A manufacturing process for partial metallization of through holes and PCB

Abstract

The present invention relates to the field of PCB technology, and discloses a manufacturing process for partial metallization of through holes and a PCB. The manufacturing process for partial metallization of through holes includes: providing a metal detection needle, a hollow plating resist and a printed circuit board with through holes, and constructing a test circuit; using the hole mouth of the intended non-metallized hole section away from the target plugging hole depth position as the entrance end, plugging the plating resist into the through hole, monitoring the electrical connection state of the test circuit in real time during the plugging process, and stopping the insertion of the plating resist when the electrical connection state switches from the disconnected state to the conductive state; after stopping the insertion of the plating resist, copper plating is performed on the through hole to form an electroplating layer on the hole wall of the intended metallized hole section of the through hole. The embodiment of the present invention can eliminate the problem that the residual stub cannot be completely removed, and avoid the interference of the residual stub on the signal; and the plating resist can be plugged into any depth position according to the requirements to achieve any different partial metallization requirements, and has strong versatility.

Description

Technical Field

[0001] The present invention relates to the technical field of PCB (Printed Circuit Boards), and in particular to a manufacturing process for partially metallizing a through hole and a PCB. Background Art

[0002] Partial through-hole metallization refers to a process that retains the hole wall copper between the effective network layers inside the through-hole and removes the invalid hole wall copper layer that is useless for signal transmission and affects the signal transmission quality. This is not only beneficial to reduce PCB signal transmission loss and improve signal transmission integrity, but also can improve the overall wiring density of the PCB and realize multiple networks in one hole.

[0003] At present, the conventional process in the PCB industry is to remove part of the hole wall copper by mechanical back drilling to achieve disconnection between designated layers. However, this process has disadvantages. It cannot completely and accurately remove the designated part of the hole copper, leaving some invalid hole wall copper "stubs", affecting the signal transmission quality. Summary of the invention

[0004] The object of the present invention is to provide a manufacturing process for partially metallizing a through hole and a PCB to solve the problem that the hole copper of a designated part cannot be completely and accurately removed.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] A manufacturing process for partially metallizing a through hole, comprising the steps of:

[0007] Provide metal detection needles, hollow resists and printed circuit boards with through holes, and build test circuits;

[0008] Wherein, the through hole includes adjacent to each other along its axial direction a pseudo non-metallized hole segment and a pseudo metallized hole segment, and the junction position between the pseudo non-metallized hole segment and the pseudo metallized hole segment is the target plugging depth position;

[0009] The plating resist is used to be inserted into the through hole and fit with the hole wall of the through hole to be non-metallized hole section, but not fit with the hole wall of the through hole to be metallized hole section, so as to prevent copper plating / electroplating solution from contacting the hole wall of the through hole to be non-metallized hole section;

[0010] The outer side wall of the plating resist is coated with a first conductive layer, the hole wall of the through hole is provided with a second conductive layer at a target plugging hole depth position, the second conductive layer is fixedly electrically connected to a metal detection needle through an inner layer pattern, and the metal detection needle is fixedly electrically connected to the first conductive layer of the plating resist, so that the first conductive layer, the second conductive layer, the metal detection needle, and the first conductive layer form the test circuit;

[0011] Taking the hole opening of the proposed non-metallized hole section far away from the target plugging hole depth position as the entrance end, inserting the plating resist into the through hole, monitoring the electrical connection state of the test circuit in real time during the insertion process, and stopping inserting the plating resist when the electrical connection state switches from a disconnected state to a conductive state;

[0012] After the insertion of the plating resist is stopped, copper electroplating is performed on the through hole to form an electroplating layer on the hole wall of the to-be-metallized hole section of the through hole.

[0013] Optionally, a metallized test hole is further provided on the printed circuit board, the metallized test hole is electrically connected to the inner layer pattern, and the metal detection needle is partially inserted into the metallized test hole.

[0014] Optionally, the plating resistance member includes a hollow support tube and a rubber layer, the rubber layer wraps around the entire outer side wall of the hollow support tube, and the hollow support tube is made of high crystalline polypropylene (HCPP).

[0015] Optionally, the through hole is divided into two hole segments along its axial direction, consisting of the pseudo-non-metallized hole segment and the pseudo-metallized hole segment; the length of the plating resist is not less than the depth of the pseudo-non-metallized hole segment.

[0016] Optionally, the through hole is divided into at least three hole segments along its axial direction, which are composed of the pseudo-non-metallized hole segments and the pseudo-metallized hole segments cross-distributed;

[0017] The number of the plating resists is the same as the number of the to-be-non-metallized hole segments and corresponds one to one, and the length of each plating resist is equal to the depth of the corresponding to-be-non-metallized hole segment;

[0018] When the number of the plating resists is at least two, each of the plating resists is provided with a corresponding target plugging hole depth position, and each target plugging hole depth position is formed with a corresponding test circuit; when each plating resist is plugged into the through hole respectively, the plugging hole depth of each plating resist is controlled by the corresponding test circuit.

[0019] Optionally, windows are respectively made between the hole wall of the quasi-non-metallized hole segment and each inner layer pattern at a corresponding depth position.

[0020] Optionally, the plug hole end of the plating resistance member is an oblique cut.

[0021] Optionally, the outer diameter of the plating resistance is 0.10 mm-0.25 mm larger than the diameter of the through hole on one side.

[0022] A PCB comprises a through hole, wherein the through hole is manufactured according to any one of the above-mentioned manufacturing processes for partially metallizing the through hole.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] According to the embodiment of the present invention, it is only necessary to set a second conductive layer at the junction of the intended non-metallized hole section and the intended metallized hole section of the through hole according to the partial metallization requirements, and then insert a plating resist with the first conductive layer coated on the outer wall into the through hole, and control the plugging depth based on a test loop constructed by the first conductive layer and the second conductive layer, and then perform copper electroplating on the through hole inserted with the plating resist to obtain a partially metallized through hole. Compared with the prior art method, the problem of residual stub being unable to be completely removed can be eliminated, and the interference of residual stub to the signal can be avoided; moreover, the plating resist can be inserted into any depth position according to the requirements to achieve any different partial metallization requirements, and the versatility is strong. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 A flow chart of a method for partially metallizing a through hole provided in an embodiment of the present invention.

[0027] Figure 2 A schematic diagram of the manufacturing process of partial metallization of a through hole provided in an embodiment of the present invention.

[0028] Figure 3 A cross-sectional view of a plating resist provided in an embodiment of the present invention.

[0029] Explanation of the reference numerals: plating resist 1 , printed circuit board 2 , through hole 3 , hollow support tube 11 , rubber layer 12 , metal detection needle 4 , first conductive layer 5 , second conductive layer 6 . DETAILED DESCRIPTION

[0030] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions 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 embodiments described below are only 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 ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In order to solve the problems of complicated procedures and inability to completely remove the invalid hole copper in the existing invalid hole copper removal solutions, the embodiments of the present invention provide a new solution. First, a first conductive layer 5 is coated on the side wall of a novel plating resist 1 with a plating resist function, and a second conductive layer 6 is laid at the copper disconnection position of the through hole 3 to be partially metallized, and a test circuit including the first conductive layer 5 and the second conductive layer 6 is constructed. Then, the plating resist 1 is inserted into the through hole 3 until the electrical connection state of the test circuit changes, and then the through hole 3 is subjected to conventional copper electroplating, so that a plating layer can be plated on part of the hole wall of the through hole 3. At the same time, part of the hole wall cannot be plated with the electroplating layer due to the effect of the plating resist 1.

[0032] Please refer to Figure 1 and Figure 2 The embodiment of the present invention provides a manufacturing process for partially metallizing a through hole, comprising the steps of:

[0033] Step 101, providing a metal detection needle 4, a hollow plating resist 1 and a printed circuit board 2 having a through hole 3 to be partially metallized, and constructing a test circuit;

[0034] The partially metallized through hole 3 includes adjacent non-metallized hole segments and metallized hole segments along its axial direction, and the junction position of the non-metallized hole segment and the metallized hole segment is used as the target plugging depth position of the plating resist 1.

[0035] The plating resist 1 is used to be inserted into the through hole 3 to a target plugging depth position, and is in contact with the hole wall of the through hole 3 to be non-metallized hole section, but not in contact with the hole wall of the through hole 3 to be metallized hole section, so as to prevent the copper plating / electroplating solution from contacting the hole wall of the non-metallized hole section.

[0036] The outer wall of the plating resist 1 is coated with a first conductive layer 5, and the hole wall of the through hole 3 is provided with a second conductive layer 6 at the target plugging depth position, and the second conductive layer 6 is fixedly electrically connected to the metal detection needle 4 through the inner layer pattern, and the metal detection needle 4 is fixedly electrically connected to the first conductive layer 5 of the plating resist 1, so that the first conductive layer 5, the second conductive layer 6, the metal detection needle 4, and the first conductive layer 5 form a test circuit.

[0037] Step 102, using the hole opening of the intended non-metallized hole section far away from the target plugging depth position as the entrance end, inserting the plating resist 1 into the through hole 3, monitoring the electrical connection status of the test circuit in real time during the plugging process, and stopping inserting the plating resist 1 when the electrical connection status switches from the disconnected state to the conductive state.

[0038] It should be noted that, during the plugging process, when the resist 1 has not reached the target plugging depth, the first conductive layer 5 on the outer wall of the resist 1 contacts the hole wall portion of the quasi-non-metallized hole section of the through hole 3, and cannot contact the second conductive layer 6 at the target plugging depth, thereby causing the first conductive layer 5 to be disconnected from the second conductive layer 6, resulting in the test circuit being disconnected;

[0039] When the resist 1 reaches the target plug hole depth position, the first conductive layer 5 on the outer wall of the resist 1 begins to contact the second conductive layer 6 at the target plug hole depth position, so that an electrical connection is established between the first conductive layer 5 and the second conductive layer 6, causing the test circuit to switch from an open state to an on state;

[0040] When the plating resist 1 continues to be inserted downward from the target plugging hole depth position and has not yet completely passed the target plugging hole depth position, the first conductive layer 5 of the outer wall of the plating resist 1 is always in contact and connected with the second conductive layer 6, so that the test circuit remains in a conducting state;

[0041] When the entire plating resist 1 completely passes through the target plug hole depth position, the first conductive layer 5 and the second conductive layer 6 of the outer wall of the plating resist 1 are no longer in contact and connected, and the test circuit is switched from the on state to the off state.

[0042] Therefore, in the embodiment of the present invention, the current depth position of the plating resist 1 can be determined by real-time monitoring of the electrical connection status of the test loop, thereby accurately controlling the plugging depth of the plating resist 1 .

[0043] Step 103 , after stopping inserting the plating resist 1 , copper electroplating is performed on the through hole 3 to form an electroplating layer on the hole wall of the to-be-metallized hole section of the through hole 3 .

[0044] It is understandable that the outer diameter of the plating resist 1 matches the aperture of the through hole 3, so that when the plating resist 1 is plugged to the target plugging depth position, it can fit with the hole wall of the through hole 3 at the corresponding position to achieve the plating resist function for this part of the hole wall.

[0045] During the copper plating process, the hole section to be non-metallized cannot be in contact with the copper plating / electroplating solution due to the shielding of the plating resist 1, so the surface cannot be plated with the electroplating layer; however, the hole section to be metallized can be fully in contact with the copper plating / electroplating solution because the surface is not blocked, so the surface can be smoothly plated with the electroplating layer. Finally, only the hole wall of the hole section to be metallized of the through hole 3 is metallized.

[0046] In practical applications, the depth position of the second conductive layer 6 can be adjusted according to actual needs to achieve different partial metallization requirements. Since the position of the second conductive layer 6 is the boundary position between the intended metallized hole segment and the intended non-metallized hole segment, and the resist 1 can be accurately controlled to stay at the target plug hole depth position, the embodiment of the present invention can simply and accurately achieve partial metallization of the through hole 3. Compared with the traditional back drilling method and etching method, it can not only completely and accurately achieve the separation of the hole copper at the specified position without leaving any residual piles, but also has a simple process, a short cycle, and a low cost.

[0047] For the convenience of testing, a metallized test hole is also provided on the printed circuit board 2, the metallized test hole is electrically connected to the inner layer pattern, and the metal detection needle 4 is partially inserted into the metallized test hole. In this way, the electrical connection operation between the metal detection needle 4 and the first conductive layer 5 on the outer side wall of the resist 1 is facilitated.

[0048] The plating resist 1 can be any structure that can perform the plating resist function; to achieve the plating resist effect, the plating resist 1 can be made of any material such as non-conductive plastic, as long as it cannot penetrate the copper plating / electroplating solution to cause the copper plating / electroplating solution to contact the inner wall of the through hole 3 at the corresponding position.

[0049] In an alternative embodiment, see Figure 3 The plating resist 1 includes a hollow support tube 11 and a rubber layer 12, and the rubber layer 12 wraps the entire outer wall of the hollow support tube 11. The hollow support tube 11 has the characteristic of being hollow, which ensures that the copper plating / electroplating solution can be fully exchanged during the copper plating process, so as to achieve uniformity and flatness of the electroplating layer on the hole wall surface of the through hole 3 to be metallized.

[0050] In order to further improve the reusability of the plating resistor 1, the hollow support tube 11 is made of a non-polar material, such as HCPP (high crystalline polypropylene). When immersed in copper plating / electroplating solution, the non-polar material can prevent the surface of the plating resistor 1 from being corroded or forming an electroplating layer due to a chemical reaction between the surface of the plating resistor 1 and the solution.

[0051] In addition, the through hole 3 can be divided into only two hole segments along its axial direction, consisting of a pseudo-non-metallized hole segment and a pseudo-metallized hole segment; in this case, the length of the plating resist 1 is not less than the depth of the pseudo-non-metallized hole segment.

[0052] When the length of the resist 1 is substantially equal to the depth of the intended non-metallized hole segment, the outer end of the resist 1 is substantially level with the hole opening of the intended non-metallized hole segment when the resist 1 is plugged into place. At this time, the method of controlling the plugging depth according to the test loop can effectively improve the plugging accuracy compared with the method of controlling the plugging depth according to the external observation result of whether the outer end of the resist 1 is level with the hole opening of the intended non-metallized hole segment. This is because: during the lamination process, under the influence of various environmental factors such as high temperature and high pressure, the theoretical depth and actual depth of the intended non-metallized hole segment and the intended metallized hole segment of the through hole 3 on the printed circuit board 2 have a certain deviation, and the resist 1 is made based on the theoretical depth of the intended non-metallized hole segment, so it is not accurate enough to control the plugging depth only by external observation; and the electrical conduction test method provided in this embodiment, because the second conductive layer 6 located at the junction of the intended non-metallized hole segment and the intended metallized hole segment is used as the judgment basis, and the depth position of the second conductive layer 6 is not affected by various factors such as high temperature and high pressure, so it has a higher control accuracy.

[0053] Of course, you can also choose to remove the plating resist 1. Specifically, different removal methods can be used according to the specific material or structure of the plating resist 1, and the embodiment of the present invention is not limited to this. Here is a universal method for removing the plating resist 1: directly pull the plating resist 1 out of the through hole 3 manually or through a power module. At this time, if the length of the plating resist 1 is greater than the depth of the intended non-metallized hole section, after the plating resist 1 is plugged into the hole, part of the plating resist 1 is still exposed outside the hole, and the staff or the power module can act on the exposed end of the plating resist 1 to perform the pull-out operation, which is simple and quick.

[0054] In another optional embodiment, the through hole 3 is divided into at least three hole segments along its axial direction, which are composed of a cross-distribution of quasi-non-metallized hole segments and quasi-metallized hole segments; at this time, the number of plating resists 1 is the same as the number of quasi-non-metallized hole segments and corresponds one to one, and the length of each plating resist 1 is equal to the depth of the corresponding quasi-non-metallized hole segment; when the number of plating resists 1 is at least two, each plating resist 1 is correspondingly provided with a target plugging depth position, and a corresponding test circuit is formed at each target plugging depth position; when each plating resist 1 is respectively plugged into the through hole 3, the plugging depth of each plating resist 1 is controlled by the corresponding test circuit.

[0055] Based on this, multiple network layers can be realized in the same through hole 3 by means of at least two plating resists 1. When plugging the hole, the power module can be used to sequentially plug each plating resist 1 from the inside to the outside. The plugging depth control of each plating resist 1 is the same as the above-mentioned electrical conduction test method, which will not be repeated here.

[0056] In order to effectively prevent the inner pattern of the quasi-non-metallized hole segment from interfering with the test results, windows are respectively made between the hole wall of the quasi-non-metallized hole segment and each inner pattern at the corresponding depth position.

[0057] In order to reduce the difficulty of plugging the hole, the plugging end of the plating resist 1 is beveled; the outer diameter of the plating resist 1 is 0.10mm-0.25mm larger than the single-side diameter of the through hole 3.

[0058] In summary, the manufacturing process for partial metallization of the through hole provided in the embodiment of the present invention only needs to set the second conductive layer 6 at the junction of the intended non-metallized hole section and the intended metallized hole section of the through hole 3 according to the partial metallization requirements, and then insert the plating resist 1 with the first conductive layer 5 coated on the outer wall into the through hole 3, and control the plugging depth based on the test circuit constructed by the first conductive layer 5 and the second conductive layer 6, and then perform copper electroplating on the through hole 3 inserted with the plating resist 1 to obtain a partially metallized through hole 3. Compared with the prior art method, the problem of residual stub being unable to be completely removed can be eliminated, thereby avoiding the interference of residual stub on the signal; and the plating resist 1 can be inserted into any depth position according to requirements to achieve any different partial metallization requirements, and has strong versatility.

[0059] The embodiment of the present invention further provides a PCB, including a through hole 3, wherein the through hole 3 is made according to the above-mentioned manufacturing process of partially metallizing the through hole 3. Specifically, the PCB can be a soft board, a hard board, or a hard-soft board, and as long as it has a through hole 3 that needs to be partially metallized, the solution provided by the present invention can be applied.

[0060] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for partially metallizing a through hole, characterized in that: Includes steps: Provide metal detection needles, hollow resists and printed circuit boards with through holes, and build test circuits; Wherein, the through hole includes adjacent to each other along its axial direction a pseudo non-metallized hole segment and a pseudo metallized hole segment, and the junction position between the pseudo non-metallized hole segment and the pseudo metallized hole segment is the target plugging depth position; The plating resist is used to be inserted into the through hole and fit with the hole wall of the through hole to be non-metallized hole section, but not fit with the hole wall of the through hole to be metallized hole section, so as to prevent copper plating / electroplating solution from contacting the hole wall of the through hole to be non-metallized hole section; The outer side wall of the plating resist is coated with a first conductive layer, the hole wall of the through hole is provided with a second conductive layer at a target plugging hole depth position, the second conductive layer is fixedly electrically connected to a metal detection needle through an inner layer pattern, and the metal detection needle is fixedly electrically connected to the first conductive layer of the plating resist, so that the first conductive layer, the second conductive layer, the metal detection needle, and the first conductive layer form the test circuit; Taking the hole opening of the proposed non-metallized hole section far away from the target plugging hole depth position as the entrance end, inserting the plating resist into the through hole, monitoring the electrical connection state of the test circuit in real time during the insertion process, and stopping inserting the plating resist when the electrical connection state switches from a disconnected state to a conductive state; After the insertion of the plating resist is stopped, copper electroplating is performed on the through hole to form an electroplating layer on the hole wall of the to-be-metallized hole section of the through hole.

2. The manufacturing process for partially metallizing a through hole according to claim 1, characterized in that: The printed circuit board is also provided with a metallized test hole, the metallized test hole is electrically connected to the inner layer pattern, and the metal detection needle is partially inserted into the metallized test hole.

3. The manufacturing process for partially metallizing a through hole according to claim 1, characterized in that: The plating resistance member includes a hollow support tube and a rubber layer, and the rubber layer wraps the entire outer side wall of the hollow support tube.

4. The manufacturing process for partially metallizing a through hole according to claim 3, characterized in that: The hollow support tube is made of high crystalline polypropylene (HCPP).

5. The manufacturing process for partially metallizing a through hole according to claim 3, characterized in that: The through hole is divided into two hole segments along its axial direction, consisting of the pseudo-non-metallized hole segment and the pseudo-metallized hole segment; the length of the plating resist is not less than the depth of the pseudo-non-metallized hole segment.

6. The manufacturing process for partially metallizing a through hole according to claim 3, characterized in that: The through hole is divided into at least three hole segments along its axial direction, which are composed of the pseudo-non-metallized hole segments and the pseudo-metallized hole segments cross-distributed; The number of the plating resists is the same as the number of the to-be-non-metallized hole segments and corresponds one to one, and the length of each plating resist is equal to the depth of the corresponding to-be-non-metallized hole segment; When the number of the plating resists is at least two, each of the plating resists is provided with a corresponding target plugging hole depth position, and each target plugging hole depth position is formed with a corresponding test circuit; when each plating resist is plugged into the through hole respectively, the plugging hole depth of each plating resist is controlled by the corresponding test circuit.

7. The manufacturing process for partially metallizing a through hole according to claim 1, characterized in that: Windows are respectively made between the hole wall of the quasi-non-metallized hole section and each inner layer pattern at a corresponding depth position.

8. The manufacturing process for partially metallizing a through hole according to claim 1, characterized in that: The plug hole end of the plating resistance member is an oblique cut.

9. The manufacturing process for partially metallizing a through hole according to claim 1, characterized in that: The outer diameter of the plating resist is 0.10 mm to 0.25 mm larger than the diameter of the through hole on one side.

10. A PCB comprising a through hole, characterized in that: The through hole is made according to the manufacturing process of partially metallizing the through hole according to any one of claims 1 to 8.

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