JP2005244093A - Method and subatrate for packaging electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for packaging an electronic component capable of packaging a highly reliable bonding without decreasing a productivity and a packaging quality even for a micro and narrow pitch of the electronic component. <P>SOLUTION: The method for packaging the elctronic component comprises the steps of printing cream solders 4, 5 on a circuit board 1 with the use of a mask having the predetermined opening part, suppressing a mobility of the cream solder so as to keep the printed shape of the printing cream solders 4, 5, applying a reinforcing thermosetting resin 10 on the circuit board 1 including cream solders 14, 15 with their mobility suppressed, mounting the electronic components 6, 7 to the predetermined position of the circuit board 1, soldering electrode lands 2, 3 and the electrodes 6a, 7a of the electronic components 6, 7 on the circuit board 1 and hardening the reinforcing resin 10 by heating. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electronic component mounting method and an electronic component mounting substrate in which an electrode land formed on a circuit board and an electrode of an electronic component are bonded with a bonding material such as solder.

  2. Description of the Related Art Conventionally, in the manufacture of an electronic component mounting substrate, a chip component having electrodes at both ends of the component, a package component such as a CSP (Chip Size Package) having electrodes in which balls such as solder are arranged in a lattice shape, and the like are represented. A mounting method for soldering an electronic component onto a circuit board using cream solder is widely used. The mounting process is roughly divided into a cream solder printing process, an electronic component mounting process, and a reflow process.

  This mounting process will be described with reference to FIG. In FIG. 2A, 21 is a circuit board, 22 is an electrode land to which the electrode of the chip component 26 is bonded, and 23 is an electrode land to which the electrode of the CSP 27 is bonded. Hereinafter, the chip component 26 and the CSP 27 may be collectively referred to as electronic components 26 and 27.

  First, in the cream solder printing process, the circuit board 21 is positioned and superimposed on a metal mask (not shown) in which a desired pattern opening is formed, and a printing squeegee (not shown) is placed on the mask. FIG. 2B shows the circuit board 21 separated from the mask by linearly moving along the printing direction in a state where it is in contact with an appropriate printing pressure, filling cream opening into the opening of the mask, and then separating the circuit board 21 from the mask. As shown, cream solders 24 and 25 are printed and applied onto the electrode lands 22 and 23 of the circuit board 21 through a mask.

  Next, in the electronic component mounting process, after the electronic components 26 and 27 are attracted and positioned by an electronic component mounting nozzle (not shown), the electronic components 26 and 27 are arranged as shown in FIG. Attached and mounted on the substrate 21. At this time, the electrode 26 a of the chip component 26 and the electrode 27 a of the CSP 27 are placed on the cream solders 24 and 25 printed on the electrode lands 22 and 23, and an electronic component is obtained by the adhesive force of these cream solders 24 and 25. 26 and 27 are held and the process proceeds to the next step.

  In the final reflow process, heat is applied by a heat source (not shown) such as hot air or an infrared heater to melt the printed cream solders 24 and 25, and as shown in FIG. The electronic parts 26 and 27 are joined by solder joints 28 and 29 which are melted and solidified.

  In the above process, the soldering of the electrode lands 22 and 23 of the circuit board 21 and the electrodes 26a and 27a of the electronic components 26 and 27 is completed. There is a problem that bonding reliability such as a decrease in the bonding strength of the solder joint portions 28 and 29 is lowered due to the progress of narrowing and miniaturization. Therefore, a process of filling and curing a reinforcing resin called underfill in the gap between the CSP 27 and the circuit board 21 is added as a separate process. In this underfill filling step, as shown in FIG. 2E, the underfill 30 is applied to the gap between the CSP 27 and the circuit board 21 joined by the solder joint portion 29 by a coating device (not shown) or the like. By doing so, the gap is filled by capillary action.

  Finally, in the underfill curing step, as shown in FIG. 2F, the filled underfill 30 is cured by heating with a heat source (not shown) such as hot air or an infrared heater, and the cured underfill 31 is cured. The CSP 27 and the circuit board 21 are bonded together. The electronic component mounting substrate has been manufactured through the above steps.

  However, in the above electronic component mounting method, after the soldering process of the electrode land of the circuit board and the electrode of the electronic component is completed, underfill filling and curing are required in a separate process, which complicates the manufacturing process. Thus, there are problems such as an increase in manufacturing cost and a decrease in productivity.

  In addition, along with the recent downsizing and higher functionality of electronic devices, the demand for smaller and higher density electronic component mounting boards has led to the reduction in pitch and miniaturization of electrodes due to the downsizing and multi-pins of package components such as CSP. Recently, CSPs having an electrode (ball) pitch of 0.4 mm have begun to be mass-produced, and it is predicted that narrowing of the pitch will continue to proceed rapidly in the future. However, when mounting CSP with an electrode pitch of 0.5 mm and conventional size electronic components such as 1.0 × 0.5 mm or 0.6 × 0.3 mm chip components, cream solder printing on a circuit board is not possible. Usually, a metal mask with a uniform thickness of 0.10 mm or more (about 0.10 to 0.15 mm) is used, and the printing thickness is constant for all electronic components, but the electrode pitch is 0.4 mm. When the following CSP is used, the size of the opening of the mask is reduced. With the conventional mask thickness of 0.10 mm or more, cream solder is clogged in the opening of the mask, and printing defects such as printing defects occur. In order to avoid this, it is conceivable to reduce the mask thickness, but conversely, the amount of cream solder of the electronic components of the conventional size is reduced, the solder joint strength after mounting is weakened, and the joint reliability is lowered. End up. Thus, due to the narrow pitch of the CSP electrodes, there is a problem that the electronic components of the conventional size and the electronic components of the narrow pitch cannot be collectively mounted on the same circuit board.

  As a means for solving such a problem, a no-flow underfill mounting method has been proposed (for example, see Patent Document 1). The no-flow underfill is a resin that contains a flux component, has a flux action during soldering, and exhibits the same effect of improving the joint reliability as the underfill by being cured.

  Each step of the no-flow underfill mounting method will be described with reference to FIG. In FIG. 3A, 41 is a circuit board, 42 is an electrode land to which the electrode of the chip component 46 is bonded, and 43 is an electrode land to which the electrode of the CSP 47 is bonded.

  First, in the cream solder printing step, the cream solder 44 is printed and applied using a metal mask having a uniform thickness of 0.10 mm or more in which a desired pattern opening is formed. Here, without forming the opening of the mask in the portion corresponding to the electrode land 43 on which the narrow pitch CSP 47 is mounted, as shown in FIG. 3B, the solder land is applied to the electrode land on which the narrow pitch CSP 47 is mounted. No printing is performed at 43. This avoids printing defects such as missing prints at a narrow pitch CSP portion in a conventional mask thickness of 0.10 mm or more.

  Next, in the no-flow underfill coating process, as shown in FIG. 3C, a necessary amount of no-flow underfill 50 is previously applied on the electrode lands 43 for the narrow pitch CSP 47 by a coating device (not shown) or the like. Apply.

  Next, in the electronic component mounting step, after the electronic components 46 and 47 are sequentially sucked and positioned by an electronic component mounting nozzle (not shown), the electronic components 46 and 47 are moved as shown in FIG. Attached and mounted on the circuit board 41. At this time, the electrode 46 a of the chip component 46 and the electrode 47 a of the narrow pitch CSP 47 are respectively placed on the cream solder 44 printed on the electrode land 42 and on the no-flow underfill 50 applied to the electrode land 43. The electronic components 46 and 47 are held by these adhesive forces, and the process proceeds to the next step.

In the final reflow process, as shown in FIG. 3E, the electronic components 46 and 47 are soldered onto the circuit board 41 by heating with a heat source (not shown) such as hot air or an infrared heater. At this time, the electrodes 46a and the electrode lands 42 of the chip component 46 are melted and soldered by the solder solder 48, and the electrodes 47a and the electrode lands 43 of the narrow pitch CSP 47 are formed by solder balls. 47a itself is soldered by the molten solder electrode 49. In this reflow process, the no-flow underfill 50 is also cured and the narrow pitch CSP 47 and the circuit board 41 are bonded and fixed by the cured no-flow underfill 51.
Japanese Patent No. 2589239

  However, the above no-flow underfill mounting method has the following problems. First, in the no-flow underfill mounting method, the solder lands are not printed on the electrode lands 43 on which the narrow pitch CSP 47 is mounted. Usually, however, the CSP electrodes (balls) have variations in height. As shown in (d), in the case of the electrode X having a low electrode height, the electrode 47a having a higher electrode height than the electrode X is in contact with the electrode land 43 after the narrow pitch CSP 47 is mounted. It does not reach the electrode land 43 and does not contact. If reflow is performed in such a state, this electrode height variation cannot be absorbed, and the electrode 47a and the electrode land 43 are not joined as shown by Y in FIG. There is a problem that mounting defects occur.

  In the no-flow underfill mounting method, the electrode 47a of the CSP 47 and the electrode land 43 of the circuit board 41 are melted and soldered by the solder ball. However, the amount of solder of the electrode 47a is very large. The bonding strength after soldering is extremely low, and there is a problem that the bonding reliability cannot be ensured even if reinforcement is performed with the underfill 51.

  Further, the electrode 47a of the CSP 47 must be formed of a solder ball that is melted by heating in the reflow process. The CSP 47 in which the electrode 47a is formed of a copper ball, a brass ball, a high temperature solder ball, or the like that is not melted by heating in the reflow process is used. There is a problem that it cannot be implemented.

  In view of the above-described conventional problems, the present invention provides an electronic component mounting method and an electronic component that can be mounted with high bonding reliability without deteriorating productivity and mounting quality even when the electronic components are made minute and narrow in pitch. An object is to provide a mounting substrate.

  The electronic component mounting method of the present invention includes a step of printing a bonding material on a circuit board using a mask having a desired opening, and the flowability of the bonding material so as to maintain the printed shape of the printed bonding material. A step of applying, a step of applying a thermosetting reinforcing resin on a circuit board including a bonding material, a step of mounting an electronic component on a predetermined position of the circuit board, and a land and an electronic component on the circuit board by heating. The step of joining the electrodes and curing the reinforcing resin.

  According to this configuration, since the fluidity of the printed bonding material is suppressed and the reinforcing resin is applied onto the circuit board including the bonding material, the printed shape of the bonding material does not collapse when the reinforcing resin is applied, and then the electronic component is After mounting, it is heated and bonded, and the reinforcing resin is cured, so the mounting process is simple and can be mounted with good productivity, and the thickness of the printing mask is reduced by making the electronic parts minute and narrow pitch. Even if the amount of the bonding material becomes unavoidable, the circuit board and the electronic component are bonded with the reinforcing resin, and the printed shape of the bonding material does not break as described above, and the electrode height depends on the thickness of the bonding material. Therefore, mounting with high bonding reliability can be performed without deteriorating the mounting quality.

  In addition, in the step of suppressing the fluidity of the bonding material, when the reinforcing resin is applied, the printed shape of the bonding material is maintained, but if the fluidity is controlled so as to be deformed by the mounting load when the electronic component is mounted, the reinforcing resin The printed shape of the bonding material does not collapse with the flow of the reinforcing resin when applying the coating, and the mounted electronic component can be held by the deformation of the bonding material due to the mounting load of the electronic component and the adhesive resin's adhesive force, This is preferable because it can prevent the occurrence of mounting defects such as missing parts.

  In the step of suppressing the fluidity of the bonding material, it is convenient and preferable to dry the bonding material and volatilize the solvent in the bonding material. At that time, it is possible to selectively dry the bonding material in almost all regions on the circuit board or the bonding material in a specific region. In addition, drying is preferably performed by hot air, a heater, microwaves, light drying, or vacuum drying.

  In addition, the reinforcing resin can be selectively applied to almost all areas or specific areas on the circuit board, and has a function of adhering the electronic component and the circuit board by using one having a flux action. Is preferably used.

  The mounted electronic component is preferably held by deformation of the bonding material due to the mounting load and the adhesive force of the reinforcing resin.

  Moreover, the electronic circuit board of the present invention is such that an electronic component is mounted on the circuit board by the above-described electronic component mounting method, and an electronic circuit board having the above effects can be provided.

  According to the electronic component mounting method of the present invention, the fluidity of the printed bonding material is suppressed, and after applying the reinforcing resin on the circuit board including the bonding material, the electronic component is mounted, and then heated and bonded. At the same time, since the reinforcing resin is cured, mounting with high bonding reliability can be performed without degrading productivity and mounting quality even when the electronic parts are made minute and narrow in pitch.

  Hereinafter, an embodiment of an electronic component mounting method of the present invention will be described with reference to FIG.

  FIG. 1 is a process diagram of the electronic component mounting method of the present embodiment. In FIG. 1A, 1 is a circuit board, 2 is an electrode land to which the electrodes of the chip component 6 are bonded, and 3 is an electrode land to which electrodes of a narrow pitch CSP 7 are bonded. In this embodiment, a chip capacitor having a size of 1.0 × 0.5 mm is mounted as the chip component 6 and a 0.4 mm pitch CSP is mounted as the narrow pitch CSP 7.

  First, in a printing process of cream solder as a bonding material, the circuit board 1 is positioned and overlapped with a metal mask (not shown) in which a desired pattern opening is formed, and a squeegee for printing (not shown). ) Is moved linearly along the printing direction in contact with the mask with an appropriate printing pressure, cream solder is filled in the opening of the mask, and then the circuit board 1 is separated from the mask. As shown in FIG. 1 (b), cream solders 4 and 5 are printed and applied onto the electrode lands 2 and 3 of the circuit board 1 through a mask.

  Here, the mask thickness was made thinner than the conventional 0.10 mm or more (usually 0.10 to 0.15 mm) to a thickness of 0.06 to 0.08 mm. In this way, by using a uniform thickness mask that can be printed on the electrode lands 3 on which the narrow pitch CSP 7 is mounted, the electrode lands 2 and 3 on which all electronic components including the conventional size chip component 6 are mounted are used. Thus, the cream solders 4 and 5 can be printed stably.

  In the present embodiment, the mask thickness is set to 0.06 to 0.08 mm. However, the present invention is not limited to this, and any thickness that can be printed on an electrode land on which a narrow pitch electronic component is mounted. good.

  Next, in the cream solder drying step, the circuit board 1 on which the cream solders 4 and 5 are printed on the electrode lands 2 and 3 is heated on a hot plate (not shown), and the solvent in the cream solders 4 and 5 and the like. As shown in FIG. 1C, the solder paste 14 and 15 with suppressed fluidity is obtained. Drying is performed at a temperature of 120 to 180 ° C. for 20 to 120 seconds. The cream solders 14 and 15 with suppressed fluidity retain the printed shape of the cream solder against the flow of the reinforcing resin when the reinforcing resin is applied in the reinforcing resin coating process and the electronic component mounting process in the subsequent process. The fluidity is controlled so as to be deformed with respect to the mounting load when mounting the electronic component.

  In the present embodiment, the entire circuit board 1 is heated to dry the cream solders 4 and 5 in almost all areas on the circuit board 1. However, the present invention is not limited to this and is mounted on the circuit board 1. Among the electronic components to be processed, the cream solder 4 or 5 in an area corresponding to one or more specific electronic components may be selectively dried.

  In this embodiment, the hot plate is used as a means for drying. However, the present invention is not limited to this, and the cream solder 4, 5 is dried using hot air, a heater, microwaves, light, or the like, or vacuum drying. May be dried.

  Next, in the reinforcing resin coating process, as shown in FIG. 1 (d), a necessary amount of heat is applied to the entire surface of the circuit board 1 including the cream solders 14 and 15 with suppressed fluidity by a coating device (not shown). A curable reinforcing resin 10 is applied in advance. As the reinforcing resin 10, an epoxy resin that is usually used well is preferably used. The cream solders 14 and 15 with suppressed fluidity can maintain the printed shape because the printed shape is not destroyed by the flow of the reinforcing resin 10 when the reinforcing resin 10 is applied.

  In the present embodiment, the thermosetting reinforcing resin 10 is applied to almost all regions on the circuit board 1, but the present invention is not limited to this. Of the electronic components to be mounted, it may be selectively applied to a region corresponding to one or a plurality of specific electronic components, and in this case, it is applied to a region that matches the region that has been selectively dried in the previous step. Is preferred.

  In this embodiment, application is performed using an application apparatus, but the present invention is not limited to this, and a printing apparatus, an inkjet apparatus, or the like may be used. 10 may be supplied uniformly.

  Next, in the electronic component mounting process, after the chip components 6 and the narrow pitch CSP 7 are sequentially sucked and positioned by an electronic component mounting nozzle (not shown), as shown in FIG. A narrow pitch CSP 7 is mounted and mounted on the circuit board 1. In this case, the fluidity of the cream solders 14 and 15 with suppressed fluidity is controlled so as to be deformed with respect to the mounting load when the chip component 6 and the narrow pitch CSP 7 are mounted as described above. After mounting, the electrode 6a of the chip component 6 and the electrode 7a of the narrow pitch CSP 7 are in a state of piercing the cream solders 14 and 15 with suppressed fluidity, and the electrodes are interposed via the cream solders 14 and 15 with suppressed fluidity. Since the electrodes 7a of the narrow pitch CSP 7 have variations in electrode height because they are stably connected to the lands 2 and 3, even if the electrodes X have a low height, the height variations are absorbed. Occurrence of mounting defects such as non-bonding can be prevented.

  Further, the chip component 6 mounted due to the deformation of the cream solders 14 and 15 that suppresses the fluidity due to the mounting load when mounting the chip component 6 and the narrow pitch CSP 7 and the adhesive force of the thermosetting reinforcing resin 10. By holding the narrow pitch CSP 7, even if the amount of cream solder 14 for the chip component 6 is reduced by using a thin mask that can be printed on the electrode land 3, the holding force of the chip component 6 and the narrow pitch CSP 7 is maintained. Since it does not decrease and is reliably held and proceeds to the next step, it is possible to prevent mounting defects such as missing parts.

  In this embodiment, the mounting load is not particularly controlled. However, the mounting load may be controlled so that the mounting can be performed with an arbitrary load, whereby the deformation of the cream solders 14 and 15 in which the fluidity is controlled. By controlling the amount and adjusting the holding force of the chip component 6 and the narrow pitch CSP 7 and adjusting the amount of solder spread after mounting, it is possible to reliably prevent mounting defects such as shortage and short circuit.

  In the final reflow process, the cream solders 14 and 15 are melted by heating with a heat source (not shown) such as hot air or an infrared heater, and the circuit is formed by the melted and solidified solder as shown in FIG. The chip components 6 and the narrow pitch CSP 7 are soldered on the substrate 1 to form solder joints 8 and 9. Reflow conditions are the standard profile of lead-free solder, preheating at a temperature of 140 to 180 ° C for 90 to 120 seconds, setting the peak temperature to 240 to 250 ° C, and ensuring the solder melting temperature of 220 ° C for 30 seconds or more. To do.

  At this time, the electrodes 6a and the electrode lands 2 of the chip component 6 are soldered by melting the cream solder 14, and the electrodes 7a and the electrode lands 3 of the narrow pitch CSP 7 are formed by the cream solder 15 and the solder balls. 7a itself is melted and soldered. In addition, the reinforcing resin 10 is also cured, and the circuit board 1, the chip component 6, and the narrow pitch CSP 7 are bonded by the heat-cured reinforcing resin 11 to reinforce the solder joints 8 and 9. Thus, since the narrow pitch CSP 7 performs soldering with a solder amount obtained by adding the solder amount of the cream solder 5 to the solder amount of the electrode 7a, the bonding strength after soldering is improved and the reinforcing resin 11 is heat-cured. With the reinforcement of the solder joint portion 9, high joint reliability can be ensured.

  Further, since the circuit board 1 and the chip component 6 are bonded by the heat-cured reinforcing resin 11 and the solder joint portion 8 is reinforced, the printed land has a thickness that can be printed on the electrode land 3 on which the narrow pitch CSP 7 is mounted. Even when the amount of cream solder for the chip component 6 is reduced by using a thin mask, high bonding reliability can be ensured.

  In the present embodiment, the circuit board 1 and the electronic components 5 and 6 are bonded to each other by the reinforcing resin 11 that is heat-cured in almost all regions on the circuit board 1, but the present invention is not limited to this. The circuit board 1 and the electronic components 5 and 6 may be bonded to each other by a reinforcing resin that is selectively heat-cured in a region that matches the coating process of the previous process.

  In the above embodiment, the example in which the electrodes 7a of the narrow pitch CSP 7 are formed by solder balls is shown. However, the soldering is performed by the cream solder 15 that is melted by heating in the reflow process. Instead, it may be an electronic component in which the electrode 7a is formed of a copper ball, a brass ball, a high-temperature solder ball, or the like that is not melted by heating in the reflow process.

  Moreover, although the example which removes the oxide of the electrode at the time of soldering, an electrode land, etc. with the flux of cream solder 4 and 5 was shown, it is not limited to this, In order to improve a flux effect | action further A thermosetting reinforcing resin may have a flux action.

  The electronic component mounting method of the present invention suppresses the fluidity of a printed bonding material, and after applying a reinforcing resin on a circuit board including the bonding material, mounts the electronic component, and then heats and bonds the bonding material. Because the reinforced resin is cured, it is possible to perform mounting with high bonding reliability without degrading productivity and mounting quality even when the electronic components are made minute and narrow in pitch. Circuit board electrode lands and electronic components This is useful for electronic component mounting in which the electrodes are bonded by a bonding material such as cream solder.

It is process drawing of the electronic component mounting method in one Embodiment of this invention. It is process drawing of the underfill mounting method of a prior art example. It is process drawing of the no-flow underfill mounting method of another prior art example.

Explanation of symbols

1 Circuit board 2, 3 Electrode land 4, 5 Cream solder (joining material)
6 Chip parts (electronic parts)
7 Narrow pitch CSP (electronic components)
8, 9 Solder joint 10 Reinforcement resin 11 Heat-cured reinforcement resin 14, 15 Cream solder with suppressed fluidity (joining material)

Claims (10)

  Including a step of printing a bonding material on a circuit board using a mask having a desired opening, a step of suppressing fluidity of the bonding material so as to maintain a printed shape of the printed bonding material, and a bonding material The step of applying a thermosetting reinforcing resin on the circuit board, the step of mounting the electronic component at a predetermined position on the circuit board, the bonding of the land and the electrode of the electronic component by heating, and the hardening of the reinforcing resin An electronic component mounting method comprising the steps of:   In the step of suppressing the fluidity of the bonding material, the printed shape of the bonding material is maintained when the reinforcing resin is applied, but the fluidity is controlled so as to be deformed by the mounting load when mounting the electronic component. The electronic component mounting method according to claim 1.   3. The electronic component mounting method according to claim 1, wherein in the step of suppressing the fluidity of the bonding material, the bonding material is dried to volatilize a solvent or the like in the bonding material.   4. The electronic component mounting method according to claim 3, wherein the bonding material in almost all regions on the circuit board or the bonding material in a specific region is selectively dried.   5. The electronic component mounting method according to claim 3, wherein the drying is performed by hot air, a heater, microwaves, light drying, or vacuum drying.   6. The electronic component mounting method according to claim 1, wherein the reinforcing resin is selectively applied to almost all areas or specific areas on the circuit board.   The electronic component mounting method according to claim 1, wherein a reinforcing resin having a flux action is used.   The electronic component mounting method according to claim 1, wherein a reinforcing resin having an action of bonding the electronic component and the circuit board is used.   The electronic component mounting method according to claim 1, wherein the mounted electronic component is held by deformation of a bonding material due to a mounting load and an adhesive force of a reinforcing resin.   An electronic component mounting board, wherein an electronic component is mounted on a circuit board by the electronic component mounting method according to claim 1.

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