JP2011159667A - Method of manufacturing printed wiring board, and printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed wiring board that has a jumper circuit prevented from becoming scratchy or peeling, and secures sufficient contact area between a connection portion exposed from an opening and the jumper circuit. <P>SOLUTION: The present invention relates to: the method of manufacturing the printed wiring board including the processes of forming a conductive circuit layer 20 including a plurality of connection portions 21 on one principal surface of an insulating base 10, forming an insulating protective layer 30 having openings 31 of ≥0.2 mm in diameter at positions corresponding to the connection portions 21 on one principal surface of the conductive circuit layer 20, printing conductive paste on one principal surface of the insulating protective layer 30 so that the jumper circuit 40 for connecting the connection portions 21 is 5 to 35 μm thick, and forming a cover coat layer 50 covering the jumper circuit 40; and the printed wiring board obtained by the manufacturing method. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a printed wiring board on which a jumper circuit is printed and formed with a conductive paste, and a printed wiring board.

  A jumper circuit for connecting a connection portion of a wiring pattern formed on one main surface of a base base material and exposed from an opening of a coverlay laminated on the base base material, with respect to a key sheet module including a contact spring (metal dome). What was formed by printing is known (patent document 1).

Japanese Patent Application No. 2007-59184

  By the way, when screen-printing with a conductive paste a jumper circuit that connects the connection part exposed from the opening of the insulating protective layer, one main surface (surface) of the insulating protective layer to be a printing surface is formed in the lower layer. It is not flat because it is affected by uneven wiring. In order to prevent the jumper circuit formed by screen printing on the surface of the insulating protective layer from fading, it is necessary to print the jumper circuit sufficiently thick. On the other hand, the jumper circuit is thick. If the thickness is too large, peeling easily occurs, and the thickness of the jumper circuit needs to be appropriately controlled.

  In addition, when screen-printing a jumper circuit with a controlled thickness, if the opening of the insulating protective layer is too small, the conductive paste does not sufficiently enter the opening and the connection and the jumper exposed from the opening are exposed. Since there is an inconvenience that a sufficient contact area with the contact portion of the circuit cannot be secured, it is necessary to appropriately manage the size of the opening according to the thickness of the jumper circuit.

  SUMMARY OF THE INVENTION Problems to be solved by the present invention include a printed wiring board manufacturing method and printed wiring in which the jumper circuit is prevented from fading and peeling, and the contact area between the connection portion exposed from the opening and the jumper circuit is sufficiently secured It is to provide a substrate.

  The present invention includes a step of forming a conductive circuit layer including a plurality of connecting portions on one main surface of an insulating substrate, and an insulating protective layer having an opening having a diameter of 0.2 mm or more at a position corresponding to the connecting portion. On the one main surface of the conductive circuit layer, and the conductive paste so that the thickness of the jumper circuit connecting the connecting portion to the one main surface of the insulating protective layer is 5 μm or more and 35 μm or less. The above-mentioned problems are solved by providing a method for manufacturing a printed wiring board and a printed wiring board, each of which includes a step of printing a cover coat layer that covers the jumper circuit.

In the above invention, the insulating protective layer having a thickness of 27.5 μm or more and 60 μm or less can be used.

In the above-mentioned invention, the conductive paste containing silver particles and having a viscosity of 250 ± 50 dPa · sec can be used.

In the above invention, the cover coat layer having a thickness of 35 μm or less can be used.

In the above invention, a polyurethane resin or a polyimide resin can be used as the cover coat layer.

The present invention according to a different aspect is formed on one main surface of an insulating base material, a conductive circuit layer including a plurality of connection portions formed on one main surface of the insulating base material, and the conductive circuit layer. An insulating protective layer having an opening at a position corresponding to the connecting portion; and a jumper circuit for connecting the connecting portion, which is printed using a conductive paste on one main surface of the insulating protective layer;
Providing a printed wiring board having a cover coat layer covering the jumper circuit, a diameter of the opening of 0.2 mm or more, and a thickness of the jumper circuit of 5 μm or more and 35 μm or less. Solve the above problems.

  In the above invention, the insulating protective layer may be configured to have a thickness of 27.5 μm or more and 60 μm or less.

  In the above invention, the conductive paste may be configured to contain silver particles.

  In the above invention, the cover coat layer may be configured to have a thickness of 35 μm or less.

  In the above invention, the cover coat layer can be made of a polyurethane resin or a polyimide resin.

  In the present invention, an insulating protective layer in which an opening having a diameter of 0.2 mm or more is formed at a position corresponding to the connecting portion is laminated on one main surface of the conductive circuit layer, and the connecting portion is provided on one main surface of the insulating protective layer. Since the jumper circuit having a thickness of 5 μm or more and 35 μm or less to be connected is formed, it is possible to prevent the jumper circuit from being peeled off by unevenness of the conductive circuit layer, and to prevent the jumper circuit from peeling off. By allowing the conductive paste to enter the opening during printing, a sufficient contact area between the connection portion of the conductive circuit and the jumper circuit can be secured. As a result, a printed wiring board having excellent connection stability can be provided.

It is a top view of the printed wiring board concerning a 1st embodiment of the present invention. It is sectional drawing which follows the II-II line of FIG. It is sectional drawing (equivalent to the II-II line cross section of FIG. 1) which shows the manufacturing process of the printed wiring board which concerns on 1st Embodiment of this invention. It is sectional drawing which expands and shows the A section of FIG.3 (D) at the time of screen printing.

Hereinafter, the printed wiring board of the present embodiment according to the present invention will be described with reference to the drawings.

In this embodiment, a description will be given by taking as an example a substrate provided with a so-called jumper circuit that intersects with other signal lines in an insulated state and connects one signal line to each other.

  A configuration of the printed wiring board 1 according to the present embodiment will be described. FIG. 1 is a plan view of a printed wiring board according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line II-II in FIG.

As shown in FIG. 1, in the printed wiring board 1 of the present embodiment, two signal lines 22a and 22a that transmit a signal A having the same voltage level transmit a signal B that has a voltage level different from the signal A. The signal lines 22b are arranged at positions sandwiched therebetween. Further, the jumper circuit 40 is connected to the connection portions 21 and 21 where the two signal lines 22a and 22a for transmitting the signal A are exposed from the openings 31 and 31, and the signal line for transmitting the signal B It is formed so as to intersect (jump) 22b in an insulated state. In other words, the jumper circuit 40 is in contact with the two connecting portions 21 through the opening 31 provided in the insulating protective layer 30, while being insulated from the signal line 22 b by the insulating protective layer 30. For this reason, the signal A input to the signal line 22a can be transmitted to the two signal lines 22a via the two connection portions 21 by skipping the signal line 22b. 1 is an example showing the jumper circuit 40, and does not limit the jumper circuit of the present invention.

  Further, as shown in the cross-sectional view of FIG. 2, the printed wiring board 1 of the present embodiment has a laminated structure, and the insulating base 10 and one main surface of the insulating base 10 from the bottom layer (in the drawing) A conductive circuit layer 20 (including a plurality of contact portions 21 and signal lines 22a and 22b) formed on the upper surface, the same applies hereinafter), an insulation protection layer 30 stacked on the conduction circuit layer 20, and insulation protection A jumper circuit 40 formed and laminated on one main surface of the layer 30 and a cover coat layer 50 covering at least the jumper circuit 40 are provided.

  Hereinafter, a method for manufacturing the printed wiring board 1 according to the present invention will be described with reference to FIGS. 3A to 3E are views showing a cross-section of a semi-finished product in the manufacturing process of the printed wiring board 1 along the line II-II in FIG.

  First, as shown in FIG. 3A, a conductor-clad laminate L in which a conductor such as metal on one side is formed is prepared. The conductor-clad laminate L is made of copper foil having a thickness of 5 μm to 50 μm on one main surface of an insulating insulating substrate 10 such as polyimide (PI) having a thickness of 10 μm to 100 μm. It is a plate-like member to which a metal foil 11 is attached. As the insulating insulating substrate 10, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyester (PE), or the like can be used.

  Next, as shown in FIG. 3B, a conductive circuit layer 20 including a plurality of connection portions 21 and signal lines 22b is formed on one main surface of the insulating substrate 10. In this embodiment, a predetermined region of the copper foil 11 is etched by a general photolithography method to form the conductive circuit layer 20 having a desired pattern. In addition, the formation method of the conductive circuit layer 20 is not limited to the above-described method, and the conductive circuit layer 20 is formed by using a conductive paste or carbon paste containing a metal such as silver on the main surface of the insulating base material 10. The conductive circuit layer 20 may be formed by screen printing according to the pattern, or the conductive circuit layer 20 may be formed by sputtering.

Next, as illustrated in FIG. 3C, the insulating protective layer 30 is formed over the conductive circuit layer 20. The insulating protective layer 30 of the present embodiment includes a film 33 made of a polyimide film and a polyimide-based adhesive layer 32, and has an overall thickness of 27.5 μm to 60 μm.

In addition, the insulating protective layer 30 of the present embodiment has openings 31 formed at positions facing the contact portions 21 included in the conductive circuit layer 20. That is, the central portion of the opening 31 is formed to be at the same position as the central portion of the connection portion 21 in the XY plane of the printed wiring board 1 (see FIG. 1). The opening 31 provided in the insulating protective layer 30 is a through hole, and is formed in advance at a predetermined position by a method of punching with a mold or the like.

  By the way, as described above, the printed wiring board 1 of the present embodiment has a laminated structure of different materials. Therefore, in the heat treatment such as reflow, the printed wiring board 1 may be distorted due to a difference in thermal expansion coefficient of each material. is there. If the printed wiring board 1 is distorted, the connection portion 21 and the contact portion 41 of the jumper circuit 40 may be peeled off, so that a sufficient contact area between the connection portion 21 and the contact portion 41 of the jumper circuit 40 is ensured. Need to be manufactured.

Since the contact area of the connection portion 21 and the contact portion 41 of the jumper circuit 40 is determined according to the opening area of the opening 31 at the time of manufacture, the diameter φ of the opening 31 at the time of manufacture is set to 0.2 mm or more. It is desirable. When the diameter φ of the opening 31 is less than 0.2 mm, the conductive paste does not sufficiently enter the opening 31 when forming the jumper circuit 40 described later, and the contact portion 41 between the connection portion 21 and the jumper circuit 40. This is because the contact area may be reduced. The upper limit of the diameter φ of the opening 31 is not particularly limited. However, if the diameter φ of the opening 31 is too large, the wiring pattern of the conductive circuit layer 20 is wasted, and the density of the wiring pattern is hindered. It is desirable to set as appropriate according to the demand for product miniaturization.

The material of the insulating protective layer 30 is not particularly limited, and a material based on a polyimide resin, a polyester resin, an epoxy resin, an acrylic resin, a polyurethane resin, or the like can be used. From the viewpoint of reducing the dimensional error, the adhesive layer 32 and the film 33 of the insulating protective layer 30 are desirably made of the same resin material, but different resin materials can also be used. In addition, the formation method of the insulating protective layer 30 is not limited, It can form by screen printing using the cover coat ink based on a polyimide resin or an epoxy resin.

  In this step, after the insulating protective layer 30 is laminated on the conductive circuit layer 20 so that the opening 31 of the insulating protective layer 30 and the contact portion 21 of the conductive circuit layer 20 face each other in the XY plane (see FIG. 1), heat treatment is performed. As a result, the adhesive layer 32 of the insulating protective layer 30 is thermally cured, and the conductive circuit layer 20 and the film 33 of the insulating protective layer 30 are bonded.

Next, as shown in FIG. 3D, a jumper circuit 40 for connecting the connection portions 21 to each other on one main surface of the insulating protective layer 30 is screen-printed using a conductive paste.

  In the present embodiment, the conductive paste is screen-printed so that the thickness T1 of the jumper circuit 40 between the contact portions 21 (the thickness of the jumper circuit 40 other than the opening 31) is 5 μm or more and 35 μm or less. The reason why the thickness T1 of the jumper circuit 40 is set to 5 μm or more is that one main surface (front surface) of the insulating protective layer 30 which is the printed surface of the jumper circuit 40 is affected by the conductive circuit layer 20 which is the lower layer. Therefore, if the thickness T1 of the jumper circuit 40 is less than 5 μm, the conductive paste flows into the concave portion on the surface of the insulating protective layer 30, and the thickness T1 of the convex jumper circuit 40 is not good. This is because there is a case where blurring occurs. On the other hand, the thickness T1 of the jumper circuit 40 is set to 35 μm or less because the jumper circuit 40 formed tends to peel off when the thickness T1 of the jumper circuit 40 is greater than 35 μm. The basis for this will be described in the examples described later.

  The conductive paste used in this embodiment is a so-called silver paste containing silver particles. The viscosity of this silver paste is 250 ± 50 dPa · sec.

  FIG. 4 is a partially enlarged view showing an A portion of FIG. 3D during screen printing. As shown in FIG. 4, a screen plate H having a mesh count of 100 to 400 on which a transmission layer corresponding to the pattern of the jumper circuit 40 is formed is set on one main surface of the insulating protective layer 30 and moves in the arrow X direction. The silver paste P extruded through the transmission layer of the screen plate H by the squeegee S is printed in a predetermined region on one main surface of the insulating protective layer 30.

  In the present embodiment, the mesh count is set to 100 or more because when the mesh count is less than 100, the aperture ratio of the screen plate H increases, the amount of ink pushed out increases, and the extension of the jumper circuit 40 tends to bleed. On the other hand, the mesh count is set to 400 or less because when the mesh count exceeds 400, the aperture ratio of the screen plate H decreases, the amount of extrusion of the conductive paste decreases, and the jumper circuit 40 has a sufficient thickness. This is because it cannot be secured and blurring occurs.

  By the way, when the silver paste P is printed in the region including the opening 31 shown in FIG. 4, the silver paste P pushed out by the squeegee S fills the concave portion K of the opening 31 and an appropriate contact area Q is formed. Therefore, it is necessary to control the size of the opening 31 and the amount of the silver paste P that the squeegee S extrudes. If the opening 31 is too small or the amount of the silver paste P pushed out to the squeegee S is too small, the volume ratio occupied by the corner R with respect to the recess K increases, and the contact area Q tends to decrease. On the other hand, if the opening 31 is too large or the amount of the silver paste P to be extruded is too large, a fine circuit pattern cannot be formed.

  In this embodiment, since the diameter φ of the opening 31 of the insulating protective layer 30 of the printed wiring board 1 is set to 0.2 mm or more, the silver paste P pushed out by the squeegee S sufficiently enters the recess K of the opening 31. Therefore, an appropriate contact area Q can be formed. Incidentally, the thickness D1 of the insulating substrate 10 of this embodiment is 10 μm to 100 μm, the thickness D2 of the copper foil is 5 μm to 50 μm, and the thickness of the insulating protective layer 30 is 27.5 μm to 60 μm. The thickness of the jumper circuit 40 (thickness other than the region facing the opening 31) D4 is 5 μm to 35 μm, and the thickness of the jumper circuit 40 in the opening 31 (thickness of the region facing the opening 31). D5 is 27.5 μm to 90 μm.

  In addition, since the amount of the silver paste P extruded to the squeegee S correlates with the thickness of the jumper circuit 40 to be formed, in this embodiment, the thickness of the jumper circuit 40 (thickness other than the region facing the opening 31). ) Adjust screen printing conditions so that D4 is 5 μm to 35 μm.

  By the way, the thickness (T1) of the printing layer (jumper circuit 40) in screen printing is the viscosity of the silver paste P, the mesh standard of the screen plate H, the squeegee attack angle (squeegee attachment angle), and the squeegee angle (squeegee contact). Contact angle, mounting angle), squeegee speed (squeegee movement speed, so-called printing speed), coating speed (speed when the doctor blade spreads ink from the back after the squeegee has advanced), doctor angle (applying the doctor blade) Contact angle), plate separation (the amount that the plate separates from the film immediately after transferring the ink with the squeegee), setting of the plate clearance condition (gap between the lower surface of the screen plate and the film), printing pressure (pressure applied to the squeegee) ), But if these conditions are constant, the result is that a circuit with a given thickness is printed. It can be. In this embodiment, by adjusting each condition of the above-mentioned screen printing, as a result, the thickness (thickness other than the region facing the opening 31) D4 of the jumper circuit 40 is adjusted to be 5 μm to 35 μm. To do.

  In the next step, as shown in FIG. 3E, a cover coat layer 50 covering the jumper circuit 40 is formed. In the present embodiment, the cover coat layer 50 can be formed by screen-printing a cover coat ink made of a polyester resin, a polyurethane resin, or a polyimide resin in a region including the jumper circuit 40.

  In the present embodiment, it is desirable that the cover coat layer 50 be made of polyurethane resin or polyimide resin. This is because the polyurethane resin or the polyimide resin hardly absorbs moisture and can protect the jumper circuit 40 from moisture. In particular, when the jumper circuit 40 is printed with a silver paste, it is desirable to use a polyurethane resin or a polyimide resin having a low hygroscopic property capable of preventing migration of silver particles.

  Further, it is desirable that the thickness T2 of the cover coat layer 50 (the distance between one main surface of the jumper circuit 40 and one main surface of the cover coat layer 50) be 4 μm or more and 35 μm or less. If the thickness of the cover coat layer 50 is less than 4 μm, the strength of the cover coat layer 50 is insufficient and the jumper circuit 40 cannot be protected. If the thickness of the cover coat layer 50 exceeds 35 μm, This is because the cover coat layer 50 tends to peel easily.

Although not particularly limited, in order to protect the outer edge portion of the jumper circuit 50, the outer edge of the cover coat layer 50 is located 50 μm or more outside the outer edge of the jumper circuit 50 (the end side of the substrate). It is desirable to print the cover coat layer 50 so that the distance W of 3 (E) is 50 μm or more.

  Incidentally, in the manufacturing process, heat treatment is performed to cure the insulating protective layer 30, the adhesive layer 32, and the cover coat layer 50. In addition to the diameter φ of the opening 31 of the printed wiring board 1 obtained by this heat treatment, the thickness of the jumper circuit 40, the thickness of the film 33 of the insulating protective layer 30, and the thickness of the cover coat layer 50 are as follows. Although it changes before and after the heat treatment, the amount of change is less than 1%.

That is, the printed wiring board 1 obtained by the manufacturing method described above has the laminated structure shown in FIGS. 1 and 2 and the shape and dimensions of the used members are kept substantially the same. Specifically, the diameter φ of the opening 31 of the printed wiring board 1 obtained by the manufacturing method of the present embodiment is 0.2 mm or more, and the connection portion 21 provided at a position corresponding to the opening 31 is connected. The thickness of the jumper circuit 40 to be made (thickness other than the region facing the opening 31) is 5 μm or more and 35 μm or less. Moreover, the thickness of the copper foil of the printed wiring board 1 is 5 μm to 50 μm, the thickness of the insulating protective layer 30 is 27.5 μm to 60 μm, and the thickness of the cover coat layer 50 is 35 μm or less.
The thickness of the jumper circuit 40 in the opening 31 of the printed wiring board 1 obtained by the manufacturing method described above (the thickness of the region facing the opening 31 and the thickness corresponding to D5 shown in FIG. 4) is 27. .5 μm to 90 μm. However, depending on the material, when the change in thickness of the adhesive layer 32 of the insulating protective layer 30 before and after the heat treatment becomes relatively large, less than 10%, the thickness of the insulating protective layer 30 is about 24.5 μm to 54 μm. It becomes.

  Hereinafter, Examples 1 to 10 of the printed wiring board 40 of the present embodiment will be described.

<Examples 1 and 2>
In Examples 1 and 2, the appropriate value of the diameter φ of the opening 31 of the insulating protective layer 30 at the time of manufacture was examined from the viewpoint of appropriately setting the contact area between the connection portion 21 and the contact portion 41 of the jumper circuit 40. .

  First, a test piece was prepared. A common conductor-clad laminate L in which a copper foil having a thickness of 18 μm is attached to one main surface of an insulating base material 10 having a predetermined thickness is prepared, and a common insulating property is obtained using a common material and a common method. The base material 10 and the conductive circuit layer 20 were formed. Then, two circular openings 31 having a diameter φ of 0.2 mm to 0.3 mm were formed in advance, and an insulating protective layer 30 having a thickness D3 of 27.5 to 60 μm was laminated on the conductive circuit layer 20. The insulating protective layer 30 has a two-layer structure in which an adhesive layer 32 and a film 33 are laminated. Subsequently, a jumper circuit 40 having a thickness D4 of 10 μm for connecting the two openings 31 is formed on one main surface of the insulating protective layer 30 using a silver paste having a viscosity of 250 dPa · sec and a screen plate having a mesh count of 200. Screen printed. Further, a cover coat layer was formed by printing a cover coat ink made of polyurethane resin and having a thickness T2 of 10 μm so as to cover the jumper circuit 40. Test pieces according to Examples 1 and 2 and Comparative Example 1 were prepared.

  Of the test pieces, the one having a diameter φ of the opening 31 of 0.2 mm is taken as Example 1, the one having a diameter φ of 0.3 mm is taken as Example 2, and the diameter φ of the opening 31 is 0.00. A sample having a thickness of 1 mm was designated as Comparative Example 1. For Examples 1 and 2 and Comparative Example 1, 100 samples (N = 100) each having a thickness D3 (see FIG. 4) of the insulating protective layer 30 of 27.5 μm, 37.5 μm, 50 μm, and 60 μm A piece was prepared.

  Next, with respect to Examples 1 and 2 and Comparative Example 1, the printing defect rate was obtained. Specifically, after printing of the jumper circuit 40, when a lack of printing was visually recognized in a region having a diameter of ½ or more of the diameter φ in the opening 31, it was determined to be defective. The ratio of the number judged to be defective with respect to the entire sample was obtained as the printing defect rate. The results are shown in Table 1.

  Subsequently, contact resistance was evaluated for Examples 1 and 2 and Comparative Example 1. Specifically, the contact resistance when a predetermined voltage is applied between the connection part 21 of the conductive circuit layer 20 and the contact part 41 of the jumper circuit 40 before and after the heat treatment at 250 ° C. × 10 sec is measured. When the contact resistance is less than a predetermined value, the contact resistance is evaluated as good (◯) because it is in a conductive state, and when the contact resistance is equal to or higher than the predetermined value, the contact resistance is evaluated as defective (×) because it is a disconnected state. The results are shown in Table 1. When the contact resistance is not included, it is expressed as good (◯), and when the contact resistance is defective, it is expressed as defective (×).

  As shown in Table 1, in Example 1 in which the diameter φ of the opening 31 is 0.2 mm and in Example 2 in which the diameter φ of the opening 31 is 0.3 mm, the thickness D3 of the insulating protective layer 30 is the same. Was 27.5 μm, 37.5 μm, 50 μm, and 60 μm, the printing defect rate was zero, and the contact resistance was good both before and after the heat treatment. On the other hand, in Comparative Example 1 in which the diameter φ of the opening 31 is 0.1 mm, printing failure occurs regardless of whether the thickness D3 of the insulating protective layer 30 is 27.5 μm, 37.5 μm, 50 μm, or 60 μm. The rate was as high as 3% to 5%, and the contact resistance after heat treatment was poor (disconnected state).

  Thus, it was confirmed that the printed wiring board 1 having a good printing state and a good contact state can be obtained by setting the diameter φ of the opening 31 to 0.2 mm or more. The upper limit of the diameter φ of the opening 31 can be appropriately set according to the size of the contact portion 21 and the thickness of the signal line 22a.

<Examples 3 to 5>
In Examples 3-5, the appropriate value of thickness D4 (refer FIG. 4) of the jumper circuit 40 was examined from a viewpoint of setting the contact area of the connection part 21 and the contact part 41 of the jumper circuit 40 appropriately.

  First, Example 1 except that the thickness D4 of the jumper circuit 40 is 5 μm to 35 μm, the diameter φ of the opening 31 is 0.2 mm, and the thickness D3 of the insulating protective layer 30 is 37.5. Using common materials and methods, 100 test pieces (N = 100) were prepared for each of Examples 3 to 5 and Comparative Examples 2 and 3 below.

  The jumper circuit 40 having a thickness D4 of 5 μm is referred to as Example 3, the thickness D4 of 10 μm is referred to as Example 4, the thickness D4 of 35 μm is referred to as Example 5, and the thickness D4 is 4 μm. Was a comparative example 2, and a thickness D4 of 36 μm was designated as a comparative example 3.

  Next, for Examples 3 to 5 and Comparative Examples 2 and 3, the printing defect rate was obtained by the same method as in Example 1. The results are shown in Table 2.

Subsequently, for Examples 3 to 5 and Comparative Examples 2 and 3, a cross-cut test (JISK5400) was performed to evaluate the adhesion of the jumper circuit. In the cross-cut test, a grid-like scratch is made with a predetermined cutter so that 100 squares can be formed in the printed part 100 mm ² of the test piece, and a tape having an adhesive surface is adhered thereto. This is a test to peel off sharply and observe the occurrence of peeling. In the result of the cross-cut test, when there was no peeled cell, it was evaluated as good adhesion (◯), and when there was a peeled cell, it was evaluated as poor adhesion (×). The results are shown in Table 2. When the adhesiveness was not included, it was expressed as good (◯), and when the adhesiveness was poor, it was expressed as defective (x).

  Furthermore, the sheet resistance was evaluated for Examples 3 to 5 and Comparative Examples 2 and 3. The jumper circuit 40 formed between the two connecting portions 21 is divided into M unit regions, and the entire resistance value of the jumper circuit 40 is divided by the number of unit regions (M) to obtain a resistance value per unit region. Asked. The results are shown in Table 2. When the sheet resistance is equal to or greater than a predetermined value, it is expressed as “disconnection”.

  As shown in Table 2, in Examples 3 to 5 in which the thickness D4 of the jumper circuit 40 is 5 μm to 35 μm, the printing defect rate is zero, the adhesion is good, and the sheet resistance is less than a predetermined value. there were. On the other hand, Comparative Example 2 in which the thickness D4 of the jumper circuit 40 was 4 μm was evaluated as being in a disconnected state because of a high printing defect rate of 5% and an area resistance of a predetermined value or more, although it had adhesion. Moreover, although the comparative example 3 whose thickness D4 of the jumper circuit 40 is 36 micrometers has evaluated the printing defect rate and the area resistance, it has confirmed that adhesiveness was inferior.

  Thus, it has confirmed that the printed wiring board 1 with a favorable printing state, a close_contact | adherence state, and sheet resistance can be obtained by making thickness D4 of the jumper circuit 40 into 5 micrometers-35 micrometers.

<Examples 6 to 8>
In Examples 6 to 8, from the viewpoint of preventing peeling of the cover coat layer 50, an appropriate value of the thickness T2 of the cover coat layer 50 (see FIG. 3E) was examined.

  The main component of the cover coat layer 50 is different, the thickness T2 (see FIG. 3E) of the cover coat layer 50 is 5 μm to 35 μm, the diameter φ of the opening 31 is 0.2 mm, and the insulation protection Except for the thickness D3 of the layer 30 being 37.5, each of the following Examples 6 to 8 and Comparative Examples 4 to 6 using the same materials and methods as in Example 1 (N = 100) ) Was prepared.

  The cover coat layer 50 is made of a polyester-based resin and the thickness T2 is 4 μm, 5 μm, 10 μm, and 35 μm as Examples 6 (1) to (4), and is made of a polyurethane-based resin, and the thickness T2 is 4 μm. Examples having the thickness of 5 μm, 10 μm, and 35 μm are referred to as Examples 7 (1) to (4), the cover coat layer 50 is made of polyimide resin, and the thickness T2 is 4 μm, 5 μm, 10 μm, and 35 μm. (1) to (4).

  Further, the cover coat layer 50 is made of a polyester resin and the thickness T2 is 36 μm as Comparative Example 4, and the cover coat layer 50 is made of a polyurethane resin and the thickness T2 is 36 μm as Comparative Example 5. The cover coat layer 50 is made of polyimide resin and has a thickness T2 of 36 μm as Comparative Example 6.

  A cross-cut test was performed on Examples 6 to 8 and Comparative Examples 4 to 6 in the same manner as in Examples 3 to 5, and the adhesion of the example cover coat layer 50 was evaluated. The results are shown in Table 3.

  As shown in Table 3, the adhesiveness of the cover coat layers 50 of Examples 6 to 8 in which the thickness T2 of the cover coat layer 50 is 35 μm or less is good regardless of the type of the resin. It was confirmed that the adhesion of the cover coat layers 50 of Comparative Examples 4 to 6 in which the thickness T2 of 50 was 36 μm or more was poor regardless of the type of resin.

  As described above, it was confirmed that the printed wiring board 1 having a good adhesion state of the cover coat layer 50 can be obtained by setting the thickness T2 of the cover coat layer 50 to 35 μm or less, particularly 4 μm to 35 μm.

<Examples 9 and 10>
In Examples 9 and 10, the type of resin that is the main component of the cover coat layer 50 was examined from the viewpoint of preventing the jumper circuit 40 from migrating.

  First, a common test piece was prepared under the same conditions as in Examples 6-8. The cover coat layer 50 was made of polyurethane resin as Example 9, the cover coat layer 50 was made of polyimide resin as Example 10, and the cover coat layer 50 was made of polyester resin. This was designated as Comparative Example 7.

  Next, a migration test was performed. In the migration test, a voltage of 50 V was applied for 1000 hours under a temperature of 85 ° C./humidity of 85% RH, and then the insulation resistance was measured and the appearance was inspected. The results are shown in Table 4.

  In this embodiment, in order to determine whether or not migration has occurred, the insulation resistance is measured. If the insulation resistance value is equal to or greater than a predetermined value, no migration has occurred and the insulation is evaluated as good (O). When the value was less than the predetermined value, migration occurred and it was evaluated as insulation failure (x). The results are shown in Table 4. When an insulation failure was not included, it was indicated as good (◯), and when an insulation failure was included, it was indicated as failure (x).

  From the same point of view, whether or not silver is deposited on the surface of the cover coat layer 50 is visually observed. If silver is not deposited, the appearance is evaluated as good (◯), and silver is deposited. The case was evaluated as poor appearance (x). The results are shown in Table 4. When an appearance defect was not included, it was expressed as “good” (◯), and when an appearance defect was included, it was expressed as “bad” (x). Incidentally, if the appearance is poor, it can be evaluated that migration has occurred.

  As shown in Table 4, Examples 9 (1) to (5) in which the cover coat layer 50 is made of a polyurethane resin and Examples 10 (1) to (5) in which the cover coat layer 50 is made of a polyimide resin. In 5), both the insulation resistance and the results of the appearance inspection were good. On the other hand, Comparative Examples 7 (1) to (5) in which the cover coat layer 50 was made of a polyester resin had poor insulation resistance and / or appearance results.

  Thus, it has been confirmed that the occurrence of migration of the jumper circuit 40 can be suppressed by configuring the cover coat layer 50 with polyurethane resin or polyimide resin. Since the cover coat ink of polyurethane resin is inexpensive, the cost can be reduced while suppressing the occurrence of migration by forming the cover coat layer 50 with the polyurethane resin.

  Further, considering the results of Examples 6 to 8 and the results of Examples 9 and 10 comprehensively, the cover coat layer 50 is made of polyurethane resin or polyimide resin and has a thickness of 35 μm or less. It is desirable to do. By configuring the cover coat layer 50 in this manner, the adhesion is good and the occurrence of migration can also be prevented.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Printed wiring board 10 ... Insulating base material 11 ... Metal foil L ... Conductor tension laminated board L
DESCRIPTION OF SYMBOLS 20 ... Conductive circuit layer 21 ... Connection part 22a ... Signal line of signal A 22b ... Signal line of signal B 30 ... Insulation protective layer 31 ... Opening part 32 ... Adhesive layer 33 ... Film 40 ... Jumper circuit 41 ... Contact part 50 ... Cover coat layer

Claims (10)

Forming a conductive circuit layer including a plurality of connecting portions on one main surface of the insulating substrate;
Forming an insulating protective layer having an opening having a diameter of 0.2 mm or more at a position corresponding to the connection portion on one main surface of the conductive circuit layer;
Printing a conductive paste on one main surface of the insulating protective layer so that a thickness of a jumper circuit for connecting the connecting portion is 5 μm or more and 35 μm or less;
Forming a cover coat layer covering the jumper circuit.   The method for manufacturing a printed wiring board according to claim 1, wherein the insulating protective layer has a thickness of 27.5 μm to 60 μm.   The method for manufacturing a printed wiring board according to claim 1, wherein the conductive paste contains silver particles and has a viscosity of 250 ± 50 dPa · sec.   The method for manufacturing a printed wiring board according to claim 1, wherein the cover coat layer has a thickness of 35 μm or less.   The method for manufacturing a printed wiring board according to any one of claims 1 to 4, wherein the cover coat layer is a polyurethane resin or a polyimide resin. An insulating substrate;
A conductive circuit layer including a plurality of connection portions formed on one main surface of the insulating base;
An insulating protective layer formed on one main surface of the conductive circuit layer and having an opening at a position corresponding to the connection;
A jumper circuit that is printed using a conductive paste on one main surface of the insulating protective layer and connects the connection portion;
A cover coat layer covering the jumper circuit,
A printed wiring board in which the diameter of the opening is 0.2 mm or more, and the thickness of the jumper circuit is 5 μm or more and 35 μm or less.   The printed wiring board according to claim 6, wherein the insulating protective layer has a thickness of 27.5 μm or more and 60 μm or less.   The printed wiring board according to claim 6, wherein the conductive paste contains silver particles.   The printed wiring board according to claim 6, wherein the cover coat layer has a thickness of 35 μm or less.   The printed wiring board according to any one of claims 6 to 9, wherein the cover coat layer is a polyurethane resin or a polyimide resin.

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