JP3726951B2 - Screen printing method for film carrier - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a screen printing method for forming a solder resist layer on a film carrier (TAB (Tape Automated Bonding) tape) for mounting an electronic component such as an IC chip on a conductor made of a metal foil.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, electronic devices such as notebook computers, printers, and mobile phones have been reduced in size and weight by mounting electronic components such as ICs and LSI chips on film carriers. In addition, with the downsizing of electronic devices, the applications of film carriers that can be folded and used are becoming increasingly widespread. For example, in a film carrier for driving a liquid crystal element, one end of a lead is bonded to the liquid crystal element, and the film carrier is bent and bonded to an external wiring board. In this way, the film carrier used by being bent is provided with a flex portion having a slit in advance in the portion to be bent. The flex portion is a portion where the insulating film is punched out to form a flex slit when forming into a desired shape, and is a portion where the insulating film is partially absent. Therefore, by forming a solder resist layer, the wiring pattern is protected and the flex portion is reinforced in strength.
[0003]
The solder resist layer is formed by a screen printing method as follows. In the film carrier, an adhesive layer is provided on an insulating film, a metal foil is adhered thereon, and then a desired wiring pattern is formed by etching. Thereafter, a screen plate on which an emulsion is coated in advance on the insulating film on which the wiring pattern is formed is brought into contact with a portion other than the portion that becomes the solder resist layer, and a coating solution for the solder resist is uniformly applied on the screen plate. And then cured to form a solder resist layer.
[0004]
However, in such a screen printing method, the pressure of the printing spatula (squeegee) is difficult to be applied uniformly in the flex portion or the device hole portion where there is no insulating film, and the coating liquid remains uncoated. There is a problem that a filling portion occurs. On the contrary, there is a problem that in the part where the coating is partially thick, the bubbles in the coating solution are not easily removed and pinholes or voids are generated.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, the problems is the film carrier having a flex portion, provide a screen printing method of the film carrier which does not cause such unpainted and pinhole flex portion It is to be. Furthermore, it is providing the screen printing method of the film carrier which can obtain a uniform soldering resist layer because the pressure of the squeegee at the time of application | coating moves smoothly.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 includes an insulating film provided with a flex portion for bending,
A film carrier having a wiring pattern with a metal foil formed on this insulating film,
In the screen printing method of a film carrier that supports a printing stage having a convex portion corresponding to the flex portion of the insulating film and forms a solder resist layer on the wiring pattern with the metal foil ,
When there is a hill-like raised portion around the flex portion of the insulating film, the insulating film is formed using a printing stage provided with a depression corresponding to the hill-like raised portion around the convex portion. A screen printing method of a film carrier that supports
The invention according to claim 2 is the film carrier screen printing method according to claim 1, wherein the hill-shaped raised portion is caused by a coating liquid at the time of forming a protective film for protecting the flex portion. A screen printing method for a film carrier.
According to a third aspect of the present invention, in the screen printing method for a film carrier according to the first or second aspect, the size of the convex portion of the printing stage corresponding to the flex portion corresponds to the plan view of the film carrier. The screen printing method of the film carrier is smaller in the range of 100 to 200 μm in both vertical and horizontal directions than the flex part.
According to a fourth aspect of the invention, the screen printing method of the film carrier according to any one of claims 1 to 3, the width of the flex portion, shall be the screen printing method of the film carrier is 500μm or more.
The invention described in 請 Motomeko 5, the screen printing method of the film carrier according to any one of claims 1 to 4, the thickness of the insulating film, a screen printing method of the film carrier is 40μm or more.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a plan view schematically showing the configuration of a film carrier. FIG. 2 is a cross-sectional view taken along line AA ′ of the film carrier shown in FIG. Film carrier 1 having a bending flex portion 8, as shown in FIGS. 1 and 2, the insulating film 2 on the adhesive layer 3, the wiring of a metal foil pattern 5 'were laminated in the order of the solder resist layer 4 It is configured Te.
[0008]
The insulating film 2 is required to have various characteristics in order to be subjected to chemical and mechanical processing in the manufacturing process of the film carrier 1. For example, heat resistance that does not change even when exposed to a high temperature by bonding, and chemical resistance that does not change even when contacted with an acid by etching, a solvent by washing, or the like are required. Furthermore, since it is often used by being bent, it must be excellent in flexibility. For this reason, examples of the material for the insulating film 2 include glass epoxy, BT resin, polyester, polyimide resin, and modified products thereof. In particular, a polyimide resin is preferable. Polyimide resin exhibits high heat resistance and electrical insulation, and is excellent in flexibility. This polyimide resin is a polymer having an acid imide structure, and examples thereof include a condensation polymer of pyromellitic dianhydride and aromatic diamine, a condensation polymer of biphenyltetracarboxylic dianhydride and aromatic diamine, and the like. The thickness of the insulating film 2 is preferably 40 μm or more. This is to compensate for the strength of the film carrier 1 having the flex portion 8.
[0009]
The adhesive used for the adhesive layer 3 requires adhesiveness in addition to heat resistance, chemical resistance, and flexibility. Examples of the adhesive include epoxy, phenol adhesive, and modified products thereof. In particular, an epoxy adhesive is preferable. Epoxy adhesives are excellent in adhesion to metals, and are excellent in electrical insulation and heat resistance. These curing agents are added to the epoxy adhesive, applied to the surface of the insulating film 2 or the metal foil 5, and the insulating film 2 and the metal foil 5 are adhered by leaving or heating at room temperature. As the curing agent, it can be appropriately selected from amines, polyamides, polysulfides, organic acid anhydrides and the like. The thickness of the adhesive layer is 3 to 23 μm, preferably 10 to 21 μm.
[0010]
As the metal foil 5, a copper foil 5 having excellent conductivity and corrosion resistance is used. Examples of the copper foil 5 include electrolytic copper foil and rolled copper foil. In particular, an electrolytic copper foil is preferable because it has a rough surface and is easily compatible with an adhesive. The thickness of the copper foil 5 is in the range of 6 to 75 μm, preferably 9 to 75 μm, and more preferably 9 to 35 μm. Thus, the thin copper foil 5 is easy to cope with the miniaturization of the outer lead 10.
[0011]
A wiring pattern 5 ′ is formed by a method such as etching, and a urethane resist is applied on the wiring pattern 5 ′ to provide a solder resist layer 4 to protect the surface.
The urethane resin is a resin having a urethane bond generated by a reaction between a diisocyanate and a glycol component. As the urethane resin, a thermosetting resin is preferable, an elastomer may be mixed with the urethane resin, or an elastomer component may be copolymerized with the urethane resin. The urethane resin may not be added with a silicone antifoaming agent. In addition, the solder resist layer 4 such as urethane resin has an accelerator that accelerates curing of the resin, a filler that improves chemical resistance, an additive that imparts flexibility, a thixotropic agent that adjusts the viscosity of the coating solution, and the like. Can be added as appropriate. Furthermore, in order to improve mechanical properties such as flexibility of the solder resist layer 4, fine particles such as rubber fine particles may be added.
[0012]
Further, a solder resist layer 4 made of polyimide resin is provided in a portion in contact with the output outer lead 10a. The polyimide resin has lower wettability than epoxy resin, urethane resin, and the like, and the flux is less likely to adhere to it. Therefore, the polyimide resin is used in a portion in contact with the output outer lead 10a. Furthermore, by setting the application thickness of the polyimide resin to 25 μm or less, the bonding failure during soldering is prevented and the reliability is improved.
[0013]
Moreover, you may provide the protective resin layer 13 in a flex part. As the protective resin layer 13 of the flex part, it is preferable to use a resin having high heat resistance and chemical resistance and being excellent in flexibility because it is often bent or bent. As this resin, polyimide resin, acrylic resin, urethane resin and the like are preferable. As a method for forming the protective resin layer 13, a screen printing method, a roll coater method, a tampo printing method, or the like can be appropriately selected. The thickness of the protective resin layer is preferably thinner than the insulating film, and is in the range of 5 to 95 μm, preferably 20 to 40 μm.
[0014]
Here, the method for producing the film carrier of the present invention will be described. An adhesive layer 3 is provided on an insulating film 2 having high heat resistance such as polyimide resin, and a conductive metal foil (copper foil) 5 is bonded thereto. Next, a photoresist is applied on the copper foil 5 and exposed through a mask so as to form a desired wiring pattern 5 ′, and then etched to form a wiring pattern 5 ′. Next, the photoresist is removed, leaving the inner leads 9 for bonding the electronic components, and a solder resist coating solution 23 is applied onto the surface of the insulating film 2 from above the wiring pattern 5 'to form the solder resist layer 4 Form. Thereafter, the film carrier 1 is obtained by plating the copper foil 5 not covered with the solder resist layer 4 with tin or the like. At this time, the solder resist layer 4 is formed by a solder resist coating solution 23 prepared by dissolving a thermosetting resin in an organic solvent.
[0015]
Next, a screen printing method for forming the solder resist layer 4 will be described.
FIG. 3 is a schematic view showing an embodiment of the screen printing method of the film carrier of the present invention. FIG. 4A is a schematic diagram showing the structure of a printing stage used in the screen printing method for a film carrier of the present invention. FIG. 4B is an enlarged view of the flex portion.
The screen printing method of the film carrier 1 is performed as follows. A screen 21 masked by applying a photocurable emulsion 22 to a screen 21 stretched on a frame (not shown), exposing and curing a desired pattern, and removing other uncured portions. A screen 21 for printing is produced. In the screen printing machine, a gear is put into a sprocket hole 7 provided with a uniform width on the insulating film 2 and conveyed, and a plurality of pins (not shown) that move up and down are provided around the printing stage 24. When the conductive film 2 is conveyed, the pin is raised and inserted into a small hole (not shown) on the insulating film 2. Next, the insulating film 2 is pressed by a pressing plate, positioned and fixed on the printing stage by suction , and the screen 21 is disposed on the fixed insulating film 2. A solder resist coating solution 23 prepared with urethane resin or the like is poured onto the screen 21, the squeegee 20 is moved at a constant pressure and speed, and the solder resist is applied onto the film carrier 1 through the screen 21 from a portion without a mask. The coating liquid 23 is applied.
[0016]
Next, a conventional screen printing method will be described. FIG. 5 is a schematic view showing an example of a conventional screen printing method for a film carrier. As shown in FIG. 5, the conventional printing stage 24 is not provided with the convex portion 24 a corresponding to the flex portion 8. Therefore, in the conventional screen printing method, even if the protective resin layer 13 is provided on the back side of the flex portion 8, since the insulating film 2 is not provided, the pressure of the wiring pattern 5 ′ is caused by the pressure when the squeegee 20 passes. The output outer lead 10a may be bent or disconnected as indicated by a symbol D in FIG. Further, the pressure of the squeegee 20 swings the protective resin layer 13 and the like, and the space between the screen 21, the output outer lead 10 a and the protective resin layer 13 is widened or narrowed . Therefore, passing a certain amount of the solder resist coating solution 23 on the screen 21 at a pressure of the squeegee 20, the thick solder resist layer 4 coating solution gathered in flexed portion is formed, the coating liquid of the other portion for its Decreases, the solder resist layer 4 becomes thin, and unpainted portions occur. In this way, the solder resist layer 4 becomes non-uniform, and random coating spots are formed between the thick and thin portions. Furthermore, pinholes and the like are likely to occur in the portion where the thick solder resist layer 4 is formed, and the remaining portions become thin solder resist layers 4 and unpainted portions occur.
[0017]
Therefore, in the present invention, as shown in FIGS. 3 and 4, the screen 21 is bent or deformed by the pressure of the squeegee 20 by providing the printing stage 24 having the convex portion 24 a corresponding to the flex portion 8. The occurrence of smears can be suppressed. Therefore, the film carrier 1 without pinholes and unpainted parts can be manufactured.
The printing stage 24 having the convex portion 24a corresponding to the flex portion 8 is, for example, a method in which a tape to which an adhesive is adhered is bonded to a predetermined height , or the printing stage is machined by a milling machine or the like It can manufacture by selecting suitably methods, such as processing by etching, such as processing or chemical polishing.
[0018]
Further, a step (hereinafter referred to as a dent) may be provided around the convex portion of the printing stage of the present invention. FIG. 6 is a diagram illustrating a screen printing example of a solder resist layer in the case where a hill-shaped raised portion is formed around the flex portion when the protective resin layer is formed.
In the film carrier 1 in which the protective resin layer 13 is provided on the flex portion 8, a hill-shaped raised portion 14 is formed around the flex portion 8. That is, when the protective resin layer 13 is formed by a screen printing method, a masked screen is prepared by coating the portion other than the portion corresponding to the flex portion 8 with an emulsion. If the unmasked portion of the screen is greater than the flex section 8, part of the insulating film is exposed, hill-shaped raised portions 14 screen coating liquid to the exposed portion thereof is coated is formed. Conversely, if the unmasked portion of the screen is smaller than the slit portion in order to have inter gap between SCREEN and the insulating film 2, the protective resin layer forming coating liquid in the gap portion is penetrated, A hill-shaped raised portion 14 is formed around the flex portion 8.
As shown in FIG. 6, by providing the recess 24c in the printing stage 24, by pulling in 24c depressions hill-shaped raised portion 14, the convex portion 24a of the printing stage 24 supports the direct protective resin layer 13 Further, since the wiring pattern 5 ′ and the screen 21 are not bent or deformed by the pressure of the squeegee 20, the squeegee 20 can be moved smoothly. Due to this smooth movement, the solder resist layer 4 can be applied to a certain thickness, and the film carrier 1 can be manufactured with no occurrence of pinholes and unpainted spots while suppressing the occurrence of smears.
[0019]
The size of the convex portion 24a corresponding to the flex portion 8 of the printing stage 24 is larger than the corresponding flex portion 8 on the plan view (FIG. 1) of the film carrier 1, as shown in the sectional view of FIG. The length and width are preferably 100 to 200 μm smaller. When the vertical or horizontal dimension of the convex portion 24a corresponding to the flex portion 8 is 200 μm or more smaller than that of the flex portion, the protective resin layer 13 or the like is bent, and pinholes and unpainted portions are generated. On the other hand, if the vertical or horizontal dimension of the convex portion 24a corresponding to the flex portion 8 is 100 μm or less smaller than the flex portion 8, accuracy for sucking and fixing the film carrier on the printing stage 24 is required, and productivity is reduced. Because. The height of the convex portion 24a corresponding to the flex portion 8 of the printing stage 24 is preferably at least 30 μm. If the height of the convex portion 24a corresponding to the flex portion 8 is less than 30 μm, the insulating film 2 and the protective resin layer 13 are bent, and pinholes and unpainted portions are generated.
In addition, the recess 24c provided around the convex portion 24a of the printing stage 24 preferably has a width of at least 200 μm and a depth of at least 5 μm. The hill-like raised portion 14 around the flex portion 8 is formed in a range of a width of 200 to 1000 μm and a height of 5 to 50 μm, depending on screen printing conditions. Therefore, it is necessary to have a size for completely storing them.
[0020]
Moreover, it is preferable that the width of the flex part 8 is at least 500 μm or more with respect to the moving direction of the squeegee 20 or the direction perpendicular to the moving direction. If it is less than 500 [mu] m, in order to both ends of the flex portion 8 is supported on the insulating film 2, less deflection or deformation, the effect is small to provide a printing stage 24 with a protrusion 24a corresponding to the flex portion 8 Because.
[0021]
Moreover, it is preferable that the thickness of the insulating film 2 is 40 μm or more because the thickness is less than 40 μm and the strength is low, and the insulating film 2 is bent or bent by the pressure of the squeegee 20. The solder resist layer 4 other than the flex portion 8 cannot be formed uniformly. In particular, since the end portion of the flex portion 8 is bent, it is difficult to form a uniform solder resist layer 4 in the flex portion 8.
Moreover, it is preferable that the film carrier 1 of this invention provides the soldering resist layer 4 on both surfaces. By providing the solder resist layer 4 on both sides, the flex portion 8 and the like can be further reinforced.
[0022]
Further, the printing stage 24 preferably has a convex portion 24 b corresponding to the device hole 6 of the film carrier 1. The device hole 6 is a portion provided on the film carrier 1 for mounting electronic components such as an IC chip and an LSI chip, and is a portion without an insulating resin formed by punching or the like. Inner leads 9 are formed in the device holes 6 to be joined to the electrodes of the electronic components. The inner lead 9 protrudes into the device hole 6. When the solder resist layer 4 is formed, the screen 21 is masked with the emulsion 22 so that it is not blocked by the solder resist coating solution 23. However, since the pressure of the squeegee 20 is applied, the inner lead 9 is deformed downward. This deformation may be caught by conveyance during another manufacturing process, and may not be aligned with the electrode of the electronic component and may not be joined. Protruding portions 24b corresponding to the device holes 6 are provided on the printing stage 24, thereby preventing deformation of the inner leads 9 and the like.
[0023]
Furthermore, the printing stage 24 in which the convex portion 24a corresponding to the flex portion 8 is lower than the convex portion 24b corresponding to the device hole 6 is preferable. The flex portion 8 is provided with a protective resin layer 13 for reinforcement. The device hole 6 is later mounted with electronic components, and then a sealing resin layer (not shown) is provided. Therefore, when applying the solder resist coating solution 23, it is preferable to make the convex portion 24 b corresponding to the device hole 6 high because there is nothing to reinforce the device hole 6. Moreover, it is preferable that the convex part 24a corresponding to the flex part 8 is 55-65 micrometers lower than the convex part 24b corresponding to the device hole 6. FIG. This is because the thickness of the protective resin layer 13 is preferably 40 to 70 μm.
[0024]
【Example】
(Example 1)
Examples of the present invention will be described below.
A device hole 6, a sprocket hole 7, and a flex part 8 are formed by punching a laminate of epoxy resin as a 12 μm thick adhesive layer 3 on an insulating film 2 made of polyimide resin having a thickness of 40 μm. Next, an electrolytic copper foil 5 having a thickness of 18 μm is bonded to the adhesive layer 3. A photoresist is applied on the electrolytic copper foil 5, exposed and etched to form a wiring pattern 5 ′. The insulating film 2 has two device holes 6 of 3000 × 16000 μm and flex portions 8 of 1500 × 29000 μm and 800 × 29000 μm.
Next, a 350-mesh screen 21 was stretched on the frame of the screen plate, and emulsion 22 was applied to the screen 21 to a thickness of 30 μm and cured to produce a screen. Next, with a screen printer, the screen 21 is placed on the film carrier 1 of the printing stage 24, the solder resist coating solution 23 is poured, the pressure of the squeegee 20 is 294 kPa (3 kg / cm ² ), and the moving speed is 150 mm / sec. Apply. The first layer is a coating solution using a urethane resin, and the second layer is a coating solution using a polyimide resin. Thereafter, it is cured by heat treatment.
[0025]
At this time, the printing stage 24 is 2800 × 15800 μm in height corresponding to the device hole 6 and 95 μm high in the convex portion 24 b, and the flex portion 8 is corresponding to 1100 × 28500 μm in height and 30 μm and 400 × 28600 μm in height. Are provided with two convex portions 24a of 30 μm. Even when any solder resist layer 4 was formed, the movement of the squeegee 20 was uniform, and the screen 21 did not sink and the insulating film 2 did not bend. Moreover, the film carrier 1 after the heat treatment was free from smears, and therefore no pinholes or unpainted parts were generated.
[0026]
(Comparative Example 1)
In Comparative Example 1, a film carrier 1 provided with a solder resist layer 4 was produced in the same manner as in Example 1 except that the printing stage 24 having no convex portions 24a was used.
Here, the insulating film 2 may bend by the pressure during the movement of the squeegee 20. Further, the flex portion 8 was greatly bent and had smears, and there were some where unpainted portions or pinholes were generated.
[0027]
(Example 2)
In Example 2, the film carrier 1 in which the solder resist layer 4 is provided in the same manner as in Example 1 except that the printing stage 24 provided with a recess 24c having a width of 300 μm and a depth of 15 μm is used around the convex portion 24a. Produced. At this time, the hill-shaped raised portion 14 of the protective resin layer 13 formed on the insulating film 2 by the coating solution of polyimide resin had an average width of 200 μm and an average height of 10 μm. Even when any solder resist layer 4 was formed, the movement of the squeegee 20 was uniform as compared with Example 1, and the screen 21 did not sink and the insulating film 2 did not bend. Moreover, the film carrier 1 after the heat treatment was free from smears, and therefore no pinholes or unpainted parts were generated.
[0028]
【The invention's effect】
As described above, in the screen printing method of the film carrier of the present invention, the insulating film does not bend or bend, and the squeegee also moves smoothly at the time of application, so that the flex portion of the flex portion and the device There was no smearing in the hall. Therefore, generation | occurrence | production of the pinhole etc. in the unfilled unpainted residue in a flex part etc. and the thick part can be suppressed.
[Brief description of the drawings]
FIG. 1 is a plan view schematically showing the configuration of a film carrier.
FIG. 2 is a cross-sectional view taken along line AA ′ of the film carrier shown in FIG.
FIG. 3 is a schematic view showing one embodiment of a screen printing method for a film carrier of the present invention.
FIG. 4 (a) is a schematic view showing the structure of a printing stage used in the screen printing method of a film carrier of the present invention. FIG. 4B is an enlarged view of the flex portion.
FIG. 5 is a schematic view showing an example of a conventional film carrier screen printing method.
FIG. 6 is a diagram illustrating a screen printing example of a solder resist layer in a case where a hill-shaped raised portion is formed around the flex portion when the protective resin layer is formed.
[Explanation of symbols]
1 Film carrier 2 Insulating film 3 Adhesive layer 4 Solder resist layer 5 Metal foil (copper foil)
5 'Wiring pattern 6 Device hole 7 Sprocket hole 8 Flex part (flex slit)
9 Inner lead 10 Outer lead 10a Output outer lead 10b Input outer lead 11 Protective resin layer 12 IC chip 13 Protective resin layer 14 Hill-like raised portion 20 Squeegee 21 Screen 22 Emulsion 23 Solder resist coating solution 24 Printing stage 24a On flex portion Corresponding convex part 24b Convex part 24c corresponding to the device hole Step (dent)

Claims (5)

An insulating film having a flex portion for bending;
A film carrier having a wiring pattern with a metal foil formed on this insulating film,
In the screen printing method of a film carrier that supports a printing stage having a convex portion corresponding to the flex portion of the insulating film and forms a solder resist layer on the wiring pattern with the metal foil ,
When there is a hill-like raised portion around the flex portion of the insulating film, the insulating film is formed using a printing stage provided with a depression corresponding to the hill-like raised portion around the convex portion. A screen printing method for a film carrier characterized by supporting the film. In the screen printing method of the film carrier of Claim 1,
The method for screen printing a film carrier, wherein the hill-shaped raised portion is caused by a coating liquid at the time of forming a protective film for protecting the flex portion. In the screen printing method of the film carrier of Claim 1 or 2,
The film carrier screen printing method characterized in that the size of the convex portion of the printing stage corresponding to the flex portion is smaller in the range of 100 to 200 μm both vertically and horizontally than the corresponding flex portion on the plan view of the film carrier. In the screen printing method of the film carrier in any one of Claims 1 thru | or 3,
The screen printing method for a film carrier, wherein the width of the flex part is 500 μm or more. In the screen printing method of the film carrier in any one of Claims 1 thru | or 4 ,
A film carrier screen printing method, wherein the thickness of the insulating film is 40 μm or more.

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