JP2004297102A - Manufacturing method of film carrier tape for electronic part packaging - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a film carrier tape for electronic parts packaging in which a scooped portion is unlikely to be formed in a wiring pattern of a solder resist lower part, and the swelling or peeling of a formed plated layer is unlikely to happen. <P>SOLUTION: The manufacturing method of film carrier tape for electronic parts packaging of the present invention is characterized in that a tin plated layer of 0.2-0.7 μm in an average thickness is formed at a lead portion of the wiring pattern formed on a flexible insulating film by copper or a copper alloy by performing tin plating at least one time by employing a electroless tin plating bath in which Sn<SP>2+</SP>density is adjusted in the range of 13-50 g/l by blending tin fluoroborate [Sn(BF<SB>4</SB>)<SB>2</SB>]. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a film carrier tape for mounting electronic parts (for example, TAB (Tape Automated).
The present invention relates to a method for manufacturing a bonding (bonding) tape, a T-BGA (Tape Ball Grid Array) tape, an ASIC (Application Specific Integrated Circuit) tape, and the like.

  With the development of the electronics industry, demand for printed wiring boards on which electronic components such as ICs (integrated circuits) and LSIs (large-scale integrated circuits) are mounted has been rapidly increasing. There has been a demand for higher functionality, and as a mounting method for these electronic components, a mounting method using a film carrier tape for mounting electronic components has recently been adopted. The importance of the liquid crystal display device (LCD) in the electronics industry, which requires a reduction in the frame area of the screen, is increasing.

  Conventionally, such a film carrier tape for mounting electronic components has been manufactured through the following steps, for example. That is, first, after a flexible insulating film serving as a base material such as a polyimide film is punched by a press machine, a conductor foil such as a copper foil is laminated on the flexible insulating film. Then, a photoresist is applied to the upper surface of the conductive foil, and the photoresist is exposed to ultraviolet light in a desired pattern shape using the photoresist, and the exposed photoresist portions are dissolved and removed by a developer. The conductor foil portion not covered with the photoresist is removed by chemically dissolving (etching) with an acid or the like, and then the photoresist is dissolved and removed with an alkali solution to remove the conductor remaining on the insulating film. A desired wiring pattern is formed from the foil.

  In addition, inner leads connected to devices (electronic components) such as ICs in a wiring pattern are provided to prevent short circuit due to adhesion of dust, whiskers and migration during mounting, and to protect and insulate between wirings. Except for the leads such as the outer leads and the output-side outer leads connected to the liquid crystal display element, etc., apply a solder resist, which is an insulating resin, using a screen printing method and then cure to form a solder resist layer I do.

Then, to prevent oxidation and discoloration of the exposed lead portion, and to ensure bonding strength (bondability) with the connection portion such as the bump electrode of the device connected to the lead portion, the lead portion is plated. I do. Various metals are used for this plating process.Because the bump electrodes of the device are made of gold, electroless tin plating is relatively easy to connect by forming a gold-tin eutectic. Widely used.

  Such electroless tin plating is performed by forming a solder resist layer and then immersing it in a tin plating bath to form a tin plated layer on the surface of the wiring pattern not covered by the solder resist layer. In a normal case, the solder resist layer becomes a masking material for tin plating, and the wiring pattern at the portion where the solder resist layer is applied should not come into contact with the plating solution.

  However, in reality, the solder resist layer has portions at its edges where the adhesion to the wiring pattern or the flexible insulating film is incomplete, and the plating solution can penetrate into the lower portion of the solder resist from these portions. is there. Then, in the portion where the plating solution has penetrated into the lower portion of the solder resist, a local battery is formed between the metal copper of the wiring pattern and the already deposited metal tin, and abnormal elution of the metal copper of the wiring pattern occurs. Such abnormal elution of the wiring pattern under the solder resist is usually called “egure”.

  Conventionally, since the thickness of the conductive foil forming the wiring pattern was as large as several tens of μm, even if such scuffing occurred, there was little occurrence of a serious problem such as a decrease in lead strength or disconnection. However, under the recent demand for fine pitch in which the width of the lead is 25 μm or less and the thickness of the conductor foil is 18 μm or less in order to form such a fine wire lead, the depth is more than The scorched portion, which may be as large as μm, not only greatly affects the strength of the lead, but also leads to disconnection of the lead due to the formation of such a scoured portion.

  An object of the present invention is to provide a method for manufacturing a film carrier tape for mounting electronic components, in which a curled portion is unlikely to be formed in a wiring pattern below a solder resist as described above. Further, the present invention provides a method for producing a film carrier tape for mounting electronic components, in which a curled portion is not easily formed in a wiring pattern below a solder resist as described above, and a blister or peeling of a formed plating layer is not easily generated. It is intended to be.

The method for producing a film carrier tape for mounting electronic components according to the present invention comprises the steps of blending tin borofluoride (Sn (BF ₄ ) ₂ ) with a lead portion of a wiring pattern formed of copper or a copper alloy on a flexible insulating film. Then, the present tin plating is performed at least once using an electroless tin plating bath in which the Sn ²⁺ concentration is adjusted within the range of 13 to 50 g / liter to form the present tin plating layer having an average thickness of 0.2 to 0.7 μm. It is characterized by doing.

In the method of the present invention, it is preferable that a surface to be tin-plated is soft-etched before the above-described tin plating is performed.
Further, in the method of the present invention, the step of forming the electroless tin plating layer can be performed by dividing into the press plating and the present tin plating, and in this case, the thickness of the press plating layer is smaller than the thickness of the present tin plating. Is preferred.

  In the present invention, the wiring pattern can be formed from a metal layer by a vapor deposition method or a plating method.

The film carrier tape for mounting electronic components production method of the present invention has been tinned by controlling the Sn ²⁺ concentration in a predetermined range in the plating bath to conduct electroless tin plating, the thus Sn ²⁺ concentration By controlling, generation of the screeching can be suppressed. Further, by forming the press plating layer before the formation of the tin plating layer, the depth can be suppressed to the minimum even if a scorched portion is formed.

Next, a method for manufacturing the film carrier tape for mounting electronic components of the present invention will be specifically described.
In the method for manufacturing a film carrier tape for mounting electronic components of the present invention, a conductive foil is laminated on a flexible insulating film, a photoresist is applied to the upper surface of the conductive foil, and the photoresist is formed into a desired shape. Exposure is performed so that a wiring pattern is formed, the excess photoresist is removed, and the conductive foil is etched using the remaining photoresist as a masking material to form a desired wiring pattern. Next, a solder resist, which is an insulating resin, is applied and hardened after leaving a lead portion for bonding a device or the like. After that, the wiring pattern portion where the solder resist is not applied (that is, mainly a lead portion) is manufactured by tin plating. Have been.

  The flexible insulating film used in the method of the present invention is a flexible insulating resin film. In addition, this flexible insulating film has chemical resistance not to be attacked by such a chemical because it comes into contact with an acid or the like at the time of etching, and heat resistance such that it does not deteriorate by heating when bonding a device. I have. Examples of such a flexible insulating film as a material include polyester, polyamide, and polyimide. Particularly, in the present invention, it is preferable to use a film made of polyimide.

  Examples of the polyimide film constituting the flexible insulating film include a wholly aromatic polyimide synthesized from pyromellitic dianhydride and an aromatic diamine, and a synthesis from biphenyltetracarboxylic dianhydride and an aromatic diamine. Wholly aromatic polyimide having a biphenyl skeleton. Particularly, in the present invention, a wholly aromatic polyimide having a biphenyl skeleton (eg, trade name: Upilex, manufactured by Ube Industries, Ltd.) is preferably used. The thickness of such a flexible insulating film is usually in the range of 25 to 125 μm, preferably 50 to 75 μm.

  When the flexible insulating film used in the present invention has a device hole, a sprocket hole, an outer lead hole, and a bent portion, a flex slit or the like is formed at the bent position by punching. The wiring pattern is formed by etching the metal foil laminated on at least one surface of the flexible insulating film having the predetermined holes as described above. The metal foil is laminated on at least one surface of the flexible insulating film with or without an adhesive. Here, when attaching a metal foil using an adhesive, an adhesive layer is formed using an insulating adhesive.

  When an adhesive is used, the adhesive used must have properties such as heat resistance, chemical resistance, adhesive strength, and flexibility. Examples of the adhesive having such properties include an epoxy-based adhesive, a polyimide-based adhesive, and a phenol-based adhesive. Such an adhesive may be modified with a urethane resin, a melamine resin, a polyvinyl acetal resin, or the like, or the epoxy resin itself may be modified with a rubber. Such adhesives are usually heat-curable. The thickness of the adhesive layer is usually in the range of 8 to 23 μm, preferably 10 to 21 μm.

  In the method for manufacturing a film carrier tape for mounting electronic components of the present invention, when laminating a metal foil on the above-mentioned flexible insulating film, the metal foil can be laminated without using an adhesive. Further, apart from the method using a metal foil as described above, a metal layer can be formed by, for example, a vapor deposition method or a plating method, and in such a case, a metal thin layer is formed using a thin metal foil. And a metal may be deposited on the thin metal layer by the vapor deposition method or the plating method to form a metal layer having a predetermined thickness.

  When an adhesive is used, the adhesive layer may be provided by applying an adhesive to the surface of the flexible insulating film, or may be provided by applying an adhesive to the surface of the metal foil. The metal foil used in the present invention has conductivity, and examples of such a metal foil include a copper foil and an aluminum foil. Particularly, in the present invention, it is preferable to use a copper foil as the metal foil. The copper foil used as the metal foil in the present invention includes an electrolytic copper foil and a rolled copper foil, and any of the copper foils can be used in the present invention. In producing the tape, it is preferable to use an electrolytic copper foil as the metal foil.

As the electrolytic copper foil used here, an electrolytic copper foil having a thickness generally used in the production of a film carrier tape for mounting electronic components can be used. For production, the average thickness is usually in the range of 3 to 150 μm, preferably 6 to 70 μm, particularly preferably 8 to 35 μm, more preferably 8 to 1 μm.
Use an electrolytic copper foil in the range of 8 μm. By using the electrolytic copper foil having such an average thickness, the inner leads having a narrow pitch can be easily formed. The surface of such an electrolytic copper foil may be surface-regulated by mechanical polishing, chemical polishing, electrolytic polishing, or a combination thereof.

  By laminating the above-mentioned flexible insulating film and a metal foil, a layer made of a metal (a metal foil layer, and a layer made of a thin metal foil) is formed on at least one surface of the flexible insulating film. A base film is formed on which a metal plating layer or a metal vapor-deposited layer having a predetermined thickness by plating or metal vapor-deposition on the layer, or a composite metal layer thereof may be formed.

  Then, a photoresist is applied to the surface of the metal layer of the base film, a predetermined wiring pattern is baked on the photoresist, and unnecessary portions of the photoresist are removed to form a predetermined pattern on the surface of the metal layer of the base film. The metal layer is etched using this pattern as a masking material. That is, a phytoresist is applied to the surface of the metal layer of the base film, and a predetermined wiring pattern is exposed and baked to form a soluble portion and an insoluble portion in the aqueous medium. The masking material made of an insoluble photoresist can be formed on the surface of the metal layer. Here, the masking material made of an insoluble photoresist may be formed of a photoresist that is cured by exposure, or conversely, it can be dissolved in a specific solvent such as an aqueous medium by exposure. After exposure using a photoresist, the photoresist can be formed by removing a portion of the photoresist solubilized by a specific solvent.

  By contacting the base film masked by the photoresist with the etching solution, the metal of the unmasked portion elutes, and the metal of the masked portion remains on the flexible insulating film, and A wiring pattern composed of a metal foil (or a metal layer) not eluted is formed on the conductive insulating film. As the etchant used here, a commonly used acidic etchant can be used.

In the wiring pattern thus formed, each pitch width of the inner leads is usually 20 to 500 μm, preferably 25 to 100 μm, and the present invention is particularly applied to a film carrier tape for mounting electronic components with a fine pitch of 30 to 80 μm. Highly useful. In the present invention, usually, after a predetermined wiring pattern is formed in this way, a solder resist layer is formed except for the tips of inner leads and outer leads to be plated in the next step.

  In the present invention, such a solder resist layer is formed by applying a solder resist coating solution to a predetermined position using a screen printing technique. In the method of the present invention, the average coating thickness of the solder resist is usually in the range of 1 to 80 μm, preferably 5 to 50 μm in terms of the thickness after curing. The curable resin contained in such a solder resist coating liquid is an epoxy resin, an elastomer-modified epoxy resin, a urethane resin, an elastomer-modified urethane resin, a polyimide resin, an elastomer-modified polyimide resin, and an acrylic resin. The resin preferably contains at least one resin component selected from the group consisting of resins. In particular, it is preferable to use a modified elastomer.

Further, in the present invention, in addition to the resin components as described above, the solder resist coating liquid may contain substances usually added to the solder resist coating liquid, such as a curing accelerator, a filler, an additive, a thixotropic agent, and a solvent. Can be added. Further, in order to improve characteristics such as flexibility of the solder resist layer, fine particles having elasticity such as rubber fine particles can be blended.

When the solder resist is applied and cured in this manner, the solder resist coating solution may flow outward from the application position at the edge of the applied solder resist, and the edge of the applied solder resist layer may have a wiring pattern. Adhesion may not be good. Then, as shown in FIG. 1, the plating solution may penetrate into the lower portion of the solder resist from the edge of the solder resist. A local battery is formed between the already deposited metal tins, and abnormal elution of the metal copper of the wiring pattern occurs, so-called "gouge portions" are formed. If the depth of such an undercut generally exceeds 5.5 μm, the presence of the undercut in a recent fine-pitch electronic component mounting film carrier tape is manifested as a decrease in lead strength. May not endure normal use.

Then, the present inventor studied a method for suppressing the formation of such a scuffed portion, and found that the depth of the scoured portion remarkably differs depending on the concentration of Sn ^{2+ in} the plating solution. In the present invention, the tin plating includes press plating and main tin plating. In the present invention, any method of directly performing main tin plating without performing press plating can be employed.

When tin plating is performed in the present invention, tin borofluoride [Sn (BF ₄ ) ₂ ] is blended so that the Sn ²⁺ concentration in the plating bath is 13 g / liter to 50 g / liter, preferably 15 to 30 g / liter. Is tinned using an electroless tin plating bath in the range of In the method for producing a film carrier tape for mounting electronic components of the present invention, the tin plating layer can be formed by various methods.

For example, as a tin plating bath that can be used in the present invention, a plating bath containing the components described below can be used.
(1)
Thiourea (NH ₂ ) ₂ CS
Tin borofluoride Sn (BF ₄ ) ₂
Hypophosphorous acid H ₃ PO ₄
Cationic surfactant In such a tin plating bath, the Sn ²⁺ concentration prepared by blending tin borofluoride [Sn (BF ₄ ) ₂ ] is preferably in the range of 13 to 50 g / liter. Needs to be adjusted within the range of 15 to 30 g / liter. By performing the electroless tin plating by adjusting the Sn ²⁺ concentration in the tin plating bath used in the present invention within the above range, even if a scoured portion is formed, the scoured portion affects the lead strength and the like. It is not so deep as to affect, and it does not cause disconnection of the lead portion or the like.

In the method of the present invention, the tin plating layer may be a single layer or may be formed from a plurality of layers.
That is, before performing the tin plating as described above, the lead portion or the wiring pattern may be press-plated, and then the tin plating may be performed using a tin plating bath having a Sn ²⁺ concentration within the above range. That is, as shown in FIG. 3, after the lead portion is press-plated at, for example, room temperature (25 ° C.), the tin plating can be performed on the press-plated layer at 70 ° C., for example. May be formed in two or more layers. In such a case, it is preferable that the thickness of the press plating layer is smaller than the thickness of the present tin plating layer. After performing the press plating in this way, by performing the present tin plating, a thin press plating layer is formed on the surface of the wiring pattern under the solder resist, for example, even if there is a peeled portion at the edge of the solder resist. Therefore, even if the plating solution remains in the peeled portion during the tin plating, the conductor foil (electrolytic copper foil) forming the wiring pattern does not elute, and thus the generation of the scoured portion can be suppressed. When the two tin plating layers are formed in this manner, the ratio of the thickness of the press plating layer to the thickness of the tin plating layer is usually 0.5: 10 to 2:10, preferably 0.5: 10 to 10:10. 1: 8, particularly preferably in the range of 0.5: 10 to 1:10. By reducing the thickness of the press plating layer in this manner, the effect of suppressing the generation of the scuffed portion is improved.

FIG. 2 shows an example of the relationship between the depth of the undercut portion when the Sn ²⁺ concentration in the plating bath used for the press plating is changed when performing the press plating and the present tin plating in combination. In FIG. 2, “A” indicates that after applying and curing a solder resist coating solution, the Sn ²⁺ concentration in the tin plating bath was changed to form a press plating layer at room temperature (25 ° C.), and then the tin plating conditions were changed to It is a graph which shows the relationship between the Sn ²⁺ concentration and the depth of the scoured portion generated when the present tin plating was performed by setting Sn ²⁺ concentration: 20 g / liter, temperature: 70 ° C., time: 210 sec. After forming a solder resist layer in the same manner as described above, performing soft press etching on the portion to be plated, and then performing the same press plating with changing the Sn ²⁺ concentration in the same manner, and then performing the same as above. It is a graph which shows the relationship of Sn2 ⁺ density ^| concentration and the depth of the scorched part which generate | occur | produced at the time of this tin plating.

As is apparent from FIG. 2, when the Sn ²⁺ concentration in the press plating solution is 7 g / liter or less, a very deep scoured portion is formed. Then, as the Sn ²⁺ concentration increases, the depth of the scouring portion gradually decreases, and the scuffing portion generated by using a press plating solution having a Sn ²⁺ concentration of 13 g / liter or more, preferably 15 g / liter or more. 5.5 in depth
It is almost stable below μm.

In addition, as shown in FIG. 5, the amount of scouring is reduced depending on the press plating time. FIG. 5 shows that the press plating conditions were changed to Sn ²⁺ concentration in the press plating bath: 15 g / liter, temperature: normal temperature (25 ° C.), press press plating time within the range of 10 to 210 seconds, and the tin plating conditions were changed to Sn. It is the graph which measured the depth of the scouring part which arises when performing tin plating at ²⁺ density ^| concentration: 15 g / liter, temperature: normal temperature (25 degreeC), time: 210 second. The lead to be plated is not soft-etched.

As is clear from FIG. 5, if the press plating is not performed, a scoured portion having a depth exceeding 7.25 μm is formed. However, as the press plating time is increased to 10 seconds and 30 seconds, the depth of the scoured portion gradually increases. When the pre-plating time is 30 seconds, the depth becomes 6.5 μm, which is about 0.75 μm lower than when no pre-plating is performed.

  It is estimated that there is a critical point of the press plating time with respect to the scouring depth in the vicinity of the press plating time of about 40 to 50 seconds. It is almost constant between μ5.5 μm. Therefore, in the method of the present invention, the pre-plating time is usually set to 20 seconds or more, preferably 40 seconds or more, particularly preferably 50 seconds or more, and more preferably 55 seconds or more. Since the press plating does not significantly affect the scouring depth even if the press plating is performed for a long time, the upper limit of the press plating time is usually about 210 seconds.

Although the above shows that the depth of the undercut portion can be reduced by performing the press plating and the tin plating, the tin borofluoride (Sn (BF ₄ ) ₂ is used when only the tin plating is performed without performing the press plating. ] Can be reduced by changing the Sn ²⁺ concentration. For example, this tin plating is performed on a lead portion which is not soft-etched and subjected to press plating, at a plating temperature of 70 ° C. and a plating time of 210 seconds, while changing the Sn ²⁺ concentration to 15 g / L, 20 g / L, and 27 g / L. Was performed and the depth of the generated scoured portion was measured. The results are shown in Table 1 below.

As described above, the Sn ²⁺ concentration containing tin borofluoride [Sn (BF ₄ ) ₂ ] in the present tin plating is in the range of 13 to 50 g / liter, preferably in the range of 15 to 30 g / liter. By doing so, the depth of the undercut portion is reduced. In order to reduce the depth of the undercut, it is effective to soft-etch the surface to be plated before plating.

In particular, in FIG. 2, by performing press plating and then performing tin plating after soft etching indicated by “B”, the depth of the scoured portion becomes 3.5 μm or less, and the depth of the scoured portion becomes 3.5 μm or less. In this case, it is difficult for the lead strength to be reduced or the lead to be deformed due to the generation of the scoring portion, and the lead is not disconnected due to the generation of the scoring portion. That is, as indicated by "B" in FIG. 2, in the method for manufacturing a film carrier tape for mounting electronic components of the present invention, it is preferable to soft-etch a portion to be plated before tin plating.

This soft etching is different from the etching for forming a wiring pattern, in which the surface of the formed wiring pattern is adjusted to make the plating more uniform in the next step (a surface to be plated (made of copper foil or the like). This is a step of chemically polishing a lead portion, etc., in which the surface of the wiring pattern is etched at a rate of about 1/3 to 1/20 of an etching rate for forming the wiring pattern.

  That is, this soft etching is a process of chemically polishing the surface to be plated with acid or the like very slightly using acid or the like. This soft etching cleans the surface of the surface to be plated and the metal oxide film on the surface to be plated. As a result, organic substances and the like are removed, and a uniform tin plating layer is easily formed on the soft-treated surface. Further, by performing this soft etching process, a uniform tin plating layer is formed, so that even if a scorched portion is formed, the depth thereof is reduced.

Such a soft etching solution is essentially an acidic solution capable of chemically polishing the surface of a wiring pattern. Examples of such a soft etching solution include those described below.
(1)
Sulfuric acid: 2 parts by volume Nitric acid: 1 part by volume hydrochloric acid: 0.8 ... milliliter / liter
(2)
Sulfuric acid: 7 to 150 ml / liter Hydrogen peroxide: 50 to 150 ml / liter Stabilizer: about 50 ml / liter
(3)
Chromic acid: about 270 g / liter
(Four)
Phosphoric acid: about 55% Nitric acid: about 29% Acetic acid: about 25%
(Five)
Sulfuric acid: 50-100 ml / liter Hydrochloric acid: 100-200 ml / liter Borofluoric acid: 50-100 ml / liter
(7)
Ammonium sulphate: 120 g / l
(8)
A soft etching solution which is an acidic aqueous solution containing K ₂ S ₂ O ₈ and H ₂ SO ₄ as main components and further containing metal ions such as copper.
(9)
Soft etching solution that is an acidic aqueous solution containing persulfate, hydrogen peroxide, and sulfuric acid
(Ten)
A soft etching solution that is an acidic aqueous solution containing nitric acid and sulfuric acid.

  In the present invention, in addition to the soft etching liquid as described above, other than the soft etching liquid exemplified above as long as it is an acidic liquid that can slightly etch a wiring pattern formed from a conductive foil on a film carrier tape for mounting electronic components. Things can be used. Particularly, in the present invention, it is preferable to use a soft etching solution containing ammonium persulfate.

  The above-described treatment with the soft etching solution is performed by bringing the surface to be soft-etched into contact with the soft etching solution at a temperature of usually 20 to 50 ° C. for 3 to 60 seconds. By subjecting the portion to be plated to soft etching using such a soft etching solution, an oxide film, an organic film, and the like on the surface of the surface to be plated are removed (usually by etching to a depth of 2 μm or less). ), And it is possible to form a very uniform tin plating layer. Further, as shown in FIG. 2, by performing tin plating after performing such a soft etching treatment, there is an effect that the depth of the scoured portion is reduced by about 2 μm when the same plating solution is used.

As described above, in the method for manufacturing a film carrier tape for mounting electronic components of the present invention, after forming a solder resist layer and then forming an electroless tin plating layer on a lead portion or the like, the Sn ²⁺ concentration in a tin plating bath is adjusted to a predetermined value. By setting it within the range, the formation of the scorched portion can be suppressed. Further, in the present invention, by forming a press-plated layer on the surface of the wiring pattern formed before applying the solder resist layer, it is possible to suppress the occurrence of the scoured portion, and to form the press-plated layer and the tin-plated layer. Thus, blistering or peeling of the plating layer can be prevented.

That is, as shown in FIG. 3, in the method for manufacturing a film carrier tape for mounting electronic components of the present invention, a tin plating layer can be formed after applying a solder resist as described above, and as shown in FIG. As described above, a thin press-plated layer may be formed before the solder resist is applied, and then the tin-plated layer may be formed by applying and curing the solder resist and then again performing tin plating. The thickness of the press plating layer formed before the formation of the solder resist layer is usually 0.005 to 0.3 μm, preferably 0.01 to 0.3 μm.
This press plating layer is formed thinner than the present tin plating layer which is plated after forming the solder resist layer. By forming a thin press-plated layer before applying a solder resist, forming a solder resist layer, and then forming a tin-plated layer in this way, it is possible to prevent the generation of a scoured portion.

  When a thin press-plated layer is formed before the formation of the solder resist layer as described above, the surface of the wiring pattern can be soft-etched in the same manner as described above. As described above, in the method for manufacturing a film carrier tape for mounting electronic components of the present invention, the thickness of the tin plating layer thus formed is usually 0.2 to 0.7 μm, preferably 0.3 to 0.7 μm. 0.5 μm. By providing a tin plating layer having such a thickness, a bump electrode or the like of a device can be satisfactorily bonded to the tin-plated lead and the like, and the corrosion resistance of the lead portion and the like can be improved. The thickness of the tin plating layer is the total thickness when a plurality of tin plating layers are formed.

After a tin plating layer is formed using a plating solution having a predetermined Sn ²⁺ concentration in this way, heat treatment is usually performed so that tin forming the formed tin plating layer and metal forming the wiring pattern mutually interact. Spread. Here, the heat treatment is performed by heating the tin plating layer to usually 90 to 150 ° C, preferably 110 to 140 ° C, usually for 30 to 180 minutes, preferably for 40 to 120 minutes.

By forming the electroless tin plating layer using a tin plating bath having a specific Sn ²⁺ concentration containing tin borofluoride [Sn (BF ₄ ) ₂ ], the depth of the undercut is reduced by the erosion effect of the plating solution. Become. The detailed reason why the depth of the undercut becomes shallow by using a tin plating bath in which the tin borofluoride [Sn (BF ₄ ) ₂ ] is blended and the Sn ²⁺ concentration is in a specific range is unknown, By forming a tin plating layer using a tin plating bath having a specific Sn ²⁺ concentration as described above, the immersion potential of the plating solution is maintained in a noble direction, and it is thought that this is because the formation of a local battery is obstructed. Can be

The film carrier tape for mounting electronic components manufactured by the method of the present invention in this manner can be used in the same manner as that manufactured by the usual method.
〔Example〕
Next, the method for producing a film carrier tape for mounting electronic components of the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.
[Reference Examples 1 to 6]
Device holes, sprocket holes, and cutting slits for outer leads were formed in a polyimide film having a width of 70 mm and a thickness of 50 μm by punching. Next, an epoxy-based adhesive was applied to the surface of the polyimide film, and an electrolytic copper foil having a thickness of 18 μm was attached.

  Further, a photoresist was applied on the electrolytic copper foil, and the photoresist was exposed to light and etched to form a wiring pattern on the copper foil. The pitch width of the leads in the formed wiring pattern is 50 μm. A urethane-based solder resist coating solution was applied while leaving the lead portion of the wiring pattern thus formed, and was cured by heating. The average thickness of the solder resist layer thus formed is 30 μm.

After forming the solder resist layer as described above, the lead surface was soft-etched using a soft etching solution having the following composition.
K ₂ S ₂ O ₈ ··· 100 g / liter H ₂ SO ₄ ··· 10 g / liter Copper ion concentration (in terms of copper sulfate) ··· 0.3 g / liter Water is added to the above components to make a total volume of 1 liter. And

The contact time between the soft etching solution and the lead surface was set to 10 seconds, and the temperature of the soft etching solution was set to 30 ° C. After washing with water, this tape was immersed in an electroless tin plating solution having the following composition at room temperature (25 ° C.) for 10 seconds to form a press plating layer on the lead portion.
Thiourea (NH ₂ ) ₂ CS ・ ・ ・ 15% by weight
Tin borofluoride Sn (BF ₄ ) ₂・ ・ ・ Predetermined amount hypophosphorous acid H ₃ PO ₄・ ・ ・ 6% by weight
Cationic surfactant 1% by weight or less Water was added to the above components to make the total amount 1 liter.

The tin borofluoride in the electroless tin plating bath has a Sn ²⁺ concentration in the tin plating bath of 2 g / liter (Reference Example 4), 3 g / liter (Reference Example 5), 8 g / liter (Reference Example 6), The amounts were 14 g / liter (Reference Example 1), 18 g / liter (Reference Example 2), and 27 g / liter (Reference Example 3).

The conditions of the press plating are as follows: temperature; 25 ° C. (room temperature); plating time 10 seconds. After pre-plating in this way, the present tin plating was performed. The conditions of the above electroless tin plating were as follows: plating bath temperature; 70 ° C., contact time: 210 seconds, Sn ²⁺ concentration: 20 g / liter, and a tin plating layer having an average thickness of 0.45 μm was formed on the lead portion. . The ratio of the thickness of the first electroless tin plating layer to the thickness of the second electroless plating layer is 1:10, and the first electroless plating layer is formed of the second electroless plating layer. It is formed thinner than the electrolytic plating layer.

After performing the electroless tin plating in this manner, the substrate was washed with water, and the plated layer was heated to 130 ° C. to produce a film carrier tape for mounting electronic components. By observing the lead portion of the obtained film carrier tape for mounting electronic components, a lead in which the lead was broken was selected, and a photograph of a cross section of this portion was taken. From this cross-sectional photograph, the depth of lead screeching was measured. FIG. 2 shows the results.
[Reference Examples 7 to 12]
In Example 1 to 6, an electronic component mounting form carrier tape was manufactured in the same manner except that the soft etching treatment was not performed. By observing the lead portion of the obtained film carrier tape for mounting electronic components, a lead in which the lead was broken was selected, and a photograph of a cross section of this portion was taken.

  From this cross-sectional photograph, the depth of lead screeching was measured. FIG. 2 shows the results.

  A film carrier tape for mounting electronic components was manufactured in the same manner as in Reference Example 2, except that the electroless tin plating of the lead portion was performed in one stage. The total thickness of the thus formed electroless tin plating was 0.45 μm. By observing the lead portion of the obtained film carrier tape for mounting electronic components, a lead in which the lead was broken was selected, and a photograph of a cross section of this portion was taken.

When the depth of the lead undercut was measured from this cross-sectional photograph, the depth of the generated lead undercut was 4 μm, which was deeper than that of Reference Example 2.
[Reference Example 13]
In Reference Example 2, before applying the solder resist, the wiring pattern was soft-etched, and then a press plating layer having a thickness of 0.03 μm was formed by electroless tin plating. To form a solder resist layer, and an electroless tin-plated layer was formed on the lead portion extending from the solder resist layer in the same manner as in Reference Example 2. The total thickness of the tin plating layer thus formed was 0.45 μm.

By observing the leads of the obtained film carrier tape for mounting electronic components, a lead having a chipped lead was searched for, but no chipped lead was found.
[Reference Example 14]
In Reference Example 2, after changing the Sn ²⁺ concentration in the press plating bath to 15 g / liter and performing press plating at room temperature for 10 seconds, 30 seconds, 60 seconds, 120 seconds, and 210 seconds, the main plating conditions were as follows: The tin plating was performed at 70 ° C. for a time of 210 seconds and a Sn ²⁺ concentration of 20 g / liter. The surface to be plated is not soft-etched.

  Pressing plating was performed for various times as described above, and the lead portion after the tin plating was observed. By observing the lead portion of the obtained film carrier tape for mounting electronic components, a lead in which the lead was broken was selected, and a photograph of a cross section of this portion was taken. When the depth of the lead digging was measured from this cross-sectional photograph, the depth of the digging gradually became shallower as the press plating time became longer, and the depth of the digging became stable at about 5 μm between 30 seconds and 60 seconds.

  The result is shown in FIG.

In Reference Example 1, the Sn ²⁺ concentration was changed to 15 g / l, 20 g / l, and 27 g / l by changing the blending amount of tin borofluoride Sn (BF ₄ ) ₂ without performing press plating on the soft-etched lead surface. Tin plating was performed. By observing the lead portion of the obtained film carrier tape for mounting electronic components, a lead in which the lead was broken was selected, and a photograph of a cross section of this portion was taken.

  The depth of the lead digging was measured from this cross-sectional photograph, and the results are shown in Table 2 below.

The tin plating conditions are as follows: plating temperature: 70 ° C., plating time: 210 seconds. From the above results, the Sn ²⁺ concentration at the time of the present tin plating is adjusted to the range specified in the present invention by mixing tin borofluoride Sn (BF ₄ ) ₂ , so that the depth of the undercut can be obtained without performing press plating. Is reduced.

In the method for producing a film carrier tape for mounting an electronic component of the present invention, a tin plating layer is formed by mixing tin borofluoride [Sn (BF ₄ ) ₂ ] and using a tin plating bath having a specific Sn ²⁺ concentration. In addition, it is possible to suppress the occurrence of the curving portion in the lower part of the solder resist. Also, even if a scoring part is formed in the wiring pattern on the lower surface of the solder resist layer by electroless tin plating, the depth of the scoring part becomes shallow, preventing lead strength reduction, lead disconnection, etc. Can be.

In particular, the method for producing a film carrier tape for mounting electronic components of the present invention is highly useful in producing a film carrier tape having a fine pitch, for example, having a very fine pitch lead portion having a lead width of 25 μm or less. Also in the film carrier tape, it is possible to suppress the occurrence of a curving portion that can be a serious defect of the film carrier tape such as a substantial decrease in lead strength and disconnection of leads.

  Therefore, by using the electronic component mounting film carrier tape prepared by the method for manufacturing an electronic component mounting film carrier tape of the present invention, the device can be mounted more reliably, and the aging of the film carrier tape can be improved. It is also unlikely that defects such as a drop in strength and disconnection will occur.

FIG. 1 is a diagram schematically showing a scorched portion of a lead caused by electroless tin plating. FIG. 2 is a graph showing the relationship between the Sn ²⁺ concentration in the press plating bath and the lead scuffing depth (scrapping amount). FIG. 3 is a diagram showing an embodiment in which a press plating layer and a main plating layer are provided. FIG. 4 is a diagram showing an embodiment in which a press plating layer is provided under a solder resist. FIG. 5 is a graph showing the relationship between the press plating time and the undercut depth.

Claims (4)

Tin borofluoride [Sn (BF ₄ ) ₂ ] is blended into the lead portion of a wiring pattern formed of copper or a copper alloy on a flexible insulating film, and the Sn ²⁺ concentration is within a range of 13 to 50 g / liter. This tin plating was performed at least once using an electroless tin plating bath adjusted to an average thickness of 0.2.
A method for producing a film carrier tape for mounting electronic components, comprising forming a tin plating layer having a thickness of about 0.7 μm.   2. The method for manufacturing a film carrier tape for electronic component mounting according to claim 1, wherein a tin-plated surface is soft-etched before tin-plating the wiring pattern formed on the flexible insulating film. .   The electronic component mounting according to claim 1, wherein the wiring pattern on which the tin plating layer is formed is formed using an electrolytic copper foil having an average thickness of 7 to 35 μm. Manufacturing method of film carrier tape for use.   3. The method according to claim 1, wherein the wiring pattern is formed of a metal layer by a vapor deposition method or a plating method.

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