JP7198190B2 - Adhesive composition, coverlay for flexible printed wiring board and flexible printed wiring board - Google Patents

Description

The present disclosure relates to adhesive compositions, coverlays for flexible printed wiring boards, and flexible printed wiring boards.

2. Description of the Related Art In recent years, flexible printed wiring boards have been widely used as electronic devices have become smaller and have higher performance. The flexible printed wiring board includes a base film, a conductive pattern laminated on the base film, and a coverlay laminated on the base film and the conductive pattern. The coverlay comprises a cover film and an adhesive layer laminated to the cover film. As the adhesive composition used for forming this adhesive layer, for example, in Patent Document 1, an acid component (acrylonitrile-butadiene rubber having carboxyl groups at both ends, an aliphatic dicarboxylic acid having 4 to 12 carbon atoms, A flame-retardant adhesive composition containing a polyamideimide resin obtained by reacting an acid and an anhydride of a polycarboxylic acid having an aromatic ring with a diisocyanate or diamine having an aromatic ring, a phosphorus-containing epoxy resin, and a phosphorus compound is described.

WO2010/038644

An adhesive composition according to one aspect of the present disclosure contains a polyamideimide resin, an epoxy resin, and a compound having a triazine ring.

A flexible printed wiring board coverlay according to another aspect of the present disclosure is a flexible printed wiring board coverlay comprising a cover film and an adhesive layer laminated on the cover film, wherein the adhesive layer is formed from an adhesive composition, the adhesive composition containing a polyamideimide resin, an epoxy resin, and a compound having a triazine ring.

A flexible printed wiring board according to yet another aspect of the present disclosure includes a base film, a conductive pattern laminated directly or indirectly on the base film, and a coverlay laminated on the base film and the conductive pattern. wherein the coverlay comprises a cover film and an adhesive layer laminated on the cover film, the adhesive layer is formed from an adhesive composition, contains a polyamideimide resin, an epoxy resin, and a compound having a triazine ring.

FIG. 1 is a schematic cross-sectional view showing a flexible printed wiring board 1 of the present disclosure. FIG. 2 shows No. 2 after the test of ion migration resistance 2 in the example. 2 is a microscope image of FIG. FIG. 3 shows No. 2 after the test of ion migration resistance 2 in the example. 3 is a microscope image of FIG. FIG. 4 shows No. 2 after the test of ion migration resistance 2 in the example. 14 microscopic images.

[Problems to be Solved by the Present Disclosure]
An adhesive layer formed from an adhesive composition is required to have high peel strength and excellent solder heat resistance.

In flexible printed wiring boards, when a voltage is applied between the terminals of a copper circuit in an environment where moisture exists, copper eluted from the anode side precipitates on the cathode side, causing a phenomenon called ion migration in which the circuit is short-circuited. There is a risk. In recent years, with the miniaturization and high performance of electronic devices, the circuit width/inter-circuit distance (L/S) of the flexible printed wiring board has been reduced from 50 μm/50 μm to 25 μm/25 μm and further to 10 μm/10 μm. Pitching is progressing rapidly. As such circuits become finer-pitched, suppression of ion migration is required.

The present disclosure has been made based on the above circumstances, and provides an adhesive composition having high peel strength, excellent solder heat resistance, and excellent ion migration resistance, a coverlay for a flexible printed wiring board, and a flexible printed wiring. The purpose is to provide a board.

[Effect of the present disclosure]
The adhesive composition according to one aspect of the present disclosure, and the flexible printed wiring board coverlay and flexible printed wiring board using the adhesive composition have high peel strength, excellent solder heat resistance, and excellent resistance. Has ion migration properties.

[Description of Embodiments of the Present Disclosure]
First, the embodiments of the present disclosure are listed and described.

An adhesive composition according to one aspect of the present disclosure contains a polyamideimide resin, an epoxy resin, and a compound having a triazine ring.

Since the adhesive composition contains a triazine ring-containing compound as an epoxy curing agent, the adhesive composition has high peel strength, excellent solder heat resistance, and excellent ion migration resistance.

The content of the epoxy resin in the adhesive composition is preferably 20 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the polyamide-imide resin. If the content of the epoxy resin is less than the above lower limit, the solder heat resistance may deteriorate, and if it exceeds the above upper limit, the flexibility may deteriorate.

In the adhesive composition, the content of the compound is preferably 1 part by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the polyamidoimide resin. If the content of the compound is less than the lower limit, curing of the epoxy resin may be insufficient, and the ion migration resistance may decrease. There is

In the adhesive composition, the epoxy resin is preferably a bisphenol A type epoxy resin or a bisphenol F type epoxy resin. When the epoxy resin is one of these resins, the ion migration resistance can be further improved.

The adhesive composition preferably has a glass transition temperature of 85° C. or higher after curing. When the glass transition temperature after curing is within the above range, changes in physical properties of the adhesive can be suppressed even under high-temperature and high-humidity conditions (for example, 85° C. and 85% RH).

The adhesive composition can be suitably used as a coverlay adhesive for flexible printed wiring boards.

A flexible printed wiring board coverlay according to another aspect of the present disclosure is a flexible printed wiring board coverlay comprising a cover film and an adhesive layer laminated on the cover film, wherein the adhesive layer is formed from an adhesive composition, the adhesive composition containing a polyamideimide resin, an epoxy resin, and a compound having a triazine ring.

Since the adhesive layer is formed of the adhesive composition, the flexible printed wiring board coverlay has high peel strength, excellent solder heat resistance, and excellent ion migration resistance.

A flexible printed wiring board according to yet another aspect of the present disclosure includes a base film, a conductive pattern laminated directly or indirectly on the base film, and a coverlay laminated on the base film and the conductive pattern. wherein the coverlay comprises a cover film and an adhesive layer laminated on the cover film, the adhesive layer is formed from an adhesive composition, contains a polyamideimide resin, an epoxy resin, and a compound having a triazine ring.

Since the flexible printed wiring board includes the flexible printed wiring board coverlay, the flexible printed wiring board has high peel strength, excellent solder heat resistance, and excellent ion migration resistance.

[Details of the embodiment of the present disclosure]
The adhesive composition, the flexible printed wiring board coverlay, and the flexible printed wiring board according to the present disclosure will be described in detail below.

<Adhesive composition>
The adhesive composition contains a polyamideimide resin, an epoxy resin, and a compound having a triazine ring. Each component will be described below.

(Polyamideimide resin)
A polyamide-imide resin is a resin having an amide bond and an imide bond in its molecule.

Examples of the polyamide-imide resin include those obtained by reacting a polycarboxylic anhydride with a diisocyanate or a diamine compound. Among them, from the viewpoint of further improving flexibility, an acid component containing acrylonitrile-butadiene rubber having carboxy groups at both ends, an aliphatic dicarboxylic acid having 4 to 12 carbon atoms and a polycarboxylic acid anhydride having an aromatic ring, and an aromatic A polyamide-imide resin obtained by reacting a diisocyanate having a ring or a diamine is preferred. Polyamide-imide resin can be used individually by 1 type or in combination of 2 or more types.

Acrylonitrile-butadiene rubber having carboxy groups at both ends has a repeating unit derived from acrylonitrile and a repeating unit derived from butadiene.

The lower limit of the content of the acrylonitrile-butadiene rubber having carboxyl groups at both ends in all the acid components contained in the polyamide-imide resin is preferably 3 mol %. The upper limit of the content ratio is preferably 10 mol %, more preferably 8 mol %.

Examples of aliphatic dicarboxylic acids having 4 to 12 carbon atoms include linear dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, heptanedioic acid, octanedioic acid, azelaic acid, sebacic acid, undecanedioic acid, and dodecanedioic acid. Aliphatic dicarboxylic acids, branched aliphatic dicarboxylic acids such as 2-methylsuccinic acid, and the like are included. The aliphatic dicarboxylic acids having 4 to 12 carbon atoms can be used singly or in combination of two or more.

The lower limit of the content of the aliphatic dicarboxylic acid having 4 to 12 carbon atoms in the total acid component contained in the polyamideimide resin is preferably 10 mol %, more preferably 20 mol %. The upper limit of the content ratio is preferably 80 mol %, more preferably 60 mol %.

Polycarboxylic anhydrides having aromatic rings include, for example, trimellitic anhydride, pyromellitic dianhydride, ethylene glycol bis-anhydro trimellitate, propylene glycol bis-anhydro trimellitate, 1,4-butanediol alkylene glycol bis-anhydro trimellitate such as bis-anhydro trimellitate, hexamethylene glycol bis-anhydro trimellitate, polyethylene glycol bis-anhydro trimellitate, polypropylene glycol bis-anhydro trimellitate, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4 ,5,8-naphthalenetetracarboxylic dianhydride, 2,3,5,6-pyridinetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 3,3′, 4,4'-diphenylsulfonetetracarboxylic dianhydride, m-terphenyl-3,3',4,4'-tetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 1,1 , 1,3,3,3-hexafluoro-2,2-bis(2,3- or 3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3- or 3,4 -dicarboxyphenyl)propane dianhydride, 2,2-bis[4-(2,3- or 3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 1,1,1,3,3,3 -hexafluoro-2,2-bis[4-(2,3- or 3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 1,3-bis(3,4-dicarboxyphenyl)-1, 1,3,3-tetramethyldisiloxane dianhydride and the like. Polycarboxylic acid anhydrides having an aromatic ring can be used singly or in combination of two or more.

The lower limit of the content of the polycarboxylic acid anhydride having an aromatic ring in all the acid components contained in the polyamide-imide resin is preferably 10 mol %. The upper limit of the content ratio is preferably 87 mol %.

Diisocyanates having an aromatic ring include, for example, diphenylmethane-2,4'-diisocyanate, 3,2'-dimethyldiphenylmethane-2,4'-diisocyanate, 3,2'-diethyldiphenylmethane-2,4'-diisocyanate, 3, 2'-dimethoxydiphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-3,3'-diisocyanate, diphenylmethane-3,4'-diisocyanate, diphenyl ether-4,4'-diisocyanate, benzophenone -4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, m-xylylenediisocyanate, p-xylylenediisocyanate, naphthalene-2, 6-diisocyanate, 4,4'-[2,2bis(4-phenoxyphenyl)propane]diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diisocyanate, 3,3'-diethylbiphenyl-4,4 '-diisocyanate, 3,3'-dimethoxybiphenyl-4,4'-diisocyanate, 3,3'-diethoxybiphenyl-4,4'-diisocyanate and the like. Diamines having an aromatic ring include, for example, diamines corresponding to those exemplified as the above diisocyanates. The diisocyanate or diamine having an aromatic ring can be used singly or in combination of two or more.

The polyamideimide resin can be produced, for example, by the method described in International Publication No. 2010/038644.

A commercial item can also be used for the said polyamide-imide resin. Commercially available products include, for example, "HR Series" manufactured by Toyobo Co., Ltd.

(Epoxy resin)
The epoxy resin is not particularly limited as long as it has at least two epoxy groups in one molecule, and examples thereof include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy, and alicyclic epoxy. . Among these, a bisphenol A type epoxy resin or a bisphenol F type epoxy resin is preferable from the viewpoint of further improving ion migration resistance. An epoxy resin can be used individually by 1 type or in combination of 2 or more types.

The lower limit of the content of the epoxy resin to 100 parts by mass of the polyamide-imide resin in the adhesive composition is preferably 20 parts by mass, more preferably 25 parts by mass, and even more preferably 30 parts by mass. The upper limit of the content is preferably 80 parts by mass, more preferably 75 parts by mass, and even more preferably 70 parts by mass. If the content of the epoxy resin is less than the above lower limit, the solder heat resistance may deteriorate, and if it exceeds the above upper limit, the flexibility may deteriorate.

(Compound having a triazine ring)
The "compound having a triazine ring" includes both a monomer having a triazine ring and a polymer having two or more repeating units containing a triazine ring. The triazine ring includes 1,3,5-triazine ring, 1,2,3-triazine ring and 1,2,4-triazine ring. A compound having a triazine ring can be used singly or in combination of two or more.

Monomers containing a triazine ring include, for example, melamine and thiocyanuric acid.

Polymers having two or more repeating units containing a triazine ring include, for example, melamine resins.

The compound having a triazine ring is preferably a polymer having two or more repeating units containing a triazine ring, more preferably a melamine resin, from the viewpoint of further improving ion migration resistance.

Examples of commercially available melamine resins include "Nikalac MW30" and "Nikalac MX730" manufactured by Sanwa Chemical Co., Ltd.

The lower limit of the content of the compound having a triazine ring with respect to 100 parts by mass of the polyamide-imide resin in the adhesive composition is preferably 1 part by mass, more preferably 2 parts by mass, and even more preferably 3 parts by mass. The upper limit of the content is preferably 80 parts by mass, more preferably 75 parts by mass, and even more preferably 70 parts by mass. If the content of the compound having a triazine ring is less than the above lower limit, the curing of the epoxy resin may be insufficient, and the ion migration resistance may decrease. There is

The lower limit of the content of the compound having a triazine ring with respect to 100 parts by mass of the epoxy resin in the adhesive composition is preferably 1 part by mass, more preferably 3 parts by mass, and even more preferably 6 parts by mass. The upper limit of the content is preferably 150 parts by mass, more preferably 120 parts by mass, and even more preferably 110 parts by mass. If the content of the compound having a triazine ring is less than the above lower limit, the curing of the epoxy resin may be insufficient, and the ion migration resistance may decrease. There is

The lower limit of the total content of the epoxy resin and the compound having a triazine ring with respect to 100 parts by mass of the polyamide-imide resin in the adhesive composition is preferably 30 parts by mass, more preferably 40 parts by mass, and even more preferably 50 parts by mass. The upper limit of the total content is preferably 160 parts by mass, more preferably 150 parts by mass, and even more preferably 145 parts by mass. When the total content of the epoxy resin and the compound having a triazine ring is within the above range, the flexibility can be improved.

The adhesive composition may contain other components as long as the effects of the present disclosure are not impaired. Other components include, for example, flame retardants, antifoaming agents, leveling agents, silane coupling agents and the like.

The lower limit of the glass transition temperature (Tg) of the adhesive composition after curing is preferably 85°C, more preferably 90°C. The upper limit of the glass transition temperature is preferably 170°C, more preferably 160°C. When the glass transition temperature after curing of the adhesive composition is within the above range, changes in physical properties of the adhesive can be suppressed even under high-temperature and high-humidity conditions (for example, 85° C. and 85% RH).

In addition, the glass transition temperature (Tg) of the adhesive composition after curing was determined by preparing a test piece having a width of 10 mm, a length of 50 mm, and a thickness of 20 μm from the cured product of the adhesive composition. Value of inflection point of storage elastic modulus E′ (MPa) measured at a heating rate of 10° C./min and a frequency of 1 Hz with a dynamic viscoelasticity measuring device (DMA) (Hitachi High-Tech Solution Co., Ltd.) with a length of 20 mm is.

The adhesive composition is suitably used as an adhesive for a flexible printed wiring board or an adhesive for a coverlay of a flexible printed wiring board.

<Flexible printed wiring board>
FIG. 1 is a schematic partial cross-sectional view showing a flexible printed wiring board 1 of the present disclosure. The flexible printed wiring board 1 includes a base film 3, a conductive pattern 4 laminated directly or indirectly on the base film 3, and a cover laminated on the base film 3 and the conductive pattern 4 via an adhesive layer 6. and Ray 2.

(base film)
The base film 3 has insulation and flexibility. The base film 3 is mainly composed of synthetic resin. In addition, the "main component" means a component with the highest content ratio, for example, a component with a content ratio of 50% by mass or more. Examples of synthetic resin include polyimide, polyethylene terephthalate, and fluororesin. Among these, polyimide is preferable because it is excellent in insulating properties, flexibility, heat resistance, and the like.

The lower limit of the average thickness of the base film 3 is preferably 5 μm, more preferably 10 μm. The upper limit of the average thickness is preferably 100 µm, more preferably 50 µm. If the average thickness of the base film 3 is less than the above lower limit, the insulating properties and mechanical strength may be insufficient. On the other hand, if the average thickness of the base film 3 exceeds the above upper limit, the printed wiring board may become unnecessarily thick and the flexibility may be insufficient. In addition, "average thickness" means the average value of the thickness measured at arbitrary 10 points.

(Conductive pattern)
The conductive pattern 4 constitutes the circuit of the flexible printed wiring board.

Examples of the main component of the conductive pattern 4 include copper such as oxygen-free copper, aluminum, silver, gold, nickel, alloys thereof, and stainless steel. Among these, copper or a copper alloy is preferred, and copper is more preferred.

The lower limit of the average thickness of the conductive pattern 4 is preferably 1 μm, more preferably 5 μm, and even more preferably 10 μm. The upper limit of the average thickness is preferably 500 µm, more preferably 100 µm, and even more preferably 50 µm. If the average thickness of the conductive pattern 4 is less than the above lower limit, the strength of the conductive pattern 4 may decrease. On the other hand, if the average thickness of the conductive pattern 4 exceeds the above upper limit, the printed wiring board may become unnecessarily thick and the flexibility may be insufficient.

The conductive pattern 4 may further have a surface treatment layer (not shown). The surface treatment layer covers the surface of the conductive pattern 4 and suppresses leakage of conductive components from the conductive pattern 4 or diffusion of reactive components (oxygen, sulfur, etc.) to the conductive component into the conductive pattern 4. It is something to do.

The material of the surface treatment layer is not particularly limited as long as it can suppress the leakage of the conductive component from the conductive pattern 4 or the diffusion of the reactive component into the conductive pattern 4. Examples include metals, resins, ceramics, and mixtures thereof. etc. The surface treatment layer may be a single layer or multiple layers.

(coverlay)
The coverlay 2 in FIG. 1 itself is a flexible printed wiring board coverlay according to an embodiment of the present disclosure. This coverlay 2 comprises a cover film 5 and an adhesive layer 6 laminated on this cover film 5 .

The cover film 5 has insulation and flexibility. Examples of the main component of the cover film 5 include synthetic resins similar to those of the base film 3 described above.

The lower limit of the average thickness of the cover film 5 is preferably 5 μm, more preferably 10 μm. The upper limit of the average thickness is preferably 60 µm, more preferably 50 µm. If the average thickness of the cover film 5 is less than the above lower limit, the insulating properties may be insufficient. On the other hand, if the average thickness of the cover film 5 exceeds the above upper limit, the coverlay 2 may become unnecessarily thick, and the flexibility of the flexible printed wiring board may become insufficient.

The adhesive layer 6 is formed from the adhesive composition described above.

The lower limit of the average thickness of the adhesive layer 6 is preferably 5 μm, more preferably 10 μm. The upper limit of the average thickness is preferably 100 µm, more preferably 75 µm. If the average thickness of the adhesive layer 6 is less than the above lower limit, the adhesiveness between the coverlay 2 and the conductive pattern 4 may be insufficient. On the other hand, if the average thickness of the adhesive layer 6 exceeds the above upper limit, the coverlay 2 may become unnecessarily thick, and the flexibility of the flexible printed wiring board may become insufficient.

[Other embodiments]
It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present disclosure is not limited to the configurations of the above-described embodiments, but is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. be.

For example, the adhesive composition may be used not only as a coverlay adhesive for a flexible printed wiring board, but also as an adhesive for bonding a base film and a conductive pattern of a flexible printed wiring board.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.

<Preparation of adhesive composition>
Adhesive composition No. 1 was prepared by mixing each component shown in Table 1 below according to the formulation shown in Table 1 below. 1-17 were prepared. The components used to prepare each adhesive composition are shown below. In Table 1, "-" indicates that the corresponding component was not used.

[Polyamideimide resin]
Polyamideimide resin 1: Polyamideimide (Toyobo's "HR type"), Mw: 128,000, Mn: 14,000, Tg: 160°C
Polyamideimide resin 2: Polyamideimide (Toyobo's "HR type"), Mw: 100,000, Mn: 20,000, Tg: 225°C

In addition, "weight average molecular weight (Mw)" is polystyrene conversion weight average molecular weight by gel permeation chromatography (GPC). The weight average molecular weight (Mw) and number average molecular weight (Mn) of the polyimideamide resin are values measured by GPC under the following conditions.
Measuring device: waterers 2695 (water company)
Column: GMH-HR-H
Mobile phase: N-methyl-2-pyrrolidone Flow rate: 0.5 mL/min Sample concentration: 1.0 mass%
Sample injection volume: 10 μL
Detector: Suggestion refractometer Reference material: Monodisperse polystyrene

[Epoxy resin]
Epoxy resin 1: Epicoat 828 (Mitsubishi Chemical Corporation)
Epoxy resin 2: Epicoat 807 (Mitsubishi Chemical Corporation)

[Epoxy curing agent]
Epoxy curing agent 1: Nikalac MW30 (Sanwa Chemical Co., Ltd.)
Epoxy curing agent 2: Nikalac MX730 (Sanwa Chemical Co., Ltd.)
Epoxy curing agent 3: Rikashid MH-700 (Shin Nihon Rika Co., Ltd.)
Epoxy curing agent 4: H-4 (Showa Kasei Kogyo Co., Ltd.)
Epoxy curing agent 5: Cursol C11Z-CN (Shikoku Kasei Co., Ltd.)
Epoxy curing agent 6: diaminodiphenylsulfone

Epoxy curing agents 1 and 2 are melamine resins, and epoxy curing agents 3 and 6 are not compounds containing a triazine ring.

[Flame retardants]
Flame retardant 1: SPH-100 (Otsuka Chemical Co., Ltd.)
Flame retardant 2: HCA (Sankosha)

<Evaluation>
Using the adhesive composition prepared above, the glass transition point (Tg), peel strength, solder heat resistance and migration resistance were evaluated according to the following methods.

[Glass transition point (Tg)]
Adhesive composition no. A test piece with a width of 10 mm, a length of 50 mm, and a thickness of 20 μm was prepared from the cured product of No. 1 to 17, and the length between chucks of this test piece was set to 20 mm. was measured at a heating rate of 10° C./min and a frequency of 1 Hz, and the inflection point of the storage elastic modulus E′ (MPa) was defined as the glass transition temperature (Tg) of the adhesive composition after curing. The results are shown in Table 1 below.

[Peel strength]
Adhesive composition No. 1 was applied to a polyimide film having a thickness of 12.5 μm. 1 to 17 were coated so that the thickness of the adhesive layer was 20 μm to prepare a coverlay film. The coverlay film was press-bonded to a rolled copper foil having a thickness of 18 μm under the conditions of 180° C., 60 minutes, and 3 MPa to prepare an evaluation sample. The peel strength (N / cm) when peeling the rolled copper foil from the above coverlay film is based on JIS-K6584-2: 1999 "Adhesive-Peeling adhesive strength test method, Part 2: 180 degree peeling". and measured at a peel speed of 50 mm/min. The results are shown in Table 1 below.

[Solder heat resistance]
Adhesive composition No. 1 was applied to a polyimide film having a thickness of 12.5 μm. 1 to 17 were coated so that the thickness of the adhesive layer was 20 μm to prepare a coverlay film. The coverlay film was press-bonded to a rolled copper foil having a thickness of 18 μm under the conditions of 180° C., 60 minutes, and 3 MPa to prepare an evaluation sample. The evaluation sample was immersed in a solder bath with a temperature difference of 10° C. from 280° C. to 340° C. for 10 seconds, and the board was visually observed. The results are shown in Table 1 below. In Table 1 below, "<280" indicates that a change in appearance was observed when immersed in a solder bath at 280°C.

[Ion migration resistance 1]
Adhesive composition No. 1 was applied to a polyimide film having a thickness of 12.5 μm. 1 to 17 were coated so that the thickness of the adhesive layer was 20 μm to prepare a coverlay film. The above coverlay film was press-bonded to a substrate having a comb-shaped copper circuit formed with a circuit width/inter-circuit distance (L/S) of 10 μm/10 μm under the conditions of 180° C., 60 minutes, and 3 MPa to prepare an evaluation substrate. did. A voltage of 30 V was applied to the evaluation substrate for 500 hours under conditions of 85° C. and 85% RH (relative humidity). Ion migration resistance 1 is "A (good)" when there is no short circuit after 500 hours, and "B (bad)" when a short circuit is observed between 250 hours and less than 500 hours. If a short circuit was observed for more than 250 hours and less than 250 hours, it was evaluated as "C (extremely poor)". The results are shown in Table 1 below.

[Ion migration resistance 2]
Adhesive composition No. 1 was applied to a polyimide film having a thickness of 12.5 μm. 1 to 17 were coated so that the thickness of the adhesive layer was 20 μm to prepare a coverlay film. The above film for coverlay was press-bonded to a board on which a comb-shaped copper circuit was formed with a circuit width/inter-circuit distance (L/S) = 25 µm/25 µm under the conditions of 180°C, 60 minutes, and 3 MPa to prepare a substrate for evaluation. did. A voltage of 32 V was applied to the evaluation substrate under conditions of 110° C. and 85% RH for 24 hours. Migration resistance 2 is measured by observing the evaluation substrate using a digital microscope (VHX-5000) manufactured by Keyence after 24 hours, and if no dendrite indicating copper deposition on the cathode side is observed, "A (good )”, and when dendrites were observed, it was evaluated as “B (bad)”. The results are shown in Table 1 below.

Moreover, adhesive composition No. Microscopic images obtained with 2, 3 and 14 are shown in FIGS. 2-4, respectively.

<Evaluation results>
As shown in Table 1 above, adhesive composition No. 1 containing a polyamideimide resin, an epoxy resin, and a compound having a triazine ring as an epoxy curing agent. It was found that Nos. 1 to 12 are excellent in peel strength and solder heat resistance, and have excellent ion migration resistance. On the other hand, adhesive composition No. 1 containing an epoxy curing agent other than a compound having a triazine ring as an epoxy curing agent. 13 to 17 are adhesive composition Nos. As compared with 1 to 12, it was found that the peel strength was low and the ion migration resistance was inferior.

Moreover, as shown in FIGS. With 2 and 3, no dendrites indicating copper deposition between the circuits were observed. On the other hand, adhesive composition No. When 14 was used, dendrites were observed.

1 flexible printed wiring board 2 coverlay 3 base film 4 conductive pattern 5 cover film 6 adhesive layer

Claims (8)

a polyamide-imide resin;
epoxy resin;
An adhesive composition containing a compound having a triazine ring. The adhesive composition according to claim 1, wherein the content of the epoxy resin is 20 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the polyamideimide resin. 3. The adhesive composition according to claim 1, wherein the content of said compound is 1 part by mass or more and 80 parts by mass or less with respect to 100 parts by mass of said polyamideimide resin. 4. The adhesive composition according to claim 1, 2 or 3, wherein the epoxy resin is a bisphenol A type epoxy resin or a bisphenol F type epoxy resin. The adhesive composition according to any one of claims 1 to 4, which has a glass transition temperature of 85°C or higher after curing. 6. The adhesive composition according to any one of claims 1 to 5, which is used as a coverlay for flexible printed wiring boards. A flexible printed wiring board coverlay comprising a cover film and an adhesive layer laminated on the cover film,
The adhesive layer is formed from an adhesive composition,
A coverlay for a flexible printed wiring board, wherein the adhesive composition contains a polyamideimide resin, an epoxy resin, and a compound having a triazine ring. A flexible printed wiring board comprising a base film, a conductive pattern laminated directly or indirectly on the base film, and a coverlay laminated on the base film and the conductive pattern,
The coverlay comprises a cover film and an adhesive layer laminated on the cover film,
The adhesive layer is formed from an adhesive composition,
A flexible printed wiring board, wherein the adhesive composition contains a polyamideimide resin, an epoxy resin, and a compound having a triazine ring.

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