JP2004265913A - Circuit board member and method of manufacturing circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board member using a flexible film equipped with a circuit pattern excellent in dimensional accuracy and capable of being separated from a reinforcing plate with a low stress without producing creases or a distortion, and to provide a method of manufacturing a circuit board. <P>SOLUTION: The reinforcing plate, a separable organic material layer, the flexible film where the circuit pattern has been formed, and a separation auxiliary layer, are stacked up in this sequence into the circuit board member. In the method of separating the flexible film with the circuit pattern stuck on the reinforcing plate through the intermediary of the separable organic layer, the separation auxiliary layer is formed on the circuit pattern first, and then the flexible film is separated from the reinforcing plate. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a circuit board using a flexible film having a highly accurate circuit pattern and excellent productivity.
[0002]
[Prior art]
2. Description of the Related Art As electronic products have become lighter and smaller, there has been a demand for higher precision patterning of printed circuit boards. The demand for a flexible film substrate is expanding because it can be bent to provide three-dimensional wiring and is suitable for miniaturization of electronic products.
[0003]
TAB (Tape Automated Bonding) technology used for IC connection to a liquid crystal display panel can obtain the finest pattern as a resin substrate by processing a relatively narrow and long polyimide film substrate. With regard to the progress of development, the limit is approaching.
[0004]
The miniaturization includes an index represented by a line width or a space width between lines, and an index represented by a position of a pattern on a substrate. There are measures to further reduce the line width and space width, but the latter index, the positional accuracy, is determined by the alignment between the electrode pads and the circuit board pattern when connecting the circuit board and electronic components such as ICs. In connection with this, as the number of pins of an IC increases, it is becoming more difficult to cope with required accuracy.
[0005]
In view of the above positional accuracy, it is becoming difficult to improve the processing of a flexible film substrate in particular. That is, the circuit board processing process includes a heat treatment process such as drying and curing, and a wet process such as etching and development, and the flexible film repeatedly expands and contracts. This is because the hysteresis at this time causes a displacement of the circuit pattern on the substrate. In addition, when there are a plurality of processes that require alignment, if there is expansion or contraction between these processes, misalignment occurs between patterns to be formed.
[0006]
The deformation due to the expansion and contraction of the flexible film has a greater effect in the case of FPC (Flexible Printing Circuit) which proceeds with a relatively large area substrate size. The displacement is also caused by an external force such as pulling or twisting, and special care is required when a thin substrate is used to increase flexibility.
[0007]
In recent years, it has been proposed to form a very fine circuit pattern by attaching a flexible film to a reinforcing plate and maintaining dimensional accuracy. Since the circuit pattern of the flexible film substrate is used after being peeled off from the reinforcing plate, it is desired that the dimensional change of the circuit pattern when peeled off from the reinforcing plate be suppressed to the order of microns. Therefore, there is a demand for peeling the flexible film without applying stress as much as possible.
[0008]
However, in the conventional peeling of the flexible film, the rigid substrate is generally a product, and the flexible film is generally a protective film. Therefore, the quality of the flexible film after peeling is not particularly noted, and the main focus is on the reliable peeling of the flexible film. For this reason, there has been no means for peeling while maintaining the flatness of the flexible film (peeling without generating a strain of about several hundred μm).
[0009]
As a method of peeling a flexible film from a rigid substrate, a method of fixing a rigid substrate and peeling the flexible film has been proposed. Specifically, a method of gripping and peeling off the end of the flexible film (for example, see Patent Document 1), or pressing a pressing plate against the surface of the flexible film, and then removing the end of the flexible film There has been proposed a method of peeling a flexible film by turning up with a claw-shaped member (for example, see Patent Document 2). In these peeling methods, the flexible film after peeling is broken or distorted, and the dimensions are largely changed.
[0010]
[Patent Document 1]
JP-A-5-319675 (page 2)
[0011]
[Patent Document 2]
JP-A-7-315682 (page 3)
[0012]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art as described above, to peel off a flexible film on which a circuit pattern is formed without breaking or distorting, and to further suppress a dimensional change of the circuit pattern at the time of peeling. It is to provide a circuit board.
[0013]
[Means for Solving the Problems]
In order to achieve the object of the present invention, the present invention comprises the following members and a manufacturing method.
(1) A circuit board member comprising a reinforcing plate, a peelable organic material layer, a flexible film having a circuit pattern on one or both sides, and a peeling auxiliary layer laminated in this order.
(2) The circuit board member according to claim 1, wherein the electronic component is bonded on the circuit pattern of the flexible film.
(3) Forming a peeling auxiliary layer on a flexible film having a circuit pattern on one or both sides attached to a reinforcing plate via a peelable organic material layer, and then reinforcing the flexible film A method for manufacturing a circuit board, comprising peeling off a board.
(4) The method for manufacturing a circuit board according to the above (3), wherein the separation assisting layer is a solder resist.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention relates to a circuit board member in which a release auxiliary layer is further provided on a flexible film having a reinforcing plate, an organic layer, and a circuit pattern, and a method of manufacturing a circuit board using the same.
[0015]
The function of the release assisting layer in the present invention is presumed as follows. That is, a metal layer (for example, a copper layer) forming a circuit pattern is more easily plastically deformed than a flexible film. When peeling the flexible film from the reinforcing plate, when the metal layer undergoes plastic deformation due to deformation such as bending or elongation, shrinkage above the yield point, bending or distortion of the flexible film with a circuit pattern after peeling, Furthermore, it causes a dimensional change. When the release auxiliary layer is formed on the flexible film with a circuit pattern, the rigidity is increased (strengthened) integrally with the flexible film with a circuit pattern. Further, by providing the peeling auxiliary layer on the circuit pattern, the center of bending in the thickness direction at the time of peeling can be made closer to the circuit pattern, and the deformation applied to the metal layer can be reduced.
[0016]
The peeling auxiliary layer in the present invention is formed on a flexible film with a circuit pattern, and when peeling off the flexible film from the reinforcing plate, it is necessary to prevent the flexible film from being bent or distorted. The material, flatness, thickness, and the like are not particularly limited as long as they have strength and can be removed after the flexible film is peeled off. However, if it is too hard, such as metal or glass, the peeling force will be too strong and the productivity will be poor, and there is a risk of plastic deformation or breakage. Therefore, an organic elastic material such as plastic or rubber is preferable.
[0017]
Specific examples include vinyl resins such as polyvinyl alcohol, vinyl acetate, polyethylene, and polystyrene; and epoxy resins, acrylic resins, and urethane resins. Above all, vinyl resins are inexpensive and easy to form films, have the advantage that they can be easily removed with water after the flexible film is peeled off the reinforcing plate, and that the removed solution can be reused. In addition, when an epoxy resin having heat resistance or chemical resistance is used, it can be used instead of a solder resist, and the step of removing the separation assisting layer can be omitted, which is preferable.
[0018]
The method for forming the release assisting layer is to apply a solution-like resin on a flexible film with a circuit pattern attached to a reinforcing plate, and then to dry the resin or apply a resin precursor to the flexible film. After that, there is a method of firing. The specific application method is described below, but it should be noted that the temperature at the time of drying or baking must be such that the flexible film is not deteriorated.
[0019]
Examples of the method for applying the release auxiliary layer include a spin coater, a roll coater, a die coater, a screen printing, a dip coater, and a spray coater. The application of the release auxiliary layer may be performed before or after the electronic component is mounted on the flexible film with a circuit pattern. However, after the electronic component is mounted, the surface to be applied is not flat, so that the spin coater or the contact may be used. Application is difficult with a roll coater of the formula or screen printing, and a die coater, a dip coater, and a spray coater are preferable.
[0020]
As another method of forming the release assisting layer, a sheet-like resin is bonded to the surface of a flexible film with a circuit pattern via an acrylic or urethane-based peelable pressure-sensitive adhesive layer or the like. There is a method of joining a certain sheet-like resin. In this case, in addition to the above resins, various plastics, rubbers, and the like can be used.
[0021]
As still another preferred embodiment, an opening or a pattern may be provided in the separation assisting layer in accordance with the circuit pattern, or two or more kinds of layers may be partially provided. For example, a first peeling auxiliary layer is provided on a flexible film with a circuit pattern, an opening is formed in an electronic component mounting portion of the first peeling auxiliary layer, and after the electronic component is mounted, a second peeling is performed from above. The provision of an auxiliary layer is also permitted.
[0022]
The removal of the peeling auxiliary layer after the flexible film is peeled from the reinforcing plate can be performed by a method of dissolving in a water or an organic solvent, a method of peeling the peeling auxiliary layer from the flexible film, or the like. However, it is preferable that the flexible film is fixed to a flat vacuum suction table or the like so that the flexible film is not broken or distorted when the auxiliary release layer is separated from the flexible film.
[0023]
The flexible film used in the present invention is a plastic film, and needs to have heat resistance enough to withstand a heat process in a circuit pattern manufacturing process and an electronic component mounting, for example, polycarbonate, polyether. Films such as sulfide, polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polyimide, polyamide, and liquid crystal polymer can be used. Among them, a polyimide film is preferably used because it has excellent heat resistance and chemical resistance. In addition, liquid crystal polymers are preferably used because of their excellent electrical characteristics such as low dielectric loss. It is also possible to employ a flexible glass fiber reinforced resin plate.
[0024]
The thickness of the flexible film is preferably thin for reducing the weight and size of the electronic device or for forming a fine via hole, while maintaining the flatness and securing mechanical strength. From the viewpoint that a thicker film is preferable, a range of 4 μm to 125 μm is preferable.
[0025]
Before the flexible film is attached to the reinforcing plate, a metal layer may be formed on one side or both sides. The metal layer can be formed by attaching a metal foil such as a copper foil with an adhesive layer, or by sputtering, plating, or a combination thereof. A flexible film with a metal layer can be produced by applying, drying, and curing a raw material resin for a flexible film or a precursor thereof on a metal foil such as copper. The metal layer only needs to have high conductivity, and for example, gold, silver, aluminum, or the like can be used.
[0026]
As the material used for the reinforcing plate in the present invention, for example, soda lime glass, borosilicate glass, inorganic glass such as quartz glass, alumina, silicon nitride, ceramics such as zirconia, stainless steel, invar alloy, metal such as titanium Or glass fiber reinforced resin. Both are preferable in that the coefficient of linear expansion and the coefficient of hygroscopic expansion are small, but they are excellent in heat resistance and chemical resistance in the circuit pattern manufacturing process, a large-area substrate with high surface smoothness is easily available at low cost, Inorganic glasses are preferred because they are less likely to be plastically deformed, or less likely to generate particles during contact during transportation or the like. Among them, borosilicate glass represented by aluminoborosilicate glass is particularly preferable because of its high elastic modulus and small linear expansion coefficient.
[0027]
When a glass substrate having a small thickness is used for the reinforcing plate, the warpage and torsion increase due to the expansion / contraction force of the flexible film, and the glass substrate may be broken when vacuum-adsorbed on a flat stage. In addition, the flexible film is deformed by vacuum suction / detachment, which tends to make it difficult to secure positional accuracy. On the other hand, in the case of a glass substrate having a large thickness, flatness is reduced due to thickness unevenness and exposure accuracy is reduced. In addition, the load on handling by a robot or the like becomes large, and quick operation cannot be performed, which causes a decrease in productivity and increases transport costs. From these points, the thickness of the glass substrate is preferably in the range of 0.3 mm to 1.1 mm.
[0028]
If a thin metal substrate is used for the reinforcing plate, warping and twisting will increase due to the expansion and contraction force of the flexible film, and vacuum suction on a flat stage will not be possible, or warping and twisting of the metal substrate will occur. The deformation of the flexible film makes it impossible to secure a predetermined positional accuracy. Also, if there is a break, it becomes defective at that time. On the other hand, in the case of a metal substrate having a large thickness, flatness is reduced due to thickness unevenness, and exposure accuracy is reduced. In addition, the load on handling by a robot or the like becomes large, and quick operation cannot be performed, thereby lowering productivity and increasing transportation cost. Therefore, the thickness of the metal substrate is preferably in the range of 0.1 mm to 0.7 mm.
[0029]
The peelable organic material layer used in the present invention is made of an adhesive or a pressure-sensitive adhesive, as long as the flexible film can be peeled off after the flexible film is attached to the reinforcing plate via the organic material layer and processed. There is no particular limitation. Examples of such an adhesive or pressure-sensitive adhesive include a pressure-sensitive adhesive called an acrylic or urethane-based re-peeling agent. It has a sufficient adhesive strength during the processing of the flexible film, can be easily peeled off at the time of peeling, and does not cause distortion of the flexible film substrate, so that an adhesive strength in an area called weak adhesive to medium adhesive is preferable. used. A tacky silicone resin or epoxy resin can also be used.
[0030]
The peeling force in the present invention is measured by a 180 ° peel strength when a 1-cm-wide flexible film bonded to a reinforcing plate via a peelable organic material layer is peeled off. The peeling speed when measuring the peeling force is 300 mm / min. In the present invention, the peeling force is preferably in the range of 0.1 g / cm to 100 g / cm.
[0031]
In addition to the above-mentioned releasable organic material layers, there are also those whose adhesive strength and adhesive strength are reduced in the low temperature region, those whose adhesive strength and adhesive strength are reduced by UV irradiation, and those whose adhesive strength and adhesive strength are reduced by heat treatment. It is preferably used. Among these, those that are irradiated by ultraviolet light have large changes in adhesive strength and adhesive strength.Before joining electronic components at high temperature and high pressure, they are cross-linked by irradiation with ultraviolet light to prevent softening due to temperature and deformation due to pressure. It is preferable because it can be suppressed. As an example of the adhesive force and the adhesive force that are reduced by the irradiation of ultraviolet rays, a two-component cross-linkable acrylic pressure-sensitive adhesive can be used. Further, as an example of an adhesive having a reduced adhesive strength and adhesive strength in a low temperature region, an acrylic adhesive which reversibly changes between a crystalline state and an amorphous state can be cited.
[0032]
As a method for applying a peelable organic material layer and a method for applying a photoresist for forming a circuit pattern, for example, a wet coating method is used. Various types of wet coating devices such as spin coaters, reverse coaters, bar coaters, blade coaters, roll coaters, die coaters, screen printing, dip coaters, spray coaters, etc. can be used, but can be peeled off on a single-sheet reinforcing plate. It is preferable to use a die coater when directly applying an organic layer or applying a photoresist for forming a circuit board directly on a single flexible film substrate.
[0033]
The die coater combines a metering pump that can operate intermittently, a mechanism that moves the substrate and the coating head relatively, and a system that comprehensively controls the metering pump, the substrate, and the coating head, so that the coating start part and the coating end The coating can be applied to a single-wafer substrate while suppressing the thickness unevenness of the portion from several mm to several tens mm. Examples of the metering pump capable of intermittent operation include a gear pump and a piston pump. Since a peelable organic material layer generally has a higher viscosity than a photoresist, it is particularly preferable to use a die coater.
[0034]
The following points should be noted regarding wet coating on a single sheet. Although a spin coater is generally used, the use efficiency of the coating liquid is inefficient at 10% or less because the thickness is controlled by the balance between the centrifugal force due to the high-speed rotation of the substrate and the attraction force to the substrate. Further, since a centrifugal force is not applied to the center of rotation, it may not be possible to uniformly apply a coating liquid having a thixotropic property or a coating liquid having a high viscosity, depending on the type of the coating liquid used. In order to obtain a stable coating thickness, a reverse coater, a bar coater, and a blade coater usually require a coating length of several tens of cm to several meters or more after the start of coating liquid discharge, and are applied to a single-wafer substrate. Care must be taken when applying to coatings.
[0035]
The peelable organic layer may be directly applied to the reinforcing plate, or may be applied to another substrate such as a long film and then transferred to the reinforcing plate. When transfer is used, there is an advantage that only a portion where the coating film thickness is uniform can be adopted, but there are disadvantages that the number of steps is increased or another substrate for transfer is required.
[0036]
Alternatively, a peelable organic layer may be applied to the flexible film side and then bonded to the reinforcing plate. In this case, a step for increasing the adhesion between the organic material layer and the surface of the reinforcing plate so that the organic material layer remains on the reinforcing plate side when the flexible film is peeled off, or the organic material remaining on the flexible film side after peeling. A step of removing a layer may be added and productivity may be reduced.
[0037]
The thickness of the releasable organic layer used in the present invention is not more than 0.1 μm because, when the thickness is too small, the flatness is deteriorated, and the strength of the peeling force due to the unevenness of the film thickness occurs because the peeling force is significantly reduced. Is more preferable, and more preferably 0.3 μm or more. On the other hand, when the thickness of the peelable organic material layer is too large, the adhesion of the organic material layer to the flexible film is improved, and the adhesive strength becomes too strong. Therefore, the thickness is preferably 20 μm or less, and more preferably 10 μm or less. More preferred. When joining an electronic component to a circuit pattern on a flexible film fixed via a peelable organic material layer on a reinforcing plate, the thickness of the peelable organic material layer is controlled to suppress a change in the thickness direction of the circuit pattern. Is preferably 5 μm or less. When the peelable organic material layer is thick, when the electronic component is heated and pressed, the amount of deformation of the peelable organic material layer is large, and the circuit pattern of the bonding portion sinks, which may cause a problem in the reliability of the wiring circuit. When the sink is large, the circuit pattern may come into contact with the edge of the electronic component to cause a short circuit. The sink is preferably 6 μm or less, more preferably 3 μm or less, to ensure the reliability of the wiring circuit.
[0038]
In the present invention, an electronic component may be mounted on a flexible film with a circuit pattern formed on a reinforcing plate. Here, the mounting method of the electronic component is not particularly limited, and a known method can be used.
[0039]
Before the flexible film used in the present invention is attached to the reinforcing plate, a circuit pattern and an alignment mark may be formed on one surface which is an attachment surface. When the reinforcing plate is transparent, the alignment mark may be read through the reinforcing plate or may be read through the flexible film, but a metal layer is formed on the side opposite to the bonding surface of the flexible film. In this case, reading from the reinforcing plate is preferable because reading can be performed regardless of the pattern of the metal layer. This alignment mark can also be used for alignment when bonding the flexible film to the reinforcing plate. The shape of the alignment mark is not particularly limited, and a shape generally used in an exposure machine or the like can be suitably adopted.
[0040]
The circuit pattern formed on the surface opposite to the bonding surface after bonding to the reinforcing plate can form a particularly high-precision pattern with a pitch of 60 μm or less, but is formed on the bonding surface with the reinforcing plate. The pattern mainly serves as the input / output terminal to the printed wiring board and the wiring around it, as well as the power supply and ground potential wiring, and is formed on the surface opposite to the surface attached to the reinforcing plate. In some cases, high definition is not required. According to the present invention, it is also easy to provide a double-sided wiring in which a particularly fine pattern is formed on one side. The advantages of the double-sided wiring are that the wiring can be crossed through through holes, increasing the degree of freedom in wiring design, and the LSI that operates at high speed by propagating the ground potential to the vicinity of the required place with thick wiring. Similarly, the power supply potential can be propagated to the vicinity of the required location by thick wiring to prevent the potential from dropping even at high-speed switching, stabilize the operation of the LSI, and reduce external noise as an electromagnetic wave shield. It becomes very important when the speed of the LSI is increased and the number of pins is increased by increasing the number of functions.
[0041]
Next, a preferred example of the method for manufacturing a circuit board of the present invention will be described below, but the present invention is not limited thereto.
[0042]
A releasable organic layer (a weakly sticking re-peeling agent) is applied to an aluminoborosilicate glass having a thickness of 1.1 mm. The coating method is the method described above, and it is preferable to use a die coater in order to uniformly apply the liquid to a single-wafer substrate that is intermittently fed. After applying the re-release agent, the re-peeling agent is dried by heat drying, vacuum drying, or the like to obtain a releasable organic layer having a thickness of 2 µm. An air-blocking film made of a release film (for example, a silicone resin layer is provided on a polyester film) is adhered to the peelable organic material layer and left at room temperature for one week. This period is called aging, and the crosslinking of the peelable organic material layer progresses, and the adhesive strength gradually decreases. The leaving period and the storage temperature are selected so as to obtain a desired adhesive strength. Instead of laminating the air blocking film, it can be stored in a nitrogen atmosphere or in a vacuum. It is also possible to apply a weakly peelable organic substance to a long film substrate, transfer it to a reinforcing plate after drying, and then.
[0043]
Next, a polyimide film having a thickness of 25 μm is prepared. The film for air blocking on the glass substrate is peeled off, and the polyimide film is attached to the glass substrate. As described above, a metal layer (which may be a circuit pattern) may be previously formed on one or both sides of the polyimide film. When a metal layer is provided on the side to which the polyimide film is attached, it can be used as a ground layer for shielding electromagnetic waves. The polyimide film may be pasted in a cut sheet of a predetermined size, or may be pasted and cut while being wound from a long roll. A roll laminator or a vacuum laminator can be used for such an attaching operation.
[0044]
Next, electronic components such as an IC chip, a resistor and a capacitor are mounted on the circuit pattern. The electronic component mounting device that can be used in the present invention is not particularly limited as long as it has an optical position detecting function and a positioning function of a movable stage and the like and can ensure mounting accuracy. The present invention is particularly effective for securing the mounting accuracy of a large-scale LSI having a small connection pitch and a large number of pins. The package form of the LSI is not particularly limited, and can be applied to any of a bare chip, a lead frame type, and a ball grid array type, but is preferably applied to a bare chip or a ball grid array type having a large number of pins.
[0045]
The method for connecting the electronic component and the circuit board that can be used in the present invention is not particularly limited, but it is preferable to use a connection method in which a large number of connection portions are joined together at a time in terms of securing positional accuracy and productivity. As a connection method for joining a large number of connection portions at once, for example, a metal layer such as tin, gold, or solder formed on a connection portion of a circuit board and a metal layer such as gold or solder formed on a connection portion of an electronic component. The method of bonding the layers with heat and pressure to join the metal, the circuit board while crimping the metal layer such as tin, gold and solder at the connection part of the circuit board with the metal layer such as gold and solder formed at the connection part of the electronic component After curing the anisotropic conductive adhesive or non-conductive adhesive placed between the electronic component and the mechanical component, or after temporarily fixing the electronic component on the solder paste with the pattern printed on the connection part And a method of connecting by batch reflow.
[0046]
Next, a peeling auxiliary layer is formed on the flexible film on which the circuit pattern and the electronic component are mounted, and the peeling auxiliary layer and the flexible film are peeled together from the reinforcing plate. The peeling method includes a method in which the end of the flexible film is gripped and pulled, and a method in which the flexible film is peeled along a cylindrical member, but in order not to apply a stress that deforms the shape of the flexible film. It is also preferable to adopt the latter method. Further, in a normal circuit pattern, there is a bias in the wiring direction, and in many cases, the distribution is such that the longitudinal direction of the wiring is aligned with a specific direction. In such a case, it is preferable to peel the wiring in a direction perpendicular to a direction in which many longitudinal directions of the wirings are arranged, because deformation of the film can be reduced. Further, it is preferable that the peelable organic material layer is heated at the time of peeling to soften the organic material layer and reduce the peeling force, because deformation of the film can be further suppressed.
[0047]
After peeling, the peeling auxiliary layer is removed from the flexible film to obtain a film circuit board.
[0048]
When a metal layer is not provided on the surface opposite to the bonding surface of the polyimide film, the metal layer is formed by a full additive method or a semi-additive method.
[0049]
The full additive method is a process as follows. The surface on which the metal layer is to be formed is treated with a catalyst such as palladium, nickel or chromium, and dried. The catalyst mentioned here does not work as a nucleus for plating growth as it is, but becomes a nucleus for plating growth by performing an activation treatment. The catalyst application treatment may be performed after bonding a flexible film to the reinforcing plate, or may be performed on a long flexible film before bonding. Next, a photoresist is applied by a spin coater, a blade coater, a roll coater, a bar coater, a die coater, screen printing, or the like, and dried. The photoresist is exposed and developed through a photomask having a predetermined pattern to form a resist layer in a portion where a plating film is unnecessary. Thereafter, after activating the catalyst, the polyimide film is immersed in an electroless plating solution composed of a combination of copper sulfate and formaldehyde to form a copper plating film having a thickness of 2 μm to 20 μm. obtain.
[0050]
The semi-additive method is a process as follows. Chromium, nickel, copper or an alloy thereof is sputtered on the surface on which the metal layer is to be formed to form an underlayer. The thickness of the underlayer ranges from 1 nm to 1000 nm. Laminating a copper sputtered film on the underlayer further from 50 nm to 3000 nm is effective in securing sufficient conduction for the subsequent electrolytic plating, improving the adhesive strength of the metal layer, and preventing pinhole defects. Prior to the formation of the underlayer, plasma treatment, reverse sputtering treatment, application of a primer layer, and application of an adhesive layer are appropriately permitted on the surface of the polyimide film in order to improve the adhesive strength. Above all, it is preferable to apply an adhesive layer of an epoxy resin type, an acrylic resin type, a polyamide resin type, a polyimide resin type, an NBR type or the like because the effect of improving the adhesive strength is large. These treatments and application may be performed before attaching the reinforcing plate, or may be carried out after attaching the reinforcing plate. It is preferable that a long polyimide film is continuously processed by roll-to-roll before the reinforcing plate is attached because productivity can be improved. The base layer may be formed after bonding a flexible film to the reinforcing plate, or may be formed on, for example, a long flexible film before bonding. A photoresist is applied on the underlayer formed in this manner by a spin coater, a blade coater, a roll coater, a die coater, screen printing, or the like, and dried. The photoresist is exposed and developed through a photomask having a predetermined pattern to form a resist layer in a portion where a plating film is unnecessary. Next, electrolytic plating is performed using the underlying layer as an electrode. As the electrolytic plating solution, a copper sulfate plating solution, a copper cyanide plating solution, a copper pyrophosphate plating solution, or the like is used. After forming a copper plating film having a thickness of 2 μm to 20 μm, the photoresist is peeled off, and then the underlying layer is removed by a slight etching to obtain a circuit pattern. Further, plating of gold, nickel, tin or the like is performed as necessary.
[0051]
In forming these metal layers (circuit patterns), connection holes can be provided in the polyimide film. That is, it is possible to provide a via hole for making an electrical connection with a metal layer provided on the surface to be bonded to the single-wafer substrate, or to provide a hole for placing a ball of a ball grid array. As a method of providing the connection holes, laser holes such as a carbon dioxide laser, a YAG laser, and an excimer laser, and chemical etching can be employed. When laser etching is employed, it is preferable that a metal layer be provided on the side of the polyimide film on which the reinforcing plate is attached, as an etching stopper layer. Hydrazine, an aqueous solution of potassium hydroxide, or the like can be used as the chemical etching solution for the polyimide film. In addition, a patterned photoresist or metal layer can be employed as the chemical etching mask. In the case of making an electrical connection, it is preferable that after the formation of the connection hole, the inner surface of the hole is made conductive by plating simultaneously with the formation of the metal layer pattern. The diameter of the connection hole for making electrical connection is preferably 15 μm to 200 μm. The diameter of the hole for ball installation is preferably 50 μm to 800 μm, more preferably 80 μm to 800 μm.
[0052]
If necessary, a solder resist layer is formed on the circuit pattern. As the solder resist, a photosensitive solder resist or a thermosetting solder resist is preferable. Among them, it is more preferable to use a photosensitive solder resist for a fine circuit pattern. Apply a photosensitive solder resist on the circuit pattern with a spin coater, blade coater, roll coater, bar coater, die coater, screen printer, etc., dry it, expose it to ultraviolet light through a predetermined photomask, and develop Thus, a solder resist pattern is obtained. Next, curing is performed at 100 ° C. to 200 ° C.
[0053]
The circuit board obtained by the manufacturing method of the present invention is used, for example, as a wiring board for an electronic device, a wiring board for an interposer wafer level burn-in socket for an IC package, and the like. In particular, when connecting electronic components such as ICs, the effect of improving the alignment accuracy between the electrode pads and the circuit board pattern is great. Including a resistor or a capacitor in the circuit pattern is appropriately permitted. Further, an insulating layer and a wiring layer can be laminated on at least one surface of the flexible film substrate to form a multilayer structure.
[0054]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.
[0055]
Example 1
As a flexible film, a polyimide film ("Kapton" 100EN, manufactured by Toray Dupont Co., Ltd.) having a thickness of 25 m and a square size of 290 mm was prepared.
[0056]
A UV-curable adhesive "SK Dyne" SW-22 (manufactured by Soken Chemical Co., Ltd.) and a curing agent L45 (Soken Chemical Co., Ltd.) were applied to a reinforcing plate of 1.1 mm thick, 300 mm square aluminoborosilicate glass using a die coater. (Manufactured by Co., Ltd.) in a ratio of 100: 3 (weight ratio), and dried at 80 ° C. for 2 minutes to form a 2 μm-thick peelable organic layer after drying. Then, an air-blocking film composed of a film in which a silicone resin layer which was easy to release was provided on a polyester film was stuck on the peelable organic material layer and left for one week.
[0057]
While peeling off the air-blocking film composed of the polyester film and the silicone resin layer, a polyimide film was adhered to the glass on which the re-peeling agent layer was formed by a roll laminator. Then, ultraviolet rays were applied from the glass substrate side at 1000 mJ / cm. ² Irradiation cured the removable layer.
[0058]
Then, a 6 nm thick chromium: nickel = 20: 80 (weight ratio) alloy film and a 200 nm thick copper film were laminated on the polyimide film in this order by sputtering. A positive photoresist was applied on the copper film by a spin coater and dried at 110 ° C. for 10 minutes. The photoresist was exposed and developed through a photomask to form a photoresist layer having a thickness of 10 μm in a portion where a plating film was not required.
[0059]
The test photomask pattern had the following shape.
[0060]
240 connection pads (width 25 μm, length 80 μm) are arranged on each side of a square having a length of 3.5 mm on each side of 240 squares. On each side, 240 bad pads (width: 50 μm, length: 100 μm) per side were arranged in 240 rows. A 300 mm square substrate is formed by connecting a connection pad on a square with a side length of 3.5 mm and a pad on a square with a side length of 30 mm one by one with a wiring having a width of 20 μm. It was arranged on the upper side at 40 mm pitch equally in 7 rows and 7 columns. In addition, four points of markers (located at a distance of 200 mm from each other in a direction parallel to the sides) arranged diagonally from the center of the substrate for measurement were provided on the photomask pattern.
[0061]
Next, a copper layer having a thickness of 5 μm was formed by electrolytic plating in a copper sulfate plating solution using the copper film as an electrode. The photoresist was stripped with a photoresist stripper, and then the copper film and the chromium-nickel alloy film under the resist layer were removed by soft etching with a hydrogen peroxide-sulfuric acid-based aqueous solution. Subsequently, a tin layer having a thickness of 0.4 μm was formed on the copper plating film by electroless plating to obtain a circuit pattern.
[0062]
Using a length measuring machine SMIC-800 (manufactured by Sokia Corporation), two points (about 200 mm in the x direction and 200 mm in the y direction) that were originally separated by about 283 mm in the diagonal direction and provided for the above-described length measurement. When the distance was measured, it was within ± 2 μm with respect to the photomask pattern, and the position accuracy was very well maintained.
[0063]
Next, a model IC chip of 4 mm × 4 mm in which four rows are arranged in a square with 60 gold-plated bumps arranged in a row at a pitch of 50 μm is mounted on a flip chip bonder FC-70 (manufactured by Toray Engineering Co., Ltd.) on the IC chip side. To 300 ° C., and metal-joined to the connection pads of the circuit pattern. The alignment between the bumps of the model IC chip and the connection pads of the circuit pattern was good.
[0064]
Next, a 20 wt% aqueous solution of polyvinyl alcohol was applied on the circuit pattern as a release assisting layer, and dried at 90 ° C. for 20 minutes. The thickness of the dried polyvinyl alcohol layer was 20 μm.
[0065]
The glass substrate side was sucked on a stage with a vacuum suction mechanism. The polyimide film with the circuit pattern on which the polyvinyl alcohol layer was formed was gripped with fingers at both ends of one side of the film, and peeled from the glass substrate in parallel to the opposite side. The polyimide film returned to flat after peeling, and no deformation such as breakage was observed in the circuit pattern on the polyimide film.
[0066]
Next, the polyvinyl alcohol layer formed on the circuit board was washed away with water and dried to obtain a film circuit board. Using a length measuring machine SMIC-800 (manufactured by Sokia Corporation), two points (200 mm in the x direction and 200 mm in the x direction), which were originally provided at a distance of 283 mm in the diagonal direction and provided on the obtained film circuit board, were provided for the above-described length measurement. The distance (point 200 mm apart in the y direction) was measured and compared with that before peeling. The change in the distance was within ± 5 μm, and the distortion was very small and good.
[0067]
Example 2
A circuit pattern was obtained in the same manner as in Example 1.
[0068]
Using a length measuring machine SMIC-800 (manufactured by Sokia Corporation), two points (about 200 mm in the x direction and 200 mm in the y direction) that were originally separated by about 283 mm in the diagonal direction and provided for the above-described length measurement. When the distance was measured, it was within ± 2 μm with respect to the photomask pattern, and the position accuracy was very well maintained.
[0069]
Next, using a screen printing machine on the polyimide film from which the circuit pattern was obtained, solder resist "FLEX PHOTO IMAGE MASK" NPR-90 (manufactured by Nippon Polytech Co., Ltd.) ) Was printed in a pattern and dried at 90 ° C. for 30 minutes. Then, ultraviolet rays were applied to the solder resist layer at 500 mJ / cm. ² Irradiation and heat curing at 150 ° C. for 90 minutes. Finally, the ultraviolet light is 1500 mJ / cm ² Irradiation and post-exposure resulted in the formation of a solder resist layer. The thickness of the solder resist layer after thermosetting was 20 μm.
[0070]
Next, in the same manner as in Example 1, the IC chip was metal-bonded to the connection pads of the circuit pattern. The alignment between the bumps of the model IC chip and the connection pads of the circuit pattern was good.
[0071]
The glass substrate side was sucked on a stage with a vacuum suction mechanism. The polyimide film with the circuit pattern on which the solder resist layer was formed was gripped with fingers at both ends of one side of the film, and peeled from the glass substrate in parallel toward the opposite side. The polyimide film returned to flat after peeling, and no deformation such as breakage was observed in the circuit pattern on the polyimide film.
[0072]
Using a length measuring machine SMIC-800 (manufactured by Sokia Corporation), two points (200 mm in the x direction and 200 mm in the x direction), which were originally provided at a distance of 283 mm in the diagonal direction and provided on the obtained film circuit board, were provided for the above-described length measurement. The distance (point 200 mm apart in the y direction) was measured and compared with that before peeling. The change in the distance was within ± 7 μm, and the distortion was very small and good. Note that the solder resist layer used as the peeling auxiliary layer can be used as a solder resist after the film is peeled, and need not be removed.
[0073]
Example 3
In the same manner as in Example 1, a model IC chip and a polyimide film with a circuit pattern on which a polyvinyl alcohol layer was formed were obtained.
[0074]
The glass substrate side was sucked on a stage with a vacuum suction mechanism, one side of the film was aligned with the bus of a plastic cylinder having a diameter of 170 mm and a height of 300 mm, and the film was peeled off along the cylinder. The film after peeling was flat, and no deformation such as breakage was observed in the circuit pattern on the polyimide film.
[0075]
Next, the polyvinyl alcohol layer formed on the circuit board was washed away with water and dried to obtain a film circuit board. Using a length measuring machine SMIC-800 (manufactured by Sokia Corporation), two points (200 mm in the x direction and 200 mm in the x direction), which were originally provided at a distance of 283 mm in the diagonal direction and provided on the obtained film circuit board, were provided for the above-described length measurement. The distance (point 200 mm apart in the y direction) was measured and compared with that before peeling. The change in the distance was within ± 5 μm, and the distortion was very small and good.
[0076]
Example 4
A model IC chip and a polyimide film with a circuit pattern were obtained in the same manner as in Example 1 except that the thickness of the polyimide film was changed to 50 μm.
[0077]
Next, a 20 wt% aqueous solution of polyvinyl alcohol was applied on the circuit pattern as a release assisting layer, and dried at 90 ° C. for 20 minutes. The thickness of the dried polyvinyl alcohol layer was 20 μm.
[0078]
The glass substrate side was sucked on a stage with a vacuum suction mechanism. The polyimide film with the circuit pattern on which the polyvinyl alcohol layer was formed was gripped with fingers at both ends of one side of the film, and peeled from the glass substrate in parallel to the opposite side. The polyimide film returned to flat after peeling, and no deformation such as breakage was observed in the circuit pattern on the polyimide film.
[0079]
Next, the polyvinyl alcohol layer formed on the circuit board was washed away with water and dried to obtain a film circuit board. Using a length measuring machine SMIC-800 (manufactured by Sokia Corporation), two points (200 mm in the x direction and 200 mm in the x direction), which were originally provided at a distance of 283 mm in the diagonal direction and provided on the obtained film circuit board, were provided for the above-described length measurement. The distance (point 200 mm apart in the y direction) was measured and compared with that before peeling. The change in the distance was within ± 5 μm, and the distortion was very small and good.
[0080]
Comparative Example 1
A circuit pattern was obtained in the same manner as in Example 1, and the model IC chip was metal-bonded.
[0081]
The glass substrate side was adsorbed to a stage with a vacuum adsorption mechanism without forming a separation assisting layer. The polyimide film with the circuit pattern was gripped with fingers at both ends of one side of the film, and peeled from the glass substrate in parallel toward the opposite side. The film was peeled off while bending in an arch shape, and the polyimide film with a circuit pattern after peeling largely curled the circuit pattern inside. In addition, a part of the circuit pattern was broken at the edge of the model IC chip, and it could not be used as a product.
[0082]
Comparative Example 2
A circuit pattern was obtained in the same manner as in Example 1 except that the thickness of the polyimide film was changed to 50 μm, and a model IC chip was metal-bonded.
[0083]
The glass substrate side was adsorbed to a stage with a vacuum adsorption mechanism without forming a separation assisting layer. The polyimide film with the circuit pattern was gripped with fingers at both ends of one side of the film, and peeled from the glass substrate in parallel toward the opposite side. The peeled polyimide film with the circuit pattern slightly curled with the circuit pattern inside, and the flatness was impaired.
[0084]
Using a length measuring machine SMIC-800 (manufactured by Sokia Corporation), two points (200 mm in the x direction and 200 mm in the x direction), which were originally provided at a distance of 283 mm in the diagonal direction and provided on the obtained film circuit board, were provided for the above-described length measurement. The distance (point 200 mm apart in the y-direction) was measured and compared with that before peeling.
[0085]
【The invention's effect】
According to the present invention, the flexible film with the circuit pattern attached to the reinforcing plate can be peeled off without breaking or distortion, and further, it is possible to make the dimensional change of the flexible film at the time of peeling small, High quality film circuit boards can be manufactured.

Claims (5)

A circuit board member in which a reinforcing plate, a peelable organic material layer, a flexible film having a circuit pattern on one or both sides, and a peeling auxiliary layer are laminated in this order. 2. The circuit board member according to claim 1, wherein an electronic component is bonded to the circuit pattern of the flexible film. 2. The circuit board member according to claim 1, wherein the release assist layer is a solder resist. Forming a peeling auxiliary layer on a flexible film having a circuit pattern on one or both sides attached to a reinforcing plate via a peelable organic material layer, and then peeling the flexible film from the reinforcing plate A method of manufacturing a circuit board. 5. The method for manufacturing a circuit board according to claim 4, wherein the release assist layer is a solder resist.