circuit board

Abstract

A circuit board according to the present disclosure has a unique structure that allows the presence or absence of a protective film on the board to be verified. Typically, the circuit board according to the present disclosure comprises a circuit board, an electronic circuit, an inspection section, and a protective film. The electronic circuit is mounted on the circuit board. The inspection section is mounted on the circuit board in such a way that it is electrically separated from the electronic circuit. The inspection section includes a plurality of conductive pads and a connecting line for electrically connecting the conductive pads to each other. The protective film covers the inspection section together with the electronic circuit.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a circuit board having a function of checking the presence or absence of a protective film. BACKGROUND OF THE TECHNOLOGY

[0002] With the advancement of communication technology, sensor technology, and control technology, circuit boards, in which electronic components are mounted on printed circuit boards, have become indispensable components today. Circuit boards are required to have various properties that depend on the environment in which the boards are used. For example, a circuit board used in a cutting machine must be resistant to cutting fluids. One technique for improving the cutting fluid resistance of circuit boards is the so-called parylene coating, in which para-xylylene is applied to the board by vapor deposition. The parylene film formed by the parylene coating has excellent cutting fluid resistance, but is colorless and transparent, making its presence difficult to detect.In order to detect the presence or absence of a colorless, transparent parylene coating film, there is a known technology to impart fluorescent properties to the parylene coating film (Patent Literature 1). CITATION LISTPATENT LITERATURE

[0003] Patent Literature 1: Unexamined Japanese Patent Application Publication No. 4-283223 SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0004] However, making the parylene coating fluorescent requires the installation of a plasma generator or similar equipment, which increases the cost of the equipment. Therefore, it is desirable to propose a technology that can easily determine whether a circuit board has a protective film, such as a colorless, transparent parylene coating film, or not. SOLUTION TO THE PROBLEM

[0005] A circuit board according to the present disclosure comprises: a circuit board; an electronic circuit mounted on the circuit board; an inspection portion mounted to be electrically separated from the electronic circuit and including a plurality of conductive pads and a lead wire electrically connecting the conductive pads; and an insulating protective film covering the inspection portion together with the electronic circuit. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing an example of a circuit board according to the present embodiment. Fig. 2 is a plan view of the circuit board in Fig. 1. Fig. 3 is a sectioned end view along AA' in Fig. 2 Fig. 4 is a supplementary diagram for explaining a method of inspecting the presence or absence of a coating of a circuit board according to the present embodiment. Fig. 5 is a plan view showing a first modification of the circuit board according to the present embodiment. Fig. 6 is a plan view showing a second modification of the circuit board according to the present embodiment. Fig. 7 is a plan view showing a third modification of the circuit board according to the present embodiment. Fig. 8 is a plan view showing a fourth modification of the circuit board according to the present embodiment. Fig. 9 is a perspective view showing a fifth modification of the circuit board according to the present embodiment. Fig. 10 is a sectioned end view along BB' in Fig. 9 DETAILED DESCRIPTION OF THE INVENTION

[0006] A circuit board according to the present embodiment will be described below with reference to the drawings. In the following description, components having substantially the same function and configuration are denoted by the same reference numerals, and repetitive descriptions will be made only where necessary.

[0007] A feature of the circuit board according to the present embodiment is that it has a structure that enables the presence or absence of a protective film of the circuit board to be checked. Typically, this structure is used in the manufacture of circuit boards to check whether a coating has been applied to the board. It enables checking for the presence or absence of a colorless, transparent parylene coating film, which is difficult for workers to confirm visually or difficult to extract by image processing based on a camera image. Typically, the circuit board according to the present embodiment is configured as follows.

[0008] In the present embodiment, the terms are defined as follows.

[0009] Circuit board: A plate-shaped element made of an insulating material. In the present embodiment, the insulating material can be a rigid material or a flexible material.

[0010] Printed circuit board: A circuit board with a conductive pattern printed on its front, back, inside, etc., that constitutes at least part of an electronic circuit.

[0011] Printed circuit board: A printed circuit board onto which circuit elements (electronic components) are soldered and which can be operated as an electronic circuit.

[0012] Printed circuit board: A coated printed circuit board. In other words, a printed circuit board that is completely covered with a parylene coating (protective film).

[0013] Electronic circuit: A circuit mounted on a circuit board to realize the original function of the circuit board according to the present embodiment.

[0014] Inspection section: A structure mounted on a printed circuit board for checking whether a printed circuit board is covered with a parylene protective layer. The inspection section is a structure provided only on the circuit board according to the present embodiment and is not directly related to the realization of the original function of the circuit board according to the present embodiment.

[0015] Note that the printed circuit board in the present embodiment is described as a so-called single-sided board consisting of two layers, an insulating layer and a conductive layer, in which a conductive pattern can be formed only on the front surface of the board, and in which an electronic circuit and an inspection section are mounted on the front surface of the board. However, the printed circuit board may also be a double-sided board consisting of three layers: conductive layer, insulating layer, and conductive layer, or a multi-layer board with at least three or more conductive layers. Alternatively, the electronic circuit and the inspection section may be mounted on both surfaces of the board.

[0016] The configuration of the circuit board according to the present embodiment will be described below with reference to Fig. 1 to Fig. 3 described. Fig. 1 is a perspective view showing an example of a circuit board according to the present embodiment. Fig. 2 is a plan view of the circuit board in Fig. 1. Fig. 3 is a sectioned end view along AA' in Fig. 2

[0017] As in Fig. 1, Fig. 2 and Fig. As shown in Fig. 3, a printed circuit board 1 according to the present embodiment includes an insulating board 20, an electronic circuit 30 mounted on a front surface of the board 20, an inspection portion 40 mounted on the front surface of the board 20, and an insulating protective film 10 covering the inspection portion 40 together with the electronic circuit 30. The board 20, the electronic circuit 30, and the inspection portion 40 mounted on the front surface of the board 20 are collectively referred to as a printed circuit board.

[0018] The insulating protective film 10 covers the entire surface (front, back, and side) of the printed circuit board. Typically, the insulating protective film 10 is realized by a colorless and transparent parylene coating film 10, which also exhibits cutting fluid resistance. The parylene protective film 10 is formed by depositing para-xylylene on the printed circuit board. However, the insulating protective film 10 is not limited to a parylene coating film and can be, for example, another type of protective film with high visible light transparency, such as a parylene coating film, or a type of protective film with low visible light transparency, which can be visually confirmed.

[0019] The electronic circuit 30 includes circuit elements 31 and a conductive connecting line 33 for electrically connecting the circuit elements 31 to one another. The circuit elements 31 include, for example, an integrated circuit, a sensor, a resistor, an inductor, a capacitor, and the like. Typically, the connecting line 33 is implemented by a conductor pattern formed on the front side of the circuit board 20. The connecting line 33 may comprise a through-hole formed in the circuit board 20 or be implemented by an independent conductive element, such as a lead wire.

[0020] The inspection section 40 is used to check the presence or absence of the parylene coating 10. It consists of two conductive pads 41 and a conductive connecting line 43 for connecting the two pads 41. Typically, the two pads 41 have a circular shape and are implemented by independent conductive elements. The connecting line 43 is a single straight line and is implemented by a conductor pattern on the front side of the circuit board 20. That is, the inspection section 40 is implemented by soldering two pads 41 at both ends of a linear conductor pattern as a connecting line 43 on the front side of the circuit board 20.

[0021] The inspection section 40 is mounted such that it is electrically separated from the electronic circuit 30. Electrically separated means that at least the structures are not in physical contact with each other. Of course, the term "electrically separated" can also encompass a state in which the structures do not exert any electrical influence, such as electromagnetic coupling or capacitive coupling, on each other. For example, the inspection section 40 is mounted on the circuit board 20 such that the two pads 41 and the connecting line 43 forming the inspection section 40 are not in physical contact with the connecting line 33 forming the electronic circuit 30. Preferably, the inspection section 40 is mounted in an area on the front side of the circuit board 20 where the mounting density of the circuit elements 31 and the connecting line 33 forming the electronic circuit 30 is low.

[0022] As in Fig. 3, it is desirable that the two pads 41 be thicker than the connecting line 43. Accordingly, a step can be formed between the connecting line 43 and the pads 41, and the contact area of ​​the parylene coating film 10 with the printed circuit board can be increased compared to the case where the pads 41 have the same thickness as the connecting line 43. As described later, increasing the contact area of ​​the parylene coating film 10 with the printed circuit board contributes to improving the adhesion of the parylene coating film 10 to the printed circuit board.

[0023] A method for checking the presence or absence of the parylene coating 10 of the circuit board 1 according to the present embodiment will be described below with reference to Fig. 4 described. Fig. Figure 4 is a supplementary diagram for explaining the method for checking the presence or absence of the parylene coating 10 of the circuit board 1 according to the present embodiment. The presence or absence of the parylene coating 10 of the circuit board 1 according to the present embodiment can be checked using a continuity tester 100. The continuity tester 100 is a two-probe device capable of judging the conduction / non-conduction state between two points to which the two probes are respectively applied.

[0024] As in Fig. As shown in Figure 4, the two probes of the continuity tester 100 are brought into contact with positions corresponding to the two pads 41 of the inspection section 40 to check the presence or absence of the parylene coating 10 of the circuit board 1 according to the present embodiment. When the two pads 41 are covered with the parylene coating film 10, the two probes are not electrically connected to the two pads 41, and the state between the two probes is non-conductive because the parylene coating film 10 is insulating. When the two pads 41 are not covered with the parylene coating film 10, the two probes come into direct contact with the two pads 41, so the state between the two probes is conductive via the inspection section 40.

[0025] Note that the parylene coating film 10 of the printed circuit board 1 according to the present embodiment is formed by vapor deposition. With vapor deposition, the entire printed circuit board placed in a vapor deposition chamber can be evenly coated, so that it never happens that only a part of the printed circuit board is covered with the parylene coating film 10. In other words, the fact that the two pads 41 are covered with the parylene coating film 10 means that the entire printed circuit board is covered with the parylene coating film 10. Likewise, the fact that the two pads 41 are not covered with the parylene coating film 10 means that the entire printed circuit board is not covered with the parylene coating film 10.

[0026] Therefore, the presence or absence of the parylene coating film 10 of the printed circuit board 1, in other words, whether the printed circuit board has been vapor-deposited or not, can be checked based on the result of determining the conductive / non-conductive state between the two probes when the two probes of the continuity tester 100 are brought into contact with the positions corresponding to the two pads 41 of the inspection section 40, respectively.

[0027] Since the circuit board 1 according to the present embodiment has the inspection section 40, the presence or absence of the parylene coating 10 of the circuit board 1, in other words, whether the printed circuit board has been vapor-deposited or not, can be easily checked by bringing the two probes of the continuity tester 100 into contact with the positions of the two pads 41 of the inspection section 40. The fact that the circuit board 1 has a structure capable of checking whether or not a coating has been applied to it contributes to improving the reliability of the circuit board 1.

[0028] On the circuit board 20 on which the structure of the inspection section 40 is mounted, there is also an electronic circuit 30 for realizing the original function of the circuit board 1. However, since the inspection section 40 is mounted at a position electrically separate from the electronic circuit 30, the mounting of the inspection section 40 does not hinder the original function of the electronic circuit 30. Even if the surface of the parylene coating film 10 is scratched by the probes coming into contact with the positions of the pads 41 of the inspection section 40 and the cutting fluid penetrates through the scratch, the cutting fluid can be prevented from reaching the electronic circuit 30, or the time until the cutting fluid reaches the electronic circuit 30 can be delayed, thereby preventing the electronic circuit 30 from developing corrosion.

[0029] By mounting not only the electronic circuit 30 for realizing the original function of the circuit board 1, but also the inspection section 40 on the circuit board 20, the unevenness of the front surface of the printed circuit board is increased, so that the contact area where the parylene coating film 10 comes into contact with the printed circuit board is enlarged, and the adhesion of the parylene coating film 10 to the printed circuit board can be improved. Peeling of the parylene coating film 10 tends to occur on a flat surface with a small contact area, and once peeling occurs, the peeling may spread to an uneven area with a large contact area. The inspection section 40 is mounted in an area where the mounting density of the circuit elements 31 and the connecting line 33 constituting the electronic circuit 30 on the front surface of the circuit board 20 is low, that is,on a flat surface where the contact area with the parylene coating film 10 is small. Therefore, the flat surface of the printed circuit board on which the parylene coating film 10 is likely to peel off can be reduced, and the possibility of the parylene coating film 10 peeling off the circuit board 1 can be appropriately reduced.

[0030] The inspection section 40 can be formed by soldering two conductive pads 41 to a conductor pattern as a connecting line 43 provided on the front side of the circuit board 20. The conductor pattern constituting the inspection section 40 can be manufactured by the same method as the conductor pattern constituting the electronic circuit 30. Furthermore, the process of soldering the two pads 41 to the conductor pattern constituting the inspection section 40 can be easily added to the process of soldering the electronic components constituting the electronic circuit 30 to the conductor pattern constituting the electronic circuit 30. Therefore, it is possible to avoid a cost increase due to the additional mounting of the inspection section 40 on the circuit board 20.

[0031] To test the presence or absence of the parylene coating 10, the two test probes of the continuity tester 100 can be brought into contact with the two contact pads 41 provided at predetermined positions on the circuit board 1, respectively. Therefore, the test can be performed by a robot or the like, so that the process of testing the presence or absence of the parylene coating 10 can be easily integrated into the manufacturing process of the circuit board 1. Furthermore, only one continuity tester 100 is required to test the presence or absence of the parylene coating 10, which reduces installation costs compared to using a plasma generator.Since the coating film itself to be inspected does not need to be identified, the present embodiment can also be used for inspecting the presence or absence of the colorless and transparent parylene coating film 10, which is difficult to be visually confirmed by workers or extracted by image processing based on a camera image.

[0032] In the circuit board 1 according to the present embodiment, the connecting line 43 of the inspection portion 40 has a linear shape. However, the shape of the inspection portion is not limited to this. A modification of the inspection portion will be described with reference to Fig. 5, Fig. 6, Fig. 7 and Fig. 8 described.

[0033] As in Fig. As shown in FIG. 5, a connecting line 53 constituting an inspection portion 50 of a circuit board 2 according to a first modification has a zigzag shape in which the connecting line 53 is alternately folded many times in opposite directions, and conductive pads 51 are connected to both ends of the connecting line 53. This shape is also called a waveform with rectangular peaks and valleys.

[0034] As in Fig. 6, a connecting line 63 of an inspection section 60 of a printed circuit board 3 according to a second modification is configured to have a circumferential shape along the outer circumference of the board 20. Conductive pads 61 are connected to both ends of the connecting line 63. The circumferential shape along the outer circumference of the board 20 is not limited to the entire shape of the outer circumference of the board 20, but also includes the shape of a part of the outer circumference of the board 20. As described above, the inspection section enables the presence or absence of the parylene coating film 10 to be checked and also contributes to improving the adhesion of the parylene coating film 10 to the printed circuit board. As shown in Fig. 5 and Fig. 6, the adhesion of the parylene coating film 10 to the printed circuit board can be further improved by increasing the length of the connecting line 53, 63 of the inspection portion 50, 60 to increase the contact area of ​​the parylene coating film 10 with the printed circuit board.

[0035] As in Fig. As shown in FIG. 7, a connecting line 73 constituting an inspection portion 70 of a printed circuit board 4 according to a third modification has a shape surrounding the important circuit element 35 of the electronic circuit 30. Conductive pads 71 ​​are connected to both ends of the connecting line 73, respectively. The conductive pads 71 ​​are disposed on opposite sides of the important circuit element 35. The important circuit element 35 is, for example, an encoder circuit, an angle calculation circuit, and the like. The connecting line 73 has a spiral shape, and the inspection portion 70 is disposed at a position where the important circuit element 35 is located at the center of the spiral. As described above, the adhesion of the parylene coating film to the printed circuit board can be enhanced at the mounting position of the inspection portion and the surrounding region.By taking advantage of this and attaching the inspection portion 70 to surround the important circuit element 35 of the electronic circuit 30, the adhesion of the parylene coating film 10 to the mounting position of the important circuit element 35 can be improved and the possibility of corrosion of the important circuit element 35 due to peeling of the parylene coating film 10 can be reduced.

[0036] As in Fig. As shown in Fig. 8, another conductive pad 81c is mounted together with the conductive pads 81a and 81b on a circuit board 5 according to a fourth modification. A branch line 84 branches off from the connecting line 83 connecting the pads 81a and 81b at any branching point 83a and connects the other pad 81c to the pads 81a and 81b. By allowing the connecting line 83 to be branched in this way, the degree of freedom in mounting the connecting line 83 is improved, and the connecting line can be mounted in a narrow area where the connecting line cannot be folded.

[0037] In the circuit board 1 according to the present embodiment, the inspection section 40 is configured by soldering two conductive pads 41 to a conductor pattern formed on the front surface of the board 20 as a connecting line 43. However, the configuration of the inspection section is not limited to this.

[0038] As in Fig. 9 and Fig.As shown in FIG. 10, in an inspection section 90 of a circuit board 6 according to a fifth modification, two pads 91 and a connecting line 93 connecting the two pads 91 are integrally formed by the conductor pattern on the front surface of the board 20. In this way, it is not necessary to manufacture two pads 41 that are independent elements, and the inspection section 90 can be formed by the same process as the conductor pattern constituting the electronic circuit 30, so that the cost of additionally mounting the inspection section 90 on the board 20 can be further reduced.

[0039] Although not shown, the two pads 41 constituting the inspection portion 40 may be formed by a conductor pattern, and the connecting line 43 connecting the two pads 41 may be realized by an independent member such as a lead wire.

[0040] In the present embodiment, the parylene coating film 10 of the printed circuit board 1 is formed by vapor deposition; therefore, when the two pads 41 constituting the inspection section 40 of the printed circuit board 1 are covered with the parylene coating film, the entire printed circuit board can be considered to be covered with the parylene coating film, and when the two pads 41 are not covered with the parylene coating film, the entire printed circuit board can be considered to be uncoated with the parylene coating film. However, the method for coating the printed circuit board is not limited to vapor deposition, and it is possible to coat only a part of the printed circuit board. The present embodiment can also be applied to inspecting the presence or absence of a protective film partially covering the printed circuit board.In this case, the inspection section can be installed in an area covered with the protective film of the printed circuit board, and the electronic circuit does not necessarily have to be installed in this area.

[0041] In the present embodiment, a printed circuit board in which the electronic circuit 30 and the inspection section 40 are mounted on the insulating board 20 is defined as the printed circuit board, and a printed circuit board covered with the parylene protective film 10 with cutting fluid resistance is defined as the circuit board 1. However, the printed circuit board may also include other protective films that can be applied to conventional rigid or flexible boards, such as solder mask to prevent solder from adhering to unwanted parts and to protect the circuit pattern from dust, heat, moisture, and the like.

[0042] In the present embodiment, the inspection section 40 has two pads 41. However, the inspection section 40 may be configured to have three or more pads 41. For example, one inspection section may consist of three conductive pads and a conductive connection line connecting the three pads. The presence or absence of the parylene coating film 10 can be inspected by a continuity tester according to three combinations of two of the three pads. Since the inspection is performed three times, the accuracy of the inspection can naturally be improved. From a similar perspective, the circuit board 1 may have a plurality of inspection sections 40.

[0043] In the present embodiment, the inspection section is described as being disposed only on the front side of the board, but it may be disposed on both sides of the board. In this case, a first inspection section may be disposed on the front side of the board, and a second inspection section may be disposed on the back side of the board. Of course, a configuration may also be adopted in which the lead wires constituting the inspection section are disposed on the front and back sides of the board, electrically connected through a through-hole, and a plurality of pads constituting the inspection section are disposed on one surface or both surfaces of the board.By attaching the inspection section on both surfaces of the board, the presence or absence of the protective film on both surfaces of the circuit board can be inspected and the possibility of peeling off the protective film on both surfaces can be reduced.

[0044] The following appendices further disclose the present embodiment and modifications. (Appendix 1)

[0045] A circuit board 1 comprising: a circuit board 20; an electronic circuit 30 mounted on the circuit board 20; an inspection portion 40 mounted to be electrically separated from the electronic circuit 30 and including a plurality of conductive pads 41 and a connecting line 43 electrically connecting the conductive pads 41; and an insulating protective film 10 covering the inspection portion 40 together with the electronic circuit 30. (Appendix 2)

[0046] The connecting line 43 of Annex 1 is a single straight line. (Appendix 3)

[0047] The inspection section 40 of Annex 1 further includes another conductive pad 81c mounted on the circuit board 20 and a branch line 84 branching from the connecting line 83 to connect the another conductive pad 81c to the conductive pads 81a and 81b. (Appendix 4)

[0048] The connecting line 43 of Annex 1 has a zigzag shape in which the connecting line 43 is alternately folded in opposite directions. (Appendix 5)

[0049] The connecting line 43 of Annex 1 has a shape that surrounds a circuit element of the electronic circuit 30. (Appendix 6)

[0050] The connecting line 43 of Annex 1 has a circumferential shape along a circumference of the circuit board 20.

[0051] Although the embodiments of the present disclosure have been described in detail, the present disclosure is not limited to the individual embodiments described above. These embodiments may be subjected to various additions, substitutions, modifications, partial deletions, etc., without departing from the gist of the invention or the idea and spirit of the present invention as understood from the contents described in the claims and their equivalents. In the embodiments described above, for example, the order of operations and the order of processes are shown as examples, and the present invention is not limited thereto. The same applies to the case where numerical values ​​or formulas are used in the description of the embodiments described above. EXPLANATION OF REFERENCE NUMBERS

[0052] 1: Circuit board, 10: Parylene coating film (protective film), 20: Circuit board, 30: Electronic circuit, 31: Circuit element, 33: Connecting line, 40: Inspection section, 41: Pad, 43: Connecting line. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 4-283223

[0003]

Claims

[1] A circuit board comprising: a circuit board; an electronic circuit mounted on the circuit board; an inspection portion mounted to be electrically separated from the electronic circuit and comprising a plurality of conductive pads and a connecting line electrically connecting the conductive pads; and an insulating protective film covering the inspection section together with the electronic circuit. [2] The circuit board according to claim 1, wherein the connecting line is a single straight line. [3] The circuit board according to claim 1, wherein the inspection section further comprises: another conductive pad attached to the circuit board; and a branch line branching off from the connecting line to connect the further conductive pad to the conductive pads. [4] The circuit board according to claim 1, wherein the connecting line has a zigzag shape in which the connecting line is alternately folded in opposite directions. [5] The circuit board according to claim 1, wherein the connecting line has a shape that surrounds a circuit element of the electronic circuit. [6] The circuit board according to claim 1, wherein the connecting line has a circumferential shape along a circumference of the board.

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