Patent Publication Number: US-2011059304-A1

Title: Dry film and manufacturing method of dry film

Description:
This application is based upon and claims the benefit of priority from Japanese patent application No. 2009-207073, filed on Sep. 8, 2009, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a solder resist, and in particular, a dry film solder resist. 
     2. Description of Related Art 
     A wiring board is provided with a solder resist film formed at a surface thereof to protect a wiring pattern from an external influence such as dusts and humidity and to prevent a solder from being in contact with an unnecessary part to cause a short circuit. A technique relating to a solder resist film is disclosed in Japanese patent publication (JP-P2005-331932A). 
     In a semiconductor device, a semiconductor element, a semiconductor package or the like is mounted on a surface of a wiring board protected with a solder resist. A manufacturing process of the semiconductor device includes a resin sealing process to protect the semiconductor element from external environment. The resin sealing process includes steps of: enclosing the wiring board on which the semiconductor element is mounted with dies; filling a cavity of the dies with sealing resin fluidized at a high temperature; curing the filled sealing resin; and taking out the semiconductor device (semiconductor package) including the cured resin from the dies. 
     A technique relating to the step of taking out the semiconductor device from dies is disclosed in Japanese patent publication (JP-P2002-166449A). A resin molding apparatus disclosed in Japanese patent publication (JP-P2002-166449A), after resin is filled in a cavity and molded, dies are opened while removing a molded product from the cavity by protruding ejector pins. The resin molding apparatus is provided with a suction device which sucks air to fix the molded product on a parting surface of the die when the dies are opened. According to such resin molding apparatus, an automatic resin molding process can be smoothly performed. 
     As described above, the wiring board is provided with the insulating solder resist film at the surface thereof. The solder resist film is formed for protecting the wiring board. Furthermore, the solder resist film can withstand a strain due to thermal deformation. In particular, when the solder resist film is positioned at a junction between the wiring board and the semiconductor element, the solder resist film is required to withstand a strain due to thermal deformation of the wiring board and the semiconductor element in the resin sealing process. Therefore, the solder resist film includes elastomer to relieve an internal stress. 
     The present inventor has recognized as follows with respect to the step of taking out the semiconductor device from the dies. In addition to a difficulty in a removal (release) of the molded resin from the dies, the elastomer included in the solder resist film tends to be adhered to the die since the elastomer is softened by heat in the resin sealing process, which makes it difficult to taking out the molded semiconductor device from the dies. 
     SUMMARY 
     In one embodiment, a dry film includes a first solder resist film, a second solder resist film and a supporting film. The first solder resist film includes first particles of first elastomer. The supporting film supports the first solder resist film and the second solder resist film. Adhesion strength of a surface of the second solder resist film is weaker than adhesion strength of a surface of the first solder resist film at a glass transition point of the first elastomer. 
     In another embodiment, a manufacturing method of a dry film includes: forming one of a first solder resist film and a second solder resist film on a supporting film; and farming another of the first solder resist film and the second solder resist film on or above one of the first solder resist film and the solder resist film. The first solder resist film includes first particles of first elastomer. Adhesion strength of a surface of the second solder resist film is weaker than adhesion strength of a surface of the first solder resist film at a glass transition point of the first elastomer. 
     The dry film can be bonded to an insulating layer and a wiring layer formed thereon such that the first solder resist film is arranged between the insulating layer and the second solder resist film, in order to farm a wiring board including the insulating layer, the wiring layer, the first solder resist film and the second solder resist film. Accordingly, the second solder resist film is arranged at a surface of the wiring board. Here, the adhesion strength of the surface of the second solder resist film is weaker than the adhesion strength of the surface of the first solder resist film at the glass transition point of the first elastomer. 
     According to the dry film, it is possible to form a wiring board including a solder resist film which is arranged at a surface of the wiring board and hard to be adhered to a body such as a die upon heating. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, advantages and features of the present invention will be more apparent from the following description of certain preferred embodiments taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a sectional view of a dry film  1  according to a first embodiment of the present invention; 
         FIG. 2  is a partial sectional view of a wiring board  50  including a solder resist film  20 A and a solder resist film  30 A formed by curing a solder resist film  20  and a solder resist film  30  based on a resist pattern; 
         FIG. 3  is an enlarged view of a portion in a circle A shown in  FIG. 2 ; 
         FIG. 4  is a sectional view of a semiconductor device  100  including the wiring board  50 ; 
         FIG. 5  is a sectional view illustrating a resin sealing process to cover a semiconductor element  60  with sealing resin  70  in a manufacturing process of the semiconductor device  100  shown in  FIG. 4 ; 
         FIG. 6  is a partial enlarged view of a section showing that the wiring board  50  and a die  110  are in contact with each other in the resin sealing process illustrated in  FIG. 5 ; 
         FIG. 7  is a flow chart illustrating a manufacturing method of the dry film  1  according to the first embodiment of the present invention; 
         FIG. 8  is a flow chart illustrating a manufacturing method of the wiring board  50 ; 
         FIG. 9  is a partial sectional view showing a dry film  1  according to a second embodiment of the present invention; 
         FIG. 10  is a partial sectional view of a wiring board  50  having a solder resist film  20 A and a solder resist film  35 A at the surface thereof, which are formed by respectively curing a solder resist film  20  and a solder resist film  35 ; 
         FIG. 11  is a sectional view showing that the wiring board  50  shown in  FIG. 10  is in contact with the die  110  in the resin sealing process; 
         FIG. 12  is a sectional view showing a dry film  1  according to a third embodiment of the present invention; 
         FIG. 13  is a partial sectional view of a wiring board  50  having a solder resist film  20 A, a solder resist film  35 A and a solder resist film  37 A at the surface thereof, which are formed by respectively curing a solder resist film  20 , a solder resist film  35 , and a solder resist film  37 ; 
         FIG. 14  is a flow chart illustrating a manufacturing method of the dry film  1  according to the third embodiment of the present invention; and 
         FIG. 15  is a partial sectional view showing a dry film  1  according to a fourth embodiment of the present invention. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The invention will be now described herein with reference to illustrative embodiments. Those skilled in the art will recognize that many alternative embodiments can be accomplished using the teachings of the present invention and that the invention is not limited to the embodiments illustrated for explanatory purposes. 
     Dry films according to embodiments of the present invention will be described below with reference to the accompanying drawings. 
     First Embodiment 
     A first embodiment of the present invention is described below.  FIG. 1  is a sectional view of a dry film  1  according to the present embodiment. Referring to  FIG. 1 , the dry film  1  includes a supporting film  10 , a solder resist film  20 , a second solder resist film  30  and a protection film  40 . 
     The supporting film  10  is a base material on which the solder resist film  20 , the solder resist film  30  and the protection film  40  are formed. The supporting film  10  prevents deformations of the solder resist film  20 , the solder resist film  30  and the protection film  40 . A known material which can support the solder resist film can be used to form the supporting film  10 . For example, in addition to polyester such as PET (polyethylene terephthalate) and PEN (polyethylene naphthalate), polypropylene and polyethylene can be used. 
     The solder resist film  20  and the solder resist film  30  are insulating films formed on the supporting film  10 . Specifically, the solder resist film  30  is formed on the supporting film  10 , and the solder resist film  20  is formed on the solder resist film  30 . The solder resist film  20  has surfaces  20   a  and  20   b  opposite to each other. The solder resist film  30  has surfaces  30   a  and  30   b  opposite to each other. The surface  20   a  is adhered to the protection film  40 . The surface  20   b  is bonded to the surface  30   a . The surface  30   b  is adhered to the supporting film  10 . Adhesion strength of the surface  30   b  of the solder resist film  30  is weaker than adhesion strength of the surface  20   b  of the solder resist film  20 . Therefore, when the solder resist film  20  and the solder resist film  30  are bonded to another member by using the dry film  1  such that the solder resist film  30  is arranged outside, a solder resist layer having weak adhesion strength is formed on a surface of the other member. When the solder resist film  20  and the solder resist film  30  are bonded to the other member, the surface  20   a  is bonded to the other member. Namely, the surface  20   a  functions as a bonding surface of the dry film  10 . Each of the solder resist film  20  and the solder resist film  30  includes resin such as a photosensitive resin known as solder resist. Therefore, the solder resist film  20  and the solder resist film  30  are formed by coating solder resist materials including such resin on the supporting film  10  and by drying the coated materials. The solder resist film  20  and the solder resist film  30  will be cured by a step of irradiating light such as ultraviolet rays, a step of heating, or the like. 
     The solder resist film  20  includes first elastomer  21 , The first elastomer  21  can relieve an internal stress of the solder resist film  20 . Any known elastomer which can relieve the internal stress of the solder resist film  20  is user as the first elastomer  21 . Details of the solder resist film  20 , the solder resist film  30  and the first elastomer  21  will be described later. 
     The protection film  40  is formed on the solder resist film  20  to protect the solder resist film  20 . The protection film  40  can prevent the solder resist film  20  from being bonded to the supporting film  10  when the dry film  1  is rolled up. The protection film  40  is formed by polyolefin such as PE (polyethylene) and PP (polypropylene), polyester, or the like. 
     By using the dry film  1 , it is easy to bond the solder resist film  20  and the solder resist film  30  to surfaces of a wiring board. The bonded solder resist film  20  and the solder resist film  30  are cured based on resist patterns to protect the wiring board.  FIG. 2  is a partial sectional view of a wiring board  50  including solder resist films  20 A and  30 A as the solder resist films  20  and  30  cured based on a resist pattern, and solder resist films  20 B and  30 B as the solder resist films  20  and  30  cured based on a resist pattern. Referring to  FIG. 2 , the solder resist film  20 A,  20 B,  30 A and  30 B are described in details. 
     Referring to  FIG. 2 , the wiring board  50  includes an insulating layer  51  having surfaces  51   a  and  51   b  opposite to each other, a wiring layer  52   a  formed on the surface  51   a , a wiring layer  52   b  formed on the surface  51   b , the solder resist film  20 A formed on the surface  51   a  and the wiring layer  52   a , the solder resist film  30 A formed on the solder resist film  20 A, the solder resist film  20 B formed on the surface  51   b  and the wiring layer  52   b , and the solder resist film  30 B formed on the solder resist film  20 B. The insulating layer  51  and the wiring layers  52   a  and  52   b  may be referred to as a core of the wiring board  50 . The surfaces of the wiring board  50  are protected by the solder resist films  20 A,  30 A,  20 B and  30 B. 
     The insulating layer  51  is a base material on which the wiring layers  52   a  and  52   b  are formed and prevents electrical conduction between the wiring layers  52   a  and  52   b . The insulating layer  51  is, for example, a glass epoxy board, a glass composite board or the like. Another wiring layer (not shown) other than the wiring layers  52   a  and  52   b  may be formed in the insulating layer  51 . Moreover, a through hole may be formed in the insulating layer  51  to connect between a predetermined wiring line in the wiring layer  52   a  and a predetermined wiring line in the wiring layer  52   b.    
     The wiring layer  52   a  is a group of conductive wiring lines formed in a predetermined pattern on the surface  51   a  of the insulating layer  51 . The wiring layer  52   b  is a group of conductive wiring lines formed in a predetermined pattern on the surface  51   b  of the insulating layer  51 . Each of the wiring layers  52   a  and  52   b  has a thickness of 10 to 35 μm, for example. 
     Referring to  FIG. 2 , the solder resist films  20 A and  20 B are provided inside the wiring board  50  and the solder resist films  30 A and  30 B are provided at the surfaces of (i.e., outside) the wiring board  50 . That is, after the protection film  40  of the dry film  1  is removed, the surface  20   a  of the solder resist film  20  is bonded to the surface  51   a  and the wiring layer  52   a , and the surface  20   a  of the solder resist film  20  is bonded to the surface  51   b  and the wiring layer  52   b . Opening portions are formed in the solder resist film  20 A and  30 A such that portions of wiring layer  52   a  are exposed to form electrode pads (not shown). Wires for wire bonding or solder balls for flip-chip bonding are connected to the electrode pads. Opening portions are formed in the solder resist film  20 B and  30 A such that portions of wiring layer  52   b  are exposed to form electrode pads (not shown) on which solder balls as external terminals are provided. 
     Note that the wiring board  50  may be a multilayer wiring board in which one or more wiring layers are provided in the insulating layer  51 . Also, the wiring board  50  may not include the wiring layer  52   b  and the solder resist films  20 B and  30 B. 
     Film thicknesses of the solder resist films  20 A and  20 B are described below. The solder resist films  20 A and  20 B cover and protect the wiring layers  52   a  and  52   b , respectively. Further, since each of the solder resist films  20 A and  20 B has insulating properties, short circuits among wiring lines in the wiring layer  52   a  and short circuits among wiring lines in the wiring layer  52   b  are prevented. Therefore, a lower limit of the film thickness of the solder resist film  20 A is a smallest film thickness required to cover the wiring layer  52   a , and an upper limit of the film thickness of the solder resist film  20 A is a largest film thickness which can prevent crack due to a strain in manufacturing and usage of a product including the wiring board  50 . Lower and upper limits of the film thickness of the solder resist film  203  are similar to those of the solder resist film  20 A. The film thickness of each of the solder resist films  20 A and  20 B is, for example, 25 to 70 μm. The solder resist film  20  shown in  FIG. 1  is formed to secure the above film thicknesses of the solder resist films  20 A and  203  in consideration of change in film thickness due to volatilization of solvent included in the solder resist film  20  and contraction in the curing. 
     Next, the first elastomer  21  included in the solder resist film  20 A and  20 B to relieve internal stress are described in detail below.  FIG. 3  is an enlarged view of a portion in a circle A shown in  FIG. 2 . Referring to  FIG. 3 , the first elastomer  21  is polymer dispersed in solder resist film  20 A as particles having mean diameter of 5 to 15 μm. The first elastomer  21  has a glass transition point equal to or lower than 150 degree Celsius and is softened to present adhesiveness at a temperature equal to or higher than the glass transition point. The necessity to relieve the internal stress by the first elastomer  21  is described below. 
       FIG. 4  is a sectional view of a semiconductor device  100  including the wiring board  50 . Referring to  FIG. 4 , the semiconductor device  100  includes the wiring board  50 , a semiconductor element  60  and a sealing resin  70 . 
     The semiconductor element  60  is provided with wiring patterns for implementing various kinds of functions and is connected to the wiring board  50 . The semiconductor element  60  is connected to the wiring board  50  by either of wire bonding or flip-chip bonding. The sealing resin  70  covers and protects the semiconductor element  60 . 
       FIG. 5  is a sectional view showing a resin sealing process included in a manufacturing process of the semiconductor device  100  shown in  FIG. 4 . In the resin sealing process, the semiconductor element  60  is covered with the sealing resin  70 . The resin sealing process is described referring to  FIG. 5 . Dies  110  and  120  covers and encloses the wiring board  50  mounting the semiconductor element  60  to form a cavity in which the sealing resin  70  is filled. The sealing resin  70  in a state of a high temperature fluid is filled in the cavity formed by the dies  110  and  120 . It is noted here that when filled in the cavity, the sealing resin  70  is not necessarily to be in liquid state but may be in a state of having fluidity (rubbery state). The following describes the case of liquid state. The die  110 , the die  120 , the wiring board  50  and the semiconductor element  60  are heated to approximately 150 to 200 degree Celsius to fully cure the sealing resin  70  in a fluid state. The sealing resin  70  in the fluid state is cured by heating. Since the solder resist film  20 A has a portion positioned between the wiring board  50  and the semiconductor element  60 , the solder resist film  20 A is required to withstand a strain due to thermal deformations of the wiring board  50  and the semiconductor element  60  in the resin sealing process. The first elastomer  21  relieves an internal stress due to the strain and prevents the solder resist film  20 A from being cracked and being detached from the insulating layer  51 . 
     However, since the first elastomer  21  is softened at a temperature equal to or higher than the glass transition point, the first elastomer  21  is easily adhered to other member. Therefore, when the first elastomer  21  were exposed at the surfaces of the wiring board  50 , there arises a problem that it is difficult to remove the wiring board  50  from the dies  110  and  120  in the resin sealing process. In the wiring board  50  manufactured by using the dry film  1  according to the present embodiment, the solder resist film  30 A and  30 B prevent the first elastomer  21  exposed on the surfaces of the solder resist films  20 A and  20 B from being in contact with the dies  110  and  120 . 
     Film thicknesses of the solder resist films  30 A and  30 B are described. Referring to  FIG. 2 , the cured solder resist films  30 A and  30 B for protecting the wiring board  50  are insulating films which cover the solder resist films  20 A and  20 B and are arranged at the surfaces of the wiring board  50 . A solder resist pattern is formed in the solder resist films  20 A and  30 A such that the wiring layer  52   a  is partially exposed. A solder resist pattern is formed in the solder resist films  20 B and  30 B such that the wiring layer  52   b  is partially exposed. Electrode pads are formed at the exposed portions of the wiring layers  52   a  and  52   b . The cured solder resist films  30 A and  30 B at the surfaces of the wiring board  50  prevents any portion other than the electrode pads from being electrically connected. 
     The solder resist film  30  of the dry film  1  does not include the first elastomer  21 . Since the solder resist film  30  does not include the first elastomer  21 , adhesion strength of the surface  30   b  of the solder resist film  30  is weaker than that of the surface  20   b  of the solder resist film  20  at the glass transition point of the first elastomer  21 . This similarly applies to the cured solder resist films  30 A and  30 B at the surface of the wiring board  50 , Therefore, in the resin sealing process shown in  FIG. 5 , each of the cured solder resist films  30 A and  305  at the surfaces of the wiring board  50  has weak adhesion strength to the die  110  or  120 . Moreover, the resin included in the solder resist films  30 A and  30 B is hard to be adhered to the dies  110  and  120  due to a heat in the resin sealing process. Therefore, even when heated to a temperature equal to or more than the glass transition point of the first elastomer  21  in the resin sealing process, the solder resist films  30 A and  30 B are hard to be adhered to the dies  110  and  120 . It is preferable that the composition of the solder resist films  30 A and  30 B is the same as that of the solder resist films  20 A and  20 B except for the first elastomer  21 . In particular, it is preferable that resin components of each of the solder resist films  30 A and  30 B are same as resin components of each of the solder resist films  20 A and  208 , since the solder resist film  30 A (or  30 B) is strongly bonded to the solder resist film  20 A ( 20 B) in this case. It is noted here that the resin components of the solder resist film indicate a base material of the solder resist film and do not include elastomer. 
     Film thicknesses of the solder resist films  30 A and  30 B are described below referring to  FIG. 3 . A lower limit of the film thickness of the solder resist film  30 A is a smallest film thickness required to cover the first elastomer  21  exposed on the surface of the solder resist film  20 A, and an upper limit of the film thickness of the solder resist film  30 A is a largest film thickness which can prevent crack due to a strain in manufacturing and usage of a product including the wiring board  50 . Lower and upper limits of the film thickness of the solder resist film  30 B are similar to those of the solder resist film  30 A. That is, the cured solder resist films  30 A and  30 B at the surfaces of the wiring board  50  prevents the first elastomer  21  exposed on the surfaces of the solder resist films  20 A and  20 B from being exposed on the surfaces of the wiring board  50  so as to prevent the first elastomer  21  from being adhered to the dies  110  and  120  in the resin sealing process, respectively. The film thickness of each of the solder resist films  30 A and  30 B is, for example, 1 to 10 μm, more preferably, 1 to 2 μm. That is, the solder resist film  30  shown in  FIG. 1  is formed to secure the above film thicknesses of the solder resist films  30 A and  30 B in consideration of change in film thickness due to volatilization of solvent included in the solder resist film  30  and contraction in the curing. 
       FIG. 6  is a partial enlarged view of a section showing that the wiring board  50  and the die  110  are in contact with each other in the resin sealing process illustrated in  FIG. 5 . Referring to  FIG. 6 , since the cured solder resist film  30 A does not include the first elastomer  21 , which is softened by heating to be adhered to the die  110 , the solder resist film  30 A can be easily detached from die  110 . Although not shown in  FIG. 6 , the solder resist film  30 B can be easily detached from the die  120 , similarly. Therefore, when the solder resist films  20 A and  20 B and the solder resist films  30 A and  30 B are formed at the surfaces of the wiring board  50  using the dry film  1  according to the first embodiment of the present invention, since the solder resist films  30 A and  30 B can be easily detached from the dies  110  and  120 , a manufacturing throughput of the semiconductor device  100  can be improved. Note that each of the solder resist films  30 A and  30 B may include no elastomer at all, or may include elastomer which is harder to be softened by heating than the first elastomer  21 . 
       FIG. 7  is a flow chart showing a manufacturing method of the dry film  1  according to the first embodiment of the present invention. Referring to  FIG. 7 , the manufacturing method of the dry film  1  according to the first embodiment of the present invention is described. 
     Second solder resist material is coated on the supporting film  10  (Step S 01 ). A spray method, a screen printing method, a roller coating method or a curtain coating method is used as a coating method of the second solder resist material, for example. 
     The solder resist film  30  is formed by drying the coated second solder resist material through a heat treatment (Step S 02 ). The heat treatment is performed for 1 to 30 minutes in a temperature range of 60 to 100 degree Celsius, for example. The solder resist film  30  is formed to have a film thickness of 1 to 10 μm, preferably 1 to 2 μm after being cured. 
     First solder resist material including the first elastomer  21  is coated on the solder resist film  30  (Step S 03 ). A coating method of the first solder resist material is similar to that of the second solder resist material. 
     The solder resist film  20  is formed by drying the coated first solder resist material through a heat treatment (Step S 04 ). The heat treatment is performed for 1 to 30 minutes in a temperature range of 60 to 100 degree Celsius. The solder resist film  20  is formed to have a film thickness of 25 to 70 μm after the solder resist  20  is cured. The film thickness of the solder resist film  30  is smaller than the film thickness of the solder resist film  30 . 
     The protection film  40  is adhered onto the solder resist film  20  (Step S 05 ). 
       FIG. 8  is a flow chart illustrating a manufacturing method of the wiring board  50 . Referring to  FIG. 8 , the manufacturing method of the wiring board  50  using the dry film  1  according to the present embodiment is described. 
     The wiring layers  52   a  and  52   b  are formed on the surfaces  51   a  and  51   b  of the insulating layer  51  having insulating properties, respectively (Step S 10 ). The insulating layer  51  is a glass epoxy board, a glass composite board or the like, A known wiring pattern forming method such as etching can be used for forming the wiring layers  52   a  and  52   b.    
     The protection film  40  is removed from the dry film  1  such that the solder resist film  20  is exposed at the surface of the dry film  1 . The dry film  1  including the solder resist film  20 , the solder resist film  30  and the supporting film  10  is bonded to the surface  51   a  of the insulating layer  51  and the wiring layer  52   a  to cover the surface  31   a  and the wiring layer  52   a , and is bonded to the surface  51   b  of the insulating layer  51  and the wiring layer  52   b  to cover the surface  51   b  and the wiring layer  52   b  (Step S 11 ). Here, the dry film  1  is bonded to the core of the wiring board  50  such that the solder resist film  20  is in contact with the core of the wiring board  50 . A known method such as a thermo-compression bonding may be used for the bonding of the dry film  1 . For example, a pressure is applied on the supporting film  10  of the dry film  1  toward the insulating layer  51  to effectively perform the bonding. 
     The dry film  1  is exposed to irradiation of light such as ultraviolet rays through a mask based on a resist pattern (Step S 12 ). A laser beam may be used in place of the light through the mask. The solder resist film  20  and the solder resist film  30  may be either a negative type in which solubility to a developing solution is lowered upon exposure and the exposed portions remain after development or a positive type in which a solubility to a developing solution is increased upon exposure and exposed portions are removed. 
     The supporting film  10  is removed from the solder resist film  30  (Step S 13 ). 
     Unnecessary portions of the exposed solder resist films  20  and  30  are removed with a developing solution (Step S 14 ). 
     The solder resist films  20  and  30  are cured by any one or both of heating and irradiation of ultraviolet rays (Step S 15 ). The solder resist films  20  and  30  are heated for 30 to 60 minutes in a temperature range of 100 to 200 degree Celsius, for example. The cured solder resist film  20  is referred to as the solder resist film  20 A or  20 B, and the cured solder resist film  30  is referred to as the solder resist film  30 A or  30 B. 
     The dry film  1  according to the first embodiment of the present invention includes the solder resist film  20  which includes the first elastomer  21  that is softened by heating and the solder resist film  30  which does not include the first elastomer. By using the dry film  1 , the solder resist film  30 A or  30 B which does not include the first elastomer  21  can be easily formed at the surfaces of the wiring board  50 . Therefore, since the surfaces of the wiring board  50  manufactured using the dry film  1  according to the present embodiment do not present adhesiveness even when heated, the wiring board  50  is hard to be adhered to the dies  110  and  120 . In other words, the dry film  1  can facilitate the semiconductor device  100  to be easily taken out from the dies  110  and  120  after heating in the resin sealing process of the semiconductor device  100  in which the wiring board  50  is used. Therefore, it takes less time for a step of detaching the wiring board  50  from the dies  110  and  120  and for a step of cleaning the dies  110  and  120 , whereby the manufacturing throughput of the semiconductor device  100  can be improved. Moreover, by using the dry film  1 , contaminants are hard to adhere to the dies  110  and  120 . Accordingly, the contaminants are prevented from being transferred to the wiring board  50 , thereby preventing an assembly deficiency that the wiring board  50  and a solder ball are not bonded each other. In particular, the dry film  1  can prevent a poor connection between the electrode pad at the opening portion and a bonding wire or between the electrode pad and a solder ball when the bonding wire or the solder ball is electrically connected with the electrode pad. Further, since the wiring board  50  manufactured by using the dry film  1  is easily detached from the dies  110  and  120 , electrostatic discharge is prevented when the semiconductor device  100  is detached from the dies  110  and  120 , thereby preventing a malfunction of the semiconductor device  100  for semiconductor element  60 ). 
     Second Embodiment 
     A second embodiment of the present invention is described. A dry film  1  according to the second embodiment of the present invention is different from the dry film  1  according to the first embodiment in the configuration of the solder resist film  30 . Since the other configurations are the same as those of the first embodiment, the same components are denoted by the same reference symbols and the explanations thereof are omitted.  FIG. 9  is a partial sectional view showing the dry film  1  according to the second embodiment of the present invention. 
     Referring to  FIG. 9 , the dry film  1  includes the supporting film  10 , the solder resist film  20 , a solder resist film  35  and the protection film  40 . The supporting film  10 , the solder resist film  20  and the protection film  40  are the same as those of the first embodiment. 
     The solder resist film  35  includes second elastomer  36 . Similarly to the first elastomer  21 , the second elastomer  36  is polymer dispersed as particles in the solder resist film  35  to relieve an internal stress. The second elastomer  36  has a glass transition point equal to or lower than a temperature for curing the sealing resin  70  (e.g., 150° C. or lower) and is softened to present adhesiveness at a temperature equal to or higher than the glass transition point. Known compositions are used as compositions of a base material of the solder resist film  35  and the second elastomer  36 , and it is preferred that the compositions of the base material of the solder resist film  35  and the second elastomer  36  are same as those of the base material of the solder resist film  20  and the first elastomer  21 . 
     Similarly to the solder resist film  30 , the solder resist film  35  is cured at the surface of the wiring board  50  to protect the wiring board  50 . Although the cured solder resist film  35  includes the second elastomer  36  which is softened by heating to present adhesiveness, the cured solder resist film  35  is harder to be adhered to each of the dies  110  and  120  than the solder resist films  20 A and  20 B in the resin sealing process shown in  FIG. 5 . That is, adhesion strength of a surface  35   b  of the solder resist film  35  is weaker than adhesion strength of the surface  20   b  of the solder resist film  20  at the glass transition point of the first elastomer  21  (i.e., a temperature at which the surface  20   b  present adhesiveness). More specifically, an area of surfaces of particles of the second elastomer  36 , which are exposed on the surface  35   b  of the solder resist film  35 , is smaller than an area of surfaces of particles of the first elastomer  21 , which are exposed on the surface  20   b  of the solder resist film  20 ; or the glass transition point of the second elastomer  36  is higher than the glass transition point of the first elastomer  21 . This similarly applies to both of the solder resist film  35  of the dry film  1  and the solder resist film  35  having been cured at the surface of the wiring board  50 . 
     The following describes a mixed amount of the second elastomer  36  in the solder resist film  35  and a mean diameter of the particles of the second elastomer  36  required to achieve that the area of surfaces of particles of the second elastomer  36 , which are exposed on the surface  35   a  of the solder resist film  35 , is smaller than the area of surfaces of particles of the first elastomer  21 , which are exposed on the surface  20   b  of the solder resist film  20 . A mass ratio of the second elastomer  36  to resin components of the solder resist film  35  is smaller than a mass ratio of the first elastomer  21  to resin components of the solder resist film  20 . Since the mixed amount of the second elastomer  36  in the solder resist film  35  is small, the area of surfaces of particles of the second elastomer  36 , which are exposed on the surface  35   b  of the solder resist film  35 , is small. Furthermore, the mean diameter of the particles of the second elastomer  36  is smaller than that of the first elastomer  21 . The mean diameter of the particles of the second elastomer  36  is, for example, 5 μm or smaller. Thus, a combination of the small mixed amount of the second elastomer  36  in the solder resist film  35  and the small mean diameter of the second elastomer  36  further reduces the area of surfaces of particles of the second elastomer  36 , which are exposed on the surface  35   a  of the solder resist film  35 . 
     A film thickness of the solder resist film  35  is described below.  FIG. 10  is a partial sectional view of the wiring board  50 . The wiring board  50  includes the insulating layer  51 , the wiring layer  52   a  formed on the insulating layer  51 , the solder resist film  20 A arranged on the wiring layer  52   a , and a solder resist film  35 A arranged on the solder resist film  20 A. The solder resist films  20  and  35  are bonded to the insulating layer  51  and the wiring layer  52   a  and then cured to be the solder resist films  20 A and  35 A. The solder resist film  35 A is positioned at the surface of the wiring board  50 . A lower limit of the film thickness of the solder resist film  35 A is a film thickness larger than the mean diameter of the particles of the second elastomer  36 , and an upper limit of the film thickness of the solder resist film  35 A is a film thickness smaller than the film thickness of the solder resist film  20 A. The lower limit is, for example, 5 μm or larger. This is because, if the lower limit of the film thickness of the solder resist film  35 A is smaller than the mean diameter of the particles of the second elastomer  36 , a large number of particles of the second elastomer  36  are exposed on the surface of the wiring board  50  and thus, the wiring board  50  is easily adhered to the dies  110  and  120 . Although each of the solder resist films  20 A and  35 A can relieve the internal stress, since it is preferable that the internal stress is mainly relieved by the solder resist film  20 A including the first elastomer  21 , it is preferable that the upper limit of the film thickness of the solder resist film  35 A does not exceed the film thickness of the solder resist film  20 A. That is, since the film thickness of the solder resist film  35  of the dry film  1  shown in  FIG. 9  changes due to volatilization of solvent included in the solder resist film  35  and contraction in the curing, the solder resist film  35  is formed to secure the above film thickness of the solder resist film  35 A. 
       FIG. 11  is a sectional view showing that the wiring board  50  shown in  FIG. 10  is in contact with the die  110  in the resin sealing process. Referring to  FIG. 11 , the surface  35   b  of the solder resist film  35 A is in contact with the die  110 . Since the area of surfaces of particles of the second elastomer  36 , which are exposed on the surface  35   b , is small, the solder resist film  35 A can be easily detached from the die  110 . Although not shown in  FIG. 11 , the solder resist film  35  having been cured on the opposite side of the wiring board  50  can be easily detached from the die  120 , similarly. 
     A manufacturing method of the dry film  1  according to the second embodiment of the present invention is similar to the manufacturing method of the dry film  1  according to the first embodiment illustrated in  FIG. 7 . Referring to  FIG. 7 , the steps different from those of the first embodiment are described. In Step S 01 , second solder resist material including the second elastomer  36  instead of the second solder resist material is coated on the supporting film  10 . A coating method of the second solder resist material including the second elastomer  36  is similar to that of the first solder resist material. In Step S 02 , the solder resist film  35  is formed by drying the coated second solder resist material including the second elastomer  36  through a heat treatment. The heat treatment is similar to that in the case of the first solder resist material. The solder resist film  35  is formed such that the solder resist film  35  has a film thickness equal to or larger than 5 μm and smaller than the solder resist film  20 A after being cured. The film thickness of the solder resist film  35  is smaller than the film thickness of the solder resist film  20 . The other steps are similar to those of the first embodiment. 
     Since the manufacturing method of the wiring board  50  using the dry film  1  according to the second embodiment of the present invention is similar to that of the first embodiment illustrated in  FIG. 8 , the explanation thereof is omitted. 
     The dry film  1  according to the second embodiment of the present invention includes the solder resist film  35 . The area of surfaces of particles of the second elastomer  36 , which are exposed on the surface  35   b  of the solder resist film, is small. By adhering the dry film  1  to the insulating layer  51  such that the solder resist film  20  is contact with the insulating layer  51 , the solder resist film  35  can be easily arranged at the surface of the wiring board  50 . Since the cured solder resist film  35 A is arranged at the surface of the wiring board  50 , the surface of the wiring board  50  presents a very weak adhesiveness when heated and the wiring board  50  is hard to be adhered to the dies  110  and  120 . Thus, similarly to the first embodiment, the dry film  1  according to the second embodiment can improve the manufacturing throughput of the semiconductor device  100 , since the semiconductor device  100  including the wiring board  50  manufactured by using the dry film  1  can be easily taken out from the dies  110  and  120  in the resin sealing process. Moreover, since the second elastomer  36  included in the solder resist film  351  can relieve the internal stress, the dry film  1  according to the second embodiment can improve the prevention of crack in the surface of the wiring board  50 . 
     Third Embodiment 
     A third embodiment of the present invention is described. The third embodiment is a combination of the first embodiment and the second embodiment. Therefore, components same as those of the first and second embodiments are denoted by the same reference symbols and the explanations thereof are omitted. 
       FIG. 12  is a sectional view of the dry film  1  according to the third embodiment of the present invention. Referring to  FIG. 12 , the dry film  1  according to the third embodiment of the present invention includes the supporting film  10 , the solder resist film  20 , the solder resist film  35 , a solder resist film  37  and the protection film  40 . The supporting film  10 , the solder resist film  20 , the solder resist film  35  and the protection film  40  are the same as those of the first or second embodiments. 
     Referring to  FIG. 12 , the solder resist film  37  is described. The solder resist film  37  is formed between the supporting film  10  and the solder resist film  35 . Therefore, when the dry film  1  is bonded to the core of the wiring board  50  such that the solder resist film  20  is in contact with the core of the wiring board  50 , the solder resist film  37  serves as an insulating film positioned at the surface of the wiring board  50 . The solder resist film  37  does not include elastomer similar to any of the first elastomer  21  and the second elastomer  36 . Since the solder resist film  37  does not include adhesive components, adhesion strength of a surface  37   b  of the solder resist film  37  is weaker than adhesion strength of the surfaces  35   b  and  20   b  of the solder resist films  35  and  20  at the glass transition point of the first elastomer  21  or the second elastomer  36 . This applies to both of a state that the solder resist films  20 ,  35  and  37  are portions of the dry film  1  and a state that the solder resist films  20 ,  35  and  37  have been cured at the surface of the wiring board  50 . The solder resist film  37  does not include elastomer. The composition of the solder resist film  37  is preferably same as those of the first and second solder resist films  20  and  35 , except for the elastomer. 
     A film thickness of the solder resist film  37  is described.  FIG. 13  is a partial sectional view of the wiring board  50 . The wiring board  50  includes solder resist films  20 A,  35 A and  37 A. The solder resist films  20 A,  35 A and  37 A are the solder resist films  20 ,  35  and  37  have been cured on the core of the wiring board  50 . Referring to  FIG. 13 , the solder resist film  37 A is an insulating film which is formed to cover the solder resist film  35 A and positioned at the surface of the wiring board  50 . A pattern is formed in the solder resist film  37 A similarly to the solder resist films  20 A and  35 A such that the wiring layer  52   a  is partly exposed to form electrode pads (not shown). The solder resist film  37 A prevents short circuit in which any portion of the wiring layer  52   a  other than the electrode pads is electrically connected. Since the mean diameter of the particles of the second elastomer  36  included in the solder resist film  35 A is smaller than the mean diameter of the particles of the first elastomer  21  included in the solder resist film  20 A, the film thickness of the solder resist film  37 A can be designed to be smaller than the film thickness of the solder resist film  30 A according to the first embodiment. Specifically, the film thickness of the solder resist film  37 A can be 1 μm or smaller. That is, since the film thickness of the solder resist film  37  of the dry film  1  shown in  FIG. 12  changes due to volatilization of solvent included in the solder resist film  37  and contraction in the curing, the solder resist film  37  is formed to secure the above film thickness of the solder resist film  37 A. 
     Since the adhesion strength of the surface  37   b  of the solder resist film  37 A is weaker than the adhesion strength of the surfaces  35   b  and  20   b  of the solder resist films  35 A and  20 A at the glass transition point of the first elastomer  21  or the second elastomer  36 , the solder resist film  37 A at the surface of the wiring board  50  is hard to be adhered to die  110  even when heated in the resin sealing process. 
       FIG. 14  is a flow chart showing a manufacturing method of the dry film  1  according to the third embodiment of, the present invention. Referring to  FIG. 14 , the manufacturing method of the dry film  1  according to the third embodiment of the present invention is described. 
     Third solder resist material is coated on the supporting film  10  (Step S 20 ). Similarly to the first and second embodiments, a spray method, a screen printing method, a roller coating method or a curtain coating method is used as a coating method of the third solder resist material, for example. 
     The solder resist film  37  is formed by drying the coated third resist material through a heat treatment (Step S 21 ). The heat treatment is performed for 1 to 30 minutes in a temperature range of 60 to 100 degree Celsius, for example The solder resist film  37  is formed to have a film thickness of 1 μm or smaller after being cured. 
     The second solder resist material including the second elastomer  36  is coated on the solder resist film  37  (Step S 22 ). A coating method of the second solder resist material is similar to that of the third solder resist material. 
     The solder resist film  35  is formed by drying the coated second solder resist material including the second elastomer  36  through a heat treatment (Step S 23 ). The heat treatment is similar to that for the third solder resist material. The solder resist film  35  is formed to have a film thickness of 5 μm or larger after being cured. The film thickness of the solder resist film  37  may be smaller than the film thickness of the solder resist film  35 . The solder resist film  35  is formed to have a film thickness smaller than that of the solder resist film  20  to be formed in the following step. 
     The first solder resist material including the first elastomer  21  is coated on the solder resist film  35  (Step S 24 ). A coating method of the first solder resist material is similar to those of the second solder resist material and the third solder resist material. 
     The solder resist film  20  is formed by drying the coated first solder resist material through a heat treatment (Step S 25 ). The heat treatment is performed for 1 to 30 minutes in a temperature range of 60 to 100 degree Celsius, for example. The solder resist film  20  is formed to have a film thickness of 25 to 70 μm after being cured. 
     The protection film  40  is adhered onto the solder resist film  20  (Step S 26 ). 
     Since the manufacturing method of the wiring board  50  using the dry film  1  according to the third embodiment of the present invention is similar to that of the first embodiment illustrated in  FIG. 8 , the explanation thereof is omitted. 
     The dry film  1  according to the third embodiment of the present invention is a layered product provided by combining the first and second embodiments of the present invention. As mentioned above, the embodiments can be combined within a range of not causing contradictions. The dry film  1  according to the third embodiment includes the solder resist film  37  which does not include any of the first and second elastomers  21  and  36  that are softened by heating. By using the dry film  1  according to the third embodiment, the solder resist film  37 A can be easily formed at the surface of the wiring board  50 . Therefore, the wiring board  50  manufactured by using the dry film  1  according to the third embodiment does not present adhesiveness on the surface thereof even when being heated and is hard to adhered to the die. Since the mean diameter of particles of the second elastomer  36  included in the solder resist film  35  is smaller than the mean diameter of particles of the first elastomer  21 , the thickness of the solder resist film  37  can be smaller than the thickness of the solder resist film  30  according to the first embodiment. Since the wiring board  50  can be easily taken out from the dies  110  and  120  in the resin sealing process included in the manufacturing process of the semiconductor device  100 , the dry film  1  according to the third embodiment of the present invention can improve a manufacturing throughput of the semiconductor device  100 , similarly to the first and second embodiments. 
     Fourth Embodiment 
     A fourth embodiment of the present invention is described. A dry film  1  according to the fourth embodiment of the present invention is different from the dry film  1  according the first embodiment in a point that solder resist films  38  are provided in place of the solder resist film  30 . Since the dry film  1  according to the fourth embodiment is same as the dry film  1  according to the first embodiment in the other configurations, the same components are denoted by the same reference symbols and the explanations thereof are omitted.  FIG. 15  is a partial sectional view showing the dry film  1  according to the fourth embodiment of the present invention. 
     Referring to  FIG. 15 , the dry film  1  according to the fourth embodiment of the present invention includes the supporting film  10 , the solder resist film  20 , the solder resist films  38  and the protection film  40 . A film thickness of each of the solder resist films  38  is smaller than the film thickness of the solder resist film  20 . The supporting film  10 , the solder resist film  20  and the protection film  40  are the same as those of the first embodiment. 
     Referring to  FIG. 15 , the solder resist films  38  are described below. One of the solder resist films  38  is arranged between the supporting film  10  and the solder resist film  20 . The solder resist film  38  has a surface  38   b  being in contact with the supporting film  10 . The other of the solder resist films  38  is arranged between the solder resist film  20  and the protection film  40 . The other solder resist film  38  has a surface  38   a  being in contact with the protection film  40 . Similarly to the solder resist film  30  of the first embodiment, each of the solder, resist films  38  does not include elastomer similar to the first elastomer  21  which relieves an internal stress. Since each of the solder resist films  38  does not include the first elastomer  21 , adhesion strengths of the surfaces  38   a  and  38   b  are weaker than adhesion strengths of the surfaces  20   a  and  20   b . This applies to both of a state that the solder resist films  38  are portions of the dry film  1  and a state that the solder resist films  38  have been cured at the surface of the wiring board  50 . Therefore, according to the dry film  1  of the fourth embodiment, the wiring board  50  is hard to be adhered to the dies  110  and  120 , a manufacturing throughput of the semiconductor device  100  including the wiring board  50  is improved, and a malfunction of the semiconductor element  60  provided in the semiconductor device  100  is prevented. 
     Moreover, the solder resist films  38  are formed such that the solder resist film  20  is arranged between the solder resist films  38 . Therefore, when the protection film  40  of the dry film  1  is configured to prevent the films  20  and  38  from being deformed similarly to the supporting film  10 , the dry film  1  can be bonded to the core of the wiring board  50  at either of the surfaces  38   a  and  38   b  of the solder resist films  38 . 
     The first to fourth embodiments can be arbitrarily combined to provide the dry film  1 , and a layer structure of the solder resist films of the dry film  1  is not limited to double or triple layer structure. Moreover, positions of the supporting film  10  and the protection film  40  may be inverted in the first to third embodiments. In this case, the protection film  40  and the supporting film  10  are interchanged in  FIGS. 1 ,  9  and  12 . In the manufacturing methods of these dry films, after the solder resist film  20  is formed on the supporting film  10 , the solder resist film  30  or  35  is formed on the solder resist film  20 . In the case of the third embodiment, the solder resist film  37  is formed on the solder resist film  35 . Thereafter, the protection film  40  is adhered to the solder resist film  30 ,  35 , or  37 . Also, the manufacturing method of the wiring board using any one of the dry films includes steps of: bonding the dry film  1  onto the insulating layer  51 ; exposing the dry film  1  to light; developing the solder resist films with a developing solution; and curing the solder resist films. In the step of bonding the dry film  1  onto the insulating layer  51 , the dry film  1  is bonded on the insulating layer  51  while removing the supporting film  10  from the dry film  1 . When each of these dry films is used, since the supporting film  10  of the dry film  1  should be removed when the dry film  1  is bonded onto the insulating layer  51 , the bonding is somewhat difficult compared to the cases of dry films shown in  FIGS. 1 ,  9  and  12 . 
     The above-mentioned embodiments can be implemented in combination. 
     The embodiments of the present invention have been specifically described. However, the present invention is not limited to the above embodiments, but may be modified and changed without departing from the scope and spirit of the invention.