JP2007194324A - Member for circuit board, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a member for a circuit board capable of bonding a semiconductor element and a circuit pattern with a high accuracy without peeling of the circuit board and a reinforcing board. <P>SOLUTION: In the circuit board, a through-hole 108 is formed between a first surface and a second surface within 5 mm from the stepped section of the first surface of a flexible film 103 having circuit patterns 102 and 124 on both surfaces. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a circuit board having a highly accurate circuit pattern and a method for manufacturing the circuit board.

  As electronics products become lighter and smaller, printed circuit board patterning needs to be highly accurate. Among them, the demand for flexible film substrates is increasing because three-dimensional wiring is possible due to its flexibility and it is suitable for downsizing of electronic products. For example, the TAB (Tape Automated Bonding) technology used for IC (Integrated Circuit) connection to a liquid crystal display panel is to process a relatively narrow wide polyimide film substrate to produce the finest level pattern as a resin substrate. Although it can be obtained, the progress of miniaturization is approaching the limit. For miniaturization, there are an index represented by a line width and a space width between lines, and an index represented by a position of a pattern on a substrate. The latter index, so-called positional accuracy, is related to the alignment of the electrode pad and the circuit board pattern when connecting the circuit board and the electronic component such as an IC, and the required accuracy is severe as the number of pins of the IC increases. It has become to.

  In view of the above positional accuracy, the flexible film substrate processing is becoming difficult to improve. Circuit board processing includes heat treatment processes such as drying and curing, and wet processes such as etching and development, and the flexible film repeatedly expands and contracts. The hysteresis at this time causes displacement of the circuit pattern on the substrate. In addition, when there are a plurality of processes that need alignment, if there is expansion or contraction between these processes, positional deviation occurs between the formed patterns. The deformation due to the expansion and contraction of the flexible film has a greater influence in the case of an FPC (Flexible Printing Circuit) in which processing is performed with a relatively large substrate size. Further, the positional shift is caused by an external force such as pulling or twisting, and special attention is required when a thin substrate is used to increase flexibility.

  On the other hand, a reinforcing plate is bonded to the flexible film to be formed with a peelable organic layer to control expansion and contraction of the flexible film and increase the overall strength. There is a proposal of forming a circuit pattern while suppressing deformation due to external force and peeling the flexible film with the circuit pattern from the reinforcing plate (see Patent Document 1).

  There is an increasing demand for higher performance of semiconductor elements and modularization by mounting multiple elements. From a circuit board on which a circuit pattern is formed only on one side of a flexible film, a circuit pattern with multiple layers on both sides. There is a need for multilayer circuit boards having: Advantages of multi-layer wiring include crossing of wiring via through holes and via holes, increasing the degree of freedom in wiring design, and high speed by propagating thick wiring and ground potential near the required location The noise of the operating semiconductor element can be reduced. Similarly, the power supply potential can be propagated to the vicinity of the necessary place with a thick wiring to prevent the potential from being lowered even at high-speed switching, and the operation of the semiconductor element can be stabilized. As a general manufacturing method of a multilayer circuit board, a build-up method can be mentioned. Various manufacturing methods have been proposed as a method for manufacturing a circuit board member with high accuracy using this build-up method (see Patent Document 2). According to this, (A) a circuit pattern is formed using a resist process or a plating process after a reinforcing plate is bonded to a flexible film on which a circuit pattern is to be formed via a peelable organic layer. If necessary, a solder resist film is formed on the circuit pattern. (B) A flexible film with a circuit pattern is transferred to another reinforcing plate via a peelable organic layer, (C) a circuit pattern is formed on the other surface, and (D) a flexible with a circuit pattern. The adhesive film is peeled off.

  In a circuit pattern for mounting a liquid crystal driver IC, a portion connected to a semiconductor element is called an inner lead, and gold plating or tin plating is usually used as the surface finish of the inner lead. The surface of the electrode pad of the semiconductor element is usually gold-plated, and is connected to the inner lead gold-plating or tin-plating, and pressure and temperature are applied to perform highly reliable bonding by gold-gold bonding or gold-tin bonding. . It is important that the inner lead is not greatly sunk into the flexible film by the pressure at this time. When the inner lead sinks greatly, a part of the inner lead is peeled off or broken from the flexible film, and the reliability is remarkably lowered. Usually, there is no problem with a simple configuration in which inner leads are provided on a flexible film typified by polyimide. However, an organic material layer having a relatively low hardness such as a solder resist is located between the flexible film and the reinforcing plate below the inner leads. In some cases, the sinking of the inner lead may increase.

  In order to suppress sinking of the inner lead to the flexible film side in the semiconductor element bonding step, it is preferable not to form an organic layer other than the flexible film in the vicinity of the region where the semiconductor element is bonded. A level difference occurs due to the presence of a portion where the organic material layer is formed and a portion where the organic layer is not formed on the bonding surface of the flexible film to the reinforcing plate. That is, when a flexible film having a circuit pattern formed on one surface is bonded to a reinforcing plate via an organic layer that can be peeled off, an organic layer such as a solder resist is formed. A gap is formed between the flexible film and the reinforcing plate at the step portion between the portion and the portion not formed. In the state where only the circuit pattern made of metal is formed without providing the solder resist, even when this surface is bonded to the reinforcing plate, a gap is formed in the stepped portion due to the presence or absence of the circuit pattern.

In order to obtain high-precision bonding between the semiconductor element and the circuit board, it is preferable to bond the semiconductor element in a state where the circuit board is bonded to a reinforcing plate having excellent dimensional stability. However, if there is a gap in the bonding surface, rapid heating during bonding of the semiconductor element causes rapid expansion of the gas in the gap, vaporization of adsorbed water, vaporization of water contained in the flexible film, etc. Expansion may occur, and the reinforcing plate and the circuit board may be peeled around the gap, resulting in misalignment between the electrode pads of the semiconductor element and the inner leads of the circuit board, and high precision bonding may not be possible. It was.
JP 2003-298194 A JP 2004-140254 A

  In view of the above-described problems, an object of the present invention is to provide a circuit board having a highly accurate circuit pattern and capable of bonding semiconductor elements with high precision, and a method for manufacturing the circuit board.

That is, this invention consists of the following structures.
(1) A circuit board in which a through-hole is formed between the first surface and the second surface within 5 mm from the step portion of the first surface of the flexible film having circuit patterns on both surfaces.
(2) A circuit board having a step on at least one side of a flexible film having a circuit pattern on both sides, the first surface having the step being fixed to a reinforcing plate via a peelable organic layer, A circuit board member in which a through hole is formed between a first surface and a second surface within 5 mm from a step portion generated between a reinforcing plate and a circuit board due to a step.
(3) The circuit board member according to (2), wherein at least a part of the through-hole is formed so as to be stepped.
(4) A step of fixing a first surface having a step of a circuit board having a step on at least one side of a flexible film having a circuit pattern on both sides to a reinforcing plate via a peelable organic layer, and fixing A method for manufacturing a circuit board member, comprising: forming a circuit pattern on a second surface opposite to the surface; and forming a through-hole in the flexible film from the second surface within 5 mm from the step.
(5) The method for manufacturing a circuit board member according to (4), wherein at least a part of the through-hole is formed so as to be stepped.

  According to the present invention, when the semiconductor element is bonded with the stepped surface bonded to the reinforcing plate, even if there is a gap due to the step near the bonded portion, the circuit board and the reinforcing plate are not separated. The element and the circuit pattern can be joined with high accuracy.

  In the present invention, the flexible film is a plastic film, and preferably has heat resistance sufficient to withstand the thermal process in the circuit pattern forming step and electronic component mounting. Polycarbonate, polyether sulfide, polyethylene terephthalate Films such as polyethylene naphthalate, polyphenylene sulfide, polyimide, polyamide, and liquid crystal polymer can be employed. Among these, a polyimide film is preferably used because it is excellent in heat resistance and chemical resistance. In addition, a liquid crystal polymer is preferably used because it has excellent electrical characteristics such as low dielectric loss. It is also possible to employ a flexible glass fiber reinforced resin plate. Examples of the resin for the glass fiber reinforced resin plate include epoxy, polyphenylene sulfide, polyphenylene ether, maleimide, polyamide, and polyimide.

  The thickness of the flexible film is preferably thinner in order to reduce the weight and size of electronic devices, or to form fine via holes. On the other hand, in order to ensure mechanical strength and maintain flatness. From the viewpoint that a thicker one is preferable, a range of 4 μm to 125 μm is preferable.

  In the present invention, a method for forming a circuit pattern is not particularly limited. For example, a circuit pattern can be formed by a subtractive method by attaching a metal foil such as a copper foil with an adhesive layer, or by sputtering or plating. Alternatively, a circuit pattern can be formed by a subtractive method, a semi-additive method, or a full additive method by combining these. In addition, a flexible film with a metal layer is obtained by applying, drying, and curing a raw material resin of a flexible film or a precursor thereof on a metal foil such as copper, and a pattern is formed by a subtractive method. You can also.

  The substrate used as the reinforcing plate in the present invention includes inorganic glasses such as soda lime glass, borosilicate glass, and quartz glass, metals such as invar alloy, stainless steel, and titanium, ceramics and glass such as alumina, zirconia, and silicon nitride. A fiber-reinforced resin plate can be used. Both are preferable because of their low linear expansion coefficient and hygroscopic expansion coefficient, but they are excellent in heat resistance and chemical resistance in the circuit pattern manufacturing process, and are easy to obtain inexpensively because of their large area and high surface smoothness. A substrate made of inorganic glass is preferable in that it is difficult to be plastically deformed. Among them, soda lime glass is preferable because it has a large thermal expansion coefficient in glass and is close to the linear expansion coefficient of a resin film.

  When a metal or glass fiber reinforced resin is used for the reinforcing plate, it can be manufactured as a long continuous body, but the method for manufacturing a circuit board of the present invention should be a single wafer type because it is easy to ensure positional accuracy. Is preferred. A sheet means a state where it is handled as an individual sheet, not a long continuous body.

  The peelable organic layer used in the present invention is composed of an adhesive or a pressure-sensitive adhesive, and the flexible film is attached to a reinforcing plate through the peelable organic layer and processed. It can be peeled off. Examples of such an adhesive or pressure-sensitive adhesive include a pressure-sensitive adhesive called an acrylic or urethane-based re-peeling pressure-sensitive adhesive. Moreover, since the molecular design can be easily performed and the solvent resistance is excellent, what is called a cross-linked type in which a main agent of an adhesive or a pressure-sensitive adhesive and a curing agent are mixed is preferable. In order to heat and pressurize and bond the semiconductor element with the circuit board bonded to the reinforcing plate, the peelable organic material layer is preferably an ultraviolet curing type and is cured before bonding the semiconductor element.

  If the thickness of the peelable organic layer is too small, the uniformity tends to decrease. Therefore, the thickness is preferably 0.1 μm or more, and more preferably 0.3 μm or more. On the other hand, if the thickness of the peelable organic layer is too large, the anchoring property to the flexible film is improved and the peeling force tends to be too large. Therefore, it is preferably within 20 μm, and is preferably within 10 μm. More preferably. When bonding electronic components to a circuit pattern on a flexible film fixed via a peelable organic layer on the reinforcing plate, the thickness of the peelable organic layer is used to suppress changes 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 change of the peelable organic material layer is large, and the circuit pattern of the joint portion sinks, which may cause a problem in the reliability of the wiring circuit. When the sinking is large, the circuit pattern may come into contact with the edge of the electrical component to cause a short circuit. The sinking is preferably 6 μm or less and more preferably 3 μm or less in order to ensure the reliability of the wiring circuit.

  The peeling interface may be either the interface between the reinforcing plate and the peelable organic layer or the peelable organic layer and the flexible film, but the step of removing the peelable organic layer from the flexible film Therefore, it is preferable to peel off at the interface between the peelable organic layer and the flexible film.

  In order to improve the peeling force between the reinforcing plate and the peelable organic layer, the reinforcing plate may be subjected to a primer treatment such as application of a silane coupling agent. In addition to the primer treatment, cleaning by ultraviolet treatment, ultraviolet ozone treatment, etc., surface roughening treatment such as chemical etching treatment, sand blast treatment or fine particle dispersion layer formation is also preferably used.

  An example of a method for manufacturing a circuit board according to the present invention will be described below with reference to FIG. Apply a silane coupling agent to a 1.1mm thick soda lime glass 101 ((1) in Fig. 1) using a spin coater, blade coater, roll coater, bar coater, die coater, screen printer, etc. To do. In order to uniformly apply a thin film of a silane coupling agent having a relatively low viscosity to a single substrate that is intermittently sent, it is preferable to use a spin coater. After application of the silane coupling agent, drying is performed by heat drying or vacuum drying to obtain a silane coupling agent layer having a thickness of 20 nm.

  Next, an ultraviolet curable re-peeling adhesive is applied on the silane coupling agent layer with a spin coater, blade coater, roll coater, bar coater, die coater, screen printer or the like. The use of a die coater is preferable in order to uniformly apply a relatively high-viscosity adhesive to the intermittently fed single wafer substrate. After applying the ultraviolet curable re-peeling adhesive, drying is carried out by heat drying or vacuum drying to obtain an ultraviolet curable organic layer 122 having a thickness of 3 μm ((1) in FIG. 1). An air-blocking film in which a silicone resin layer is provided on a polyester film is attached to the ultraviolet curable organic material layer and aged for one week. 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 an ultraviolet curable organic layer to a long film substrate, dry it, and then transfer it to a single wafer substrate.

  In the present invention, the ultraviolet curable organic material layer may be initially formed on the flexible film side, may be formed on the reinforcing plate side, or may be formed on both. In order to control the ease of formation and the peeling interface to be a flexible film and an ultraviolet curable organic material layer, it is preferably formed on the reinforcing plate side.

  A polyimide film having a thickness of 38 μm, which is a flexible film, is prepared. Peel off the air barrier film on the glass and attach the plastic film to the glass. A circuit pattern layer may be formed in advance on one or both sides of the polyimide film.

  In the present invention, the circuit pattern 104 and the solder resist film 151 and the barrier metal layer 152 as a protective film are formed in advance on the bonding side of the polyimide film 103 with the glass on the bonding side ((2) in FIG. 1). When the circuit pattern on the side of the polyimide film bonded to the glass is intended for wiring crossing or when low impedance thick wiring is used, a long polyimide film is formed by a reel-to-reel method, not a fine pitch. can do. On the other hand, when a fine pitch circuit pattern is required on both sides, a circuit pattern on one side is formed using the technique employed in the present invention in which a polyimide film is bonded to a reinforcing plate to form a circuit pattern. A method of transferring this surface as a bonding surface with glass can be employed.

  When one circuit pattern is formed on a long polyimide film, the polyimide film may be attached in a cut sheet of a predetermined size in advance. May be. For such a pasting operation, a method of laminating the polyimide film on the glass side with low stress and high accuracy by holding the polyimide film on the surface of the flexible planar body and then pressing it onto the glass is suitable. Can be adopted.

  A laminating apparatus used in the above method will be described with reference to FIG. FIG. 2 is a schematic front view of the laminating apparatus. The flexible sheet 202 is charged by the electrostatic charging device 201 to adsorb the polyimide film 203. A flexible fabric or thin film can be used for the flexible planar body 202 and is fixed to the frame body 204. In addition, the electrostatic charging device 201 is supported by a support 206 on the base 205, and the support 206 includes a frame 204 and a mounting table 207 that move to the left and right and an electrostatic charging device 201 by a vertical movement mechanism (not shown). Move so as not to interfere. Next, the glass 209 coated with the ultraviolet curable organic material layer 208 is held on the mounting table 207 by vacuum suction or the like. The polyimide film 203 is pressed against the peelable organic layer 208 together with the flexible planar body 202 with the squeegee 210, and the polyimide film 203 is transferred to the glass 209 side. The squeegee 210 is held by a squeegee holder 211 and can be moved and moved up and down. The mounting table 207 can be moved to the left and right in the figure by a rail 212, a guide 213, a nut 214, a bracket 215, a ball screw 217, and a motor 218.

  A protective film such as a solder resist is formed on the circuit pattern, but in order to suppress the sinking of the inner lead to the flexible film side in the bonding process of the semiconductor element, it is near the area where the semiconductor element is bonded. Since an organic layer other than the flexible film is not formed, a step due to the presence of a part where the solder resist is formed and a part where the solder resist is not formed occurs in the region where the semiconductor element is bonded. A gap 107 is formed around the step ((2) in FIG. 1).

  After the polyimide film is attached to the glass 101, the ultraviolet curable organic material layer 122 formed on the polyimide film is irradiated with ultraviolet rays to promote crosslinking ((2) in FIG. 1).

  When a circuit pattern made of metal is not provided in advance on the surface opposite to the bonded surface of the polyimide film, the circuit pattern can be formed by a full additive method or a semi-additive method.

  The full additive method is, for example, the following process. The surface on which the circuit pattern is to be formed is treated with a catalyst such as palladium, nickel or chromium, and dried. The catalyst referred to here does not act as a nucleus for plating growth as it is, but it becomes a nucleus for plating growth by activation treatment. Next, the photoresist is applied by a spin coater, a blade coater, a roll coater, a bar coater, a die coater, a screen printer 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 the plating film is unnecessary. Then, 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.

  The semi-additive method is, for example, the following process. On the surface on which the metal layer is to be formed, chromium, nickel, copper or an alloy thereof is sputtered to form an underlayer. The thickness of the underlayer is usually in the range of 1 nm to 1000 nm. It is preferable to stack a copper sputtered film on the underlayer of 50 nm to 3000 nm in order to ensure sufficient conduction for subsequent electrolytic plating, to improve the adhesion of the metal layer, and to prevent pinhole defects. Prior to the formation of the underlayer, plasma treatment, reverse sputtering treatment, primer layer coating, and adhesive layer coating are appropriately used to improve the adhesion on the polyimide film surface. Among them, the application of an adhesive layer such as epoxy resin, acrylic resin, polyamide resin, polyimide resin, and NBR is preferable because it has a great effect of improving the adhesive force. These treatments and application may be performed before being attached to glass or after being attached to glass. It is preferable to continuously treat a long polyimide film by a reel-to-reel method before attaching the glass, in order to improve productivity. A photoresist is applied onto the underlayer thus formed by a spin coater, blade coater, roll coater, die coater, screen printer, 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 the plating film is unnecessary. Next, electrolytic plating is performed using the base 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 with a thickness of 2 μm to 20 μm, the photoresist is peeled off, and then the underlying layer is removed by a light etching, and further, gold, nickel, tin, etc. are plated as necessary to obtain a circuit pattern. Get. In addition to the semi-additive method and the full additive method described above, a circuit pattern can be formed on the surface opposite to the bonding surface by a subtractive method. The subtractive method is a method in which a metal layer is formed on a polyimide film, and a circuit pattern is formed using a photoresist and an etching solution. In particular, in order to obtain a high-definition circuit pattern, it is preferable to employ a semi-additive method or a full additive method.

  Furthermore, the connection hole 105 can be provided in a polyimide film ((3) of FIG. 1). That is, it is possible to provide a via hole for making an electrical connection between the circuit pattern provided on the glass bonding surface side and the circuit pattern on the opposite surface, or to provide a ball mounting hole for the ball grid array. . As a method for providing the connection hole, laser drilling such as a carbon dioxide laser, YAG laser, or excimer laser, or chemical etching can be employed. When laser drilling is employed, it is preferable that a metal layer is present on the glass attachment surface side of the polyimide film as an etching stopper layer.

  As the chemical etching solution for the polyimide film, hydrazine, potassium hydroxide aqueous solution, or the like can be used. Further, a patterned photoresist or a metal layer can be employed as the chemical etching mask. When electrical connection is made, it is preferable that after the connection hole is formed, the inner surface of the hole is made into a conductor by plating at the same time as the circuit pattern is formed. The diameter of the connection hole for electrical connection is preferably 15 μm to 200 μm. The hole for installing the ball preferably has a diameter of 80 μm to 800 μm.

  The timing for forming the connection holes is not limited. However, in the case of a multilayer circuit board, a circuit pattern is formed on one side of the polyimide film, and the circuit formation side of the polyimide film is bonded to another glass. It is preferable to form the connection hole from the opposite surface of the mating surface.

  Next, a circuit pattern 124 is formed on the opposite surface of the polyimide film attachment surface by a semi-additive method, a full additive method, or a semi-additive method ((4) in FIG. 1). If necessary, a solder resist film 153 and a barrier metal layer 154 are formed on the circuit pattern ((5) in FIG. 1). For photosensitive solder resist, spin coater, blade coater, roll coater, bar coater, die coater, screen printer, etc., apply the photosensitive solder resist on the circuit pattern, let it dry, and then apply a predetermined photomask. And exposing to ultraviolet light and developing to obtain a solder resist pattern. Next, curing is performed at 100 ° C. to 200 ° C. Further, it can be cured by pattern printing with a screen printer using a non-photosensitive solder resist.

  In order to suppress the sinking of the inner lead when the semiconductor element 109 is bonded, a solder resist is not formed in a region where the semiconductor element 109 is bonded, so that a step is formed from the portion where the solder resist is formed. Here, the level difference means the end of the solder resist where the solder resist is formed, and the end of the circuit pattern where the surface of the circuit pattern is coated with a gold or tin film that does not have a solder resist. To do. The thickness of the circuit pattern is often 6 μm or more, and the thickness of the solder resist formed on the circuit pattern is about 10 μm on the polyimide film and about 6 μm on the circuit pattern, so the step is 12 μm or more. Often becomes.

  In the bonding process of the semiconductor element 109, a circuit board temperature of 50 to 200 ° C., a semiconductor element temperature of 200 to 400 ° C., and a bonding pressure of 5 to 15 g per electrode pad of the semiconductor element are employed. When forming a high-definition circuit pattern on both surfaces of the polyimide film, it is preferable that the surface on which the circuit pattern is formed first is bonded to the glass also in the semiconductor element bonding step. Here, in the gap 107 around the step formed on the surface bonded to the circuit board and the glass, the gas in the gap expands due to a rapid temperature rise in the bonding process, the adsorbed water vaporizes, and the water contained in the polyimide film vaporizes. The circuit board and the glass may be peeled off due to swelling. Further, preheating is often performed by placing a circuit board on a stage immediately before bonding, but the circuit board may be peeled off from the glass during preheating reaching 150 to 180 ° C. in a few seconds. In the present invention, in order to prevent this, it is important to provide the through-hole 108 from the opposite side of the bonding surface with the glass around the step portion ((6) in FIG. 1).

  By forming the through hole 108, the gap formed by the level difference only advances to the through hole due to a rapid temperature rise in the bonding process of the semiconductor element 109, and in the semiconductor element bonding region outside the through hole. Since the polyimide film is attached to the glass, it can be joined with high accuracy. When the setting position of the through-hole is more than 5 mm away from the stepped portion, the adhesive force between the polyimide film and the glass due to the peelable organic material layer exceeds the force by which the polyimide film due to the development of the gap portion peels from the glass. The polyimide film in the bonding region of the semiconductor element may peel from the glass beyond the formation position. Therefore, it is important that the setting position of the through hole is provided within 5 mm from the stepped portion. Further, in order to minimize the progress of the gap 107, it is more preferable that at least a part of the through-hole is provided on the step portion.

  The shape of the through hole is preferably a hole similar to the connection hole of the circuit pattern on both sides of the polyimide film. In this case, the through hole preferably has a diameter of 15 μm to 200 μm. In order to obtain a greater effect, it is preferable to form a linear through hole extending in a direction perpendicular to the step or the gap. The extending direction of the through hole is not particularly limited to the vertical direction, and can be freely set in an area where the through hole can be arranged.

  As a method of providing the through-hole, similarly to the above-described connection hole, laser drilling such as a carbon dioxide laser, YAG laser, or excimer laser, or chemical etching can be employed. When the shape of the through hole is a hole, the diameter is preferably 15 μm to 200 μm. In the case of forming a linear through hole, the chemical etching may be performed by linear patterning using an etching mask, and in the case of laser drilling, a plurality of laser holes may be arranged so that a part of each of them overlaps.

  When the step of the wiring pattern on the polyimide film on the surface bonded to the glass is small, the width of the gap formed between the polyimide film and the glass is reduced, and the volume of the gap is also reduced. In the case of a step smaller than 6 μm, since the width of the gap is small and the volume in the gap is small, peeling between the circuit board and the glass is difficult to occur, and the bonding deviation between the semiconductor element and the circuit board hardly occurs. The present invention is effective.

  The timing for forming the through-hole 108 formed near the step formed on the circuit board and the glass is not particularly limited, but the hole is formed by forming simultaneously with the connection hole for connecting the circuit patterns on both sides of the polyimide film described above. It is possible to reduce the number of steps to be performed. However, it is necessary to prevent a metal layer or an organic material layer from being formed in the through hole in the circuit pattern forming process and the solder resist printing process after the through hole is formed. If they are formed in the through hole, the effect of removing the gas from the gap is greatly reduced. In the step of forming the circuit pattern, for example, it is necessary to cover with copper or the like in advance so that copper is not formed in the through hole by copper plating, and when formed, it is necessary to selectively remove it by etching. Also, in the solder resist printing process, when using a photosensitive resist, it is necessary to add a pattern to remove the resist around the through-hole in the exposure mask, and when using a non-photosensitive resist It is necessary to prepare a printing plate having a pattern that does not print the periphery of the through-hole on the screen printing plate. The timing for forming the through hole is preferably provided immediately before the bonding step for mounting the semiconductor element, and more preferably after the solder resist printing performed after all the circuit patterns are formed.

  Regarding the number of through-holes to be set, it is preferable to provide at least one through-hole in the stepped portion due to the presence or absence of the solder resist closest to the end portion of the bonding region of the semiconductor element. A mouth should be provided.

  After bonding the semiconductor elements, the polyimide film on which the circuit pattern is formed is peeled from the glass.

  FIG. 3 is a schematic front view of a peeling apparatus for explaining a preferable peeling method. Using the apparatus shown in FIG. 3, the polyimide film is peeled off along a curved surface obtained by cutting a part of a cylindrical shape, and the polyimide film is held in a state where the peeling angle formed by the reinforcing plate and the polyimide film is kept at an acute angle. The method of peeling from the edge part can be mentioned.

  First, an object to be peeled is set so that the reinforcing plate 301 side comes to the stage 305 (not shown). The stage 305 is raised by an air cylinder (not shown), and the peeling start position of the polyimide film 303 bonded via the reinforcing plate 301 and the ultraviolet curable organic material layer 302 and the predetermined position of the curved surface 304 (S in FIG. 3). Contact). One end of the polyimide film 303 is held by a vacuum chuck or the like built in the curved surface 304, and then the movable body 306 that holds the curved surface is rotated to peel the polyimide film along the curved surface 304. At this time, in synchronization with the rotation of the movable body 306, the stage 305 moves rightward on the rail 308, and moves the peeling point leftward on the substrate. When the polyimide film to which the electronic component is connected is peeled off, a groove is provided in accordance with the position of the electronic component in order to absorb the thickness of the electronic component on the curved surface 304, or the surface of the curved surface 304 is cushioned. It is preferably covered with a plastic foam sheet. After the completion of peeling, the holding body 307 is moved rightward along the rail 308, and the polyimide film peeled off on the stage 309 is taken out.

  It is preferable to use a laser, a high-pressure water jet, a cutter, or the like to cut the polyimide film with a circuit pattern into individual pieces or an assembly of individual pieces before peeling because the handling becomes easy. Furthermore, in order to maintain the positional accuracy of the connection with the electronic component, it is preferable to peel the polyimide film from the glass after connecting the electronic component to the circuit pattern on the polyimide film. As a connection method with an electronic component, for example, solder connection, connection using an anisotropic conductive film, connection using a metal eutectic, connection using a non-conductive adhesive, wire bonding connection, or the like can be employed. Also, when peeling the entire surface of the polyimide film from the glass, peeling off the UV curable organic layer after irradiating the UV curable organic layer after forming the circuit pattern will reduce the peeling force at the periphery of the polyimide film, making it easy to peel off. Become.

  Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

Example 1
The circuit pattern of the double-sided circuit board was designed as follows. On the surface to which the semiconductor element is bonded ((1) in FIG. 4, that is, the surface opposite to the surface to be bonded to the glass as the reinforcing plate), 25 μm pitch is provided on two long sides of a rectangle of 15 mm × 2 mm as inner leads. Then, the rectangular bonding pads 411 having a size of 10 μm × 50 μm were arranged 600 pieces per side. Further, 20 pieces of 10 μm × 50 μm rectangular bonding pads 401 were arranged at a pitch of 25 μm on one short side of the same 15 mm × 2 mm rectangle. The center of the 50 μm side of the bonding pad was placed on the long side and the short side of the rectangle, respectively. In addition, as outer leads, on the two long sides of the 30 mm × 25 mm rectangle, which is the same as the rectangle of the inner lead bonding pad arrangement, 600 pieces per side with a rectangular pitch of 24 μm × 50 μm at a pitch of 50 μm. The pads 412 were arranged. In addition, a rectangular bonding pad 407 of 24 μm × 50 μm was arranged on the short side opposite to the short side where 20 bonding pads were arranged as inner leads with the same 30 mm × 25 mm. The inner lead bonding pad 411 and the outer lead bonding pad 412 were connected by a wiring (not shown) having a width of 10 μm. Also, on the surface to be bonded to the glass ((2) in FIG. 4), each of the 20 wires having a circuit pattern width of 50 μm at a pitch of 100 μm is parallel between the inner lead and the outer lead in one long side direction. Lined up. Both ends of the wiring 404 are connected to wirings 403 and 406 having a width of 10 μm arranged on the surfaces to which the semiconductor elements are bonded by 20 conduction holes 403 and 405 each having a diameter of 100 μm. Further, since the wiring 402 is electrically connected to the inner lead 401 and the wiring 406 is electrically connected to the outer lead 407, the outer lead 406 is electrically connected to the inner lead 401. The wirings 404 are all covered with a solder resist, and the solder resist end 408 is designed to be formed at a position 10 mm from the bonding region end 413 of the rectangular semiconductor element on the outer lead side. These units were regarded as one unit, and the units were arranged in such a manner that the glass was equally distributed from the center in the direction of the length of 300 mm, and 5 rows were adjacent to each other at a pitch of 48 mm. Fourteen glasses were arranged at a pitch of 23.75 mm, equally spaced from the center in the 350 mm length direction. When the glass is 350 mm long, the distance between the units is 0.75 mm.

  A polyimide film having a thickness of 38 μm and a width of 300 mm (trade name “Kapton” 150EN manufactured by Toray Du Pont Co., Ltd.) was prepared as a flexible film. A long polyimide film is mounted on a reel-to-reel sputtering apparatus, and a 10 nm thick chromium: nickel = 20: 80 (weight ratio) alloy film and a 1000 nm thick copper film are arranged in this order on the polyimide film. Laminated. To a soda-lime glass with a thickness of 1.1 mm and 300 × 350 mm, a UV curable adhesive, trade name “SK Dyne” SW-22 (manufactured by Soken Chemical Co., Ltd.) and a curing agent L45 (Soken Chemical ( Co., Ltd.) was mixed at 100: 3 (weight ratio) and dried at 80 ° C. for 2 minutes to provide an ultraviolet curable pressure-sensitive adhesive layer. The thickness of the ultraviolet curable pressure-sensitive adhesive layer after drying was 3 μm. Next, an air-blocking film made of a film in which a silicone resin layer that can be easily released was provided on a polyester film was bonded to the ultraviolet curable pressure-sensitive adhesive layer, and left for one week.

A polyimide film provided with a metal layer was cut out to 300 × 350 mm. After peeling off the air blocking film, a polyimide film provided with a metal layer was bonded to an organic layer that can be peeled off with a laminator. Thereafter, the ultraviolet curable pressure-sensitive adhesive layer was irradiated with 1000 mJ / cm ^{2 of} ultraviolet light from the soda lime glass side, and the ultraviolet curable pressure-sensitive adhesive layer was photocured.

  A positive photoresist was applied onto the copper layer with a spin coater and dried at 80 ° C. for 10 minutes. The photoresist was exposed and developed through a photomask to form a photoresist layer having a thickness of 15 μm in a portion where the plating layer was unnecessary.

  Next, a copper layer having a thickness of 8 μm was formed by electrolytic plating in a copper sulfate plating solution using the copper layer as an electrode. The photoresist was stripped with a photoresist stripper, and then the copper layer and the chromium-nickel alloy layer under the resist layer were removed by soft etching with a hydrogen peroxide-sulfuric acid aqueous solution to form a circuit pattern. . Then, the protective film for protecting a circuit pattern was formed on the circuit pattern with the screen printer. Solder resist FS-510T (manufactured by Ube Industries) was used as the protective film. The film was cured at 120 ° C. for 90 minutes in an oven to obtain a 10 μm thick protective film. Thereafter, a barrier metal layer 152 was formed in the opening of the solder resist by electrolytic gold plating. The end of the polyimide film did not peel from the end of the glass during the circuit pattern forming process.

  Next, the circuit pattern surface previously formed on the polyimide film was bonded to another soda lime glass 101 coated with the ultraviolet curable adhesive 122 with a laminating apparatus (see FIG. 2). At this time, the level difference due to the solder resist was about 12 μm. As a result, a gap was generated between the polyimide film and soda lime glass around the step. Subsequently, the connection holes for connecting the circuit patterns on both sides were processed with a UV-YAG laser. The opening diameter of the connection hole was 100 μm.

  Thereafter, chromium-nickel alloy and copper are sputtered with a single-wafer sputtering apparatus to form an underlayer. The thickness of the underlayer was 10 nm of chromium: nickel = 20: 80 (weight ratio) alloy film and copper 1000 nm. Subsequently, a positive photoresist was applied onto the underlayer with a spin coater and dried at 80 ° C. for 10 minutes. The photoresist was exposed and developed through a photomask to form a photoresist layer having a thickness of 15 μm in a portion where the plating layer was unnecessary.

  A copper layer having a thickness of 8 μm was formed by electrolytic plating in a copper sulfate plating solution using the copper layer as an electrode. The photoresist is stripped with a photoresist stripping solution, and then the copper layer and the chromium-nickel alloy layer under the resist layer are removed by soft etching with a hydrogen peroxide-sulfuric acid aqueous solution to form a circuit pattern 124. did. Then, in order to protect a circuit pattern with a screen printing machine, solder resist FS-510T (made by Ube Industries) was formed on the circuit pattern. Cure at 120 ° C. for 90 minutes in an oven to obtain a 10 μm thick solder resist layer. Thereafter, a barrier metal layer 154 was formed on the inner lead portion by electrolytic gold plating.

  Here, the UV-YAG laser was used to form the through-hole 108 so as to cover the gap 107. The opening diameter of the through hole was 100 μm, similar to the connection hole diameter. The through-hole avoids wiring arranged on the surface on which the semiconductor element is mounted for a total of 40 pieces per side with respect to the steps on the four sides of the solder resist formed on the polyimide film on the surface bonded to the glass. Arranged.

After irradiating the ultraviolet curable adhesive layer with 1000 mJ / cm ² from the glass side with the reinforcing plate attached, the semiconductor element is bonded to the circuit board with a bonding device (FC-2000, manufactured by Toray Engineering Co., Ltd.). I let you. Bonding was performed under the bonding conditions of a temperature of 400 ° C., 10 g per inner lead, and a bonding time of 1 second, but the polyimide film did not peel from the glass.

  Subsequently, the 300 × 350 mm polyimide film substrate was gradually peeled from the glass at the end of the polyimide film using the apparatus of FIG. There was no cracking or cracking of the semiconductor element after peeling, and no warpage or breakage due to peeling of the polyimide film occurred. Further, when the connection state between the inner leads of the circuit board and the bonding pads of the semiconductor element was observed with a microscope from the polyimide surface, good bonding without positional deviation was performed with all the bonding pads.

Example 2
A double-sided substrate having a circuit pattern was produced in the same manner as in Example 1 except that the through hole was formed at a position 3 mm away from the stepped portion, and the semiconductor elements were bonded. Although the gap became larger during the preheating and bonding, when it reached the through-hole, it did not further develop, and the polyimide film in the bonding region of the semiconductor element did not peel from the glass. Further, when the bonding pad portion was observed from the glass side, good bonding with no positional deviation was performed on all bonding pads.

Example 3
A double-sided substrate having a circuit pattern was produced in the same manner as in Example 1 except that the through hole was formed at a position 5 mm away from the stepped portion, and the semiconductor elements were bonded. Although the gap became larger during the preheating and bonding, when it reached the through-hole, it did not further develop, and the polyimide film in the bonding region of the semiconductor element did not peel from the glass. Further, when the bonding pad portion was observed from the glass side, good bonding with no positional deviation was performed on all bonding pads.

Comparative Example 1
A double-sided substrate having a circuit pattern was prepared in the same manner as in Example 1 except that no through hole was formed, and semiconductor elements were bonded. It was confirmed that the gap 107 greatly progressed during the stage heating during bonding, and the polyimide film in the region where the semiconductor element was bonded peeled from the glass. Moreover, in the observation after joining, joining deviation | shift was confirmed by many joining pads by peeling of the above-mentioned polyimide film.

Comparative Example 2
A double-sided substrate having a circuit pattern was prepared in the same manner as in Example 1 except that the position where the through-hole was formed was 7 mm away from the stepped portion, and the semiconductor element was bonded. During the stage heating at the time of bonding, the gap 107 progressed to the through hole, and then instantaneously progressed to the region where the semiconductor element was bonded. Moreover, in the observation after joining, joining deviation | shift was confirmed by many joining pads by peeling of the above-mentioned polyimide film.

Manufacturing process schematic diagram of the double-sided circuit board of the present invention Schematic front view of laminating equipment Schematic front view of peeling device Circuit pattern schematic of Example 1

Explanation of symbols

101, 209, 301 Glass 122, 208, 302 UV curable organic layer 103, 203, 303 Flexible film (plastic film)
104, 124 Circuit patterns 105, 403, 405 Connection holes 151, 153 Protective films 152, 154 Barrier metal layer 107 Gaps 108 Through-hole 109 Semiconductor element 201 Electrostatic charging device 202 Flexible planar body 204 Frame body 207 Mounting table 210 Squeegee 212 Rail 217 Ball screw 304 Curved surface 305, 309 Stage 306 Movable body 307 Holding body 308 Rail 401, 411 Inner leads 402, 404, 406 Wiring 407, 412 Outer lead 408 Solder resist end 413 Semiconductor junction region end

Claims (5)

A circuit board in which a through hole is formed between a first surface and a second surface within 5 mm from a step portion of a first surface of a flexible film having a circuit pattern on both surfaces. A circuit board having a step on at least one side of a flexible film having a circuit pattern on both sides, the first surface having the step being fixed to a reinforcing plate through a peelable organic layer, and reinforced by the step A circuit board member in which a through hole is formed between a first surface and a second surface within 5 mm from a step portion generated between a board and a circuit board. The circuit board member according to claim 2, wherein at least a part of the through hole is formed to be stepped. A step of fixing a first surface having a step of a circuit board having a step on at least one side of a flexible film having a circuit pattern on both sides to a reinforcing plate via a peelable organic layer, and the fixed surface A method for manufacturing a circuit board member, comprising: forming a circuit pattern on the second surface of the opposite surface; and forming a through-hole in the flexible film from the second surface within 5 mm from the step. The manufacturing method of the member for circuit boards of Claim 4 currently formed so that at least one part of a through-hole may cover a level | step difference.

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