JP6772567B2 - Printed wiring board and electronic equipment - Google Patents

Description

The present invention relates to a printed wiring board provided with a metal reinforcing plate and an electronic device provided with the printed wiring board.

Electronic devices such as mobile phones and smartphones are generally provided with an electromagnetic wave shield layer to prevent malfunctions caused by electromagnetic wave noise generated by electronic components mounted inside or electromagnetic wave noise invading from the outside. is there. Further, since the printed wiring board mounted inside the electronic device, particularly the flexible printed wiring board, is flexible, when the electronic component is mounted on the surface thereof, it is placed on the other surface of the flexible printed wiring board facing the electronic component mounting surface. A metal plate is attached and reinforced with an adhesive layer. Therefore, Patent Document 1 discloses a printed wiring board in which an electromagnetic wave shielding property is imparted by using a conductive adhesive layer to the adhesive layer.

Further, Patent Document 2 discloses a printed wiring board in which the surface of a metal plate is gold-plated to improve conductivity in order to efficiently remove electromagnetic waves from electronic components.

Japanese Unexamined Patent Publication No. 2005-317946 International Publication 2014/132951

However, the printed wiring board described in Patent Document 1 has improved normal adhesive strength by using a conductive adhesive layer, but a reflow step (for example, 230 to 280 ° C.) in the process of manufacturing the printed wiring board. Therefore, there is a problem that bubbles are generated at the interface between the conductive adhesive layer and the metal reinforcing plate, and the metal reinforcing plate is easily peeled off.
Further, the printed wiring board described in Patent Publication 2 has a problem that the adhesion between the metal plate and the plating formed of a noble metal or the like is weak, cracks occur at the interface, and the resistance value increases.
Further, the plated metal plate formed of a noble metal or the like has a problem that the adhesive force with the conductive adhesive layer is low.

INDUSTRIAL APPLICABILITY The present invention provides a printed wiring board in which bubbles are less likely to be generated even after the reflow step, the conductive adhesive layer and the metal plate have good adhesive strength, and the ground circuit and the metal plate have good conductivity. With the goal.

The printed wiring board of the present invention includes a wiring circuit board, a conductive adhesive layer, and a metal reinforcing plate, and the conductive adhesive layer is adhered to the wiring circuit board and the metal reinforcing plate, respectively, and the metal. The reinforcing plate has an intermediate layer and a surface protective layer on the surface of the metal plate, the intermediate layer is a nickel layer having a thickness of 0.1 to 3 μm, and the surface protective layer has a thickness of 0. It is characterized by having a noble metal layer of 05 to 0.5 μm.

According to the present invention, the metal reinforcing plate has a surface protective layer formed of a noble metal on the surface of the metal plate via a nickel layer which is an intermediate layer, so that the metal reinforcing plate is directly on the surface of the metal plate. It has better adhesiveness than the case where the surface protective layer, which is a noble metal layer, is provided, and the surface protective layer is integrated with the metal plate via the intermediate layer with sufficient adhesion.

In addition, the surface protective layer is often formed extremely thin in order to ensure the flexibility of the printed wiring board, and a large number of microholes are formed on the entire surface. The conductive adhesive invades and becomes a uniform conductive surface on the entire surface. As a result, the adhesive force between the display protection layer and the conductive adhesive layer is strengthened, and the conductivity of the display protection layer is also increased. Further, the surface protective layer formed of a noble metal is less likely to be oxidized, can maintain stable conductivity for a long period of time, and can obtain a printed wiring board having excellent mechanical strength and conductivity.

It is sectional drawing which shows the structure of the printed wiring board of this invention.

Hereinafter, the printed wiring board of the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

FIG. 1 is a cross-sectional view showing the configuration of the printed wiring board of the present invention. In the following, for convenience of explanation, the upper side in FIG. 1 is referred to as “upper” and the lower side is referred to as “lower”.

《Printed circuit board》
As shown in FIG. 1, the printed wiring board 1 of the present invention includes a conductive adhesive layer 3 for adhering a wiring board 6 and a metal reinforcing plate 2. The metal reinforcing plate 2 has a surface protective layer 2c on the surface of a metal plate 2a such as stainless steel via an intermediate layer 2b.
The intermediate layer 2b is a nickel layer having a thickness of 0.1 to 3 μm, and the surface protective layer 2c is a noble metal layer having a thickness of 0.05 to 0.5 μm.
Further, it is preferable that the exposure ratio of the intermediate layer 2b to the surface protective layer 2c is 0.5 to 20%.

An embodiment of the printed wiring board 1 will be further described. By mounting the electronic component 10 on the surface of the wiring board 6 in contact with the insulating base material 9 and facing the metal reinforcing plate 2, the strength required for the printed wiring board 1 can be obtained. By providing the metal reinforcing plate 2, it is possible to prevent damage to the solder-bonded portion or the electronic component 10 when a force such as bending is applied to the printed wiring board 1. Further, the conductive adhesive layer 3 can shield electromagnetic waves from the upper direction to the lower direction of the printed wiring board.

<Metal reinforcement plate>
The metal reinforcing plate of the present invention is provided with a metal plate, and has an intermediate layer and a surface protective layer on the surface of the metal plate.
That is, the metal reinforcing plate 2 has a surface protective layer 2c on the surface of the metal plate 2a such as stainless steel via the intermediate layer 2b.

[Metal plate]
Examples of the metal plate 2a of the metal reinforcing plate 2 include conductive metals such as gold, silver, copper, iron and stainless steel. Among these, stainless steel is preferable in terms of strength, cost and chemical stability as a metal reinforcing plate. The thickness of the metal reinforcing plate 2a is generally about 0.04 to 1 mm.

[Middle layer]
The intermediate layer of the present invention is a layer having nickel, and is a layer formed of at least one of nickel and a nickel alloy. The intermediate layer 2b is formed on the entire surface of the metal plate 2a of the metal reinforcing plate 2.
The thickness of the intermediate layer is 0.1 to 3 μm, more preferably 0.5 to 2 μm. By reducing the thickness of the intermediate layer 2b to 3 μm or less, the surface unevenness of the metal reinforcing plate can be projected onto the outermost surface, so that the peel strength is improved. Further, by setting the thickness of the intermediate layer 2b to 0.1 μm or more, the connection resistance value can be improved.

The intermediate layer 2b can be formed by an electrolytic nickel plating method and an electroless nickel plating method, but the electroless nickel plating method is preferable. Electroless nickel plating has high plating hardness and high adhesion of the surface protective layer, so that the solder float test is good.

Further, the intermediate layer 2b preferably contains phosphorus, and the phosphorus atom (P) concentration in the intermediate layer is preferably 2 to 20% by weight, preferably 5 to 15% by weight, based on the entire intermediate layer (100% by weight). % Is more preferable. By containing 2 to 20% by weight of phosphorus in the intermediate layer, the adhesion between the intermediate layer and the surface protective layer is improved, and the solder float test is improved.
The phosphorus atom concentration is the weight% of phosphorus atoms in all the atoms of the intermediate layer 2b.
Phosphorus atom concentration can be measured by X-ray fluorescence analysis. Quantitative analysis of a metal reinforcing plate having an intermediate layer and a surface protective layer using fluorescent X-rays, and the phosphorus atom concentration when the total of the obtained nickel atoms and phosphorus atoms is 100.

As the metal reinforcing plate 2 having the intermediate layer 2b described in the upper part, the metal plate 2a after the intermediate layer is formed may be sampled, and the metal reinforcing plate 2 having the intermediate layer satisfying these numerical ranges may be appropriately selected and used. good.

[Surface protective layer]
The surface protective layer 2c is a noble metal layer formed on the outermost surface of the metal reinforcing plate 2 via the intermediate layer 2b. The surface protective layer of the present invention is a layer having a noble metal, and is formed of at least one of the noble metal and an alloy thereof.
The thickness of the surface protective layer is 0.05 to 0.5 μm, preferably 0.07 to 0.3 μm. By setting the thickness of the surface protective layer to 0.05 to 0.5 μm, the peel strength and the solder float test are improved.

Precious metals that can be used as the material for the surface protective layer 2c include, for example, gold (Au), silver (Ag), platinum (Pt), palladium (Pd), iridium (Ir), ruthenium (Ru), and osmium (0s). In this example, gold is used for explanation. Further, the surface protective layer 2c can be formed by using an alloy containing a noble metal as a main component as a material.
The surface roughness Ra of the surface protective layer 2c is preferably 0.2 μm or more, more preferably 0.3 μm or more, and further preferably 0.4 μm or more. If the value of the surface roughness Ra is large, the surface of the surface protective layer 2c becomes a rough surface. Therefore, when the metal reinforcing plate 2 and the conductive adhesive layer 3 are thermocompression bonded, the conductive adhesive layer 3 becomes the surface protective layer. It penetrates into the depression on the surface of 2c and strengthens the adhesive force between the two.

The surface roughness Ra is a numerical value measured by measuring the surface of the surface protection layer 2c using a contact type surface roughness meter in accordance with JIS B 0601-2001.

Further, in the metal reinforcing plate of the present invention, pinholes may be formed when the surface protective layer is thinly formed to a certain thickness. Further, by adding a step such as masking when forming the surface protective layer, it is possible to intentionally form pinholes without thinning the surface protective layer. When the surface of the surface protective layer having the pinholes is measured by X-ray photoelectron spectroscopy (XPS), nickel in the intermediate layer is confirmed. In the present invention, the amount of the intermediate layer detected in the surface protective layer confirmed here is defined as the exposure rate.
The exposure rate of this intermediate layer is preferably 0.5 to 20% with respect to the surface protective layer. The exposure rate is more preferably 1 to 15%, further preferably 2 to 10%. When the exposure ratio of the intermediate layer to the surface protective layer is 0.5 to 20%, the peel strength and the solder float test resistance are improved.
The exposure rate can be determined by using X-ray photoelectron spectroscopy (XPS) based on the ratio of the element concentration of the intermediate layer to the element concentration of the surface protection layer.

The ratio of the thickness of the intermediate layer 2b to the surface protective layer 2c is preferably 2 to 30 and more preferably 3 to 20 when the thickness of the surface protective layer 2c is 1 . By setting the thickness ratio to 2 to 30, the peel strength and the connection resistance value can be further improved.

<Conductive adhesive layer>
The conductive adhesive layer 3 is adhered to the wiring circuit board and the metal reinforcing plate, respectively. It is also formed using an isotropic conductive adhesive or an anisotropic conductive adhesive containing a thermosetting resin and a conductive component. Here, the isotropic conductivity is a property of conducting in three-dimensional directions of the X axis (horizontal direction in FIG. 1), the Y axis (depth direction in FIG. 1), and the Z axis (vertical direction in FIG. 1). Also, anisotropic conductivity is a property of conducting only on the Z axis. These conductivitys can be appropriately selected according to the usage mode of the printed wiring board.

The thermosetting resin preferably has at least one of a hydroxyl group and a carboxyl group. Specific examples thereof include acrylic resin, epoxy resin, polyester resin, urethane resin, urethane urea resin, silicone resin, amide resin, imide resin, amide imide resin, elastomer resin and rubber resin. The above resins may be used alone or in combination of two or more.

The thermosetting resin is preferably cured using a curing agent. The curing agent is not limited as long as it is a compound having at least one functional group capable of reacting with the crosslinkable functional group of the thermosetting resin. When the crosslinkable functional group is a carboxyl group, the curing agent is preferably an epoxy compound, an alidirin compound, an isocyanate compound, a polyol compound, an amine compound, a melamine compound, a silane compound, a carbodiimide compound, a metal chelate compound or the like.
When the crosslinkable functional group is a hydroxyl group, the curing agent is preferably an isocyanate compound, an epoxy compound, an aziridine compound, a carbodiimide compound, or a metal chelate compound. When the crosslinkable functional group is an amino group, the curing agent is preferably an isocyanate compound, an epoxy compound, an aziridine compound, a carbodiimide compound, or a metal chelate compound. These curing agents may be used alone or in combination of two or more.

The conductive component can be appropriately selected and used from conductive fine particles, conductive fibers, carbon nanotubes and the like. Examples of the conductive fine particles include metals such as gold, silver, copper, iron, nickel, and aluminum, alloys thereof, and inorganic materials such as carbon black, fullerenes, and graphite. Further, silver-coated copper fine particles in which the surface of the copper particles is coated with silver can also be mentioned.

For the conductive adhesive layer 3, a tackifier resin, an ion collector, an inorganic filler, a metal inactivating agent, a flame retardant, a photopolymerization initiator, an antistatic agent, an antioxidant and the like are appropriately selected. Can include. The thickness of the conductive adhesive layer 3 is usually about 30 to 80 μm.

<Wiring circuit board>
The wiring circuit board 6 includes insulating layers 4a and 4b, adhesive layers 5a and 5b, a ground wiring circuit 7, a wiring circuit 8, and an insulating substrate 9. Further, the wiring circuit board 6 is provided with a columnar or mortar-shaped hole called a via 11 (Via) on the ground wiring circuit 7.

The insulating layers 4a and 4b are also referred to as coverlay films and contain at least a resin. Examples of the resin include acrylic resin, epoxy resin, polyester resin, urethane resin, iretanurea resin, silicone resin, polyamide resin, polyimide resin, amidimide resin and phenol resin. Further, the resin can be appropriately selected from a thermoplastic resin, a thermosetting resin and an ultraviolet curable resin, but a thermosetting resin is preferable in terms of heat resistance. These resins can be used alone or in combination of two or more. The thickness of the insulating layers 4a and 4b is usually about 5 to 50 μm.

Examples of the adhesive layers 5a and 5b include thermosetting resins such as acrylic resin, epoxy resin, polyester resin, urethane resin, silicone resin, and amide resin. Examples of the curing agent used for the thermosetting resin include an epoxy curing agent, an isocyanate curing agent, and an aligirin curing agent. The adhesive layers 5a and 5b are used to bond the insulating layers 4a and 4b to the insulating substrate 9 provided with the ground wiring circuit 7 and the wiring circuit 8, and have insulating properties. The thickness of the adhesive layers 5a and 5b is usually about 1 to 20 μm.

The ground wiring circuit 7 and the wiring circuit 8 are generally formed by etching a conductive metal layer such as copper or by printing a conductive paste. Although not shown, the wiring circuit board 6 may have a plurality of ground wiring circuits 7 and wiring circuits 8. The ground wiring circuit 7 is a circuit that maintains the ground potential, and the wiring circuit 8 is a circuit that transmits an electric signal to an electronic component or the like. The thickness of the ground wiring circuit 7 and the wiring circuit 8 is usually about 5 to 50 μm, respectively.

The insulating substrate 9 is a film having insulating properties such as polyimide, polyamideimide, polyferrensulfide, polyethylene terephthalate, and polyethylene naphthalate, and is a base material for the wiring circuit board 6. The insulating substrate 9 is preferably polyferrensulfide and polyimide when the reflow step is performed, and polyethylene terephthalate is preferable when the reflow step is not performed. The thickness of the insulating substrate 9 is usually about 5 to 100 μm.

The via 11 is formed by etching, a laser, or the like in order to expose a part of a circuit pattern appropriately selected from the ground wiring circuit 7 and the wiring circuit 8. According to FIG. 1, a part of the ground wiring circuit 7 is exposed by the via 11, and the ground wiring circuit 7 and the metal reinforcing plate 2 are electrically connected via the conductive adhesive layer 3. The diameter of the via 11 is usually about 0.5 to 2 μm.

The printed wiring board 1 usually includes an electromagnetic wave shielding sheet. The electromagnetic wave shield sheet generally includes an insulating layer 101, a metal film 102, and a conductive adhesive layer 103, and is particularly preferable when the electric signal flowing through the wiring circuit 8 has a high frequency. On the other hand, although not shown, when the electric signal flowing through the wiring circuit 8 has a relatively low frequency, the electromagnetic wave shield sheet may include at least an insulating layer 101 and a conductive adhesive layer 103.

For the insulating layer 101, in addition to using the film having the insulating property described in the insulating substrate 9, a thermosetting resin such as an acrylic resin, an epoxy resin, a polyester resin, a urethane resin, a silicone resin, and an amide resin is appropriately selected. Can also be formed. The thickness of the insulating layer 101 is usually preferably about 2 to 20 μm.

The metal film 102 is preferably a film formed from conductive metals such as gold, silver, copper, aluminum, and iron, and alloys thereof, and copper is more preferable from the viewpoint of cost. The metal film 102 can be appropriately selected from a rolled metal foil, an electrolytic metal foil, a sputter film and a vapor deposition film, but a rolled metal foil is preferable, and a rolled copper foil is more preferable from the viewpoint of cost. The thickness of the metal film 102 is preferably about 0.1 to 20 μm in the case of a metal foil, preferably about 0.05 to 5.0 μm in the case of a sputtered film, and preferably about 10 to 500 nm in the case of a thin-film film. When forming a sputter film, it is preferable to use ITO (indium tin oxide) or ATO (antimony trioxide), and when forming a vapor deposition film, gold, silver, copper, aluminum or nickel is used. Is preferable.

The conductive adhesive layer 103 preferably contains the raw materials described in the conductive adhesive layer 3. The thickness of the conductive adhesive layer 103 is preferably about 2 to 20 μm.

The method for manufacturing a printed wiring board of the present invention needs to include at least a step of crimping the wiring circuit board 6, the conductive adhesive layer 3, and the metal reinforcing plate 2. For crimping, for example, a method of crimping the wiring circuit board 6 and the electromagnetic wave shield sheet, then laminating the conductive adhesive layer 3 and the metal reinforcing plate 2 and then mounting the electronic components can be mentioned. Is not limited. The present invention may include a step of crimping the wiring circuit board 6, the conductive adhesive layer 3, and the metal reinforcing plate 2, and the other steps can be appropriately changed according to the configuration or usage mode of the printed wiring board. ..
When the conductive adhesive layer 3 contains a thermosetting resin, the pressure bonding is particularly preferably performed at the same time from the viewpoint of promoting curing. On the other hand, even when the conductive adhesive layer 3 contains a thermoplastic resin, it is preferable to heat it because the adhesion tends to be strong. Heating is preferably about 150 to 180 ° C., and crimping is preferably about 3 to 30 kg / cm ² . As the crimping device, a flat plate crimping machine or a roll crimping machine can be used, but when the flat plate crimping machine is used, a constant pressure can be applied for a constant time, which is preferable. The crimping time is not particularly limited as long as the wiring circuit board 6, the conductive adhesive layer 3, and the metal reinforcing plate 2 are sufficiently adhered to each other, but is usually about 30 minutes to 2 hours.

The printed wiring board of the present invention is not only mounted (equipped) on electronic devices such as mobile phones, smartphones, notebook PCs, digital cameras, and liquid crystal displays, but also on transportation devices such as automobiles, trains, ships, and aircraft. It can be suitably mounted (prepared).

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

The members used for the evaluation are as follows.

<Conductive adhesive sheet A>
100 parts of thermocurable polyamide resin (acid value = 10 mgKOH / g, manufactured by Toyochem), conductive fine particles (copper for core, silver for coating layer, dendritic particles D50, average particle diameter = 12 μm, Fukuda metal foil (Manufactured by Powder Industry Co., Ltd.) was placed in a container, and a mixed solvent of toluene: isopropyl alcohol (weight ratio = 2: 1) was added and mixed so that the non-volatile content concentration became 40% by weight. Next, add 40 parts of bisphenol A type epoxy resin ("JER828" (epoxy equivalent = 189 g / eq) manufactured by Mitsubishi Chemical Corporation) and 15 parts of amine-based epoxy curing agent ("YN100" manufactured by Mitsubishi Chemical Corporation) for 10 minutes with a disper. A conductive resin composition was prepared by stirring. The obtained conductive resin composition is applied to the release-treated surface of the release film so as to have a thickness of 60 μm after drying using a doctor blade, and in an electric oven at 100 ° C. 2 The conductive adhesive sheet A was obtained by drying for a minute.

<Conductive adhesive sheet B>
100 parts of thermocurable polyamide resin (acid value = 10 mgKOH / g, manufactured by Toyochem), conductive fine particles (copper for core, silver for coating layer, dendritic particles D50, average particle diameter = 12 μm, Fukuda metal foil (Manufactured by Powder Industry Co., Ltd.) was placed in a container, and a mixed solvent of toluene: isopropyl alcohol (weight ratio = 2: 1) was added and mixed so that the non-volatile content concentration became 40% by weight. Next, add 40 parts of bisphenol A type epoxy resin ("JER828" (epoxy equivalent = 189 g / eq) manufactured by Mitsubishi Chemical Corporation) and 15 parts of imidazole epoxy curing agent ("EMI24" manufactured by Mitsubishi Chemical Corporation) for 10 minutes with a disper. A conductive resin composition was prepared by stirring. The obtained conductive resin composition is applied to the release-treated surface of the release film so as to have a thickness of 60 μm after drying using a doctor blade, and in an electric oven at 100 ° C. 2 The conductive adhesive sheet B was obtained by drying for a minute.

<Conductive adhesive sheet C>
100 parts of thermocurable polyurethane urea resin (acid value = 5 mgKOH / g, manufactured by Toyochem), conductive fine particles (copper for core, silver for coating layer, dendritic particles D50, average particle diameter = 12 μm, Fukuda Metals (Manufactured by Foil Powder Industry Co., Ltd.) was charged in 400 parts of a container, and a mixed solvent of toluene: isopropyl alcohol (weight ratio = 2: 1) was added and mixed so that the non-volatile content concentration became 40% by weight. Next, add 40 parts of bisphenol A type epoxy resin ("JER828" (epoxy equivalent = 189 g / eq) manufactured by Mitsubishi Chemical Corporation) and 15 parts of amine-based epoxy curing agent ("YN100" manufactured by Mitsubishi Chemical Corporation) for 10 minutes with a disper. A conductive resin composition was prepared by stirring. The obtained conductive resin composition is applied to the release-treated surface of the release film so as to have a thickness of 60 μm after drying using a doctor blade, and in an electric oven at 100 ° C. 2 The conductive adhesive sheet C was obtained by drying for a minute.

<Wiring circuit board>
Copper-clad laminate; Esperflex (8 μm thick copper foil / 38 μm thick polyimide manufactured by Sumitomo Metal Mining Co., Ltd.)

<Metal reinforcement plate>
An electroless plating was performed on each of the commercially available stainless steel plates to form an intermediate layer made of nickel on the surface of the stainless steel plate, and then a surface protective layer made of a precious metal was formed by electrolytic plating. Sampling is performed by adjusting the conditions of electroless plating by a known method, and a stainless steel plate having an intermediate layer and a surface protective layer having different thicknesses, exposure rates and surface roughness Ra, respectively (hereinafter, simply 1 to 8 and 11 and 12 (referred to as SUS plate) (SUS 1 to 8 and 11 and 12) were obtained. A stainless steel plate 9 (SUS9) was obtained by directly forming a precious metal layer on the surface of the stainless steel plate without electroless plating. Further, by performing only electroless plating on the surface of the stainless steel plate, a stainless steel plate 10 (SUS10) having only a nickel layer was obtained. Then, each SUS plate was prepared on a test plate A having a thickness of 0.2 mm, a width of 30 mm, and a length of 150 mm, and a test plate B having a thickness of 0.2 mm, a width of 30 mm, and a length of 50 mm. A test plate for analysis was prepared separately.

The obtained SUS plates (SUS1 to 12) were analyzed by the methods shown below. The results are shown in Tables 1 and 2.

<Phosphorus atom concentration (P concentration)>
The phosphorus atom concentration was measured by a fluorescent X-ray analyzer "SII SEA5120" manufactured by Seiko Instruments Inc. The measurement conditions were vacuum and the collimator diameter was 1.8 mm. Quantitative analysis by bulk FP application was performed, and the weight% of phosphorus atom when the total of nickel atom and phosphorus atom of the obtained quantification result was 100 was defined as the phosphorus atom concentration.

<Intermediate layer / Surface protection layer thickness ratio>
From each film thickness value, the ratio of the thickness of the intermediate layer was obtained when the thickness of the surface protective layer was 1 .

<Exposure rate>
The exposure rate was calculated by performing XPS analysis on the surface of the obtained test plate under the following conditions.

A double-sided adhesive tape was attached to a dedicated pedestal, and a SUS plate was fixed as a measurement sample. The measurement sample was measured at three different locations under the following conditions.
Equipment: AXIS-HS (manufactured by Shimadzu / Kratos)
Vacuum degree in sample chamber: 1 × ^10-8 Torr or less X-ray source: Dual (Al) 15 kV, 5 mA Pass energy 80 eV
Step: 0.1 eV / Step
Speed: 120 seconds / element Dell: 300, total number of times: 5
Photoelectron extraction angle: 90 degrees with respect to the sample surface Binding energy: Shift correction with C1s main peak as 284.6 eV Au (4f) peak region: 80 to 92 eV
Ni (2p) peak region: 880 to 845 eV
Ag (3d) peak region: 376-362 eV
Pd (3d) peak region: 330-350 eV

The peaks appearing in the peak region were smoothed, a baseline was drawn by a linear method, and the atomic concentrations of nickel and precious metals "Atomic Conc" were determined.
For the nickel atom concentration in the total of 100% of the obtained gold atom concentration and nickel atom concentration, the average value of the values at three points was calculated and used as the exposure rate.
When nickel or a noble metal is the alloy, the atomic concentration was calculated by taking into account the peak of the alloy, and the exposure rate of the intermediate layer was calculated.

<Surface roughness (Ra)>
The surface roughness Ra was measured under the following conditions according to JISB0601'2001.
Ra refers to the arithmetic average roughness Ra, which is the defined center line average roughness, and refers to the center line average roughness when the reference roughness is 1 mm. The above SUS plate is surface roughness using a contact type surface roughness meter (“SURFCOM 480A” manufactured by Tokyo Seimitsu Co., Ltd.) under the conditions of a measurement speed of 0.03 mm / s, a measurement length of 2 mm, and a cutoff value of 0.8 mm. Ra was measured. The average value of Ra at 5 locations obtained by changing the measurement location was defined as Ra.

"Examples 1 to 10 and Comparative Examples 1 to 4"
<Preparation of test laminate>
The conductive adhesive sheet was prepared to have a width of 25 mm and a length of 100 mm. Next, one of the peelable sheets was peeled off and the exposed conductive adhesive layer was placed on the test plate A obtained from the metal reinforcing plate shown in Table 1, and a roll laminator (SA-1010 small desktop test laminator Tester Sangyo Co., Ltd.). Temporarily fixed at 90 ° C., 3 kgf / cm2, 1 m / min. Then, the other peelable sheet was peeled off, placed on the exposed conductive adhesive layer so that the polyimide surface of Esperflex was in contact with the conductive adhesive layer, and temporarily fixed under the same roll laminating conditions as described above. Then, these were crimped under the conditions of 170 ° C., 2 MPa, and 5 minutes, and then heated in an electric oven at 160 ° C. for 60 minutes to obtain a laminate.
However, Examples 5, 7 and 8 are reference examples.

<Peeling strength>
The obtained laminate was subjected to a T-peel peeling test at a tensile speed of 50 mm / min in an atmosphere of 23 ° C. and a relative humidity of 50% in order to measure the peel strength between the conductive adhesive layer and the test plate. The peel strength (N / cm) at 23 ° C.) was measured. A small desktop testing machine (manufactured by EZ-TEST Shimadzu Corporation) was used as the testing machine. The peel strength is also referred to as adhesive strength.

The laminate obtained for measuring the peel strength after reflow was subjected to a reflow treatment at a peak temperature of 260 ° C. using a small reflow machine (manufactured by SOLSYS-62501RTP Antom). The laminate was left to stand in an atmosphere of 23 ° C. and a relative humidity of 50% for 1 hour, and then the peel strength (N / cm) after reflow was measured in the same atmosphere in the same manner as described above. The peel strength was evaluated according to the following criteria.
◯: Peeling strength is 8 N / cm or more Δ: Peeling strength is 3 N / cm or more and less than 8 N / cm ×: Peeling strength is less than 3 N / cm

<Solder float test>
The obtained laminate was floated on molten solder at 260 ° C. for 1 minute with the metal reinforcing plate facing down. Next, the appearance of the conductive adhesive layer was visually confirmed from the side surface of the laminated body immediately after being taken out from the molten solder, and evaluated according to the following criteria. A square solder tank (POT100C manufactured by Taiyo Denki Sangyo Co., Ltd.) was used for the evaluation. The evaluation was performed 5 times per sample.
◯: During the evaluation of 5, no abnormality was observed in all the samples. Excellent Δ: Bubbles were generated in 1 or 2 evaluations out of 5 evaluations. Practical useability ×: Bubbles were generated in 3 or more evaluations out of 5 evaluations. Not practical

<Connection resistance value>
<Test laminate <Except that the size of the conductive adhesive sheet used in <Preparation of test laminate> was changed to a size of 10 mm in width and 50 mm in length, and test plate A was replaced with test plate B. A laminate was obtained by performing the same procedure as in>. About the obtained laminate The connection resistance value of the obtained laminate was measured by the two-terminal method using a resistivity meter (Lorester GP MCP-T600 manufactured by Mitsubishi Chemical Corporation). The connection resistance value was evaluated according to the following criteria.
◯: Connection resistance value is less than 20 mΩ / □ Δ: Connection resistance value is 20 mΩ / □ or more, less than 40 mΩ / □ ×: Connection resistance value is 40 mΩ / □ or more

From the results of Tables 1 and 2, the printed wiring board provided with the wiring circuit board, the conductive adhesive layer, and the metal reinforcing plate according to Examples 1 to 10 is less likely to generate air bubbles even after the reflow process, and is conductively bonded. The agent layer and the metal plate had good adhesive strength, and the ground circuit and the metal plate had good conductivity.
On the other hand, the printed wiring board of the comparative example could not satisfy all of the conductivity, the peel strength, and the solder float property between the ground circuit and the metal plate.

Therefore, the electronic device provided with the printed wiring board having excellent mechanical strength and conductivity according to the present invention causes a long-term malfunction due to electromagnetic noise generated by the electronic components mounted inside or electromagnetic noise invading from the outside. It is possible to prevent it in a stable manner.
Further, since the printed wiring board has a good adhesive force between the conductive adhesive layer and the metal plate, the electronic device using the printed wiring board is resistant to vibration and dropping, and maintains stable operation for a long period of time. Can be done.

1 Printed wiring board 2 Metal reinforcing plate 2a Metal plate 2b Intermediate layer 2c Surface protection layer 3 Conductive adhesive layer 4a Insulation layer 4b Insulation layer 5a Adhesive layer 5b Adhesive layer 6 Wiring circuit board 7 Ground wiring circuit 8 Wiring circuit 9 Insulation base material 10 Electronic components 11 Via 101 Insulation layer 102 Metal film 103 Conductive adhesive layer

Claims (5)

A wiring circuit board, a conductive adhesive layer, and a metal reinforcing plate are provided, the conductive adhesive layer is adhered to the wiring circuit board and the metal reinforcing plate, respectively, and the metal reinforcing plate is a surface of the metal plate. It has an intermediate layer and a surface protective layer.
The intermediate layer is a nickel layer having a thickness of 0.1 to 3 μm.
The surface protective layer, Ri noble metal layer der the thickness of 0.05 to 0.5 [mu] m,
A printed wiring board characterized in that the exposure ratio of the intermediate layer to the surface protective layer is 2 to 20% . Wherein when the one of the thickness of the surface protective layer, according to claim 1 Symbol mounting of the printed wiring board ratio of the thickness of the intermediate layer, characterized in that 2 to 30. The printed wiring board according to claim 1 or 2, wherein the intermediate layer contains phosphorus and the phosphorus atom concentration is 2 to 20% by weight in the entire intermediate layer. The printed wiring board according to any one of claims 1 to 3 , wherein the surface protective layer has a surface roughness Ra of 0.2 μm or more. An electronic device provided with the printed wiring board according to any one of claims 1 to 4 .