JP2010129803A - Wiring circuit board and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring circuit board preventing occurrences of ion migration and corrosion, and reducing costs, and also to provide a method for manufacturing the wiring circuit board. <P>SOLUTION: A predetermined conductor pattern (wiring pattern) 2 consisting of copper is formed on an insulating layer 1 including a base resin layer 1a and a base adhesive layer 1b. A coverlay film 4 is stuck on a predetermined region on the insulating layer 1 by using a coverlay adhesive layer 3. A plated layer 5 is formed so as to cover a part of the conductor pattern 2 in a region where the coverlay film 4 is not stuck on the insulating layer 1. An end face 5E of the plated layer 5 positioned on the conductor pattern 2 is covered by the coverlay adhesive layer 3 protruding from between the insulating layer 1 and the coverlay film 4. A region 5F of a predetermined width from the end face 5E on a surface of the plated layer 5 is covered with the coverlay adhesive layer 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a printed circuit board and a method for manufacturing the same.

  In a printed circuit board such as a flexible printed circuit board, a conductor layer (conductor pattern) such as a copper foil having a predetermined pattern is formed on one side or both sides of an insulation layer such as polyimide, and the conductor layer is covered with the conductor layer. A coverlay film is formed on the surface.

A coverlay film is adhere | attached via the adhesive bond layer on the area | region except the terminal part of a conductor pattern, and a plating layer is formed in the surface of the terminal part of a conductor pattern (patent documents 1-3). Thereby, corrosion of the terminal portion is prevented.
JP 7-38239 A JP-A-9-92979 JP 2000-219854 A

  However, metal ion migration may occur due to the use of the printed circuit board. As a result, a short circuit occurs between the conductor patterns. Here, ion migration refers to a phenomenon in which metal ions move using moisture as a medium while an electric field is generated. In addition, the conductor pattern portion in the vicinity of the terminal portion may corrode due to the penetration of moisture or the like. Thereby, the connectivity between the electronic component mounted on the terminal portion and the conductor pattern is lowered.

  In the flexible printed wiring board of Patent Document 1, screen printing is performed at the boundary between the coverlay film and the circuit conductor in order to prevent corrosion of the coverlay film and the circuit conductor. In this case, manufacturing equipment and paint for screen printing are required. Thereby, the manufacturing cost is increased.

  An object of the present invention is to provide a printed circuit board which can prevent the occurrence of ion migration and corrosion and can be reduced in cost, and a method for manufacturing the same.

  (1) A printed circuit board according to a first invention includes a first insulating layer, a conductor layer formed on the first insulating layer and including a metal having a predetermined pattern, and a partial region of the conductor layer. A second insulating layer formed on the first insulating layer via an adhesive layer so as to cover other regions of the conductor layer except for, and a plating layer formed in a partial region of the conductor layer The adhesive layer protrudes from the other region so as to cover a part of the plating layer on the partial region.

  In the printed circuit board according to the present invention, other regions except for a partial region of the conductor layer are covered with the second insulating layer via the adhesive layer. Moreover, a partial region of the conductor layer is covered with the plating layer.

  In this case, a part of the plating layer formed in the partial region of the conductor layer is covered with the adhesive layer protruding from the other region of the conductive layer. This prevents metal ions eluted from the conductor layer from moving outside through the interface between the plating layer and the adhesive layer. Therefore, the occurrence of ion migration is prevented. Further, the external atmosphere is prevented from reaching the surface of the conductor layer through the interface between the plating layer and the adhesive layer. Thereby, corrosion of the conductor layer is prevented. As a result, the reliability of the printed circuit board is improved.

  Furthermore, since a part of the plating layer is covered with the adhesive layer without newly preparing other materials, the cost of the printed circuit board can be reduced.

  (2) The plating layer has an end surface on the conductor layer, and the adhesive layer protruding from the other region has a vertical cross section perpendicular to the end surface of the plating layer, and the surface of the plating layer including the end surface is formed by the adhesive layer. It may be coated with a length of 5 μm or more and 200 μm or less.

  Here, said length is an average length in the edge part of an adhesive bond layer.

  Thereby, the length of the interface between the plating layer and the adhesive layer can be sufficiently secured, and the exposed area of the plating layer is prevented from becoming excessively small. Therefore, the occurrence of ion migration and the occurrence of corrosion of the conductor layer are sufficiently prevented while ensuring the connectivity between the plating layer and the electronic component. As a result, the reliability of the printed circuit board is sufficiently improved.

  (3) In the longitudinal section perpendicular to the end face of the plating layer, the surface of the plating layer including the end face may be covered with an adhesive layer for a length of 10 μm or more and 50 μm or less.

  Thereby, the length of the interface between the plating layer and the adhesive layer can be more sufficiently secured, and the reduction of the exposed area of the plating layer can be minimized. Therefore, the occurrence of ion migration and the occurrence of corrosion of the conductor layer are more sufficiently prevented while the connectivity between the plating layer and the electronic component is sufficiently ensured. As a result, the reliability of the printed circuit board is further improved.

  (4) A method for manufacturing a printed circuit board according to a second invention includes a step of forming a conductor layer including a metal having a predetermined pattern on the first insulating layer, and a conductor except for a partial region of the conductor layer. Forming a second insulating layer on the first insulating layer via an adhesive layer so as to cover other regions of the layer, and pressurizing the first insulating layer and the second insulating layer A step of bonding the first insulating layer and the second insulating layer, a step of forming a plating layer in a partial region of the conductor layer, a first insulating layer and a second insulating layer after forming the plating layer; And a step of pressurizing.

  In the method for manufacturing a printed circuit board according to the present invention, a conductor layer including a metal having a predetermined pattern is formed on the first insulating layer, and other areas of the conductor layer are removed except for a part of the conductor layer. A second insulating layer is formed on the first insulating layer so as to cover the adhesive layer. Thereafter, the first insulating layer and the second insulating layer are pressurized, the first insulating layer and the second insulating layer are bonded together, and a plating layer is formed in a partial region of the conductor layer.

  Furthermore, after the plating layer is formed, the first insulating layer and the second insulating layer are pressurized. As a result, the adhesive layer between the first insulating layer and the second insulating layer protrudes from the other region of the conductor layer.

  In this case, a part of the plating layer formed in the partial region of the conductor layer is covered with the adhesive layer protruding from the other region of the conductive layer. This prevents metal ions eluted from the conductor layer from moving outside through the interface between the plating layer and the adhesive layer. Therefore, the occurrence of ion migration is prevented. Further, the external atmosphere is prevented from reaching the surface of the conductor layer through the interface between the plating layer and the adhesive layer. Thereby, corrosion of the conductor layer is prevented. As a result, the reliability of the printed circuit board is improved.

  Furthermore, since a part of the plating layer is covered with the adhesive layer without newly preparing other materials and equipment, an increase in the material cost of the printed circuit board is suppressed. Moreover, a part of the plating layer is covered with the adhesive layer by pressurization. Thereby, it is not necessary to prepare other facilities. As a result, increases in material cost and manufacturing cost are sufficiently suppressed.

  (5) In the bonding step, the first insulating layer and the second insulating layer are pressurized for the first period, and in the step of pressing the first insulating layer and the second insulating layer after forming the plating layer The first insulating layer and the second insulating layer are pressurized during the second period, and the first period may be shorter than the second period.

  In this case, since the first period is shorter than the second period, it is possible to prevent the adhesive layer from being completely cured in the step of bonding the first insulating layer and the second insulating layer. The adhesive layer can be prevented from excessively protruding from between the first insulating layer and the second insulating layer before the plating layer is formed. In addition, after the plating layer is formed, the adhesive layer can be easily protruded from a portion of the conductor layer from between the first insulating layer and the second insulating layer, and the adhesive layer is completely cured. Can be made. Thereby, a part of plating layer can be reliably coat | covered with an adhesive bond layer.

  In the printed circuit board according to the present invention, other regions except for a partial region of the conductor layer are covered with the second insulating layer via the adhesive layer. Moreover, a partial region of the conductor layer is covered with the plating layer.

  In this case, a part of the plating layer formed in the partial region of the conductor layer is covered with the adhesive layer protruding from the other region of the conductive layer. This prevents metal ions eluted from the conductor layer from moving outside through the interface between the plating layer and the adhesive layer. Therefore, the occurrence of ion migration is prevented. Further, the external atmosphere is prevented from reaching the surface of the conductor layer through the interface between the plating layer and the adhesive layer. Thereby, corrosion of the conductor layer is prevented. As a result, the reliability of the printed circuit board is improved.

  Furthermore, since a part of the plating layer is covered with the adhesive layer without newly preparing other materials, the cost of the printed circuit board can be reduced.

  Hereinafter, a printed circuit board and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to the drawings. Hereinafter, a flexible printed circuit board will be described as an example of the printed circuit board.

(1) Configuration of Wiring Circuit Board FIG. 1 is an external perspective view of a flexible wiring circuit board 100 according to an embodiment of the present invention. 2A is a schematic top view of the flexible printed circuit board 100 of FIG. 1, and FIG. 2B is a partially enlarged sectional view taken along line AA of FIG. 2A. In FIG. 2A, in order to identify each of a plurality of components of the flexible printed circuit board 100 to be described later, the components visible from the outside are hatched.

  As shown in FIGS. 1 and 2, a flexible printed circuit board 100 according to the present embodiment includes an insulating layer 1, a conductor pattern 2, a coverlay adhesive layer 3, a coverlay film 4, and a plating layer 5. The insulating layer 1 includes a base resin layer 1a and a base adhesive layer 1b. The structure of the flexible printed circuit board 100 will be described in detail.

  A predetermined conductor pattern (wiring pattern) 2 made of copper is formed on an insulating layer 1 made of a base resin layer 1a and a base adhesive layer 1b.

  As shown in FIGS. 2A and 2B, a coverlay film 4 is bonded to a predetermined region on the insulating layer 1 using a coverlay adhesive layer 3. Thereby, a part of the conductor pattern 2 is covered with the coverlay adhesive layer 3 and the coverlay film 4.

  Further, in the region on the insulating layer 1 where the cover lay film 4 is not bonded, the plating layer 5 is formed so as to cover a part of the conductor pattern 2. A portion of the conductor pattern 2 on which the plating layer 5 is formed constitutes a terminal portion T in the flexible printed circuit board 100. An electronic component (not shown) is mounted on the terminal portion T.

  Here, as shown in FIGS. 2A and 2B, in the conductor pattern 2, a gap G is formed between the portion where the plating layer 5 is formed and the portion covered with the coverlay film 4. The

  In flexible printed circuit board 100 according to the present embodiment, gap G of conductor pattern 2, part of insulating layer 1 located around gap G, and part of plating layer 5 located around gap G Is covered with the coverlay adhesive layer 3.

  As a result, the end surface 5E of the plating layer 5 is covered with the coverlay adhesive layer 3 as indicated by a thick line in FIG. A region 5 </ b> F having a predetermined width from the end surface 5 </ b> E on the surface of the plating layer 5 is covered with the coverlay adhesive layer 3. In the following description, the region 5F on the surface of the plating layer 5 covered with the coverlay adhesive layer 3 is referred to as a surface coating region 5F.

  Here, the thickness of the plating layer 5 is d1, and the width of the surface coating region 5F is d2. In this case, in the longitudinal section of the flexible printed circuit board 100, the plating layer 5 is covered with the coverlay adhesive layer 3 for the total length of the thickness d1 and the width d2. In the following description, the total value of the thickness d1 and the width d2 is referred to as a coating length.

(2) Effect Based on Configuration of Printed Circuit Board In flexible printed circuit board 100 according to the present embodiment, end surface 5E and surface covering region 5F of plating layer 5 are covered with coverlay adhesive layer 3.

  This prevents metal ions (copper ions) eluted from the surface of the conductor pattern 2 from moving outside through the interface between the plating layer 5 and the coverlay adhesive layer 3. Therefore, the occurrence of ion migration is prevented even in a high temperature and high humidity atmosphere. Further, even in a high-temperature and high-humidity atmosphere, an external atmosphere (moisture or the like) is prevented from reaching the surface of the conductor pattern 2 through the interface between the plating layer 5 and the coverlay adhesive layer 3. Thereby, corrosion of the conductor pattern 2 is prevented. Therefore, a decrease in connectivity between the electronic component (not shown) mounted on the terminal portion T and the conductor pattern 2 is prevented. As a result, the reliability of the flexible printed circuit board 100 is improved.

  Furthermore, it is not necessary to use another material for covering a part of the plating layer 5. Therefore, the cost of the flexible printed circuit board 100 can be reduced.

  The coating length is preferably set to 5 μm or more and 200 μm or less. Here, in the present embodiment, the covering length refers to the average length at the edge of the coverlay adhesive layer 3. Thereby, the length of the interface between the plating layer 5 and the coverlay adhesive layer 3 can be sufficiently secured, and the exposed area of the plating layer 5 is prevented from becoming excessively small. Therefore, the region of the terminal portion T is sufficiently secured, and the occurrence of ion migration and the corrosion of the conductor pattern 2 are sufficiently prevented while the connectivity between the plating layer 5 and the electronic component is secured. As a result, the reliability of the flexible printed circuit board 100 is sufficiently improved.

  More preferably, the coating length is set to 10 μm or more and 50 μm or less. Thereby, the length of the interface between the plating layer 5 and the coverlay adhesive layer 3 can be secured more sufficiently, and the reduction of the exposed area of the plating layer 5 can be minimized. Therefore, the region of the terminal portion T is more sufficiently secured, and the occurrence of ion migration and the corrosion of the conductor pattern 2 are more sufficiently prevented while the connectivity between the plating layer 5 and the electronic component is sufficiently secured. As a result, the reliability of the flexible printed circuit board 100 is more sufficiently improved.

(3) Manufacturing method of wiring circuit board Subsequently, the manufacturing method of the flexible wiring circuit board 100 is demonstrated in detail. 3 and 4 are schematic process cross-sectional views showing a method for manufacturing the flexible printed circuit board 100 of FIG.

  First, as shown in FIG. 3A, a base film is prepared in which a copper foil 2X is bonded to one surface of a base resin layer 1a made of an insulator film with a base adhesive layer 1b interposed therebetween. Then, a photoresist is applied on one surface of the exposed copper foil 2X, and an exposure process and a development process are performed using a photomask. Thereby, an etching resist having a predetermined pattern is obtained. Thereafter, the copper foil 2X is etched and the etching resist is removed to form a conductor pattern 2 (wiring pattern) made of copper.

  As described above, in the present embodiment, the insulating layer 1 is constituted by the base resin layer 1a and the base adhesive layer 1b.

  As the base resin layer 1a, for example, an insulating film such as a polyimide film or a polyester film is used. The thickness of the base resin layer 1a is preferably 10 μm or more and 40 μm or less.

  Further, as the base adhesive layer 1b, for example, an epoxy resin adhesive, a phenol resin adhesive, a polyester resin adhesive, an acrylic resin adhesive, an adhesive made of acrylonitrile butadiene rubber, or the like is used. It is done. The thickness of the base adhesive layer 1b is preferably 10 μm or more and 40 μm or less.

  The material of the conductor pattern 2 is not limited to copper, and other metals such as gold, nickel, or aluminum may be used, or an alloy such as copper alloy, solder, or aluminum alloy may be used. The thickness of the conductor pattern 2 is preferably 5 μm or more and 40 μm or less.

  In the above description, it is described that a three-layer base film composed of the base resin layer 1a, the base adhesive layer 1b, and the copper foil 2X is used. However, a two-layer base film composed of the base resin layer 1a and the copper foil 2X is used. It may be used.

  Next, a cover lay film 4 having a cover lay adhesive layer 3 previously applied on one surface is prepared. And as shown in FIG.3 (b), the coverlay film 4 is bonded together on one surface of the insulating layer 1 in which the conductor pattern 2 was formed on both sides of the coverlay adhesive layer 3 by hot press. In the following description, the hot press at this time is referred to as a first hot press. In addition, the coverlay film 4 is affixed on the area | region except the formation area (refer FIG. 4) of the terminal part T defined beforehand.

  Specifically, the insulating layer 1, the conductive pattern 2, and the coverlay adhesive layer 3 in a state where the coverlay film 4 is disposed on the insulating layer 1 on which the conductive pattern 2 is formed with the coverlay adhesive layer 3 interposed therebetween. And the laminated body which consists of coverlay film 4 is pressurized with the 1st pressure in the 1st period with the press machine heated to the 1st temperature.

At this time, the first hot press is performed so that the coverlay adhesive layer 3 is in a semi-cured state. The first temperature is set to 50 ° C. or higher and 200 ° C. or lower. The first period is set to 5 seconds or more and 10 minutes or less, and the first pressure is set to 1 kg / cm ² or more and 90 kg / cm ² or less.

  As described above, by performing the first hot press, a part of the coverlay adhesive layer 3 is pushed out from the end face 4E of the coverlay film 4 as shown in FIG.

  As the coverlay film 4, for example, an insulating film such as a polyimide film or a polyester film is used. The thickness of the coverlay film 4 is preferably 10 μm or more and 60 μm or less.

  As the coverlay adhesive layer 3, a thermosetting adhesive in which a thermosetting resin and a thermoplastic resin are mixed is used. As the thermosetting resin, for example, an epoxy resin or a phenol resin can be used. As the thermoplastic resin, for example, polyester resin, acrylic resin, acrylonitrile butadiene rubber, or the like can be used. The coverlay adhesive layer 3 preferably has a thickness of 10 μm or more and 40 μm or less.

  The coverlay film 4 having the coverlay adhesive layer 3 applied on one surface is coated by applying a thermosetting adhesive mixed with a thermosetting resin and a thermoplastic resin on one surface of the coverlay film 4. The prepared adhesive is made into a semi-cured state, and a release film is laminated on the adhesive.

  Thereafter, as shown in FIG. 4C, the plating layer 5 is formed by electrolytic plating, for example, in a region where the coverlay adhesive layer 3 in the conductor pattern 2 is not formed, that is, a region where the terminal portion T is formed.

  In the present embodiment, as the plating layer 5, a gold plating layer, a nickel-gold plating layer, a tin plating layer, a solder plating layer, a tin-copper alloy plating layer, a tin-silver alloy plating layer, or the like is used. Can do. In the present embodiment, the thickness of the plating layer 5 is not particularly limited.

  The plating layer 5 is not limited to electrolytic plating, and may be formed by electroless plating. The plating layer 5 may be formed by screen-printing solder on the formation region of the terminal portion T on the insulating layer 1 or may be formed by bringing molten solder into contact with the formation region of the terminal portion T. May be.

  Subsequently, as shown in FIG. 4 (d), the laminated body composed of the insulating layer 1, the conductor pattern 2, the coverlay adhesive layer 3 and the coverlay film 4 is subjected to hot pressing again. In the following description, the hot press after the formation of the plating layer 5 is referred to as a second hot press.

  Specifically, the above laminate is pressurized at a second pressure for a second period by a press machine heated to a second temperature.

At this time, the second hot press is performed so that the coverlay adhesive layer 3 is completely cured. It is preferable that 2nd temperature is more than 1st temperature and is set to 50 to 200 degreeC. The second period is preferably set to be not less than the first period and not less than 10 minutes and not more than 3 hours. Furthermore, the second pressure is preferably set to be equal to or higher than the first pressure and not lower than 1 kg / cm ^{2 and not} higher than 90 kg / cm ² .

  Here, the total time of the first period and the second period is preferably set to 5 seconds or more and 3 hours or less. The hot press may be performed using either a single-layer press or a multistage press.

  As described above, after the plating layer 5 is formed in a partial region of the conductor pattern 2, the second heat press is performed, so that the end face 4 </ b> E of the coverlay film 4 is formed as shown in FIG. A part of the cover lay adhesive layer 3 is extruded from. As a result, the coverlay adhesive layer 3 protrudes from the end surface 5E of the plating layer 5 onto the surface of the plating layer 5 by a width d2. As a result, as described above, the end surface 5E and the surface coating region 5F of the plating layer 5 in the longitudinal section of the flexible printed circuit board 100 are covered with the coverlay adhesive layer 3.

(4) Effects based on the printed circuit board manufacturing method In the manufacturing method described above, after the insulating layer 1 and the coverlay film 4 are bonded together by the first hot press, the exposed conductor pattern 2 is exposed. The plating layer 5 is formed, and the coverlay adhesive layer 3 is extruded from between the coverlay film 4 and the insulating layer 1 by the second hot press.

  Thereby, the end surface 5E and the surface covering region 5F of the plating layer 5 on the conductor pattern 2 are covered with the coverlay adhesive layer 3 without newly preparing other materials and equipment. Thereby, increase of material cost and manufacturing cost is fully suppressed.

  Here, in the flexible printed circuit board 100 of FIG. 4D, the length L from the end face 4E of the coverlay film 4 to the end 3E of the coverlay adhesive layer 3 covering the plating layer 5 is defined as the coverlay adhesive. Called the exposed length L of layer 3. The exposure length L is a total value of the gap G and the width of the surface coating region 5F with d2. In the present embodiment, the exposed length L refers to the average length at the edge of the coverlay adhesive layer 3.

  The exposure length L is preferably set to 5 μm or more and 400 μm or less. Thereby, the length of the interface between the plating layer 5 and the coverlay adhesive layer 3 can be sufficiently secured, and the exposed area of the plating layer 5 is prevented from becoming excessively small. Therefore, the occurrence of ion migration and the occurrence of corrosion of the conductor pattern 2 are sufficiently prevented while ensuring the connectivity between the plating layer 5 and an electronic component (not shown). As a result, the reliability of the flexible printed circuit board 100 is sufficiently improved.

  The exposure length L is more preferably set to 5 μm or more and 200 μm or less. Thereby, the length of the interface between the plating layer 5 and the coverlay adhesive layer 3 can be secured more sufficiently, and the reduction of the exposed area of the plating layer 5 can be minimized. Accordingly, the connectivity between the plating layer 5 and an electronic component (not shown) is sufficiently secured, and the occurrence of ion migration and the corrosion of the conductor pattern 2 are more sufficiently prevented. As a result, the reliability of the flexible printed circuit board 100 is more sufficiently improved.

(5) Covering State of Plating Layer with Coverlay Adhesive Layer FIG. 5 is a schematic cross-sectional view showing a covering state of the plating layer 5 with the coverlay adhesive layer 3. FIG. 5A shows the coating state of the plating layer 5 when the thickness d1 of the plating layer 5 is small. FIG. 5B shows a covering state of the plating layer 5 when the thickness d1 of the plating layer 5 is large.

  As shown in FIGS. 5A and 5B, in the flexible printed circuit board 100, the covering state of the plating layer 5 by the coverlay adhesive layer 3 changes according to the thickness d1 of the plating layer 5. The above effect can be obtained by setting the covering length (the total value of the thickness d1 and the width d2) to 5 μm or more and 200 μm or less.

(6) Correspondence between each constituent element of claims and each element of the embodiment An example of correspondence between each constituent element of the claims and each element of the embodiment will be described, but the present invention is limited to the following examples. Not.

  In the above embodiment, the flexible printed circuit board 100 is an example of a printed circuit board, the insulating layer 1 is an example of a first insulating layer, the conductive pattern 2 is an example of a conductive layer, and the coverlay adhesive Layer 3 is an example of an adhesive layer, coverlay film 4 is an example of a second insulating layer, and end surface 5E of plating layer 5 is an example of an end surface of the plating layer.

  As each constituent element in the claims, various other elements having configurations or functions described in the claims can be used.

  Hereinafter, the printed circuit board and the manufacturing method thereof in Examples 1 to 5 and the comparative example will be described.

[Example 1]
In Example 1, a base film was prepared in which a copper foil 2X was bonded to one surface of a base resin layer 1a with a base adhesive layer 1b interposed therebetween. A polyimide film was used as the base resin layer 1a, and an epoxy resin adhesive was used as the base adhesive layer 1b. The thickness of the base resin layer 1a was 25 μm, the thickness of the base adhesive layer 1b was 15 μm, and the thickness of the copper foil 2X was 35 μm.

  Then, an etching resist having a predetermined pattern was formed on one surface of the exposed copper foil 2X in the same manner as described above. Thereafter, the conductor pattern 2 made of copper was formed by etching the copper foil 2X and removing the etching resist.

  Next, a cover lay film 4 having a cover lay adhesive layer 3 coated on one side was prepared. An epoxy resin adhesive was used as the coverlay adhesive layer 3 and a polyimide film was used as the coverlay film 4.

  And the coverlay film 4 was bonded together by 1st hot press on the one surface of the insulating layer 1 in which the conductor pattern 2 was formed on both sides of the coverlay adhesive layer 3. In addition, the coverlay film 4 was affixed on the area | region except the formation area of the terminal part T defined beforehand.

In the first hot press, the first temperature was set to 150 ° C., the first period was set to 1 minute, and the first pressure was set to 40 kg / cm ² .

  Thereafter, a plating layer 5 was formed by electrolytic plating on the portion of the conductor pattern 2 where the coverlay adhesive layer 3 was not formed. The thickness of the plating layer 5 was about 0.3 μm.

Finally, a second hot press was performed on the laminate composed of the insulating layer 1, the conductor pattern 2, the coverlay adhesive layer 3 and the coverlay film 4. In the second hot press, the second temperature was set to 150 ° C., the second period was set to 1 minute, and the second pressure was set to 40 kg / cm ² .

[Example 2]
In Example 2, a flexible printed circuit board was produced in the same manner as in Example 1 except that the conditions of the first hot press and the second hot press were different.

In this example, as the conditions for the first hot press, the first temperature was set to 150 ° C., the first period was set to 1 minute, and the first pressure was set to 40 kg / cm ² . Further, as conditions for the second hot press, the second temperature was set to 150 ° C., the second period was set to 3 minutes, and the second pressure was set to 40 kg / cm ² .

[Example 3]
In Example 3, a flexible printed circuit board was produced in the same manner as in Example 1 except that the conditions of the first hot press and the second hot press were different.

In this example, as the conditions for the first hot press, the first temperature was set to 150 ° C., the first period was set to 1 minute, and the first pressure was set to 40 kg / cm ² . Further, as conditions for the second hot press, the second temperature was set to 150 ° C., the second period was set to 10 minutes, and the second pressure was set to 40 kg / cm ² .

[Example 4]
In Example 4, a flexible printed circuit board was produced in the same manner as in Example 1 except that the conditions of the first hot press and the second hot press were different.

In this example, as the conditions for the first hot press, the first temperature was set to 150 ° C., the first period was set to 1 minute, and the first pressure was set to 40 kg / cm ² . Further, as conditions for the second hot press, the second temperature was set to 150 ° C., the second period was set to 34 minutes, and the second pressure was set to 40 kg / cm ² .

[Example 5]
In Example 5, a flexible printed circuit board was produced in the same manner as in Example 1 except that the conditions of the first hot press and the second hot press were different.

In this example, as the conditions for the first hot press, the first temperature was set to 150 ° C., the first period was set to 1 minute, and the first pressure was set to 40 kg / cm ² . Further, as the conditions for the second hot press, the second temperature was set to 150 ° C., the second period was set to 120 minutes, and the second pressure was set to 40 kg / cm ² .

[Comparative example]
In the comparative example, the flexible printed circuit board is manufactured in the same manner as in Example 1 except that the first period in the first hot press is different and the second hot press is not performed after the plating layer 5 is formed. Was made. In this example, the first temperature was set to 150 ° C., the first period was set to 35 minutes, and the first pressure was set to 40 kg / cm ² .

[Evaluation]
The longitudinal section of the portion of the plating layer 5 in the flexible printed circuit boards of Examples 1 to 5 was substantially the same as that of the flexible printed circuit board 100 shown in FIG. On the other hand, the plating layer 5 was not covered with the coverlay adhesive layer 3 in the longitudinal section of the portion of the plating layer 5 in the flexible printed circuit board of the comparative example.

  In the production of the flexible printed circuit boards of Examples 1 to 5 and Comparative Example, the length of the coverlay adhesive layer 3 protruding from the end face 4E of the coverlay film 4 was measured after the first hot press. It was measured by. This length corresponds to the length of the gap G (see FIG. 4D) in the above embodiment.

  As a result, in the flexible printed circuit boards of Examples 1 to 5, the lengths of the gaps G were 29 μm, 30 μm, 30 μm, 28 μm, and 29 μm, respectively. In the flexible printed circuit board of the comparative example, the length of the gap G was 50 μm.

  Furthermore, about the completed flexible wiring circuit board of Examples 1-5, the length of the cover-lay adhesive layer 3 which protruded from the end surface 4E of the cover-lay film 4 was measured with the length measuring microscope after 2nd heat press completion. . This length corresponds to the exposure length L (see FIG. 4D) in the above embodiment.

  As a result, in the flexible printed circuit boards of Examples 1 to 5, the exposed lengths L were 32 μm, 35 μm, 41 μm, 49 μm, and 82 μm, respectively.

  The flexible printed circuit board of the comparative example was not subjected to the second measurement because the second heat press was not performed.

  Based on the measurement results, the coating length of the plating layer 5 by the coverlay adhesive layer 3 in each flexible printed circuit board was calculated. As a result, in the flexible printed circuit boards of Examples 1 to 7, the coating lengths of the plating layer 5 by the coverlay adhesive layer 3 were 3 μm, 5 μm, 11 μm, 21 μm, and 53 μm, respectively.

  On the other hand, as described above, in the comparative example, since the plating layer 5 was not covered with the coverlay adhesive layer 3, the coating length was 0 μm.

  The following corrosion tests were performed on the flexible printed circuit boards of Examples 1 to 5 and the comparative example.

  A desiccator having a volume of 12 liters was prepared, and a container containing 480 ml of 70% nitric acid was placed in the desiccator. The lid of the desiccator was closed and left for 30 minutes.

  Subsequently, in addition to the 70% nitric acid container, the flexible printed circuit boards of Examples 1 to 7 and Comparative Example were placed in the desiccator, and the desiccator lid was closed and left for 60 minutes. And the container of 70% nitric acid and the flexible wiring circuit board of Examples 1-7 and a comparative example were taken out from the desiccator.

  Next, after heating the flexible printed circuit boards of Examples 1 to 5 and the comparative example in a temperature environment of 125 ° C. for 30 minutes, each flexible printed circuit board is again placed in the desiccator, and the lid is closed. Left for a minute.

  Finally, each flexible printed circuit board was taken out from the desiccator, and the magnitude and number of corrosion occurring on the conductor pattern 2 were measured with a microscope.

  FIG. 6 is a diagram showing the exposed length L, the coating length of the plating layer 5 with the coverlay adhesive layer 3, and the corrosion test results in the flexible printed circuit boards of Examples 1 to 5 and the comparative example.

As shown in FIG. 6, in the flexible printed circuit board according to Example 1, the number of corrosions per 25 mm ² is 2.1 when the outer diameter is 0.05 mm or more and 0.12 mm or less, and the outer diameter is 2.1. Corrosion between 0.13 mm and 0.4 mm was 3.0, and corrosion with an outer diameter greater than 0.4 mm was 0.5.

In the flexible printed circuit board according to Example 2, the number of corrosions per 25 mm ² is 1.9 when the outer diameter is 0.05 mm or more and 0.12 mm or less, and the outer diameter is 0.13 mm or more and 0. Corrosion of 0.4 mm or less was 1.7, and corrosion having an outer diameter larger than 0.4 mm was 0.3.

Furthermore, in the flexible printed circuit board according to Example 3, the number of corrosions per 25 mm ² is 1.3 when the outer diameter is 0.05 mm or more and 0.12 mm or less, and the outer diameter is 0.13 mm or more and 0. Corrosion of 4 mm or less was 0.5, and corrosion having an outer diameter greater than 0.4 mm was 0.1.

Further, in the flexible printed circuit board according to Example 4, the number of corrosions per 25 mm ² is 1.1 when the outer diameter is 0.05 mm or more and 0.12 mm or less, and the outer diameter is 0.13 mm or more and 0. Corrosion of 0.4 mm or less was 0.1, and corrosion having an outer diameter greater than 0.4 mm was 0.1.

Furthermore, in the flexible printed circuit board according to Example 5, the number of corrosions per 25 mm ² is 0.9 when the outer diameter is 0.05 mm or more and 0.12 mm or less, and the outer diameter is 0.13 mm or more and 0. Corrosion of 4 mm or less was 0.1, and corrosion having an outer diameter greater than 0.4 mm was 0.2.

On the other hand, in the flexible printed circuit board according to the comparative example, the number of corrosions per 25 mm ² is 2.2 when the outer diameter is 0.05 mm or more and 0.12 mm or less, and the outer diameter is 0.13 mm or more and 0.0. Corrosion of 4 mm or less was 3.3, and corrosion having an outer diameter greater than 0.4 mm was 0.5.

  As described above, in the flexible printed circuit boards of Examples 1 to 5 in which the plating layer 5 is coated with the coverlay adhesive layer 3, the corrosion generated in the conductor pattern 2 is more than that of the flexible printed circuit board of the comparative example. The size and number are reduced.

  As a result, the end surface 5E and the surface coating region 5F of the plating layer 5 are covered with the coverlay adhesive layer 3, so that the external atmosphere contacts the conductor pattern 2 through the interface between the coverlay adhesive layer 3 and the plating layer 5. It became clear that this was prevented.

  In the flexible printed circuit boards of Examples 2 to 5, the magnitude and number of corrosion generated in the conductor pattern 2 are reduced as compared with the flexible printed circuit board of Example 1.

  Thereby, when the coating length of the plating layer 5 by the coverlay adhesive layer 3 is 5 μm or more, the external atmosphere contacts the conductor pattern 2 through the interface between the coverlay adhesive layer 3 and the plating layer 5. It has become clear that this is sufficiently prevented.

  In the flexible printed circuit boards of Examples 3 to 5, the magnitude and number of corrosion generated in the conductor pattern 2 are reduced as compared with the flexible printed circuit boards of Examples 1 and 2.

  Thereby, when the coating length of the plating layer 5 by the coverlay adhesive layer 3 is 10 μm or more, the external atmosphere contacts the conductor pattern 2 through the interface between the coverlay adhesive layer 3 and the plating layer 5. It has become clear that this is even more adequately prevented.

  The present invention is useful when manufacturing a printed circuit board.

1 is an external perspective view of a flexible printed circuit board according to an embodiment of the present invention. 2A is a schematic top view of the flexible printed circuit board of FIG. 1, and FIG. 2B is a partially enlarged sectional view taken along line AA of FIG. 2A. It is typical process sectional drawing which shows the manufacturing method of the flexible printed circuit board of FIG. It is typical process sectional drawing which shows the manufacturing method of the flexible printed circuit board of FIG. It is typical sectional drawing which shows the coating state of the plating layer by a coverlay adhesive bond layer. It is a figure which shows the exposure length in the flexible wiring circuit board of Examples 1-5 and a comparative example, the coating length of the plating layer by a coverlay adhesive bond layer, and a corrosion test result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation layer 1a Base resin layer 1b Base adhesive layer 2 Conductor pattern 3 Coverlay adhesive layer 4 Coverlay film 5 Plating layer 5E End face 100 Flexible printed circuit board

Claims (5)

A first insulating layer;
A conductor layer formed on the first insulating layer and including a metal having a predetermined pattern;
A second insulating layer formed on the first insulating layer via an adhesive layer so as to cover other regions of the conductor layer except for a part of the conductor layer;
A plating layer formed in the partial region of the conductor layer,
The printed circuit board according to claim 1, wherein the adhesive layer protrudes from the other region so as to cover a part of the plating layer on the partial region. The plating layer has an end surface on the conductor layer,
The adhesive layer protruding from the other region has a longitudinal section perpendicular to the end face of the plating layer, and the surface of the plating layer including the end face is covered with the adhesive layer for a length of 5 μm or more and 200 μm or less. The wired circuit board according to claim 1, wherein: 3. The printed circuit board according to claim 2, wherein a surface of the plating layer including the end surface is covered with the adhesive layer for a length of 10 μm or more and 50 μm or less in a longitudinal section perpendicular to the end surface of the plating layer. Forming a conductor layer containing a metal having a predetermined pattern on the first insulating layer;
Forming a second insulating layer on the first insulating layer via an adhesive layer so as to cover other regions of the conductor layer except for a part of the conductor layer;
Bonding the first insulating layer and the second insulating layer by pressurizing the first insulating layer and the second insulating layer;
Forming a plating layer in the partial region of the conductor layer;
A method of manufacturing a printed circuit board, comprising: pressing the first insulating layer and the second insulating layer after forming the plating layer. In the bonding step, the first insulating layer and the second insulating layer are pressurized for a first period;
In the step of pressing the first insulating layer and the second insulating layer after forming the plating layer, the first insulating layer and the second insulating layer are pressed for a second period,
The method for manufacturing a printed circuit board according to claim 4, wherein the first period is shorter than the second period.

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