Abstract:
The present invention provides a printed circuit board whose insulating layer is not melt-adhered to a heating tool, to thereby enhance reliability and productivity of a semiconductor chip mounting line, and also provides a method of producing the printed circuit board. The printed circuit board contains a flexible printed wiring board and a semiconductor chip mounted on the flexible printed wiring board, wherein the flexible printed wiring board includes: an insulating layer  12  and a wiring pattern  21  formed of a conductor layer  11  provided on at least one side of the insulating layer  12  and a releasing layer  13  provided on a surface of the insulating layer  12 , which surface is opposite to the mounting side of the semiconductor chip.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a printed circuit board comprising a flexible printed wiring board such as a COF film carrier tape or an FPC (flexible printed circuit) on which electronic parts (semiconductor chips) such as ICs and LSIs are mounted. The term “COF film carrier tape” refers to a film substrate assuming the form of tape onto which electronic devices (chips) are to be mounted. The invention also relates to a method of producing the printed circuit board. 
   2. Description of the Related Art 
   Development of the electronics industry has been accompanied by sharp demand for printed-circuit boards for mounting electronic devices thereon, such as ICs (Integrated Circuits) and LSIs (Large-Scale Integrated circuits). Manufacturers have attempted to realize small-size, lightweight, and high-function electronic equipment, which has long been desired. To this end, manufactures have recently come to employ a film carrier tape, such as a TAB (tape automated bonding) tape, a T-BGA (ball grid array) tape, an ASIC tape, or an FPC (flexible printed circuit). Use of film carrier tapes for mounting electronic devices thereon has become of increasing importance, especially for manufacturers of personal computers, cellular phones, and other electronic equipment employing a liquid crystal display (LCD) that must have high resolution and flatness, as well as a narrow screen-frame area. 
   In addition, in order to attain higher-density mounting on a narrower space, mounting of bare IC chips directly on a flexible printed wiring board has been employed. Such a product is called COF (chip-on-film). 
   Since the flexible printed wiring board serving as a substrate of COFs does not have a device hole, a laminate film obtained by laminating in advance a conductor layer and an insulating layer is employed as the flexible printed wiring board. When IC chips are directly mounted on the wiring pattern, positioning is performed on the basis of marks such as an inner lead and a positioning mark which are visible through the insulating layer, followed by joining the IC chips and the wiring pattern; i.e., the inner lead, by means of a heating tool (see, for example, Japanese Patent Application Laid-Open (kokai) No. 2002-289651, FIGS. 4 to 6 and paragraphs [0004] and [0005]). 
   Such semiconductor chips are mounted while the insulating layer is in direct contact with a heating tool. Since the insulating layer is heated to a considerably high temperature by the heating tool during mounting, a portion of the insulating layer is caused to adhere to the heating tool by melting, thereby causing stoppage of a production apparatus. In addition, unfavorable deformation of the carrier tape occurs. In the case where the insulating layer is melt-adhered to the heating tool, the heating tool is stained, thereby deteriorating reliability and productivity. 
   Such melt adhesion to the heating tool is critical when semiconductor chips are mounted on a COF film carrier tape or a COF FPC having no device hole. 
   SUMMARY OF THE INVENTION 
   In view of the foregoing, an object of the present invention is to provide a printed circuit board whose insulating layer is not melt-adhered to a heating tool, to thereby enhance reliability and productivity of a semiconductor chip mounting line. Another object of the invention is to provide a method of producing the printed circuit board. 
   Accordingly, in a first aspect of the present invention, there is provided a printed circuit board comprising a flexible printed wiring board and a semiconductor chip mounted on the flexible printed wiring board, wherein the flexible printed wiring board includes: an insulating layer; a wiring pattern formed of a conductor layer provided on at least one side of the insulating layer and a releasing layer provided on a surface of the insulating layer, which surface is opposite to the mounting side of the semiconductor chip. 
   Through employment of the flexible printed wiring board according to the first aspect, the releasing layer is brought into direct contact with a heating tool during mounting of semiconductor chips. Thus, melt adhesion between the layer and the heating tool does not occur, thereby preventing staining of the heating tool caused by melt adhesion of the insulating layer. 
   In the second aspect of the present invention, the releasing layer may comprise a silicone series compound. 
   Through employment of the above construction according to the second aspect, the releasing layer which is to be in contact with a heating tool and comprises a silicone series compound, melt adhesion or a similar phenomenon can be reliably prevented. 
   In the third aspect of the present invention, a silicone series compound or elemental silicon may be in existence, in a portion opposite to the region defined when the semiconductor chip is orthogonally projected onto the layer, in a continued form or in the form of discontinuous islands. 
   Through embodiment of the above construction according to the third aspect, the semiconductor ship has been mounted, the silicone series compound or the elemental silicon contained in the releasing layer is observed on the side of the insulating layer opposite the side to which the semiconductor chip is mounted. 
   In the forth aspect of the present invention, the releasing layer may be formed from a releasing agent containing at least one species selected from among a siloxane compound, a silane compound, and silica sol. 
   Through embodiment of the above construction according to the forth aspect, the releasing layer to be in contact with a heating tool is formed from a releasing agent containing a siloxane compound, a silane compound, or silica sol, melt adhesion or a similar phenomenon can be reliably prevented. 
   In the fifth aspect of the present invention, the releasing layer may be formed by coating a solution containing the releasing agent to the insulating layer and heating. 
   Through embodiment of the above construction according to the fifth aspect, releasing layer which reliably prevents melt adhesion is formed through the application method. 
   In the sixth aspect of the present invention, the releasing layer may be formed by transferring the releasing layer provided on a transfer film substrate. 
   Through embodiment of the above construction according to the sixth aspect, releasing layer can be readily formed through the transfer method. 
   In the seventh aspect of the present invention, the flexible printed wiring board may be a COF film carrier tape. 
   Through embodiment of the above construction according to the seventh aspect, the releasing layer is brought into direct contact with a heating tool during mounting of semiconductor chips on the COF film carrier tape. Thus, melt adhesion between the layer and the heating tool does not occur, thereby preventing staining of the heating tool caused by melt adhesion of the insulating layer. 
   In the eighth aspect of the present invention, there is provided a method of producing a printed circuit board comprising: producing a flexible printed wiring board which includes: an insulating layer; a wiring pattern formed of a conductor layer provided on at least one side of the insulating layer and a releasing layer provided on a surface of the insulating layer, which surface is opposite to the mounting side of a semiconductor chip; and mounting the semiconductor chip on the flexible printed wiring board. 
   Through embodiment of the above construction according to the eighth aspect, the releasing layer is brought into direct contact with a heating tool during mounting of semiconductor chips. Thus, melt adhesion between the layer and the heating tool does not occur, thereby preventing staining of the heating tool caused by melt adhesion of the insulating layer. 
   In the ninth aspect of the present invention, the semiconductor chip may be mounted by use of a heating tool which is to be in direct contact with the releasing layer and heated at 200° C. or higher. 
   Through embodiment of the above construction according to the ninth aspect, the releasing layer is brought into direct contact with a heating tool heated at 200° C. or higher during mounting of semiconductor chips. Thus, strong adhesion between the layer and the heating tool does not occur, thereby preventing staining of the heating tool caused by melt adhesion of the insulating layer. 
   In the tenth aspect of the present invention, the releasing layer may comprise a silicone series compound. 
   Through embodiment of the above construction according to the tenth aspect, the releasing layer, which is to be in contact with a heating tool, comprises a silicone series compound, so melt adhesion or a similar phenomenon can be reliably prevented. 
   In the eleventh aspect of the present invention, a method of producing a printed circuit board, a silicone series compound or elemental silicon may be in existence, in a portion opposite to the region defined when the semiconductor chip is orthogonally projected onto the layer, in a continued form or in the form of discontinuous islands. 
   Through embodiment of the above construction according to the eleventh aspect; the semiconductor chip has been mounted, the silicone series compound or the elemental silicon contained in the releasing layer is observed on the side of the insulating layer opposite the side to which the semiconductor chip is mounted. 
   In the twelfth aspect of the present invention, the releasing layer may be formed from a releasing agent containing at least one species selected from among a siloxane compound, a silane compound, and silica sol. 
   Through embodiment of the above construction according to the twelfth aspect, the releasing layer to be in contact with a heating tool is formed from a releasing agent containing a siloxane compound, a silane compound, or silica sol, melt adhesion or a similar phenomenon can be reliably prevented. 
   In the thirteenth aspect of the present invention, the releasing layer may be formed by coating a solution containing the releasing agent to the insulating layer and heating. 
   Through embodiment of the above construction according to the thirteenth aspect, the releasing layer which reliably prevents melt adhesion is formed through the application method. 
   In the fourteenth aspect of the present invention, the releasing layer may be formed by transferring the releasing layer provided on a transfer film substrate. 
   Through embodiment of the above construction according to the fourteenth aspect, the releasing layer can be readily formed through the transfer method. In the fifteenth aspect of the present invention, the flexible printed wiring board may be a COF film carrier tape. 
   Through embodiment of the above construction according to the fifteenth aspect, the releasing layer is brought into direct contact with a heating tool during mounting of semiconductor chips on the COF film carrier tape. Thus, melt adhesion between the layer and the heating tool does not occur, thereby preventing staining of the heating tool caused by melt adhesion of the insulating layer. 
   As described hereinabove, the printed circuit board (e.g., COF film carrier tape or COF FPC) of the present invention has a specific silicone series releasing layer. Therefore, melt adhesion of the insulating layer of the film carrier tape to a heating tool is prevented during mounting of semiconductor chips, to thereby enhance reliability and productivity of a semiconductor chip mounting line. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various other objects, features, and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood with reference to the following detailed description of the preferred embodiments when considered in connection with accompanying drawings, in which: 
       FIG. 1  is a cross-sectional view of a printed circuit board according to one embodiment of the present invention; 
       FIG. 2A  is a schematic plan view of a COF film carrier tape according to one embodiment of the present invention; 
       FIG. 2B  is a cross-sectional view of the COF film carrier tape according to the same embodiment of the present invention; 
       FIGS. 3A  to  3 G are cross-sectional views showing a method of producing a COF film carrier tape according to one embodiment of the present invention; 
       FIGS. 4A  to  4 E are cross-sectional views showing a laminate film for producing a COF according to another embodiment of the present invention; and 
       FIG. 5  is a cross-sectional view showing a method of producing a printed circuit board according to one embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   The COF film carrier tape which is used in the printed circuit board of the present invention comprises a conductor layer and an insulating layer. No particular limitation is imposed on the laminate film comprising a conductor layer and an insulating layer and used in the COF flexible printed wiring board, and any type of conductor-insulator laminate film can be employed. Examples of such laminate film include a laminate film prepared by sputtering a bond-improving layer (e.g., Ni) on an insulating film (e.g., polyimide film) and plating copper on the bond-improving layer; a casting-type laminate film prepared by coating polyimide to copper foil; and a laminate film prepared through hot-press-adhesion of an insulating film onto copper foil using of a thermoplastic or thermosetting resin. 
   The COF flexible printed wiring board of the present invention or the COF flexible printed wiring board produced through the method of the present invention comprises the aforementioned laminate film and a releasing layer which is provided on the insulating layer of the laminate film opposing the side on which a semiconductor chip is to be mounted. In the production method of the present invention, no particular limitation is imposed on the material for forming the releasing layer, so long as the material has such releasability that adhesion of the laminate film to a heating tool during mounting of semiconductor chips is prevented and does not induce melt adhesion by heat. Both inorganic and organic materials are employable. Examples of preferred releasing agents include a silicone series compound, an epoxy series compound, or a fluorine-containing compound, more preferably a silicone series compound; i.e., a compound having a siloxane bond (Si—O—Si). A releasing layer comprising a silicone series compound is preferred, since the layer can be formed in a relatively simple manner and does not tend to adversely affect adhesion of mold resin even when the releasing layer is transferred to a mount side of the produced printed wiring board. 
   Examples of the releasing agents for forming a releasing layer comprising a silicone series compound; i.e., a compound having a siloxane bond, include silicone series releasing agents. 
   More specifically, such releasing agents contain at least one species selected from among siloxane compounds such as disiloxane and trisiloxane. Preferably, the releasing agent comprises a compound which transforms into a silicone series compound through application and reaction of the releasing agent. Examples of such compounds include silane compounds such as monosilane, disilane, and trisilane; and silica sol series compounds. 
   Examples of more preferred releasing agents include releasing agent containing an alkoxysilane compound, or a silazane compound such as hexamethyldisilazane or perhydropolysilazane, which belongs to silane compounds having a Si—NH—Si structure serving as a precursor for forming a siloxane bond. These releasing agents form a releasing layer comprising a compound having a siloxane bond through application thereof or reaction with moisture or a similar substance contained in air after the application. However, for example, in case silazane compound is used, unreacted Si—NH—Si may also be present in the releasing layer. 
   As described above, the most preferred releasing layer is formed of the silicone series compound formed by reaction after the application. 
   Although the above releasing agents generally contain an organic solvent, similar releasing agents of aqueous solution type or emulsion form may also be employed. 
   Specific examples of the releasing agents include silicone series resin SR 2411 (trade name: product of Dow Corning Toray Silicone Co., Ltd., containing dimethylsiloxane-series silicone series oil, methyltri(methyl ethyl ketoxime)silane, toluene, and ligroin); silicone series resin SEPA-COAT (trade name: product of Shin-Etsu Chemical Co., Ltd., containing silazane, synthetic isoparaffin, and ethyl acetate); and COLCOAT SP-2014S (trade name: product of Colcoat Co., Ltd., containing a silane compound). Examples of releasing agents containing silica sol include COLCOAT P and COLCOAT N-103X (trade names: products of Colcoat Co., Ltd.). A grain size of silica contained in silica sol is, for example, 50 to 80 Å (angstrom). 
   Notably, provision of a releasing layer formed of a silicone series releasing agent containing a silazane compound is particularly preferred, since the releasing agent has excellent releasability for preventing adhesion of the laminate film to a heating tool during mounting of semiconductor chips and does not induce melt adhesion by heat. Examples of such releasing agents containing a silazane compound include silicone series resin SEPA-COAT (trade name: product of Shin-Etsu Chemical Co., Ltd., containing silazane, synthetic isoparaffin, and ethyl acetate). 
   No particular limitation is imposed on the method for forming such a releasing layer, and any known method can be employed. For example, a releasing agent or a liquid thereof may be applied to a substrate through spraying, dipping, or roller-coating. Alternatively, a releasing layer provided on a transfer film may be transferred. In any case, bonding between the insulating layer and the releasing layer may be enhanced through, for example, heat treatment in order to prevent peeling of the releasing layer from the insulating layer. The releasing layer is not necessarily provided uniformly on the entire insulating layer, and may be provided in the form of discontinuous islands. For example, in case the releasing layer is provided by transferring, in case the releasing layer may be provided on only the region between two rows of sprocket holes, which will be described later, or on the region opposite to the region corresponding to the region where semiconductor chips (IC) are to be mounted in a continued form or in the form of discontinuous islands. No particular limitation is imposed on the timing of provision of the releasing layer, so long as the layer is provided prior to mounting of semiconductor elements. Specifically, the releasing layer may be provided after provision of the conductor layer; provided in advance on an insulating layer which has not been provided with a conductor layer; or provided simultaneously with provision of the conductor layer. Needless to say, the releasing layer is not necessarily provided prior to patterning of the conductor layer, but may be provided after patterning of the conductor layer. 
   The transfer method is preferably employed in the cases in which, for example, the releasing layer is provided after provision of the conductor layer or in advance on an insulating layer which has not been provided with a conductor layer. When the releasing layer is provided after patterning of the conductor layer, the application method is preferably employed. Needless to say, the timing of formation of the releasing layer is not limited, and the layer may be provided at an initial stage before patterning of the conductor layer through application or may be provided after patterning of the conductor layer through transfer. 
   In one embodiment of the production method of the present invention, the releasing layer is provided after the photolithographic process (patterning process) and before mounting of semiconductor elements. The reason for choosing the above timing is that the releasing layer is possibly dissolved by a photoresist remover or a similar material. Therefore, the releasing layer is preferably provided after etching of the conductor layer for removal of a resist mask for forming a wiring pattern. Specifically, the releasing layer is preferably provided, for example, after formation of a tin plating layer preceded by removal of a resist mask or after plating of a lead electrode preceded by removal of the resist mask and provision of a solder resist layer. Such a releasing layer may be formed by coating a solution containing a releasing agent and bringing the applied solution to dryness. However, in order to enhance bonding strength between the insulating layer and the releasing layer, the applied solution is preferably heated. The conditions under which the heating is performed are, for example, at 50 to 200° C., preferably 100 to 200° C. for one minute to 120 minutes, preferably 30 minutes to 120 minutes. 
   According to another embodiment of the method of the present invention, a releasing layer provided on a transfer film may be transferred on the surface of the insulating layer opposite to the side which the semiconductor chips (IC) are to be mounted. Exemplary conditions under which the transfer is performed are, but are not limited to, a heating temperature of 15 to 200° C., a load for rolling or pressing of 5 to 50 kg/cm 2 , and a treatment time of 0.1 seconds to two hours. Bonding between the insulating layer and the releasing layer may be enhanced through, for example, heat treatment in order to prevent peeling of the releasing layer from the insulating layer. Exemplary conditions under which the heating is performed are, but are not limited to, at 50 to 200° C., preferably 100 to 200° C., preferably for one minute to 120 minutes, preferably 30 minutes to 120 minutes. 
   According to the above transfer method, no particular limitation is imposed on the timing of provision of the releasing layer, so long as the layer is provided prior to mounting of semiconductor elements. Specifically, the releasing layer may be provided in advance on an insulating layer which has not been provided with a conductor layer; or provided simultaneously with provision of the conductor layer. Needless to say, the releasing layer is, not necessarily provided prior to patterning of the conductor layer, but may be provided after patterning of the conductor layer. 
   The transfer method is preferably employed in the cases in which, for example, the releasing layer is provided in advance on an insulating layer which has not been provided with a conductor layer. In the case in which the releasing layer is provided through the transfer method at an initial stage of production of the COF flexible printed wiring board, the following procedure may be employed. Specifically, the transfer film is not peeled from the releasing layer, so as to serve as a reinforcing film, and the transfer film is removed at a final production step. 
   Using this method in the present invention of the printed circuit board, a semiconductor is mounted on the COF flexible printed wiring board. No particular limitation is imposed on the mounting method. For example, semiconductor chips are mounted by positioning and disposing the COF flexible printed wiring board on semiconductor chips which are placed on a chip stage, and pressing a heating tool against the COF flexible printed wiring board. In this case, the heating tool is heated to at least 200° C., or in some cases, 350° C. or higher. However, since the COF flexible printed wiring board has a releasing layer formed on the insulating layer, melt adhesion between the heating tool and the insulating layer can be prevented. 
   Hereafter, one embodiment of the printed circuit board of the present invention, will be described with reference to  FIGS. 1A and 1B . The following embodiments of the present invention will be described taking a COF film carrier tape as an example. However, needless to say, those with ordinary skill in the art would readily understand that COF FPCs can also be realized in an analogous manner. 
   Hereafter, a COF film carrier tape  20  for producing a printed circuit board, according to one embodiment of the present invention, will be described with reference to an example. 
     FIGS. 2A and 2B  show a COF film carrier tape  20 ,  FIGS. 3A  to  3 G are cross-sectional views showing a method of producing of the COF film carrier tape  20 . 
     FIG. 1  is a cross-sectional view of a printed circuit board according to one embodiment of the present invention. As shown in  FIG. 1 , a COF film carrier tape  20  comprises a conductor layer  11  formed of copper foil, and an insulating layer  12  formed of polyimide film. The COF film carrier tape  20  has wiring patterns  21  obtained by patterning the conductor layer  11 , and a pair of transversely spaced rows of sprocket holes  22  provided along opposite longitudinal edges of the wiring patterns  21 . The wiring patterns  21  are provided on a surface of the insulating layer  12  continuously in the longitudinal direction of the film carrier tape  20 . The insulating layer  12  has, on the side opposite the side having wiring patterns  21  on which semiconductor chips are to be mounted, a releasing layer  13 . Each wiring pattern  21  has, on a surface thereof, a solder resist layer  23  which is formed by coating a solder resist coating solution through screen printing. A semiconductor chip  30  is mounted on each wiring pattern  21 , with an inner lead of the wiring pattern  21  being bonded with bumps  31  of the semiconductor chip  30 . 
   As shown in  FIGS. 2A ,  2 B, and  3 A to  3 G, the COF film carrier tape  20  according to the present embodiment is formed from a laminate film  10  for producing a COF, the laminate film comprising a conductor layer  11  (copper foil) and an insulating layer  12  (polyimide film). The COF film carrier tape  20  has wiring patterns  21  obtained by patterning the conductor layer  11 , and a pair of transversely spaced rows of sprocket holes  22  provided along opposite longitudinal edges; that is, the two rows of sprocket holes  22  are disposed such that one row extends along each of the opposite longitudinal edges of the wiring pattern  21 . The wiring patterns  21  are provided on a surface of the insulating layer  12  continuously in the longitudinal direction of the film carrier tape. Each wiring pattern  21  has, on a surface thereof, a solder resist layer  23  which is formed by coating a solder resist coating solution through screen printing. Moreover, the wiring pattern may be formed on two sides of the insulating layer (2-metal COF film carrier tape). In this case, the releasing layer may be formed on only the region where the heating tool is to contact, by coating or transferring. 
   Although the conductor layer  11  can be formed from a metal other than copper; e.g., aluminum, gold or silver, a copper layer is generally employed. No particular limitation is imposed on the type of copper layer, and any type of copper layers, such as a copper layer formed through vapor deposition or plating, electrolyzed copper foil, or rolled copper foil, can be used. Generally, the conductor layer  11  has a thickness of 1 to 70 μm, preferably 5 to 35 μm. 
   The insulating layer  12  may be formed from, other than polyimide, a polymeric material such as polyester, polyamide, polyether-sulfone, or liquid crystalline polymer. Of these, an aromatic polyimide (all repeating units being aromatic) prepared by polymerizing pyromellitic dianhydride and 4,4′-diaminodiphenyl ether is preferred. The thickness of the insulating layer  12  generally falls within a range of 12.5 to 125 μm, preferably 12.5 to 75 μm, more preferably 12.5 to 50 μm. 
   The laminate film  10  for producing a COF is produced by, for example, coating to a conductor layer  11  (copper foil) a polyimide precursor resin composition containing a polyimide precursor and varnish, to thereby form a coating layer  12   a ; removing the solvent by drying; winding the coating layer; and heating the wound coating layer in an oxygen-purged curing furnace for imidization, to thereby form the insulating layer  12 . However, no particular limitation is imposed on the method for producing the laminate film. 
   A releasing layer  13  can be formed from a silicone series releasing agent containing a silazane compound or a releasing agent containing silica sol. Preferably, the releasing layer  13  is formed by providing a releasing agent on the insulating layer  12  through, for example, the application method, followed by heating to thereby attain strong bonding between the releasing layer  13  and the insulating layer  12 . The releasing layer  13  has a thickness of, for example, 0.1 to 1 μm. 
   On the above-described COF film carrier tape of the present invention, chips or electronic devices are mounted. For example, while the tape or wiring board is conveyed, semiconductor chips are mounted on the tape, or electronic devices are mounted on a print wiring board, to thereby yield COF products. Since the insulating layer  12  has a optical transmittance of 50% or higher, the image of the wiring patterns  21  (e.g., an inner lead) can be recognized from the side of the insulating layer  12  by means of a CCD or a similar device. In addition, the wiring patterns of semiconductor chips and printed circuit boards to be mounted can be recognized. Thus, precise positioning of the wiring patterns with respect to the insulating layer  12  can be performed through image processing, thereby mounting electronic devices with high precision. 
   Next, one exemplary method of producing the aforementioned COF film carrier tape will be described with reference to  FIGS. 3A  to  3 G. 
   As shown in  FIG. 3A , a laminate film  10  for producing a COF is provided. As shown in  FIG. 3B , sprocket holes  22  are formed, by punching or a similar method, through a conductor layer  11  and an insulating layer  12 .These sprocket holes  22  may be formed from the front side or the backside of the insulating layer  12 . Then, as shown in  FIG. 3C , a photoresist coating layer  30  is formed on a region of the conductor layer  11  for providing a wiring pattern  21 , through a routine photolithographic method involving application of, for example, a negative type photoresist coating solution. Needless to say, a positive type photoresist can also be employed. After the insulating layer  12  is positioned by inserting positioning pins in the sprocket holes  22 , the photoresist coating layer  30  is exposed and developed via a photomask  31  for patterning thereof, thereby forming a resist pattern  32  for providing a wiring pattern as shown in FIG.  3 D. Subsequently, the conductor layer  11  is removed by dissolving with an etchant through the resist pattern  32  serving as a mask pattern, and the resist pattern  32  is removed by dissolving with an alkaline solution or a similar material, thereby forming a wiring pattern  21  as shown in FIG.  3 E. The entirety of the thus-formed wiring pattern  21  is plated (e.g., plated with tin) in accordance with needs, and then a releasing layer  13  is formed, through the application method, on the insulating layer  12 , as shown in FIG.  3 F. Although the applied releasing layer  13  may be simply dried, heating of the layer is preferred, for enhancing a releasing effect; i.e., for preventing melt adhesion of a heating tool and the insulating layer. Exemplary conditions under which the heating is performed are, but are not limited to, at 50 to 200° C., preferably 100 to 200° C. for one minute to 120 minutes, preferably  30  minutes to 120 minutes. Subsequently, a solder resist layer  23  is formed through, for example, screen printing, as shown in FIG.  3 G. An outer lead and an inner lead, which are not covered with the solder resist layer  23 , are plated with a metal in accordance with needs. No particular limitation is imposed on the material of the metal plating layer, and tin plating, tin alloy plating, nickel plating, gold plating, gold alloy plating, etc. may appropriately be performed in accordance with the purpose of use. 
   In the embodiment described above, the releasing layer  13  is formed after removal of the resist pattern  32  with an alkali solution or a similar material and before provision of the solder resist layer  23 . Alternatively, the releasing layer  13  may be formed in the final production step after provision of the solder resist layer  23 . When the releasing layer  13  is formed through the latter method, exposure of the releasing layer  13  to an etchant, a photoresist remover, etc. is prevented, thereby attaining a high releasing effect. As described hereinabove, the term “final production step” refers to as a step immediately before the product inspection step. 
   As described above, the releasing layer of the present invention is preferably formed after the photolithography step for forming wiring patterns  21  and before bonding with semiconductor chips. The reason for the timing is that the releasing layer is possibly dissolved in a photoresist layer removal step. Therefore, the releasing layer  13  is preferably formed immediately after completion of the photolithography step or after plating, more preferably after formation of the solder resist layer  23  or a similar step. Needless to say, the releasing layer  13  may also be formed before the photolithography step. 
   The releasing layer may be formed through the transfer method. Specifically, the aforementioned COF film carrier tape may be produced from a laminate film  10 A for producing a COF as shown in  FIGS. 4A  to  4 E. The laminate film shown in  FIGS. 4A  to  4 E is produced by coating to a conductor layer  11  (copper foil,  FIG. 4A ) a polyimide precursor resin composition containing a polyimide precursor and varnish, to thereby form a coating layer  12   a  (FIG.  4 B); removing the solvent by drying; winding the coating layer; and heating the wound coating layer in a curing furnace for imidization, to thereby form the insulating layer  12  (FIG.  4 C). Subsequently, a releasing layer  13   a  formed on a transfer film  14  serving as a transfer substrate is brought into firm contact with the surface of the insulating layer  12  opposite to the side of the conductor layer  11  ( FIG. 4D ) and heated. Then, the transfer film  14  is peeled, thereby forming the laminate film  10 A for producing a COF and having a releasing layer  13 A (FIG.  4 E). Exemplary conditions under which the transfer is performed are, but are not limited to, a heating temperature of 15 to 200° C., a load for rolling or pressing of 5 to 50 kg/cm 2 , and a treatment time of 0.1 seconds to two hours. Exemplary conditions under which the heating is performed are, but are not limited to, at 50 to 200° C., preferably 100 to 200° C. for one minute to 120 minutes, preferably 30 minutes to 120 minutes. Needless to say, formation of the releasing layer  13 A through transfer may be performed after the photolithography step or a similar step. Examples of the material of the transfer film  14  include PET (polyethylene terephthalate), PI (polyimide), and liquid crystal polymers. The thickness of such transfer film  14  is, for example, 15 to 100 μm, preferably 20 to 75 μm. 
   As shown in  FIG. 5 , the printed circuit board of the present invention is produced by mounting a semiconductor chip  30  on a COF film carrier tape  20  produced in the above-described manner. Specifically, the COF film carrier tape  20  is conveyed and then positioned at a predetermined position, while the semiconductor chip  30  is placed on a chip stage  41 . Subsequently, the COF film carrier tape  20  is fixed by means of upper dampers  42  and lower dampers  43 , with each upper clamper  42  descending while a corresponding lower clamper  43  ascending. A heating tool  45  is pressed against the thus-fixed COF film carrier tape  20  so as to heat the tape, and further descends, thereby pressing an inner lead of the film carrier tape  20  against a bump  31  of the semiconductor chip  30 . Pressing is performed for a predetermined period of time, thereby bonding the inner lead and the semiconductor chip  30 . After completion of bonding, the bonded chip is sealed with resin, to thereby produce a printed circuit board. 
   Depending on time and pressure of pressing or other conditions, the temperature of the heating tool  45  is controlled to 200° C. or higher, preferably 350° C. or higher. According to the present invention, even when the heating tool  45  is heated to such high temperature, melt adhesion between the COF film carrier tape  20  and the heating tool  45  is prevented by virtue of a releasing layer  13  provided on a surface of the film carrier tape  20  to be brought into contact with the heating tool  45 . Therefore, according to the present invention, bonding can be performed at sufficiently high temperature, thereby ensuring high bonding strength. In other words, since heating temperature can be elevated for attaining a predetermined level of bonding strength, the time required for press bonding can be shortened, which is advantageous. 
   EXAMPLES 
   Examples 1a to 1d 
   A variety of commercially available polyimide film substrates; i.e., S&#39;PERFLEX (trade name: product of Sumitomo Metal Mining Co., Ltd.; Example 1a), ESPANEX (trade name: product of Nippon Steel Chemical Co., Ltd.; Example 1b), NEOFLEX (trade name: product of Mitsui Chemicals, Inc.; Example 1c), and UPISEL (trade name: product of Ube Industries, Ltd.; Example 1d) were used to provide laminate films for producing a COF. A conductor layer of each laminate film was patterned by use of a photoresist. The entirety of the resultant pattern was tin-plated, and a silicone series resin (containing a silane compound), SR2411 (trade name: product of Dow Corning Toray Silicone Co., Ltd.), was applied to the backside of the film substrate. The coating was heated at 125° C. for one hour, to thereby form a COF film carrier tape having a releasing layer. 
   A heating tool was pressed against the releasing layer  13  of each of the COF film carrier tapes produced in Examples 1a to 1d. The temperature of the heating tool was varied within a range of 260° C. to 440° C. Under the heating conditions, semiconductor chips  30  were mounted and moulded, to thereby produce a printed circuit board. The temperature of the chip stage was maintained at 450° C. 
   Examples 2a to 2d 
   A variety of commercially available polyimide film substrates similar to those employed in Examples 1a to 1d; i.e., S&#39;PERFLEX (trade name: product of Sumitomo Metal Mining Co., Ltd.; Example 2a), ESPANEX (trade name: product of Nippon Steel Chemical Co., Ltd.; Example 2b), NEOFLEX (trade name: product of Mitsui Chemicals, Inc.; Example 2c), and UPISEL (trade name: product of Ube Industries, Ltd.; Example 2d) were used to provide laminate films for producing a COF. A conductor layer of each laminate film was patterned by use of a photoresist. The entirety of the resultant pattern was tin-plated, and a silicone series resin (containing silazane), SEPA-COAT (trade name: product of Shin-Etsu Chemical Co., Ltd.), was applied to the backside of the film substrate. The coating was heated at 125° C. for one hour, to thereby form a COF film carrier tape having a releasing layer. 
   A heating tool was pressed against the releasing layer  13  of each of the COF film carrier tapes produced in Examples 2a to 2d. The temperature of the heating tool was varied within a range of 260° C. to 440° C. Under the heating conditions, semiconductor chips  30  were mounted and moulded, to thereby produce a printed circuit board. The temperature of the chip stage was maintained at 450° C. Comparative Examples la to id and 2a to 2d 
   The procedure of Examples 1a to 1d and 2a to 2d were repeated, except that no releasing layer was provided, to thereby yield COF film carrier tapes of Comparative Examples 1a to 1d and 2a to 2d, respectively. 
   A heating tool was pressed against the releasing layer  13  of each of the COF film carrier tapes produced in Comparative Examples 1a to 1d and 2a to 2d. The temperature of the heating tool was varied within a range of 260° C. to 440° C. Under the heating conditions, semiconductor chips  30  were mounted and moulded, to thereby produce a printed circuit board. The temperature of the chip stage was maintained at 450° C. 
   Test Example 1 
   A heating tool was pressed against the releasing layer  13  of each of COF film carrier tapes produced in Examples 1a to 1d and 2a to 2d and Comparative Examples 1a to 1d and 2a to 2d. The temperature of the heating tool was varied within a range of 260° C. to 440° C. Under the heating conditions, semiconductor chips were mounted. Adhesion between the releasing layer and the heating tool was observed, and the temperature at which adhesion occurred was determined. The results are shown in Table 1. 
   
     
       
             
             
             
             
           
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
               TABLE 1 
             
           
           
             
                 
                 
             
             
                 
               Releasing 
               Film 
               Adhesion temperature (° C.) 
             
           
        
         
             
                 
               agent 
               substrate 
               Examples 
               Comp. Exs. 
             
             
                 
                 
             
           
        
         
             
               1a 
               SR2411 
               S′PERFLEX 
               370 
               320 
             
             
               1b 
               SR2411 
               ESPANEX 
               360 
               320 
             
             
               1c 
               SR2411 
               NEOFLEX 
               360 
               340 
             
             
               1d 
               SR2411 
               UPISEL 
               350 
               260 
             
             
               2a 
               SEPA-COAT 
               S′PERFLEX 
               440 
               320 
             
             
               2b 
               SEPA-COAT 
               ESPANEX 
               390 
               320 
             
             
               2c 
               SEPA-COAT 
               NEOFLEX 
               400 
               340 
             
             
               2d 
               SEPA-COAT 
               UPISEL 
               360 
               260 
             
             
                 
             
           
        
       
     
   
   As is clear from Table 1, the film carrier tapes of Examples 1a to 1d and 2a to 2d exhibit remarkably high adhesion resistance (i.e., high releasing effect), as compared with those of Comparative Examples 1a to 1d and 2a to 2d having no releasing layer  13 . 
   In addition, a moulding status of under-filling material (resin) was almost same regardless of the presence or absence of the releasing layer. 
   Examples 3a to 3d 
   A variety of commercially available polyimide film substrates similar to those employed in Examples 1a to 1d; i.e., S&#39;PERFLEX (trade name: product of Sumitomo Metal Mining Co., Ltd.; Example 3a), ESPANEX (trade name: product of Nippon Steel Chemical Co., Ltd.; Example 3b), NEOFLEX (trade name: product of Mitsui Chemicals, Inc.; Example 3c), and UPISEL (trade name: product of Ube Industries, Ltd.; Example 3d) were used to provide laminate films for producing a COF. A conductor layer of each laminate film was patterned by use of a photolithographic process, to thereby form a wiring pattern. The entirety of the wiring pattern was tin-plated, and subsequently a silicone series oil, SRX310 (trade name: product of Dow Corning Toray Silicone Co., Ltd.), was applied to the backside of the film substrate. The coating was heated at 125° C. for one hour, to thereby form a COF film carrier tape having a releasing layer. 
   A heating tool was pressed against the releasing layer  13  of each of the COF film carrier tapes produced in Examples 3a to 3d. The temperature of the heating tool was varied within a range of 260° C. to 400° C. Under the heating conditions, semiconductor chips  30  were mounted, to thereby produce a printed circuit board. The temperature of the chip stage was maintained at 450° C. 
   Comparative Examples 3a to 3d 
   The procedure of Examples 3a to 3d were repeated, except that no releasing layer was provided, to thereby yield COF film carrier tapes of Comparative Examples 3a to 3d, respectively. 
   A heating tool was pressed against the releasing layer  13  of each of the COF film carrier tapes produced in Comparative Examples 3a to 3d. The temperature of the heating tool was varied within a range of 260° C. to 400° C. Under the heating conditions, semiconductor chips  30  were mounted, to thereby produce a printed circuit board. The temperature of the chip stage was maintained at 450° C. 
   Test Example 2 
   A heating tool was pressed against the releasing layer  13  of each of COF film carrier tapes produced in Examples 3a to 3d and Comparative Examples 3a to 3d. The temperature of the heating tool was varied within a range of 260° C. to 400° C. Under the heating conditions, semiconductor chips were mounted. Adhesion between the releasing layer and the heating tool was observed, and the temperature at which adhesion occurred was determined. The results are shown in Table 2. 
   
     
       
             
             
             
           
             
             
             
           
             
             
             
             
           
         
             
                 
               TABLE 2 
             
           
           
             
                 
                 
             
             
                 
                Adhesion temprature (° C.) 
                 
             
           
        
         
             
                 
               Examples 
               Comp. Exs. 
             
             
                 
                 
             
           
        
         
             
                 
               3a: S′PERFLEX 
               400 
               320 
             
             
                 
               3b: ESPANEX 
               350 
               320 
             
             
                 
               3c: NEOFLEX 
               370 
               340 
             
             
                 
               3d: UPISEL 
               280 
               260 
             
             
                 
                 
             
           
        
       
     
   
   As is clear from Table 2, the film carrier tapes of Examples 3a to 3c exhibit remarkably high adhesion resistance as compared with those of Comparative Examples 3a to 3c. Although the film carrier tape of Example 3d exhibits an adhesion temperature higher than that of the film carrier tape of Comparative Example 3d, the difference in temperature was comparatively small. However, in view that the temperature at which semiconductor elements are mounted through melt adhesion varies depending on the type of heating tools, the type of semiconductor chips, use of the element-mounted products, etc., and is generally about 200° C. to about 350° C., such a small increase in adhesion temperature would suffice for purposes of the present invention. Examples 4a to 4h. 
   The procedure of Example la was repeated, except that the timing of application of SEPA-COAT (trade name: product of Shin-Etsu Chemical Co., Ltd.) was varied, to thereby produce COF film carrier tapes. Specifically, the releasing layer was obtained by coating SEPA-COAT to a laminate film for producing a COF, followed by air-drying for three hours or longer (Example 4a); by heating the applied SEPA-COAT at 125° C for one hour instead of air-drying (Example 4b); by coating SEPA-COAT at a cleaning step performed before patterning of the conductor layer, followed by air-drying for three hours or longer (Example 4c); by heating the thus-applied SEPA-COAT in 125° C. for one hour instead of air-drying (Example 4d); by coating SEPA-COAT after development of a photoresist for patterning the conductor layer, followed by air-drying for three hours or longer (Example 4e); by heating the thus-applied SEPA-COAT at 125° C. for one hour instead of air-drying (Example 4f); by coating SEPA-COAT after patterning of the conductor layer, removal of photoresist, and plating of tin, followed by air-drying for three hours or longer (Example 4g); or by heating the thus-applied SEPA-COAT at 125° C. for one hour instead of air-drying (Example 4h) 
   A heating tool was pressed against the releasing layer  13  of each of the COF film carrier tapes produced in Examples 4a to 4g. The temperature of the heating tool was varied within a range of 340° C. to 490° C. Under the heating conditions, semiconductor chips  30  were mounted, to thereby produce a printed circuit board. The temperature of the chip stage was maintained at 450° C. 
   Test Example 3 
   A heating tool was pressed against the releasing layer  13  of each of COF film carrier tapes produced in Examples 4a to 4h. The temperature of the heating tool was varied within a range of 340° C. to 490° C. Under the heating conditions, semiconductor chips were mounted. Adhesion between the releasing layer and the heating tool was observed, and the temperature at which adhesion occurred was determined. The results are shown in Table 3. 
   
     
       
             
             
           
             
             
             
           
         
             
                 
               TABLE 3 
             
             
                 
                 
             
             
                 
               Adhesion temperature (° C.) 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               Example 4a 
               350 
             
             
                 
               Example 4b 
               360 
             
             
                 
               Example 4c 
               350 
             
             
                 
               Example 4d 
               370 
             
             
                 
               Example 4e 
               340 
             
             
                 
               Example 4f 
               380 
             
             
                 
               Example 4g 
               480 
             
             
                 
               Example 4h 
               490 
             
             
                 
                 
             
           
        
       
     
   
   As is clear from Table 3, the film carrier tapes of Examples 4g and 4h, in which the releasing layer is formed after removal of photoresist, exhibit excellent adhesion resistance. A possible reason for excellent adhesion resistance is that the releasing layer is partially dissolved upon removal of photoresist performed after the photolithography step. As is also clear from the results, in the case in which the releasing layer is provided through the application method, adhesion resistance is further enhanced by heat treatment, as compared with air-drying without any additional heat treatment. 
   Examples 5a to 5e 
   In a manner similar to that for producing the film carrier tapes of Examples 4a to 4h, patterning of the conductor layer, removal of photoresist, plating with tin, and application of a silicone series resin were performed, to thereby produce film carrier tapes. Formation of the releasing layer was performed by air-drying three hours or longer or heating for one hour at 125° C. In Examples 5a to 5e, the silicone series resin, SEPA-COAT (trade name: product of Shin-Etsu Chemical Co., Ltd.), was diluted with ethyl acetate at a variety of dilution factors: i.e., 1 (undiluted), 2, 3, 5, and 10 times. In each case, the thickness of the releasing layer was calculated. 
   A heating tool was pressed against the releasing layer  13  of each of the COF film carrier tapes produced in Examples 5a to 5e. The temperature of the heating tool was varied within a range of 320° C. to 460° C. Under the heating conditions, semiconductor chips  30  were mounted, to thereby produce a printed circuit board. The temperature of the chip stage was maintained at 450° C. 
   Test Example 4 
   A heating tool was pressed against the releasing layer  13  of each of COF film carrier tapes produced in Examples 5a to 5e. The temperature of the heating tool was varied within a range of 320° C. to 460° C. Under the heating conditions, semiconductor chips were mounted. Adhesion between the releasing layer and the heating tool was observed, and the temperature at which adhesion occurred was determined. The results are shown in Table 4. 
   
     
       
             
             
             
             
           
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
               TABLE 4 
             
           
           
             
                 
                 
             
             
                 
                 
               Adhesion 
                 
             
             
                 
               Layer 
               temperature (° C.) 
             
           
        
         
             
                 
               thickness (μm) 
               Non-heated 
               Heated 
             
             
                 
                 
             
           
        
         
             
                 
               Example 5a 
               0.35 
               440 
               460 
             
             
                 
               Example 5b 
               0.18 
               440 
               440 
             
             
                 
               Example 5c 
               0.12 
               400 
               410 
             
             
                 
               Example 5d 
               0.07 
               370 
               390 
             
             
                 
               Example 5e 
               0.04 
               320 
               320 
             
             
                 
                 
             
           
        
       
     
   
   As is clear from Table 4, the film carrier tapes having a releasing layer thickness 0.05 μm or more exhibit adhesion resistance. As confirmed with Examples 5a to 5c, the film carrier tapes having a releasing layer thickness in excess of 0.1 μm exhibit remarkably high adhesion resistance. 
   Example 6 
   A polyimide layer (thickness: 40 μm) serving as an insulating layer  12  was formed through the application method on copper foil (thickness: 9 μm) of ultra-minute roughness serving as a conductor  11 . On the other surface (opposite to the conductor  11 ) of the copper foil, a releasing layer  13  (thickness: 0.1 μm) formed of a silicone series compound was provided through the transfer method, thereby yielding a COF film carrier tape of Example 6. After completion of transferring of the releasing layer  13  formed from the silicone series compound, the film carrier tape was heated at 120° C 
   A heating tool was pressed against the releasing layer  13  of the COF film carrier tape produced in Example 6. The temperature of the heating tool was varied within a range of 260° C. to 440° C. Under the heating conditions, semiconductor chips  30  were mounted, to thereby produce a printed circuit board. The temperature of the chip stage was maintained at 450° C. 
   Example 7 
   The procedure of Example 6 was repeated, except that heating treatment to be performed after transfer of the silicone series compound was omitted, to thereby yield a laminate film for producing a COF of Example 7. 
   A heating tool was pressed against the releasing layer  13  of the COF film carrier tape produced in Example 7. The temperature of the heating tool was varied within a range of 260° C. to 440° C. Under the heating conditions, semiconductor chips  30  were mounted, to thereby produce a printed circuit board. The temperature of the chip stage was maintained at 450° C. 
   Example 8 
   The procedure of Example 6 was repeated, except that the the releasing layer  13  formed through transfer method was changed to silicone series compound formed from SEPA-COAT (trade name: product of Shin-Etsu Chemical Co., Ltd.), to thereby yield a laminate film for producing a COF of Example 8. 
   A heating tool was pressed against the releasing layer  13  of the COF film carrier tape produced in Example 8. The temperature of the heating tool was varied within a range of 260° C. to 440° C. Under the heating conditions, semiconductor chips  30  were mounted, to thereby produce a printed circuit board. The temperature of the chip stage was maintained at 450° C 
   Comparative Example 4 
   The procedure of Example 6 was repeated, except that provision of the releasing layer  13  was omitted, to thereby yield a laminate film for producing a COF of Comparative Example 4. 
   A heating tool was pressed against the releasing layer  13  of the COF film carrier tape produced in Comparative Example 4. The temperature of the heating tool was varied within a range of 260° C. to 440° C. Under the heating conditions, semiconductor chips  30  were mounted, to thereby produce a printed circuit board. The temperature of the chip stage was maintained at 450° C. 
   Test Example 5 
   A heating tool was pressed against the releasing layer  13  of each film carrier tape in Examples 6 to 8 and Comparative Example 4. The temperature of the heating tool was varied within a range of 260° C. to 440° C. Under the heating conditions, semiconductor chips were mounted. Adhesion between the releasing layer and the heating tool was observed, and the temperature at which adhesion occurred was determined. The results are shown in Table 5. 
   
     
       
             
             
             
             
             
           
         
             
               TABLE 5 
             
             
                 
             
             
               Tool 
                 
                 
                 
                 
             
             
               temperature 
                 
                 
                 
               Comparative 
             
             
               (° C.) 
               Example 6 
               Example 7 
               Example 8 
               Example 4 
             
             
                 
             
           
           
             
               260 
               ◯ 
               ◯ 
               ◯ 
               ◯ 
             
             
               280 
               ◯ 
               ◯ 
               ◯ 
               ◯ 
             
             
               300 
               ◯ 
               ◯ 
               ◯ 
               X 
             
             
               320 
               ◯ 
               Δ 
               ◯ 
               X 
             
             
               340 
               ◯ 
               Δ 
               ◯ 
               X 
             
             
               360 
               ◯ 
               X 
               ◯ 
               X 
             
             
               380 
               ◯ 
               X 
               ◯ 
               X 
             
             
               400 
               ◯ 
               X 
               ◯ 
               X 
             
             
               420 
               X 
               X 
               ◯ 
               X 
             
             
               440 
               X 
               X 
               X 
               X 
             
             
                 
             
             
               ◯: no adhesion,  
             
             
               Δ: partially adhered,  
             
             
               X: adhered  
             
           
        
       
     
   
   As is clear from Table 5, the film carrier tape of Comparative Example 4 adheres to the heating tool when the temperature exceeds 300° C. The film carrier tape of Example 7 exhibits such an good adhesion resistance that the tape partially adheres to the heating tool when the temperature exceeds 320° C. The film carrier tapes of Examples 6 and 8 cause no adhesion when the temperature is 400° C. or lower. Although the film carrier tape of Example 7 exhibits an adhesion temperature higher than that of the film carrier tape of Comparative Example 4, the difference in temperature was comparatively small. However, in view that the temperature at which semiconductor elements are mounted through melt adhesion varies depending on the type of heating tools, the type of semiconductor chips, use of the element-mounted products, etc., and is generally about 200° C. to about 350° C., such a small increase in adhesion temperature would suffice for purposes of the present invention. 
   Examples 9a to 9c 
   S&#39;PERFLEX (trade name: product of Sumitomo Metal Mining Co., Ltd.) was employed as a film substrate, and, as a releasing agent, COLCOAT P (trade name: product of Colcoat Co., Ltd., silica sol-containing; Example 9a); COLCOAT N-103X (trade name: product of Colcoat Co., Ltd.; Example 9b); and COLCOAT SP-2014S (trade name: product of Colcoat Co., Ltd., containing silane compound; Example 9c) were used. The entirety of the provided wiring pattern was tin-plated, and subsequently, each releasing agent was applied to the backside of the film substrate. The coating was dried by heating at 120° C. for 60 minutes, to thereby form a COF film carrier tape having a releasing layer. 
   A heating tool was pressed against the releasing layer  13  of each of the COF film carrier tapes produced in Examples 9a to 9c. The temperature of the heating tool was varied within a range of 440° C. to 480° C. Under the heating conditions, semiconductor chips  30  were mounted, to thereby produce a printed circuit board. The temperature of the chip stage was maintained at 450° C. 
   Test Example 6 
   A heating tool was pressed against the releasing layer  13  of each of COF film carrier tapes produced in Examples 9a to 9c. The temperature of the heating tool was varied within a range of 440° C. to 480° C. Under the heating conditions, semiconductor chips were mounted, to thereby produce a printed circuit board. 
   During production of printed circuit boards of Examples 9a to 9c, adhesion between the releasing layer and the heating tool was observed, and the temperature at which adhesion occurred was determined. The results are shown in Table 6. 
   
     
       
             
             
             
           
         
             
                 
               TABLE 6 
             
             
                 
                 
             
             
                 
               Examples 
               Adhesion temperature (° C.) 
             
             
                 
                 
             
           
           
             
                 
               9a: COLCOAT P 
               460 
             
             
                 
               9b: COLCOAT N-103X 
               480 
             
             
                 
               9c: COLCOAT SP-2014S 
               440 
             
             
                 
                 
             
           
        
       
     
   
   As is clear from Table 6, the film carrier tapes of Examples 9a to 9c also exhibit remarkably high adhesion resistance. 
   Test Example 10 
   On each of the COF film carrier tapes which had been produced in Examples 2a, 8, and 9a, a semiconductor chip was mounted by use of a heating tool heated at 400° C., to thereby yield a printed circuit board. Separately, on the COF film carrier tape which had been produced in Comparative Example 2a, a semiconductor chip was mounted by use of a heating tool heated at 280° C., to thereby yield a printed circuit board. The surface, which had been contacted with the heating tool, of the insulating layer of each of the printed circuit boards was observed by means of an Auger electron spectrometer (SAM). Through observation, Si contained in the releasing agent was detected in a continued form or in the form of discontinuous islands at least in a portion of the surface of the insulating layer of each of the printed circuit boards of Examples 2a, 8, and 9a, which portion being opposite to the region defined as the semiconductor chip is orthogonally projected onto the layer. However, no Si was detected on the surface of the insulating layer of the printed circuit board of Comparative Example 2a. Note that, since a Si compound contained in an insulating layer would be observed as a mass-like image rather than an island-like image, the Si compound can be distinguished from the Si components present on the surface of the insulating layer.