JP4845705B2 - Printed wiring board, manufacturing method thereof, and electronic device - Google Patents

Description

  The present invention relates to a printed wiring board, a manufacturing method thereof, and an electronic apparatus using the same.

  Since a flexible printed wiring board has a high bending property, it is used for a movable part in a case of an electronic device. Hereinafter, the flexible printed wiring board is abbreviated as a printed wiring board.

In recent years, with the downsizing and thinning of electronic devices, the layout space of a printed wiring board mounted on the electronic device is also reduced, and the printed wiring board is required to have very high bending characteristics. In order to improve the bending characteristics of the printed wiring board, the thickness of the insulator layer of the printed wiring board is reduced (see, for example, Patent Document 1).
Japanese Patent Application Laid-Open No. 2001-7451

  By the way, a printed wiring board may be arranged in a bent state in a movable case such as a slide-type mobile phone. In such a case, the insulator layer of the printed wiring board comes into contact with the inner surface of the case by sliding the case. Thereby, stress is applied to the contact portion of the printed wiring board.

  In particular, when the thickness of the insulating layer of the printed wiring board is reduced as described above, the radius of curvature at the time of bending of the printed wiring board is reduced, so that the stress applied to the contact portion of the printed wiring board is increased. As a result, when the printed wiring board is repeatedly contacted with the case, the resistance value of the conductor pattern, which is the wiring pattern, may increase or break.

  An object of the present invention is to provide a printed wiring board in which an increase in resistance value and disconnection of a conductor pattern due to repeated contact with a part in an electronic device are prevented, a manufacturing method thereof, and an electronic device using the printed wiring board. It is.

(1) A printed wiring board according to a first invention is a printed wiring board used in a state bent along one direction, and is formed on the first insulator layer and the first insulator layer. A conductor pattern to be formed; and a second insulator layer formed on the first insulator layer so as to cover the conductor pattern, the outer side of the first and second insulator layers being bent. A plurality of stripe-shaped irregularities extending in parallel to each other so as to be orthogonal to one direction are formed on the surface of the insulator layer, and the plurality of stripe-shaped irregularities are formed by stripe-shaped concave portions and stripe-shaped convex portions. The thickness of the insulating layer on the outer side of the concave portion is smaller than the thickness of the insulating layer on the outer side of the striped convex portion .

In the printed wiring board, a plurality of striped irregularities extending in parallel to each other so as to be orthogonal to one direction are formed on the surface of the insulating layer that is outside when bent among the first and second insulating layers. ing. Thereby, when the printed wiring board is disposed in the electronic device in a bent state, the contact area between the surface of the outer insulator layer and the portion in the electronic device is reduced, and stress due to contact is reduced. Therefore, even when the radius of curvature of the printed wiring board at the time of bending is small, an increase in the resistance value and disconnection of the conductor pattern due to repeated contact of the printed wiring board with a portion in the electronic device can be prevented.

  (2) The height from the bottom to the top of the irregularities is preferably 0.2 μm or more and 3.0 μm or less.

  In this case, the contact area between the outer insulator layer and the portion in the electronic device can be made sufficiently small while sufficiently ensuring the minimum thickness of the insulator layer that becomes the outside when bent. Thus, the resistance value of the conductor pattern and the breakage of the conductor pattern due to repeated contact of the printed wiring board with the portion in the electronic device are reliably prevented while the conductor pattern is sufficiently protected by the outer insulator layer.

  (3) The minimum radius of curvature of the insulating layer that becomes the outside when bent may be 1.0 mm or less.

  Thus, even when the radius of curvature of the outer insulating layer is small when bent, the printed wiring board repeatedly contacts the part in the electronic device because the surface of the outer insulating layer is uneven. As a result, an increase in resistance value and disconnection of the conductor pattern are prevented.

  (4) The first insulator layer may be a base insulator layer, the second insulator layer may be a cover insulator layer, and the insulator layer that becomes outside when bent may be a cover insulator layer.

  In this case, since the surface of the cover insulator layer is uneven, when the printed wiring board is placed in the electronic device in a bent state, the surface of the outer cover insulator layer and the portion in the electronic device The contact area is reduced, and the stress due to contact is reduced. Therefore, even when the radius of curvature of the printed wiring board at the time of bending is small, an increase in the resistance value and disconnection of the conductor pattern due to repeated contact of the printed wiring board with a portion in the electronic device can be prevented.

(5) A printed wiring board manufacturing method according to a second invention is a printed wiring board manufacturing method used in a bent state, wherein a conductor pattern is formed on a first insulator layer, and a conductor A step of forming a second insulator layer on the first insulator layer so as to cover the pattern, and a direction of the first and second insulator layers on the surface of the insulator layer that is outside when bent Forming a plurality of stripe-shaped irregularities extending in parallel to each other so as to be orthogonal to each other , the plurality of stripe-shaped irregularities comprising a stripe-shaped concave portion and a stripe-shaped convex portion, and the outside of the stripe-shaped concave portion The thickness of the insulating layer is smaller than the thickness of the insulating layer on the outer side of the stripe-shaped convex portion .

According to the method for manufacturing a printed wiring board, a plurality of stripe-like shapes extending parallel to each other so as to be orthogonal to one direction are formed on the surface of the insulating layer that is outside when bent among the first and second insulating layers . Unevenness is formed. Thereby, when the printed wiring board is disposed in the electronic device in a bent state, the contact area between the surface of the outer insulator layer and the portion in the electronic device is reduced. Therefore, even when the radius of curvature of the printed wiring board at the time of bending is small, an increase in the resistance value and disconnection of the conductor pattern due to repeated contact of the printed wiring board with a portion in the electronic device can be prevented.

(6) An electronic device according to a third aspect of the present invention includes a case and a printed wiring board disposed in a bent state in the case. The printed wiring board includes a first insulator layer and a first insulator. A conductor pattern formed on the layer and a second insulator layer formed on the first insulator layer so as to cover the conductor pattern, wherein the bent state of the first and second insulator layers A plurality of striped irregularities extending in parallel to each other so as to be orthogonal to one direction are formed on the surface of the insulating layer that is outside.

In the electronic device, a printed wiring board is arranged in a bent state in a case. A plurality of striped irregularities extending in parallel to each other so as to be orthogonal to one direction are formed on the surface of the outer insulator layer in a bent state among the first and second insulator layers of the printed wiring board. Thereby, the contact area between the surface of the outer insulator layer and the inner surface of the case is reduced, and the stress due to contact is reduced. Therefore, even when the radius of curvature of the printed wiring board in the bent state is small, an increase in the resistance value of the conductor pattern and disconnection due to repeated contact of the printed wiring board with the inner surface of the case are prevented.

  (7) The case may have a movable part that is movably provided, and the insulating layer on which the unevenness of the printed wiring board is formed may contact the movable part.

  In this case, with the movement of the movable part of the case, the bent portion moves while the surface of the insulator layer outside the printed wiring board repeatedly contacts the movable part. Even in such a case, since the unevenness is formed on the surface of the outer insulator layer, the contact area between the surface of the outer insulator layer and the movable part of the case is reduced, and the stress due to the contact is reduced. Therefore, even when the radius of curvature of the printed wiring board in the bent state is small, an increase in the resistance value of the conductor pattern and disconnection due to repeated contact of the printed wiring board with the movable portion of the case are prevented.

  According to the present invention, when the printed wiring board is placed in the electronic device in a bent state, the contact area between the surface of the outer insulator layer and the portion in the electronic device is reduced, and stress due to contact is reduced. The Therefore, even when the radius of curvature of the printed wiring board at the time of bending is small, an increase in the resistance value and disconnection of the conductor pattern due to repeated contact of the printed wiring board with a portion in the electronic device can be prevented.

  Hereinafter, a flexible printed wiring board according to an embodiment of the present invention will be described with reference to the drawings. In the following description, the flexible printed wiring board is abbreviated as a printed wiring board.

(1) Method for Manufacturing Printed Wiring Board FIG. 1 is a process sectional view showing a method for manufacturing a printed wiring board according to an embodiment of the present invention.

  First, as shown in FIG. 1A, a two-layer base material 10 having a laminated structure of a base insulator layer 1 and a conductor layer 2 is prepared. The base insulator layer 1 is made of, for example, a polyimide film, and the conductor layer 2 is made of, for example, copper. The thickness of the base insulator layer 1 is preferably 10 μm or more and 20 μm or less, for example, 12.5 μm. The thickness of the conductor layer 2 is preferably 5 μm or more and 25 μm or less, for example, 12 μm.

  Next, as shown in FIG. 1B, the conductor layer 2 is etched to form a plurality of conductor patterns 2a. Each conductor pattern 2a has a width of 15 μm to 200 μm, for example, 100 μm. The interval between the conductor patterns 2a is not less than 15 μm and not more than 200 μm, for example, 100 μm. The conductor pattern 2a corresponds to a wiring pattern.

  Next, as shown in FIG. 1C, a cover insulator layer 4 is formed on the base insulator layer 1 via an adhesive layer 3 so as to cover the conductor pattern 2 a. As the adhesive layer 3, for example, an adhesive mainly composed of an epoxy resin is used. Moreover, as the cover insulator layer 4, for example, a polyimide film is used. The thickness of the adhesive layer 3 is preferably 10 μm or more and 15 μm or less, for example, 12.5 μm. The thickness of the cover insulator layer 4 is preferably 2 μm or more and 30 μm or less, for example, 15 μm.

  Thereafter, as shown in FIG. 1 (d), irregularities 5 are formed on the surface of the cover insulating layer 4 that becomes the outside when bent. In the present embodiment, the unevenness 5 is formed on the entire surface of the cover insulating layer 4 using an abrasive. The unevenness 5 may be formed on the surface of the cover insulator layer 4 using sandpaper or a polishing roll, or the unevenness 5 may be formed by sublimating the surface of the cover insulator layer 4 with a laser beam. . The unevenness 5 may be partially formed on the surface of the cover insulator layer 4 in the bent region of the printed wiring board. In this way, the printed wiring board 100 is completed.

(2) Method for Confirming Concavity and Concavity 5 FIG. 2 is an enlarged cross-sectional view of the concavity and convexity 5 formed on the surface of the cover insulator layer 4.

  In FIG. 2, SEM (scanning electron microscope) is used to confirm the height h from the bottom to the top of the unevenness 5. The height h of the unevenness 5 is measured by observing the cross section of the printed wiring board 100 with an SEM.

  In this case, if the height h of the unevenness 5 is smaller than 0.2 μm, the contact area between the inner surface of the case of the electronic device described later and the cover insulator layer 4 cannot be made sufficiently small. Further, if the height h of the unevenness 5 is larger than 3.0 μm, the minimum thickness of the cover insulator layer 4 becomes small, so that the conductor pattern 2 a cannot be sufficiently protected by the cover insulator layer 4. Therefore, the height h of the unevenness 5 is preferably 0.2 μm or more and 3.0 μm or less. Thereby, as will be described later, it is possible to more reliably prevent an increase in resistance value and disconnection of the conductor pattern 2a.

(3) Bending Method of Printed Wiring Board 100 FIG. 3A is a schematic perspective view showing a state when the printed wiring board 100 according to the present embodiment is bent, and FIG. It is an expansion perspective view of A section. As shown in FIG. 3, the printed wiring board 100 is bent so that the cover insulator layer 4 is on the outside and the base insulator layer 1 is on the inside. As a result, irregularities 5 are formed on the outer surface of the printed wiring board 100 in a bent state. The unevenness 5 extends in a stripe shape parallel to the bending direction.

(4) Electronic device using printed wiring board 100 FIG. 4 is a cross-sectional view showing an example of an electronic device using the printed wiring board 100 according to the present embodiment. The electronic device 50 in FIG. 4 is a slide-type mobile phone.

  As shown in FIGS. 4A and 4B, the electronic device 50 includes an upper case 51 and a lower case 52. The upper case 51 is slidably attached to the lower case 52.

  A rigid printed wiring board 53 is disposed in the upper case 51, and a rigid printed wiring board 54 is disposed in the lower case 52. An opening 55 is provided on the lower surface of the upper case 51, and an opening 56 is provided on the upper surface of the lower case 52.

  The printed wiring board 100 according to the present embodiment is arranged to extend from the inside of the upper case 51 to the inside of the lower case 52 through the opening 55 of the upper case 51 and the opening 56 of the lower case 52. ing. One end of the printed wiring board 100 is connected to a rigid printed wiring board 53 in the upper case 51, and the other end of the printed wiring board 100 is connected to a rigid printed wiring board 54 in the lower case 52.

  As shown in FIG. 4A, in the state where the upper case 51 overlaps the lower case 52, the outer surface of the printed wiring board 100 is bent in the state where the printed wiring board 100 is bent. It is in contact with the upper inner surface. The minimum curvature radius of the cover insulating layer 4 (see FIG. 3) when bent is, for example, 1.0 mm or less.

  As shown in FIG. 4B, when the upper case 51 is slid in the direction of the arrow, the outer surface of the printed wiring board 100 is hardly in contact with the upper inner surface of the lower case 52.

  When the electronic device 50 is used, the upper case 51 is repeatedly slid with respect to the lower case 52 so that the outer surface of the printed wiring board 100 repeatedly contacts the inner surface of the lower case 52 and the printed wiring The bent portion of the substrate 100 moves repeatedly.

  Since the printed wiring board 100 according to the present embodiment has the irregularities 5 formed on the surface of the cover insulating layer 4 that becomes the outer side when bent, the contact area between the surface of the printed wiring board 100 and the inner surface of the case is small. Thus, stress due to contact is reduced. Thereby, even when the radius of curvature of the printed wiring board 100 is small, an increase in resistance value and disconnection of the conductor pattern 2a due to repeated contact of the printed wiring board 100 with the inner surface of the case are prevented.

(5) Other Embodiments The material of the base insulator layer 1 is not limited to polyimide, and other insulating materials such as a polyethylene terephthalate film, a polyether nitrile film, and a polyether sulfone film may be used.

  The material of the conductor layer 2 and the conductor pattern 2a is not limited to copper, and other metal materials such as copper alloy, gold, and aluminum may be used.

  The material of the cover insulator layer 4 is not limited to polyimide, and other insulating materials such as a polyethylene terephthalate film, a polyether nitrile film, and a polyether sulfone film may be used.

  The method for forming the conductor pattern 2a is not limited to the subtractive method, and a semi-additive method may be used. In this case, the conductor pattern 2 a may be formed on the base insulator layer 1 by plating without using the two-layer base material 10.

  The printed wiring board according to the present invention is not limited to a mobile phone, and can be used for various electronic devices such as a portable information terminal and a personal computer.

(6) Example (Example 1)
In Example 1, the printed wiring board 100 was manufactured by the manufacturing method shown in FIG. 1 as follows.

  A two-layer base material 10 including a base insulator layer 1 and a conductor layer 2 was prepared, and the conductor layer 2 was etched to form a conductor pattern 2a. The base insulator layer 1 is made of polyimide having a thickness of 12.5 μm, and the conductor layer 2 is made of copper having a thickness of 12 μm. The width of the conductor pattern 2a was 100 μm, and the interval between the conductor patterns 2a was also 100 μm.

  Next, a cover insulator layer 4 made of a polyimide film having a thickness of 12.5 μm is interposed through an adhesive layer 3 having a thickness of 15 μm mainly composed of an epoxy resin so as to cover the conductor pattern 2 a on the surface of the base insulator layer 1. Formed.

  Thereafter, the surface of the cover insulator layer 4 was polished with # 2000 sandpaper so that the unevenness 5 was formed on the entire surface of the cover insulator layer 4. In this case, the height h of the unevenness 5 was 1.0 μm.

(Example 2)
In Example 2, a printed wiring board was produced in the same manner as in Example 1 except that the surface of the cover insulator layer 4 was polished using a roll coated with an alumina abrasive having a particle size of 4000. In this case, the height h of the unevenness 5 was 0.5 μm.

(Example 3)
In Example 3, a printed wiring board was fabricated in the same manner as in Example 1 except that the surface of the cover insulator layer 4 was polished using # 1500 sandpaper. In this case, the height h of the irregularities 5 was 2.5 μm.

(Comparative example)
In the comparative example, a printed wiring board was produced in the same manner as in Example 1 except that the unevenness was not formed on the surface of the cover insulator layer 4.

(Evaluation)
The bending test of the printed wiring board 100 of Example 1, Example 2, and Example 3 and the printed wiring board of the comparative example was performed by the method shown in FIG.

  FIG. 5 is a schematic diagram showing a bending test method. As shown in FIGS. 5A and 5B, the movable unit 62 can be reciprocated in the direction of the arrow by the driving device 61. A fixed plate 63 is disposed above the drive device 61.

  The printed wiring board 100 of Example 1 is bent so that the cover insulator layer 4 faces outside, and one end portion is attached to the movable portion 62 so that the surface of the cover insulator layer 4 contacts the fixed plate 63, and the other end The part was attached to the lower surface of the fixed plate 63. Then, the interval between the movable portion 62 and the fixed plate 63 was set so that the radius of curvature of the cover insulating layer 4 of the printed wiring board 100 was 1 mm. In this state, by reciprocating the movable part 62 at a speed of 10 times / second, the conductor pattern of the printed wiring board 100 is repeatedly brought into contact with the surface of the fixed plate 63 while repeatedly contacting the outer surface of the printed wiring board 100. The resistance value of 2a was measured.

  The printed circuit boards of Example 2, Example 3, and Comparative Example were also subjected to a bending test by the same method.

  For the printed wiring board 100 of Example 1, no increase in the resistance value of the conductor pattern 2a was observed even when contact was made 200,000 times or more. Moreover, the disconnection of the conductor pattern 2a was not recognized.

  For the printed wiring board of Example 2, no increase in the resistance value of the conductor pattern was observed even when contact was made 200,000 times or more. Also, no disconnection of the conductor pattern was observed.

  For the printed wiring board of Example 3, no increase in the resistance value of the conductor pattern was observed even when contact was made 200,000 times or more. Also, no disconnection of the conductor pattern was observed.

  About the printed wiring board of the comparative example, the resistance value of the conductor pattern rose rapidly by the contact of about 50,000 times, and the conductor pattern was disconnected.

  From these results, by forming irregularities on the surface of the cover insulator layer that becomes the outside when bent, even when the radius of curvature of the printed circuit board is small, the printed circuit board repeatedly contacts the inner surface of the case. It was found that the resistance value of the conductor pattern and the disconnection were prevented. This is presumably because the contact area between the surface of the printed wiring board and the inner surface of the case is reduced due to the unevenness formed on the surface of the cover insulator layer, and stress due to contact is reduced.

  The printed wiring board according to the present invention can be effectively used for an electronic device having a movable part.

It is process sectional drawing which shows the manufacturing method of the printed wiring board which concerns on one embodiment of this invention. It is an expanded sectional view of the unevenness | corrugation formed in the surface of a cover insulator layer. It is the typical perspective view which shows the state at the time of the bending of the printed wiring board which concerns on this Embodiment, and the expansion perspective view of A part. It is sectional drawing which shows an example of the electronic device using the printed wiring board which concerns on this Embodiment. It is a schematic diagram which shows the method of a bending test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base insulator layer 2 Conductor layer 2a Conductor pattern 3 Adhesive layer 4 Cover insulator layer 5 Concavity and convexity 100 Printed wiring board 50 Electronic device 51, 52 Case 53, 54 Rigid printed wiring board 55, 56 Opening 61 Drive device 62 Movable Part 63 Fixed plate

Claims (7)

A printed wiring board used in a bent state along one direction,
A first insulator layer;
A conductor pattern formed on the first insulator layer;
A second insulator layer formed on the first insulator layer so as to cover the conductor pattern;
A plurality of striped irregularities extending in parallel to each other so as to be orthogonal to the one direction are formed on the surface of the insulating layer that is outside when bent among the first and second insulating layers ,
The plurality of stripe-shaped projections and depressions are formed of a stripe-shaped recess and a stripe-shaped projection, and the insulating layer on the outside of the stripe-shaped recess has the thickness on the outside of the stripe-shaped projection. A printed wiring board having a thickness smaller than that of the printed circuit board. The printed wiring board according to claim 1, wherein a height from the bottom to the top of the unevenness is 0.2 μm or more and 3.0 μm or less. The printed wiring board according to claim 1 or 2, wherein the minimum radius of curvature of the insulating layer that is outside when bent is 1.0 mm or less. The first insulator layer is a base insulator layer, the second insulator layer is a cover insulator layer, and the insulator layer that is outside when bent is a cover insulator layer. The printed wiring board according to claim 1. A printed wiring board manufacturing method used in a bent state,
Forming a conductor pattern on the first insulator layer;
Forming a second insulator layer on the first insulator layer so as to cover the conductor pattern;
Forming a plurality of stripe-shaped irregularities extending parallel to each other so as to be orthogonal to the one direction on the surface of the insulator layer that is outside when bent among the first and second insulator layers ,
The plurality of stripe-shaped projections and depressions are formed of a stripe-shaped recess and a stripe-shaped projection, and the insulating layer on the outside of the stripe-shaped recess has the thickness on the outside of the stripe-shaped projection. A method of manufacturing a printed wiring board, wherein the thickness is smaller than the thickness of the printed wiring board. Case and
A printed wiring board disposed in a bent state in the case,
The printed wiring board is
A first insulator layer;
A conductor pattern formed on the first insulator layer;
A second insulator layer formed on the first insulator layer so as to cover the conductor pattern,
A plurality of striped irregularities extending in parallel to each other so as to be orthogonal to the one direction are formed on the surface of the insulating layer which is outside in the bent state among the first and second insulating layers. Electronic equipment. The case has a movable part provided movably,
The electronic device according to claim 6, wherein the insulating layer formed with the unevenness of the printed wiring board is in contact with the movable portion.

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