JP2006173654A - Method for forming solder bump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method suitable for forming a high solder bump with superior height accuracy. <P>SOLUTION: The method includes a step to form a resist layer 12 on a substrate 10 wherein an electrode 2 is provided so as to cover the electrode 2, a step to form an opening 11 at the corresponding position to the electrode 2 in the resist layer 12, a step to press-fit a film 4 on the resist layer 12 wherein the opening 11 is formed, a step to form an opening 40 communicating with the opening 11 of the resist layer 12 in the film 4, a step to apply flux in a recess which is comprised of the opening 11 of the resist layer 12 and the opening 40 of the film 4 and wherein the electrode 2 is exposed, a step to fill the recessed part with solder powder, and a step to provide a solder bump 5A on the electrode 2 in the recessed part by melting the solder powder and solidifying it thereafter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solder bump forming method for forming solder bumps on various substrates, an electronic component mounting method, and an electronic component mounting structure. In the present specification, the term “substrate” is not limited to a narrowly defined substrate such as a printed wiring board or a wafer, but refers to a broadly defined substrate including everything that can be a solder bump formation target.

  In recent years, there has been an increasing demand for high-density mounting of electronic components, and the mounting method of electronic components has shifted from a face-up mounting method using wire bonding to a face-down mounting method using solder bumps. There is a tendency to change. Conventionally, a so-called plating method or vapor deposition method has been generally employed as a method for forming solder bumps. However, these methods have problems in that, in addition to requiring large and expensive equipment, it is difficult to control the height of the solder bumps and the solder composition.

  In order to solve the above problems, a method using a heat-resistant insulating film (described in, for example, Patent Document 1 below) or a method using a sheet (for example, described in Patent Document 2 below). Have been proposed in the past.

JP-A-1-161850 JP-A-9-116257

  In the solder bump forming method described in Patent Document 1, as shown in FIG. 9A, the substrate 9 on which the solder bump is to be formed is a surface layer portion 92 of a glass film that covers the aluminum wiring 91 on the surface of the substrate body 90. Are formed, and an electrode 94 is provided in the concave portion 93 of the surface layer portion 92. In order to form solder bumps on the substrate 9, an insulating film 95 is first formed on the surface layer portion 92 as shown in FIG. The insulating film 95 is formed by applying a liquid resin to the entire surface of the surface layer portion 92 and the electrode 94 and then etching the resin on the surface of the electrode 94. Thereby, a recess 93 ′ deeper than the recess 93 can be formed above the electrode 94. Next, as shown in FIG. 9C, after the solder paste 5e is filled in the concave portion 93 ', the solder paste 5e is heated to be remelted and then solidified. According to this method, by forming the insulating film 95 on the surface layer portion 92, the depth dimension of the concave portion 93 'can be increased, and the amount of solder paste filled in the concave portion 93' can be increased. Therefore, as shown in FIG. 9D, a raised solder bump 50 can be formed.

  However, the method shown in FIG. 9 has the following problems. That is, when the insulating film 95 is formed on the surface layer portion 92, a liquid resin is applied to the entire surface of the surface layer portion 92 and the electrode 94, and a part thereof is etched. It has been difficult to accurately finish the desired thickness throughout. Therefore, it is difficult to make the depth of each of the plurality of concave portions 93 'uniform, and it is easy to cause a large variation in the height of the plurality of solder bumps 50 to be formed later. Such a variation in the height of the solder bumps 50 is not preferable when the solder bumps are used for electrical connection with other components.

  Further, when electrical connection with other components is performed using solder bumps, it may be required to increase the solder amount by increasing the height of the solder bumps as much as possible. However, in the conventional method, there is a certain limit to increasing the thickness t of the insulating film 95 formed by applying a liquid resin, and the concave portion 93 'cannot be formed so deeply. For this reason, it has been difficult to form the solder bumps 50 at a certain height or higher. In this conventional method, an insulating film similar to this is further formed on the insulating film 95 to increase the thickness of the entire insulating film. When the resin is applied, the resin is applied in a thick shape in the recess 93 ′, and it is difficult to appropriately etch the resin in this portion.

  On the other hand, the solder bump forming method described in Patent Document 2 uses a sheet 8 having a through hole 80 as shown in FIG. In order to form solder bumps, first, as shown in FIG. 10B, a mask sheet 81 is overlaid on the sheet 8, and this mask sheet 81 is used to form solder paste in the through holes 80 of the sheet 8. After filling 5f, the mask sheet 81 and the sheet 8 are separated from each other as shown in FIG. Next, as shown in FIG. 10D, the sheet 8 is placed on the substrate 82, and the solder paste 5 f is disposed above the electrode 83. When the solder paste 5f is heated and remelted in this state, solder bumps 51 can be formed as shown in FIG. Thereafter, the sheet 8 is removed from the substrate 82 as shown in FIG. According to this method, not only the sheet 8 can be repeatedly used for a plurality of solder bump forming operations, but also the depths and opening diameters of the plurality of through holes 80 formed in the sheet 8 are made uniform in various places. Can do.

  However, in the conventional method shown in FIG. 10, the sheet 8 having a plurality of through holes 80 corresponding to the arrangement of the plurality of electrodes 83 on the substrate 82 needs to be manufactured in advance. Moreover, the production of the sheet 8 needs to be performed as a completely separate operation from the process of forming the electrode 83 on the substrate 82 and the like. For this reason, in addition to the troublesome manufacturing of the sheet 8, if the pitch of the plurality of electrodes 83 becomes fine due to the miniaturization of the integrated circuit pattern, the production of the sheet 80 may be difficult. there were. Further, when the pitch of the plurality of electrodes 83 becomes fine, the alignment accuracy between the plurality of electrodes 83 and the plurality of through holes 80 of the sheet 8 also decreases. As a result, in the latter means, when the pitch of the plurality of electrodes 83 is reduced, it is difficult to accurately align the solder hust 5f on each electrode 83. For example, the solder bumps 51 and 51 adjacent to each other are not aligned. There is a possibility of causing a problem that the conductive contact is unjustified.

  Further, Patent Document 3 below discloses a solder bump forming method that can solve the problems of the above two conventional examples. That is, according to the solder bump forming method disclosed in Patent Document 3, a first solder resist layer is first formed on the surface of a substrate on which a circuit pattern is formed, and then the first solder resist layer is etched to form a circuit pattern. An opening hole is formed in a portion corresponding to the electrode. Next, after applying the second solder resist layer to the surface of the first solder resist layer, the second solder resist layer is etched to form an opening hole in a portion corresponding to the opening hole of the first solder resist layer. Form. Next, solder bumps are formed on each electrode of the circuit pattern by filling the solder paste in the opening holes of both solder resist layers, solidifying after heating and melting. Finally, the first solder resist is not dissolved, and the second solder resist layer is dissolved and removed by a solution that dissolves the second solder resist layer.

JP-A-7-273439

  According to the above method, by using the thickness of the first solder resist layer and the thickness of the second solder resist layer, the depth of the recess filled with the solder paste (formed by the opening holes of both solder resist layers). The solder bump can be formed in a sufficient size by increasing the thickness. In addition, since the first solder resist layer remains even after the second solder resist layer is dissolved and removed, a short circuit between the solder bumps can be prevented, so that a fine pitch between the electrodes can be accommodated.

  However, in the method described in Patent Document 3, when the substrate is mainly composed of a resin having the same quality as that of the second solder resist layer, the substrate is also partially dissolved when the second solder resist layer is dissolved. And cause defects. In addition, a process for dissolving and removing the second solder resist layer is required, and it cannot be said that the working efficiency is good. Furthermore, when joining electronic components, the solder bumps on the electronic component side must be aligned with the solder bumps on the substrate side. If the alignment is poor, the reliability of the product is reduced.

  Therefore, one of the objects of the present invention is to allow a plurality of solder bumps to be accurately formed at a desired height by a simple operation, and even when the substrate is made of resin, the substrate is inadvertently dissolved. An object of the present invention is to provide a solder bump forming method that does not occur. Another object of the present invention is to provide a method and a structure capable of efficiently mounting an electronic component on a substrate without involving a step of dissolving and removing a resin layer used for forming solder bumps. Another object of the present invention is to provide a solder bump forming method suitable for forming solder bumps with high positional accuracy and high uniformity in shape and size. In addition, an object of the present invention is to provide a method suitable for forming a high solder bump excellent in height accuracy.

  According to the first aspect of the present invention, a solder bump is formed in each of the recesses by filling the solder into a plurality of recesses provided in the surface layer portion of the substrate and melting and solidifying the solder. A method of forming solder bumps, including a step of pasting or placing a film on the surface layer portion as a step before filling the plurality of recesses with solder, and a plurality of the steps on the film. And a step of providing a plurality of windows communicating with the recess, wherein the film is made of a material whose main component is different from the material constituting the substrate. Is provided.

  In the first aspect of the present invention, before the solder is filled in the plurality of concave portions of the surface layer portion of the substrate, a film is attached or placed on the surface layer portion, and the plurality of concave portions are formed on the film. Since a plurality of communicating windows are provided, when the solder is filled into the plurality of recesses, the solder can be filled into the windows of the film. Therefore, the height of the solder disposed on the electrode of the substrate can be increased, and the solder bumps can be appropriately formed by solidifying the solder after melting. In addition, if a film having a uniform thickness is used in each part, the depths of the plurality of windows provided in the film are inevitably uniform in each part, and the height of the solder disposed on the plurality of electrodes on the substrate is constant in each part. Can be aligned to height. Therefore, it is possible to prevent a large variation in the height dimension of the plurality of solder bumps. In the present invention, the height of the solder bump is a dimension corresponding to the thickness of the film, and it is easy to set the solder bump to a desired height. Furthermore, the height of the solder bump can be considerably increased by using a thick film as the film or by stacking a plurality of the films.

  And since the said film consists of a material different from the material which comprises a board | substrate, when the said film is melt | dissolved and removed with a solution, a board | substrate is not inadvertently attacked. From such a viewpoint, for example, when the substrate is made of an epoxy resin, the film may be made of an acrylic or imide resin. In addition, when the above film is placed on the surface layer of the substrate (in place of sticking), the film can be easily peeled and removed after the solder bump is formed, and the residue of the film adheres to the electrode, resulting in poor connection. The possibility of waking up can be reduced.

  Preferably, the surface layer portion of the substrate includes a resist layer on the surface of the substrate body, and the resist layer is exposed and developed so that an opening hole is formed above each electrode.

  Preferably, the film is a photosensitive film, and the step of providing the plurality of windows on the film is a step of performing exposure and phenomenon on the film. Alternatively, the step of providing the plurality of opening holes in the film may be a step of performing laser irradiation on the film.

  The step of filling the concave portion of the substrate surface layer with solder is preferably performed by filling solder paste, solder powder, or molten solder from the window portion of the film. In order to fill with molten solder, the substrate may be immersed in a molten solder bath under normal pressure or reduced pressure after forming a window on the film.

  According to the second aspect of the present invention, an electronic component is mounted on a substrate having a surface layer portion in which a plurality of recesses are formed, and the electrodes of the electronic components and the electrodes of the respective recesses are connected via solder. The electronic component mounting method according to claim 1, wherein, as a step before mounting the electronic component on the substrate, a step of attaching or placing a film on the surface layer portion, and a plurality of the film communicating with the plurality of recesses And a step of filling the plurality of window portions and the plurality of concave portions with solder, and after the electronic component is mounted on the substrate, the solder is melted. An electronic component mounting method is provided.

  In the above mounting method, since the electronic component is already mounted on the substrate in the stage of melting the solder arranged on the electrode, when the solder is melted, the electrode of the electronic component and the electrode of the substrate are formed by the solder. Can be connected mechanically and electrically. Therefore, it is not necessary to form solder bumps independently on the substrate side or to remove the film, and it is possible to mount electronic components on the substrate with fewer work steps. As a result, the efficiency of mounting electronic components can be increased. In addition, since the window portion of the film can be used for positioning the solder bumps on the electronic component side, the positioning is easier and the reliability is higher than when the bumps are bumped against each other.

  Of course, in the electronic component mounting method provided by the second aspect of the present invention, the operation process until the plurality of recesses formed in the surface layer portion of the substrate are filled with solder is the first aspect of the present invention. Therefore, the same advantages as those obtained by the above-described first aspect of the present invention can be obtained. In other words, in the electronic component mounting method provided by the second aspect of the present invention, the depth of the plurality of window portions of the film attached to the surface layer portion of the substrate can be made uniform everywhere. The amount of solder that connects the plurality of electrodes and the electronic component can also be made uniform in each place. Further, it is possible to easily increase the amount of solder for connecting the plurality of electrodes of the substrate and the electronic component by increasing the thickness of the film. Therefore, it is possible to appropriately mount the electronic component on the board without causing excess or deficiency in the amount of solder. Furthermore, the operation of providing a plurality of window portions on the film so as to correspond to the plurality of electrodes of the substrate can be performed easily and accurately, and the fine pitch of the plurality of electrodes can be appropriately dealt with.

  According to the third aspect of the present invention, an electronic component is mounted on a substrate having a surface layer portion in which a plurality of concave portions are formed, and the electrodes of the electronic components and the electrodes of the concave portions of the substrate are disposed via solder. An electronic component mounting structure connected, wherein the surface layer portion is formed with a film having a plurality of windows communicating with the recesses. Provided.

  The third aspect of the present invention is intended for the mounting structure obtained by the mounting method according to the second aspect, and the same effect as that obtained by the second aspect can be expected.

  According to a fourth aspect of the present invention, a solder bump forming method is provided. This method includes a step of forming a resist layer on a substrate provided with an electrode so as to cover the electrode (first step), and an opening having a diameter larger than that of the electrode at a position corresponding to the electrode in the resist layer. Forming a film on the resist layer (second process), forming a film on the resist layer (third process), and forming an opening having a larger diameter than the electrode and communicating with the opening in the film A step (fourth step) of filling a solder material into a recess having a diameter larger than that of the electrode and exposing the electrode (fifth step). Step) and a step of providing ball-shaped solder bumps on the electrode surface having a diameter smaller than the bottom surface of the concave portion by utilizing the surface tension of the molten solder at the time of melting by melting and solidifying the solder material (sixth step) ) And solder Including a step (seventh step) of removing the film after the formation of the amplifier.

  In the method of the fourth aspect, the inner peripheral wall of the recess (consisting of the resist layer opening and the film opening) completed in the fourth step, and both ends of the electrode exposed (or facing) the recess Is far from. The separation distance can be set as appropriate. On the other hand, in the melting and solidifying process of the solder material (for example, solder paste) in the sixth step, the solder is condensed into a ball shape on the electrode due to the surface tension of the molten solder at the time of melting, and a solder bump is formed. At this time, if the above-mentioned separation distance is sufficiently secured, the solder is condensed on the electrode center position away from the inner peripheral wall of the recess. Therefore, it is possible to form a solder bump at an accurate position on the electrode center position (that is, the deviation from the electrode center position can be sufficiently suppressed), and in addition, the shape and size of the solder bump to be formed High uniformity can be achieved with respect to (i.e., deviation of the solder bump from the proper shape and size due to the solder adhering to the inner peripheral wall of the recess). Thus, the method according to the fourth aspect of the present invention is suitable for forming solder bumps with high positional accuracy and high uniformity in shape and size.

  In the fourth aspect, preferably, the resist layer has photosensitivity, and the step of forming the opening in the resist layer includes an exposure process and a development process for the resist layer. The film is a photosensitive film, and the step of forming the opening in the film preferably includes exposure processing and phenomenon processing for the film. The exposure process in the step of forming the opening in the resist layer and the exposure process in the step of forming the opening in the film are preferably performed using a mask having the same mask pattern.

  According to a fifth aspect of the present invention, a solder bump forming method is provided. The method includes a step of forming a first resist layer on a substrate provided with an electrode so as to cover the electrode, a step of forming an opening at a position corresponding to the electrode in the first resist layer, A step of pressure-bonding a film to be a second resist layer on the first resist layer in which the opening is formed, a step of forming an opening communicating with the opening of the first resist layer in the film, A step of applying a flux in a concave portion which is composed of an opening portion of a resist layer and an opening portion of a film and exposing an electrode, a step of filling the concave portion with solder powder, and solidifying after melting the solder powder. And a step of providing solder bumps on the electrodes in the recesses.

  In this method, with respect to a synthetic space (concave portion) composed of an opening provided in the first resist layer and an opening provided in the film as the second resist layer so as to communicate with the opening. Solder powder is then supplied, and solder material is melted and solidified in the synthesis space to form solder bumps. That is, in this solder bump forming method, solder bumps are formed using a synthetic space (concave portion) provided in a resist portion that is formed in two layers by the first and second resist layers. Such a solder bump forming method is suitable for forming a high solder bump on an electrode of a substrate.

  In this method, when a plurality of bumps are simultaneously formed on a plurality of electrodes on a substrate, a film having a uniform thickness at each location (a film generally has excellent thickness accuracy) is used. The depth of the plurality of openings can be made uniform everywhere, and the height of the solder material (solder powder) supplied onto the plurality of electrodes of the substrate can be made uniform at each place. As a result, it is possible to prevent a large variation in the height dimension of the plurality of solder bumps to be formed.

  In addition, the flux is applied to the concave portion including the opening portion of the first resist layer and the opening portion of the film that is the second resist layer, and the concave portion is filled with solder powder. Solder powder filling can be appropriately performed while preventing escape of the solder powder. Such suppression of solder powder escape is preferable in forming solder bumps excellent in size accuracy or height accuracy.

  As described above, the solder bump forming method according to the fifth aspect of the present invention is suitable for forming a high solder bump excellent in height accuracy.

  FIG. 1 is a cross-sectional view of an essential part showing an example of a solder bump forming method according to the present invention. FIG. 2 is a fragmentary cross-sectional view showing a manufacturing process of the circuit board shown in FIG.

  A circuit board 1 shown in FIG. 1A is provided with a surface layer portion 12 having a constant thickness in which a plurality of concave portions 11 are formed on the surface of a substrate body 10. For example, a copper electrode 2 is provided inside each recess 11. The substrate body 10 is made of, for example, glass fiber (or glass cloth) reinforced epoxy resin.

  The circuit board 1 originally has a structure in which a plurality of electrodes 2 and wiring portions (not shown) connected thereto are formed on the surface of the substrate body 10 as shown in FIG. The operation of forming the surface layer portion 12 on the substrate body 10 is performed by first forming a photoresist layer 12 ′ having a thickness larger than that of each electrode 2 on the surface of the substrate body 10 as shown in FIG. . Next, as shown in FIG. 2C, the photoresist layer 12 'using the photomask 3 is exposed and developed. When a positive type is used as the photoresist layer 12 ′, for example, a subsequent development process is performed by exposing the formation position of each electrode 2 and its periphery in the photoresist layer 12 ′. Thus, the photoresist can be removed above and around the electrodes 2. Through such a series of steps, the surface layer portion 12 made of a photoresist layer can be provided on the surface of the substrate body 10 as shown in FIG. The solder bump forming operation to be described later can be performed following the operation of providing the surface layer portion 12.

  In order to form solder bumps on the circuit board 1 shown in FIG. 1 (a), first, as shown in FIG. 1 (b), a film 4 having a certain thickness is stuck or placed on the surface of the surface layer portion 12. . When the circuit board 1 is made of glass fiber reinforced epoxy resin, if the film 4 is made of a photosensitive material such as an acrylic resin or an imide resin, the film 4 is later dissolved and removed with a solution. It is possible to prevent the circuit board 1 from being damaged. By attaching or placing the film 4, the upper openings of the concave portions 11 of the surface layer portion 12 are closed.

  Next, as shown in FIG. 1C, the film 4 is provided with a plurality of window portions 40 communicating with the plurality of recesses 11. The opening diameter of each window 40 is the same as or substantially the same as that of each of the recesses 11. The operation of providing a plurality of window portions 40 on the film 4 employs the same technique as that for forming the recesses 11 in the photoresist layer 12 ′ described above, and performs an exposure process and a development process on the film 4, What is necessary is just to remove the part right above each recessed part 11 of the said film 4. FIG. For example, in the case where the photoresist layer 12 ′ is a positive type, if the same positive type photosensitive film is used for the film 4, exposure to the film 4 as shown by the phantom line in FIG. For the processing, the photomask 3 used for the exposure processing on the photoresist layer 12 ′ can be used as it is. Therefore, the photomask 3 can be shared, which is convenient. Furthermore, if the concave portion 11 and the window portion 40 are formed using the same photomask, the concave portion 11 and the window portion 40 can be accurately aligned.

  After the formation of the window portion 40, as shown in FIG. 1 (d), the solder paste 5 is filled into the window portion 40 and the recessed portion 11 below the window portion 40. When filling the solder paste 5, it is desirable that a large amount of excess solder paste does not remain on the upper surface of the film 4. For this purpose, for example, the excess solder paste on the upper surface of the film 4 is scraped using a squeegee. The work to take is good. In this embodiment, instead of the solder paste 5, solder powder may be filled in the window portions 40.

  Thereafter, the solder paste 5 is heated and remelted. As a result, the components other than the solder component contained in the solder paste 5 are volatilized and disappeared, and as shown in FIG. To solidify into the same shape. As a result, a plurality of solder bumps 5A fixed to the respective electrodes 2 are formed. Since each solder bump 5A is formed from the solder paste 5 filled in the window 40 in addition to the recess 11, the height of the solder bump 5A can be increased. Further, since the depth of the window portion 40 can be made uniform at various places, it is possible to prevent a large variation in the height of the solder bumps 5A.

  After the formation of the solder bump 5A, the film 4 is removed from the surface layer portion 12 as shown in FIG. In order to remove the film 4, the film 4 may be peeled off or the film 4 may be dissolved using a suitable solvent. In particular, when the film 4 is merely placed on the surface layer portion 12 of the circuit board 1 (in place of sticking), the film 4 can be easily peeled off. However, the film 4 may be left attached to the surface layer portion 12. If the film 4 is an electrically insulating material, the electrical connection using each solder bump 5A will not be hindered even if the film 4 is left attached to the surface layer portion 12.

  The circuit board 1 obtained by the series of work steps can be used for mounting flip-chip electronic components. That is, as shown in FIG. 3, in order to mount the semiconductor chip 6 on the circuit board 1, first, the bump electrode 61 on the semiconductor chip 6 side is brought into contact with the plurality of solder bumps 5A so as to face the semiconductor chip 6. Is set on the circuit board 1. The bump electrodes 61 on the semiconductor chip 6 side are, for example, solder bump electrodes, and these bump electrodes 61 can also be formed using the solder bump forming method according to the present invention. Next, as shown in FIG. 4, when the plurality of solder bumps 5 </ b> A and the bump electrodes 61 are heated and melted, bumps 5 </ b> B in which the solders constituting the solder bumps 5 </ b> A and the bump electrodes 61 are integrated are formed. Then, the electrodes 2 of the circuit board 1 and the electrodes of the semiconductor chip 6 are connected via the bumps 5B.

  When the mounting operation of the semiconductor chip 6 is performed, it is preferable to apply a flux in advance to the tips of the solder bumps 5A to improve so-called wettability. As an example of the flux, rosin is used as a main component, and a solvent such as ethanol, an organic acid, or an organic halogen activator can be used. Further, in addition to the application of the flux or in place of the application of the flux, when the adhesive is applied to the tip of each solder bump 5A, each solder bump 5A and each bump electrode 61 is utilized by utilizing the adhesive property of the adhesive. Positioning and holding can be achieved. As the pressure-sensitive adhesive, for example, rosin can be applied.

  Further, when performing the mounting operation of the semiconductor chip 6, as shown in FIG. 5A, a flat portion 55 may be formed on the upper part of the solder bump 5A. The flat portion 55 can be formed, for example, by pressing the solder bump 5A from above. If such a flat portion 55 is formed, the bump electrode 61 of the semiconductor chip 6 can be stably disposed on the flat portion 55 of the solder bump 5A as shown in FIG. 5B. In addition, when applying a flux or an adhesive, these may be applied to the flat portion 55, and the operation becomes easy.

  FIG. 6 is a cross-sectional view of the main part showing another example of the solder bump forming method according to the present invention. In FIG. 6 and the subsequent drawings, the same parts as those in the previous embodiment are indicated by the same reference numerals.

  The method shown in FIG. 6 is a method in which two films 4 and 4A are attached to or placed on the surface layer portion 12 of the circuit board 1. More specifically, first, as shown in FIG. 6A, the first film 4 is attached or placed on the surface layer portion 12 of the circuit board 1, and a plurality of window portions 40 are formed on the film 4. Provide. The configuration of the circuit board 1 is the same as that shown in FIG. 1C, and the work steps up to that are the same as those of the previous embodiment.

  Next, as shown in FIG. 6B, a second film 4 </ b> A having the same material as the photosensitive film 4 is attached or placed on the upper surface of the film 4.

  Thereafter, as shown in FIG. 6C, the exposure process and the phenomenon process of the second film 4A are performed. Thereby, as shown in FIG.6 (d), the location which forms the window part 40A of the said 2nd film 4 rum 4A is right above each window part 40. As shown in FIG. Therefore, the plurality of window portions 40A can be appropriately formed on the film 4A by the exposure and development processing.

  After forming the window portion 40A, as shown in FIG. 6E, the window portion 40A, the window portion 40 communicating with the window portion 40A, and the plurality of recesses 11 are filled with the solder paste 5. Thereafter, similar to the process shown in FIG. 1E, the solder paste 5 is heated and remelted and then solidified. Thereby, a solder bump can be formed.

  According to the above method, the amount of the solder paste 5 used for forming the solder bumps can be increased by the depth of the window 40 formed using the second film 4A, and the height of the solder bumps can be increased. Can be higher. As described above, in this embodiment, not only one film is used, but also two films or a plurality of films of a larger number are sequentially stacked on the surface layer portion of the circuit board. You may make it provide a window part in each.

  FIG. 7 is an explanatory view showing another example of solder filling work. In the work process shown in the figure, the circuit board 1 is immersed in the molten solder bath 5C in the solder storage tank 19. The circuit board 1 is provided with a plurality of window portions 40 by pasting the film 4 on the surface layer portion 12, and the configuration of the circuit board shown in FIGS. 1 (c) and 6 (a). Is the same. At this time, in order to ensure that the molten solder flows into the window 40 of the minute film 4, it is preferable to perform this operation under reduced pressure. According to the operation process shown in FIG. The melted solder 5C can be filled into the twelve recesses 11. If the circuit board 1 is pulled up from the solder storage tank 19 and the filled molten solder is naturally cooled, the solder bump 5A can be formed as it is, as indicated by the phantom line in FIG. In the present embodiment, it is not necessary to reheat and melt the solder, and components other than the solder component are volatilized and lost as in the case of using the solder paste, and the solder bump does not fade by that amount. However, if the posture of the circuit board 1 is not stabilized at an early stage after the circuit board 1 is pulled up from the solder storage tank 19, the solder bump 5 </ b> A may be solidified at a position where the electrode 2 is biased. In such a case, as in the case of using a solder paste, components other than the solder component volatilize and disappear, and the solder bump does not fade by that amount. However, if the posture of the circuit board 1 is not stabilized at an early stage after the circuit board 1 is pulled up from the solder storage tank 19, the solder bump 5 </ b> A may be solidified at a position where the electrode 2 is biased. In such a case, after the circuit board 1 is stabilized in a horizontal state, the solder bump 5A is reheated and the correction is performed.

  As described above, in the present invention, the solder filling method is not limited to using solder paste or solder powder, and molten solder may be filled. In addition, the solder referred to in the present invention is not limited to those containing Sn, Pb, In, or the like as a main component, but also includes those containing, as a main component, Ag or the like used for joining electronic components.

  FIG. 8 is a cross-sectional view showing an example of an electronic component mounting method according to the present invention. In this electronic component mounting method, first, as shown in FIGS. 8A to 8D, a film 4 is pasted or placed on the surface layer portion 12 of the circuit board 1, and a plurality of windows are formed on the film 4. A portion 40 is provided, and the solder paste 5 is filled into the plurality of window portions 40 and the concave portions 11 communicating with the window portions 40. These series of work steps are the same as the work steps shown in FIGS.

  After the filling operation of the solder paste 5, as shown in FIG. 8E, the semiconductor chip 6 to be mounted is set so that the bump electrode 61 is in contact with the solder paste 5.

  When the solder paste 5 is heated and melted in this state and then solidified, as shown in FIG. 8 (f), each electrode 2 of the circuit board 1 and the semiconductor via the solder 5D formed in a substantially ball shape. The electrodes of the chip 6 can be connected. Since the solder 5D is formed from the solder paste 5 having a large volume filled in the concave portion 11 and the window portion 40, the amount of the solder 5D can be prevented from being insufficient. The film 4 may be stuck or placed on the circuit board 1. However, the film 4 may be removed by dissolving it with a solvent.

  The specific configuration of each work process of the solder bump forming method and the electronic component mounting method according to the present invention is not limited to the above-described embodiment.

  In the present invention, for example, the diameter of each window portion formed in the film may not be the same as or substantially the same as the diameter of the concave portion of the surface layer portion of the substrate, and may be larger or smaller than the concave portion.

  In the present invention, the surface layer portion of the substrate may be the surface layer portion (surface) of the substrate itself. For example, as a method of forming an electrode on the surface of a silicon substrate, an oxidation process is performed on the surface of the silicon substrate to form an insulating layer (silicon oxide layer) on the surface of the silicon substrate, and etching is performed on the insulating layer. There is a method in which a recess is formed by processing, and then an electrode made of aluminum or the like is formed in the recess, but the present invention can also be applied to a substrate in this way.

  In the present invention, the specific configuration of the concave portion provided in the surface layer portion of the substrate is not limited to the above-described embodiment. For example, the opening diameter of the recess may be smaller than that of the electrode, and only a part of the surface of the electrode may be exposed through the recess. Moreover, as shown to Fig.9 (a) showing a prior art example, the structure which an electrode itself has a recessed part may be sufficient.

  Furthermore, in the present invention, as a method for providing a window portion on a film affixed to a surface layer portion of a substrate, for example, means for irradiating a film with a laser may be employed. As the laser, various lasers such as an excimer laser and a YAG laser can be used. When a window is provided in the film by laser irradiation, it is not necessary to use a photosensitive film as the film, and for example, a polyimide film may be used.

  By forming a photoresist layer having a thickness of 25 μm on the surface of a substrate made of glass fiber reinforced epoxy resin in which a large number of copper electrodes having a diameter of 50 μm are formed on the surface at a pitch of 150 μm, the exposure / development treatment is performed, A large number of recesses with a diameter of 80 μm were formed in the photoresist layer to expose the electrodes to the outside. The photoresist layer was an epoxy acrylate resin system. Thereafter, an acrylic resin photosensitive film having a thickness of 50 μm is thermocompression-bonded (105 ° C., pressure 3.5 Kg / cm 2) on the upper surface of the photoresist layer and exposed using a glass mask, and then a 1% sodium carbonate solution The photosensitive film was etched and developed to form a window having a diameter of 80 μm that overlapped the concave portion. Next, a solder paste containing about 50% of 63% Sn—Pb solder in a volume ratio was filled into the window portion and the concave portion by a printing method, and heated and melted at 210 ° C. Thereafter, the photosensitive film was removed using a 3% sodium hydroxide solution.

  As a result, a large number of solder bumps having an average height of 60 μm could be formed. The variation in the height of these many solder bumps was within 2 μm. Moreover, when the photosensitive film was dissolved and removed, the substrate was never eroded.

  By forming a photoresist layer having a thickness of 25 μm on the surface of a substrate made of glass fiber reinforced epoxy resin in which a large number of copper electrodes having a diameter of 50 μm are formed on the surface at a pitch of 150 μm, the exposure / development treatment is performed, A large number of recesses with a diameter of 80 μm were formed in the photoresist layer to expose the electrodes to the outside. The photoresist layer was an epoxy acrylate resin system. Thereafter, an acrylic resin photosensitive film having a thickness of 50 μm is thermocompression-bonded (105 ° C., pressure 3.5 kg / cm 2) on the upper surface of the photoresist layer, exposed to light using a glass mask, and then 2.3% tetramethyl. The photosensitive film was etched and developed with an ammonium hydroxide solution to form a window portion having a diameter of 120 μm that overlapped the concave portion. Next, a solder paste containing about 50% of 63% Sn—Pb solder in a volume ratio was filled into the window portion and the concave portion by a printing method, and heated and melted at 210 ° C. Thereafter, the photosensitive film was removed using a 10% monoethanolamine solution.

  As a result, a large number of solder bumps having an average height of 75 μm could be formed. The variation in the height of these many solder bumps was within 1.5 μm. Moreover, when the photosensitive film was dissolved and removed, the substrate was never eroded.

  By forming a photoresist layer having a thickness of 25 μm on the surface of a substrate made of glass fiber reinforced epoxy resin in which a large number of copper electrodes having a diameter of 50 μm are formed on the surface at a pitch of 150 μm, the exposure / development treatment is performed, A large number of recesses with a diameter of 80 μm were formed in the photoresist layer to expose the electrodes to the outside. The photoresist layer was an epoxy acrylate resin system. Thereafter, an acrylic resin photosensitive film having a thickness of 50 μm is placed on the upper surface of the photoresist layer (at 25 ° C.), exposed using a glass mask, and then exposed to 2.3% tetramethylammonium hydroxide solution. The conductive film was etched and developed to form a window portion having a diameter of 120 μm that overlapped with the concave portion. Next, a solder paste containing about 50% of 63% Sn—Pb solder in a volume ratio was filled into the window portion and the concave portion by a printing method, and heated and melted at 210 ° C. Thereafter, the photosensitive film was removed using a 5% monoethanolamine solution.

  As a result, a large number of solder bumps having an average height of 75 μm could be formed. The variation in the height of these many solder bumps was within 1.5 μm. Moreover, when the photosensitive film was dissolved and removed, the substrate was never eroded.

  An acrylic resin photosensitive film having a thickness of 50 μm is thermocompression-bonded on the surface of a substrate on which a large number of electrodes having a Ni diameter of 70 μm and a concave surface are formed at a pitch of 150 μm and other than the upper part of the electrode is coated with polyimide (105 And exposed to light using a glass mask, the photosensitive film was etched and developed with a 2.3% tetramethylammonium hydroxide solution, and a window portion having a diameter of 120 μm overlapped with the concave portion. Formed. Next, a solder paste containing about 50% of 63% Sn—Pb solder in a volume ratio was filled into the window portion and the concave portion by a printing method, and heated and melted at 210 ° C. Thereafter, the photosensitive film was removed using a 10% monoethanolamine solution.

  As a result, a large number of solder bumps having an average height of 70 μm could be formed. The variation in the height of these many solder bumps was within 1.5 μm. Moreover, when the photosensitive film was dissolved and removed, the substrate was never eroded.

  An acrylic resin photosensitive film having a thickness of 50 μm is placed on the surface of a substrate on which a large number of electrodes having a Ni diameter of 70 μm and a concave surface are formed at a pitch of 150 μm and the upper part of the electrode is covered with polyimide (25 And exposed to light using a glass mask, the photosensitive film was etched and developed with a 2.3% tetramethylammonium hydroxide solution to form a window portion having a diameter of 120 μm that overlapped the concave portion. Next, a solder paste containing about 50% of 63% Sn—Pb solder in a volume ratio was filled into the window portion and the concave portion by a printing method, and heated and melted at 210 ° C. Thereafter, the photosensitive film was removed using a 5% monoethanolamine solution.

  As a result, a large number of solder bumps having an average height of 70 μm could be formed. The variation in the height of these many solder bumps was within 1.5 μm. Moreover, when the photosensitive film was dissolved and removed, the substrate was never eroded.

  By forming a photoresist layer having a thickness of 25 μm on the surface of a substrate made of glass fiber reinforced epoxy resin in which a large number of copper electrodes having a diameter of 50 μm are formed on the surface at a pitch of 150 μm, the exposure / development treatment is performed, A large number of recesses with a diameter of 80 μm were formed in the photoresist layer to expose the electrodes to the outside. The photoresist layer was an epoxy acrylate resin system containing barium sulfate as a filler. Thereafter, a polyimide film having a thickness of 50 μm was placed on the upper surface of the photoresist layer, and a window part having a diameter of 120 μm was formed on the electrode using an excimer laser. Next, a solder paste containing about 50% of 63% Sn—Pb solder in a volume ratio was filled into the window portion and the concave portion by a printing method, and heated and melted at 210 ° C. Thereafter, the polyimide film was removed using a 5% monoethanolamine solution.

  As a result, a large number of solder bumps having an average height of 75 μm could be formed. The variation in the height of these many solder bumps was within 1.5 μm. Moreover, when the photosensitive film was dissolved and removed, the substrate was never eroded.

  A carbon dioxide gas laser is formed by placing an acrylic resin film having a thickness of 50 μm on the surface of a substrate on which a large number of electrodes each having a diameter of 70 μm and a concave shape are formed with a pitch of 150 μm and the upper part of the electrode is covered with polyimide. A window part having a diameter of 120 μm was formed on the upper part of the electrode. Next, a solder paste containing about 50% of 63% Sn—Pb solder in a volume ratio was filled into the window portion and the concave portion by a printing method, and heated and melted at 210 ° C. Thereafter, the film was removed using a 5% monoethanolamine solution.

  As a result, a large number of solder bumps having an average height of 70 μm could be formed. The variation in the height of these many solder bumps was within 1.5 μm. Moreover, when the photosensitive film was dissolved and removed, the substrate was never eroded.

  In the process of Example 1, solder powder (63% Sn—Pb) having an average particle diameter of 15 μm was used in place of the solder paste. In addition, before filling the solder powder with the window portion of the photosensitive film and the concave portion of the photoresist layer, flux (product ULF-500VS manufactured by Tamura Kaken Co., Ltd.) is applied to the inner surface of the window portion and the concave portion. A slight amount was applied. The other conditions were the same as in Example 1.

  As a result, as in Example 1, a large number of solder bumps having an average height of 60 μm could be formed. The variation in the height of these many solder bumps was within 2 μm. Moreover, when the photosensitive film was dissolved and removed, the substrate was never eroded.

  In the process of Example 1, instead of filling the window portion of the photosensitive film with solder paste, the whole substrate was immersed in molten solder (63% Sn—Pb) at 210 ° C. Solidified. Before immersing the entire substrate in molten solder, a flux coating process was performed in the same manner as in Example 2. The other conditions were the same as in Example 1.

  As a result, a large number of solder bumps having an average height of 70 μm could be formed. The variation in the height of these many solder bumps was within 2 μm. Moreover, when the photosensitive film was dissolved and removed, the substrate was never eroded.

  In the process of Example 1, instead of the photosensitive film having a thickness of 50 μm, a photosensitive film having the same material thickness as that of 40 μm was used. After a large number of windows having a diameter of 80 μm are formed on this photosensitive film, a second photosensitive film having the same material as that of the photosensitive film and having a thickness of 40 μm is thermocompression bonded, and two photosensitive films are stacked. It was. This second photosensitive film was also exposed and developed under the same conditions as the first photosensitive film, and many 80 μm diameter windows overlapped with the window of the first photosensitive film. Formed. Thereafter, a solder paste containing about 50% of a 63% Sn—Pb solder in a volume ratio is filled in each of the window portions of the two photosensitive films and the recesses of the photoresist layer by a printing method. And melted by heating. Thereafter, the two photosensitive films were removed using a 3% sodium hydroxide solution.

  As a result, a large number of solder bumps having an average height of 80 μm could be formed. The variation in the height of these many solder bumps was within 2 μm. Further, when the second photosensitive film was dissolved and removed, the substrate was never eroded.

  In the process of Example 4, solder powder (63% Sn-Pb) having an average particle diameter of 15 μm was used in place of the solder paste. Further, before filling the solder powder in the window portion, a small amount of flux was applied to the inner surfaces of the two photosensitive film window portions and the photoresist layer concave portions in the same manner as in Example 2. The other conditions were the same as in Example 4.

  As a result, a large number of solder bumps having an average height of 80 μm could be formed. The variation in the height of these many solder bumps was within 2 μm. Moreover, when the photosensitive film was dissolved and removed, the substrate was never eroded.

  In the step of Example 4, instead of filling the windows of the two photosensitive films with solder paste, the entire substrate was dipped in 210 ° C. molten solder (63% Sn—Pb), pulled up, and left as it was. Solidified by natural cooling. Prior to immersing the entire substrate in molten solder, a small amount of flux was applied to the inner surfaces of the window portion of the photosensitive film and the concave portion of the photoresist layer in the same manner as in Example 5. The other conditions were the same as in Example 4.

  As a result, a large number of solder bumps having an average height of 90 μm could be formed. The variation in the height of these many solder bumps was within 2 μm. Further, when the second photosensitive film was dissolved and removed, the substrate was never eroded.

  A thermosensitive film having a thickness of 50 μm was thermocompression-bonded on the photoresist layer of the substrate under the same conditions as in the previous step of Example 1, and after forming a large number of windows having a diameter of 80 μm on the photosensitive film, these A number of windows were filled with solder paste. Thereafter, a semiconductor chip having a plurality of bump electrodes is placed on the substrate, and the solder paste is heated and melted at 210 ° C. with the plurality of bump electrodes partially entering the solder paste in the window. Then, it was solidified by natural cooling.

  As a result, the semiconductor chip could be properly mechanically and electrically connected to the substrate.

It is principal part sectional drawing which shows an example of the formation method of the solder bump which concerns on this invention. It is principal part sectional drawing which shows the manufacturing process of the circuit board shown to (a) of FIG. It is principal part sectional drawing which shows an example of the method of mounting an electronic component on the board | substrate with which the solder bump was formed by the method shown in FIG. It is principal part sectional drawing which shows the mounting structure of the electronic component obtained by the mounting method shown in FIG. It is principal part sectional drawing which shows the other example of the method of mounting an electronic component on the board | substrate with which the solder bump was formed by the method shown in FIG. It is principal part sectional drawing which shows the other example of the formation method of the solder bump which concerns on this invention. It is principal part sectional drawing which shows the example of the solder filling operation | work using a fusion | melting solder. It is sectional drawing which shows an example of the mounting method of the electronic component which concerns on this invention. It is principal part sectional drawing which shows an example of the conventional solder bump formation method. It is sectional drawing which shows the other example of the conventional method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circuit board 2 Electrode 3 Photomask 4 Film 5 Solder paste 5A Solder bump 6 Semiconductor chip 10 Substrate body 11 Concave part 12 Surface layer part 12 'Photoresist layer

Claims (1)

Forming a first resist layer on the substrate provided with the electrodes so as to cover the electrodes;
Forming an opening at a position corresponding to the electrode in the first resist layer;
A step of pressure-bonding a film to be a second resist layer on the first resist layer in which the opening is formed;
Forming an opening in the film that communicates with the opening of the first resist layer;
A step of applying a flux in a recess formed of the opening of the first resist layer and the opening of the film and exposing the electrode;
Filling the recess with solder powder;
Providing a solder bump on the electrode in the recess by solidifying the solder powder after melting the solder powder.

Images