JP6765816B2 - Flexible metal laminate and manufacturing method of flexible metal laminate - Google Patents

Description

The present invention relates to a flexible metal laminated plate including an insulating layer and a metal layer , and a method for manufacturing the flexible metal laminated plate .

A flexible metal laminate in which an insulating layer and a metal layer are bonded is used, for example, as a material for manufacturing a flexible printed wiring board.
By the way, if a pinhole is present in the insulating layer of the flexible metal laminate, the withstand voltage of the insulating layer is remarkably lowered in that portion, and an internal short circuit is likely to occur. As a technique for suppressing the occurrence of pinholes in such an insulating layer, for example, a technique disclosed in Patent Document 1 is known.

The technique disclosed in Patent Document 1 suppresses the occurrence of pinholes by devising at the manufacturing stage of the flexible metal laminated plate. Specifically, a process of adhering a resin material and laminating an insulating layer and a step of laminating a metal thin film are set as one unit, and the process is repeated on a supporting support to manufacture a flexible metal laminated plate. In the method, a strip is run on the support prior to laminating the insulating layer on the support. According to this method, foreign matter existing on the support adheres to the strip and is removed, and when the insulating layer is formed, pinholes are suppressed in the insulating layer due to the foreign matter on the support. To. As a result, an internal short circuit caused by a pinhole can be suppressed.

JP-A-11-251181

An object of the present invention is to suppress an internal short circuit caused by a pinhole in an insulating layer in a flexible metal laminated plate by a technique different from that of Patent Document 1.

The flexible metal laminate for achieving the above object includes an insulating layer having a thickness of 25 to 50 μm and a metal layer adhered to one side or both sides of the insulating layer, and the insulating layer has a plurality of sheets. It has a structure in which thermoplastic resin films overlap in the thickness direction.

In the flexible metal laminated plate, the difference in melting point between the plurality of thermoplastic resin films constituting the insulating layer is preferably 150 ° C. or less.

According to the present invention, it is possible to suppress an internal short circuit caused by a pinhole in the insulating layer in the flexible metal laminated plate.

Side view of flexible metal laminate.

Hereinafter, an embodiment of the present invention will be described.
As shown in FIG. 1, the flexible metal laminated plate includes an insulating layer 10 and a metal layer 20 bonded to one or both sides of the insulating layer 10. Note that FIG. 1 illustrates a flexible metal laminate having a metal layer 20 on only one side of the insulating layer 10.

The insulating layer 10 is a laminate having a structure in which a plurality of thermoplastic resin films 11 are overlapped in the thickness direction, and the adjacent thermoplastic resin films 11 are adhered to each other. The number of the thermoplastic resin films 11 constituting the laminate is not particularly limited, but is preferably 2 to 5, for example. In the present embodiment, the insulating layer 10 is composed of a laminate of two thermoplastic resin films 11 of a first thermoplastic resin film 11a and a second thermoplastic resin film 11b. Although details will be described later, in the flexible metal laminate of the present embodiment, the insulating layer 10 is a laminate of the thermoplastic resin film 11 to suppress an internal short circuit caused by a pinhole in the insulating layer 10. ing.

As the type of the thermoplastic resin film 11, a known thermoplastic resin film used for the insulating layer in the flexible metal laminate can be used. Further, the thermoplastic resin film 11 may be a single-layer structure thermoplastic resin film or a multi-layered thermoplastic resin film. The thermoplastic resin film 11 is preferably thermocompression-bonded to the metal layer 20 and to the overlapping thermoplastic resin film 11, and more preferably has good dimensional stability during thermocompression bonding.

Specific examples of the thermoplastic resin film 11 include a multilayer aromatic polyimide film, a single-layer polyimide film, a polyester film (including a liquid crystal film), a polyamide film (including an aramid film), a vinyl ester film, and a fluororesin film. Can be mentioned. The multilayer aromatic polyimide film is a non-crimpable aromatic polyimide film in which a polyimide layer having thermocompression bonding property is formed on both sides, and is commercially available, for example, Upirex (trade name) VT manufactured by Ube Industries, Ltd. Goods can be used. Such a multilayer aromatic polyimide film is described in, for example, Patent Document (Japanese Patent Laid-Open No. 2001-27033).

The insulating layer 10 may be a laminate composed of all the same type of thermoplastic resin film 11, or may be a laminate containing different types of thermoplastic resin film 11. In the case of a laminate containing the same type of thermoplastic resin film 11, the same type of thermoplastic resin film 11 may be continuously overlapped, including the case of a single-layer structure thermoplastic resin film. Further, in the case of a laminate containing different types of thermoplastic resin films 11, it is preferable to use a combination of the thermoplastic resin films 11 in which the difference in melting point between the thermoplastic resin films 11 is 150 ° C. or less.

The thickness of the insulating layer 10 formed as a laminated body of the thermoplastic resin film 11 is 25 to 50 μm. By setting the thickness of the insulating layer 10 to 25 μm or more, the withstand voltage of the insulating layer 10 can be suitably secured. By setting the thickness of the insulating layer 10 to 50 μm or less, the flexibility of the flexible metal laminate can be suitably ensured.

The thickness of each thermoplastic resin film 11 constituting the insulating layer 10 is preferably, for example, 9 to 25 μm, which is ½ or less of the thickness of the insulating layer 10. That is, it is preferable that the ratio of the thickness occupied by one thermoplastic resin film 11 in the insulating layer 10 is 1/2 or less. By setting the thickness of the thermoplastic resin film 11 in the above range, the effect of suppressing an internal short circuit caused by a pinhole in the insulating layer 10 can be suitably exhibited.

The metal layer 20 is made of a metal material such as a metal foil, and is a portion constituting a conductive portion (conductive layer) in the flexible metal laminated plate. The metal constituting the metal layer 20 is not particularly limited, and examples of the metal include copper and copper alloys, stainless steel and alloys thereof, nickel and nickel alloys (including 42 alloys), and aluminum and aluminum alloys. And so on. Further, those having a rust preventive layer, a heat resistant layer (for example, plating treatment of chromium, zinc, etc.), a silane coupling agent, or the like formed on these metal surfaces can also be used.

The thickness of the metal layer 20 is, for example, 1 μm to 1 mm. From the viewpoint of the flexibility of the flexible metal laminated plate, it is preferable to set the thickness of the metal layer 20 to be thin. Further, the surface roughness of the metal layer 20 on the side in contact with the insulating layer 10 is, for example, preferably a ten-point average roughness (Rz) of 5 μm or less, and more preferably 2 μm or less.

Further, when the metal layers 20 are provided on both sides of the insulating layer 10, the types of metals constituting each metal layer 20 and the thickness of each metal layer 20 may be the same or different.
The flexible metal laminated plate of the present embodiment is, for example, in a state where a metal foil constituting the metal layer 20 and a plurality of thermoplastic resin films 11 constituting the insulating layer 10 are laminated, and the metal foil and the thermoplastic resin film 11 are combined. Can be produced by heat-bonding the thermoplastic resin films 11 to each other. In the example shown in FIG. 1, it is manufactured by thermocompression bonding a metal foil constituting the metal layer 20, a first thermoplastic resin film 11a, and a second thermoplastic resin film 11b in a laminated state. Can be done.

The thermocompression bonding between the metal foil and the thermoplastic resin film 11 and the thermocompression bonding between the thermoplastic resin films 11 may be performed at the same time or separately. For example, in a state where only a plurality of thermoplastic resin films 11 constituting the insulating layer 10 are laminated, the thermoplastic resin films 11 are thermally pressure-bonded to each other to produce a laminated body as the insulating layer 10, and then the laminated body is combined with the laminated body. The laminated body and the metal foil may be thermally pressure-bonded in a state where the metal foils are laminated.

The specific method of thermocompression bonding is not particularly limited, and a known method used for manufacturing a flexible metal laminated plate, for example, a method using a roll laminating apparatus and a method using a double belt pressing apparatus can be used. Can be used.

The flexible metal laminate of the present embodiment is used for, for example, FPC (Flexible Printed Circuits), and can also be used for tapes used for mounting methods such as TAB (Tape Automated Bonding) method and COF (Chip on Film) method. it can. In particular, since the flexible metal laminate of the present embodiment has an excellent withstand voltage, it is suitable for applications such as power modules to which a high voltage is applied. Examples of products equipped with a flexible metal laminate include electronic devices such as cameras, personal computers, liquid crystal displays, printers, and mobile devices.

Next, the operation and effect of this embodiment will be described.
(1) The flexible metal laminated plate includes an insulating layer 10 having a thickness of 25 to 50 μm, and a metal layer 20 bonded to one or both sides of the insulating layer 10. The insulating layer 10 has a structure in which a plurality of thermoplastic resin films 11 are overlapped in the thickness direction. That is, the insulating layer 10 is composed of a laminate of the thermoplastic resin films 11.

As shown in FIG. 1, according to the above configuration, even if pinholes 12 are present in the thermoplastic resin film 11 constituting the insulating layer 10, all the thermoplastic resin films 11 constituting the insulating layer 10 As long as the pinholes 12 do not overlap, no through hole is formed in the insulating layer 10. That is, the pinhole 12 existing in one thermoplastic resin film 11 is only an element for reducing the thickness of the portion of the insulating layer 10, and does not become a through hole of the insulating layer 10 as it is. Therefore, even if the pinhole 12 is present in one of the thermoplastic resin films 11 constituting the insulating layer 10, at least one piece of thermoplastic is formed by the portion of the other thermoplastic resin film 11 that overlaps with the pinhole 12. A withstand voltage corresponding to the thickness of the resin film 11 is secured. As a result, an internal short circuit caused by the pinhole 12 in the insulating layer 10 can be suppressed.

(2) The thickness of each thermoplastic resin film 11 constituting the insulating layer 10 is preferably 1/2 or less of the thickness of the insulating layer 10.
In this case, it is possible to reduce the influence of the pinholes 12 existing on one thermoplastic resin film 11 on the withstand voltage of the insulating layer 10.

(3) The thermoplastic resin film 11 is used as the plurality of resin films constituting the insulating layer 10.
According to the above configuration, when the thermoplastic resin films 11 are thermocompression bonded to each other, the thermoplastic resin films 11 are softened to obtain fluidity. Therefore, when the pinhole 12 is present in the thermoplastic resin film 11, the fluidized resin flows into the pinhole 12. Here, since the insulating layer 10 is formed by the laminated body of the thermoplastic resin film 11, the resin of the other thermoplastic resin film 11 that overlaps the thermoplastic resin film 11 in which the pinhole 12 is present is also inside the pinhole 12. Flow into. As a result of a large amount of resin flowing into the pinhole 12 in this way, the pinhole 12 is filled with the flowed resin, and the pinhole 12 disappears or the size of the pinhole 12 becomes smaller.

When the pinhole 12 disappears, the dielectric strength corresponding to the thickness can be maintained while more reliably suppressing the internal short circuit caused by the pinhole 12 in the insulating layer 10. Further, even if the pinholes 12 are not completely eliminated, the possibility that the pinholes 12 of all the thermoplastic resin films 11 overlap is reduced by reducing the size of the pinholes 12. Whether or not the pinhole 12 disappears depends on the size (diameter) of the pinhole 12. For example, when the size of the pinhole 12 is smaller than or equal to the thickness of the thermoplastic resin film 11 in which the pinhole 12 is present, the pinhole 12 is likely to disappear.

(4) It is preferable that the difference in melting point between the plurality of thermoplastic resin films 11 constituting the insulating layer 10 is 150 ° C. or less.
By adopting the thermoplastic resin film 11 having a similar melting point, when the thermoplastic resin films 11 are thermally pressure-bonded to each other, one of the thermoplastic resin films 11 obtains fluidity, but the other thermoplastic resin film 11 is obtained. Is less likely to be in a situation where it is not fluid. As a result, when the thermoplastic resin films 11 are thermally pressure-bonded to each other, the phenomenon that the resin flows into the pinholes 12 from another thermoplastic resin film 11 that overlaps with the thermoplastic resin film 11 in which the pinholes 12 are present is suitably exhibited. Can be made to.

The technical ideas that can be grasped from the above embodiments are described below.
(A) An insulating layer having a thickness of 25 to 50 μm and a metal layer adhered to one or both sides of the insulating layer are provided, and the insulating layer is formed by bonding a plurality of thermoplastic resin films overlapping in the thickness direction to each other. A flexible metal laminated board characterized by being made of

(B) An insulating layer having a thickness of 25 to 50 μm and a metal layer adhered to one or both sides of the insulating layer are provided, and the insulating layer is at least a first layer made of a first thermoplastic resin film. A flexible metal laminate having a second layer made of the second thermoplastic resin film adhered to the first thermoplastic resin film.

(C) Of the plurality of thermoplastic resin films constituting the insulating layer, at least two thermoplastic resin films overlapping in the thickness direction are the same type or different types of thermoplastic resin films.

(D) An insulating layer having a thickness of 25 to 50 μm and a metal layer adhered to one or both sides of the insulating layer are provided, and the insulating layer is a first layer made of a first thermoplastic resin film. A method for producing a flexible metal laminated plate having a second layer made of the second thermoplastic resin film adhered to the first thermoplastic resin film, wherein the metal foil and the first thermoplastic resin are used. A method for producing a flexible metal laminated plate, which comprises laminating a film and the second thermoplastic resin film and heat-bonding them.

Next, the embodiment will be described more specifically with reference to a test example.
<Manufacturing of flexible metal laminate>
(Test Examples 1-2)
Using the metal foil and the thermoplastic resin film shown in Table 1, a flexible metal laminated plate including an insulating layer made of one thermoplastic resin film and a metal layer made of a metal foil bonded to one side of the insulating layer is formed. It was manufactured by a double belt press device. In Test Example 2, a thermoplastic resin film having pinholes (through holes) intentionally provided was used as the thermoplastic resin film.

(Test Examples 3 to 11)
Using the metal foils and thermoplastic resin films shown in Tables 1 and 2, an insulating layer composed of two thermoplastic resin films having a structure in which both films overlap in the thickness direction was bonded to one side of the insulating layer. A flexible metal laminated plate including a metal layer made of a metal foil was produced by a double belt press device. In Test Examples 4 to 8 and 10, a thermoplastic resin film having pinholes (through holes) intentionally provided was used as one or both of the thermoplastic resin films.

(Test Example 12)
Using the metal foil and the thermoplastic resin film shown in Table 2, the insulating layer is composed of two thermoplastic resin films and has a structure in which both films overlap in the thickness direction, and the metal foil bonded to both sides of the insulating layer. A flexible metal laminated plate provided with a metal layer was produced by a double belt press device. As both thermoplastic resin films, a thermoplastic resin film having pinholes (through holes) intentionally provided was used.

The metal foil and the thermoplastic resin film used for producing the flexible metal laminated plate are as follows.
Rolled copper foil: GHY5-93F-HA-V2 (manufactured by JX Nippon Mining & Metals Co., Ltd.)
Electrolytic copper foil: TQ-M4-VSP (manufactured by Mitsui Mining & Smelting Co., Ltd.)
SUS foil: SUS304-H-TA (manufactured by Nisshin Steel Co., Ltd.)
PI: Upirex VT (manufactured by Ube Industries, Ltd.)
LCP: Vexter CTZ-25K (manufactured by Kuraray Co., Ltd.)
PFA: Neophron AF-0025 (manufactured by Daikin Industries, Ltd.)
(Evaluation of withstand voltage)
A predetermined circuit processing was performed on the metal layer of the flexible metal laminated plate of each test example to prepare a measurement sample. The insulation resistance value (withstand voltage) of these measurement samples was measured using a measurement method compliant with JIS C2110-1 (AC, 50 Hz). The results are shown in the "Insulation resistance value" column of Tables 1 and 2. The insulation resistance values shown in Tables 1 and 2 are average values of five measurements. Test Example 2 was made unmeasurable because dielectric breakdown occurred immediately after the start of boosting. The measurement conditions for this measurement are as follows.

Boosting method: Short-time method Boosting speed: 0.5 kV / s
Measurement temperature: 23 ° C
Ambient medium: Silicone oil Electrode: φ25 cylinder / φ25 cylinder Measurement environment: 23 ± 2 ° C, 50 ± 5% RH
(Observation of pinhole)
The state of pinholes was observed in the flexible metal laminated plates of Test Examples 2, 4 to 8 and 10 using a thermoplastic resin film provided with pinholes as the thermoplastic resin film. Specifically, a 25 mm square test piece was cut out from the flexible metal laminated plate, and the metal layer of the test piece was removed by etching. Then, using a microscope (VHX-1000 manufactured by KEYENCE CORPORATION), pinholes provided in each thermoplastic resin film constituting the insulating layer were observed. The results are shown in the "Pinhole status" column of Tables 1 and 2. Here, the case where the pinhole is not confirmed is defined as “disappearing”, and the case where the pinhole is confirmed is defined as “yes”.

As shown in the evaluation results of Test Example 1 and Test Example 2, in the configuration in which the insulating layer made of one thermoplastic resin film is adopted, when the thermoplastic resin film used has pinholes, the flexible metal The insulation resistance value of the laminated board dropped to almost zero. On the other hand, as shown in the evaluation results of the withstand voltage of Test Examples 3 to 6, in the configuration in which the insulating layer composed of two thermoplastic resin films is adopted, pinholes are formed in one or both of the used thermoplastic resin films. Even in the presence of, the insulation resistance value did not decrease significantly as compared with Test Example 2. From these results, it can be seen that by forming the insulating layer of the flexible metal laminate from a plurality of thermoplastic resin films, it is possible to suppress an internal short circuit of the insulating layer due to pinholes in the insulating layer.

Further, the insulation resistance values of Test Example 4 and Test Example 5 using the thermoplastic resin film provided with small pinholes are the same as those of Test Example 3 without pinholes, whereas large pinholes are provided. The insulation resistance value of Test Example 6 using the obtained thermoplastic resin film was about half that of Test Example 3 without pinholes. Then, pinholes were not confirmed in the flexible metal laminates of Test Example 4 and Test Example 5, whereas pinholes were confirmed in the flexible metal laminates of Test Example 6.

From these results, in the case of Test Example 4 and Test Example 5, the resin of the thermoplastic resin film flowed into the pinhole at the manufacturing stage of the flexible metal laminated plate, and the pinhole was filled, so that the pinhole was filled. It is probable that the insulation resistance value was equivalent to that of Test Example 3 without the above. In the case of Test Example 6, since the pinholes were not sufficiently filled, the insulation resistance value was about half that of Test Example 3 without pinholes, that is, the insulation resistance value for one layer of the thermoplastic resin film without pinholes. It is probable that it showed.

Further, in Test Example 2, the size of the pinholes provided on the thermoplastic resin film was the same as that of Test Example 4 and Test Example 5, but pinholes were confirmed. From this result, in the manufacturing stage of the flexible metal laminate, the phenomenon that the resin of the thermoplastic resin film flows into the pinhole and the pinhole is filled is that the insulating layer of the flexible metal laminate is formed by a plurality of thermoplastic resin films. It is considered to be a peculiar phenomenon when it is composed of.

Further, from the results of Test Examples 7 to 12, it can be seen that the same effect can be obtained even when the type of the metal constituting the metal layer or the type of the thermoplastic resin film constituting the insulating layer is changed.

10 ... Insulation layer, 11 ... Thermoplastic resin film, 11a ... First thermoplastic resin film, 11b ... Second thermoplastic resin film, 12 ... Pinhole, 20 ... Metal layer.

Claims (3)

An insulating layer having a thickness of 25 to 50 μm and
A metal layer adhered to one side or both sides of the insulating layer is provided.
The insulating layer, a plurality of thermoplastic resin films that overlaps in the thickness direction (however,. That unless all of the plurality is a thermoplastic liquid crystal polymer film) having a structure which is formed by bonding together,
A flexible metal laminated plate characterized in that the thickness of each thermoplastic resin film constituting the insulating layer is ½ or less of the thickness of the insulating layer. The flexible metal laminated plate according to claim 1, wherein the difference in melting points between the plurality of thermoplastic resin films constituting the insulating layer is 150 ° C. or less. The method for manufacturing a flexible metal laminate according to claim 1 or 2.
A method for producing a flexible metal laminated plate, which comprises a step of thermocompression bonding the plurality of thermoplastic resin films to each other in a state where the plurality of thermoplastic resin films are laminated.