JP2004319981A - Transfer sheet for forming wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer sheet for wiring board of superior transfer stability, for a circuit which is superior in chemical resistant characteristics and dimension stability and especially comprises a fine wiring whose line width is 50 μm or below. <P>SOLUTION: A hardened silicone resin layer and a metal foil are laminated in this order on a supporting body such as a resin film. In the transfer sheet for forming wiring board formed in this way, a shrinkage rate X in at least one of an MD direction and a TD direction of the supporting body at 100°C after heating one hour is 0.05%<X<0.5%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a transfer sheet for forming a wiring board, and more particularly, has a long-term stable adhesive force with metal foil, excellent chemical resistance, and excellent dimensional stability, and a circuit width of 50 μm or less. The present invention relates to a transfer sheet for forming a wiring substrate, which can be applied to fine wiring and has excellent storage stability.

  2. Description of the Related Art Conventionally, ceramic wiring boards have been frequently used as high-density wiring boards, for example, high-density multilayer wiring boards used for packages containing semiconductor elements.

  This ceramic wiring board is formed by forming a wiring conductor made of a high melting point metal such as tungsten or molybdenum on an insulating substrate such as alumina, and a concave portion is formed in a part of the insulating substrate. The semiconductor element is housed in the recess, and the recess is hermetically sealed with an appropriate lid to form a package.

  However, since the ceramics constituting the insulating substrate of such a ceramic multilayer wiring board are hard and brittle, chipping or cracking of the ceramics is likely to occur in a manufacturing process or a transporting process, and the hermetic sealing property of the semiconductor element is impaired. Therefore, there was a problem that the yield was low. In addition, a multilayer ceramic wiring board is manufactured by printing a metallized ink on a green sheet before sintering, laminating and sintering the printed sheet, and in the manufacturing process, firing at a high temperature. Due to firing shrinkage, there is a problem that the obtained substrate is liable to be deformed such as warpage and dimensional variation, etc., and it is sufficient for ultra-high density circuit boards and flip chips with strict substrate flatness requirements. There was a problem that can not respond to.

  As a means for solving these problems, a method using a transfer sheet for forming a wiring board (for example, see Patent Document 1) has been proposed. This method uses a configuration in which a photocurable adhesive layer is provided on a resin film, and a metal layer is adhered on the photocurable adhesive layer. A copper foil (thickness: 9 μm, 12 μm) is laminated with an ultraviolet-curable acrylic or epoxy adhesive having an adhesive force of 150 g / 20 mm to 400 g / 20 mm, and a photoresist is coated on the copper foil and dried, and then dried. A fine pattern conductor circuit is formed on a copper foil by exposure and development through a mask, and after forming a transfer sheet, ultraviolet rays are irradiated from the copper foil side to cure the adhesive on the exposed portion of the adhesive layer and reduce the adhesive strength. An organic resin insulating sheet is overlaid on the circuit forming side of the transfer sheet and laminated by heating and pressing. Thereafter, ultraviolet light is irradiated from the PET film side to reduce the adhesive strength of the conductive circuit forming portion to zero, and then the PET film is peeled off to form a wiring board. This is a method of heating and transferring a conductive circuit to an insulating substrate, and is excellent in that the insulating substrate does not come into contact with various chemicals and does not affect the characteristics of the insulating substrate.

  However, the adhesive is semi-cured, that is, the adhesive force with the copper foil gradually changes due to unreacted, and when using it, it is necessary to optimize the amount of UV exposure each time and further optimize the curing conditions etc. There is a usage problem.

  In addition, in many cases, the adhesive itself has high hygroscopicity in many cases, and when the transfer sheet on which the wiring circuit is formed is exposed to a high-humidity atmosphere, the adhesive layer absorbs and expands, causing the transfer sheet to deform into an irregular shape. In particular, when the wiring pattern becomes fine wiring of 50 μm or less, the wiring is peeled off from the sheet, and furthermore, when immersed in an etching solution or the like when a wiring circuit is formed due to insufficient chemical resistance, the adhesive swells. There is a problem that the fine wiring is easily peeled off from the sheet, and the adhesive strength between the wiring circuit made of metal foil and the sheet becomes uneven. As a result, when a wiring circuit is transferred to an insulating substrate using such a transfer sheet, a problem occurs in which a dimensional error or transfer failure (dropout) occurs in the transferred wiring circuit.

As a means for solving these problems, a proposal is to use a resin film having a very small heat shrinkage, specifically, a resin film having a shrinkage of 0.05% or less after heating at 100 ° C. for 1 hour (for example, Patent Document 2). See). However, the low heat shrinkable resin film requires processing by a special method, for example, a heat treatment at a high temperature for a long time, or an extremely expensive special material made of a resin having high heat resistance, such as a polyimide resin or a liquid crystal film. However, there is a problem that the cost must be increased due to the necessity of using a special film.
JP-A-10-178255 (see pages 1 to 4) Patent No. 3085649 (see pages 1 to 4)

  The present invention has been made in order to improve various disadvantages of the prior art, and an object of the present invention is to solve the above-mentioned problems of aging of the pressure-sensitive adhesive, poor transfer, dimensional errors, and non-uniform adhesive strength. In addition, an object of the present invention is to provide a transfer sheet for forming a wiring board, which is excellent in chemical resistance and can obtain a wiring board stably at low cost, which is particularly applicable to a fine wiring pattern of 50 μm or less.

  That is, the transfer sheet for forming a wiring board of the present invention is a transfer sheet for forming a wiring board, wherein a cured silicone resin layer and a metal foil are laminated in this order on a support. A transfer sheet for forming a wiring board, wherein a shrinkage ratio X after heating at 100 ° C. for one hour in at least one of the directions is 0.05% <X <0.5%.

  According to the present invention, particularly in the case of manufacturing a substrate having a fine wiring circuit of 50 μm or less, which is required in the future, a flip which requires excellent dimensional accuracy without transfer failure and disconnection of a circuit pattern, and particularly requires high accuracy of flattening. It is possible to obtain a transfer sheet for a wiring board having a performance applicable to a package or a batch hardening lamination method of a high-density multilayer wiring board by an easy process and at low cost.

  Hereinafter, the transfer sheet for forming a wiring board of the present invention will be described more specifically. The transfer sheet for forming a wiring board of the present invention has a cured silicone resin layer and a metal foil on a support, and preferably has a configuration in which they are laminated in this order, and is directly transferred to an insulating substrate after circuit pattern formation. The support can be peeled off before use. Therefore, a complicated process such as an ultraviolet irradiation step or a heating step for reacting and curing the adhesive layer after the transfer of the circuit pattern as in the conventional method becomes unnecessary.

  The support used in the present invention satisfies that the shrinkage X after heating at 100 ° C. for one hour in at least one of the MD direction and the TD direction is in the range of 0.05% <X <0.5%. What is necessary is just to do and it does not specifically limit. Preferably, 0.05% <X <0.4%, and more preferably, 0.05% <X <0.35%. It is further preferable that the shrinkage ratios in both the MD direction and the TD direction satisfy the above ranges. Within this range, the transferability of the circuit pattern formed on the silicone resin layer is significantly improved due to shrinkage of the support. If the value is below the lower limit of the above numerical range, the material of the support is limited and the selection range is narrowed, which is not only uneconomical, but also reduces the transferability of a circuit important as a transfer sheet for forming a wiring board. On the other hand, when the value exceeds the upper limit, the dimensional error of the circuit pattern increases, which is not preferable.

  Here, the MD direction and the TD direction mean a Machine Direction (machine direction) and a Transverse Direction (lateral direction), respectively.

The shrinkage of the support in the present invention after heating at 100 ° C. for 1 hour can be measured by the following method.
1. A sample of 190 × 200 mm (MD × TD) as shown in FIG. 1 is prepared.
2. The prepared sample is left at room temperature and humidity of 25 ° C. × 50% RH for 4 hours or more.
3. Measure the length of the four sides of the sample before heat treatment in a room temperature- and humidity-controlled at 25 ° C. × 50% RH.

The length can be measured by, for example, a CNC image measurement system, NEXIV VM-250 (manufactured by Nikon Instec), a single column, XY stage type, transmission type linear encoder. In this measurement, if there is a curl or the like of the film, the length cannot be accurately measured, so that a glass plate is placed on the film to suppress the floating of the film.
4. The film is placed on a coarse mesh, placed in an oven at 100 ° C., and heated for 1 hour.
5. The sample is taken out of the oven and cooled to 25 ° C., and the length of the four sides of the sample after the heat treatment is measured in a room where the temperature is adjusted to 25 ° C. × 50% RH and the humidity is adjusted.
6. From the dimensions before and after the heat treatment, the heat shrinkage X in the MD and TD directions is calculated by the following equation.

MD direction shrinkage (%) = 100 − {(after heat treatment (side A + side B) / before heat treatment (side A + side B)) × 100}
As the support, for example, metal foil or paper such as aluminum, copper, stainless steel, iron or the like, natural fiber, polymer fiber, cloth, polymer resin film and the like are used according to the purpose. From the viewpoint of handling, a support made of a resin film is preferable. Examples of the resin film include known films such as a polyester resin film such as polyethylene terephthalate and polyethylene naphthalate, and a plastic film or sheet such as polypropylene, polyphenylene sulfide, polyvinyl chloride, and PEN (polyether nitrile).

  The thickness of the support is not particularly limited as long as it can be directly transferred to an insulating substrate after forming a circuit pattern and the support can be peeled off, but when a resin film is used as the support, the thickness is 1 μm or more. It is preferably 400 μm or less. The thickness is more preferably 3 μm or more, and further preferably 5 μm or more. The resin film is more preferably 200 μm or less, and still more preferably 100 μm or less in thickness. Since the transferability of the circuit pattern tends to decrease as the thickness of the support increases, it is preferable to use a support as thin as possible.

  In the transfer sheet for forming a wiring board of the present invention, since the adhesive force between the cured silicone resin layer and a support such as a resin film is important, preferably before applying the silicone resin layer to the resin film, the resin film and It is preferable that a surface treatment for obtaining sufficient adhesiveness with the silicone resin layer is performed. Examples of such surface treatment include low-temperature plasma treatment and provision of a primer layer on the support surface.

  The low-temperature plasma treatment is a treatment performed by exposing a material to be processed to a discharge which is started and applied by applying a high DC or AC voltage between electrodes under atmospheric pressure or vacuum. For example, known corona treatment and glow discharge treatment are mentioned, and there is no particular limitation. The plasma processing conditions such as the type of gas, the processing pressure, the applied voltage, the power supply frequency, and the processing speed can be appropriately selected according to the purpose, such as the type of the plasma processing apparatus and the type of adhesive.

  The primer layer used in the present invention is not particularly limited as long as it improves the adhesive strength between the resin film and the silicone resin layer. As the primer layer, for example, a phenol resin type, an acrylic type, a polyamide type, a polyester type, an ultraviolet curable resin type, a urethane type or the like is preferable.

  Naturally, the surface of the resin film on which the primer layer is provided may be subjected to the low-temperature plasma treatment in advance.

  The thickness of the primer layer is preferably 0.1 to 100 μm, more preferably 0.2 to 50 μm, and still more preferably 0.5 to 10 μm. If the primer layer is too thin, defects such as pinholes tend to occur during coating, and if it is too thick, it is economically disadvantageous.

  The silicone resin constituting the silicone resin layer used in the present invention is roughly classified into the following two types (1) and (2).

(1) Silicone Resin Obtained by Condensation Reaction As a method of forming such a condensation type silicone rubber, a linear organic polysiloxane having a repeating unit represented by the following general formula [1] and having a molecular weight of thousands to hundreds of thousands is mentioned. Is generally crosslinked with a crosslinking agent.

In the formula, n is an integer of 2 or more; R ¹ and R ² are a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms; a substituted or unsubstituted alkenyl group having 2 to 50 carbon atoms; It is at least one selected from the group of substituted or unsubstituted aryl groups, and may be the same or different. Preferably, 40% or less of R ¹ and R ² is vinyl, phenyl, vinyl halide, or phenyl halide, and 60% or more of all is a methyl group.

  Such a linear organic polysiloxane can be further crosslinked by adding an organic peroxide and performing a heat treatment. Such a linear organopolysiloxane can be usually crosslinked by adding a crosslinking agent represented by the following general formula [2].

In the formula, q is an integer of 0 to 2, and R ³ is An alkyl group, an alkenyl group, an aryl group, or a combination thereof, which represents a functional group such as a halogen atom, an amino group, a hydroxyl group, an alkoxy group, an aryloxy group, a (meth) acryloxy group, or a thiol group; You may have it as a substituent. Z is a hydrogen atom, a hydroxyl group, an alkoxy group, an acyloxy group, a ketoxime group, an amide group, an aminooxy group, an amino group, a glycidyl group, a methacryl group, an allyl group, an acetoxysilane having a vinyl group, a ketoxime silane, an alkoxysilane, Examples include, but are not limited to, aminosilane and amidosilane.

  It is optional to add a compound containing a metal such as tin, zinc, lead, calcium, manganese or the like as a catalyst to such a condensation type silicone rubber.

(2) Silicone rubber obtained by addition reaction As a method of forming an addition type silicone rubber, a polysiloxane compound having two or more ethylenically unsaturated bonds in a molecule is reacted with a polyvalent hydrogen polysiloxane compound. The method is general. Examples of the polysiloxane compound having two or more ethylenically unsaturated bonds in the molecule include α, ω-divinylpolydimethylsiloxane, and a (methylsiloxane) (dimethylsiloxane) copolymer having methyl groups at both terminals. Examples of the polyvalent hydrogen polysiloxane compound include α, ω-dimethyl polymethyl hydrogen siloxane, and a (methyl polymethyl hydrogen siloxane) (dimethyl siloxane) copolymer having methyl groups at both terminals.

  To such an addition type silicone rubber, platinum alone, platinum chloride, olefin-coordinated platinum or the like is added as a catalyst.

  The thickness of the silicone resin layer is usually 0.5 to 100 μm, preferably 0.5 to 10 μm, and more preferably 1 to 5 μm. If the silicone resin layer is too thin, a problem of non-uniform adhesion with the metal foil may occur.

  The insolubilization rate of the silicone rubber layer is measured by the following method.

  A silicone rubber solution is applied on a degreased aluminum plate having a thickness of 0.24 mm and dried at 130 ° C. for 3 minutes to prepare a silicone rubber layer sample for measuring the insolubilization rate. Cut to 10 × 10 cm for insolubilization ratio measurement, and measure the initial weight (S). Using "Isopar E" (isoparaffinic hydrocarbon, manufactured by Exxon Chemical Co., Ltd.) as a measuring solvent, the silicone rubber layer sample was immersed in the solvent at an immersion temperature of 30 ° C. and an immersion time of 300 seconds. After wiping the surface of the silicone rubber layer sample using, the weight (T) is measured. The remaining silicone rubber layer is removed, the weight (U) of the aluminum plate is measured, and the insolubilization rate (Y) is calculated by the following general formula (a).

Y = (TU) / (SU) × 100 (a)
The insolubilization rate is preferably at least 50%, more preferably at least 70%. If the insolubilization rate is 50% or less, the silicone resin layer will fall off the substrate when etching the metal foil, causing problems such as the inability to obtain a pattern.

The metal foil used in the present invention may be any metal foil generally used for forming a conductive circuit. Suitable metal foils include, for example, metal foils such as copper, aluminum, gold, silver, and stainless steel. Among these, a particularly preferred metal is copper or an alloy containing copper. When the metal foil is a copper foil, a known rolled foil or electrolytic foil for a wiring board is preferably used. The thickness of the metal foil is 1 μm or more and 40 μm or less. It is 20 μm or less, preferably 15 μm or less, and more preferably 13 μm or less. When the thickness exceeds 40 μm, for example, there is a problem that the copper foil holding force of the silicone resin layer becomes unstable and the copper foil falls off during etching for forming a circuit pattern. The adhesive force may be preferably selected according to the temperature, pressure, pattern shape, line width, and the like during transfer, and is not particularly limited.

  The term "adhesive force" as used herein refers to the stress when the support and the silicone resin layer are peeled from the metal foil in the direction of 180 degrees, and the measurement complies with JIS-Z-0237.

  The adhesive strength is preferably 0.2 g / 10 mm or more, more preferably 0.3 g / 10 mm or more, and further preferably 1 g / 10 mm or more and 300 g / 10 mm or less.

  If the adhesive strength is less than 0.2 g / 10 mm, the adhesive tends to peel off during handling, and if the adhesive strength is greater than 300 g / 10 mm, circuit transfer failure occurs when transferring a circuit pattern, which is not preferable.

  The transfer sheet for forming a wiring board of the present invention is manufactured, for example, as follows. First, on a support such as a resin film that has been subjected to a primer treatment or a low-temperature plasma treatment for improving adhesion as necessary, a composition solution to be constituted as a silicone resin layer is coated with a reverse coater, a calendar roll coater, a knife coater, Coating is performed using a usual coater such as a Mayer bar coater or a spin coater such as a wooler and dried. Drying is usually performed by heat treatment at a temperature of 60 to 180 ° C. for several minutes, and sufficiently cured to form a silicone resin layer.

  Next, a metal foil for forming a conductive circuit is overlaid on the silicone resin layer thus obtained, and pressed by a press, a roll laminator or the like. Conditions such as temperature and pressure can be arbitrarily selected.

  The transfer sheet for forming a wiring board manufactured as described above is used as a transfer sheet for forming a wiring board by forming a predetermined circuit pattern on the metal foil by a known resist method or the like. The photoresist can be used in either a negative type or a positive type.

  For example, an example in which a circuit is formed using a positive photoresist will be described below. A photoresist is applied to the entire surface of the metal foil, and is exposed through a predetermined mask. The light source used in this exposure step generates abundant ultraviolet rays, and may be a mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a tungsten lamp, a fluorescent lamp, or the like.

  Next, the photoresist layer in the exposed area is removed by using an automatic developing device or performing manual development. Then, the copper in the non-pattern portion was removed by etching with a ferric chloride solution, washed with water, and dried to form a wiring circuit pattern, thereby obtaining a wiring board transfer sheet. Although the photoresist remains on the metal foil to be left as a circuit in this way, as long as there is no problem with the characteristics and adhesion of the insulating substrate described later, for example, when a resist having the same composition as the constituent material of the insulating substrate is used. Need not remove the remaining resist. In the case of removing the remaining resist, the resist is stripped with a resist stripper, and then washed and dried with an appropriate rinse solution.

  The wiring board transfer sheet thus obtained may be subjected to a treatment for preventing corrosion and improving adhesion to the conductor as necessary. Further, an electronic component may be mounted on the wiring board transfer sheet, or a resistor, a capacitor, an inductor, and the like may be formed by a printing method.

Next, the wiring circuit formed as described above is transferred to an insulating substrate. As a transfer method, as shown in FIG. 2, the insulating substrate 1 is superposed on the wiring circuit 2 and transferred at a pressure of about 5 to 400 kg / cm ² , and then the support 3 is peeled off. As shown in the figure, a method of forming an insulating slurry containing a curable resin thicker than the wiring circuit on the wiring circuit 2 formed by the above-described method, and then, after curing according to the purpose, peeling off the silicone resin layer 4. Used. The pressure at the time of transfer varies depending on the type of resin of the insulating substrate, but is selected so that the entire formed wiring circuit is embedded.

  Examples of the insulating substrate include a sheet, a resin having a cured resin or a semi-cured resin on a film-like heat-resistant resin, and a sheet-like material containing a semi-cured resin in an organic or inorganic fibrous base material. .

  Examples of the heat resistant resin include BT resin (bismaleimide triazine resin), epoxy resin, polyphenylene ether resin, fluorine resin, phenol resin and the like. In addition, an inorganic (filler) or an organic filler (filler) may be added to these resins as needed. The inorganic filler (filler) is not limited, and examples thereof include generally known fillers (fillers) such as silica, alumina, barium titanate, aluminum nitride, titanium oxide, and aluminum borate. Examples of the organic filler (filler) include known fillers (fillers) such as a polyimide resin and a polyaramid resin.

  Examples of the fibrous base material include fabrics such as woven fabrics made of inorganic fibers such as glass fibers and synthetic fibers such as fluorine-based fibers.

  When the wiring circuit is transferred to the above-described insulating substrate, it is preferable that the insulating substrate has at least one through hole, and the through hole is filled with a conductive paste. Thereby, for example, a composite wiring board for high-density mounting having an IVH (inner via hole) structure in which wiring patterns on both sides or one side of an insulating substrate are electrically connected by a conductive paste can be easily obtained.

  Further, it is preferable to perform the above-described low-temperature plasma treatment, surface treatment with an organic solvent or an aqueous solvent, and sandblast treatment on the surface of the insulating substrate to which the wiring circuit has been transferred. Thereby, for example, the adhesiveness with the above-described insulating substrate, heat sink, electronic component, or the like can be improved.

  The wiring board thus obtained is extremely excellent in flatness, and is particularly suitable for manufacturing a multilayer wiring board by batch lamination and flip-chip mounting.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In addition, the evaluation method of the positional deviation defect, the presence or absence of disconnection, the transfer defect, and the measuring method of the adhesive force by the stereomicroscope are as follows. The operations such as sample preparation and evaluation were performed in a room where the temperature and humidity were adjusted to 25 ° C. and 50% RH.

(a) Poor positional deviation The wiring interval was measured, and the deviation from the design value and the uniformity were evaluated. When the wiring interval was ± 5% or more from the design value, it was determined to be defective.
(b) Presence or absence of disconnection The wiring was observed and the presence or absence of disconnection was determined. If at least one disconnection was observed, it was determined to be present (defective).
(c) Poor transfer After the transfer of the wiring board on which the circuit was formed, the presence or absence of transfer residue of the circuit was observed. If there was only one transfer residue, it was determined to be defective.
(d) Adhesive strength The metal foil surface of the transfer sheet for a wiring board (25 mm wide x 300 mm long) is fixed to a 2 mm thick stainless steel plate using a double-sided adhesive tape, and the support and the silicone resin layer are separated from the metal foil by 180 degrees. Was peeled off at a speed of 300 mm / min in the direction of, and the adhesive strength (g / cm) was measured.

Example 1
The heat shrinkage of a 50 μm thick polyester film (manufactured by Toray Industries, Inc .: “Lumirror S10”) after heating at 100 ° C. for 1 hour was measured. The results are shown in Table 1. On the surface of this polyester film, a primer layer having the following composition was applied so that the film thickness after curing became 2 μm, dried at 70 ° C. for 1 minute, and then a 3 kW ultra-high pressure mercury lamp (manufactured by Oak Manufacturing Co., Ltd.) was used. Exposure was performed for 5 minutes with an illuminance of 15 mW / cm ^{2 using} a UV meter (Oak Seisakusho's light measure type UV365) to cure.
[Primer layer composition]
The primer layer had a composition consisting of the following (1) and (2).
(1) 100 parts by weight of a copolymer of 2-hydroxyethyl methacrylate / 2-hydroxyethyl acrylate / methyl methacrylate / methyl acrylate = 20/20/30/30; (2) 900 parts by weight of tetrahydrofuran.

A condensation type silicone rubber layer having the following composition was applied to the upper layer of the primer layer so that the film thickness after drying was 2 μm, and dried and cured at 100 ° C. for 2 minutes.
(Silicone rubber layer composition)
The silicone rubber layer had a composition consisting of the following (1) to (5).
(1) 100 parts by weight of polydimethylsiloxane having hydroxyl groups at both terminals (average molecular weight: 50,000), (2) 9.9 parts by weight of methyltriacetoxysilane, (3) 0.1 part by weight of dibutyltin dioctate, (4) 190 parts by weight of hexane Parts, (5) 50 parts by weight of xylene.

A glossy surface of 9 μm thick electrolytic copper foil (Furukawa Circuit Foil Co., Ltd .: F0-WS) was overlaid and laminated on the upper layer of the silicone rubber layer to obtain a transfer sheet for a wiring board. The adhesive strength between the copper foil and the silicone adhesive layer was measured. Table 1 shows the results. Next, a photoresist is formed on the entire upper surface of the copper foil of the obtained wiring board transfer sheet by spin coating, and is dried to a thickness of 4 μm to have a wiring width of 25 μm and a wiring pitch of 50 μm. A mask having a ground electrode pattern of 5 mm square having an area of about 60% of that of the above is superimposed on the positive film under vacuum for 30 seconds, and a UV meter (Oak Seisakusho) is used at 28 ° C. using a 3 kW ultra-high pressure mercury lamp (Oak Seisakusho). Exposure was performed for 2 minutes with an illuminance of 2.4 mW / cm ^{2 using} a light measure type UV365). After the exposure, the mask was removed, and alkali development was performed using an aqueous sodium hydroxide solution to remove unnecessary resist, followed by washing and drying. Next, the copper in the non-pattern portion was removed by etching with a ferric chloride solution, washed with water, and dried, and then the resist on the wiring pattern was peeled off. Thus, a wiring board transfer sheet having a wiring circuit pattern with a wiring pitch of 50 μm was obtained. Subsequently, an insulating sheet having a thickness of 100 μm and a square of 12 cm after drying an insulating slurry having the following composition as an organic resin by a doctor blade method was prepared.
[Insulating slurry composition]
The insulating slurry had the following composition (1) to (3).
(1) BT resin (manufactured by Mitsubishi Gas Chemical Co., Ltd.) 30% by volume, (2) spherical silica (volume average particle size 2 μm) 70% by volume, (3) solvent: butyl acetate 20 parts by weight.

The obtained insulating sheet was superimposed on the wiring circuit surface, and the conductor circuit was transferred to the insulating sheet by a vacuum heating press under the conditions of a pressure of 50 kg / cm ² , a pressing time of 30 minutes, and a temperature of 100 ° C., and completely embedded therein.

  Next, the cured polyester film with the silicone resin layer was peeled off, and the insulating sheet was cured by heating at 190 ° C. for 6 hours. Ten wiring boards were prepared, and a stereoscopic microscope was used to observe misalignment, disconnection, and transfer failure. Table 1 shows the results.

Example 2
The polyester film of Example 1 (manufactured by Toray Industries, Inc., “Lumirror S10”) was heat-treated at a temperature of 70 ° C. for 30 minutes. Further, an aluminum electrode was used as a corona discharge treatment on this support, and the electrode density was 250 (W). Surface treatment was performed under the conditions of (min / m ² ). The heat shrinkage after heating at 100 ° C. for 1 hour after the heat treatment and corona discharge treatment was measured. The results are shown in Table 1. This film was used as a support and evaluated in the same manner as in Example 1 except that the primer layer of Example 1 was not formed.

Example 3
The polyester film of Example 1 (manufactured by Toray Industries, Inc .: “Lumirror S10”) was heat-treated at a temperature of 90 ° C. for 30 minutes. The heat shrinkage after heating at 100 ° C. for 1 hour after the heat treatment was measured. The results are shown in Table 1. Evaluation was performed in the same manner as in Example 1 except that this film was used as a support.

Example 4
The polyester film of Example 1 (manufactured by Toray Industries, Inc .: “Lumirror S10”) was heat-treated at a temperature of 120 ° C. for 30 minutes. The heat shrinkage after heating at 100 ° C. for 1 hour after the heat treatment was measured. The results are shown in Table 1. Evaluation was performed in the same manner as in Example 1 except that this film was used as a support.

Example 5
A 3 μm-thick polyester film (manufactured by Toray Industries, Inc .: “Lumilar C21”) was heat-treated at 90 ° C. for 30 minutes. The heat shrinkage after heating at 100 ° C. for 1 hour after the heat treatment was measured. The results are shown in Table 1. Evaluation was performed in the same manner as in Example 1 except that this film was used as a support.

Example 6
The heat shrinkage of a 25 μm thick polyimide film (manufactured by Toray DuPont, “Kapton 100H”) after heating at 100 ° C. for 1 hour was measured. The results are shown in Table 1.
After the same primer layer as in Example 1 was formed on the surface of this polyimide film, a condensation type silicone rubber layer was applied so that the film thickness after drying was 2 μm, and dried and cured at 100 ° C. for 2 minutes.

A glossy surface of a 12 μm-thick electrolytic copper foil (Furukawa Circuit Foil Co., Ltd .: F0-WS) was overlaid and laminated on the silicone rubber layer to obtain a transfer sheet for a wiring board wound on a roll. The adhesive strength between the copper foil and the silicone adhesive layer was measured. Table 1 shows the results. Next, a dry film photoresist (Nichigo Morton Co., Ltd .: ALPHO NIT215) is laminated on the entire upper surface of the copper foil of the obtained wiring board transfer sheet, and a wiring circuit mask having a line width of 25 μm and a wiring pitch of 50 μm. And a positive film was vacuum-adhered for 30 seconds, and a UV meter (Light Measure Type UV365, manufactured by Oak Manufacturing Co., Ltd.) was used at a temperature of 28 ° C. using a 3 kW ultra-high pressure mercury lamp (manufactured by Oak Manufacturing Co., Ltd.) at 2.4 mW / Exposure was performed for 35 seconds at an illuminance of cm ² . After the exposure, the mask was removed, and alkali spray development was performed with a 1% aqueous solution of Na ₂ CO ₃ to remove unnecessary resist, followed by washing and drying. Next, the copper in the non-pattern portion was removed by etching with a ferric chloride solution, washed with water, and dried, and then the resist on the wiring pattern was peeled off. Thus, a wiring circuit pattern having a wiring pitch of 50 μm was formed, and a wiring substrate transfer sheet was obtained. Evaluation was performed in the same manner as in Example 1 except that the substrate transfer sheet on which this wiring pattern was formed was used.

Example 7
The polyimide film of Example 6 (manufactured by Toray DuPont: "Kapton 100H" registered trademark) was heat-treated at a temperature of 90 ° C for 30 minutes. The heat shrinkage after heating at 100 ° C. for 1 hour after the heat treatment was measured. The results are shown in Table 1. Evaluation was performed in the same manner as in Example 6 except that this film was used as a support.

Example 8
The heat shrinkage of a 25 μm-thick polyimide film (manufactured by Toray DuPont, “Kapton 100EN”) after heating at 100 ° C. for 1 hour was measured. The results are shown in Table 1.
Evaluation was performed in the same manner as in Example 6 except that this film was used as a support.

Comparative Example 1
The heat shrinkage of a 50 μm-thick polyester film (manufactured by Toray Industries, Inc .: “Lumirror X10S”) after heating at 100 ° C. for 1 hour was measured. The results are shown in Table 1. The polyester film was prepared and evaluated in the same manner as in Example 1 except that an adhesive made of an acrylic resin was used and a copper foil was adhered on the polyester film. Table 1 shows the results. The adhesive strength with the copper foil was 150 g / cm.

Comparative Example 2
A 50 μm thick polyester film (manufactured by Toray Industries, Inc .: “Lumirror X10S”) was heat-treated at 70 ° C. for 30 minutes. The heat shrinkage after heating at 100 ° C. for 1 hour after the heat treatment was measured. The results are shown in Table 1.

  The polyester film was prepared and evaluated in the same manner as in Example 1 except that an adhesive made of an acrylic resin was used and a copper foil was adhered on the polyester film. Table 1 shows the results. The adhesive strength with the copper foil was 150 g / cm.

Comparative Example 3
The heat shrinkage of a 50 μm-thick polyester film (manufactured by Toray Industries, Inc .: “Lumirror X10S”) after heating at 100 ° C. for 1 hour was measured. The results are shown in Table 1. Evaluation was performed in the same manner as in Example 1 except that this film was used as a support.

Comparative Example 4
The heat shrinkage of a 50 μm thick liquid crystal polyester film (manufactured by Kuraray Co., Ltd .: “VECTRA OC”) after heating at 100 ° C. for 1 hour was measured. The results are shown in Table 1. Evaluation was performed in the same manner as in Example 1 except that this film was used as a support.

  As described above, in Examples 1 to 8 of the present invention, one out of ten samples in Example 1 and Example 8 was defective in transfer or defective in transfer, but within the allowable range. In other examples 2 to 7, good wiring boards without any misalignment, disconnection, or transfer failure were obtained. On the other hand, in Comparative Examples 1 and 2, the etching liquid eroded the interface between the wiring pattern and the acrylic adhesive when forming the wiring circuit pattern, and as a result, many partial disconnections were observed. Further, since the support has a large heat shrinkage, misregistration occurs and the wiring board is not practical. In Comparative Example 3, since the support had a large heat shrinkage, a misalignment defect occurred and the wiring board was not practical. In Comparative Example 4, since the support had a very small heat shrinkage, transfer failure occurred, and the wiring substrate was not practical.

FIG. 4 is a diagram showing the shape of a support when measuring a shrinkage X. FIG. 3 is a cross-sectional view illustrating a transfer method for transferring a wiring circuit formed on a transfer sheet for a wiring board of the present invention to an insulating substrate. FIG. 4 is a cross-sectional view illustrating another transfer method for transferring a wiring circuit formed on a transfer sheet for a wiring board of the present invention to an insulating substrate.

Explanation of reference numerals

1: Insulating substrate 2: Wiring circuit 3: Support (resin film)
4: Silicone resin layer

Claims (5)

A transfer sheet for forming a wiring board having a cured silicone resin layer and a metal foil on a support, wherein the shrinkage X after heating at 100 ° C. for 1 hour in at least one of the MD direction and the TD direction of the support. A transfer sheet for forming a wiring board, wherein 0.05% <X <0.5%. 2. The transfer sheet according to claim 1, wherein the support is made of a resin film having a thickness of 1 μm or more and 400 μm or less. 2. The transfer sheet according to claim 1, wherein the thickness of the metal foil is 1 μm or more and 40 μm or less. 2. The transfer sheet for forming a wiring board according to claim 1, wherein the support is a resin film, and the surface of the resin film is subjected to low-temperature plasma treatment. The transfer sheet for forming a wiring board according to claim 1, wherein a primer layer is provided on the surface of the support.

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