JP5627906B2 - Flexible printed circuit board with reinforcing plate and manufacturing method thereof - Google Patents

Description

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

  A hard disk drive (hereinafter also simply referred to as “HDD”) incorporates an actuator for holding a head element portion. As the actuator rotates about the rotation axis, the head element portion is positioned on a desired recording track on the magnetic disk. An FPC unit that performs signal transmission between the head element unit and the control circuit is fixed to the actuator. The FPC unit includes a flexible printed circuit board (hereinafter also simply referred to as “FPC board”) and a preamplifier IC mounted on a predetermined land portion of the FPC board.

  The FPC board performs signal transmission between the control circuit and the preamplifier IC. The preamplifier IC is connected to the head element unit by transmission wiring called a flexure, and the current output from the preamplifier IC is transmitted to the head element unit by the flexure (see, for example, Patent Document 1).

  In recent years, data transfer speeds have increased dramatically due to the increase in the speed of HDDs. As a result, the amount of heat generated by the preamplifier IC is increasing. Therefore, as a heat dissipation measure, a reinforcing plate made of a metal having good thermal conductivity is provided on the back surface of the FPC board on which the preamplifier IC is mounted (see, for example, Patent Document 2). In general, a reinforcing plate made of aluminum (hereinafter, also referred to as “aluminum reinforcing plate”) is used as such a reinforcing plate.

  In order to produce an FPC board with a reinforcing plate by laminating and bonding the aluminum reinforcing plate to the FPC board, various adhesives such as acrylic, epoxy, and urethane can be used. An acrylic adhesive is used when purity such as outgas characteristics is required for HDD applications. Acrylic adhesives are certified as standard adhesives in applications such as HDDs, and are excellent in non-contamination to the periphery.

  In order to laminate and bond the aluminum reinforcing plate to the FPC board, it is necessary to press and heat the FPC board and the aluminum reinforcing board that are stacked via an adhesive.

  Acrylic adhesives require a press treatment for a relatively long time (for example, 45 to 120 minutes) due to the characteristics of the material in order to develop a sufficient adhesive force. Here, such a method of performing a relatively long press process is referred to as a “long-time molding method”. The press apparatus for performing the press process is relatively expensive and the introduction quantity is limited. Therefore, when the press apparatus is occupied for a long time by one press process, there is a problem that the production efficiency of the FPC board with the reinforcing plate is lowered.

  On the other hand, in contrast to the above long-time forming method, there is a method (hereinafter referred to as “quick forming method”) in which the pressing process is relatively short. In this quick molding method, the press treatment time is short (about 10 minutes or less), and a heat treatment called after-cure treatment is performed after the press treatment. The molding pressure and molding temperature in the quick molding press process are almost the same as in the long-time press process. The after-curing process after the press process is performed, for example, under conditions of 150 ° C. or higher and 2 hours or longer.

  In the case of the quick molding method, since the press process is short, the press apparatus is not occupied for a long time by one press process. Further, it is not necessary to lower the temperature of the FPC board when the FPC board is taken out from the press apparatus after the pressing process. That is, in the long-time molding method, the necessary temperature lowering process can be omitted and the after-curing process of the next process can be performed. For this reason, the occupation time of a press apparatus becomes still shorter. Further, the after-curing process can be performed in a large amount by performing in parallel using, for example, a plurality of ovens. Therefore, according to the quick molding method, there is an advantage that the production efficiency of the FPC board with the reinforcing plate can be greatly improved as compared with the long-time molding method.

  However, conventionally, when the quick molding method is applied, the pressurization time (press process) is short, and thus it has been impossible to ensure proper curing conditions for the acrylic adhesive. As a result, there is a problem that sufficient adhesiveness cannot be obtained even after the after-curing treatment. In addition, the method of improving the adhesiveness by the anchor effect due to the roughening of the aluminum plate surface has been known, but even when this method is used, sufficient adhesive strength (under normal temperature and humidity) , Also referred to as “stripping strength”).

  Furthermore, the FPC board with a reinforcing plate manufactured by the conventional quick molding method has a significantly reduced adhesion between the aluminum reinforcing plate and the FPC board in a wet environment that can be assumed as one of the usage environments of the FPC board. End up. That is, the conventional technique has a problem that the water-resistant adhesiveness is inferior.

JP 2007-287197 A JP 2002-314207 A

  The present invention has been made in view of the above circumstances, and is intended to provide a flexible printed circuit board with a reinforcing plate that is applicable to a quick molding method and has excellent adhesion, and a method for manufacturing the same. To do.

  According to an aspect of the present invention, there is provided a flexible printed circuit board having a base film and a wiring pattern formed on at least one surface of the base film, and a metal plate for reinforcing the flexible printed circuit board, the flexible printed circuit board. A reinforcing plate comprising: a metal plate having a chemical conversion film containing zirconium oxide on a surface facing a circuit board and bonded to a cover film that insulates the base film or the wiring pattern through an acrylic adhesive layer A flexible printed circuit board is provided.

  According to another aspect of the present invention, a chemical conversion film containing zirconium oxide is formed on the surface of an aluminum plate, and the aluminum plate on which the chemical conversion film is formed is coated with an acrylic adhesive on a plastic film of a flexible printed circuit board. And forming a laminate in which the aluminum plate and the plastic film are laminated via the acrylic adhesive, by laminating the chemical film so as to be in contact with the acrylic adhesive layer. On the other hand, the manufacturing method of the flexible printed circuit board with a reinforcement board which heat-processes with respect to the said laminated body after a heating and pressurizing process for 10 minutes or less is provided.

  In the present invention, a metal plate on which a chemical conversion film containing zirconium oxide is formed is used as a reinforcing plate for a flexible printed circuit board. The metal plate having the chemical conversion film is bonded to the flexible printed circuit board through an acrylic adhesive layer. In the heat treatment for curing the acrylic adhesive, the hydroxyl groups in the chemical conversion film containing zirconium oxide chemically react with the carboxyl groups and hydroxyl groups in the acrylic adhesive. Thereby, a strong chemical bond is formed in high density. This chemical bond constitutes a bridge across the interface between the chemical conversion film and the acrylic adhesive layer. Therefore, according to the present invention, high adhesive strength can be obtained even when the quick molding method is employed.

  Furthermore, since the chemical bond constituting the above-described cross-linking has a strong bonding force and is not affected by the hydroxyl group of the water molecule, sufficient adhesiveness can be ensured even in a wet environment. That is, according to the present invention, high water-resistant adhesion can be obtained.

(A) is sectional drawing of the FPC board with a reinforcement board which concerns on embodiment of this invention, (b) is a bottom view of the FPC board with a reinforcement board which concerns on embodiment of this invention. It is an expanded sectional view of the A section of Fig.1 (a). (A) is sectional drawing of the FPC unit with a reinforcement board which concerns on embodiment of this invention, (b) is sectional drawing of the FPC unit with a reinforcement board which concerns on the modification of embodiment of this invention. It is a figure for demonstrating a peeling test. It is a figure for demonstrating the surface state of the aluminum reinforcement board after a peeling test.

  Hereinafter, an FPC unit with a reinforcing plate according to an embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the component which has an equivalent function, and detailed description is abbreviate | omitted. The drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones.

  An FPC board with a reinforcing plate according to an embodiment of the present invention will be described with reference to FIG. FIG. 1A shows a cross-sectional view of the FPC board 1 with a reinforcing plate according to this embodiment, and FIG. 1B shows a bottom view of the FPC board 1 with a reinforcing plate.

  The FPC board 1 with a reinforcing plate includes an FPC board 2 having a wiring pattern on the front surface, an acrylic adhesive layer 3 provided on the back surface of the FPC board 2, and the FPC board 2 through the acrylic adhesive layer 3. It has the aluminum reinforcement board 4 affixed on the back surface.

  As can be seen from FIGS. 1A and 1B, the FPC board 2 is composed of mounting regions 2a and 2b and a wiring region 2c. The mounting areas 2a and 2b have land portions 22a and 22b for mounting electronic components. The wiring region 2c is provided so as to be sandwiched between the mounting region 2a and the mounting region 2b, and has a wiring for performing signal transmission between the mounting region 2a and the mounting region 2b.

  The acrylic adhesive layer 3 is provided between the base film 21 of the FPC board 2 and the aluminum reinforcing plate 4. This acrylic adhesive layer 3 is obtained by curing an acrylic adhesive by pressure treatment and heat treatment.

As will be described in detail later, the aluminum reinforcing plate 4 is obtained by processing an aluminum plate that has been subjected to a chemical conversion treatment with a zirconium oxide chemical conversion liquid into a predetermined shape. For this reason, the aluminum reinforcing plate 4 has a chemical conversion film 4 a containing zirconium oxide (ZrO ₂ ) on at least the surface facing the FPC substrate 2.

  As can be seen from FIGS. 1 (a) and 1 (b), the aluminum reinforcing plate 4 is attached to the back surface of the FPC board 2 in the mounting regions 2a and 2b via an acrylic adhesive layer 3. That is, the aluminum reinforcing plate 4 is stuck so that the chemical conversion film 4 a contacts the acrylic adhesive layer 3. The aluminum reinforcing plate 4 functions as a reinforcing plate that reinforces the FPC board 2 so that the FPC board 2 is not bent in the mounting regions 2a and 2b, and dissipates heat generated by the electronic components mounted on the land portions 22a and 22b. Also functions as a heat sink. Note that the aluminum reinforcing plate 4 is not attached to the back surface of the FPC board 2 in the wiring region 2c. Thus, the wiring region 2c is configured to have flexibility.

  Next, a detailed configuration of the FPC board 2 will be described.

  As can be seen from FIG. 1A, the FPC board 2 includes a base film 21 made of a plastic film, a wiring pattern 22 formed on one side of the base film 21, and a plastic provided via an adhesive layer 23. And a cover film 24 made of a film.

  The wiring pattern 22 is made of a conductive material such as copper (Cu). The wiring pattern 22 is formed in a predetermined circuit pattern using a subtractive method, a semi-additive method, a printing method, or the like. As can be seen from FIG. 1A, a part of the wiring pattern 22 is not covered with the cover film 24, and constitutes land portions 22a and 22b for mounting electronic components. In addition, this wiring pattern 22 may be laminated | stacked on the base film 21 via the adhesive agent, and may be laminated | stacked not via an adhesive agent.

  The cover film 24 insulates the wiring pattern 22 excluding the land portions 22 a and 22 b through the adhesive layer 23. As the material for the adhesive layer 23, various adhesives such as acrylic, epoxy, and urethane can be used. Preferably, as described above, an acrylic adhesive excellent in non-contamination to the periphery is used.

  Examples of the plastic film used for the base film 21 and the cover film 24 include a polyimide film, a polyester film, a polyethylene naphthalate film, a polyethersulfone film, a polyetherimide film, a polyetheretherketone film, and a polyparabanic acid film. It is done.

  Next, the adhesion state of the FPC board 2 and the aluminum reinforcing plate 4 will be described in detail with reference to FIG. FIG. 2 shows an enlarged cross-sectional view of a portion A in FIG.

  As shown in FIG. 2, a chemical conversion film 4 a containing zirconium oxide is formed on the surface of the aluminum reinforcing plate 4. And the aluminum reinforcement board 4 is affixed on the base film 21 through the acrylic adhesive layer 3 so that the chemical conversion film 4a may adhere to the acrylic adhesive layer 3. Strictly speaking, an aluminum hydrated oxide layer (not shown) is naturally formed on the surface of the aluminum reinforcing plate 4, and the chemical conversion film 4a is formed on the aluminum hydrated oxide layer. Yes.

  In the vicinity of the interface (Al / Ad) between the acrylic adhesive layer 3 and the chemical conversion film 4a, a strong chemical bond (crosslinking) is formed so as to straddle the interface. The reason for this will be described.

  Hydroxyl groups (OH groups) are present at high density on the surface of the chemical conversion film 4a containing zirconium oxide. When the heat treatment for bonding the aluminum reinforcing plate 4 to the FPC substrate 2 is performed, the hydroxyl group on the surface of the chemical conversion film 4a is converted into a carboxyl group (COOH group) or a hydroxyl group contained in the acrylic adhesive applied to the base film 21 ( Chemical reaction with OH group). As a result of this chemical reaction (dehydration bonding), a strong bond represented by “—C (═O) —O—”, “—O—” or the like is formed near the interface between the chemical conversion film 4 a and the acrylic adhesive layer 3. Crosslinks consisting of are formed with high density. For this reason, the adhesive strength between the aluminum reinforcing plate 4 and the FPC board 2 is increased.

  Next, the configuration of the FPC unit with a reinforcing plate will be described.

  FIG. 3A shows a cross-sectional view of the FPC unit 100 with a reinforcing plate. This FPC unit with a reinforcing plate 100 is obtained by mounting a preamplifier IC 101 on lands 22a and 22a in the mounting region 2a of the FPC board 1 with a reinforcing plate using a solder material 102. In the FPC unit 100 with a reinforcing plate, the heat generated by the preamplifier IC 101 is radiated by the aluminum reinforcing plate 4 attached to the back surface of the FPC board 2 in the mounting region 2a.

  Heretofore, the FPC board 1 with the reinforcing plate and the FPC unit 100 with the reinforcing plate according to the present embodiment have been described.

  Note that the FPC board with a reinforcing plate is not limited to the above configuration.

  For example, the aluminum reinforcing plate 4 may be provided only on the back surface of the base film 21 in either the mounting region 2a or the mounting region 2b.

  Further, instead of the FPC board 2 in which wiring is formed only on one side of the base film 21, a double-sided FPC board 2 'in which wiring is formed on the front and back surfaces of the base film 21 may be used. FIG. 3B shows a cross-sectional view of the FPC unit 200 with a reinforcing plate when the double-sided FPC board 2 ′ is used. The double-sided FPC board 2 ′ has wiring patterns 22 </ b> A and 22 </ b> B formed on the front and back surfaces of the base film 21, respectively. The wiring patterns 22A and 22B are insulated and protected by cover films 24A and 24B provided via adhesive layers 23A and 23B, respectively.

  As shown in FIG. 3B, the aluminum reinforcing plate 4 may be laminated and bonded via the acrylic adhesive layer 3 on the cover film 24B instead of on the base film 21.

  Further, instead of the cover film 24, a predetermined portion of the wiring pattern 22 may be covered with a cover coat made of varnish-like resin. This cover coat may be formed in a desired pattern using a printing technique, or may be formed using a photofabrication technique using a photosensitive resin. When using the photofabrication technique, a photosensitive resin film is applied to predetermined portions of the base film 21 and the wiring pattern 22, and then the resin film is exposed and developed to be patterned into a desired shape. A cover coat is formed. As an advantage of using the cover coat, it is possible to perform patterning with higher accuracy than the cover film. Therefore, for example, an opening or the like can be accurately formed at a desired position. Moreover, you may use a cover film and a cover coat together as needed. For example, the production efficiency can be increased by using a cover coat for a portion that requires high-precision patterning and using a cover film for the other portions.

  Examples of the present invention will be described below. After describing the manufacturing method of the FPC board with a reinforcing plate according to the present embodiment, the measurement result of the peel strength test will be described.

  First, a copper-clad plate in which a copper foil was laminated on one side of a polyimide base film via an adhesive was prepared. Next, after laminating a dry film on the copper-clad plate, exposure and development were performed. Thus, a resist having a predetermined negative pattern was formed on the copper clad plate. Next, the copper foil of the copper-clad plate was etched using this resist as a mask to form a wiring pattern. And the cover film by which the adhesive agent was coated on the single side | surface of a polyimide film was prepared, and the opening part was formed in the predetermined part of this cover film. Subsequently, the cover film provided with the opening was laminated so as to cover the wiring pattern. At this time, the cover film was laminated so that the opening of the cover film corresponds to a portion that needs to be exposed, such as a land portion. Through the above steps, the FPC board according to this example was manufactured. Next, the manufacturing method of an aluminum reinforcement board is demonstrated.

  First, an aluminum plate was prepared, and an oily substance adhering to the surface of the aluminum plate was removed (degreasing treatment). Next, the aluminum plate was washed with water and then immersed in an alkali solution to remove the aluminum oxide layer naturally formed on the surface of the aluminum plate (alkali degreasing treatment). Next, the aluminum plate was washed with water and then immersed in a weakly acidic (pH = about 5 to 6) zirconium oxide conversion solution. As the zirconium oxide conversion liquid, a zirconium compound without addition of phosphoric acid can be used. This zirconium compound without addition of phosphoric acid is, for example, one obtained by adding hydrofluoric acid to fluorozirconic acid (or its ammonium salt).

  Next, the aluminum plate is pulled up from the zirconium oxide chemical conversion solution, washed with water, and then dried in an oven. Through the steps so far, an aluminum plate having a chemical conversion film containing zirconium oxide formed on the surface is obtained. Here, two types of samples were prepared, one containing silicon oxide in the chemical conversion film and the other containing no silicon oxide. The reason for this is that some FPC board uses require that silicon be contained in order to obtain a rust-preventing effect, while others require no silicon. .

  After the chemical conversion treatment, the thickness of the chemical conversion film formed on the surface of the aluminum plate was measured. The thickness of the chemical conversion film was 5 nm regardless of whether or not silicon oxide was contained.

  For comparison with an aluminum plate that has been subjected to chemical conversion treatment, an aluminum plate that is not subjected to chemical conversion treatment (hereinafter referred to as “untreated aluminum plate”) and an aluminum plate that has been subjected to boehmite treatment (hereinafter referred to as “boehmite-treated aluminum plate”). And prepared. In addition, the above-mentioned degreasing process and alkali degreasing process were performed also to the untreated aluminum plate. The boehmite treatment is a treatment for oxidizing the surface of the aluminum plate with hot water of about 80 ° C. to 90 ° C.

  When the thickness of the aluminum oxide layer formed on the surface of these comparative aluminum plates was measured, it was 6 nm for the untreated aluminum plate and 238 nm for the boehmite treated aluminum plate.

  The thicknesses of the chemical conversion film and the aluminum oxide layer are all values measured by a scanning transmission electron microscope (STEM).

  Thereafter, the above four types of aluminum plates (chemically treated aluminum plate containing silicon oxide, chemically treated aluminum plate not containing silicon oxide, untreated aluminum plate and boehmite treated aluminum plate) are each punched into a predetermined shape, and FPC board It was made into the aluminum reinforcement board for affixing on.

  Next, after the FPC substrate and the aluminum reinforcing plate produced as described above were laminated via an acrylic adhesive, press treatment (pressurization / heating treatment) was performed. The press treatment was performed using a quick molding method under the conditions of pressure: 1 MPa, temperature: 190 ° C., and time: 5 minutes. Thereafter, after-curing treatment (temperature: 180 ° C., time: 3 hours) was performed.

  Through the above steps, four types of FPC board samples with reinforcing plates, each of which was laminated and bonded with the above four types of aluminum reinforcing plates, were completed. Hereinafter, for convenience, an FPC substrate with a reinforcing plate using an aluminum plate subjected to zirconium oxide conversion treatment (containing silicon oxide) is type A, and an FPC substrate with a reinforcing plate using an aluminum plate subjected to zirconium oxide conversion treatment (not containing silicon oxide). Type B, an FPC board with a reinforcing plate using an untreated aluminum plate is called Type C, and an FPC board with a reinforcing plate using a boehmite-treated aluminum plate is called Type D.

  Next, an evaluation test of peel strength (peel strength) carried out on these FPC boards with reinforcing plates will be described.

  The peel strength evaluation test was conducted in accordance with the IPC standard (TM650 2.4.9.). The measurement temperature is 25 ° C., the peeling speed is 50 (mm / min), and as shown in FIG. 4, the peeling angle is 90 ° (in FIG. 4) with the aluminum reinforcing plate of the FPC board with reinforcing plate fixed to the base. The FPC board was pulled in the direction directly above.

The peel strength test results are shown in Table 1.

  The conditions “before mounting” and “after mounting” in Table 1 will be described. “Before mounting” indicates a result of evaluating an FPC board with a reinforcing plate that does not undergo thermal history. On the other hand, “after mounting” indicates a result of evaluating an FPC board with a reinforcing plate subjected to a heat treatment equivalent to a thermal history associated with mounting of components on the FPC board. A solder reflow process and an underfill process were assumed as thermal histories associated with component mounting. Specifically, after heat treatment at 220 ° C. for 5 minutes assuming a solder reflow process, heat treatment at 165 ° C. for 30 minutes was performed assuming an underfill process.

  The conditions of “Dry” and “Soak” in Table 1 will be described. “Dry” indicates a case where the test is performed at normal temperature and normal humidity, and “Soak” indicates a case where the test is performed after the sample is immersed in warm water (50 ° C., 1 hour). “Average” and “σ” in Table 1 are the average value and standard deviation (σ) of the measured peel strength. The number of samples is 6 (N = 6).

  The “peeling interface” in Table 1 will be described. This “peeling interface” indicates the state of the peeling interface after the peeling test. The peeling interface state is peeling at the interface (Al / Ad) between the aluminum reinforcing plate (Al) and the acrylic adhesive layer (Adhesive), and the interface between the base film of the FPC board and the acrylic adhesive layer (FPC / Ad). There are three types of cases, namely, peeling at the same time and mixing of both. FIG. 5 shows the state of the aluminum reinforcing plate surface after the peeling test. Fig. 5 (a) shows the case where peeling occurred at the Al / Ad interface, Fig. 5 (b) shows the case where peeling occurred at the FPC / Ad interface, and Fig. 5 (c) shows a mixture at both interfaces. This shows the case where peeling occurred. Peeling occurs at the interface where the adhesive strength is relatively weak. Therefore, if the peeling interface is Al / Ad, it can be seen that the adhesive force at the interface between the aluminum reinforcing plate and the acrylic adhesive layer is relatively lower than the adhesive force at the interface between the FPC board and the acrylic adhesive layer. On the other hand, when the peeling interface is FPC / Ad, it can be seen that the adhesive force at the interface between the aluminum reinforcing plate and the acrylic adhesive layer is relatively higher than the adhesive force at the interface between the FPC substrate and the acrylic adhesive layer.

  As shown in Table 1, with regard to Type A and Type B subjected to the zirconium oxide chemical conversion treatment, the average peel strength is high both in “before mounting” and “after mounting”, and the variation is small. Furthermore, the peel strength is improved after “mounting” compared to “before mounting”. This is because the chemical reaction between the reactive group (hydroxyl group) in the chemical conversion film and the reactive group (carboxyl group, hydroxyl group) in the acrylic adhesive layer further progressed by heat treatment assuming component mounting, and the crosslink density increased. Conceivable.

  Further, for type A and type B subjected to the zirconium oxide chemical conversion treatment, the peel strength did not decrease even in a wet environment, and a peel strength comparable to that in a normal humidity environment was obtained. This is because the bonding force of the chemical bond constituting the cross-linking is strong, and this bond is not affected by moisture entering the adhesive interface in a wet environment. That is, the bond constituting the crosslink has a stronger binding force than the reactivity with the hydroxyl group of the water molecule, and therefore, the adhesive strength of the FPC board with a reinforcing plate of type A and type B does not decrease even in a wet environment. .

  On the other hand, as can be seen from Table 1, regarding Type C using an untreated aluminum plate, the peeling interface is an FPC / Ad interface or a mixture in the “before mounting” state. However, in the “after mounting” state, peeling occurs at the Al / Ad interface, and the adhesive strength between the aluminum reinforcing plate and the acrylic adhesive layer is low. Further, the average peel strength is 352 in a wet environment in the “after mounting” state, which is significantly lower than that in the “before mounting” state. This is thought to be because water molecules penetrated into the adhesive interface between the aluminum reinforcing plate and the acrylic adhesive layer, and the water molecules reacted with chemical bonds that exerted adhesive strength, thereby reducing the crosslink density. .

  In Type D using a boehmite-treated aluminum plate, peeling occurs at the FPC / Ad interface before mounting, and the adhesive strength between the aluminum reinforcing plate and the acrylic adhesive layer is high. However, as shown in Table 1, in the wet environment after mounting, the standard deviation σ of peel strength is 123, and the variation is large and unstable. This means that there are many samples with low peel strength, and the yield decreases.

  As can be seen from the above evaluation results of peel strength, in the case of Type A and Type B using an aluminum reinforcing plate subjected to zirconium oxide conversion treatment, regardless of the inclusion of silicon oxide, any condition ("before mounting", A sufficient peel strength could be stably obtained even after “after mounting”, “dry”, and “wet”). Thereby, according to the present Example, it was demonstrated that the FPC board with a reinforcement board which exhibits sufficient adhesive strength in the environment assumed practically is obtained.

  The embodiment and the example of the present invention have been described above. As described above, in the embodiment of the present invention, a chemical conversion treatment is performed on a metal plate made of aluminum, and a chemical conversion film containing zirconium oxide is formed on the surface thereof. Then, the metal plate that has been subjected to the chemical conversion treatment is bonded to the FPC board via an acrylic adhesive. Thereafter, a short press process and after-cure process are performed by a quick molding method. As a result, the hydroxyl groups on the surface of the chemical conversion film containing zirconium oxide chemically react with the carboxyl groups and hydroxyl groups in the acrylic adhesive, and as a result, strong bonds are formed at high density. This bond constitutes a bridge across the interface between the chemical conversion film and the acrylic adhesive layer. As a result, according to the present invention, high adhesive strength can be obtained even when the quick molding method is employed.

  Furthermore, since the binding force of the bond constituting the above-described crosslinking is strong and is not affected by the hydroxyl group of the water molecule, sufficient adhesiveness can be ensured even in a wet environment. That is, according to the present invention, high water-resistant adhesion can be obtained.

  Further, the chemical conversion treatment according to the present invention has no possibility of adversely affecting the environment unlike the chromate treatment using hexavalent chromium, and there is no problem in industrial use.

  In the above description, the FPC unit used in the HDD is taken as an example of the FPC board with a reinforcing plate. However, the present invention is not limited to this, and may be applied to an FPC board with a reinforcing plate for any application. it can.

  In the above description, an aluminum plate is used as the reinforcing plate. However, the present invention is not limited to this, and another metal plate capable of zirconium oxide conversion treatment may be used.

  Based on the above description, those skilled in the art may be able to conceive additional effects and various modifications of the present invention, but the aspects of the present invention are not limited to the above-described embodiments. Various additions, modifications, and partial deletions can be made without departing from the concept and spirit of the present invention derived from the contents defined in the claims and equivalents thereof.

1 FPC board with reinforcing plate 2 FPC board (single-sided FPC board)
2 'Double-sided FPC boards 2a, 2b Mounting area 2c Wiring area 21 Base films 22, 22A, 22B Wiring patterns 22a, 22b Land portions 23, 23A, 23B Adhesive layers 24, 24A, 24B Cover film 3 Acrylic adhesive layer 4 Aluminum reinforcing plate 4a Chemical conversion coating 100, 200 FPC unit with reinforcing plate 101 Preamplifier IC
102 Solder material

Claims (6)

A flexible printed circuit board having a base film and a wiring pattern formed on at least one surface of the base film;
A metal plate that reinforces the flexible printed circuit board, has a chemical conversion film containing zirconium oxide on a surface facing the flexible printed circuit board, and the base film or the wiring via an acrylic adhesive layer A metal plate adhered to a cover film that insulates the pattern;
A flexible printed circuit board with a reinforcing plate, comprising: Including a land portion formed on a surface of the base film, the first mounting region and the second mounting region, and the first mounting region and the second mounting region, the first mounting region and the first mounting region, A flexible printed circuit board comprising: a wiring region including a wiring electrically connecting the land portion of the mounting region and the land portion of the second mounting region;
An acrylic adhesive layer formed on the back surface of the base film in the first mounting region and / or the second mounting region;
An aluminum reinforcing plate having a chemical conversion film containing zirconium oxide on the surface facing the flexible printed circuit board, and being bonded to the base film via the acrylic adhesive layer;
A flexible printed circuit board with a reinforcing plate, comprising:   The flexible printed circuit board with a reinforcing plate according to claim 1, wherein the chemical conversion film contains silicon oxide.   4. The flexible printed circuit board with a reinforcing plate according to claim 2, further comprising a preamplifier IC mounted on the land portion. Form a chemical conversion film containing zirconium oxide on the surface of the aluminum plate,
The aluminum plate on which the chemical conversion film is formed is laminated on a plastic film of a flexible printed circuit board via an acrylic adhesive so that the chemical conversion film is in contact with the acrylic adhesive layer. Forming a laminate in which the aluminum plate and the plastic film are laminated through an acrylic adhesive,
The laminated body is heated / pressurized for 10 minutes or less, and then the laminated body is heated.
A method for producing a flexible printed circuit board with a reinforcing plate. It is a manufacturing method of the flexible printed circuit board with a reinforcement board according to claim 5,
The chemical conversion film is formed by immersing the aluminum plate in a zirconium oxide chemical conversion solution in which hydrofluoric acid is added to fluorozirconic acid or an ammonium salt of fluorozirconic acid and phosphoric acid is not added.
A method for producing a flexible printed circuit board with a reinforcing plate.

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