JP4826196B2 - Release film and circuit board manufacturing method - Google Patents

Description

  The present invention relates to a release film and a method for producing a circuit board.

  In a pressing process for circuit boards such as printed wiring boards, flexible printed wiring boards, and multilayer printed wiring boards, a release film is used to prevent the circuit board from adhering to the backing plate. For example, in the case of a flexible printed circuit board, in order to protect the circuit part of a base material (for example, polyimide film) having a predetermined circuit part, the circuit part is covered with a resin film with an adhesive, and a release film is further laminated. And pressing.

As such a release film, a film composed of a polyphenylene ether resin, a fluorine resin, or the like is used (for example, see Patent Document 1).
However, in such a release film, the resin film with an adhesive protrudes during the pressing process, and a defect may occur at the end of the circuit board.

JP 2004-339491 A

An object of the present invention is to provide a release film that can prevent a coverlay adhesive or the like from exude when a circuit board is manufactured.
It is another object of the present invention to provide a method for manufacturing a circuit board with less occurrence of defects.

Such an object is achieved by the present invention described in the following (1) to (7).
(1) Used when manufacturing a circuit board using a core substrate having a convex circuit portion having an average height A [μm], and the first layer, the second layer, and the third layer are laminated in this order. A release film consisting of
The first layer has a thickness of 7 to 40 μm and is composed of a polyester resin having an elastic modulus at 180 ° C. of 30 to 150 MPa,
The second layer has a thickness of 50 to 100 μm and is composed of a second resin having an elastic modulus at 90 ° C. of 2 to 8 MPa, which is different from the polyester resin.
The third layer has a thickness of 5 to 20 μm, is composed of a third resin made of an olefin resin having a softening point of 120 ° C. or higher and higher than the softening point of the second resin,
When the first layer and the circuit portion are pressed at a pressure of 4 MPa at a temperature lower by 50 ° C. than the melting point of the polyester-based resin, an average height at which the first layer enters the gap between adjacent convex circuit portions is determined. When B [μm]
B / A × 100 = 70% or more of a release film.
(2) The release film according to (1), wherein the polyester-based resin mainly contains a polybutylene terephthalate resin.
(3) The release film according to (2), wherein the polybutylene terephthalate resin is a copolymer of polybutylene terephthalate and polytetramethylene glycol.
(4) The release film according to (3), wherein the content of the polytetramethylene glycol is 5 to 50% by weight of the entire copolymer.
(5) The release film according to any one of (1) to (4), wherein the second resin is an ethylene resin or an acrylic resin.
(6) The release film according to any one of (1) to (5), wherein the circuit board is a flexible circuit board.
(7) A method for producing a circuit board, comprising using the release film according to any one of (1) to (6) above.

ADVANTAGE OF THE INVENTION According to this invention, when manufacturing a circuit board, the exfoliation of an adhesive agent etc. can be prevented and the release film which can reduce the thickness nonuniformity etc. of a circuit board can be provided.
When a specific polybutylene terephthalate resin is included as the polyester resin, the releasability can be particularly improved.
Further, when the viscoelastic modulus at 180 ° C. of the first layer is set to a specific value, the embedding property in the circuit part can be improved.
In addition, according to the present invention, it is possible to provide a method for manufacturing a circuit board with less occurrence of defects and the like.

Hereafter, the manufacturing method of the release film and circuit board of this invention is demonstrated in detail.
The release film of the present invention is used when a circuit board is produced using a core substrate having a convex circuit portion having an average height A [μm], and the first layer, the second layer, and the third layer are used. A release film laminated in this order,
The first layer is made of a polyester resin, the second layer is made of a second resin different from the polyester resin, and the third layer has a higher softening point than the second resin. When the first layer and the circuit portion are pressed at 4 MPa at a temperature lower than the melting point of the polyester resin by 4 MPa, the average height at which the first layer enters the gap between the convex shapes is made of resin. When B [μm], A / B × 100 = 70% (transfer rate) or higher.
Moreover, the manufacturing method of the circuit board of this invention uses the release film as described above.

First, a release film is demonstrated based on suitable embodiment.
As shown in FIG. 1, the release film 10 is formed by laminating a first layer 1, a second layer 2, and a third layer 3 in this order.
Hereinafter, each layer will be described.

(First layer)
The first layer 1 has a function of releasability from the circuit surface side required when manufacturing a circuit board. Moreover, it also has a function of pattern followability that the first layer 1 follows according to the pattern of the circuit portion.
The first layer 1 is made of a polyester resin. Thereby, since the polyester-based resin has high heat resistance and low elasticity, it is possible to reduce the amount of the adhesive layer of the coverlay film that oozes out during the manufacture of the circuit board (particularly the flexible circuit board).

The polyester resin uses a divalent acid such as terephthalic acid as an acid component or a derivative thereof having an ester forming ability, and a glycol having 2 to 10 carbon atoms as a glycol component or other divalent alcohol or ester forming ability. The saturated polyester resin obtained using those derivatives etc. which have this.
Specific examples of the polyester resin include polyalkylene terephthalate resins such as polyethylene terephthalate resin, polybutylene terephthalate resin, polytrimethylene terephthalate resin, and polyhexamethylene terephthalate resin. Among these, polybutylene terephthalate resin is preferable. Thereby, it is possible to improve the releasability in particular.

  The polyester resin may be a polyester copolymer resin copolymerized with other components as necessary. Examples of the copolymerizing component include known acid components, alcohol components, phenol components, derivatives thereof having ester-forming ability, polyalkylene glycol components, and the like.

  Examples of the copolymerizable acid component include a divalent or higher valent aromatic carboxylic acid having 8 to 22 carbon atoms, a divalent or higher valent aliphatic carboxylic acid having 4 to 12 carbon atoms, and a divalent or higher valent carbon number. Examples thereof include 8 to 15 alicyclic carboxylic acids and derivatives thereof having ester forming ability. Specific examples of the copolymerizable acid component include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, bis (p-carbodiphenyl) methaneanthracene dicarboxylic acid, 4-4′-diphenylcarboxylic acid, and 1,2-bis. (Phenoxy) ethane-4,4′-dicarboxylic acid, 5-sodium sulfoisophthalic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, maleic acid, trimesic acid, trimellitic acid, pyromellitic acid, 1,3 -Cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and derivatives thereof having the ability to form esters. These can be used alone or in combination of two or more.

  Examples of the copolymerizable alcohol and / or phenol component include divalent or higher aliphatic alcohols having 2 to 15 carbon atoms, divalent or higher alicyclic alcohols having 6 to 20 carbon atoms, and 6 to 40 carbon atoms. Examples thereof include aromatic alcohols having a valence of 2 or more, or derivatives thereof having phenol and ester forming ability. Specific examples of the copolymerizable alcohol and / or phenol component include ethylene glycol, propanediol, butanediol, hexanediol, decanediol, neopentylglycol, cyclohexanedimethanol, cyclohexanediol, 2,2′-bis ( 4-hydroxyphenyl) propane, 2,2′-bis (4-hydroxycyclohexyl) propane, hydroquinone, glycerin, pentaerythritol, and the like, derivatives having ester forming ability, and cyclic esters such as ε-caprolactone Can be mentioned.

  Examples of the copolymerizable polyalkylene glycol component include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and random or block copolymers thereof, alkylene glycols of bisphenol compounds (polyethylene glycol, polypropylene glycol, polytetramethylene glycol). , And random or block copolymers thereof) modified polyoxyalkylene glycols such as adducts.

  Among such polyester-based copolymer resins, a copolymer of a polyester-based resin and a polyalkylene glycol component is preferable, more specifically, a copolymer of a polyester-based resin and polytetramethylene glycol, more specifically Specifically, a copolymer of polybutylene terephthalate resin and polytetramethylene glycol is preferable. Thereby, it is excellent also in the plating property.

  The content of such other copolymerizable components (especially polytetramethylene glycol) is not particularly limited, but is preferably 5 to 50% by weight, particularly 10 to 40% by weight of the total polyester-based copolymer resin. % Is preferred. If the content is less than the lower limit, the effect of improving embedding may be reduced, and if the content exceeds the upper limit, the effect of improving the releasability may be reduced.

  The first layer 1 is made of an antioxidant, a slip agent, an anti-blocking agent, an antistatic agent, a coloring agent such as a dye and a pigment, an additive such as a stabilizer, an impact resistance such as a fluororesin and silicon rubber, in addition to the polyester resin. An inorganic filler such as a property-imparting agent, titanium oxide, calcium carbonate, or talc may be contained.

  Examples of the method for forming the first layer 1 include known methods such as an air-cooling or water-cooled inflation extrusion method and a T-die extrusion method.

  Although the thickness of such a 1st layer 1 is not specifically limited, 5-40 micrometers is preferable and 7-20 micrometers is especially preferable. When the thickness is within the above range, the embedding property in the circuit portion 41 is particularly excellent.

The viscoelastic modulus at 180 ° C. of the first layer 1 is not particularly limited, but is preferably 10 to 200 MPa, and particularly preferably 30 to 150 MPa. If the viscoelastic modulus is less than the lower limit, the releasability may be lowered, and if the upper limit is exceeded, the embedding may be lowered.
Such a viscoelastic modulus of the first layer 1 can be evaluated by measuring from a normal temperature to 250 ° C. with a dynamic viscoelasticity measuring device, for example, in a tensile mode, a frequency of 1 Hz, and a heating rate of 5 ° C./min.

(Second layer)
The second layer 2 has a cushion function for embedding the first layer 1 (release layer) of the release film in the gap between the adjacent convex circuit portions 41 when the circuit board is manufactured. In addition, it has a function to make the pressure applied to the entire circuit board uniform when manufacturing the circuit board, thereby reducing the generation of voids. Further, when a flexible circuit board is manufactured as a circuit board, the appearance is excellent (particularly, the generation of wrinkles is reduced).
The second layer 2 is composed of a second resin different from the polyester resin. In this case, examples of the second resin include a polyester resin having a composition different from that of the polyester resin constituting the first layer, or a resin other than the polyester resin. Among these, resins other than the polyester resin are preferable.

  Examples of the resin other than the polyester resin include α-olefin polymers such as polyethylene and polypropylene, α-olefin copolymers having ethylene, propylene, butene, pentene, hexene, methylpentene, and the like as copolymer components, Engineering plastics resins such as polyethersulfone and polyphenylene sulfide may be used, and these may be used alone or in combination. Of these, α-olefin copolymers are preferred. Specifically, a copolymer of α-olefin such as ethylene and (meth) acrylic acid ester, a copolymer of ethylene and vinyl acetate, a copolymer of ethylene and (meth) acrylic acid, and those Partially ionically crosslinked products and the like can be mentioned.

Among the second resins as described above, the elastic modulus at 90 ° C. is preferably 10 MPa or less, and particularly preferably 2 to 8 MPa. When the elastic modulus is within the above range, the cushion function particularly when a flexible circuit is produced is excellent. Moreover, the relationship between the height A [μm] of the convex circuit portion 41 described later and the average height B [μm] into which the first layer 1 enters can be easily satisfied.
Such elastic modulus can be evaluated, for example, by measuring from normal temperature to 250 ° C. in a tensile mode, a frequency of 1 Hz, and a heating rate of 5 ° C./min with a dynamic viscoelasticity measuring apparatus.

In addition to the second resin, the second layer 2 may contain a rubber component in order to further improve cushioning properties. Thereby, it can make it easy to the range of the preferable elasticity modulus mentioned later.
Examples of the rubber component include styrene-based thermoplastic elastomers such as styrene-butadiene copolymers and styrene-isoprene copolymers, thermoplastic elastomer materials such as olefin-based thermoplastic elastomers, amide-based elastomers, and polyester-based elastomers, and natural rubber. , Rubber materials such as isoprene rubber, chloroprene rubber and silicon rubber.

  Although content of the said rubber component is not specifically limited, 5-50 weight part is preferable with respect to 100 weight part of said 2nd resin, and 10-40 weight part is especially preferable. When the content is within the above range, the cushioning property can be particularly improved.

  In addition to the second resin, the second layer 2 is made of an antioxidant, a slip agent, an antiblocking agent, an antistatic agent, a coloring agent such as a dye and a pigment, an additive such as a stabilizer, a fluororesin, or a silicone rubber. An impact resistance-imparting agent, an inorganic filler such as titanium oxide, calcium carbonate, or talc may be contained.

  Examples of the method for forming the second layer 2 include known methods such as an air-cooling or water-cooling inflation extrusion method and a T-die extrusion method.

  The thickness of the second layer 2 is not particularly limited, but is preferably 30 to 100 μm, and particularly preferably 50 to 70 μm. When the thickness is less than the lower limit value, the effect of imparting cushioning properties to the release film may be reduced, and when the thickness exceeds the upper limit value, the effect of improving the release property may be reduced. Further, when the thickness is within the above range, the relationship between the height A [μm] of the convex circuit portion 41 and the average height B [μm] into which the first layer 1 enters can be easily satisfied. it can.

  Although the softening temperature of such a 2nd layer 2 is not specifically limited, 50-90 degreeC is preferable and especially 60-80 degreeC is preferable. When the softening temperature is within the above range, the cushioning property is particularly excellent.

(3rd layer)
The third layer 3 has a function of releasability from the contact plate required when manufacturing the circuit board.
The third layer 3 is made of a third resin having a softening point higher than that of the second resin. Thereby, the releasability with a backing plate can be improved.

  Examples of the third resin include 4-methyl-1-pentene resin, 4-methyl-1-pentene, and other α-olefins such as ethylene, propylene, 1-butene, 1-hexene, 1-hexene, Copolymers with α-olefins having 2 to 20 carbon atoms such as octene, 1-decene, 1-tetradecene and 1-octadecene, olefin resins such as polypropylene, and polyesters similar to those used in the first layer 1 Examples thereof include resins.

  The third resin and the polyester-based resin may be the same or different, but are preferably the same. Thereby, it is possible to use the release film 10 without distinguishing between the front and back, thereby reducing the misuse of the front and back of the release film.

  The softening point of the third resin is not particularly limited, but is preferably 100 ° C. or higher, and particularly preferably 120 ° C. or higher. Thereby, in addition to releasability, it can reduce that the volatile component resulting from 3rd resin, or 3rd resin adheres to the contact plate comprised with the SUS board.

  In addition to the third resin, the third layer 3 is made of an antioxidant, a slip agent, an antiblocking agent, an antistatic agent, a coloring agent such as a dye and a pigment, an additive such as a stabilizer, a fluororesin, a silicone rubber and the like. You may contain impact fillers, inorganic fillers, such as a titanium oxide, a calcium carbonate, and a talc.

  Examples of the method for forming the third layer 3 include known methods such as an air-cooling or water-cooled inflation extrusion method and a T-die extrusion method.

  The thickness of the third layer 3 is not particularly limited, but is preferably 30 μm or less, and particularly preferably 5 to 20 μm. If the thickness is less than the lower limit value, the third layer 3 may adhere to the circuit board during pressing, and if the thickness exceeds the upper limit value, the embeddability may deteriorate. Further, when the thickness is within the above range, the relationship between the height A [μm] of the convex circuit portion 41 and the average height B [μm] into which the first layer 1 enters can be easily satisfied. it can.

(Release film)
The first layer 1, the second layer 2, and the third layer 3 may be separately manufactured and then joined with a laminator or the like to obtain the release film 10. A method of obtaining the release film 10 by a method in which the second layer 2 and the third layer 3 are formed by, for example, an air-cooled or water-cooled coextrusion inflation method or a coextrusion T-die method is preferable. Especially, the method of forming into a film by the co-extrusion T die method is especially preferable at the point which is excellent in the thickness control of each layer.
Further, the first layer 1, the second layer 2, and the third layer 3 may be joined as they are, or may be joined via an adhesive layer.

  The total thickness of the release film 10 is not particularly limited, but is preferably 80 to 150 μm, particularly preferably 100 to 130 μm. When the thickness is within the above range, the balance between the cushioning property and the release property is particularly excellent.

  The ratio of the thickness (t1) of the first layer 1 of the release film 10, the thickness (t2) of the second layer 2, and the thickness (t3) of the third layer 3 is not particularly limited. : 8: 1 to 4: 5: 1 are preferable, and 2: 7: 1 to 3: 6: 1 are particularly preferable. Void generation can be particularly suppressed when the ratio is within the above range.

As shown in FIG. 2, the release film 10 of the present invention is used when a circuit board is manufactured using a core substrate 4 having a convex circuit portion 41 having an average height A [μm].
The sheet is sandwiched between a cover plate 7 via a cover lay film 5 composed of a base material layer 51 and an adhesive layer 52, a release film 10, and cushion paper 6 as needed, on and under the core substrate 4, and pressed. Mold. At this time, an uncovered portion 41 a that is not covered with the coverlay film 5 exists in a part of the circuit portion 41 for reasons such as component mounting. The release film 10 is directly pressure-bonded to the uncoated portion 41a.

  As shown in FIG. 3 as a model, the first layer 1 (mold release) of the present invention is formed in the gap 411 of the convex circuit portion 41 having an average height A [μm] adjacent to the uncovered portion 41a. A film 10) is inserted (embedded). However, the height of the first layer 1 to enter differs depending on the difference in the gap between the adjacent circuit portions 41, the first layer 1 is likely to enter the portion where the gap is large, and the first layer 1 is the portion where the gap is small. It is hard to get in. In the present invention, when the core substrate 4 having the circuit portion 41 having such an average height A [μm] is used, the first layer 1 of the release film 10 and the circuit portion 41 are connected to the melting point of the polyester resin. When the average height at which the first layer 1 enters the gap 411 between the adjacent convex circuit portions 41 is B [μm] at a temperature lower than 50 ° C. and pressure of 4 MPa, A / B × 100 = 70% or more. Thereby, when the core substrate 4 is used, there is no protrusion of the adhesive layer 52 and the like, and it becomes possible to reduce unevenness in the thickness of the circuit substrate. Furthermore, it is possible to prevent the gold plating from adhering to the adhesive layer 52 and short-circuiting in the subsequent evaluation with plating.

As described above, when the average height A [μm] of the convex portion of the circuit unit 41 and the average height B [μm] of the first layer 1 enter the above relationship, the adhesive layer 52 and the like protrude. The reason for disappearance is considered as follows.
The adhesive layer 52 of the cover lay film 5 is normally melted and softened by heating up to about 130 ° C. and oozes out from the lateral portion of the film. The adhesive layer 52 that has oozed out adheres to the side surface of the core substrate 4 and the uncoated portion 41a. However, when the release film 10 of the present invention is used, before the adhesive layer 52 oozes out, the release film 10 is spread by the cushion function, and the portion where the adhesive layer 52 oozes out is blocked. Furthermore, since the first layer 1 is embedded in the uncovered portion 41a, the adhesive layer 52 cannot ooze there. Therefore, the part where the adhesive layer 52 oozes out is blocked by the release film 10.
Specifically, A / B × 100 = 80% or more is preferable, and 85-95% is more preferable. When the transfer rate (A / B × 100) is within the above range, the balance between the cushioning property and the embedding property of the release film 10 in the circuit portion 41 is particularly excellent.
The average height B [μm] into which the first layer 1 enters can be measured by, for example, a precision step meter (alpha-step 200) manufactured by Tokyo Electron Limited.

  When such a release film 10 peels off the flexible printed circuit (FPC) and the release film, the release film is taken by the FPC and is torn, or conversely, the FPC is adhered to the release film and the circuit is peeled off. Will not happen.

  Moreover, in the release film 10 of this embodiment, what was comprised by 3 layers of the 1st layer 1, the 2nd layer 2, and the 3rd layer 3 was shown, but this invention is not limited to this, adhesion | attachment Four or more layers such as four layers, five layers, etc. having a layer, a gas barrier layer, etc. may be used.

(Manufacturing method)
Next, the manufacturing method of the circuit board using such a release film 10 is demonstrated in detail based on suitable embodiment.
First, the core substrate 4 forms a predetermined pattern of circuits (circuit portions 41) on both surfaces of the resin film 40. For example, after forming a copper layer on the resin film 40, patterning or the like is performed.
Then, as shown in FIG. 2, the cover lay film 5, the release film 10, and the cushion paper 6 are stacked on the upper and lower sides of the core substrate 4, and the upper and lower sides are sandwiched between the contact plates 7. At this time, the adhesive layer 52 of the coverlay film 5 is disposed on the core substrate 4 side. The first layer 1 of the release film 10 is disposed on the cover lay film 4 side.
And in the state which pinched | interposed the core board | substrate 4, the coverlay film 5, the release film 10, etc. with the contact plate 7, it heats and pressurizes and a circuit board is obtained by press molding.
The heating condition is that the temperature is raised from room temperature to a predetermined temperature (for example, 150 to 200 ° C., particularly preferably 160 to 185 ° C.) in the pressurized state, and the predetermined temperature is 30 to 90 minutes, preferably 45 to 80 minutes. maintain. Next, it is cooled to room temperature. Here, the rate of temperature increase during the temperature increase is not particularly limited, but is preferably 5 to 30 ° C./min, and particularly preferably 8 to 20 ° C./min.
Moreover, although the said pressurization conditions are not specifically limited, 3-10 Mpa is preferable and 4-6 Mpa is especially preferable. Thus, when the release film 10 is pressure-bonded to the core substrate 4, the first layer 1 is embedded in the gap 411 of the circuit portion 41, and A / B × 100 = 70% or more.

  In FIG. 2, an example in which the core substrate 4, the coverlay film 5, the release film 10, and the like are laminated and formed with a pair of patch plates 7 is shown. Specifically, a plurality of combinations of such configurations are used. It is preferable to mold. Thereby, productivity can be improved.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example and a comparative example, this invention is not limited to these Examples.
Example 1
1. Manufacture of release film Polybutylene terephthalate and polytetramethylene glycol copolymer (PBT resin 1, polytetramethylene glycol copolymerization ratio 10%, product number 5505S, Mitsubishi Engineering) Plastics), ethylene-methyl acrylate copolymer (EMMA, part number ACRIFTH WH102, manufactured by Sumitomo Chemical Co., Ltd.) as the second resin constituting the second layer, and polypropylene (third resin constituting the third layer) PP: product number FS2011DG2, softening point 120 ° C., manufactured by Sumitomo Chemical Co., Ltd.) was coextruded with a three-layer die to produce a release film. The thickness of each layer of the obtained release film was the first layer 30 μm, the second layer 80 μm, and the third layer 8 μm. The viscoelastic modulus at 180 ° C. of the first layer was 30 MPa.

2. Manufacture of circuit board Coverlay film (manufactured by Arisawa), the above-mentioned release film, and cushion paper (manufactured by Oji Paper Co., Ltd.) on both sides of a flexible core substrate having a convex circuit portion with an average height of 30 μm And a pair of sandwiched plates with a patch plate, 20 sets were stacked, and the temperature was raised from normal temperature to 175 ° C. at a temperature increase rate of 10 ° C./min at a pressure of 4.0 MPa using a multistage press. And after hold | maintaining for 60 minutes at 175 degreeC, it cooled to normal temperature and obtained the circuit board (flexible circuit board).

(Example 2)
Example 1 was the same as Example 1 except that the following were used as the polyester resin constituting the first layer.
A copolymer of polybutylene terephthalate and polytetramethylene glycol (PBT resin 2, copolymerization ratio of polytetramethylene glycol 20%, product number 5510S, manufactured by Mitsubishi Engineering Plastics) was used. The viscoelastic modulus at 180 ° C. of the first layer was 10 MPa.

(Example 3)
The polyester resin (PBT resin 4) constituting the first layer was the same as Example 1 except that the following were used.
25% by weight of the above-mentioned copolymer of polybutylene terephthalate and polytetramethylene glycol (PBT resin 1, copolymerization ratio of polytetramethylene glycol 10%, product number 5510S, manufactured by Mitsubishi Engineering Plastics), and polybutylene terephthalate A mixture of 75% by weight of resin (PBT resin 3, manufactured by Mitsubishi Engineering Plastics, product number 5020F) was used. The viscoelastic modulus at 180 ° C. of the first layer was 100 MPa.

Example 4
The polyester resin (PBT resin 5) constituting the first layer was the same as Example 1 except that the following were used.
15% by weight of the above-mentioned copolymer of polybutylene terephthalate and polytetramethylene glycol (PBT resin 1, copolymer ratio of polytetramethylene glycol 10%, product number 5510S, manufactured by Mitsubishi Engineering Plastics), polybutylene terephthalate A mixture of 85% by weight of resin (PBT resin 3, manufactured by Mitsubishi Engineering Plastics, product number 5020F) was used. The viscoelastic modulus at 180 ° C. of the first layer was 120 MPa.

(Example 5)
Example 2 was the same as Example 1 except that the resin constituting the second layer was as follows.
EVOH (manufactured by Mitsui DuPont, product number V5716RC) was used as the resin constituting the second layer.

(Example 6)
Example 3 was the same as Example 1 except that the resin constituting the third layer was as follows.
Polyethylene resin (manufactured by Sumitomo Chemical Co., Ltd., product number L211, softening point 100 ° C.) was used as the resin constituting the third layer.

(Comparative Example 1)
Example 1 was repeated except that the resin constituting the first layer was as follows.
Nylon 6 (manufactured by Ube Industries, product number 5033B) was used as the resin constituting the first layer. The viscoelastic modulus at 180 ° C. of the first layer was 250 MPa.

(Comparative Example 2)
Example 3 was the same as Example 1 except that the resin constituting the third layer was as follows.
Polycarbonate resin (manufactured by Mitsubishi Engineering Plastics, product number 7027R, softening temperature 120 ° C.) was used as the resin constituting the third layer.

The following evaluation was performed about the release film and circuit board obtained by each Example and each comparative example. The evaluation items are shown together with the contents. The obtained results are shown in Table 1.
1. Transfer rate (A / B x 100)
The average height B [μm] at which the first layer enters the gap between the circuit portions was measured with a precision step meter (alpha-step 200) manufactured by Tokyo Electron Co., Ltd., and A / B × 100 was evaluated.

2. Release properties (breakage of release layer resin)
The releasability is in accordance with “JPCA standard (design guide manual / single-sided and double-sided flexible printed wiring board / JPCA-DG02, hereinafter abbreviated as JPCA standard)”. The release state of the release film when the circuit board was taken out after the circuit board was manufactured was visually evaluated. Each code is as follows. The evaluation was performed with n = 10.
A: No breakage or the like occurred in all release films.
A: Some of the release films were torn and the rate of occurrence was less than 2.0%.
(Triangle | delta): The tear generate | occur | produced in one part release film and the generation | occurrence | production rate was 2.0% or more.
X: All the release films were torn.

3. Adhesive layer exudation amount Whether or not the circuit board has exudation of the adhesive layer of the cover lay film is determined according to the flow of the cover lay adhesive in 7.5.3.6 of the JPCA standard and the cover coat. It was evaluated in accordance with “No blur”. Each code is as follows. The evaluation was performed with n = 10.
(Double-circle): The flow amount of the adhesive bond layer was less than 150 micrometers in all the circuit boards.
A: The flow amount of the adhesive layer in 7 to 9 circuit boards was less than 150 μm.
(Triangle | delta): The flow amount of the adhesive bond layer was 150 micrometers or more with the circuit board of 4-6 sheets.
X: The flow rate of the adhesive layer was 150 μm or more in 7 to 10 circuit boards.

4). Moldability The moldability was evaluated according to “bubbles in 7.5.3.3 of the JPCA standard”. Each code is as follows. The evaluation was performed with n = 10.
(Double-circle): The void generation rate was less than 2.0% in all the circuit boards.
A: The void generation rate was less than 2.0% on 7 to 9 circuit boards.
(Triangle | delta): The void generation rate was 2.0% or more with the circuit board of 4-6 sheets.
X: The void generation rate was 2.0% or more on 7 to 10 circuit boards.

5). Appearance wrinkle The appearance was evaluated according to “JPCA standard 7.5.7.2 wrinkle”. Each code is as follows. The evaluation was performed with n = 10.
A: The wrinkle generation rate of all circuit boards was less than 2.0%.
A: The wrinkle generation rate of 7 to 9 circuit boards was less than 2.0%.
(Triangle | delta): The wrinkle incidence of 4-6 circuit boards was 2.0% or more.
X: The wrinkle generation rate of 7 to 10 circuit boards was 2.0% or more.

6). Plating property The plating property was evaluated in accordance with "Appearance of JPCA standard 7.5.4 plating (non-defective product having 90% or more of the required plating area)". Each code is as follows. The evaluation was performed with n = 10.
A: All the circuit side surfaces were uniformly plated, and the plating defect rate was 0%.
A: The plating defect rate on the side surfaces of 7 to 9 circuits was less than 2.0%.
(Triangle | delta): The plating defect rate of the 4-6 circuit side surface was 2.0% or more.
X: The plating defect rate of 7 to 10 circuit side surfaces was 2.0% or more.

When manufacturing a circuit board using the release film of Examples 1-6, it was excellent in the mold release property with a circuit board (especially flexible circuit board).
When a circuit board is manufactured using the release films of Examples 1 to 6, as can be seen from Table 1, the amount of the adhesive layer that oozes out can be prevented.
Moreover, when a circuit board was manufactured using the release film of Examples 1-6, there was no generation | occurrence | production of an external wrinkle etc. in the obtained circuit board, and it was excellent also in the moldability.

  The release film of the present invention is useful when producing a circuit board (particularly a flexible circuit board). In other words, it has excellent mold releasability while reducing the appearance of circuit boards (especially flexible circuit boards), reduces the amount of adhesive that is not satisfactory with conventional release films, and further plating Adhesiveness can be improved. Furthermore, it is possible to provide a release film that is superior in tear strength, elongation, tensile strength and cost as compared with conventional release films.

It is sectional drawing which shows an example of the release film of this invention. It is a state figure which shows the state which manufactures a circuit board using the release film of this invention. It is a model figure which shows in a model the state in which a release film enters into the gap | interval of a circuit part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st layer 2 2nd layer 3 3rd layer 4 Core substrate 40 Resin film 41 Circuit part 41a Uncovered part 411 Gap | interval 5 Coverlay film 51 Base material layer 52 Adhesive layer 6 Cushion paper 7 Catch plate 10 Release film

Claims (7)

This is used when a circuit board is manufactured using a core substrate having a convex circuit portion having an average height A [μm], and a first layer, a second layer, and a third layer are laminated in this order. Mold film,
The first layer has a thickness of 7 to 40 μm and is composed of a polyester resin having an elastic modulus at 180 ° C. of 30 to 150 MPa,
The second layer has a thickness of 50 to 100 μm and is composed of a second resin having an elastic modulus at 90 ° C. of 2 to 8 MPa, which is different from the polyester resin.
The third layer has a thickness of 5 to 20 μm, is composed of a third resin made of an olefin resin having a softening point of 120 ° C. or higher and higher than the softening point of the second resin,
When the first layer and the circuit portion are pressed at a pressure of 4 MPa at a temperature lower by 50 ° C. than the melting point of the polyester-based resin, an average height at which the first layer enters the gap between adjacent convex circuit portions is determined. When B [μm]
B / A × 100 = 70% or more of a release film.   The release film according to claim 1, wherein the polyester resin mainly contains a polybutylene terephthalate resin.   The release film according to claim 2, wherein the polybutylene terephthalate resin is a copolymer of polybutylene terephthalate and polytetramethylene glycol.   The release film according to claim 3, wherein the content of the polytetramethylene glycol is 5 to 50% by weight of the entire copolymer.   The release film according to claim 1, wherein the second resin is an ethylene resin or an acrylic resin.   The release film according to claim 1, wherein the circuit board is a flexible circuit board.   A method for producing a circuit board, wherein the release film according to claim 1 is used.

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