JP2006272683A - Flexible metal laminate and flexible printed circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible metal laminate which is used in treatment to push a projection like a bump at high temperatures and can solve a problem caused by the deformation of a resin layer etc., and a flexible printed circuit board using the laminate. <P>SOLUTION: The flexible metal laminate comprises a metal layer 10 and a resin layer 11. The resin layer is divided into two at a place 1/2 in thickness. When the side of a contact surface 13 with the metal layer 10 is made a first specimen 11a and the rest is made a second specimen 11b, a penetration displacement quantity (L1) from the contact surface 13 with the metal layer 10 of the first specimen 11a is smaller than a penetration displacement quantity (L2) from the opposite surface (outermost surface) 12 to the metal layer 10 of the second specimen 11b. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flexible metal laminate and a flexible printed board.

With the spread of mobile phones and liquid crystal monitors, electronic devices are required to be further reduced in size, thickness and functionality. In order to realize this requirement, downsizing and high integration of electronic components are indispensable, but further high-density mounting technology for electronic components is required.
Recently, with the demand for downsizing of driving ICs for liquid crystal displays (LCDs) and multi-outputs of ICs, flip chip bonding, especially COF (Chip On Film), is used for bonding IC (integrated circuit) chips and flexible printed circuit boards. ) Implementation is adopted.
The COF implementation so far uses a modified ILB (Inner Lead Bonder) bonder used in TCP (Tape Carrier Package) implementation.
In order to further reduce the size of drive ICs and increase the number of ICs that can handle multiple outputs, it is essential to reduce the accuracy of the joint position between the IC chip and flexible printed circuit board. COF bonders that can be joined in response have begun to be adopted in recent years.

FIG. 3 is an explanatory view showing an example of a joining method using a COF bonder.
The COF bonder is generally composed of a heating tool 3 for pressing the IC chip 1 and the flexible printed circuit board 2 and a stage 4.
The IC chip 1 includes a plate-like main body 1a and bumps 1b made of gold or the like. In the bump 1b, for example, a plurality of plate-like protrusions are arranged on one side of the main body 1a with a predetermined interval.
The flexible printed board 2 includes a plate-like insulating resin layer 2a and a metal wiring 2b provided on one surface thereof. In addition, the flexible printed circuit board 2 processes and manufactures a flexible metal laminated body. That is, the flexible metal laminate includes an insulating resin layer and a metal layer provided thereon. The flexible printed circuit board 2 is formed by processing the metal layer by plating or the like to form the wiring 2b. Obtainable.

When the IC chip 1 and the flexible printed circuit board 2 are pressed against each other, the flexible printed circuit board 2 is disposed on the stage 4 so that the surface on which the wiring 2b is provided faces up. And it arrange | positions so that the bump 1b side of IC chip 1 may oppose the said wiring 2b.
Next, when the heating tool 3 is pressed from above the IC chip 1 and pressure is applied to the IC chip 1 and the flexible printed circuit board 2, the bumps 1b and the wiring 2b are melted at a high temperature and high pressure to be eutectic. The flexible printed circuit board 2 is joined.
After the joining is completed in this way, an insulating resin called underfill is filled around the bump 1b and the wiring 2b between the IC chip 1 and the flexible printed board 2.

As a flexible metal laminate for producing a flexible printed circuit board 2 used for such applications, a metal foil composed of a non-thermoplastic polyimide layer and a copper foil is laminated, and between these, a non-thermoplastic polyimide layer is used. In addition, a structure in which a thermoplastic polyimide layer having a low glass transition temperature is provided has been proposed (see, for example, Patent Documents 1, 2, and 3).
JP 2004-82719 A JP 2004-322636 A Japanese Patent Laid-Open No. 2004-230670

However, when the flexible printed circuit board 2 is configured using a conventional flexible metal laminate and is to be joined to the IC chip 1 as shown in FIG. 3, the bumps 1b are connected via the wiring 2b under high temperature conditions. Therefore, there is a problem that the resin layer 2a of the soft flexible printed circuit board 2 is deformed.
When the resin layer 2a is deformed or the like, the wiring 2b provided on the resin layer 2a or the bump 1b bonded thereto may sink into the resin layer 2a. Then, the gap between the IC chip 1 and the flexible printed board 2 becomes narrow, and after bonding, the underfill cannot be filled between the IC chip 1 and the flexible printed board 2.
Further, when the bump 1b and the wiring 2b are strongly pressed by point contact while the resin layer 2a is soft, the wiring 2b may be peeled off from the resin layer 2a using these contacts as fulcrums. Then, the peeled wiring 2b may come into contact with the IC chip 1 to cause a short (so-called edge short).

  Therefore, in the present invention, in a flexible metal laminate used for a process of pressing a projection such as a bump under a high temperature condition and a flexible printed circuit board using the same, the resin layer is softened and deformed (hereinafter referred to as deformation). And a flexible printed circuit board using the same.

In order to solve the above problems, the present invention proposes the following means.
The first aspect is a flexible metal laminate having a metal layer and a resin layer,
When the resin layer is divided into two at a thickness of 1/2, the contact surface side with the metal layer is the first sample, and the rest is the second sample,
The penetration displacement amount (L1) of the first sample from the contact surface with the metal layer is smaller than the penetration displacement amount (L2) of the second sample from the surface opposite to the metal layer. This is a flexible metal laminate.
The second aspect is a flexible metal laminate in which the absolute value (dL) of the difference between (L1) and (L2) is 2 μm or more in the flexible metal laminate of the first aspect.
A third aspect is the flexible metal laminate according to the first or second aspect, wherein the resin layer has a penetration displacement (L0) from a contact surface with the metal layer of 10 μm or less.
According to a fourth aspect, in the first to third aspects, the resin layer has a storage elastic modulus (E ′) at 300 ° C. of 1 GPa or more and a glass transition point (Tg) of 300 ° C. or more. It is a flexible metal laminate.
A 5th aspect is a flexible metal laminated body of the aspect in any one of the 1st-4th in which the said resin layer contains a thermoplastic resin soluble in an organic solvent.
A sixth aspect is any one of the first to fifth aspects, wherein the resin layer contains at least one resin selected from the group consisting of a polyimide resin, a polyamideimide resin, a polyetherimide resin, and a polysiloxaneimide resin. It is a flexible metal laminated body of an aspect.
A seventh aspect is the flexible metal laminate according to any one of the first to sixth aspects, wherein the resin layer includes a plurality of layers.
An 8th aspect is a flexible metal laminated body of the aspect in any one of the 1st-7th in which the said metal layer is comprised from metal foil.
A ninth aspect is the flexible metal laminate according to the eighth aspect, wherein the metal foil is composed of one or more selected from the group consisting of a copper foil, a stainless steel foil, an aluminum foil, and a nickel foil.
A tenth aspect is a flexible printed board using the flexible metal laminate of the present invention.

  In the present invention, a flexible metal laminate for use in a process of pressing bumps and other protrusions under high temperature conditions, and a flexible metal that can solve problems associated with deformation of the resin layer in a flexible printed circuit board using the same. A laminated body and a flexible printed circuit board using the same can be provided.

[Flexible metal laminate]
Fig.1 (a) is sectional drawing which showed an example of the structure of the flexible metal laminated body.
The flexible metal laminate of this example is composed of a metal layer 10 and a resin layer 11 laminated on one side thereof.

Examples of the metal constituting the metal layer 10 include copper, stainless steel, aluminum, and steel.
Among these, metal foil is preferable. By using a metal foil, the generation of pinholes can be suppressed. Therefore, wiring defects can be reduced. Therefore, the effect of improving the yield and improving the electrical reliability can be obtained. Further, when the metal foil is used, an excellent effect is obtained that the resin layer and the metal layer (wiring) are hardly separated even when continuously heated to a high temperature.

And it is preferable to use 1 or more types chosen from the group which consists of copper foil, stainless steel foil, aluminum foil, and steel foil among metal foil.
More preferably, the carrier is an electrolytic copper foil that has good etching characteristics and can cope with fine pitching, a rolled copper foil that can improve high flexibility, and a copper foil that can improve the processability of copper foil. And ultrathin copper foil.
The thickness of the metal layer is preferably 3 to 50 μm, more preferably 3 to 35 μm. Furthermore, it is desirable that the thickness is 8 to 18 μm, which can be fine pitched and can be transported by a metal foil alone.

  As shown in FIGS. 1B to 1D, the flexible metal laminate of the present invention divides the resin layer 11 into two layers at a thickness of 1/2, and contacts the metal layer 10 with the contact surface 13 side. Is the first sample 11a and the rest is the second sample 11b, the penetration displacement amount (L1) from the contact surface 13 of the first sample 11a with the metal layer 10 is the second sample 11b. This is characterized in that it is smaller than the penetration displacement amount (L2) from the surface 12 (referred to herein as “outermost surface” for convenience) opposite to the metal layer 10.

In the present invention, the “needle displacement amount” is a 1 mm × 1 mm square needle probe using TMA (thermomechanical analyzer), under the measurement conditions of load: 300 mN, heating rate: 20 ° C./min. The measured displacement of the probe at 300 ° C.
As the TMA, for example, trade name: EXSTAR6100TMA / SS manufactured by SII Nano Technology is preferably used.
Note that the probe type, load, heating rate, measurement temperature, etc. were all determined in consideration of the conditions of the bonding method using the COF bonder as shown in FIG.
That is, the needle-like probe corresponds to a protruding bump. By measuring the penetration displacement amount under such conditions, the state of the resin layer at the time of connection between the bump and the wiring can be represented by a numerical value.

Specifically, for example, the measurement is performed according to the following procedure.
First, two flexible metal laminates having the structure shown in FIG.
Next, as shown in FIG. 1B, the metal layer 10 is removed and only the resin layer 11 is obtained for the two flexible metal laminates. For the removal of the metal layer 10, a chemical etching process or the like can be applied. For example, when the metal layer 10 made of copper foil is used, it can be removed with a ferric chloride solution or the like.

Then, the first sample 11a is obtained from one resin layer 11 as follows. That is, about this resin layer 11, the film thickness (T0) of the resin layer 11 is measured using a micrometer, and the film thickness T1 of the 1/2 is calculated.
Then, while measuring the film thickness with a micrometer, the resin layer 11 is scraped off from the outermost surface 12 side to a film thickness T1 by a method such as mechanical polishing.
Thereby, the 1st sample 11a by the side of the contact surface 13 with the metal layer 10 is obtained.

And about the other resin layer 11, the 2nd sample 11b is obtained as follows.
That is, the resin layer 11 is scraped off from the contact surface 13 side with the metal layer 10 until the film thickness T1 in the same manner as the procedure for obtaining the first sample 11a. Thereby, the second sample 11b on the outermost surface 12 side opposite to the metal layer 10 is obtained.

  Then, after the first sample 11a is left for 24 hours or more in an environment of 23 ± 5 ° C. and 55 ± 5% relative humidity, the probe 20 is pressed from the contact surface 13 side as shown in FIG. Then, the needle displacement is measured up to 400 ° C. while raising the temperature at 20 ° C./min. The amount of needle insertion displacement when the temperature reaches 300 ° C. is defined as needle insertion displacement amount (L1).

  On the other hand, after leaving the second sample 11b for 24 hours or more in an environment of 23 ± 5 ° C. and 55 ± 5% relative humidity, the probe 20 is pushed from the outermost surface 12 side as shown in FIG. Then, the penetration displacement is measured up to 400 ° C. while raising the temperature at 20 ° C./min. The amount of needle insertion displacement when the temperature reaches 300 ° C. is defined as needle insertion displacement amount (L2).

In the present invention, the needle insertion displacement amount (L1) is set to a value smaller than the needle insertion displacement amount (L2). That is, in the resin layer 11, the displacement amount when the needle-like probe 20 is pressed from the contact surface 13 side is smaller than the displacement amount when the probe 20 is pressed from the outermost surface 12 side.
Therefore, when a flexible printed circuit board is manufactured using this flexible metal laminate, on the outermost surface 12 side, while maintaining the flexibility (flexibility) required as a flexible substrate, on the contact surface 13 side. Since the resin layer 11 is not easily deformed even when a needle-like object such as the probe 20 is pressed from the outermost surface 12 side, the bumps are formed from the metal layer 10 under high temperature conditions. Even if it is strongly pressed against the resin layer 11 via, deformation of the resin layer 11 and the like can be suppressed.
As a result, as described above, it is possible to suppress the inconvenience that the wiring and bumps sink into the resin layer 11 and the underfill cannot be filled. In addition, edge shorts where the wiring contacts the IC chip can be suppressed.

It is to be noted that the penetration displacement amount is measured for the first sample 11a and the second sample 11b separately on the outermost surface 12 side and the contact surface 13 side, on the outermost surface 12 side and the contact surface 13 side. This is to accurately evaluate the characteristics.
Without separating the resin layer 11, when the probe 20 is pressed from the outermost surface 12 side and the contact surface 13 side to measure the amount of needle insertion displacement for the entire resin layer 11, a portion corresponding to the first sample 11a, The portions corresponding to the second sample 11b are affected by each other. Therefore, it is not possible to accurately evaluate the characteristics of the outermost surface 12 side and the contact surface 13 side.

  The values of the needle insertion displacement (L1) and the needle insertion displacement (L2) are preferably such that the absolute value (dL) of these differences is 2 μm or more. Preferably it is 5 micrometers or more, More preferably, it is 10 micrometers or more. By setting it as this range, the function on the outermost surface 12 side and the function on the contact surface 13 side are each effectively exhibited, and preferably the flexibility and the effect of suppressing deformation of the resin layer 11 under high temperature conditions are improved. Can be made.

Further, the value of the penetration displacement amount (L1) is preferably 0 to 6 μm, and particularly preferably 0 to 3 μm, from the balance between the characteristics of the outermost surface 12 side and the contact surface 13 side.
The value of the needle insertion displacement (L2) is desirably 2 to 15 μm, and particularly desirably 2 to 10 μm, from the balance between the characteristics of the outermost surface 12 side and the contact surface 13 side.

  The thickness (T0) of the resin layer 11 is preferably 12 to 75 μm, and more preferably 12 to 75 μm, from the viewpoint of bending properties and tensile strength necessary for transporting the flexible metal laminate, and flexibility. 50 μm.

The resin layer 11 having a characteristic that the needle insertion displacement amount (L1) is smaller than the needle insertion displacement amount (L2) can be manufactured, for example, by laminating a plurality of different types of resins. For example, as shown in FIG. 2, the resin layer 11 is composed of a plurality of layers such as a first layer 14 and a second layer 15.
Preferably, for example, one or both of the layer constituting the contact surface 13 and the layer adjacent thereto are constituted by a layer having an action of reducing the penetration displacement amount (hereinafter referred to as “displacement preventing layer” for convenience). The “displacement preventing layer” is a layer that does not constitute the outermost surface 12.

  The displacement prevention layer is made of a resin material having a high “glass dislocation point (Tg)”. Alternatively, it is made of a resin material having a large “storage elastic modulus (E ′) in dynamic viscoelasticity measurement”. In particular, it is desirable to use a resin material having a high glass transition point (Tg) and a large storage elastic modulus (E ′).

The glass transition temperature (Tg) of the resin material constituting the displacement prevention layer is measured as follows, and dynamic viscoelasticity measurement is performed, and the result is a graph of the relationship between temperature and loss coefficient (tan δ). This is the temperature at the peak apex (peak top temperature). In practice, the peak top temperature is automatically detected by the measuring device.
That is, using a forced vibration non-resonant viscoelasticity measuring device (Orientec Co., Ltd., trade name: Leo Vibron), measurement conditions: excitation frequency 11 Hz, static tension 3.0 gf, sample size 0.5 mm (width) × The temperature is raised at a rate of temperature rise of 10 ° C./min from a room temperature and humidity environment at 30 mm (length) × thickness 20 (μm), and the relationship between the temperature and the loss factor is obtained.

In the resin material constituting each layer of the resin layer, for example, when two or more resins having different mass average molecular weights are mixed, there may be two or more peak top temperatures. And it is desirable that at least one point is 300 ° C. or higher.
The higher the glass transition point (Tg) of the resin material constituting the displacement prevention layer is, the more preferable it is, and more preferably the presence of a glass transition point (Tg) of 330 ° C. or higher. Furthermore, it is desirable that a glass transition point (Tg) of 350 ° C. or higher exists.
In addition, when there are a plurality of glass transition points (Tg), it is desirable that all the glass transition points (Tg) be 300 ° C. or higher from the viewpoint of preventing deformation during high temperature treatment.

The storage elastic modulus (E ′) of the resin material constituting the displacement prevention layer is measured at a temperature of 300 ° C. in a dynamic viscoelasticity measurement using a forced vibration non-resonant viscoelasticity measuring device (product name: Leo Vibron). It is a measured value.
The specific measurement conditions are the same as the glass transition point (Tg), the excitation frequency is 11 Hz, the static tension is 3.0 gf, the sample size is 0.5 mm (width) × 30 mm (length) × thickness 20 (μm). The temperature is increased at a temperature increase rate of 10 ° C./min from a room temperature and humidity environment. And the measured value when it becomes 300 degreeC is calculated | required.

  The storage elastic modulus (E ′) is preferably 1 GPa or more, particularly preferably 3 GPa or more. The upper limit value is not particularly limited, but is substantially 10 GPa or less.

The storage elastic modulus (E ′) and the glass transition point (Tg) can be adjusted, for example, by changing the type of resin (chemical structure) or the mass average molecular weight (Mw).
The thickness of the displacement prevention layer is preferably, for example, 2 to 20 μm, and more preferably 5 to 15 μm from the viewpoint of adjusting the penetration displacement (L1) to an appropriate range.

Moreover, it is preferable from the point of heat resistance improvement to make the layer adjacent to the layer which comprises the contact surface 13 into a displacement prevention layer.
In this case, the layer which comprises the contact surface 13 can be manufactured from resin which has the characteristic similar to the material of layers other than the displacement prevention layer shown below. At this time, the thickness of the layer constituting the contact surface 13 is preferably about 2 to 10 m from the viewpoint of exerting the effect of the displacement preventing layer provided adjacent thereto.

  Thus, if the resin layer 11 is comprised from multiple layers, the characteristic control of a flexible metal laminated body will become easy. Preferably, the resin layer 11 is preferably composed of 2 to 5 layers, and 2 to 3 layers are more preferable in consideration of cost reduction such as the resin lamination yield.

The layers other than the displacement prevention layer are desirably relatively soft layers that exhibit flexibility.
For example, the glass transition point (Tg) of the resin material constituting the layers other than the displacement prevention layer is preferably higher to some extent, but is preferably in the range of 300 ° C. or higher.
Further, the storage elastic modulus (E ′) of the resin material constituting the layers other than the displacement prevention layer is 0.1 to 5 GPa, preferably 0.5 to 3 GPa.

In addition, about the resin layer 11 whole, it is desirable from the point of heat resistance improvement to satisfy the following characteristics.
That is, when the entire resin layer 11 is used as a measurement sample, the needle insertion displacement (L0) from the contact surface 13 is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 5 μm or less. Thereby, the deformation | transformation etc. of the resin layer 11 at the time of high temperature can be suppressed more effectively.
As described in the method of measuring the needle insertion displacement amount (L1), the needle insertion displacement amount (L0) is the resin layer 11 after removing the metal layer 10 as a sample for (L0) measurement. And about this sample, it can measure by pressing the probe 20 from the contact surface 13 side like the above-mentioned 1st sample 11a.

Moreover, when the resin layer 11 whole is used as a measurement sample, the storage elastic modulus (E ′) at 300 ° C. is preferably 1 GPa or more, and particularly preferably 3 GPa or more. The upper limit value is not particularly limited, but is substantially 10 GPa or less. Within this range, deformation of the resin layer 11 at a high temperature can be effectively suppressed.
The storage elastic modulus (E ′) at this time can be measured in the same manner as the measurement method for each resin material, using a sample similar to the sample for (L0) measurement. However, in the measurement method for each resin material described above, the thickness of the sample is specified, but when measuring the entire resin layer 11, it is not necessary to change the thickness of the resin layer 11 in particular.

Moreover, since the resin layer 11 is formed by laminating a plurality of different types of resin materials, for example, when the entire resin layer 11 is measured as a measurement sample, a plurality of glass transition points (Tg) may exist. And when it measures as the resin layer 11 whole, it is desirable for the resin layer 11 to have a glass transition point (Tg) of at least 1 point or more and 300 degreeC or more.
More preferably, a glass transition point (Tg) of 330 ° C. or higher exists. Furthermore, it is desirable that a glass transition point (Tg) of 350 ° C. or higher exists.
Further, when there are a plurality of glass transition points (Tg), it is desirable that all the glass transition points (Tg) be 300 ° C. or higher from the viewpoint of preventing deformation during high temperature treatment.
The glass transition point (Tg) can be measured in the same manner as the measurement method for each resin material, using a sample similar to the sample for (L0) measurement. However, in the measurement method for each resin material described above, the thickness of the sample is specified, but when measuring the entire resin layer 11, it is not necessary to change the thickness of the resin layer 11 in particular.

The resin constituting the resin layer 11 is not particularly limited as long as the bending property and the tensile strength necessary for transporting the flexible metal laminate can be obtained and flexibility can be imparted. In the present invention, a thermoplastic resin is preferably used from the viewpoint of processability and flexibility.
Furthermore, it is desirable that the thermoplastic resin be soluble in an organic solvent because operations such as coating during production are easy. Here, “soluble” means that 1% by mass or more dissolves in an organic solvent in a temperature range of room temperature to 100 ° C.

Specific examples include heat-resistant thermoplastic resins such as polyimide resin, polyamideimide resin, polyetherimide resin, polysiloxaneimide resin, polyetherketone resin, and polyetheretherketone resin.
More preferably, it is soluble in an organic solvent, and a dehydration condensation polymerization reaction such as an imidization reaction has been sufficiently completed, a polyimide resin, a polyamideimide resin, a polyetherimide resin, a polysiloxaneimide resin, a polyetherketone resin, Polyether ether ketone resins are desirable.
More preferably, it is a thermoplastic resin made of at least one selected from polyimide resin, polyamideimide resin, polyetherimide resin, and polysiloxaneimide resin.

In addition, the resin which comprises the resin layer 11 can be used 1 type or in mixture of 2 or more types.
Moreover, the mass average molecular weight of resin is selected from the range of 20000-150000, for example.

Moreover, you may comprise one or more layers which comprise the resin layer 11 from a three-dimensional bridge | crosslinking type thermosetting resin in the range which does not impair the effect of this invention.
In that case, a curing accelerator such as an organic peroxide or a Lewis acid compound may be added in order to accelerate the thermosetting of the three-dimensional crosslinkable thermosetting resin layer.

In addition, a phosphate ester compound, a nitrogen ester compound, and a halogenated epoxy resin for imparting flame retardancy can also be added to the resin layer 11.
Moreover, an organic filler, an inorganic filler, etc. can also be added for linear expansion control etc.
However, it is desirable to mix the organic filler and the inorganic filler not in the contact surface 13 side but in the layer on the outermost surface 12 side. Furthermore, it is more desirable to add to the outermost layer constituting the outermost surface 12. When an organic filler and an inorganic filler are blended, the transportability during the manufacturing process of the flexible printed circuit board can be improved.
Among these, inorganic fillers are preferable, and colloidal silica, silicon nitride, talc, titanium oxide, calcium phosphate having an average particle size of 0.005 to 5 μm, and more preferably 0.005 to 2 μm are particularly preferable.
The compounding quantity is 0.1-3 mass parts with respect to 100 mass parts of resin of the layer to add, for example.

Examples of the method for producing the flexible metal laminate include the following methods.
A resin solution dissolved in an organic solvent is applied onto a metal layer such as a copper foil, and the organic solvent is dried to form a first layer.

The organic solvent only needs to be a soluble organic solvent, and the solvent may be used alone or as a mixed solvent of two or more.
For example, pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, acetamide solvents such as N, N-dimethylacetamide and N, N-diethylacetamide, N, N-dimethylformamide, N And polar solvents such as formamide solvents such as N-diethylformamide and sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide. In addition to these relatively high boiling solvents, ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, toluene, xylene aromatic solvents, tetrahydrofuran, etc. Ether solvents such as dioxane, diclime and triglyme can also be used as a mixed solvent.

Thereafter, the above coating and drying operations are repeated to form a resin layer 11 composed of a plurality of layers. In addition, it can also apply | coat continuously to such an extent that mixing does not arise between several layers.
The coating machine is not limited as long as it can be applied according to the desired resin layer thickness. Examples include a coating machine capable of performing continuous coating or the like with a dam type coater, a die coater, a reverse coater, a lip coater, a gravure coater, a comma coater or the like alone or in combination with each coating head according to a desired resin layer thickness.
In application, two or more application heads may be used.

  More preferably, after the resin solution is applied on the metal layer, the initial drying is repeated until the surface of the layer has no tackiness to form the resin layer 11 composed of a plurality of layers, In this method, the organic solvent is removed at a temperature at which the organic solvent can be completely removed under reduced pressure or in an oxygen-free atmosphere so that the heat resistance and the warpage of the flexible metal laminate can be controlled.

[Flexible printed circuit board]
The flexible printed circuit board of the present invention uses the flexible metal laminate of the present invention. For example, in the configuration shown in FIG. 1, the metal layer 10 is obtained by processing the metal layer 10 by plating or the like to obtain a wiring. Can do.

As described above, in the present invention, in a flexible metal laminate used for a process of pressing a protrusion such as a bump under a high temperature condition and a flexible printed circuit board using the same, there are inconveniences associated with deformation of the resin layer, etc. Can be provided, and a flexible printed circuit board using the same.
In other words, bump-like projections are strongly pressed against the resin layer through the metal layer and the metal wiring formed from the metal layer under high-temperature conditions as in the flip-chip bonding method, particularly COF mounting. When used for processing, inconveniences such as deformation of the resin layer can be suppressed. For this reason, it is possible to suppress underfill filling problems and edge short-circuit problems.

  EXAMPLES Examples will be specifically shown below, but the present invention is not limited to these examples.

<Polyimide resin solution: A>
A polyimide resin solution (trade name: Q-VR-FP007, glass transition point 330 ° C., manufactured by PI Engineering Laboratory Co., Ltd.) is dissolved in N-methyl-2-pyrrolidone so as to have a solid content concentration of 12% by mass to obtain a polyimide resin solution. (Hereinafter referred to as “resin solution A”).

<Polyimide resin solution: B>
Polyamideimide resin (manufactured by Toyobo Co., Ltd., trade name: Viromax HR16NN, glass transition point 320 ° C.) was dissolved in N-methyl-2-pyrrolidone so as to have a solid content concentration of 12% by mass, and a polyamideimide resin solution (hereinafter referred to as “polyamideimide resin solution”) And “resin solution B”).

<Polyimide resin solution: C>
Polyamideimide resin (manufactured by Toyobo Co., Ltd., trade name: Viromax N003TM, glass transition point 370 ° C.) was dissolved in N-methyl-2-pyrrolidone so as to have a solid content concentration of 12% by mass, and polyamideimide resin solution C ( Hereinafter, "resin solution C") was obtained.

<Polyimide resin solution: D>
300 g of the polyimide resin solution A and 100 g of the polyamideimide resin solution C were mixed and stirred to obtain a polyimide resin solution D (hereinafter referred to as “resin solution D”).

<Polyimide resin solution: E>
200 g of the polyimide resin solution A and 200 g of the polyamideimide resin solution C were mixed and stirred to obtain a polyimide resin solution E (hereinafter referred to as “resin solution E”).

Next, the flexible metal laminated body was produced according to the following procedure using the resin solution produced above.
In the following description, resin layers manufactured using the resin solutions A to E are referred to as resin layers A to E, respectively.

Example 1
The resin solution C was applied to the roughened surface of electrolytic copper foil (trade name: USLP, manufactured by Nippon Electrolytic Co., Ltd., thickness: 9 μm) so as to have a thickness of 10 μm after the final heat treatment, and dried by heating at 100 ° C. for 10 minutes. Resin layer C was obtained. Next, the resin solution A was applied onto the resin C layer, dried by heating at 120 ° C. for 5 minutes, and then applied twice so as to have a thickness of 30 μm after drying, to obtain a resin layer A. Furthermore, heat treatment was performed at 280 ° C. for 10 hours while raising the temperature from 30 ° C. to 280 ° C. in a nitrogen atmosphere, and a flexible metal laminate having a total thickness of all resin layers of 40 μm was obtained.

Example 2
The resin solution E was applied to the roughened surface of electrolytic copper foil (trade name: USLP, manufactured by Nippon Electrolytic Co., Ltd., thickness: 9 μm) to a thickness of 20 μm after the final heat treatment, and dried by heating at 120 ° C. for 10 minutes. Resin layer E was obtained. Next, the resin solution A was applied onto the resin layer E so as to have a thickness of 20 μm after drying, and was heated and dried at 120 ° C. for 10 minutes to obtain a resin layer A. Furthermore, heat treatment was performed for 18 hours at 300 ° C. for 3 hours while raising the temperature from 30 ° C. to 300 ° C. in a nitrogen atmosphere, and a flexible metal laminate having a total thickness of all resin layers of 40 μm was obtained.

Example 3
The resin solution D is applied to a roughened surface of an electrolytic copper foil (trade name: USLP, manufactured by Nippon Electrolytic Co., Ltd., thickness: 9 μm) to a thickness of 5 μm after drying, and is heated and dried at 120 ° C. for 5 minutes. Resin layer D was obtained. Next, the resin solution E was applied onto the resin layer D so as to have a thickness of 15 μm after drying, and was heated and dried at 120 ° C. for 10 minutes to obtain a resin layer E. Further, the resin solution B was applied on the resin layer E so as to have a thickness of 20 μm after drying, and was dried by heating at 130 ° C. for 10 minutes. Heat treatment was performed for 20 hours at 300 ° C. for 2 hours while raising the temperature from 30 ° C. to 300 ° C. in a nitrogen atmosphere to obtain a flexible metal laminate having a total thickness of all resin layers of 40 μm.

Example 4
The resin solution D is applied to a roughened surface of an electrolytic copper foil (trade name: USLP, manufactured by Nippon Electrolytic Co., Ltd., thickness: 9 μm) to a thickness of 8 μm after drying, and is heated and dried at 120 ° C. for 5 minutes. Resin layer D was obtained. Next, the resin solution E was applied on the resin layer D so as to have a thickness of 13 μm after drying, and was heated and dried at 120 ° C. for 5 minutes. Further, the resin solution B was applied on the resin layer E so as to have a thickness of 19 μm after drying, and was dried by heating at 130 ° C. for 10 minutes. Heat treatment was performed for 20 hours at 300 ° C. for 2 hours while raising the temperature from 30 ° C. to 300 ° C. in a nitrogen atmosphere to obtain a flexible metal laminate having a total thickness of all resin layers of 40 μm.

Comparative Example 1
The resin solution B was applied to a roughened surface of electrolytic copper foil (trade name: F0-WS, manufactured by Furukawa Circuit Foil Co., Ltd., thickness: 9 μm) so as to have a thickness of 30 μm after the final heat treatment. The resin layer B was obtained by heating and drying for minutes. Next, the resin solution C was repeatedly applied onto the resin layer B, dried by heating at 120 ° C. for 5 minutes, and the resin layer C was obtained so as to have a thickness of 10 μm after drying. Furthermore, heat treatment was performed at 280 ° C. for 10 hours while raising the temperature from 30 ° C. to 280 ° C. in a nitrogen atmosphere, and a flexible metal laminate having a total thickness of all resin layers of 40 μm was obtained.

Comparative Example 2
The resin solution D is applied to a roughened surface of electrolytic copper foil (trade name: USLP, manufactured by Nippon Electrolytic Co., Ltd., thickness: 9 μm) to a thickness of 18 μm after drying, and is heated and dried at 130 ° C. for 10 minutes. A hand resin layer D was obtained. Next, the resin solution E was applied on the resin layer D so as to have a thickness of 14 μm after drying, and was heated and dried at 120 ° C. for 5 minutes. Further, the resin solution B was applied on the resin layer E so as to have a thickness of 8 μm after drying, and was heated and dried at 120 ° C. for 5 minutes. Heat treatment was performed for 20 hours at 300 ° C. for 2 hours while raising the temperature from 30 ° C. to 300 ° C. in a nitrogen atmosphere to obtain a flexible metal laminate having a total thickness of all resin layers of 40 μm.

In Table 1, the structure of the resin layer of the flexible metal laminated body of an Example and a comparative example was shown collectively. In addition, the numerical value in a table | surface is a film thickness (unit: micrometer).
For convenience, the first layer, the second layer, and the third layer are shown from the metal foil side, and the types of the resin layers are shown.

  Thus, the physical property value measurement and evaluation of the flexible metal laminated body of an Example and a comparative example which were obtained in this way were performed as follows.

<Evaluation of flexible metal laminate>
1. Needle displacement amount A plurality of flexible metal laminates of each of the examples and comparative examples were prepared, and a sample of a resin layer used for measurement was prepared as follows.

・ (L0) Sample for measurement Remove the copper foil layer with ferric chloride solution from the flexible metal laminate, measure the resin thickness with a micrometer, and then check the amount of penetration from the resin surface adjacent to the metal layer. A sample for measuring (L0) was prepared.

・ (L1) Sample for measurement In the same manner, the resin layer from which the copper foil layer was removed from the flexible metal laminate was measured on the outermost surface side while measuring the resin thickness with a Marumoto Struers Tegra series polishing machine with a micrometer. Was polished into a sample having a thickness of 20 μm.

-(L2) Sample for measurement A sample for measurement was manufactured by polishing in the same manner as the sample for measurement (L1) except that the sample was polished from the contact surface side with the metal layer.

Each of the above three samples was allowed to stand for 24 hours or more in an environment of 23 ± 5 ° C. and 55 ± 5% relative humidity, and then the temperature was raised and the penetration displacement at 300 ° C. was measured.
The (L0) measurement sample and (L1) measurement sample were each measured by pressing the probe from the contact surface side with the metal layer. (L2) The measurement sample was measured by pressing the probe from the outermost surface side.
Measurement conditions are as follows.
Measuring device: manufactured by SII Nano Technology, Inc. Product name: EXSTAR6100TMA / SS, use of a 1 mm × 1 mm square needle-inserted probe, load: 300 mN, heating rate: 20 ° C./min.
The results are shown in Table 2.

2. Storage elastic modulus (E '), glass transition point (Tg)
(L0) The same sample as the measurement sample is prepared, and the storage elasticity at 300 ° C. is used for this sample under the following conditions using a forced vibration non-resonant viscoelasticity measuring device (trade name: Leo Vibron, manufactured by Orientec). The rate (E ′) was measured.
Measurement condition:
Excitation frequency: 11 Hz, static tension: 3.0 gf, sample size: 0.5 mm (width) × 30 mm (length), heating rate: 10 ° C./min, measurement environment conditions: room temperature and humidity.

Similarly, the peak top of the loss coefficient (tan δ) was detected, and the glass transition point (Tg) was obtained.
The results are shown in Table 3.

3. The same linear thermal expansion coefficient (L0) measurement sample as the resin layer was prepared, and this sample was subjected to TMA tensile measurement with a thermomechanical analyzer (trade name: TMA7, manufactured by Vacuum Riko Co., Ltd.), and the average at 50 to 250 ° C. The linear expansion coefficient was measured by an average linear expansion coefficient calculation method according to JIS K7197.
The measurement conditions are as follows. Sample shape: 0.5 cm width × 1.5 cm length, measurement temperature range: 30 → 400 ° C., load: 9.8 mN, heating rate: 10 ° C./min, initial measurement environmental condition: normal temperature and humidity environment.
The results are shown in Table 4.

4). Curling Amount The flexible metal laminates of Examples and Comparative Examples were cut into 70 mm width × 250 mm.
Next, these cut samples were conditioned for 72 hours in a constant temperature and humidity chamber adjusted to an environment of 23 ± 5 ° C./55±5% (humidity). The sample was placed on a flat and smooth glass plate, and the height of the sample curled in an arc shape from the glass surface was measured.
Furthermore, after leaving the flexible metal laminate in a constant temperature oven at 150 ° C. for 24 hours in air, the humidity was adjusted for 72 hours in a constant temperature and humidity chamber adjusted to an environment of 23 ± 5 ° C./55±5% (humidity). The curl amount after standing at 150 ° C. for 24 hours was used.
The results are shown in Table 4.

5. Flip chip bonding (inner lead (ILB))
The metal layers in the flexible metal laminates of Examples and Comparative Examples were subjected to photoresist coating, pattern exposure, development, etching, solder resist coating, and tin plating, and a circuit pattern for flip chip bonding was formed by a photoresist method. The flexible printed circuit board on which this circuit pattern is formed is allowed to stand at 23 ° C. and 55% Rh for 72 hours, and then the flip chip bonder (manufactured by Kabuya Kogyo Co., Ltd.) is used to bond the circuit pattern for flip chip bonding to the IC bump. went.
In addition, the temperature at the time of joining, joining time, and joining pressure were performed on the following conditions.
Circuit board stage temperature: 100 ° C
Tip side tool temperature: 450 ° C
Joining time: 2.5 seconds Joining pressure: 200 mN / mm ²

And the change in the external appearance of a resin layer and the cross-sectional observation of a junction part were performed based on the following evaluation criteria.
The results are shown in Table 4.
<Evaluation criteria>
◯: There was no problem in appearance, and no significant deformation or peeling occurred at the joining site.
Δ: There was no problem in appearance, but although resin subsidence occurred slightly at the joining site, edge short-circuit and lead misalignment did not occur. .
X: There was a problem in appearance, and significant resin sinking, edge short-circuiting, or lead displacement occurred at the joining site.

  As is clear from the results shown in Tables 2 to 4, the flexible metal laminates of the examples in which the penetration displacement satisfies the conditions of the present invention have good results in flip chip bonding properties (inner leads (ILB properties)). Obtained. On the other hand, in the comparative example, the condition of the penetration displacement amount could not be satisfied, and the flip chip bondability (inner lead (ILB property)) was poor.

Fig.1 (a) is sectional drawing which shows an example of the flexible metal laminated body of this invention, and FIG.1 (b)-FIG.1 (d) is explanatory drawing which showed the measurement procedure of the penetration displacement amount. It is sectional drawing which shows the other example of the flexible metal laminated body of this invention. It is explanatory drawing which showed an example of the joining system by a COF bonder.

Explanation of symbols

10 Metal layer 11 Resin layer 11a First sample 11b Second sample 12 Surface opposite to metal layer (outermost surface)
13 Contact surface

Claims (10)

A flexible metal laminate having a metal layer and a resin layer,
When the resin layer is divided into two at a thickness of 1/2, the contact surface side with the metal layer is the first sample, and the rest is the second sample,
The penetration displacement amount (L1) of the first sample from the contact surface with the metal layer is smaller than the penetration displacement amount (L2) of the second sample from the surface opposite to the metal layer. The flexible metal laminated body characterized by the above-mentioned.   The flexible metal laminate according to claim 1, wherein an absolute value (dL) of a difference between the needle insertion displacement (L1) and the needle insertion displacement (L2) is 2 µm or more.   The flexible metal laminate according to claim 1, wherein the resin layer has a penetration displacement (L0) from a contact surface with the metal layer of 10 μm or less.   The flexible metal laminate according to any one of claims 1 to 3, wherein the resin layer has a storage elastic modulus (E ') at 300 ° C of 1 GPa or more and a glass transition point (Tg) of 300 ° C or more. body.   The said resin layer is a flexible metal laminated body as described in any one of Claims 1-4 containing the thermoplastic resin soluble in an organic solvent.   The flexible resin according to claim 1, wherein the resin layer contains at least one resin selected from the group consisting of a polyimide resin, a polyamideimide resin, a polyetherimide resin, and a polysiloxaneimide resin. Metal laminate.   The flexible metal laminate according to claim 1, wherein the resin layer includes a plurality of layers.   The said metal layer is a flexible metal laminated body of any one of Claims 1-7 comprised from metal foil.   The flexible metal laminate according to claim 8, wherein the metal foil is one or more selected from the group consisting of a copper foil, a stainless steel foil, an aluminum foil, and a nickel foil. The flexible printed circuit board using the flexible metal laminated body as described in any one of Claims 1-9.

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