JP2023059011A - Metal-clad laminate - Google Patents

Abstract

To provide a metal-clad laminate satisfying all of dielectric properties, heat resistance and dimensional stability with a high level and having high bending resistance.SOLUTION: A metal-clad laminate is provided which includes a first fluororesin layer, polyimide layers, a second fluororesin layer and metal foil. The first fluororesin layer contains polytetrafluoroethylene and a powdered filler. The polyimide layers are provided on both sides of the first fluororesin layer, respectively and include polyimide. The second fluororesin layer is provided on the polyimide layer and includes perfluoro-alkoxy alkane. The metal foil is provided on the second fluororesin layer.SELECTED DRAWING: Figure 1

Description

The present invention relates to a metal-clad laminate.

2. Description of the Related Art Communication systems using high-frequency bands are attracting attention as the information communication environment in recent years becomes more diversified and sophisticated. Among the high frequency bands, high frequencies of 30 GHz or higher, which are so-called millimeter waves, have a very large transmission information capacity, but are characterized by a tendency to increase transmission loss. Therefore, there is an increasing demand for a millimeter-wave low-loss substrate capable of reducing transmission loss even when transmitting millimeter waves.

Since fluororesin is a material with excellent dielectric properties, laminates comprising a dielectric containing fluororesin and a metal foil as a conductor are used in various applications utilizing high frequency bands. In such a laminate, since an electrical signal passes through the interface between the dielectric and the conductor, the smoother the interface, the smaller the transmission loss.

On the other hand, the fluororesin has a large coefficient of thermal expansion, so it is not excellent in dimensional stability. Therefore, FCCL (Flexible Cupper Clad Laminate) having a polyimide layer with a small thermal expansion coefficient is used as a laminate for high frequency bands. However, since polyimide does not necessarily have excellent dielectric properties, a metal-clad laminate satisfying all of dielectric properties, heat resistance and dimensional stability at a high level has not been obtained.

JP 2011-011456 A JP 2017-024265 A

In addition to these properties, FCCL is required to have, for example, high bending resistance. As flexible printed circuit boards (FPCs) become thinner, the amount of deflection due to their own weight increases, resulting in poor handling during processing. This can be suppressed if the FCCL has a high bending resistance. Polyimide has a property of high bending resistance compared to polytetrafluoroethylene (PTFE).

SUMMARY OF THE INVENTION It is an object of the present invention to provide a metal-clad laminate that satisfies all of dielectric properties, heat resistance and dimensional stability at a high level and has high bending resistance.

According to one aspect of the present invention, a metal-clad laminate is provided. A metal-clad laminate includes a first fluororesin layer, a polyimide layer, a second fluororesin layer, and a metal foil. The first fluororesin layer contains polytetrafluoroethylene and a powdery filler. The polyimide layers are provided on both sides of the first fluororesin layer and contain polyimide. The second fluororesin layer is provided on the polyimide layer and contains perfluoroalkoxyalkane. A metal foil is provided on the second fluororesin layer.

According to the present invention, it is possible to provide a metal-clad laminate that satisfies all of dielectric properties, heat resistance and dimensional stability at high levels and has high bending resistance.

BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows schematically an example of the metal tension laminate sheet which concerns on embodiment. Sectional drawing which shows roughly the other example of the metal-clad laminated board which concerns on embodiment.

Hereinafter, embodiments will be described with reference to the drawings as appropriate. In addition, the same code|symbol shall be attached|subjected to the common structure through embodiment, and the overlapping description is abbreviate|omitted. In addition, each drawing is a schematic diagram for explaining the embodiments and promoting understanding thereof, and there are places where the shapes, dimensions, ratios, etc. are different from the actual device, but these are the following explanations and known techniques. Consideration can be taken into consideration and the design can be changed as appropriate.

A metal-clad laminate according to an embodiment will be described with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing an example of a metal-clad laminate. The metal-clad laminate 10 may be a printed circuit board provided with a pattern circuit formed by etching a metal foil. Metal-clad laminates can be mounted in various devices such as image sensors, in-vehicle radars for collision prevention, and large-capacity wireless communication mainly for applications such as IoT (Internet of Things) and 5G.

A metal-clad laminate 10 includes a first fluororesin layer 1 , a polyimide layer 2 , a second fluororesin layer 3 , and a metal foil 4 . A laminate consisting of the first fluororesin layer 1 , the polyimide layer 2 and the second fluororesin layer 3 excluding the metal foil 4 can constitute the dielectric 5 . Polyimide layers 2 are provided on both surfaces of the first fluororesin layer 1, respectively. Since the two polyimide layers 2 are provided on both sides of the first fluororesin layer 1, deformation (flare and wrinkle) of the polyimide layer 2 can be suppressed. If the polyimide layer is provided only on one side of the first fluororesin layer, the polyimide layer tends to deform due to the difference in coefficient of linear expansion and shrinkage force between the first fluororesin layer and the polyimide layer. In the metal-clad laminate according to the embodiment, since the polyimide layers 2 are provided on both surfaces of the first fluororesin layer 1, the mechanical strength and dimensional stability of the first fluororesin layer 1 or the metal-clad laminate 10 as a whole are improved. sexuality increases.

The metal-clad laminate, in which deformation of the polyimide layer is suppressed, is free from curling and warping, and has high smoothness. Lead-free mounting is increasing from the viewpoint of increasing the density of printed wiring boards and reducing the environmental load. Along with this, the suppression of substrate warpage during mounting is becoming more important. If an FCCL that is less likely to warp can be provided, connection failures between components and the board due to board warpage during mounting can be suppressed, and high connection reliability can be ensured.

The first fluororesin layer contains polytetrafluoroethylene (PTFE) and a powdery filler. The first fluororesin layer has a sheet or film shape. Since PTFE has excellent dielectric properties, the metal-clad laminate including the first fluororesin layer can be used in a high frequency band. The first fluororesin layer may consist of PTFE and a powdery filler. Since PTFE has a high melting point and a high maximum continuous use temperature, the first fluororesin layer can improve the heat resistance of the metal-clad laminate.

For example, lead-free solder, which has a higher melting point than lead-containing solder, can be used for processing a substrate in which the first fluorine resin layer includes PTFE. A metal-clad laminate including a first fluororesin layer containing PTFE can have a continuous heat resistance of 260° C. or higher. The heat resistance of the metal-clad laminate can be evaluated by a solder heat resistance test according to JIS C 6481.

Powdered fillers can be inorganic fillers and/or organic fillers. When the first fluororesin layer contains the powdered filler, the coefficient of thermal expansion (CTE) of the first fluororesin layer is reduced compared to when the first fluororesin layer does not contain the powdered filler. can be done. The volume ratio of the powdery filler in the first fluororesin layer is, for example, within the range of 10% to 70%, preferably within the range of 40% to 60%. If the ratio is too small, the thermal expansion coefficient of the dielectric including the first fluororesin layer may be too large. If the ratio is too large, the mechanical strength (bending resistance) of the dielectric tends to be insufficient.

Examples of inorganic fillers include silica (silicon dioxide), clay, talc, calcium carbonate, mica, diatomaceous earth, alumina, zinc oxide, titanium oxide, calcium oxide, magnesium oxide, iron oxide, tin oxide, antimony oxide, and calcium hydroxide. , magnesium hydroxide, aluminum hydroxide, basic magnesium carbonate, magnesium carbonate, zinc carbonate, barium carbonate, dawsonite, hydrotalcite, calcium sulfate, barium sulfate, calcium silicate, montmorillonite, bentonite, activated clay, sepiolite, imogolite, celery Sight, glass fibers, glass beads, silica-based balloons, carbon black, graphite, carbon fibers, carbon balloons, wood powder, zinc borate, and the like. The first fluororesin layer may contain one type of inorganic filler, or may contain two or more types of inorganic fillers. The particle surfaces of the inorganic filler may be subjected to a hydrophobic treatment.

Examples of organic fillers include polyimide powder and LCP (liquid crystal polymer) powder.

In order to enhance the effect of reducing the coefficient of thermal expansion, the powdery filler is preferably an inorganic filler. Among the inorganic fillers, spherical fine particles made of silicon dioxide and having a hydrophobic surface are preferable. In this case, there are effects such as achievement of a low CTE due to silicon dioxide, suppression of hygroscopicity due to surface hydrophobic treatment, retention of flexibility due to spherical fine particles, and overall suppression of increase in dielectric loss tangent Df.

The average particle size of the powdery filler is, for example, within the range of 0.5 μm to 30 μm. The average particle size of the powdery filler was determined by removing the metal foil and polyimide layer from the metal-clad laminate and examining the residue obtained by removing the fluororesin by thermal decomposition using a scanning electron microscope (SEM). It can be measured by performing observation.

The thickness of the first fluororesin layer is, for example, within the range of 10 μm to 75 μm, preferably within the range of 25 μm to 75 μm. The thickness of the first fluororesin layer in the range of 25 μm to 75 μm is preferable from the viewpoint of dielectric properties. Furthermore, in this case, there is an effect of improving the handleability of the film corresponding to the first fluororesin layer during production.

The polyimide layer includes polyimide. The polyimide layer has a sheet or film form. The polyimide layer may consist only of polyimide. The polyimide contained in the polyimide layer may be a highly heat-resistant polyimide or a thermoplastic polyimide. The polyimide contained in the polyimide layer may consist of only a highly heat-resistant polyimide. In this case, the bending resistance of the metal-clad laminate can be further increased. As the polyimide, modified polyimide (MPI) may be used. The polyimide layer may further contain fluororesins such as PTFE and PFA, and foreign materials such as powdered fillers.

The compositions of the two polyimide layers provided on both sides of the first fluororesin layer may be the same or different.

Thermoplastic polyimide refers to polyimides that have a softening point of less than 300°C. The softening point is the temperature at which an object softens rapidly. The softening point of amorphous polyimide is the glass transition point Tg. In crystalline polyimide, the melting point is the softening point. The softening point of the thermoplastic polyimide is preferably in the range of 200°C to 300°C.

An example of thermoplastic polyimide is AURUM (registered trademark) manufactured by Mitsui Chemicals. AURUM® has a glass transition point Tg of 250°C and a melting point Tm of 388°C.

High heat-resistant polyimide refers to polyimide having a glass transition point Tg of 320° C. or higher, or having a higher Tg than the thermal decomposition temperature. The molecular structure of the highly heat-resistant polyimide is not particularly limited as long as it contains 90% by mass or more of non-thermoplastic polyimide.

A highly heat-resistant polyimide can be produced, for example, using a polyamic acid as a precursor. When the polyimide layer contains highly heat-resistant polyimide, the glass transition point Tg of the highly heat-resistant polyimide is higher than the melting point Tm of the fluororesin contained in the second fluororesin layer in contact with the polyimide layer. is preferred. It is more preferable that the glass transition point Tg of the highly heat-resistant polyimide is 10° C. or more higher than the melting point Tm of the fluororesin contained in the second fluororesin layer.

When bonding the polyimide layer and the second fluororesin layer, it is desirable to perform the processing at a temperature of about Tm+10° C. or higher of the melting point of the fluororesin contained in the second fluororesin layer. When the glass transition point Tg of the highly heat-resistant polyimide is higher than this processing temperature, the adhesion between the polyimide layer and the second fluororesin layer can be enhanced.

For example, when the melting point Tm of the fluororesin contained in the second fluororesin layer is in the range of 290° C. to 310° C., the glass transition point Tg of the highly heat-resistant polyimide is preferably 320° C. or higher. Examples of highly heat-resistant polyimides having a glass transition point Tg of 320° C. or higher include Kapton (registered trademark) manufactured by Dupont Co., Ltd., UPILEX-S (registered trademark) manufactured by Ube Industries, Ltd., and , trade name: XENOMAX (registered trademark) manufactured by Xenomax Japan Co., Ltd.;

Modified polyimides include, for example, those obtained by mixing a small amount of monomers other than polyimide to lower the purity when polymerizing monomers such as polyamic acid, those obtained by binding low-molecular-weight oligomers other than polyimide, and other Examples thereof include those obtained by polymerizing a monomer into which a substituent has been introduced together with the monomer.

Each of the polyimide layers is preferably thinner than the first fluororesin layer. Further, it is more preferable that the total thickness of the polyimide layers included in the metal-clad laminate is thinner than the first fluororesin layer. Polyimide has higher hygroscopicity than fluorine resin. Therefore, by decreasing the thickness ratio of the polyimide layer and increasing the thickness ratio of the first fluororesin layer, the dielectric properties are improved.

In the metal clad laminate, the total thickness of the polyimide layer (total thickness of two layers) with respect to the total thickness of the dielectric excluding the metal foil 4 is defined as "PI thickness ratio". That is, the PI thickness ratio is represented by the following formula (1). The PI thickness ratio in the metal-clad laminate is in the range of 10-25, for example. Within this range, it is possible to achieve both the advantages of fluororesin, namely low dielectric properties and low moisture absorption, and the advantages of polyimide, namely high mechanical strength. Therefore, in this case, it is easy to secure an appropriate balance of characteristics as a dielectric for FCCL, which is preferable.
[PI thickness ratio]=[total thickness of polyimide layer]/[total thickness of dielectric]×100 (1)

The thickness of each polyimide layer is, for example, in the range of 5 μm to 15.0 μm. The total thickness of the polyimide layers contained in the metal-clad laminate can be appropriately adjusted according to the total thickness of the dielectric, and is, for example, within the range of 10 μm to 50 μm, preferably within the range of 10 μm to 30 μm. .

In the dielectric 5, the two polyimide layers 2 are provided so as to face the front and back surfaces of the first fluororesin layer 1, respectively. For example, as shown in FIG. 1, in a dielectric 5 configured plane-symmetrically, the first fluorocarbon resin layer 1 is arranged at a position close to a virtual plane of symmetry (not shown). The polyimide layer 2 is positioned away from the plane of symmetry. Since the polyimide layer 2 having a relatively high hardness compared to the first fluororesin layer 1 is arranged outside the dielectric 5, the metal-clad laminate 10 exhibits a high bending resistance. This is the same even in the case of FIG. 2 where the dielectric 5 does not have a perfectly plane-symmetrical structure. The dielectric according to the embodiment does not have to have a plane-symmetric layered structure.

A second fluororesin layer 3 is provided on the polyimide layer 2 . As shown in FIG. 1, a second fluororesin layer 3 may be provided on each surface of two polyimide layers 2 provided on both sides of the first fluororesin layer 1, as shown in FIG. Alternatively, the second fluororesin layer 3 may be provided only on one of the two polyimide layers 2 . A metal foil 4 is provided on the second fluororesin layer 3 . Although not shown, a second fluororesin layer 3 may further exist between the first fluororesin layer 1 and the polyimide layer 2 .

The second fluororesin layer 3 contains perfluoroalkoxyalkane (PFA). Since PFA is a fluororesin having melt fluidity, the second fluororesin layer 3 can function as a layer for bonding the polyimide layer 2 and the metal foil 4 together. The presence of the second fluororesin layer 3 between the polyimide layer 2 and the metal foil 4 can improve the peel strength of the metal foil 4 . The second fluororesin layer 3 preferably consists of PFA only. This is because if the second fluororesin layer 3 contains other components such as an inorganic filler, the brittleness of the second fluororesin layer 3 may increase and the peel strength may decrease.

The thickness of the second fluororesin layer 3 is, for example, within the range of 1 μm to 20 μm, preferably within the range of 2 μm to 12 μm. If the thickness of the second fluororesin layer 3 is less than 1 μm, it may become difficult to obtain the effect of improving the peel strength due to the second fluororesin layer 3 . For example, the peel strength at the interface between the second fluororesin layer and the metal foil or polyimide layer may be extremely reduced. If the thickness of the second fluororesin layer 3 is too large, the material before metal-clad lamination processing tends to curl greatly, resulting in poor handleability.

The thickness of the dielectric is for example in the range from 25 μm to 100 μm, preferably in the range from 50 μm to 100 μm. When the thickness of the dielectric is within this range, continuous molding of the FCCL is facilitated and sufficient flexibility can be exhibited.

The peel strength of the metal foil 4 at room temperature is preferably 1.0 kN/m or more, more preferably 1.2 kN/m or more. In order to increase the peel strength of the metal foil 4, it is effective to use an adhesive modified PFA as the PFA contained in the second fluororesin layer. When the second fluororesin layer contains adhesive modified PFA, it becomes easy to set the peel strength of the metal foil 4 to 1.0 kN/m or more. The second fluororesin layer may consist only of adhesive modified PFA. The peel strength of a metal foil can be measured by a 90° peel test conforming to JIS C 6481 under a normal temperature environment.

Adhesive modified PFAs, for example, further contain modified monomer units that provide improved adhesion to metal foils.

Adhesive modified PFA can be melt-molded and has heat resistance, chemical resistance, weather resistance, low friction, non-adhesion, water and oil repellency, and dielectric properties similar to those of ordinary PFA. . The adhesive modified PFA preferably has a dielectric constant of 2.06 or less and a dielectric loss tangent of 0.002 or less at a frequency of 1 GHz. When measuring the dielectric constant and dielectric loss tangent of the adhesive modified PFA resin, it can be measured according to JIS 2138:2007. When the dielectric constant and dielectric loss tangent of the adhesive modified PFA resin satisfy the above numerical ranges, the metal-clad laminate can have excellent low-loss characteristics.

The melt flow rate of the adhesive modified PFA is preferably in the range of 10g/10min-25g/10min. The tensile strength of the adhesive modified PFA is, for example, 35 MPa or more. The flexural modulus of adhesive modified PFA is, for example, in the range of 600-680 MPa. The melting point of adhesive modified PFA is, for example, 290°C-300°C.

An example of an adhesive modified PFA is Fluon+ EA-2000 manufactured by AGC.

The type of metal foil is not particularly limited, and may be appropriately selected according to the use of the metal-clad laminate. For example, when a laminate is used for an electronic device, materials for the metal foil include copper or copper alloys, stainless steel or alloys thereof, nickel or nickel alloys, aluminum or aluminum alloys. Copper foils such as rolled copper foils and electrolytic copper foils are often used in ordinary laminates used in electronic devices, and copper foils are also suitable for the laminates according to the embodiments. A rust preventive layer (an oxide film such as chromate) or a heat resistant layer may be formed on the surface of the metal foil.

The surface roughness Rz of the surface of the metal foil 4 where the metal foil 4 and the second fluororesin layer 3 are in contact is, for example, 3.0 μm or less, preferably 1.0 μm or less. As long as the peel strength of the metal foil is 3 N/cm or more, it is desirable that the surface roughness Rz be as small as possible. The surface roughness Rz can be 0.5 μm or more according to one example. The surface roughness Rz in the present specification means "maximum height Rz" measured according to JIS C 6515-1998.

The thickness of the metal foil is not particularly limited as long as it can exhibit sufficient functions according to the application of the metal-clad laminate. The thickness of the metal foil is, for example, in the range from 2 μm to 18 μm, preferably in the range from 9 μm to 18 μm.

The total thickness of the metal-clad laminate is, for example, within the range of 50 μm to 200 μm, preferably within the range of 70 μm to 136 μm.

The relative dielectric constant (Dk) of the dielectric portion excluding the metal foil is preferably 3.5 or less, more preferably 3.0 or less. The dielectric loss tangent (Df) of the dielectric portion is preferably 0.0030 or less, more preferably 0.0020 or less.

According to the metal-clad laminate according to the embodiment, while achieving high dimensional stability and mechanical strength due to polyimide, the thickness of the first fluororesin layer and the second fluororesin layer occupying the metal-clad laminate is reduced. You can increase the percentage. Also, the first fluororesin layer containing PTFE is sandwiched between the two polyimide layers. Therefore, the metal-clad laminate according to the embodiment satisfies all dielectric properties, heat resistance and dimensional stability at high levels, and has high bending resistance.

In order to obtain the metal clad laminate according to the embodiment, for example, after laminating each layer so as to have the lamination order shown in FIG. 1 or 2, hot pressing is performed under predetermined pressure and temperature conditions. Cool them. In this way, an integral product in which each layer is integrated is obtained. The second fluororesin layer may be produced by coating a desired film with an aqueous or organic solvent-based dispersion in which PFA resin particles are dispersed, followed by drying.

The method of hot pressing is not particularly limited, and known methods such as an upper and lower flat plate method, a two-roller method, and a belt press method can be employed. For the purpose of avoiding thermal discoloration of the metal foil, it is desirable to perform hot pressing under vacuum and nitrogen gas or other inert atmospheres. In addition, when a thick polyimide film is used as a curing film during hot pressing, in addition to further prevention of thermal discoloration, the effect of reducing wrinkles in each layer (function as a cushioning material) can be expected.

Hot pressing can be performed, for example, for 60 to 150 minutes. The temperature during pressing can be set, for example, within the range of normal temperature to 400.degree. C., preferably within the range of 330.degree. C. to 360.degree.

The press pressure can be set, for example, within the range of 5 kg/cm ² to 50 kg/cm ² . A setting in which no press pressure is applied is also possible. If the pressing pressure is insufficient, the peel strength of the metal foil tends to be poor. Excessively high pressing pressure is not preferable because the dimensions of the laminate may change.

The degree of vacuum can be set, for example, within the range of 0.1 Torr to 800.0 Torr. Too little vacuum can trap air between layers of material, causing delamination and/or metal foil oxidation. An excessively high degree of vacuum may cause the materials to slide and collapse.

[Example]
Examples are described below, but embodiments are not limited to the examples described below.

(Example 1)
Materials (sheets) constituting each layer were prepared as shown below.

A first film constituting a first fluororesin layer was prepared. The first film is a film containing PTFE and silicon dioxide. The content of silicon dioxide contained in the first film was 48% by weight, and its average particle size was 2 μm. The thickness of the first films was 43 μm each. Two sheets of this first film were prepared.

EA-2000 manufactured by AGC Corporation was prepared as the second film constituting the second fluororesin layer. EA-2000 is a fluororesin film consisting essentially of an adhesive modified PFA resin. As the second film, four films having a thickness of 3 μm and two films having a thickness of 2 μm were prepared.

Two sheets of UPILEX-12.5SN manufactured by Ube Industries, Ltd. were prepared as polyimide films constituting the polyimide layer. This polyimide film is a film made of non-thermoplastic polyimide. The thickness of the polyimide films was 12.5 μm each.

Two electrolytic copper foils manufactured by Fukuda Metal Foil & Powder Co., Ltd. were prepared as metal foils constituting the metal foil layer. The surface roughness Rz on one side (matte side) of the electrolytic copper foil was 0.8 μm. Moreover, the thickness of the electrolytic copper foil was 15 μm each.

Each film and metal foil prepared as described above were laminated according to the lamination order (arrangement order) in Table 1 below. When laminating each film, the films were laminated so that the MD directions of the films were aligned with each other. Thus, a laminate before pressing was produced. Table 1 below shows the thickness of the laminate before pressing and the thickness of the metal-clad laminate after pressing, in addition to the order of lamination of each film and metal foil.

After carrying the obtained laminate into a clean room, it was hot-pressed for 60 minutes to produce a metal-clad laminate. As shown in Table 1, the total thickness of the obtained metal-clad laminate was 154 µm. The thickness of the dielectric contained in the metal-clad laminate was 124 μm. The PI thickness ratio in the metal-clad laminate according to Example 1 was 20%.

(Comparative example 1)
A metal-clad laminate according to Comparative Example 1 was produced under the same conditions as in Example 1, except that when producing the laminate, the order of lamination of each film and metal foil was changed as shown in Table 2 below. bottom. Table 2 below shows the thickness of the laminate before pressing and the thickness of the metal-clad laminate after pressing, in addition to the order of lamination of each film and metal foil.

As shown in Table 2, the total thickness of the obtained metal-clad laminate was 153 μm. The thickness of the dielectric contained in the metal-clad laminate was 123 μm. The PI thickness ratio in the metal-clad laminate according to Comparative Example 1 was 20%.

Various measurements described below were performed on the metal-clad laminates produced in Example 1 and Comparative Example 1.

<Measurement of linear thermal expansion coefficient>
Regarding the linear thermal expansion coefficient CTE, the vertical X (MD direction) and horizontal Y direction (TD direction) of the dielectric film comply with IPC-TM 650 2.4.41, and the thickness direction Z of the film conforms to IPC-TM 650 2.4.41. Measured according to TM 650 2.4.24. The analysis temperature was -65°C to 260°C.

<Dielectric property evaluation>
Relative permittivity D _k and dielectric loss tangent D _f were measured according to JPCA-FCL01-2006 by the balanced disk resonator method.

<Measurement of peel strength of metal foil (copper foil)>
The peel strength of one of the two copper foils included in the metal-clad laminate was measured according to Japanese Industrial Standard JIS C 6481. The peeling test was performed at room temperature, and the peeling angle was 90°.

<Measurement of water absorption>
The water absorption was measured according to Japanese Industrial Standard JIS C 6481.

<Gurley bending resistance measurement>
The bending resistance of the metal-clad laminate was measured according to Japanese Industrial Standard JIS L 1096.

<Solder heat resistance test>
A solder heat resistance test was conducted in accordance with JIS C 6481. In the test, the pretreatment was performed under normal conditions, and the solder bath temperature was 260°C. In addition, the normal state means the case where hot water boiling is not performed in the pretreatment. In other words, it means that the metal-clad laminate to be tested is immersed in the solder bath in a moisture-free state.

Various measurement results are summarized in Table 3 below. In Table 3, the row of "linear thermal expansion coefficient CTE X/Y/Z" indicates the CTE in the vertical X-axis direction, the CTE in the horizontal Y-axis direction, and the CTE in the thickness Z-axis direction in order.

As shown in Table 3, in Example 1 in which the first fluororesin layer exists between the two polyimide layers, dielectric properties, heat resistance and dimensional stability are all satisfied at a high level, It had high bending resistance. In addition, in Example 1, in the dielectric having a plane-symmetrical laminated structure, two polyimide layers were present at positions away from the virtual plane of symmetry. degree.

It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the scope of the invention. Further, each embodiment may be implemented in combination as appropriate, in which case the combined effect can be obtained. Furthermore, various inventions are included in the above embodiments, and various inventions can be extracted by combinations selected from a plurality of disclosed constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiments, if the problem can be solved and effects can be obtained, the configuration with the constituent elements deleted can be extracted as an invention.

DESCRIPTION OF SYMBOLS 1... 1st fluorine-resin layer, 2... Polyimide layer, 3... 2nd fluorine-resin layer, 4... Metal foil, 5... Dielectric, 10... Metal clad laminate.

Claims (6)

a first fluororesin layer containing polytetrafluoroethylene and a powdery filler;
polyimide layers respectively provided on both sides of the first fluororesin layer and containing polyimide;
a second fluororesin layer provided on the polyimide layer and containing a perfluoroalkoxyalkane;
and a metal foil provided on the second fluororesin layer. 2. The metal-clad laminate according to claim 1, having a total thickness in the range of 50 μm to 200 μm. 3. The metal-clad laminate according to claim 1, wherein the polyimide layer has a total thickness in the range of 10 μm to 50 μm. 4. The metal-clad laminate according to any one of claims 1 to 3, wherein the volume ratio of the powdery filler in the first fluorine resin layer is in the range of 40% to 60%. The metal-clad laminate according to any one of claims 1 to 4, wherein the metal foil is copper foil. Continuous use temperature measured by solder heat resistance test in accordance with JIS C 6481 is 260 ° C. or higher,
The metal-clad laminate according to any one of claims 1 to 5, wherein the metal foil has a peel strength of 1.0 kN/m at room temperature.

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