JP2014160838A - Printed-wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a printed wiring board capable of preventing the printed wiring board from breaking even if a bend radius is small.SOLUTION: A method for manufacturing a printed wiring board 1 comprises: a first step S10 of forming a copper layer 23 of a wiring pattern 20 on a base film 10; a second step S20 of laminating a coverlay 30 on the base film 10 and covering the copper layer 23 with the coverlay 30 while a part of the copper layer 23 is exposed from the coverlay 30; a third step S30 of mechanically polishing at least an exposed part of the copper layer 23; and fourth steps S40 to S60 of forming a plating layer 24 on the copper layer 23 by plating the exposed part of the copper layer 23. Angles αand αbetween a polishing direction of the exposed part of the copper layer 23 and bending lines Cand Cin the third step S30 meet the following expression (1): 30[°]≤α,α≤150[°]...(1)

Description

  The present invention relates to a method of manufacturing a printed wiring board having a terminal portion and being bent with a small bending radius, and a printed wiring board.

  A technique is known in which buffing is performed on the surface of the wiring terminal portion in order to remove an oxide film, an organic substance, or the like before plating the wiring terminal portion to be fitted to the connector with another wiring board or the like. (For example, refer to Patent Document 1).

JP 2008-208400 A

  In the above technique, since the printed wiring board is also polished except for the terminal portion, many polishing scratches are also formed on the surface of the coverlay on which the wiring pattern is laminated.

  When the bending radius of the flexible printed wiring board is further reduced, there is a problem in that cracks develop from such polishing scratches at the time of bending and the flexible printed wiring board may break.

  The problem to be solved by the present invention is to provide a printed wiring board manufacturing method and a printed wiring board capable of avoiding breakage even when the bending radius is small.

  [1] A method for manufacturing a printed wiring board according to the present invention is a method for manufacturing a printed wiring board that is bent around a folding line, and includes a first step of forming a conductor layer of a wiring pattern on an insulating layer; A second step of laminating a covering layer on the insulating layer and covering the conductor layer with the covering layer while exposing a part of the conductor layer from the covering layer; and mechanically covering at least the exposed portion of the conductor layer A third step of polishing the exposed portion of the conductor layer, and a fourth step of forming a plated layer on the conductor layer by performing a plating process on the exposed portion of the conductor layer. In the step, the surface of the coating layer is mechanically polished together with the exposed portion of the conductor layer, thereby forming a plurality of polishing flaws on the surface of the coating layer, and the exposure of the conductor layer in the third step. The polishing direction of the part, and the folding line Angle (alpha) between satisfies the following equation (1), the angle (beta) between the folding line and the polishing scratches and satisfies the following formula (2).

30 [°] ≦ α ≦ 150 [°] (1)
30 [°] ≦ β ≦ 150 [°] (2)

  [2] In the above invention, the printed wiring board has a plurality of fold lines, and the polishing direction of the exposed portion of the coating layer in the third step is the above with respect to all the fold lines. You may satisfy | fill each (1) Formula.

  [3] A printed wiring board according to the present invention is a printed wiring board that is bent around a folding line, and includes an insulating layer, a wiring pattern that is formed on the insulating layer and has a terminal portion, and the insulating layer. And a coating layer that covers the wiring pattern while exposing the terminal portion, and a plurality of polishing scratches are formed on a surface of the coating layer, and between the polishing scratches and the fold line The angle (β) satisfies the following expression (3).

  30 [°] ≦ β ≦ 150 [°] (3)

  According to the present invention, when the exposed portion of the conductor layer is mechanically polished, the angle (α) between the polishing direction and the folding line is 30 [°] to 150 [°]. The polishing scratches formed on the coating layer are also inclined at an angle of 30 [°] to 150 [°] with respect to the folding line. For this reason, when the printed wiring board is bent around the fold line, it is possible to suppress cracks from starting from polishing scratches and to avoid breakage of the printed wiring board even if the bending radius is small. Can do.

  Further, according to the present invention, the angle (β) between the polishing flaw on the coating layer and the fold line is 30 [°] to 150 [°], so the printed wiring board is centered on the fold line. When the wire is bent, it is possible to suppress the crack from starting from a polishing scratch, and to avoid the breakage of the printed wiring board even if the bending radius is small.

FIG. 1 is a plan view showing a printed wiring board according to an embodiment of the present invention. 2A is a cross-sectional view taken along line IIA-IIA in FIG. 1, and FIG. 2B is an enlarged view of IIB in FIG. 3A is a cross-sectional view taken along the line IIIA-IIIA in FIG. 1, and FIG. 3B is an enlarged view of the IIIB portion in FIG. 4A is an enlarged view of the IVA portion of FIG. 1, and FIG. 4B is an enlarged view of the IVB portion of FIG. 5 (a) and 5 (b) are enlarged views of the cover lay having polishing scratches parallel to the folding line, and FIG. 5 (a) is a view before the printed wiring board is bent. (B) is the figure after bending a printed wiring board. FIG. 6 is an enlarged view of the surface of the coverlay in a state where the printed wiring board is bent in the embodiment of the present invention, and corresponds to FIG. FIG. 7 is a flowchart showing a method for manufacturing a printed wiring board according to the embodiment of the present invention. 8A to 8D are side views showing the printed wiring board in each step of FIG. 7, FIG. 8A is a view showing step S10 of FIG. 7, and FIG. ) Is a diagram showing step S20 in FIG. 7, FIG. 8C is a diagram showing step S30 in FIG. 7, and FIG. 8D is a diagram showing step S60 in FIG. FIG. 9 is a plan view of a sample in Example 1. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 is a plan view showing a printed wiring board according to the present embodiment, FIG. 2A is a cross-sectional view taken along line IIA-IIA in FIG. 1, and FIG. 2B is an enlarged view of IIB in FIG. 3A is a cross-sectional view taken along the line IIIA-IIIA in FIG. 1, FIG. 3B is an enlarged view of the portion IIIB in FIG. 3A, and FIG. 4A is the view in FIG. FIG. 4B is an enlarged view of the IVA portion of FIG. 1B.

  The printed wiring board 1 in the present embodiment is incorporated in an electronic device such as a mobile phone, a PDA (Personal Digital Assistant), a smartphone, a notebook computer, a tablet information terminal, a digital camera, a digital video camera, and a digital audio camera. Flexible printed wiring board (FPC). As shown in FIGS. 1 to 3, the printed wiring board 1 includes a base film 10, a wiring pattern 20, and a coverlay 30, and has an L shape as a whole. The planar shape of the printed wiring board is not particularly limited to this, and an arbitrary shape can be selected.

  The base film 10 is a flexible insulating film made of, for example, polyimide (PI). The base film 10 may be made of, for example, liquid crystal polymer (LCP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyester (PE), or aramid. The base film 10 in the present embodiment corresponds to an example of an insulating layer in the present invention.

  A plurality of wiring patterns 20 are formed on the base film 10. In the present embodiment, as shown in FIG. 1, a plurality of wiring patterns 20 are arranged in parallel at equal intervals, and extend in an L shape on the base film 10. The shape and arrangement of the wiring pattern 20 are not particularly limited. Moreover, a wiring pattern may be formed on both surfaces of the base film 10, or a via hole or the like may be included in the wiring pattern.

  Terminal portions 22 are provided at both ends of the wiring pattern 20, respectively. For example, a connector provided on another printed wiring board or a cable is connected to the terminal portion 22, and the printed wiring board 1 is connected to an external electronic circuit via the terminal portion 22. The position where the terminal portion is formed is not limited to the end portion of the wiring pattern, and an arbitrary position can be selected in the wiring pattern. Further, the number of terminal portions in the wiring pattern is not particularly limited.

  In the wiring pattern 20, a portion 21 (hereinafter simply referred to as a wiring portion 21) other than the terminal portion 22 is formed, for example, by etching a copper foil laminated on the base film 10 into a predetermined shape. As shown to (a), it is comprised only with the copper layer 23. FIG. On the other hand, the terminal portion 22 of the wiring pattern 20 has a copper layer 23 extending from the wiring portion 21 and plating formed on the surface of the copper layer 23 by electrolytic plating as shown in FIG. And a layer 24.

  The plating layer 24 has a nickel (Ni) layer 241 as a base and a gold (Au) layer 242 formed on the surface of the nickel layer 241 as shown in FIG. ing. The nickel layer 241 functions as a barrier layer for suppressing the diffusion of the gold layer 242 into the copper layer 23. The configuration of the plating layer 24 is not particularly limited to the above. For example, the gold layer 242 may be formed directly on the copper layer 23 by omitting the nickel layer. Further, the plating layer 24 may be formed by an electroless plating process.

  As shown in FIG. 3A, the coverlay 30 has a resin layer 31 for protecting the wiring portion 21 of the wiring pattern 20 and an adhesive layer 32 for bonding the resin layer 31 to the base film 10. 1 and is laminated on the base film 10 so as to cover the wiring part 21 of the wiring pattern 20. On the other hand, as shown in the figure, the terminal portion 22 of the wiring pattern 20 is exposed from the coverlay 30. The coverlay 30 in the present embodiment corresponds to an example of a coating layer in the present invention.

  The resin layer 31 of the cover lay 30 is a flexible insulating base made of polyimide (PI), for example. The resin layer 31 may be made of, for example, liquid crystal polymer (LCP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyester (PE), or aramid.

  On the other hand, the adhesive layer 32 of the coverlay 30 is made of, for example, an epoxy adhesive or an acrylic adhesive. When the base film 10 is made of liquid crystal polymer (LCP) and the resin layer 31 of the cover lay 30 is also made of liquid crystal polymer (LCP), these can be attached to each other by thermal fusion. The adhesive layer 32 becomes unnecessary.

  In addition, you may comprise this coverlay 30 with the dry film which consists of photosensitive coverlay materials using polyester, an epoxy, an acryl, a polyimide, a polyurethane etc., for example. Alternatively, the coverlay 30 may be formed by screen-printing a coverlay ink based on polyimide or epoxy or a liquid photosensitive coverlay material on the base film 10.

As shown in FIG. 1, the printed wiring board 1 according to the present embodiment is bent with a bending radius of 0.3 mm or less around the first bending line C ₁ and the second bending line C ₁ , for example. ₂ is assembled in an electronic device in a state of being bent at a bending radius of 0.3 [mm] or less. Incidentally, the printed wiring board 1 of the present embodiment is not incorporated into the movable part of the electronic device that is repeatedly bent, but is permanently incorporated into the electronic device in a state of being bent (plastically deformed) with a minimum bending radius. It is. For this reason, the printed wiring board 1 of this embodiment is required to have toughness with respect to a minimum bending radius rather than bending durability. The first and second fold lines C ₁ and C ₂ are both imaginary straight lines. Further, the bending position and the bending radius of the printed wiring board are merely examples, and are not particularly limited thereto.

  By the way, in this embodiment, before forming the plating layer 24 of the terminal part 22, in order to remove foreign substances, such as an oxide and organic substance which exist on the copper layer 23, as mentioned later, A buffing process is performed on the surface.

  In this buffing treatment, the surface 311 of the resin layer 31 of the cover lay 30 is also exposed to the buffing. For this reason, as shown in FIG. 3B, a large number of polishing scratches 312 having a depth of 1 [μm] or more are formed on the surface 311 of the resin layer 31. These polishing scratches 312 are arranged on the cover lay 30 so as to satisfy the following expressions (4) and (5), as shown in FIGS. 4 (a) and 4 (b).

30 [°] ≦ β ₁ ≦ 150 [°] (4)
30 [°] ≦ β ₂ ≦ 150 [°] (5)

However, in the above equation (4), β ₁ is the angle of the polishing flaw 312 with respect to the first folding line C ₁ , and in the above equation (5), β ₂ is relative to the second folding line C ₂ . This is the angle of the polishing flaw 312. 4A and 4B are schematic diagrams for explaining the orientation of the polishing scratches 312. In practice, the length, width, interval, etc. of the polishing scratches 312 are random. .

  5 (a) and 5 (b) are enlarged views of the cover lay having polishing scratches parallel to the fold line, and FIG. 6 is an enlarged view of the surface of the cover lay in a state where the printed wiring board is bent in the present embodiment. FIG.

When folding the printed wiring board which is formed parallel to the polishing scratches 312 fold line C ₁ (see FIG. 5 (a)), since the scratches 312 in coverlay 30 portions formed is thinner , Stress concentrates on the portion, and the polishing scratch 312 is torn. Then, as shown in FIG. 5 (b), tear 313 progress from the scratches 312, propagates to scratches 312 next bending line C ₁ in the vicinity of the scratches 312 to each other one after another led to large cracks As a result, the printed wiring board may break.

On the other hand, in the present embodiment, the polishing scratches 312 are formed on the cover lay 30 so as to satisfy the above expressions (4) and (5), whereas the cracks associated with the bending of the printed wiring board 1 since 313 is not formed only in the vicinity of the fold line C _1, as shown in FIG. 6, the number of scratches 312 connected via a tear 313 is significantly reduced. For this reason, it can suppress that a crack progresses from a grinding | polishing damage | wound, and even if a bending radius is small, the fracture | rupture of a printed wiring board can be avoided.

  Below, the manufacturing method of the printed wiring board in this embodiment is demonstrated, referring FIG.7 and FIG.8.

  FIG. 7 is a flowchart showing a method for manufacturing a printed wiring board in the present embodiment, and FIGS. 8A to 8D are side views showing the printed wiring board in each step of FIG. 8A to 8D are side views of the printed wiring board 1 viewed from the direction A in FIG.

  First, in step S10 of FIG. 7, as shown in FIG. 8A, the wiring pattern 20 is formed on the base film 10 by the subtractive method. Specifically, after forming a resist pattern on a copper foil of a copper clad laminate using a mask having a shape corresponding to the wiring pattern 20, an iron chloride etchant, a copper chloride etchant, an alkali etchant, or the like is used. Etching is performed on the copper foil. Thereby, the wiring part 21 of the wiring pattern 20 is formed on the base film 10. In addition, about the terminal part 22, only the copper layer 23 is formed in this step S10. The copper layer 23 in the present embodiment corresponds to an example of a conductor layer in the present invention.

  The method for forming the wiring pattern 20 is not particularly limited to the above. For example, the wiring pattern may be formed by plating as in the semi-additive method. Alternatively, a conductive paste such as silver paste or copper paste may be formed by screen printing on the base film.

  Next, in step S20 of FIG. 7, as shown in FIG. 8 (b), the cover lay 30 is laminated on the base film 10, and these are heated and pressed by hot pressing, whereby the cover lay 30 is formed on the base film 10. Paste to. At this time, the wiring portion 21 of the wiring pattern 20 is entirely covered with the cover lay 30, but the copper layer 23 in the terminal portion 22 of the wiring pattern 20 is exposed from the cover lay 30.

  Next, in step S30 of FIG. 7, as shown in FIG. 8C, the baffle 40 of the buffing machine is moved relative to the printed wiring board while rotating, and the terminal portion 22 of the wiring pattern 20 is moved. By polishing the surface of the copper layer 23, foreign substances such as oxides and organic substances existing on the copper layer 23 are removed. In this buffing treatment, not only the terminal portion 22 but also the surface 311 of the resin portion 31 of the cover lay 30 is polished by the buffing machine 40 of the buffing machine, and the surface 311 of the resin layer 31 has a depth of 1 [μm] or more. A large number of polishing scratches (see FIG. 3B) having a thickness are formed.

  In this embodiment, in this step S30, the buffing process is performed so that the buffing direction satisfies the following expressions (6) and (7).

30 [°] ≦ α ₁ ≦ 150 [°] (6)
30 [°] ≦ α ₂ ≦ 150 [°] (7)

However, in the above equation (6), α ₁ is an angle of the buffing direction (reference symbol L ₁ in FIG. ₁ ) with respect to the first fold line C _{1. In} the above equation (7), α ₂ is This is the angle of the buffing direction (reference numeral L ₂ in FIG. 1) with respect to the second fold line C ₂ (see FIG. 1 for both). In addition, the “buffing direction” in the present embodiment is a direction in which the rotating baffle 40 advances (or retreats) relative to the printed wiring board 1 as shown in FIG. This corresponds to an example of the polishing direction in the invention.

A number of polishing flaws 312 formed on the surface 311 of the cover lay 30 by this buffing are arranged substantially parallel to the buffing direction and arranged in parallel to each other, and the folding lines C ₁ , angle beta ₁ of scratches 312 for C _2, beta ₂ meets the above (4) and (5).

The baffle 40 used in step S30 is configured by winding a cloth with an abrasive uniformly attached around a roll. Examples of the abrasive include ceramic fine particles such as aluminum oxide (Al ₂ O ₃ ), diamond fine particles, and the like. Examples of the cloth to which the abrasive is attached include nylon cloth and polypropylene cloth.

  Next, in step S <b> 40 of FIG. 7, pretreatment is performed on the copper layer 23 in the terminal portion 22 of the wiring pattern 20. Specifically, first, an oily substance on the surface of the copper layer 23 is removed by performing a degreasing cleaning process on the copper layer 23 of the terminal portion 22. Next, the oxide film on the copper layer 23 is removed by performing an acid treatment on the copper layer 23 of the terminal portion 22. In addition, the content of the pre-processing in this step S40 is only an example, and is not particularly limited to this.

  Next, in step S50 of FIG. 7, a nickel layer 241 (see FIG. 2B) is formed on the surface of the copper layer 23 of the terminal portion 22 by electrolytic nickel plating. Next, in step S60 of FIG. 7, a gold layer 242 (see FIG. 2B) is formed on the surface of the nickel layer 241 by electrolytic gold plating. As a result, as shown in FIG. 8D, the plating layer 24 is formed on the copper layer 23, and the terminal portion 22 is completed.

  Incidentally, if the copper layer 23 is plated in step S50 without polishing the surface of the copper layer 23 of the terminal portion 22 in step S30, the interface between the copper layer 23 and the plating layer 24 will be removed. Adhesion may be reduced. For this reason, the contact resistance in the terminal part 22 becomes high, and the friction resistance of the terminal part 22 with respect to the repetition of connector insertion / extraction falls.

As described above, in the present embodiment, since the buffing direction in step S30 satisfies the above expressions (6) and (7), the polishing flaw 312 is described above with respect to the folding lines C ₁ and C ₂ . Are inclined by the angles β ₁ and β ₂ . For this reason, when the printed wiring board 1 is bent around the fold lines C ₁ and C ₂ , it is possible to suppress the cracks from starting from the polishing scratches 312, and even if the bending radius is small, the printed wiring The breakage of the plate can be avoided.

  Note that step S10 in FIG. 7 in the present embodiment corresponds to an example of the first process in the present invention, and step S20 in FIG. 7 in the present embodiment corresponds to an example of the second process in the present invention. Step S30 in FIG. 7 in the embodiment corresponds to an example of the third step in the present invention, and steps S40 to S60 in FIG. 7 in the present embodiment correspond to an example in the fourth step in the present invention.

  The embodiment described above is described for facilitating the 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.

  Below, the effect of the present invention was confirmed by examples and comparative examples that further embody the present invention. The following examples and comparative examples are for confirming the effect of suppressing breakage of the printed wiring board in the above-described embodiment.

<Example 1>
In Example 1, ten printed wiring boards having a straight shape as shown in FIG. 9 were produced as samples. FIG. 9 is a plan view of a sample in Example 1. In FIG. 9, the same code | symbol is attached | subjected about the part which is the same structure as the printed wiring board in the above-mentioned embodiment.

Specifically, in Example 1, first, a copper foil having a thickness of 18 [μm] is laminated on a polyimide film (base film) having a thickness of 25 [μm], and S _{1 in} FIG. ], A strip-shaped single-sided copper-clad laminate with w ₁ of 10 [mm] is prepared, a resist pattern is formed on the copper foil, and then the copper foil is etched to give 0.1 Thirty linear wiring patterns arranged in parallel at intervals of [mm] were formed. The width of each wiring pattern was 0.1 [mm]. Further, as shown in the figure, set the fold line C ₃ only in one place in the longitudinal center portion of the printed circuit board.

  Next, a coverlay in which a thermosetting adhesive with a thickness of 30 [μm] is applied to a polyimide film with a thickness of 12.5 [μm] is exposed so that both end portions of the wiring pattern are exposed at 3 [mm], respectively. The cover lay was bonded to the base film by laminating on the base film and curing with a hot press at 165 ° C. for 70 minutes.

Next, the entire surface of the printed wiring board was buffed. In this case, in Example 1, (it was perpendicular to buffing direction relative i.e. fold line C ₃₎ of fold line C ₃ the angle α of the buffing direction with respect to the 90 [°].

  In this buffing treatment, a baffle in which aluminum oxide having a particle size of # 1000 was attached to a nylon cloth was used, the rotation speed of the baffle was 1450 [rpm], and the feed rate was 1.65 [m / min]. Furthermore, the pressing force of the bafrol was set so that a foot mark of 1.5 to 2.0 [mm] was formed.

Ten of a printed wiring board fabricated as described above, the diameter 0.6 [mm] of the mandrel (bending radius: 0.3 [mm]) was used to manually respectively about the folding lines _{C 3} 1 After bending 10 times, the surface of the coverlay was visually observed using a microscope.

In the sample of Example 1, as shown in Table 1, no crack was generated on the surface of the coverlay even when the printed wiring board was bent 10 times. In the column of “Presence / absence of breakage” in Table 1, “◯” indicates that the printed wiring board was not broken, and “x” indicates that the printed wiring board was broken.

<Example 2>
In Example 2, except that the angle of the buffing direction α with respect to bending line C ₃ and 60 [°], and the same samples as in Example 1 was produced 10 pieces.

For a sample of Example 2 also, under the same conditions as in Example 1, after bending 10 times each around a folding line C ₃ to 10 of the printed wiring board, the surface of the coverlay of the printed circuit board Was observed.

  As shown in Table 1, in the sample of Example 2, no crack was generated on the surface of the coverlay even when the printed wiring board was bent 10 times.

<Example 3>
In Example 3, except that the angle of the buffing direction α with respect to bending line C ₃ and 45 [°], and the same samples as in Example 1 was produced 10 pieces.

For a sample of Example 3 also, under the same conditions as in Example 1, after bending 10 times each around a folding line C ₃ to 10 of the printed wiring board, the surface of the coverlay of the printed circuit board Was observed.

  As shown in Table 1, even in the sample of Example 3, no crack was generated on the surface of the coverlay even when the printed wiring board was bent 10 times.

<Example 4>
In Example 4, except that the angle of the buffing direction α with respect to bending line C ₃ and 30 [°], and the same samples as in Example 1 was produced 10 pieces.

For a sample of Example 4 also, under the same conditions as in Example 1, after bending 10 times each around a folding line C ₃ to 10 of the printed wiring board, the surface of the coverlay of the printed circuit board Was observed.

  As shown in Table 1, even in the sample of Example 4, no crack was generated on the surface of the coverlay even when the printed wiring board was bent 10 times.

<Comparative Example 1>
In Comparative Example 1, except that the angle of the buffing direction α with respect to bending line C ₃ and 15 [°], and the same samples as in Example 1 was produced 10 pieces.

For a sample of the Comparative Example 1, under the same conditions as in Example 1, after bending 10 times each around a folding line C ₃ to 10 of the printed wiring board, the surface of the coverlay of the printed circuit board Was observed.

  As shown in Table 1, in the sample of Comparative Example 1, when the printed wiring board was bent seven times, the resin layer and the adhesive layer of the coverlay were broken and the wiring pattern was exposed.

<Comparative example 2>
In Comparative Example 2, except that the angle of the buffing direction α with respect to bending line C ₃ and 10 [°], and the same samples as in Example 1 was produced 10 pieces.

For a sample of Comparative Example 2 also, under the same conditions as in Example 1, after bending 10 times each around a folding line C ₃ to 10 of the printed wiring board, the surface of the coverlay of the printed circuit board Was observed.

  As shown in Table 1, in the sample of Comparative Example 2, when the printed wiring board was bent five times, the resin layer and the adhesive layer of the coverlay were broken and the wiring pattern was exposed.

<Comparative Example 3>
In Comparative Example 3, the angle of the buffing direction α with respect to fold line C ₃ was 0 [°] Except (i.e., in the parallel buffing direction against bending line C ₃₎ that, similarly to Example 1 Ten samples were prepared.

For a sample of Comparative Example 3 also, under the same conditions as in Example 1, after bending 10 times each around a folding line C ₃ to 10 of the printed wiring board, the surface of the coverlay of the printed circuit board Was observed.

  As shown in Table 1, in the sample of Comparative Example 3, when the printed wiring board was bent three times, the resin layer and the adhesive layer of the coverlay were broken and the wiring pattern was exposed.

As described above, in Examples 1 to 4 the angle α of the buffing direction is 30 [°] or more with respect to fold line C _3, it was possible to suppress the occurrence of cracks due to bending. In contrast, in Comparative Examples 1 to 3 of the angle α of the buffing direction is less than 30 [°] with respect to fold line C _3, cracks were generated in the coverlay with the folding.

DESCRIPTION OF SYMBOLS 1 ... Printed wiring board 10 ... Base film 20 ... Wiring pattern 21 ... Wiring part 22 ... Terminal part 23 ... Copper layer 24 ... Plating layer 241 ... Nickel layer 242 ... Gold layer 30 ... Coverlay 31 ... Resin layer 311 ... Surface 312 ... Polishing scratch 313 ... tear 32 ... adhesive layer 40 ... buffol C ₁ , C ₂ ... fold line α ₁ , α ₂ ... angle formed by fold line and polishing direction β ₁ , β ₂ ... angle L ₁ formed by fold line and polishing scratch , L ₂ ... A straight line parallel to the buffing direction

Claims (1)

A printed wiring board that is bent around a fold line,
An insulating layer;
A wiring pattern formed on the insulating layer and having a terminal portion;
A coating layer that is laminated on the insulating layer and covers the wiring pattern while exposing the terminal portion;
A plurality of polishing flaws are formed on the surface of the coating layer,
An angle (β) between the polishing flaw and the bending line satisfies the following expression (3).
30 [°] ≦ β ≦ 150 [°] (3)

Images