A method for fabricating PCB signal holes

Abstract

This invention relates to the field of circuit board manufacturing technology, and discloses a method for processing PCB signal holes, comprising the following steps: processing to form a PCB having a plurality of signal holes; forming a plug hole structure with a preset plug hole depth in at least a portion of the signal holes; and etching the exposed copper plating inside the signal holes using an etching solution. The PCB signal hole processing method provided by this invention can replace the traditional mechanical back-drilling process, saving the space occupied by the signal holes on the PCB, thereby increasing the wiring density of the PCB.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing technology, and in particular to a method for processing PCB signal holes. Background Technology

[0002] With the development of wireless and network communication technologies, the requirements for signal transmission rates are constantly increasing. PCBs are an important component of signal transmission, and it is necessary to increase the wiring density of PCBs.

[0003] The stub length of signal vias on a PCB is one of the key specifications. The stub acts as a concave filter in the transmission line. When two such stubs appear in the signal transmission line, an oscillation segment will be formed. Whether it is filtering or oscillation, it will damage the high-speed signal transmission and cause signal distortion. Therefore, it is very important to control the stub height by back drilling.

[0004] Currently, the industry uses controlled-depth drilling with a drilling machine to remove residual copper from signal holes. However, controlled-depth drilling with a drilling machine requires increasing the diameter of the back drill bit (compared to the diameter of the first drill bit + 6-8 mil), which will have a significant impact on the PCB wiring space and is not conducive to improving the signal transmission rate.

[0005] Therefore, there is an urgent need for a PCB signal hole processing method to solve the above-mentioned technical problems. Summary of the Invention

[0006] Based on the above, the purpose of this invention is to provide a PCB signal hole processing method that replaces the traditional mechanical back drilling process, saves the space occupied by the signal hole on the PCB, and thus improves the wiring density of the PCB.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for fabricating PCB signal holes is provided, including the following steps:

[0009] The process involves fabricating a PCB with several signal holes.

[0010] A plugging structure with a preset plugging depth is formed in at least a portion of the signal holes;

[0011] The exposed copper plating inside the signal hole is etched using an etching solution.

[0012] As an optional technical solution for PCB signal hole processing, the plugging depth of the plugging structure is obtained by the following formula:

[0013] H+Q=LP, where H+Q is the hole-plugging depth of the hole-plugging structure, L is the thickness of the PCB, P is the preset etching depth, and Q is the etching compensation depth.

[0014] As an optional technical solution for PCB signal hole processing, the etching compensation depth Q ranges from 1 mil to 3 mil.

[0015] As an optional technical solution for PCB signal hole processing, before etching the exposed copper in the signal hole with etching solution, the following steps are also included:

[0016] Transfer the signal line pattern to the PCB.

[0017] As an optional technical solution for PCB signal hole processing, forming a plug structure with a predetermined depth in at least a portion of the signal holes specifically includes the following steps:

[0018] The PCB is placed in its initial position within the plug cylinder using a clamp;

[0019] Inject plugging medium into the plugging cylinder body so that the liquid level of the plugging medium reaches the reference level;

[0020] The PCB is lowered to a first depth or a first volume of the via-filling medium is injected, so that the PCB is immersed in the via-filling medium, and the immersion depth of the PCB is less than the thickness of the PCB.

[0021] The plugging medium in at least a portion of the signal hole is initially solidified to form a first plugging hole.

[0022] As an optional technical solution for PCB signal hole processing, when the PCB is placed in the initial position of the plug cylinder, the lower surface of the PCB is flush with the reference surface.

[0023] As an optional technical solution for PCB signal hole processing, the first depth is obtained by the following formula:

[0024] h1 = (N1*s*H1 + V1) / (S1 - S2 + N1*s), where h1 is the first depth, N1 is the number of all signal holes that need to be plugged, s is the cross-sectional area of ​​the signal hole, H1 is the plugging depth of the first plugged hole, V1 is the immersion volume of the fixture when descending to the first depth, S1 is the cross-sectional area of ​​the plugging cylinder, and S2 is the cross-sectional area of ​​the PCB.

[0025] As an optional technical solution for PCB signal hole processing, the first volume is obtained by the following formula:

[0026] v1 = N1 * s * H1 + S2 * H1, where N1 is the number of all signal holes that need to be plugged, s is the cross-sectional area of ​​the signal hole, H1 is the plugging depth of the first plugged hole, and S2 is the gap area between the PCB and the plugged cylinder.

[0027] As an optional technical solution for PCB signal hole processing, the signal holes are provided in at least two forms. The preliminary curing of the plugging medium in at least a portion of the signal holes specifically refers to the preliminary curing of the plugging medium in a portion of the signal holes. After the preliminary curing of the plugging medium in a portion of the signal holes, the following steps are also included:

[0028] The PCB continues to descend to a second depth or continues to inject a second volume of the plugging medium;

[0029] The plugging medium in at least one of the signal holes is initially solidified to form a second plugging hole.

[0030] As an optional technical solution for PCB signal hole processing, the second depth is obtained by the following formula:

[0031] h2=(N2*s*(H2-H1)+V2) / (S1-S2+N2*s), where h2 is the second depth, N2 is the number of all signal holes (2) that need to be plugged minus the number of signal holes plugged in the first time, s is the cross-sectional area of ​​the signal hole, H1 is the plugging depth of the first plugging hole, H2 is the plugging depth of the second plugging hole, V2 is the immersion volume of the fixture when descending to the second depth, S1 is the cross-sectional area of ​​the plugging cylinder, and S2 is the cross-sectional area of ​​the PCB.

[0032] As an optional technical solution for PCB signal hole processing, the second volume is obtained by the following formula:

[0033] v2 = N2 * s * (H2 - H1) + S2 * (H2 - H1), where N2 is the total number of signal holes that need to be plugged minus the number of signal holes plugged in the first plugging, s is the cross-sectional area of ​​the signal hole, H1 is the plugging depth of the first plugging hole, H2 is the plugging depth of the second plugging hole, and S2 is the gap area between the PCB and the plugging cylinder.

[0034] As an optional technical solution for PCB signal hole processing, the hole-filling medium includes photosensitive ink and thermosetting ink; or the hole-filling medium includes photosensitive resin and thermosetting resin.

[0035] As an optional technical solution for PCB signal hole processing, the preliminary solidification of at least a portion of the plugging medium in the signal hole to form the first plugging hole specifically includes the following steps:

[0036] Allow the plugging medium to remain still for a preset time, allowing it to immerse itself in the signal hole;

[0037] The plugging medium corresponding to the first plugging hole is exposed using ultraviolet light.

[0038] After the plugging medium in all the signal holes that need to be plugged has been initially cured, the following steps are also included:

[0039] The PCB is removed from the plug cylinder.

[0040] The plugging medium in the signal hole that requires thermosetting.

[0041] The beneficial effects of this invention are as follows:

[0042] The PCB signal hole processing method provided by this invention controls the plugging depth of the formed plugging structure in reverse according to the depth of the part of the signal hole wall that needs to be removed. Then, the excess copper exposed in the signal hole is etched by etching solution to remove excess stub, which replaces the traditional mechanical back drilling process and saves the space occupied by the signal hole on the PCB, so as to improve the wiring density of the PCB. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of the PCB structure before the vias are plugged, provided by the present invention;

[0045] Figure 2 This is a flowchart of the PCB signal hole processing method provided by the present invention;

[0046] Figure 3 This is a schematic diagram of the structure of forming the first plug hole, the second plug hole, and the third plug hole on the PCB provided by the present invention;

[0047] Figure 4 This is a flowchart of the steps for forming a plug structure with a preset plug depth provided by the present invention;

[0048] Figure 5This is a schematic diagram showing the state in which the liquid level of the plugging medium provided by the present invention reaches the reference plane;

[0049] Figure 6 This is a schematic diagram of the state of the PCB when it descends to the first depth, as provided by the present invention.

[0050] Figure 7 This is a flowchart of the steps provided by the present invention to initially solidify the plugging medium in at least a portion of the signal hole to form a first plugging hole;

[0051] Figure 8 This is a flowchart of the steps involved in forming a PCB with signal holes, as provided by the present invention.

[0052] In the picture:

[0053] 1. PCB; 2. Signal hole; 21. First plug hole; 22. Second plug hole; 23. Third plug hole; 3. Plug hole cylinder; 4. Plug hole medium; 5. Fixture; 6. Ultraviolet light sensor lamp; 7. Copper plating. Detailed Implementation

[0054] To make the technical problems solved by the present invention, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] This embodiment provides a method for processing PCB signal holes. Signal holes 2 are processed on PCB 1. By controlling the hole-filling depth and etching with a chemical solution, excess stubs (residual studs) in the signal holes 2 are removed. Signal holes 2 are then processed as follows: Figure 1 As shown, section B represents the exposed copper 7 on the hole wall after plugging, while section A represents the part requiring depth-controlled plugging. Figure 2 As shown, the PCB signal hole processing method specifically includes the following steps:

[0056] The PCB1 with several signal holes 2 is formed through processing;

[0057] A plugging structure with a preset plugging depth is formed in at least a portion of the signal holes 2;

[0058] The exposed copper 7 inside the signal hole 2 is etched using etching solution.

[0059] Specifically, the PCB signal hole processing method provided in this embodiment controls the plugging depth of the formed plugging structure in reverse according to the depth of the part of the signal hole where the copper 7 needs to be removed from the hole wall. Then, the excess copper 7 exposed in the signal hole 2 is etched by etching solution to remove the excess stub function, which replaces the traditional mechanical back drilling process and saves the space occupied by the signal hole on the PCB1, so as to improve the wiring density of the PCB1.

[0060] Preferred, such as Figure 3 As shown, the plug depth of the plug structure is obtained by the following formula:

[0061] H+Q=LP, where H+Q is the hole-plugging depth of the hole-plugging structure, L is the thickness of PCB1, P is the preset etching depth, and Q is the etching compensation depth.

[0062] Optionally, the etch compensation depth Q can range from 1 mil to 3 mil. In this embodiment, the etch compensation depth Q is 2 mil.

[0063] Furthermore, such as Figure 2 As shown, before etching the exposed copper 7 inside the signal hole 2 with etching solution, the following steps are also included:

[0064] Transfer the signal line pattern to PCB1.

[0065] While the exposed copper 7 inside the signal hole 2 is etched with etching solution, the etching solution also etches the copper 7 on other areas of the PCB1 board surface except for the signal line pattern. This allows the etching of the signal line pattern on the PCB1 and the etching of the excess copper 7 inside the signal hole 2 to be carried out simultaneously, reducing processing steps and improving production efficiency.

[0066] Preferred, such as Figure 4 As shown, forming a plug structure with a preset plug depth in at least a portion of the signal hole 2 specifically includes the following steps:

[0067] The PCB1 is placed in the initial position inside the plug cylinder 3 using the clamp 5;

[0068] like Figure 5 As shown, plugging medium 4 is injected into the plugging cylinder 3 so that the liquid level of plugging medium 4 reaches the reference surface.

[0069] like Figure 6 As shown, PCB1 descends to a first depth or continues to inject a first volume of via-filling medium 4, so that PCB1 is immersed in via-filling medium 4, and the immersion depth of PCB1 is less than the thickness of PCB1.

[0070] The plugging medium 4 in at least part of the signal hole 2 is initially solidified to form the first plugging hole 21.

[0071] Specifically, in the via-filling process, the PCB1 is first placed in the via-filling cylinder 3. After the via-filling medium 4 is injected into the via-filling cylinder 3, the height of the PCB1 in the via-filling cylinder 3 is controlled by the fixture 5, or the via-filling medium 4 is continued to be injected. Thus, the depth of the PCB1 immersed in the via-filling medium 4 is adjusted according to the required depth of the via. Then, according to the number requirement of the first via 21, the via-filling medium 4 in at least part of the signal holes 2 is initially solidified to obtain the first via 21 with a specific via depth. This can effectively solve the problem that the traditional via-filling process cannot accurately control the via depth, quickly obtain the first via 21 with a specific via depth, facilitate the Z-axis interconnection of multilayer PCB1, and at the same time eliminate the back drilling process, save production process, improve production efficiency, and reduce production cost.

[0072] Furthermore, the signal hole 2 is provided with at least two holes. The preliminary curing of the plugging medium 4 in at least a portion of the signal hole 2 specifically refers to the preliminary curing of the plugging medium 4 in a portion of the signal hole 2. After the preliminary curing of the plugging medium 4 in a portion of the signal hole 2, the following steps are also included:

[0073] PCB1 continues to descend to a second depth or continues to inject a second volume of plugging medium 4;

[0074] The plugging medium 4 in at least one signal hole 2 is initially solidified to form a second plugging hole 22.

[0075] It should be noted that the signal hole 2 that ultimately forms the second plug hole 22 here is the signal hole 2 that did not undergo preliminary curing to form the first plug hole 21. Through the above steps, several first plug holes 21 and second plug holes 22 are formed, and the depth of the second plug hole 22 is greater than that of the first plug hole 21. That is, plug holes of different depths are precisely formed on the PCB1, thereby improving the versatility and flexibility of the PCB1.

[0076] Furthermore, such as Figure 3 As shown, depending on the different via depths, the above steps can be repeated to continue lowering PCB1 to a third depth, a fourth depth, and so on. In the signal holes 2 that have not undergone the aforementioned preliminary curing to form vias, different via depths such as third vias 23 and fourth vias are also formed through preliminary curing. By controlling the PCB1 to gradually immerse itself in the via-filling medium 4 from shallow to deep, and through preliminary curing to sequentially form vias of varying depths—first vias 21, second vias 22, third vias 23, fourth vias, etc.—until all via depth requirements are met, this process is simple and reliable. By controlling the immersion depth of PCB1 and selectively pre-curing the via-filling medium 4 within the signal holes 2, vias of various depths can be formed.

[0077] Optional, such as Figure 5As shown, when PCB1 is placed in the initial position of the plugging cylinder 3, the lower surface of PCB1 is flush with the reference surface. After the plugging medium 4 is injected into the plugging cylinder 3, the lower surface of PCB1 is just in contact with the plugging medium 4 or at the critical point of being about to contact the plugging medium 4.

[0078] Based on this, and considering the required plugging volume = (cross-sectional area of ​​plugging cylinder 3 - gap area between PCB1 and plugging cylinder 3) * descent depth of PCB1, the first depth is obtained using the following formula:

[0079] h1=(N1*s*H1+V1) / (S1-S2+N1*s), where h1 is the first depth, N1 is the number of signal holes 2 that need to be plugged, s is the cross-sectional area of ​​signal hole 2, H1 is the plugging depth of the first plugging hole 21, V1 is the immersion volume of the fixture 5 when descending to the first depth, S1 is the cross-sectional area of ​​the plugging cylinder 3, and S2 is the cross-sectional area of ​​PCB1.

[0080] Similarly, based on the formula: the volume to be plugged = (cross-sectional area of ​​plugged cylinder 3 - gap area between PCB1 and plugged cylinder 3) * descent depth of PCB1, the second depth is obtained by the following formula:

[0081] h2=(N2*s*(H2-H1)+V2) / (S1-S2+N2*s), where h2 is the second depth, N2 is the number of signal holes 2 that need to be plugged minus the number of signal holes 2 plugged in the first time, s is the cross-sectional area of ​​signal hole 2, H1 is the plugging depth of the first plugging hole 21, H2 is the plugging depth of the second plugging hole 22, V2 is the immersion volume of the fixture 5 when descending to the second depth, S1 is the cross-sectional area of ​​the plugging cylinder 3, and S2 is the cross-sectional area of ​​PCB1.

[0082] When PCB1 is immersed in via-filling medium 4 by continuing to inject via-filling medium 4, the first volume is obtained by the following formula:

[0083] v1 = N1 * s * H1 + S2 * H1, where N1 is the number of signal holes 2 that need to be plugged, s is the cross-sectional area of ​​signal hole 2, H1 is the plugging depth of the first plugging hole 21, and S2 is the gap area between PCB1 and plugging cylinder 3.

[0084] Similarly, the second volume is obtained by the following formula:

[0085] v2=N2*s*(H2-H1)+S2*(H2-H1), where N2 is the number of signal holes 2 that need to be plugged minus the number of signal holes 2 plugged in the first time, s is the cross-sectional area of ​​signal hole 2, H1 is the plugging depth of the first plugging hole 21, H2 is the plugging depth of the second plugging hole 22, and S2 is the gap area between PCB1 and plugging cylinder 3.

[0086] Preferably, the pore-filling medium 4 is composed of a two-component medium, which includes a photosensitive ink and a thermosetting ink, or the pore-filling medium 4 includes a photosensitive resin and a thermosetting resin.

[0087] like Figure 6 and Figure 7 As shown, the initial curing is specifically photocuring, which initially cures at least a portion of the plugging medium 4 in the signal hole 2 to form the first plugging hole 21, and specifically includes the following steps:

[0088] Allow the plug medium 4 to stand for a preset time, allowing it to immerse into the signal hole 2;

[0089] The ultraviolet light emitted by the ultraviolet light lamp is used to expose the plug medium 4 corresponding to the first plug hole 21.

[0090] Similarly, the initial curing of the plugging medium 4 in the second plugging hole 22 is also achieved by static, ultraviolet light exposure.

[0091] Furthermore, after the initial curing of all the plugging medium 4 in the signal holes 2 that need to be plugged, the photocured plugging medium 4 needs to be further thermocured, specifically including the following steps:

[0092] Remove PCB1 from cylinder block 3;

[0093] Thermosetting requires the plugging medium 4 in the signal hole 2 to ensure complete curing of the plugging medium 4 and guarantee the reliability of the plugging.

[0094] Optionally, after the plugging medium 4 in all the signal holes 2 that need to be plugged has been initially cured, the following steps are also included:

[0095] Remove PCB1 from cylinder block 3;

[0096] By developing and cleaning the plugging medium 4 in the signal hole 2, the uncured plugging medium 4 in the signal hole 2 is removed so that the excess copper 7 in the signal hole 2 can be etched in the subsequent process.

[0097] It should be noted that the above-mentioned developing and cleaning steps are performed before the thermosetting step.

[0098] Preferred, such as Figure 8 As shown, the PCB1 with signal holes 2 is fabricated by the following steps:

[0099] At least two substrates are stacked and laminated to form a PCB1 with a multilayer board structure;

[0100] Drill signal hole 2 on PCB1;

[0101] A metallic conductive layer is formed on signal hole 2 by electroplating.

[0102] Preferably, the clamp 5 for gripping PCB1 can be a suction cup.

[0103] Preferably, when PCB1 is placed inside the plugging cylinder 3, the distance between the edge of PCB1 and the peripheral wall of the plugging cylinder 3 is 1cm to 2cm.

[0104] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A method for processing PCB signal holes, characterized in that, Includes the following steps: A PCB (1) with several signal holes (2) is formed by processing; A plugging structure with a preset plugging depth is formed in at least a portion of the signal hole (2); The exposed copper plating (7) inside the signal hole (2) is etched using an etching solution; The process of forming a plugging structure with a preset depth in at least a portion of the signal holes (2) specifically includes the following steps: placing the PCB (1) in the initial position inside the plugging cylinder (3) using a clamp (5), injecting plugging medium (4) into the plugging cylinder (3) to make the liquid level of the plugging medium (4) reach the reference plane, lowering the PCB (1) to a first depth or continuing to inject a first volume of the plugging medium (4) to immerse the PCB (1) in the plugging medium (4), wherein the immersion depth of the PCB (1) is less than the thickness of the PCB (1), and initially solidifying the plugging medium (4) in at least a portion of the signal holes (2) to form a first plugging hole (21); The signal hole (2) is provided with at least two. The preliminary curing of the plugging medium (4) in at least a portion of the signal hole (2) specifically refers to the preliminary curing of the plugging medium (4) in a portion of the signal hole (2). After the preliminary curing of the plugging medium (4) in a portion of the signal hole (2), the following steps are also included: the PCB (1) continues to descend to a second depth or continues to inject a second volume of the plugging medium (4) to preliminarily cure at least one plugging medium (4) in the signal hole (2) to form a second plugging hole (22).

2. The PCB signal hole processing method according to claim 1, characterized in that, The plug depth of the plug structure is obtained by the following formula: H+Q=LP, where H+Q is the hole-plugging depth of the hole-plugging structure, L is the thickness of the PCB (1), P is the preset etching depth, and Q is the etching compensation depth.

3. The PCB signal hole processing method according to claim 2, characterized in that, The etching compensation depth Q ranges from 1 mil to 3 mil.

4. The PCB signal hole processing method according to claim 1, characterized in that, Before etching the exposed copper plating (7) inside the signal hole (2) with etching solution, the following steps are also included: Transfer the signal line pattern to the PCB (1).

5. The PCB signal hole processing method according to claim 1, characterized in that, When the PCB (1) is placed in the initial position of the plug cylinder (3), the lower surface of the PCB (1) is flush with the reference surface.

6. The PCB signal hole processing method according to claim 5, characterized in that, The first depth is obtained by the following formula: h1=(N1*s*H1+V1) / (S1-S2+N1*s), where h1 is the first depth, N1 is the number of all signal holes (2) that need to be plugged, s is the cross-sectional area of ​​the signal hole (2), H1 is the plugging depth of the first plugging hole (21), V1 is the immersion volume of the fixture (5) when descending to the first depth, S1 is the cross-sectional area of ​​the plugging cylinder (3), and S2 is the cross-sectional area of ​​the PCB (1).

7. The PCB signal hole processing method according to claim 5, characterized in that, The first volume is obtained by the following formula: v1 = N1 * s * H1 + S2 * H1, where N1 is the number of all signal holes (2) that need to be plugged, s is the cross-sectional area of ​​the signal hole (2), H1 is the plugging depth of the first plugging hole (21), and S2 is the gap area between the PCB (1) and the plugging cylinder (3).

8. The PCB signal hole processing method according to claim 1, characterized in that, The second depth is obtained by the following formula: h2=(N2*s*(H2-H1)+V2) / (S1-S2+N2*s), where h2 is the second depth, N2 is the number of all signal holes (2) that need to be plugged minus the number of signal holes (2) plugged in the first time, s is the cross-sectional area of ​​the signal hole (2), H1 is the plugging depth of the first plugging hole (21), H2 is the plugging depth of the second plugging hole (22), V2 is the immersion volume of the fixture (5) when descending to the second depth, S1 is the cross-sectional area of ​​the plugging cylinder (3), and S2 is the cross-sectional area of ​​the PCB (1).

9. The PCB signal hole processing method according to claim 1, characterized in that, The second volume is obtained by the following formula: v2=N2*s*(H2-H1)+S2*(H2-H1), where N2 is the number of all signal holes (2) that need to be plugged minus the number of signal holes (2) plugged for the first time, s is the cross-sectional area of ​​the signal hole (2), H1 is the plugging depth of the first plugging hole (21), H2 is the plugging depth of the second plugging hole (22), and S2 is the gap area between the PCB (1) and the plugging cylinder (3).

10. The PCB signal hole processing method according to claim 1, characterized in that, The plugging medium (4) includes photosensitive ink and thermosetting ink; or the plugging medium (4) includes photosensitive resin and thermosetting resin.

11. The PCB signal hole processing method according to claim 10, characterized in that, The preliminary curing of at least a portion of the plugging medium (4) in the signal hole (2) to form the first plug hole (21) specifically includes the following steps: The medium (4) is allowed to stand for a preset time to immerse itself in the signal hole (2); The plugging medium (4) corresponding to the first plugging hole (21) is exposed to ultraviolet light; after the plugging medium (4) in all the signal holes (2) that need to be plugged is initially cured, the following steps are also included: The PCB (1) is removed from the plug cylinder (3); The plugging medium (4) in the signal hole (2) that requires thermosetting.

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