surface of the hole copper detection area, the etching position between the third initial hole and the fourth initial hole is located on the copper layer on the second surface of the hole copper detection area, the etching position between the fourth initial hole and the fifth initial hole is located on the copper layer on the first surface of the hole copper detection area, and so on.

11. The method for detecting the thickness of copper vias on a flexible circuit board according to claim 1, characterized in that: The hole copper thickness detection result includes abnormal hole copper thickness and normal hole copper thickness; The method of obtaining the hole copper thickness detection result of the hole to be detected on the effective area according to the resistance change rate of all the detection components includes: comparing all of the resistance change rates with a preset electrical measurement threshold; When at least one of the resistance value change rates is greater than the preset electrical measurement threshold, it is determined that the hole to be detected has an abnormal copper thickness; When all the resistance change rates are less than or equal to the preset electrical measurement threshold, it is determined that the hole to be detected has a normal hole copper thickness.

12. The method for detecting the thickness of copper vias on a flexible circuit board according to claim 1, characterized in that: The preset immersion gold layout includes an immersion gold pattern and an immersion gold center distance; wherein, the immersion gold pattern is specifically a pattern shape formed after each detection component is processed by immersion gold, and the immersion gold center distance is specifically the distance between the center of the immersion gold pattern and the center of the copper-plated holes at both ends of the corresponding detection component.

13. The method for detecting the thickness of copper vias on a flexible circuit board according to claim 12, characterized in that: The immersion gold pattern of each detection component includes any one of a circle, a triangle and a rectangle.

14. The method for detecting the thickness of copper vias on a flexible circuit board according to claim 12, characterized in that: The center distance of the immersion gold of each detection component ranges from 0.85 to 5 mm.

15. The method for detecting the thickness of copper vias on a flexible circuit board according to any one of claims 1 to 14, characterized in that: The flexible substrate is composed of one or more flexible circuit boards, and the flexible circuit board is any one of a single-layer board, a double-layer board and a multi-layer board.

16. The method for detecting the thickness of copper vias on a flexible circuit board according to claim 15, characterized in that: The number of the flexible substrate is one or more.

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