JP4224082B2 - Flexible printed circuit board and semiconductor device - Google Patents

Description

  The present invention relates to a flexible printed wiring board and a semiconductor device that are used by being bent in correspondence with the mounting density of electronic components having a higher density. More particularly, the present invention relates to a flexible printed wiring board suitable for mounting and bending an electronic component (such as an IC chip) for driving a flat display panel such as a liquid crystal display device, a plasma display device, and the like. The present invention relates to a semiconductor device mounted with an electronic component.

  As is well known, an electronic component for driving an electronic device is generally incorporated in the electronic device in a state of being mounted on a wiring board including an insulating film and a wiring pattern formed on the surface of the insulating film. This wiring board can be formed, for example, by disposing a conductive metal foil such as a copper foil on the surface of an insulating film and selectively etching the conductive metal foil by a photolithography method. The copper foil used as the conductive metal foil here includes a rolled copper foil and an electrolytic copper foil. However, the rolled copper foil is usually more expensive than the electrolytic copper foil. Electrolytic copper foil is used.

  Electrolytic copper foil is applied to the surface of the rotating drum-shaped cathode by flowing an electrolyte containing copper between the rotating drum-shaped cathode and the anode formed along the cathode, and applying a voltage between the electrodes. Manufactured by depositing copper.

The surface of the rotating drum used as the cathode when manufacturing the electrolytic copper foil as described above is made of titanium, for example, and is polished so that the surface becomes a mirror surface. Therefore, the copper deposition starting surface deposited on the surface of the rotating drum-shaped cathode becomes a mirror surface by transferring the surface state of the rotating drum-shaped cathode, and has a very low surface roughness (Rz), which is usually a shiny surface (S Called the surface). On the other hand, the surface on which the copper is deposited is generally higher in surface roughness (Rz) than the S surface because copper precipitates from the electrolytic solution and grows, resulting in a shiny surface (S surface). This is called the matte surface (M surface).

When manufacturing a wiring board, generally arrange the electrolytic copper foil so that the M surface of the electrolytic copper foil faces the surface of the insulating film, and laminate the electrolytic copper foil and the insulating film to manufacture the base film Then, a photosensitive resin layer is formed on the surface of the S surface of the electrolytic copper foil forming this base film, and this photosensitive resin layer is exposed and developed to form a pattern made of a cured product of the photosensitive resin, Using this pattern as a masking material, the electrolytic copper foil is selectively etched to form a wiring pattern.

The wiring board formed as described above preferably has high adhesion between the insulating film and the wiring pattern formed on the insulating film. The adhesion between the insulating film and the wiring pattern is determined by the wiring pattern. Because it depends on the surface roughness of the M surface of the electrolytic copper foil forming
The M surface of the electrolytic copper foil has been desired to have a certain degree of surface roughness. For this reason, in order to increase the surface roughness of the M surface of the manufactured electrolytic copper foil, the surface roughness of the M surface of the electrolytic copper foil is increased by performing a roughening process such as a bumping process. Treatments such as improving the adhesion have also been performed.

Although roughening the surface of the M surface of the electrolytic copper foil as described above is very preferable for improving the adhesion between the formed wiring pattern and the insulating film, the electrolytic copper foil is selectively etched. When forming a wiring pattern, the M surface having a high surface roughness is not always advantageous. For example, when a very fine wiring pattern with a narrow pitch width is to be formed, the thickness of the electrolytic copper foil to be used cannot be greater than the width of the wiring to be formed. However, if the surface roughness of the M-plane is high, the amount of copper embedded in the insulating film also increases, and copper that is embedded in the insulating film in a short time of etching. It is difficult to completely remove the copper, and if the buried copper is completely removed, problems such as excessive etching of the formed wiring pattern and thinning are likely to occur.

  By the way, when forming using the electrolytic copper foil as described above, as the electrolytic copper foil to be used, an electrolytic copper foil equivalent to the thinnest line width of the wiring pattern to be formed or thinner than the line width is used. For example, when a printed wiring board having an inner lead wiring pitch width of 70 μm (inner lead width is usually about 35 μm), which is generally regarded as a fine pitch printed wiring board, is used. An electrolytic copper foil of ˜40 μm is used.

  However, recently, electronic components have become more dense, and it is necessary to further reduce the wiring pattern formed on a printed wiring board used for mounting such electronic components.

  However, the limit of the wiring pitch width of the printed wiring board that can be manufactured by the manufacturing method using the electrolytic copper foil as described above is 40 μm, and a conventional method for manufacturing a printed wiring board having a narrower wiring pitch width than this. The method for manufacturing a printed wiring board cannot be employed as it is, and it is necessary to newly set all conditions for forming a wiring pattern such as etching conditions and characteristics of the electrolytic copper foil to be used.

For example, when forming a wiring pattern on the surface of an insulating film, when it is intended to form a wiring pattern with a wiring pitch width of less than 40 μm, it is necessary to use an electrolytic copper foil that is thinner than the wiring width to be formed The surface roughness of the M surface of the electrolytic copper foil at this time is a large value as compared with the thickness of the electrolytic copper foil to be used. For this reason, if the contact time with the etching solution is increased in order to completely remove the M-side protrusions of the electrolytic copper foil buried in the insulating film surface by etching, the formed wiring is eroded by the etching solution and becomes thin. As a result, a fine-pitch wiring pattern as planned cannot be formed. Thus, in order to manufacture a printed wiring board having a wiring pitch width of less than 40 μm, it is necessary to newly select an electrolytic copper foil to be used, an etching method and the like.

Under such circumstances, as an electrolytic copper foil capable of forming a wiring pattern having a wiring pitch width of less than 40 μm, for example, Japanese Patent Laid-Open Nos. 9-143785 and 2002-32586 are disclosed. 2), Japanese Unexamined Patent Application Publication No. 2004-162144 (Patent Document 3), Japanese Unexamined Patent Application Publication No. 2004-35918 (Patent Document 4).
), WO2003 / 096776 (Patent Document 5), JP-A-2004-107786 (Patent Document 6), JP-A-2004-137588 (Patent Document 7), JP-A-2004-263289 (Patent Document 8) ), JP 2004-3396558 (Patent Document 9), JP 2005-150265 (Patent Document 10), and the like have been proposed. This low profile electrolytic copper foil is made by adding various additives to the electrolytic solution in which copper is dissolved to lower the surface roughness (Rz) of the M-side of the formed electrolytic copper foil. Depending on the type, the surface roughness (Rz) of the M surface of the obtained electrolytic copper foil can be made lower than the surface roughness (Rz) of the S surface. The low profile electrolytic copper foil thus formed contains various additives in a copper electrolyte solution for depositing copper, and forms a complex when copper is deposited, thereby reducing the particle size of the deposited copper. Thus, the surface profile of the obtained electrolytic copper foil is to be kept low.

  However, the low profile electrolytic copper foil described in the above-mentioned patent document has a small crystal particle diameter of the formed copper, so that the mechanical properties such as the tensile strength of the electrolytic copper foil itself tend to be low. .

  For example, in a flexible printed wiring board on which electronic components for driving a flat panel display such as a liquid crystal display device and a plasma display device are mounted, a hard circuit board is disposed on the back side of the flat panel, and the hard circuit board, A transparent electrode formed on the flat panel is connected by bending a printed wiring board on which electronic components are mounted. The printed wiring board used by bending in this way is subjected to a very large bending stress at the bent part, and wiring formed from electrolytic copper foil with low mechanical properties cannot resist such a large bending stress. There is.

  Recently, with the shift to digital terrestrial broadcasting, flat display panels have become larger due to the introduction of high-definition video. Thus, the flat display panel is gradually increased in size, but the electronic components that drive such a flat display panel are becoming smaller and higher in density, and the number of channels that are driven by one electronic component is increasing. For example, in order to drive a liquid crystal display device of 1280 × 1024 pixels, in a liquid crystal display device currently used, 8 electronic components having 480 effective channels per electronic component are provided on the source side of the liquid crystal display device. Although this liquid crystal display device is driven individually, as part of cost reduction for the spread of the liquid crystal display device, an attempt to reduce the number of electronic components to be arranged by increasing the number of effective channels per electronic component is made. Has been made.

  In a printed circuit board that mounts electronic components that are downsized and have a large number of effective channels per electronic component, the inner lead wiring pitch width for mounting the electronic components is less than 40 μm, and the inner lead lead width is It is considered that it is necessary to make the wire thin to about 20 μm.

  In order to form such a thinned wiring pattern, the electrolytic copper foil used when the wiring pitch width is about 70 μm cannot be used, and the low profile as described above is used. A wiring pattern having a wiring pitch width of less than 40 μm cannot be formed unless an electrolytic copper foil is used.

However, since the wiring formed from the low profile electrolytic copper foil as described above has small copper crystal particles, there is a problem that when the printed wiring board is bent and used, the wiring at the bent portion is often broken. . In order to prevent the wiring formed from such low profile electrolytic copper foil from breaking at the bent portion, for example, the M surface of the low profile electrolytic copper foil is roughened to improve the adhesion with the insulating film and Although it is possible to cope with the problem by jointly preventing disconnection due to the bent portion, it is possible to form a very fine pitch wiring pattern like the above-mentioned low profile electrolytic copper foil and If the foil itself has mechanical strength that can resist bending stress as described above, the strength of the wiring itself will increase even in harsh usage environments such as bending the printed wiring board. It becomes possible.
Japanese Laid-Open Patent Publication No. 9-143785 Japanese Patent Laid-Open No. 2002-32586 JP 2004-162144 JP JP 2004-35918 WO2003 / 096776 JP 2004-107786 A JP 2004-137588 A JP 2004-263289 A JP 2004-3396558 A JP 2005-150265 A

An object of the present invention is to provide a flexible printed wiring board excellent in characteristics such as tensile strength and folding resistance despite the very fine pitch.
Further, the present invention is a flexible printed wiring board having a very fine pitch in which the wiring pitch width of the inner leads, which is the narrowest portion, is less than 40 μm, and the formed wiring itself has high mechanical strength, for example, bent. An object of the present invention is to provide a flexible printed wiring board in which a bent portion and a wiring near a connection terminal are not easily disconnected even when used.

  Another object of the present invention is to provide a semiconductor device for driving a display device in which an electronic component is mounted on the flexible printed wiring board as described above.

The flexible printed wiring board of the present invention is formed of an electrolytic copper foil and a base film having a polyimide layer on the surface of the electrolytic copper foil, the polyimide layer being exposed by etching the electrolytic copper foil, The surface roughness (Rz) of the polyimide surface exposed by selective etching of the electrolytic copper foil is 5 μm or less, and the poly copper exposed by etching the electrolytic copper foil.
A polyimide layer having a light transmittance of more than 67% and not more than 95% is formed, and the pitch width of the inner leads of the wiring pattern is less than 40 μm, and the wiring pattern is folded together with the polyimide layer. Flexible printed wiring board to be used
The wiring pattern includes 50% or more of columnar copper crystal particles having a major axis length of 3 μm or more, and includes copper crystal particles having a major axis of less than 3 μm in a cross-sectional ratio of 50% or less. Columnar copper having a thickness of 15 μm or less and formed of an electrolytic copper foil having an elongation of 5% or more at 25 ° C. , and at least 50% (area ratio) of columnar copper crystal particles forming the wiring pattern The crystal is characterized by having a major axis that is equal to or longer than the thickness of the wiring pattern .

  Furthermore, in the printed wiring board of the present invention, it is preferable that at least a part of the columnar copper crystal particles forming the electrolytic copper foil has a longer diameter longer than the thickness of the wiring pattern, specifically, It is particularly preferable that at least 50% (area ratio) of the copper crystal particles in the cross section of the wiring pattern are copper crystal particles having a long diameter longer than the thickness of the wiring pattern.

A flexible printed wiring board having a wiring pattern formed from an electrolytic copper foil having such copper crystal particles has a very high folding resistance, a bending radius of 0.8 mm, a bending angle of ± 135 degrees, and a bending When measured at 25 ° C. under conditions of a speed of 175 rpm and an applied load of 100 gf / 10 mm ^w , the folding resistance until at least a part of the wiring pattern is broken is usually 100 times or more.

The flexible printed wiring board of the present invention preferably has a polyimide layer formed on the electrolytic copper foil by applying a polyimide precursor to the M surface of the electrolytic copper foil, and the light transmittance of the polyimide layer thus formed. Is preferably more than 67% and 95% or less.

The surface roughness of the exposed surface of such a polyimide layer depends on the surface roughness (Rz) of the M surface of the electrolytic copper foil used, and generally the surface state of the M copper surface of the electrolytic copper foil used or the roughening treatment The surface state of the M surface is transferred. Accordingly, in the present invention, since the surface roughness (Rz) of the M surface of the electrolytic copper foil used is 5 μm or less, such an electrolytic copper foil is laminated and the surface state of the polyimide layer transferred is transferred. The surface roughness (Rz) of the surface is 5 μm or less. The polyimide layer thus formed has high light transmittance, and light is irradiated from the polyimide surface side of the flexible printed wiring board of the present invention when an electronic component is mounted on the flexible printed wiring board of the present invention. In addition, a detection device such as a CCD camera can be arranged on the polyimide surface side of the flexible printed wiring board, and the polyimide layer on which the wiring pattern is not formed by the light irradiated from the polyimide surface side of the flexible printed wiring board of the present invention. By detecting the light beam reflected and returned to the semiconductor chip after transmission, the semiconductor chip arranged on the pattern surface side of the flexible printed wiring board can be accurately positioned.

In addition, the semiconductor device of the present invention is provided on the flexible printed wiring board as described above, 640.
An electronic component of ˜1280 ch / IC is mounted, and is a driver semiconductor device for a display device such as an LCD.

  Such a semiconductor device has a large number of effective channels per electronic component, and therefore, the number of printed wiring boards disposed on the source side of the flat panel display panel can be reduced. And even if this flexible printed wiring board is bent and used, the wiring is not broken at the bending position of the flexible printed wiring board or in the vicinity of the connection terminals.

The wiring pattern formed on the flexible printed wiring board of the present invention has a thickness of 15 μm or less, an elongation at 25 ° C. of 5% or more, and an electrolytic copper mainly composed of columnar copper crystal particles having a major axis length of 3 μm or more. It is formed from foil. Thus, unlike the conventional low profile electrolytic copper foil, the flexible printed wiring board of the present invention has very large copper particles forming the electrolytic copper foil. By increasing the copper crystal particles in this way, the wiring pitch can be increased. It becomes possible to form a wiring pattern having a width of less than 40 μm. The thinning technology of the wiring pattern so far was based on using a low profile electrolytic copper foil by reducing the copper crystal particles forming the electrolytic copper foil, but in the flexible printed wiring board of the present invention, Contrary to these conventional techniques, by making the copper crystals forming the electrolytic copper foil larger than the copper crystal particles forming the conventional electrolytic copper foil, the wiring pitch width is less than 40 μm and the wiring pitch width is very fine. This is based on the finding that a pattern can be formed.

Further, since the particles forming the wiring pattern of the flexible printed wiring board of the present invention are mainly composed of large columnar copper crystals, the tensile strength of the wiring pattern is increased. Elongation increases. Moreover, the M-plane of electrolytic copper foil with such large copper crystals has a surface roughness (Rz) equivalent to or lower than that of the S-plane, but the M-plane is uniformly roughened. By processing, very high adhesiveness is expressed between the polyimide layer.

Therefore, by using such an electrolytic copper foil having a large copper particle diameter, it is possible to form a wiring pattern with a very fine pitch such that the wiring pitch width is less than 40 μm, and thus formed. The wiring pattern itself has very high tensile strength and elongation. In addition, the surface of the electrolytic copper foil is uniformly roughened, a layer made of a polyimide precursor is formed on the surface of the roughened electrolytic copper foil, and a polyimide ring-closing reaction is performed on the surface of the electrolytic copper foil. By carrying out and laminating a polyimide layer, very high adhesiveness appears between this electrolytic copper foil and a polyimide layer. The wiring formed by selectively etching the electrolytic copper foil using the base film composed of the electrolytic copper foil and the polyimide layer has a high mechanical strength and elongation rate, and the polyimide layer. High adhesion strength. Therefore, even if a very fine pitch flexible printed wiring board having a wiring pitch width of less than 40 μm is formed, the mechanical strength of the wiring itself formed on the flexible printed wiring board is high. Even when used under extremely severe conditions such as bending the wiring pattern, the wiring pattern does not peel off from the polyimide layer at the bent portion or the like, and the wiring pattern does not break. Specifically, a flexible printed wiring having a wiring pattern formed of electrolytic copper foil as described above has a bending radius of 0.8 mm, a bending angle of ± 135 degrees, a bending speed of 175 rpm, and an applied load of 100 gf / 10 mm ^w. The folding resistance measured at 0 ° C. until at least a part of the wiring patterns is broken is 100 times or more, and has very high folding resistance.

Furthermore, when forming a wiring pattern using such an electrolytic copper foil having a large copper crystal particle diameter, the cross-sectional shape of the wiring pattern to be formed is set by setting the etching solution, etching conditions, etc. in a suitable range. It can be made as close as possible to a rectangle having an ideal cross-sectional shape.

  And this flexible printed wiring board can make the light transmittance of the polyimide layer which is an insulating film high. For example, the light is irradiated from the polyimide surface side of this flexible printed circuit board, transmitted through this flexible printed circuit board, and then reflected back to the semiconductor chip and detected on the polyimide surface side of this circuit board. By detecting with the apparatus and recognizing the pattern of the image thus detected, the flexible printed wiring board of the present invention can be positioned with high accuracy. Therefore, the flexible printed wiring board of the present invention can accurately position the printed wiring board using the entire formed wiring pattern without forming any special positioning means, and the electronic component can be obtained with higher accuracy. It becomes possible to implement.

  As described above, the flexible printed wiring board of the present invention has a very fine pitch flexible printed wiring whose wiring pitch width at the narrowest part is less than 40 μm, which is considered to be substantially impossible to manufacture by the conventional photolithography method. It is a substrate. In addition, the wiring pattern itself thus formed is excellent in mechanical properties such as tensile strength and elongation, and the adhesion between the wiring pattern and the polyimide layer, which is an insulating film, is very high. It is extremely useful as a very fine pitch flexible printed circuit board used in applications where external stress is applied.

Next, the flexible printed wiring board of the present invention will be specifically described.
The flexible printed wiring board of the present invention is a flexible printed wiring board in which the wiring pitch width (P) in the inner lead having the narrowest pitch width is less than 40 μm, and achieves such a fine pitch. Therefore, in this invention, a flexible printed wiring board is formed using the laminated body of the specific electrolytic copper foil in which a large columnar copper crystal particle occupies most, and the laminated polyimide layer.

  The flexible printed wiring board of the present invention has a wiring pattern in which the wiring pitch width of the narrowest portion is less than 40 μm as described above, and the thickness of the electrolytic copper foil to be used is 15 μm or less, more preferably 5 ~ 12 μm. That is, when a flexible printed wiring board is manufactured by a photolithography method, the thickness of the electrolytic copper foil to be used is selected based on the pitch width of the narrowest portion of the wiring pattern, and the inner portion which is the narrowest portion as in the present invention. When the lead pitch width is less than 40 μm, the width of the finest wiring is usually 20 μm or less, and in order to form a suitable wiring pattern, the thickness of the electrolytic copper foil is the same as the width of the finest wiring. Make it equal or less.

  Unlike conventional low profile electrolytic copper foils with small copper crystal particles, the electrolytic copper foil used in the present invention is formed with a large number of columnar copper crystal particles having a large particle diameter, and the columnar copper crystal particles There are a large number of copper crystal particles having a long diameter of 3 μm or more, preferably 6 μm or more.

  FIG. 1 shows an electron microscope in which a cross section of an inner lead (polyimide layer is dissolved and removed) formed using the above-described electrolytic copper foil is sectioned so that copper crystal particles become clear for each crystal. It is a photograph and its trace figure.

As shown in FIG. 1, the thickness of the electrolytic copper foil used in the present invention is T ₀ , and the major diameters in this electrolytic copper foil are D ₁ , D ₂ , D ₄ , D ₅ , D ₆ , D _7, columnar copper crystal grains represented by D ₈ are present many. The major axis D ₁ of the columnar copper crystal _{grains, D 2, D 4, D} 5, D 6, D 7, D 8 is clearly longer than or equal to T ₀ and the thickness T ₀ of the electrolytic copper foil, thus The wiring pattern forming the flexible printed wiring board of the present invention contains a large number of columnar copper crystal particles having a long diameter longer than the thickness of the wiring pattern.

A wiring pattern formed on the flexible printed wiring board of the present invention, the columnar crystal grains having a (thickness of = wiring pattern) longer diameter than equal to or T ₀ and T ₀ thickness of the electrolytic copper foil The cross section of the wiring pattern usually contains 50% or more in terms of area ratio, and more preferably contains 75% or more.

  Therefore, the electrolytic copper foil used in the present invention contains copper crystal particles whose major axis is less than 3 μm in an amount of 50% or less, preferably 25% or less in terms of the cross-sectional ratio, and the major axis is 3 μm. The copper crystal particles less than 2 are present so as to fill the gaps between the columnar copper crystal particles having a major axis of 3 μm or more.

As described above, the electrolytic copper foil used in the present invention contains columnar copper crystal particles having a major axis of 3 μm or more at a high ratio, and contains such large columnar copper crystal particles at a high ratio. Therefore, the surface roughness (Rz) of the M surface of this electrolytic copper foil is very low, usually 0.8 μm
Hereinafter, it is preferably in the range of 0.1 to 0.6 μm. Moreover, the M surface of this electrolytic copper foil is very smooth, and the surface of this electrolytic copper foil is irradiated with measurement light at an incident angle of 60 ° along the flow direction (MD direction) of this electrolytic copper foil, and the reflection angle When the glossiness [Ga (60 °)] is measured by measuring the intensity of light bounced at 60 °, the glossiness of this electrolytic copper foil shows a value of 600 to 780. The value of the gloss [Ga (60 °)] of the M surface (deposition surface) of this electrolytic copper foil is in contact with the S surface of the electrolytic copper foil (the surface of the drum-type electrode used in the production of the electrolytic copper foil). In many cases, it exhibits a higher value than the surface), and exhibits very high smoothness.

Since the electrolytic copper foil used in the present invention contains long-diameter columnar particles in a high ratio, the particle interface with low bonding force is reduced, and this electrolytic copper foil has high tensile strength. For the electrolytic copper foil used in the present invention, the tensile strength measured at 25 ° C. is usually 33 kgf / mm ² or more, preferably 3
5-40 kgf / mm ² . Tensile strength measured after heating an additional 60 minutes at 180 ° C. is usually at 30 kgf / mm ² or more, preferably 33~40kgf / mm ^2. That is, since the electrolytic copper foil used in the present invention is mainly composed of columnar copper crystal particles having a major axis of 3 μm or more as described above, it has a very high tensile strength.

  The elongation at 25 ° C. of this electrolytic copper foil is 5% or more, preferably 10 to 15%. Further, the elongation after heating at 180 ° C. for 60 minutes is usually 8% or more, preferably 10 to 15%. %. That is, as described above, the copper crystal particles constituting the electrolytic copper foil used in the present invention have a columnar crystal grain size and form having a major axis of 3% or more, and therefore have a very high elongation at room temperature. Along with the development of the rate, the elongation after heating to a high temperature also shows a very high value.

  As described above, the electrolytic copper foil used in the present invention has a very high elongation and tensile strength because the copper crystal particles forming the electrolytic copper foil are columnar crystals, and most of them have a major axis. This is because it is a large columnar crystal of 3 μm or more.

  As described above, since the shape of the copper particles forming the electrolytic copper foil used in the present invention is a large columnar crystal, the tensile strength and the elongation rate are increased, so the electrolytic copper foil was formed using this electrolytic copper foil. Even when the flexible printed wiring board is bent and used, the wiring pattern is not peeled off from the polyimide layer, and the wiring pattern is not disconnected at the bent portion.

The electrolytic copper foil used in the present invention as described above is, for example, a quaternary ammonium salt polymer having a cyclic structure such as diallyldimethylammonium chloride, an organic sulfonic acid such as 3-mercapto-1-propanesulfonic acid, It can be produced by depositing copper from a sulfuric acid-based copper electrolyte containing chlorine ions. In this case, the concentration of the quaternary ammonium salt polymer having a cyclic structure is usually in the range of 1 to 50 ppm, the concentration of the organic sulfonic acid is usually in the range of 3 to 50 ppm, and the chlorine concentration is usually It exists in the range of 5-50 ppm. In addition, the copper concentration of this sulfuric acid-based copper electrolyte is usually in the range of 50 to 120 g / liter, and the free sulfuric acid concentration is usually in the range of 60 to 250 g / liter. The sulfuric acid-based copper electrolyte is used in the present invention by setting the liquid temperature within a range of 20 to 60 ° C. and the current density within a range of usually 30 to 90 A / dm ² to precipitate copper. Electrolytic copper foil can be manufactured. When copper is precipitated under the above conditions using a sulfuric acid-based copper electrolyte having the above composition, most of the precipitated copper becomes columnar copper crystal particles having a major axis of 3 μm or more, and the precipitation finish surface. The surface of (deposition surface = M surface) becomes very smooth.

  On the other hand, conventional low profile electrolytic copper foil is manufactured by adding an additive that forms a complex with copper into the copper electrolyte used when copper is deposited to make the copper deposited particles as small as possible. The surface of the resulting electrolytic copper foil is smooth, and since the particle diameter is small in the low profile electrolytic copper foil, there are many interfaces of copper crystal particles, so the tensile strength of the resulting copper foil Further, the elongation rate and the like are unlikely to be as high as those of the electrolytic copper foil used in the present invention. Further, since the surface of the copper foil is also composed of very fine particles, the surface roughness of the copper foil surface is low, but the glossiness [Ga (60 °)] usually shows a value of less than 600, and the glossiness [ Ga (60 °)] usually does not exceed 600.

In the present invention, a flexible printed wiring board is manufactured using a base film that is a laminate of an electrolytic copper foil and a polyimide layer as described above. In this lamination, a polyimide layer is formed on the surface of the electrolytic copper foil. Form. As described above, the electrolytic copper foil used in the present invention can increase the smoothness of the M surface to the same level as or higher than that of the S surface. A layer may be formed, but usually a polyimide layer is formed on the surface of the M-plane. When a polyimide layer is formed on the M surface of the electrolytic copper foil, it is preferable to form the polyimide layer after surface treatment of the electrolytic copper foil. As an example of the surface treatment, for example, a so-called burn plating process for depositing and adhering copper fine particles on, for example, the M surface of the electrolytic copper foil, and a roughening process and a rust preventive process comprising a cover plating process for fixing the adhering copper fine particles. As well as a coupling agent treatment, and the like.

Of these, the roughening treatment comprises a burn plating treatment and a cover plating treatment. The burn plating treatment is a plating solution having a low copper concentration with a copper concentration of about 5 to 20 g / liter and a free sulfuric acid concentration of about 50 to 200 g / liter. For example, α-naphthoquinone, dextrin,
This is a process of attaching fine copper particles to the M surface of the electrolytic copper foil under conditions of a liquid temperature of 15 to 40 ° C. and a current density of 10 to 50 A / dm ² using glue or thiourea. Further, the covering plating treatment is a treatment for fixing the fine copper particles adhering as described above to the M surface of the electrolytic copper foil. Usually, the copper concentration is about 50 to 80 g / liter, and the free sulfuric acid concentration is 50 to 150 g / liter. using copper plating solution of about l, solution temperature 40 to 50 ° C., is in the process of the deposition surface of the electrolytic copper foil fine particles of copper deposited over a copper plating layer at a current density of 10 to 50 a / dm ² .

Surface treatment is performed as described above, and the surface roughness (Rz) of the deposited surface of the electrolytic copper foil is 5 μm or less,
Preferably, it is adjusted within the range of 0.1 to 3 μm, more preferably within the range of 0.1 to 2 μm. By performing the surface treatment in this manner, the adhesion between the electrolytic copper foil and the polyimide layer is increased. In particular, when the flexible printed wiring board of the present invention is used for mounting an electronic component for driving a flat display panel, the flexible printed wiring board of the present invention needs to be bent and used as described above. By doing this, the formed wiring is not peeled off from the polyimide layer, and it is possible to prevent the wiring from being broken near the bent portion or the connection terminal. In addition, by performing the roughening treatment uniformly as described above, copper does not remain on the surface of the polyimide layer exposed by the etching treatment.

  In this invention, although a flexible printed wiring board is manufactured using the base film which is a laminated body of the above electrolytic copper foil and a polyimide layer, the polyimide layer at this time is a polyimide film previously made into a film shape. It can also be laminated with electrolytic copper foil, or by applying a polyimide precursor to the surface of the electrolytic copper foil deposition surface, and heating the polyimide precursor together with the electrolytic copper foil, the polyimide precursor is electrolytic copper foil. It can also be formed by ring closure on the surface.

The thickness of the polyimide layer thus formed is usually in the range of 12.5 to 75 μm, preferably 20 to 75 μm, particularly preferably 20 to 50 μm. Originally polyimide resin is not a resin with high light transmittance, but by forming the polyimide layer with the above thickness, the light transmittance of the polyimide layer is in the range of more than 67% to 95%. When light is irradiated from the polyimide surface side of the flexible printed wiring board of the invention, the irradiation light is transmitted through the portion where the wiring is not formed, and the irradiation light is not transmitted through the portion where the wiring pattern is formed. The transmitted light that passes through the substrate can be recognized by a detection device such as a CCD camera, and the position of the wiring pattern and the position of the semiconductor chip to be mounted can be recognized, thereby significantly improving the positioning accuracy.

Thus, when pattern recognition is performed using a detection device such as a CCD camera from the polyimide surface side of the flexible printed wiring board, the light transmittance of the polyimide layer exceeds 67% and is 95% or less, preferably 70 to It is desirable to adjust the thickness of the polyimide layer so that it is within the range of 90%.

  In the formation of the flexible printed wiring board of the present invention, when a polyimide layer is formed by pouring and curing the polyimide precursor on the surface of the electrolytic copper foil as described above, no device hole is formed in the polyimide layer. The film carrier on which the polyimide layer is formed as described above becomes a printed wiring board such as a COF having no device holes.

  In the above description, an example in which a polyimide layer is formed using a polyimide precursor is shown. However, the present invention is not limited to this, and after forming a polyimide film in advance and forming a device hole or the like in this polyimide film, electrolysis is performed. It can also be laminated with a copper foil, and a device hole can be formed in the film carrier thus formed, and for example, a TAB tape or the like can be formed.

  By forming a photosensitive resin layer on the surface of the electrolytic copper foil of the base film that is a laminate of the electrolytic copper foil and the polyimide layer formed as described above, and exposing and developing this photosensitive resin layer, A pattern made of a cured photosensitive resin is formed, and the wiring pattern is formed by etching the electrolytic copper foil using this pattern as a masking material.

As shown in FIG. 3, the flexible printed wiring board of the present invention has a wiring pitch width (P) of an inner lead that is the narrowest portion of less than 40 μm, and preferably the wiring pitch width (P) is 20 μm or more. Within the range of less than 40 μm. In the flexible printed wiring board having such a wiring pitch width (P), the lead width (W) of the wiring pattern can be usually set to 8 to 22 μm.

In the conventional method, the wiring pattern cannot be formed so that the wiring pitch width (P) is less than 40 μm. However, by using the electrolytic copper foil as described above, the wiring pitch width (P) is reduced. A very fine pitch wiring pattern of less than 40 μm can be formed.

The wiring pattern having the wiring pitch width (P) as described above is formed by forming a photosensitive resin layer on the surface (usually S surface) of the electrolytic copper foil of the base film, and exposing and developing the photosensitive resin layer. By doing so, it can form by forming the pattern which consists of a hardening body of photosensitive resin, and etching the said electrolytic copper foil by using the pattern formed in this way as a masking material.

  The wiring pattern formed in this way is formed so that the difference between the width of the upper end portion of the wiring pattern and the width of the lower end portion of the wiring pattern, that is, the lower end portion of the wiring pattern in contact with the polyimide layer is small. It is preferable to do. That is, as shown in FIG. 3, it is preferable that the difference between the top width (ILP) of the wiring pattern and the bottom width (ILB) of the wiring pattern is small.

Thus, in order to reduce the difference between the top width (ILT) of the wiring pattern and the bottom width (ILB) of the wiring pattern, an electrolytic solution containing the above-described electrolytic copper foil with a compound having a high etching suppression effect is used. Is preferably used. Here, the compound having a high etching suppression effect includes a heterocyclic compound having a carbonyl group or a carboxyl group, a glycol having a triple bond or a compound in which ethylene oxide is added to an active hydrogen of a glycol having a triple bond, alkyl sarcosine Or at least one compound selected from the group consisting of alkali metal salts of alkyl sarcosine and anhydrides of aromatic carboxylic acids or derivatives thereof, triazole compounds containing nitrogen atoms such as aminotriazole and derivatives thereof, Examples thereof include benzothiazole compounds and derivatives thereof, mercaptobenzothiazole and derivatives thereof, and carboxybenzothiazole and derivatives thereof. These can be used alone or in combination. By adding a compound having a high etching suppression effect as described above to the etching solution, the compound having a high etching suppression effect is preferentially bonded to the newly exposed copper in the etched portion, and this newly exposed compound is exposed. Therefore, the top of the wiring pattern is not excessively etched, and the top width (ILT) and bottom width (ILB) of the formed wiring pattern are not etched. The difference is reduced, and a wiring pattern having an overall cross section close to a rectangle can be formed.

As an etchant used here, an etchant containing ferric chloride or cupric chloride as a main component of the etchant is preferably used.
The flexible printed wiring board formed as described above has a small difference between the width (ILT) of the upper end portion and the width (ILB) of the lower end portion of the wiring pattern, and the cross-sectional shape of the formed wiring pattern is, for example, FIG. As shown in FIG.

  When the cross-sectional shape of the wiring pattern thus formed is rectangular, as shown in FIG. 4, a wide contact area with the bump electrode of the IC can be ensured, and the electronic component can be more reliably mounted.

  The above description is mainly about the inner lead connected to the electronic component. However, according to the above method, the cross-sectional shape of the outer lead can be formed in a substantially rectangular shape as described above.

Further, by performing the etching as described above, as shown in FIG. 5, the cross section of the formed wiring pattern becomes substantially rectangular and the formed wiring pattern is formed linearly. FIG. 5 shows an example of a micrograph of a wiring pattern having a wiring pitch width (P) of 20 μm. The surface of the polyimide layer is exposed between the wiring pattern and the adjacent wiring pattern. In general, the surface state of the M surface of the electrolytic copper foil disposed on the surface of the polyind layer is transferred to the surface of the exposed polyimide layer. Since the surface state of the M surface of the electrolytic copper foil used is transferred, the surface roughness (Rz) of the exposed polyimide layer is usually 5 μm or less, preferably in the range of 0.1 to 1 μm. Is in.

  By adopting the etching method as described above, the wiring pattern formed as shown in FIG. 5 becomes very linear. For example, as shown in FIG. 6, the flexible printed wiring board formed by the conventional method has a trapezoidal cross section, and the formed wiring pattern has low linearity. As described above, since the wiring pitch width (P) cannot be less than 40 μm by the conventional method, the wiring pitch width (P) of the wiring pattern shown in FIG. 6 is 45 μm.

  By appropriately setting the etching conditions in this way, a wiring pattern having a cross-sectional shape closer to a rectangle can be formed. After etching in this manner, the used masking material can be easily removed by alkali cleaning or the like.

  As shown in FIG. 2, the wiring pattern formed in this way is a protective resin so that lead portions such as input outer leads, input inner leads, output inner leads, and output outer leads that are connection terminal portions are exposed. Covered with layers. This protective resin layer may be a solder resist layer obtained by applying and curing a resin using a screen printing technique, or a laminate in which an adhesive resin layer is formed on one surface of a film in a desired shape. It may be a coverlay that has been punched out and adhered to a predetermined location of the wiring pattern.

As described above, the lead portions exposed from the solder resist layer or the coverlay are subjected to plating. The plating process employed here includes a tin plating process, a gold plating process, a nickel-gold plating process, a nickel plating process, a solder plating process, a lead-free solder plating process, a galvanizing process, a copper plating process, and a silver plating process. These plating processes can be performed alone or in combination with a plurality of plating processes. Furthermore, the solder resist layer can be formed or the cover lay can be adhered after the plating treatment is performed before the wiring pattern is covered with the solder resist layer or the cover lay.

The thickness of the plated layer thus formed is usually in the range of 0.1 to 10 μm.
After forming the plating layer and the solder resist layer or the cover lay as described above, as shown in FIG. 2, a semiconductor device can be obtained by mounting an electronic component and sealing with resin.

  Since the polyimide layer constituting the flexible printed circuit board of the present invention is formed very thin, the light transmittance is high and the flexible printed circuit board is transmitted by light transmitted from the polyimide surface side of the flexible printed circuit board. The shape of the wiring pattern formed on the semiconductor device can be recognized, whereby the semiconductor device of the present invention can be manufactured by positioning with very high accuracy and mounting the electronic component.

The electronic component mounted on the flexible printed wiring board of the present invention is preferably a driver arranged in a display device such as an LCD display device or a PDP display device. The driver of such a display device has 128 channels per IC, 256 channels per IC, and 256 channels per IC.
The number of channels gradually increases to 512ch / 1IC, and the flexible printed wiring board of the present invention is suitable for mounting electronic components having an effective channel number of 640ch / 1IC to 1280ch / 1IC. In particular, the flexible printed wiring board of the present invention is suitable for mounting a driver IC for a display device having 1 million or more pixels.

As described above, the driver for driving the flat panel display gradually increases the amount of information processed by one electronic component, but the electronic component itself is light and small. Therefore, the inner lead that forms the electrical connection point with the electronic component needs to have a narrow wiring pitch width corresponding to the bump electrode that is small and formed with high density.

  The flexible printed wiring board of the present invention has the above-described configuration. When the flexible printed wiring board is mounted with an electronic component for driving a flat panel display, for example, as shown in FIG. The electronic component of the flexible printed circuit board is used by being bent between the position where the circuit board is mounted and the output outer lead. When a flexible printed wiring board is bent and used in this way, a large bending stress is applied to the wiring pattern of the bent portion, and stress is concentrated near the connection terminal, and the copper crystal of the wiring board such as the bent portion is used. When the particles are small, cracks are likely to occur, and the breakage of the wiring pattern such as a bent portion often starts from this crack.

  However, when using electrolytic copper foil that is mostly columnar crystals with a crystal diameter of 3 μm or more as used in the present invention, cracks are unlikely to occur in the bent portions, and thus disconnections occur in the bent portions. Hard to do. Furthermore, the electrolytic copper foil used in the present invention has a high tensile strength and elongation rate by adopting the crystal structure as described above, and therefore absorbs bending stress and repetitive stress even in a bent portion where a large bending stress is applied. It is possible to prevent breakage.

About the flexible printed wiring board of the present invention, using a flexible printed wiring board folding resistance testing machine (MIT testing machine), a bending radius of 0.8 mm, a bending angle of ± 135 degrees, a bending speed of 175 rpm, and an applied load of 100 gf / 10 mm ^w When the folding resistance is measured at 25 ° C. under the above conditions, the folding resistance until the wiring pattern formed in the bent portion is ruptured is at least 100 times. In a normal case, the wiring pattern does not break even when 100 diffraction curves are repeated.

  Such excellent folding resistance is due to the columnar copper crystals having a long major axis of 3 μm or more so that the high tensile strength and elongation rate are expressed in the electrolytic copper foil used for forming the wiring pattern as described above. Further, since at least a part of such columnar copper crystal particles are copper crystal particles having a longer diameter than the thickness of the formed wiring pattern, the formed wiring pattern is It is considered that it has very high mechanical characteristics, and the formed wiring pattern and the polyimide layer as a support jointly prevent the wiring pattern from being broken by bending stress.

  The flexible printed wiring board of the present invention can be suitably used for applications in which electronic components are mounted and further bent. Therefore, the flexible printed wiring board of the present invention is particularly preferably used for mounting an electronic component for driving the flat panel display, which is disposed on a flat panel display such as an LCD or a PDP.

〔Example〕
EXAMPLES Next, the present invention will be described in more detail with reference to examples of the present invention, but the present invention is not limited thereto.

Copper concentration 80 g / liter, free sulfuric acid concentration 140 g / liter, 1,3-mercapto-1-propanesulfonic acid concentration 4 ppm, diallyldimethylammonium chloride (Senka Co., Ltd.)
(Product name: Unisense FPA100L) 3ppm, Chlorine concentration 10ppm of sulfuric copper electrolyte,
An electrolytic copper foil having a thickness of 12 μm was produced under the conditions of a liquid temperature of 50 ° C. and a current density of 60 A / dm ² . The surface roughness (Rz) of the S surface of this electrolytic copper foil is 1.2 μm, the surface roughness of the M surface is 0.6 μm, and the glossiness [Gs (60 °)] of the M surface is 650.

The M surface of this electrolytic copper foil was subjected to a roughening treatment comprising a burn plating treatment and a cover plating treatment, and the surface roughness (Rz) of the M surface was adjusted to 1.5 μm. A polyimide precursor varnish containing a commercially available polyamic acid was applied to the matte surface of the electrolytic copper foil thus roughened, and heated to carry out a ring-closing imidization reaction to form a polyimide layer. The substrate film layer thus obtained has a polyimide layer thickness of 40 μm, and the obtained substrate film is a two-layer laminate having an electrolytic copper foil thickness of 12 μm and a polyimide layer thickness of 40 μm. is there. In addition, about the electrolytic copper foil before roughening process used here, the elongation measured at 25 degreeC is 8% according to a conventional method, and the elongation measured after hold | maintaining for 60 minutes at 180 degreeC is 12%. It was a very flexible electrolytic copper foil. Further, this electrolytic copper foil had a tensile strength of 39 kgf / mm ² measured at 25 ° C. according to a conventional method, and the tensile strength measured after holding at 180 ° C. for 60 minutes was 35 kgf / mm ^2. After etching until the thickness of the entire surface of the electrolytic copper foil layer of the base film formed was 8 μm, a photosensitive resin was applied to the surface, and the photosensitive resin layer thus formed was exposed and developed. The wiring pitch width (P) of the inner leads of the developed pattern is 20 μm, and the lead width (W) is 10 μm. The wiring pitch width of the outer leads is 40 μm, and the lead width is 20 μm.

  Using the pattern formed as described above as a masking material, a copper foil is selectively used by using a cupric chloride-based etching solution containing as an additive an azole having only nitrogen atoms as hetero atoms in the ring. Etching was removed.

  The masking material is removed by alkali cleaning the etched base film, and then a solder resist is applied using a screen printing technique so that the inner leads and outer leads are exposed, and dried to form a solder resist layer. Formed.

  Next, an electroless tin plating layer having a thickness of 0.5 μm was formed on the inner lead portion and the outer lead portion exposed from the solder resist layer to obtain the flexible printed wiring board of the present invention.

A semiconductor in which an electronic component is mounted by applying an ultrasonic wave to the inner lead of the flexible printed wiring board obtained in this way, applying an ultrasonic wave by pressing a bonding tool from the polyimide layer side of the flexible printed wiring board, and heating. The device was manufactured.

  When manufacturing as mentioned above, the inner lead part was cut out from the flexible printed wiring board before electroless tin plating. An electron micrograph of the inner lead portion thus formed is shown in FIG. Each wiring was formed in the rectangular cross-sectional shape.

The bottom width (ILB) of the inner lead thus formed is 10 μm, and the top width (ILT) of the inner lead is 10 μm.
The polyimide in this portion was dissolved and removed, the inner lead made of electrolytic copper foil was taken out, and the cross section was observed with an electron microscope. The electron micrograph is shown in FIG. 1, and a trace of the electron micrograph is also shown in FIG.

As shown in FIG. 1, the thickness T ₀ of the inner lead is 8 μm, and in the traced drawing of FIG. 1, D1 to D8 clearly have a longer diameter than the thickness T _{0 of the} inner lead = 8 μm. It was a copper columnar crystal. The area occupied by columnar copper crystals exceeding 8 μm in this cross section was 60%.

Further, in the flexible printed wiring board manufactured as described above, the surface roughness (Rz) of the surface of the polyimide layer in the portion where the wiring pattern is not formed between the wiring patterns is 0.5 μm. The light transmittance of the portion not formed was 80%. In the TAB bonder, a light source is arranged on the polyimide surface side of this flexible printed wiring board, a CCD camera is arranged on the polyimide surface side, and the light transmitted through this flexible printed wiring board is detected, and the semiconductor chip and the flexible printed wiring Positioning with the substrate was possible. Here, the light transmittance is measured using an absorptiometer, that is, an insulating layer (polyimide layer) obtained by etching a conductor is cut out to an appropriate size, and the photometer is perpendicular to the light source. Set and measure as follows. Further, the light transmittance may be in the wavelength region of the light source used for image processing when mounting an IC chip or the like, but in general, a visible region, for example, a region having a wavelength of about 400 to 800 nm is used. However, when the insulating layer is made of, for example, a material having a double bond of polyimide, it has a large absorption at 500 nm or less, and therefore generally has a light transmittance centered on light having a wavelength of 600 to 700 nm. Image recognition processing is detected by a CCD camera.

The flexible printed wiring board manufactured as described above was subjected to a load of 100 gf / 10 mm ^w by using a commercially available MIT test machine, which is a folding resistance test apparatus, with a bending angle of ± 135 degrees and a bending radius of 0.8 mm. When a change in wiring resistance was measured at 25 ° C. under a bending speed of 175 rpm, 13
Disconnected 0 times.

  As shown in FIG. 1, the copper particles in the cross section of the wiring pattern formed on the flexible printed wiring board of the present invention are considered to be suitable for forming a conventional printed wiring board and are widely used. Compared with the copper particles constituting the electrolytic copper foil shown in Fig. 7, the shape is very large, and there are many columnar copper particles having a large particle diameter in the wiring pattern, and these are other columnar shapes in the wiring pattern. It is considered that in combination with the copper particles, the substantially rectangular wiring pattern is imparted with excellent characteristics such as excellent folding resistance and elongation.

  On the other hand, when the precipitated particle size is reduced as in the prior art and a copper foil in which such small copper particles are densely packed is used, for example, as shown in FIG. As the number of grain boundaries of the copper particles is large, the etchant can easily enter from these boundaries, so the side etching of the already etched part proceeds while the wiring pattern is formed by etching. A rectangular wiring pattern is difficult to form, and as shown in FIG. 6, a trapezoidal wiring pattern is easily formed.

As described above, the flexible printed wiring board formed in Example 1 of the present invention has most of the crystal grains of copper forming the wiring pattern as columnar crystals, and the major axis of the columnar crystals is 3 μm or more. Even if the wiring pitch width (P) is less than 40 μm, it is possible to form a wiring pattern having a substantially rectangular cross section, and further, the wiring pattern formed itself is very excellent by containing long diameter copper columnar particles. It shows mechanical properties such as folding resistance.
[Comparative Example 1]
Using an ultra-low roughness electrolytic copper foil (manufactured by Mitsui Kinzoku Kogyo Co., Ltd.) as the electrolytic copper foil, a polyimide precursor varnish is applied to the S surface of this electrolytic copper foil and heated to produce a two-layer laminate. did.

This electrolytic copper foil had an elongation measured at 25 ° C. of 4%, a tensile strength of 33 kgf / mm ² , a surface roughness (Rz) of the S surface of 1.0 μm, and a glossiness [Gs (60 °)] of 370. there were.
A wiring pattern was formed in the same manner as in Example 1 except that this electrolytic copper foil was used, and an electroless tin plating layer of 0.5 μm was formed on the lead portion of the obtained sailing ship pattern.

The thickness of the inner lead was 8 μm. When the cross section was observed, the inner lead was formed of a copper granular crystal having a particle size of almost 100% less than 3 μm.
In the flexible printed circuit board manufactured as described above, the surface roughness (Rz) of the surface of the polyimide layer where the wiring pattern is not formed between the wiring patterns is 1.0 μm, and thus the wiring pattern is formed. The light transmittance of the unexposed portion was 65%.

When the flexible printed wiring board manufactured as described above was subjected to a folding resistance test using an MIT testing machine, it was disconnected 60 times.

  The flexible printed wiring board of the present invention is excellent in folding resistance despite the fine pitch where the pitch width (P) of the inner lead which is the narrowest portion of the wiring is less than 40 μm. Even when the substrate is bent, the wiring formed at the bent portion is not easily broken. And since the light transmittance of the polyimide layer which forms an insulating layer is high, the flexible printed wiring board of this invention recognizes the pattern of the light which permeate | transmits the flexible printed wiring board of this invention. Positioning can be performed. Furthermore, the flexible printed wiring board of the present invention can form the cross-sectional shape of the wiring pattern in a substantially rectangular shape. Therefore, the flexible printed wiring board of the present invention can form wiring with a very high density. Can do.

  In addition, the semiconductor device of the present invention has electronic components mounted on the flexible printed wiring board as described above, and can be particularly suitably used for a use as a source driver semiconductor device for a flat panel display. it can.

FIG. 1 is an electron micrograph showing an example of copper crystal particles in a cross section of a wiring pattern obtained by dissolving and removing a polyimide layer, which is an insulating substrate, from the flexible printed wiring board of the present invention and a diagram obtained by tracing it. FIG. 2 is a diagram schematically showing an example of a cross section of the flexible printed wiring board and the semiconductor device of the present invention. FIG. 3 is a cross-sectional view of the inner lead portion of the flexible printed wiring board of the present invention. FIG. 4 is an enlarged view showing inner lead and bump electrode portions when electronic components are mounted on the flexible printed wiring board of the present invention. The photograph on the left side of FIG. 5 is a plan photograph of the inner lead having a pitch width of 20 μm of the flexible printed wiring board. The photograph on the right side is a cross-sectional view of the inner lead portion of the above-mentioned flexible printed wiring board having a rectangular width of 20 μm. FIGS. 6A and 6B are a plane photograph and a cross-sectional photograph of a wiring pattern formed using a conventionally used electrolytic copper foil. FIG. 7 is a conventional example of an inner lead formed by using an electrolytic copper foil that has been widely used as being most suitable for manufacturing a conventional flexible printed wiring board, and an inner lead electron microscope from which a polyimide layer has been removed. It is an example of a photograph.

Claims (12)

The electrolytic copper foil is formed on a surface of the electrolytic copper foil from a base film having a polyimide layer that is etched to expose the polyimide layer, and the electrolytic copper foil is selectively etched. The surface roughness (Rz) of the exposed polyimide surface is 5 μm or less.
The polyimide layer exposed by etching the electrolytic copper foil has a light transmittance of more than 67% and less than 95%, and the pitch width of the inner leads of the wiring pattern is less than 40 μm. , A flexible printed wiring board used by bending the wiring pattern together with the polyimide layer,
The wiring pattern includes 50% or more of columnar copper crystal particles having a major axis length of 3 μm or more, and includes copper crystal particles having a major axis of less than 3 μm in a cross-sectional ratio of 50% or less. Columnar copper having a thickness of 15 μm or less and formed of an electrolytic copper foil having an elongation of 5% or more at 25 ° C. , and at least 50% (area ratio) of columnar copper crystal particles forming the wiring pattern A flexible printed wiring board, wherein the crystal has a major axis equal to or longer than the thickness of the wiring pattern . The flexible printed wiring board having a wiring pattern formed from the above electrolytic copper foil was measured at 25 ° C. under the conditions of a bending radius of 0.8 mm, a bending angle of ± 135 degrees, a bending speed of 175 rpm, and an applied load of 100 gf / 10 mm ^w. 2. The flexible printed wiring board according to claim 1, wherein the folding resistance until the wiring pattern of the part is broken is 100 times or more. The electrolytic copper foil has a tensile strength at 25 ° C of 33 kgf / mm ² or more, and a tensile strength after heating at 180 ° C for 60 minutes in air at 30 kgf / mm ² or more. A flexible printed wiring board according to item 1.   The flexible printed wiring board according to claim 1, wherein the electrolytic copper foil has an elongation of 8% or more after being heated to 180 ° C for 60 minutes in the air. 2. The flexible printed wiring board according to claim 1, wherein the surface roughness (Rz) of the surface of the electrolytic copper foil laminated with the polyimide layer is 5 [mu] m or less. Precipitation of electrolytic copper foil in which the surface roughness (Rz) of the deposited surface is 0.8 μm or less and the glossiness [Gs (60 °)] of the deposited surface is in the range of 600 to 780. Surface roughness (Rz)
6. The flexible printed wiring board according to claim 5, wherein the substrate is roughened so as to be 5 [mu] m or less. 2. The flexible printed wiring board according to claim 1, wherein a wiring pitch width (P) of inner leads formed on the flexible printed wiring board is less than 40 [mu] m.   The flexible printed wiring board according to claim 1, wherein the polyimide layer has a thickness in the range of 20 to 75 µm.   The flexible printed wiring board according to claim 1 or 8, wherein the polyimide layer is formed by applying a polyimide precursor to the surface of the electrolytic copper foil and curing it by heating. 2. The flexible printed wiring board according to claim 1, wherein the number of effective channels of the electronic component mounted on the flexible printed wiring board is in a range of 640 to 1280 ch / IC.   2. The flexible printed wiring board according to claim 1, wherein the flexible printed wiring board is for mounting a semiconductor chip of a display device having 1 million or more pixels. 12. A semiconductor device for driving a display device, wherein an electronic component having an effective channel number of 640 to 1280 ch / IC is mounted on the flexible printed wiring board according to any one of claims 1 to 11. .

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