JPS6152237B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a partial treatment method such as partial plating using masking tape. Traditionally, when applying a treatment such as partial plating to the surface of an object, masking tape is pasted on the parts of the surface that do not require treatment, then plating or other treatment is applied to the areas that need treatment, and after this treatment, the above masking tape is applied. A partial treatment method is being used to peel off the material. This method requires that the masking tape adheres well to the parts of the object's surface that do not require treatment, and if the masking tape does not adhere well, liquid may leak to the parts that do not require treatment. A sufficient masking effect cannot be obtained. However, if the adhesive force of the masking tape is too high, it will be difficult to peel off the tape after processing. For this reason, the adhesive strength of the masking tape must be adjusted to a level that does not cause the above-mentioned leakage and does not make it difficult to peel off after processing, but this adjustment is difficult. In some cases, the above-mentioned liquid leakage may occur, or the workability when peeling off the tape after treatment may be low, or furthermore, the object may be deformed when the tape is peeled off. Particularly during partial plating in the manufacture of electronic components such as IC lead frames and transistor lead frames, problems such as leakage of liquid to parts that do not need to be plated or deformation of the plated object when the masking tape is removed after plating may occur due to electrical characteristics or other problems. This will have a large impact on the characteristics of the parts, and since partial plating is usually performed continuously in the production of the electronic parts mentioned above, if the masking tape peeling efficiency after plating is low, production efficiency will deteriorate. The adhesive strength of the masking tape has a large influence. Therefore, in view of the above circumstances, the inventors conducted intensive studies to improve the reliability and workability of partial processing methods such as partial plating using masking tape, and as a result, they came up with this invention. . That is, when applying a treatment such as plating to a part of the surface of an object, the present invention applies a masking tape to the portion of the surface that does not require treatment, then applies treatment such as plating to the portion that requires treatment, and after this treatment, the above-mentioned In a partial treatment method for peeling off a masking tape, the masking tape has a light-transmitting support, a pressure-sensitive adhesive layer provided on the support, and having a property of being cured into a three-dimensional network by being irradiated with light. This partial treatment method is characterized in that the masking tape is irradiated with light after a treatment such as plating and before the masking tape is peeled off. According to the method of the present invention, the adhesive force of the masking tape can be made large enough to reliably obtain a masking effect without considering the peeling workability after plating, so this Masking tape has good adhesion and strong adhesion to parts of the surface of objects that do not require treatment, and does not cause leakage of processing liquids such as plating liquid. On the other hand, after treatments such as plating, the pressure-sensitive adhesive layer of the masking tape is cured and becomes a three-dimensional network by irradiating the masking tape with light, which increases the cohesive force of this adhesive layer and causes it to become sticky. As masking tape loses most of its properties, the adhesive force of the masking tape to the surface of the object is significantly reduced. Therefore, this tape can be removed extremely easily, has good peeling workability, and does not deform the object to be processed. . As described above, according to the method of the present invention, processes such as partial plating can be performed using masking tape with excellent reliability and workability. Particularly, the method of the present invention is effective when a process such as partial plating is continuously performed in the manufacture of electronic parts. Examples of the light-transmissive support constituting the masking tape used in the method of the present invention include plastic films such as polyvinyl chloride, polyethylene terephthalate, polyethylene, and polypropylene. The thickness of this film is usually about 10 to 200 μm. This pressure-sensitive adhesive layer, which is provided on a light-transmitting support and has the property of curing and forming a three-dimensional network when exposed to light, can be applied to a normal rubber-based or acrylic-based pressure-sensitive adhesive layer, for example. at least 2
It is formed using a pressure-sensitive adhesive composition containing a low molecular weight compound having photopolymerizable carbon-carbon double bonds (hereinafter referred to as a photopolymerizable compound) and a photopolymerization initiator. The above rubber-based or acrylic-based pressure-sensitive adhesives can be copolymerized with rubber-based polymers such as natural rubber and various synthetic rubbers, poly(meth)acrylic acid alkyl esters, and (meth)acrylic acid alkyl esters. The base polymer is an acrylic polymer such as a copolymer with other unsaturated monomers, and a crosslinking agent such as a polyisocyanate compound or an alkyl etherified melamine compound is blended therein as necessary. In addition, the above-mentioned base polymer may have a photopolymerizable carbon-carbon double bond in the molecule. The above photopolymerizable compounds usually have a molecular weight of
The molecular weight is preferably about 10,000 or less, and more preferably, the molecular weight is about 5,000 or less and photopolymerizable carbon-carbon in the molecule so that the pressure-sensitive adhesive layer can be efficiently formed into a three-dimensional network by light irradiation. Particularly preferred photopolymerizable compounds having 2 to 6 double bonds include, for example, trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, pentaerythritol triacrylate, and pentaerythritol. Examples include tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, and the like. In addition, other photopolymerizable compounds include 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate,
Examples include polyethylene glycol diacrylate and commercially available oligoester acrylate. As the photopolymerizable compound, one type of the above compounds may be used alone or two or more types may be used in combination, and the amount used is usually 1 part by weight per 100 parts by weight of the above base polymer. The range is preferably 100 parts by weight. If the amount used is too small, the three-dimensional reticulation of the pressure-sensitive adhesive layer by light irradiation will be insufficient, and the degree of decrease in adhesive force to the object surface will be too small, which is not preferable. Furthermore, if the amount used is too large, the pressure-sensitive adhesive layer will become significantly plasticized, making it impossible to obtain the adhesive force necessary for cutting semiconductor wafers, which is not preferable. Examples of the above-mentioned photopolymerization initiators include isopropyl benzoin ether, isobutyl benzoin ether, benzophenone, Michler's ketone,
Examples include chlorothioxanthone, dodecylthioxanthone, dimethylthioxanthone, diethylthioxanthone, acetophenone diethyl ketal, benzyl dimethyl ketal, α-hydroxycyclohexyl phenyl ketone, 2-hydroxymethyl phenyl propane, etc., and one of these may be used alone. It may be used alone or in a mixture of two or more. The amount of the photopolymerization initiator to be used is usually in the range of 0.1 to 5 parts by weight per 100 parts by weight of the base polymer. If the amount used is too small, the three-dimensional reticulation of the pressure-sensitive adhesive layer by light irradiation will be insufficient, and the degree of decrease in adhesive force to the object surface will be too small, which is not preferable. Moreover, if the amount used is too large, not only the corresponding effect will not be obtained, but also this photopolymerization initiator will remain on the surface of the object, which is not preferable. Note that, if necessary, an amine compound such as triethylamine, tetraethylpentamine, dimethylaminoethanol, etc. may be used together with this photopolymerization initiator as a photopolymerization accelerator. In order to form a pressure-sensitive adhesive layer using a pressure-sensitive adhesive composition formed by mixing the above-mentioned components, this composition is coated on a light-transmitting support and heated as necessary. Bye. The thickness of the pressure-sensitive adhesive layer formed in this way is usually 1 to 100 μm.
It is better to be m. In addition, this pressure-sensitive adhesive layer usually has a 100% modulus (at 20°C) of 10 kg/cm ² or less,
Further, it is usually preferable that the gel fraction determined by immersion in toluene for 24 hours is less than 55% by weight and the swelling degree of the gel is 20 times or more. In order to carry out a treatment such as partial plating using the above-mentioned masking tape consisting of a light-transmitting support and a pressure-sensitive adhesive layer, first apply it to the untreated areas of the surface of an object made of metal or non-metal such as plastic. This masking tape is pasted, and then a treatment such as plating is applied to the portions of the surface of the object that require treatment. Examples of this treatment include ordinary plating treatments such as electroplating, chemical plating, electroforming, melt plating, vacuum plating, and vapor phase plating, as well as chemical conversion treatment, anodizing treatment, metal coloring treatment, etc.
The treatment may be carried out by spraying the treatment liquid onto the area that requires treatment, or by immersing the object in the treatment liquid. In the method of this invention, after the above treatment, the masking tape is exposed to light with a wavelength of 180 to 460 μm, usually for 5 to
The tape is irradiated for about 60 seconds and then peeled off. The above masking tape on the object surface
The 180° peel adhesive force (peel speed 300mm/min) is usually 200 to 1500g/20mm before irradiation with light, and during treatments such as plating, it adheres strongly to the surface of the object with good adhesion and removes the processing liquid. Excellent masking effects can be achieved without causing any leakage. On the other hand, when the pressure-sensitive adhesive layer of the above masking tape is irradiated with light, the photopolymerizable compounds polymerize with each other, radicals are generated in the base polymer, and this polymer and photopolymerizable compound react. , the adhesive layer is cured to form a three-dimensional network. Note that three-dimensional reticulation here generally means that the gel fraction determined by immersing the adhesive layer in toluene for 24 hours is approximately 1.4 times or more of that before light irradiation, and that this gel fraction is 55% by weight. This means the above. Further, it is preferable that the adhesive layer after light irradiation has a gel swelling degree of usually 18 times or less, which is determined in the same manner as above. By creating a three-dimensional network in this way, the cohesive force of the adhesive layer increases significantly compared to before light irradiation,
Normally, 100% modulus (20℃) is 20Kg/cm ² or more. As a result, the adhesive layer loses most of its tackiness, and the adhesion of the masking tape to the surface of the object is significantly reduced. At this time, the 180° peel adhesive force (peel speed 300 mm/min) is usually 150 g/min.
It will be less than 20mm. Therefore, the masking tape can be easily peeled off after treatment. The figure shows an example of an apparatus for continuously performing processes such as partial plating according to the method of the present invention. Reference numeral 1 denotes a supply roll for delivering objects to be subjected to a process such as partial plating, and 2 represents a supply roll for delivering masking tape. 3 is a pressure roll, and the masking tape 5 sent out from the supply roll 2 is applied to the unnecessary part of the object 4 sent out from the supply roll 1 by the pressure roll 3.
is crimped. This masking tape 5 is made up of a light-transmissive plating and a pressure-sensitive adhesive layer provided on the support that has the property of curing and forming a three-dimensional network when irradiated with light, and masks the parts of the object 4 that do not need to be processed in advance. It is wound into a coil shape (for example, it has a shape in which perforations, linear openings, etc. are provided so that these parts are required to be processed, and other parts are not required to be processed), and wound into a coil. In addition, the adhesive force of this masking tape 5 is set to be large enough to firmly adhere to the object 4 with good adhesion.The masking tape 5 fed from the supply roll 2 is in the form of a normal tape, and is crimped. Just before roll 3, apply this masking tape 5 to object 4.
A means for shaping the object 4 into a shape capable of masking the unprocessed portion of the object 4 may be provided, and the masking tape 5 formed into a predetermined shape by this means may be pressed onto the unprocessed portion of the object 4 by the pressure roll 3. The object 4 and the masking tape 5 that have been crimped by the crimping roll 3 are sent together to a processing section 6 using a plating liquid or the like, where the portions of the object 4 that require processing are subjected to processing such as plating. In this case, since the masking tape 5 adheres firmly and with good adhesion to the parts of the object 4 that do not need to be processed, the process such as plating can be applied only to the parts that need to be processed without causing liquid leakage. The processing method in the processing section 6 may be a method of spraying a processing liquid such as a plating solution, or a method of immersing it in a processing liquid. After the above processing, the object 4 and the masking tape 5 are sent together to a post-processing section 7 where they are subjected to post-processing such as cleaning and drying, and then sent to a light irradiation section 8. Here, the masking tape 5 is irradiated with light, and the pressure-sensitive adhesive layer of this tape 5 is photocured and becomes a three-dimensional network, increasing its cohesive force. The adhesion strength to No. 4 is significantly reduced. Therefore, the masking tape 5 is very easily peeled off from the object 4 by the next peeling roll 9 and wound onto the take-up roll 10. On the other hand, the object 4, which has been treated with a plating liquid or the like only in the portions that require treatment, is wound up on the take-up roll 11, thereby completing the partial treatment. When carrying out partial processing in this way, it is especially necessary that the masking tape can be easily peeled off after processing, but the method of the present invention reduces the reliability of the masking effect during processing. The masking tape can be easily peeled off after treatment without any problems. Therefore, the method of the present invention is suitable for continuous manufacturing of electronic components such as IC lead frames and transistor lead frames, where reliability of the masking effect during processing and easy peeling of the masking tape after processing are important. It is particularly effective for processing such as partial plating. Examples of this invention will be described below. In addition, in the following, parts mean parts by weight. Example 1 100 parts of butyl acrylate, 5 parts of acrylonitrile
A polymerization raw material consisting of 1 part and 3 parts of acrylic acid was copolymerized in toluene to obtain an acrylic copolymer having a number average molecular weight of 300,000. To 100 parts of this copolymer, add a polyisocyanate compound (product name: Coronate L, manufactured by Nippon Polyurethane Co., Ltd.)
5 parts of dipentaerythritol monohydroxypentaacrylate and 1 part of α-hydroxycyclohexyl phenyl ketone were added and mixed to prepare a pressure sensitive adhesive composition. This composition was coated on one side of a 70 μm thick polyvinyl chloride film so that the adhesive layer had a thickness of 10 μm, and heated at 130° C. for 3 minutes to obtain a masking tape. Using this masking tape, use the device shown in the figure (however, a means was provided just before the pressure roll 3 to shape the masking tape into a shape that would mask the unnecessary parts of the object to be partially plated). Then, continuous partial plating was applied to a thin copper metal plate. That is, the thin metal sheet 4 fed out from the supply roll 1 and the masking tape 5 fed out from the feed roll 2 and shaped so as to be able to mask the unnecessary portions of the thin metal sheet 4 immediately before the pressure bonding roll 3 are placed on the pressure bonding roll 3. They were crimped together to form a single body, and then both were sent to the plating solution processing section 6, where they were immersed in an electroplating bath of gold plating (PH4 to 5). After that, the masking tape 5 is washed and dried through the plating post-processing section 7, and then the masking tape 5 is placed in the light irradiation section 8.
Then, ultraviolet rays were irradiated for 20 seconds from a distance of 15 mm using a high-pressure mercury lamp (40 W/cm), and then the masking tape 5 was peeled off with a peeling roll 9 and wound onto a winding roll 10. On the other hand, the partially plated thin metal sheet 4 was taken up by a take-up roll 11. The masking tape 5 was peeled off after plating very easily, and the thin metal plate 4 was not deformed during this peeling, and there was no residual adhesive on the surface of the thin metal plate 4. In addition, the thin metal plate 4 was plated with high accuracy only in the areas that required plating, and the masking effect of the above-mentioned masking tape was excellent. Note that the masking tape 5 has a 180° peel adhesion force (peel speed 300
mm/min) was 300 g/20 mm before UV irradiation and 20 g/20 mm after UV irradiation. Comparative Example A masking tape was obtained in the same manner as in Example 1, except that 15 parts of dipentaerythritol monohydroxypentaacrylate and 1 part of α-hydroxycyclohexyl phenyl ketone were not used. Using this masking tape, a copper metal thin plate was continuously partially plated in the same manner as in Example 1, but when the masking tape was peeled off after plating, the metal thin plate was significantly deformed and no adhesive remained on the metal thin plate. occurred. Further, when partial plating was performed continuously in the same manner as above except that the masking tape was not passed through the light irradiation section 8, the thin metal plate 4 was deformed when the masking tape was peeled off after plating. In addition, the 180° peel adhesive strength of the above masking tape to the above metal thin plate (peel speed 300 mm/
minutes) was 300 g/20 mm before UV irradiation and 1.200 g/20 mm after UV irradiation. Example 2 Acrylic copolymer (same as Example 1)
100 parts of polylysocyanate compound (Example 1
) 5 parts, 20 parts of pentaerythritol acrylate and isobutyl benzoin ether
0.5 part was added and mixed to prepare a pressure sensitive adhesive composition. A masking tape was obtained using this composition in the same manner as in Example 1. Using this masking tape, a thin copper metal plate was continuously partially plated in the same manner as in Example 1. By this partial plating, the thin metal plate was plated with high precision only in the areas that required plating, and the masking effect of the above-mentioned masking tape was excellent. Furthermore, the masking tape was extremely easy to peel off after plating, and the thin metal plate was not deformed and no adhesive remained. In addition, the 180° peel adhesive strength of the above masking tape to the above metal thin plate (peel speed 300 mm/
minutes) was 480 g/20 mm before UV irradiation and 60 g/20 mm after UV irradiation. Example 3 Acrylic copolymer (same as Example 1)
To 100 parts, 5 parts of a polyisocyanate compound (same as in Example 1), 10 parts of dipentaerythritol monohydroxypentaacrylate, 1 part of dimethylthioxanthone, and 1 part of triethylamine were added and mixed to prepare a pressure-sensitive adhesive composition. . A masking tape was obtained using this composition in the same manner as in Example 1. Using this masking tape, a thin copper metal plate was continuously partially plated in the same manner as in Example 1. By this partial plating, the thin copper metal plate was plated with high precision only in the areas that required plating, and the masking effect of the above-mentioned masking tape was excellent. Furthermore, the masking tape was extremely easy to peel off after plating, and the thin copper metal plate was not deformed and there was no residual adhesive. In addition, the 180° peel adhesion of the above masking tape to the above copper metal thin plate (peel speed 300
mm/min) was 380 g/20 mm before UV irradiation and 25 g/20 mm after UV irradiation. Test Example <100% Modulus> 50μ of the pressure-sensitive adhesive compositions used in Examples 1 to 3 and Comparative Examples above were subjected to release treatment.
The surface of a polyethylene terephthalate film with a thickness of m is coated to a thickness of 10 μm, and 130
After heating at ℃ for 3 minutes, cut into pieces of 50mm/50mm and gather them into a bar shape so that the cross-sectional area is 0.5
A filamentous specimen of mm ² was obtained. About this specimen20
The 100% modulus at °C was measured. Also,
A high-pressure mercury lamp (40W/cm) was applied to this test piece.
The same 100% modulus was measured after UV irradiation for 20 seconds from a distance of 15 cm. <Gel fraction, swelling degree of gel> Each of the above pressure-sensitive adhesive compositions was coated and heated in the same manner as for the 100% modulus test piece, and then cut into a size of 50 mm x 500 mm. This was used as a test piece. Add this test piece to toluene for 24 hours.
The gel fraction and swelling degree of the gel were examined by immersion for a time.
In addition, this test piece was irradiated with light under the same conditions as above, and then immersed in toluene for 24 hours to examine the gel fraction and swelling degree of gel. The above test results are shown in the table below. In addition, in the table below, column A shows the measured value before light irradiation,
Column B shows the measured values after light irradiation.

[Table] As is clear from the above examples, according to the partial plating method of the present invention, when plating, the masking tape firmly adheres to the parts of the surface of the object that do not need plating, and exhibits an excellent masking effect. Afterwards, the masking tape can be easily peeled off by irradiating it with light. Also, the reason why masking tape can be easily peeled off is because the pressure-sensitive adhesive layer of this tape forms a three-dimensional network when irradiated with light, and its cohesive strength increases significantly, resulting in a significant decrease in its adhesion to objects. It is clear that this is for the purpose of

[Brief explanation of the drawing]

The figure is a schematic configuration diagram showing an example of an apparatus for continuously performing treatments such as partial plating according to the partial treatment method of the present invention. 4...object, 5...masking tape.

Claims (1)

[Claims] 1 When applying a treatment such as plating to a part of the surface of an object, apply masking tape to the part of the surface that does not require treatment, then apply treatment such as plating to the part that does not require treatment, and after this treatment, peel off the above masking tape. In the partial treatment method, the masking tape is composed of a light-transmitting support and a pressure-sensitive adhesive layer provided on the support and having a property of curing and forming a three-dimensional network by light irradiation,
A partial treatment method for partial plating, etc., characterized in that the masking tape is irradiated with light after the treatment such as plating and before the masking tape is peeled off.