JP3736001B2 - Electronic component mounting method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronic component mounting method, and more particularly, to improve wire bondability in a mounting method in which wire bonding is performed directly on a conductor on a circuit board and an electronic component such as a semiconductor chip is connected. Related to the method.
[0002]
[Prior art]
Conventionally, when a semiconductor chip or individual electronic component is mounted on a circuit board and a terminal is taken out via a lead 100 as shown in FIG. 27, for example, between the electrode 102 on the circuit board 101 and the lead 100, Electrical connection is performed by wire bonding using the wire 103.
[0003]
As the electrode 102 on the substrate 101, a metal pad 106 bonded to the conductor 104 on the circuit substrate 101 with a solder 105 is generally used. As a specific material of the metal pad 106, a Ni alloy plated on 42 alloy, 50 alloy or the like, and an Al clad material on the bonding side are used.
[0004]
[Problems to be solved by the invention]
In general, the metal pad 106 cannot be machined as small as about 1 mm in diameter and 1 mm in thickness due to restrictions on the metal punching process. Therefore, the circuit board 101 is inevitably associated with the installation of the metal pad 106. There was a problem that would become larger.
[0005]
Further, in order to form the metal pad 106, a Ni plating process or the like is required after the punching process, and the manufacturing process is complicated, resulting in an increase in manufacturing cost.
On the other hand, Japanese Patent Laid-Open No. 5-326805 proposes a technique for eliminating the metal pad 106 and directly bonding the wire to the conductor 104 on the circuit board 101.
[0006]
Here, according to the trial production and examination by the present inventors, when a wire-bonded conductor 104 is Au-plated, Au thick film, or Ni-plated, wire bonding is directly performed on the conductor 104. It has been confirmed that there is no particular problem with the bondability associated with the process.
However, in the case of Au plating or Au thick film, there is a problem that the substrate manufacturing cost becomes high due to the material cost and processing steps. In addition, the combination of Au and Al wire has a problem that corrosion occurs at the bonding interface and the moisture resistance of the wire bonding portion is inferior.
[0007]
In the case of employing Ni plating, a Ni plating layer is first formed on the surface of the substrate, and a thick film conductor, for example, a Cu thick film is formed on the Ni plating layer. There is a problem that the solder wettability of the Cu thick film portion on the Ni plating is lowered and solder joint failure is likely to occur.
Therefore, the present inventors tried to adopt a Cu-based conductor such as a Cu thick film or Cu plating as a wire bonding conductor on the circuit board in order to solve such a problem.
[0008]
However, in the method of mounting a hybrid integrated circuit using a Cu-based conductor such as a Cu thick film or Cu plating as a conductor material for wire bonding of a circuit board, even if a cleaning process is performed after the solder reflow process, the wire bonding It has been found that there is a problem that dirt remains on the conductor for use and the bondability of the wire bond is deteriorated. Hereinafter, the reason for the occurrence of this problem will be described in detail with reference to the flowchart of the conventional process shown in FIG.
[0009]
In the mounting method of FIG. 28, first, a circuit board on which a wiring pattern is formed is prepared. Next, a solder paste is printed on the mounting component mounting portion of the wiring pattern on the circuit board. Thereafter, the mounted component is mounted (assembled) on a predetermined portion of the wiring pattern. Next, the solder is melted by the reflow process to fix the mounting component, and thereafter, the contaminants due to the flux and the like are cleaned by the cleaning process, and finally the wire bonding is performed on the wire bonding conductor of the circuit board.
[0010]
However, according to such a mounting method, during solder reflow, the activator Br or Cl in the solder flux is eluted or scattered together with the solvent or the resin component in the flux, and the conductor (Cu thick film, Cu Reaction) with the oxide of the conductor formed on the surface of the conductor or the surface of the conductor, and a reaction product is formed on the surface of the conductor in a granular or uniform manner. Contamination of the conductor surface with this reaction product causes subsequent wire bonding. It was found that the bondability was lowered.
[0011]
It has been found that such trouble due to contamination of the conductor surface does not occur when an Al pad or Au conductor is used as a conductor, but is an inherent problem particularly generated when a Cu-based conductor is used.
Furthermore, in the case of Cu thick film and Cu plating, in addition to solder reflow, by heating and curing the resin and adhesive in the heating process at the time of curing the adhesive and the packaging process for bonding the circuit board and case, It has also been found that the surface of the Cu thick film and Cu plating is oxidized, and the problem that the bondability of the wire bond is lowered occurs.
[0012]
As countermeasures against such problems, Japanese Patent Application Laid-Open Nos. 58-111329 and 6-260520 have already been proposed in which oxide films and contaminants are removed mechanically.
However, since these conventional techniques perform the removal process for each pad, when a large number of bonding pads are provided, there is a problem that this removal process takes a lot of time and increases the cost. Moreover, even if the oxide film and contaminants are mechanically removed, there is a problem that the powder accompanying the removal remains on the substrate surface and the bondability of the wire bond is not stable.
[0013]
The present invention has been made in view of the above-described circumstances. In a mounting method in which wire bonding is performed directly on a Cu-based conductor on a circuit board, the bonding property of wire bonding is improved, and mounting by wire bonding is low cost. It is intended to be able to be implemented in.
[0014]
[Means for Solving the Problems]
  The present invention employs the following technical means to achieve the above object.To do.
[0019]
  Claim 1In the invention described in the above, the electronic component mounting method is a container (32) in which a paste-like resin (33) for forming the coating resin layer (31) is formed and a resin coating pattern (32a) is formed on the bottom. The resin coating pattern (32a) of the container (32) and the Cu-based conductors (11, 13) for wire bonding of the circuit board (1) are positioned, and then the container (32 The resin layer (31) is coated on the Cu-based conductors (11, 13) for wire bonding by discharging the paste-like resin (33) through the resin coating pattern (32a) at the bottom of). And Also,Claim 2In the invention described in, after the Cu-based conductor (11) to be wire bonded to the electronic component (41) is coated with the resin layer (31), the electronic component (41, 42) is soldered or bonded with an adhesive. After fixing, the coating resin layer (31) is peeled off, and thereafter, the Cu-based conductor (11) from which the resin layer (31) is peeled and the electronic component (41) are wire bonded. Yes. In this electronic component mounting method, the coating resin layer (31) is sucked by a vacuum nozzle (91) to which a vacuum is applied, and the tip of the vacuum nozzle (91) is engaged with the coating resin layer (31). By stopping, the coating resin layer (31) is peeled off by applying an external force in a direction away from the circuit board (1) to the coating resin layer (31).Claims 1 and 2According to the invention, contamination of the wire bonding pad conductor (11) that occurs when the electronic component is mounted on the circuit board and reflowed can be prevented by covering with the resin layer (31). Further, in the case where the adhesive is fixed, oxidation of the wire bonding pad conductor (11) can be prevented by heating for curing. Therefore, wire bonding can be performed while keeping the conductor (11) clean, and the bondability of wire bonding can be improved. Also,
Claim 1In the present invention, the coating resin layer (31) can be formed using a stamp method,Claim 2In this invention, the coating resin layer (31) can be easily peeled off using a vacuum.
[0022]
  Claim 3In this invention, after coating the Cu-based conductor (11) to be wire bonded to the electronic component (41) with the resin layer (31), the electronic components (41, 42) are fixed by soldering, and thereafter The electronic component mounting method is a method of peeling the coating resin layer (31), and thereafter wire bonding the Cu-based conductor (11) and the electronic component (41) from which the resin layer (31) has been peeled off. A protective layer (37) for protecting the coating resin layer (31) from a cleaning solution used for cleaning the circuit board (1) after soldering is formed on the surface of the coating resin layer (31).
[0023]
  Accordingly, the coating resin layer (31) can be protected from the cleaning liquid, and the Cu-based conductor (11, 13) under the coating resin layer (31) can be prevented from being oxidized. Therefore, the Cu-based conductor (11, 13) can be prevented. The bondability of wire bonding to can be improved. Also,Claims 4 and 5In the present invention, the contaminants and oxides on the bonding pad conductors (11, 13) are removed by the plasma cleaning method immediately before the wire bonding, so that the wire bonding can be performed directly on the Cu-based conductor. Stable bondability can be ensured.
[0024]
In addition, the code | symbol in the bracket | parenthesis of each said means shows a corresponding relationship with the specific means of embodiment description later mentioned.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIGS. 1-13 shows 1st Embodiment, FIG. 1 is a flowchart which shows the flow of the whole process of the mounting method at the time of introduce | transducing the resin application | coating process of this invention, FIG. 6, 7, 8, and 13 are diagrams specifically showing each process of the mounting method. First, a circuit board 1 having a wiring pattern made of a Cu-based conductor such as a Cu thick film and Cu plating as shown in FIG. 2 is prepared. The circuit board 1 is formed by molding a ceramic insulating material.
[0026]
Here, the wiring pattern on the circuit board 1 includes a conductor 11 as a pad for wire bonding a semiconductor chip and a substrate electrode, a conductor 13 as a wire bonding pad for external connection, and a die pad for mounting the semiconductor chip. It is assumed that a conductor pattern 12 and a terminal pattern 20 for connecting electronic components are included.
Next, as shown in FIG. 3, a solder paste 21 is printed by screen printing on the terminal pattern 20 for connecting electronic components and the semiconductor chip die pad conductor 12 in the wiring pattern of the circuit board 1. .
[0027]
Thereafter, as shown in FIG. 4, a coating resin layer 31 made of a vinyl-based resin or the like is formed so as to cover the bonding pad conductors 11 and 13 for wire bonding.
The material of the coating resin layer 31 is excellent in heat resistance so as not to seize on the circuit board 1 in the solder reflow process described later, specifically, at a temperature of 230 ° C. for 10 minutes. What has heat resistance of the grade which is not seized on the board | substrate 1 even if heated is preferable. Further, the coating resin layer 31 is selected such that it can be cured at a heating condition in a solder reflow process described later, specifically at a temperature of 130 ° C. to 240 ° C.
[0028]
As a resin satisfying such characteristics, for example, a vinyl resin is suitable, and specific examples of this vinyl resin include strip masks # 448T and # 503B-SHV (Osaka Asahi Chemical Co., Ltd.). .
The resin layer 31 may be formed by a screen printing method (similar to solder paste printing) in which a paste-like resin placed on a screen mask is extruded through the opening of the mask to form the resin layer 31, or in a cylinder. A dispensing method, a stamping method, or the like, in which a resin in a paste state is extruded from the cylinder by air pressure to form the resin layer 31 can be used.
[0029]
Among these methods, the stamping method will be described in detail with reference to FIG. 5. As shown in FIGS. 5A and 5B, a resin coating pattern 32 a is formed on the bottom of the container 32. The container 32 is filled with a paste-like coating resin 33.
Next, the resin coating pattern 32 a of the container 32 is positioned on the wire bonding pad conductors 11 and 13 of the circuit board 1. Next, the coating resin 33 is formed on the circuit board 1 by stamping the coating resin 33. When this stamping is performed, pressure is applied from above the filled resin 33 by the pressing plate 35. Thus, the resin 33 can be easily removed from the coating pattern 32a.
[0030]
In addition, in the application pattern with a large area, when stamping, the problem that the resin 33 is dripped before and after the application pattern is likely to occur. Therefore, as shown in FIG. By providing the mesh 34 in a wide portion, the dripping of the resin 33 can be eliminated.
Next, as shown in FIG. 6, an electronic component 42 such as a semiconductor chip 41 and a capacitor is positioned on the solder paste 21 on the patterns 12 and 20 and mounted (assembled).
[0031]
Next, as shown in FIG. 7, heating in the solder reflow process (for example, temperature: 130 ° C. to 240 ° C., heating time: 3 minutes to 5 minutes)InTherefore, the solder 21 on the wiring pattern is melted to fix the semiconductor chip 41 and the electronic component 42 to the substrate 1, and the coating resin layer 31 is heated and cured by heating in the reflow process.
[0032]
In this reflow process, Br and Cl, which are activators in the solder flux, are eluted or scattered together with the solvent and the resin component in the flux. However, the coating resin is applied on the wire bonding pad conductors 11 and 13. Since the layer 31 is formed, it is possible to prevent the conductors 11 and 13 from being contaminated by the above-described elution or scattering components, and preventing Sn and Pb in the solder from adhering to the wire bonding pad conductors 11 and 13. it can.
[0033]
Next, a cleaning process is performed to clean and remove contaminants such as flux attached to the circuit board 1.
Thereafter, as shown in FIG. 8, the coating resin layer 31 on the wire bonding pad conductor 11 for connecting the semiconductor chip 41 except for the external connection wire bonding pad conductor 13 is peeled off.
[0034]
As the peeling method of the resin layer 31, an adsorption peeling method as shown in FIG. 9 is suitable. This peeling method is a method in which the coding resin layer 31 is adsorbed and peeled off by vacuum. The peeling operation is performed by a claw piece 92 formed at the tip of the vacuum nozzle 91 while sucking the resin layer 31 at the same time that the tip of the vacuum nozzle 91 connected to the vacuum pump (not shown) touches the coding resin layer 31. The coating resin layer 31 is pulled up and peeled upward.
[0035]
Here, the tip of the vacuum nozzle 91 moves along an operation locus refracted as shown by an arrow 93. Further, as described above, since the material of the coding resin layer 31 is selected to have a heat resistance that does not burn onto the substrate 1 under the heating conditions during the solder reflow process, the resin layer 31 can be easily peeled off. Can be done.
As another example of the peeling method of the resin layer 31, there is a method of providing a hook 94 on the coating resin layer 31 as shown in FIG. The hook 94 is made of resin or metal, and is mounted on the coating resin layer 31 on the substrate 1 simultaneously with the mounting component, and the hook 94 is fixed to the coating resin layer 31 when the resin is cured (during solder reflow).
[0036]
Further, instead of providing the hook 94 as a separate part, if a material having a high viscosity is used as the material of the coating resin layer 31 and the projection 95 is formed on a part of the coating resin layer 31 as shown in FIG. The convex portion 95 can play the same role as the hook 94.
Further, as shown in FIG. 12, through-holes 86 are provided in advance in one to several places of the application portion of the coating resin layer 31 in the substrate 1, and the resin layer 31 is projected from the back surface of the substrate 1 when the resin layer is peeled off. There is also a method in which the resin layer 31 is easily peeled off by floating the substrate 31 from the substrate 1.
[0037]
In this manner, wire bonding is performed on the wire bonding pad conductor 11 kept clean as shown in FIG. That is, the semiconductor chip 41 and the semiconductor chip bonding pad conductor 11 are bonded (wire bonding) using an Al (aluminum) wire 43 by a pressure bonding method using both thermocompression bonding and ultrasonic pressure bonding.
[0038]
According to the mounting method of the first embodiment, the wire bonding pad conductors 11 and 13 are covered with the coating resin layer 31 before the solder reflow process of the electronic components 41 and 42, so that the conductors 11 and 13 are solder reflowed. You can avoid being contaminated from time to time. Therefore, the bonding with the wire 43 can be satisfactorily performed while the conductor 11 is kept clean.
[0039]
Moreover, the coating resin layer 31 is left formed on the wire bonding pad conductor 13 for external connection after the mounting process (after the wire bonding of the conductor 11), so that the semiconductor device can be made into a case ( It is possible to prevent the conductor 13 from being oxidized when the adhesive, resin, or the like is cured in a packaging process in which it is fixed (fixed) in the resin and sealed with resin.
[0040]
Here, in the packaging process, the wire bonding pad conductor 13 portion for external connection is not resin-sealed in the case and is left exposed to the outside.
Then, after the packaging process is finished, the coating resin layer 31 on the external connection conductor 13 is peeled off, and then the external connection conductor 13 and the external circuit connection lead (see the lead 100 in FIG. 27) are wire bonded. Moreover, the wire bonding bondability of the external connection conductor 13 can be ensured well.
[0041]
In the process flow shown in FIG. 1, the coating resin layer 31 is applied before the soldering component (semiconductor chip 41, electronic component 42) mounting step. The coating resin layer 31 may be applied later.
FIG. 14 shows the experimental results comparing the bondability when wire bonding is performed by applying the coating resin layer 31 and when wire bonding is performed without the conventional resin layer applying step. The wire used in this experiment is a Φ250 μm Al wire, and the bonding pad conductor is Cu plating. The number of experiments n is 15.
[0042]
The evaluation method of wire bondability is a tensile strength test, and the test method is shown in FIG. The formed bonding wire 150 is cut at the center of the loop (see FIG. 15A), and the wire 150 is erected as shown in FIG. 15B. Next, the wire 150 erected as shown in FIG.Top edgeThen, the wire 150 is pulled upward by the tensile strength measuring instrument 152 until the wire 150 is broken. The graph is a plot of the measured breaking strength at that time.
[0043]
The breaking mode was classified into “peeling” which is a failure mode and “neck break” which is a non-defective mode. Here, “peeling” means peeling at the interface between the conductor as a bonding pad and the wire as shown in FIG. 15 (d), and neck breakage is as shown in FIG. 15 (e). This “peeling” does not occur, and the neck portion 151 of the bonding wire is broken.
[0044]
From this evaluation result, the coating resin layer 31 according to the present invention has a “peeling” in the low breaking strength region of 0, and can provide a stable wire bonding property compared to the case where the resin layer is not applied. It could be confirmed.
In addition, as a material of the coating resin layer 31 used for the evaluation, a strip mask manufactured by Osaka Asahi Chemical Co., Ltd., which is a vinyl resin, was used. However, the material is not limited to this, and is cured under solder reflow conditions. Other resins and films may be used as long as they are heat resistant enough to withstand curing conditions such as adhesives and resins and can be easily peeled off thereafter.
[0045]
In addition, after curing, a resin with less air bubbles (voids), a non-bolus resin, a resin with low oxygen permeability, a resin with less voids on the above-mentioned strip mask of Osaka Asahi Chemical Co., Ltd., By covering the resin with low oxygen permeability and forming the resin layer 31 into two layers, the effect of preventing the conductor under the resin layer 31 from being oxidized can be further enhanced.
[0046]
According to the experimental study by the present inventors, when a circuit board using a Cu thick film as a conductor for a wire bonding pad was actually left in air at 150 ° C. for 10 hours without applying a resin layer, Oxidation was remarkable, and it was found that what was wire-bonded on the conductor often peeled off at low strength when the tensile strength test was conducted.
[0047]
However, when resin (specifically, the strip mask of Osaka Asahi Chemical Co., Ltd.) is applied to the wire bonding pad conductor and the same test is performed, oxidation of the conductor surface is suppressed and high It was confirmed that stable wire bonding could be secured without causing "peeling mode" even in strength.
The inventors further examined the film thickness of the coating resin layer 31 (thickness from the surface of the circuit board 1). In FIG. 16, the experimental result of the tensile strength with respect to the film thickness of the coating resin layer 31 is shown. The test method is the same as that shown in FIG. 15, and the coating resin layer 31 used in the test is the same as that at that time. In addition, the right side shows the case where bonding is performed under optimum conditions for each film thickness in FIG. 16, and the left side shows the case where the power for ultrasonic bonding is slightly reduced.
[0048]
From this evaluation result, when bonding is performed under the optimum conditions, the bonding property is good at any film thickness in the range of 0.1 mm to 2.0 mm of the coating resin layer 31, but the power is slightly reduced. When bonding was performed, “peeling” occurred at a film thickness of 0.3 mm or more. Therefore, it can be seen that there is no allowance for bondability at 0.3 mm or more.
[0049]
Further, FIG. 17 shows the result of the moisture resistance test performed when bonding is performed under the optimum conditions and the film thickness is in the range of 0.05 mm to 0.3 mm. This moisture resistance test is a PCT test that is allowed to stand for 96 hours in an environment of 121 ° C., 1.7 atm and humidity of 85%. From FIG. 17, “peeling” occurred when the thickness of the coating resin layer 31 was 0.05 mm and 0.3 mm. This is presumably because a thick oxide film was formed on the surface of the Cu-based conductor at these film thicknesses, and there was no allowance for bonding properties due to the oxide film.
[0050]
Therefore, it can be seen from the above-described test that the thickness of the coating resin layer 31 is preferably in the range of 0.07 mm to 0.2 mm.
In the embodiment described above, the function and effect of the coating resin layer 31 have been described for the hybrid integrated circuit device in which the semiconductor chip 41 and the electronic component 42 are fixed by solder. However, the semiconductor chip using an adhesive instead of solder is described. 41, even when the electronic component 42 is fixed, the coating resin layer 31 can prevent the wire bonding pads 11 and 13 from being oxidized when the adhesive is cured.
(Second Embodiment)
In the mounting method of the first embodiment, the wire bonding pad conductors 11 and 13 are covered with the coating resin layer 31 before the solder reflow process of the electronic components 41 and 42, so that the conductors 11 and 13 are solder reflowed. It is possible to avoid contamination at times, and the coating resin layer 31 remains formed after the mounting process (after the wire bonding of the conductor 11) on the wire bonding pad conductor 13 for external connection. The conductor 13 is prevented from being oxidized when the adhesive, resin or the like is cured.
[0051]
However, further investigation by the present inventors has revealed that there is a problem that the wire bonding pad conductor 13 under the coating resin layer 31 is oxidized and the bonding property of wire bonding is lowered.
In the packaging process, as shown in FIG. 18, the surface of the conductor 13 is heated by the heating action when the circuit board 1 is bonded to the resin case 52 with an adhesive 51 and is further sealed with resin. It is thought to oxidize. Further investigation on this point revealed that the solder flux that flows out during the solder reflow process is a problem.
[0052]
That is, since the solder flux has good wettability with respect to the circuit board 1, as shown in the plan view of FIG. 19A, around the soldered components (semiconductor chip 41, electronic component 42) during solder reflow. Solder flux 22 flows out. The solder flux 22 melts the coating resin layer 31 and enters the interface between the coating resin layer 31 and the circuit board 1, thereby reducing the adhesion between the coating resin layer 31 and the circuit board 1. Then, when the solder flux 22 is removed in the cleaning process, the coating resin layer 31 is in a floating state. Thereafter, when the heating described above is performed in the packaging process, the surface of the conductor 13 is oxidized.
[0053]
Therefore, in the second embodiment, as shown in FIG. 19B, the soldered component (semiconductor chip 41, electronic component 42) and the coating resin layer are used so that the solder flux 22 does not spread to the coating resin layer 31. A resin layer 36 that forms a dam is formed between the dam 31 and the dam 31.
Therefore, since the solder flux 22 is blocked by the dam resin layer 36, the influence of the solder flux 22 on the coating resin layer 31 can be eliminated, and the conductor 13 can be prevented from being oxidized and bonded onto the conductor 13. It can be performed with good bonding properties.
[0054]
In the present embodiment, the dam resin layer 36 is formed of the same material as the coating resin layer 31 at the same time. That is, in the resin coating process, as shown in FIG. 20, between the conductor 11 and the die pad conductor 12 for mounting the semiconductor chip, between the conductor 11 and the terminal pattern 20 for connecting electronic components, and the terminal pattern. A dam resin layer 36 is formed between 20 and the conductor 13 as a wire bonding pad for external connection. Except for forming the resin layer 36 for the dam, the same steps as in the first embodiment are performed. Note that the resin layer 36 for the dam described above can be coated without being removed.resinLayer 31You may remove sequentially with removal of.
[0055]
From the viewpoint of preventing the conductor 13 from being oxidized as described above, the dam resin layer 36 may be provided only between the terminal pattern 20 and the conductor 13. However, as shown in FIG. 13, when a very thin wire 43 is bonded to the conductor 11, even a slight oxidation of the conductor 11 causes a problem in its bonding property. Therefore, it is preferable to form the dam resin layer 36 between the conductor 11 and the die pad conductor 12 and between the conductor 11 and the terminal pattern 20.
[0056]
Further, the dam resin layer 36 does not need to be formed simultaneously with the formation of the coating resin layer 31, and may be either before or after the formation of the coating resin layer 31. In short, the dam resin layer 36 may be formed before the solder reflow process. Moreover, the resin layer 36 for dams does not need to be the same material as the coating resin layer 31, and may be another material. However, as described above, the manufacturing process becomes simpler when both are simultaneously formed of the same material.
(Third embodiment)
In the second embodiment, the solder flux that flows out during the solder reflow is prevented from reaching the coating resin layer 31 to prevent the conductor 13 from being oxidized. However, the second embodiment is used for cleaning the circuit board 1 after soldering. The coating resin layer 31 is also slightly dissolved by the cleaning liquid (organic solvent-based cleaning liquid), and the coating resin layer 31 becomes hard and discolored during the subsequent heating of the packaging process, and the protective effect on the conductor 13 is reduced. May be oxidized.
[0057]
Therefore, in this embodiment, the coating resin layer 31 is protected from the solder flux and the cleaning liquid. Specifically, as shown in FIG. 21, after the coating resin layer 31 is formed, a protective resin layer 37 is formed on the coating resin layer 31 using a dispenser.
As the protective resin layer 37, a resin excellent in chemical resistance and solvent resistance such as solder flux and cleaning liquid is used. For example, a silicone resin or an epoxy resin can be used. In this case, since the resin layer 37 is firmly fixed to the circuit board 1, when the coating resin layer 31 is peeled off, the resin layer 37 and the coating resin are left with the fixing part of the resin layer 37 and the circuit board 1 left. The layer 31 is peeled off.
[0058]
In the third embodiment, the same steps as those in the first embodiment are performed except that a protective resin layer 37 is formed on the coating resin layer 31.
Therefore, according to the third embodiment, since the protective resin layer 37 is provided on the coating resin layer 31, it is not affected by the solder flux and the cleaning liquid, and on the conductors 11 and 13. Bonding can be performed with good bondability.
[0059]
As shown in the second embodiment, when the configuration is made so as to eliminate the influence of the solder flux on the coating resin layer 31, the coating resin layer 31 is protected only for the cleaning liquid as the material of the resin layer 37. The material to be used can also be selected.
In the present embodiment, the resin layer 37 can be provided only on the coating resin layer 31 on the conductor 13 from the viewpoint of preventing the conductor 13 from being oxidized. However, similarly to the second embodiment, in order to minimize the oxidation of the conductor 11, it is preferable to form the resin layer 37 on the coating resin layer 31 on the conductor 11.
(Fourth embodiment)
In the first to third embodiments described above, the coating resin layer 31 is applied in the resin application process, and the coating resin layer 31 is heated and cured by heating in the reflow process. Since the adhesive force with the circuit board 1 increases when the heating is performed twice, the coating resin layer 31 is heated and cured after the resin coating step as shown in FIG. You may make it implement a mounting process through a printing process.
[0060]
In the heat curing step, heating is performed under the same conditions as in the solder reflow step.
(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described. In the fifth embodiment, a plasma cleaning method is incorporated into the mounting process as a method for cleaning the wire bonding pad conductor, and FIG. 23 is a flowchart showing the mounting process when this plasma cleaning method is introduced. is there.
[0061]
The resin layer coating process in the first embodiment protects the bonding pad conductor from contamination and oxidation, whereas the plasma cleaning process in the fifth embodiment adheres during solder reflow and resin / adhesive curing. By removing contaminants (Br, Cl, Sn, etc.) and oxides to be cleaned, a clean surface is secured on the wire bonding pad conductor to ensure stable wire bonding.
[0062]
Specifically, as shown in FIG. 23, after the solder reflow and cleaning process, a plasma cleaning method is performed on the wire bonding pad conductor 11 for connecting the semiconductor chip 41, so that contaminants attached during solder reflow ( Br, Cl, Sn, etc.) and oxides are removed, and then wire bonding to the conductor 11 is performed.
Next, a packaging process is performed for bonding the substrate 1 and a case (not shown) for housing and fixing the substrate 1 and curing the resin, and then a plasma cleaning method for the wire bonding pad conductor 13 for external connection. After removing the contaminants, oxides and the like adhering at the time of solder reflow and bonding and curing in the package process, wire bonding to the conductor 13 is performed.
[0063]
The plasma cleaning method in the fifth embodiment is, for example, 10% -H as the discharge gas.₂/ Ar is used to generate reactive gas plasma on the conductors 11 and 13 to remove contaminants and oxides on the conductors 11 and 13.
Also, as shown in FIG. 24, during the plasma cleaning process, the mounting component (semiconductor chip 41 and the like) is covered with a mask 170 to avoid adverse effects on the semiconductor chip 41 and the like, and the bonding pad conductor 11. It is desirable to clean only 13.
[0064]
This is because when the plasma cleaning process is performed, the mounting component (semiconductor chip 41 or the like) is mounted on the substrate 1, so there is a concern that the characteristics of the mounting component may vary due to plasma cleaning. Therefore, it is desirable to cover the mounted components with the mask 170 to avoid adverse effects on the mounted components such as the semiconductor chip 41.
As a material for the mask 170, a metal material such as Al or stainless steel that does not interfere with plasma cleaning is selected. The mask 170 is provided with a buffer member 172 made of a soft resin (silicone resin or the like) at a contact portion with the substrate 1. By providing the buffer member 172, it is possible to prevent a gap due to warpage of the substrate 1 from being generated between the mask 170 and the substrate 1 and to prevent the substrate 1 from being damaged by the mask 170.
[0065]
25 and 26 show specific examples of the effect of removing contaminants (Br, Sn) adhering to the conductors 11 and 13 at the time of solder reflow. On the Cu conductor that has been solder-reflowed but not plasma-cleaned. As shown in the upper part of FIG. 25, Br and Sn were confirmed by surface analysis. However, after plasma cleaning according to the fifth embodiment, it was confirmed that these Br and Sn were completely removed. .
[0066]
Therefore, as shown in FIG. 26, the wire bonding property was confirmed to be good because the plasma-cleaned product did not have the “peeling mode”. This contaminant cannot be removed in the conventional cleaning time (30 to 180 sec), and the contaminant can be removed by cleaning for a long time of 10 to 15 minutes.
[0067]
In the fifth embodiment, when the semiconductor chip 41 or the like is fixed to the substrate 1 using an adhesive, the surfaces of the wire bonding conductors 11 and 13 are oxidized when the adhesive is cured. These oxides can also be suitably removed by a plasma screening method.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a mounting method according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a circuit board having a wiring pattern used in the first embodiment.
3 is a cross-sectional view showing a state in which a solder paste is printed on the circuit board of FIG. 2;
4 is a cross-sectional view showing a state in which a coating resin layer is applied to the circuit board of FIG. 3;
5A is a cross-sectional view of a container used in the coating resin layer application step of FIG. 4, and FIG. 5B is a plan view of the bottom of the container.
6 is a cross-sectional view showing a state in which an electronic component is mounted on the circuit board of FIG.
7 is a cross-sectional view showing a state after performing a solder reflow process on the circuit board of FIG. 6;
8 is a cross-sectional view showing a state after a coating resin layer on a semiconductor chip connecting conductor is peeled from the circuit board of FIG.
9 is a cross-sectional view showing a method for peeling the coating resin layer in FIG. 8. FIG.
FIG. 10 is a cross-sectional view showing another example of a method for peeling a coating resin layer.
FIG. 11 is a cross-sectional view showing another example of a method for peeling a coating resin layer.
FIG. 12 is a cross-sectional view showing another example of a method for peeling a coating resin layer.
13 is a cross-sectional view showing a state after wire bonding to a semiconductor chip connecting conductor in the circuit board of FIG. 8;
FIG. 14 is a chart showing evaluation results of wire bonding properties with and without a coating resin layer.
FIG. 15 is an explanatory diagram showing a tensile strength test method for evaluating wire bonding properties.
FIG. 16 is a diagram showing a test result of a tensile strength with respect to a film thickness of a coating resin layer.
FIG. 17 is a diagram showing the results after a PCT test of the tensile strength with respect to the film thickness of the coating resin layer.
FIG. 18 is a diagram showing a state in which a circuit board is bonded to a case with an adhesive in a packaging process.
19A is a view showing a state where the solder flux spreads to the coating resin layer, and FIG. 19B is a view showing a state where the solder flux is stopped by the dam resin layer.
FIG. 20 is a view showing a state in which a dam resin layer is provided between a coating resin layer and a soldered part in the second embodiment of the present invention.
FIG. 21 is a view showing a state in which a protective resin layer is formed on a coating resin layer in the third embodiment of the present invention.
FIG. 22 is a flowchart showing a mounting method according to the fourth embodiment of the present invention.
FIG. 23 is a flowchart showing a mounting method according to the fifth embodiment of the present invention.
FIG. 24 is a cross-sectional view showing a mask used when performing the plasma cleaning method of the fifth embodiment.
FIG. 25 is a chart showing the analysis results of the conductor surface before and after performing the plasma cleaning method.
FIG. 26 is a chart showing evaluation results of wire bonding properties depending on whether or not a plasma cleaning method is performed.
FIG. 27 is a cross-sectional view showing a mounting structure using conventional wire bonding.
FIG. 28 is a flowchart showing a mounting method using conventional wire bonding.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Circuit board 11, 12, 13, 20 ... Cu-type conductor, 21 ... Solder paste,
22 ... solder flux, 31 ... coating resin layer, 36 ... resin layer for dam,
37 ... Protective resin layer, 41 ... Semiconductor chip, 42 ... Electronic component,
52 ... Case, 100 ... Lead for external circuit connection.

Claims (5)

The electronic components (41, 42) are fixed to the Cu-based conductors (12, 20) constituting the wiring pattern on the circuit board (1) by soldering or adhesive, and other Cu constituting the wiring pattern. A mounting method in which wire bonding is performed directly on the system conductor (11) to connect the Cu system conductor (11) and the electronic component (41).
After coating the Cu-based conductor (11) to be wire bonded to the electronic component (41) with the resin layer (31), the electronic component (41, 42) is fixed by soldering or an adhesive,
Thereafter, the coating resin layer (31) is peeled off,
After this, the mounting method of the electronic component wire bonding the Cu-based conductor (11) and the electronic component (41) from which the coating resin layer (31) has been peeled off,
A paste-like resin (33) for forming the coating resin layer (31) is stored in a container (32) having a resin coating pattern (32a) formed on the bottom,
Positioning the resin coating pattern (32a) of the container (32) and the Cu-based conductors (11, 13) for wire bonding of the circuit board (1),
Thereafter, the resin (33) in the form of paste is discharged through the resin coating pattern (32a) at the bottom of the container (32), and the resin layer (31) is formed on the Cu-based conductors (11, 13) for wire bonding. ) Coating method for electronic parts. The electronic components (41, 42) are fixed to the Cu-based conductors (12, 20) constituting the wiring pattern on the circuit board (1) by soldering or adhesive, and other Cu constituting the wiring pattern. A mounting method in which wire bonding is performed directly on the system conductor (11) to connect the Cu system conductor (11) and the electronic component (41).
After coating the Cu-based conductor (11) to be wire bonded to the electronic component (41) with the resin layer (31), the electronic component (41, 42) is fixed by soldering or an adhesive,
Thereafter, the coating resin layer (31) is peeled off,
After this, the mounting method of the electronic component wire bonding the Cu-based conductor (11) and the electronic component (41) from which the coating resin layer (31) has been peeled off,
The coating resin layer (31) is sucked by a vacuum nozzle (91) to which a vacuum is applied, and the tip of the vacuum nozzle (91) is locked to the coating resin layer (31), whereby the coating resin A method for mounting an electronic component, wherein an external force in a direction away from the circuit board (1) is applied to the layer (31) to peel off the coating resin layer (31). The electronic components (41, 42) are fixed by soldering to the Cu-based conductors (12, 20) constituting the wiring pattern on the circuit board (1), and other Cu-based conductors ( 11) a mounting method in which wire bonding is performed directly on the Cu-based conductor (11) and the electronic component (41).
After coating the Cu-based conductor (11) to be wire bonded to the electronic component (41) with the resin layer (31), the electronic component (41, 42) is fixed by soldering,
Thereafter, the coating resin layer (31) is peeled off,
After this, the mounting method of the electronic component wire bonding the Cu-based conductor (11) and the electronic component (41) from which the coating resin layer (31) has been peeled off,
A protective layer (37) for protecting the coating resin layer (31) from a cleaning solution used for cleaning the circuit board (1) after the soldering is applied to the coating resin layer (31) before the soldering. A method for mounting an electronic component, comprising: The electronic components (41, 42) are fixed to the Cu-based conductors (12, 20) constituting the wiring pattern on the circuit board (1) by soldering or an adhesive, and other components constituting the wiring pattern are configured. A mounting method in which wire bonding is performed directly on a Cu-based conductor (11) to connect the Cu-based conductor (11) and the electronic component (41).
After the electronic components (41, 42) are fixed by soldering or adhesive, a plasma cleaning process is performed on the Cu-based conductor (11) in which wire bonding with the electronic components (41) is performed. The surface of the Cu-based conductor (11) is cleaned,
Thereafter, the plasma-cleaned Cu-based conductor (11) and the electronic component (41) are wire-bonded. The electronic components (41, 42) are fixed to the Cu-based conductors (12, 20) constituting the wiring pattern on the circuit board (1) by soldering or an adhesive, and other components constituting the wiring pattern are configured. In a mounting method in which wire bonding is performed directly on the Cu-based conductors (11, 13), and the Cu-based conductors (11, 13) are connected to the electronic component (41) and the external circuit connecting lead (100). There,
After the electronic parts (41, 42) are fixed by soldering or using an adhesive, wire bonding with the electronic parts (41) of the Cu-based conductors (11, 12, 13, 20) is performed. A plasma cleaning process is performed on the Cu-based conductor (11) to clean the surface of the Cu-based conductor (11),
Thereafter, wire bonding of the Cu-based conductor (11) and the electronic component (41) that have been subjected to the plasma cleaning,
Thereafter, a packaging process for sealing the circuit board (1) in a case is performed.
Thereafter, a plasma cleaning step is performed on the Cu-based conductor (13), which is wire-bonded to the external circuit connecting lead (100), among the Cu-based conductors (11, 12, 13, 20). The surface of this Cu-based conductor (13) is cleaned,
Thereafter, the plasma-cleaned Cu-based conductor (13) and the external circuit connecting lead (100) are wire-bonded.

Images