JP2013093370A - Die bonder device and die bonding method - Google Patents

Abstract

【Task】
Disclosed are a die bonder capable of reducing voids in solder joints and interface bonding defects, and a die bonding process using the die bonder.
[Solution]
In a die bonder for joining a semiconductor chip to a lead frame or a substrate with a solder, a transport unit for transporting the lead frame or the substrate, a solder supply unit for supplying solder onto the lead frame or the substrate, the lead frame, Alternatively, a surface cleaning device that includes a mounting portion for mounting and joining a semiconductor chip to solder on the substrate, and after removing the oxide film on the solder surface melted in the furnace after supplying the solder onto the lead frame or the substrate. The die bond quality is improved by the die bonder equipment characterized by having the conversion unit.
[Selection] Figure 1

Description

  The present invention relates to a die bonder apparatus and a die bonding method.

  Generally, a semiconductor device using a lead frame has a semiconductor chip mounted on a land portion of the lead frame, and the electrodes of the semiconductor chip and the electrodes of the lead frame are electrically connected by a technique such as wire bonding. Thereafter, the periphery of the semiconductor chip and the wiring portion such as the wire bonding is molded with resin, and the lead frame portion outside the resin portion is cut into a predetermined lead shape to obtain individual semiconductor devices.

  In a semiconductor device, an adhesive is often used to connect the lead frame and the semiconductor chip. However, in a semiconductor device that handles a large current, a large power, etc., heat generated in the semiconductor chip is transmitted to the land portion to be external to the semiconductor device. Since it is necessary to efficiently release heat, generally, the semiconductor chip and the lead frame are joined using solder having better thermal conductivity than the adhesive.

  A die bonder device in which a semiconductor chip is mounted on a lead frame and joined using solder is disclosed in Japanese Unexamined Patent Publication No. 2000-216174 (Patent Document 1). The content disclosed here is a die bonder that mounts semiconductor pellets on a lead frame via solder. Before mounting the semiconductor pellets, the molten solder is moved up and down and stirred using a stirring rod that rotates around an axis. However, in order to shorten the work time, there is a problem that when the operating speed of the apparatus is increased, the stirrer scatters the molten solder, which is solved.

  As a solution, a solder supply unit that supplies a certain amount of solder to a lead frame that is heated and intermittently moved on a guide rail covered with a cover, and a solder agitation unit that agitates solder melted on the lead frame with a stirring rod And a die bonder in which semiconductor pellet supply parts for supplying semiconductor pellets on the molten solder thus stirred are sequentially arranged, and means for heating at least the surface of the stirring rod that contacts the molten solder is provided.

  Japanese Patent Laid-Open No. 2009-283705 (Patent Document 2) discloses a die bonder in which an ultrasonic vibrator that can be vibrated in a direction parallel to the surface of a lead frame is provided on a solder stirrer to reduce voids in a joint. Is disclosed.

  In addition, when supplying solder, it is possible to supply solder from the solder supply nozzle to the lead frame through the solder melting arm and diffuse the solder oxide film inside the solder without concentrating on the surface. A die bonder device is disclosed in Japanese Patent Laid-Open No. 2001-176893 (Patent Document 3).

  Japanese Patent Laid-Open No. 2008-192965 (Patent Document 4) discloses a needle-like point to ensure solder wettability even when an oxide film is generated on the molten solder surface after supplying the solder. A method is shown in which a jig having a needle portion is pierced into the oxide film on the solder surface and stirred to destroy and remove the oxide film. Patent Document 4 also discloses a method of spraying a reducing agent such as flux or reducing gas.

  As semiconductor devices using members other than lead frames, in power semiconductors, power modules, etc., a semiconductor device such as a connection between a heat dissipation base substrate mainly made of a copper-based material and an insulating substrate, or an insulating substrate and a diode. Are connected by solder connection of a large area, and the same die bonding process as described above can be applied. In these large-area solder joints, it is important to reduce voids in the solder joints in order to ensure performance and reliability.

  As a method for performing solder bonding of a large area other than the above, a solder paste is supplied to a lead frame or a substrate by printing or a dispenser, a semiconductor chip is mounted on this, and then placed in a heating furnace to melt the solder, A process of joining a lead frame or a substrate and a semiconductor chip is often used. In this process, a vacuum reflow furnace that can evacuate the furnace is often used as the heating furnace. That is, the solder paste is first melted to ensure the wetness of the member by the reducing action of the organic components, and then the whole is evacuated to eliminate voids from the joint. Thereafter, the whole is cooled, but after cooling, a flux residue remains and often involves a cleaning step.

JP 2000-216174 A JP 2009-283705 A JP 2001-176893 A JP 2008-192965 A

  However, in the known examples of the die bonder already disclosed above, after the solder is supplied, the oxide film on the surface of the solder is broken and dispersed with a stirring rod or the like, or the solder oxide film is soldered when the solder is supplied. It was a process in which an oxide film was left at the junction only by diffusing inside.

  When these oxide films remain at the interface, wetting between the solder and the material to be joined is hindered, causing voids and causing defective bonding such as the oxide film being sandwiched. Further, even when the oxide film is dispersed inside the solder, it is not removed, which leads to voids inside the solder. Furthermore, the mechanical properties and heat conduction properties of the solder are also deteriorated.

  As described above, the generation of voids and poor bonding at the interface lead to an increase in the thermal resistance of the solder connection portion and a decrease in heat dissipation, causing a problem that necessary performance as a semiconductor device cannot be ensured. Also, the bonding strength is reduced. For this reason, thermal fatigue characteristics deteriorate and long-term reliability cannot be ensured. These large-area soldered semiconductor devices are generally used for power semiconductors and power modules. In addition to semiconductor devices for home appliances such as air conditioners and personal computers, they are used in automobile equipment, railways, industrial equipment, etc. The quality of solder joints that affect the performance and reliability is very important. In the future, power semiconductors will also need to be miniaturized, and in order to reduce thermal resistance, the solder will tend to be thinner, and it will be important to control voids in die-bonded joints and ensure wetting. ing.

  Further, although there is a description regarding a method of removing the oxide film by treating the solder surface melted in the furnace with a reducing gas, the treatment of the reaction product in the removal process is not considered. If these reaction products are not efficiently removed, the surrounding members and the inside of the furnace are contaminated, and the quality is deteriorated at portions other than the joint portion at the joint interface. In addition, when hydrogen plasma or the like is used as the reducing gas, the amount of gas required for plasma processing may increase and the cost may be higher than in a normal furnace atmosphere.

  On the other hand, in the joining method using solder paste, the cause of void generation is thought to be due to the volatilization of the solvent component and the reaction product of the solder and the organic component being generated as a decomposition gas. Vacuuming is performed in a vacuum reflow furnace. However, batch processing is necessary to pull the vacuum, and flux residue remains after cooling, which necessitates a cleaning process, which lengthens the manufacturing process and hinders cost reduction. Yes.

  In view of the above, there is a need for a no-bonding die-bonding process that reduces voids in the joint or reduces bonding failure at the interface, and a die bonder facility that realizes this. Moreover, the equipment which can reduce the cost of a process is required.

In order to solve the above problems, for example, the configuration described in the claims is adopted.
The present application includes a plurality of means for solving the above-mentioned problems. To give an example, in a die bond that joins a plurality of members to be joined by forming solder joints in an atmosphere in a furnace, The solder supplied to the member is reduced and removed from the surface oxide film using gas, and then supplied to the member to be joined, and the gas containing the reaction product generated by the reduction is removed from the exhaust port provided in the vicinity. .

  According to the present invention, since the oxide film amount of the solder supplied to the lead frame or the substrate has already been reduced at the time of joining the semiconductor chip, voids are generated at the solder joint portion with the semiconductor chip, and the solder And wetting defects at the interface between the member and the member to be joined can be suppressed. That is, when the solder oxide film remains at the interface, voids are generated at the interface between the solder and the material to be joined, or the bonding is poor. However, these problems can be prevented.

  Therefore, heat dissipation of the solder connection portion can be ensured, and performance required as a semiconductor device can be obtained. Moreover, since voids can be reduced, bonding strength can be ensured, and long-term reliability can be guaranteed. In addition, the shape of the fillet around the semiconductor chip is improved, and the mechanical strength can be ensured.

  Furthermore, since a cleaning step after cooling is not required as compared with a method using a conventional solder paste, a high-quality die bond joint can be obtained without cleaning.

  Further, the amount of hydrogen used can be reduced, and the processing cost can be reduced.

It is a figure which shows the principal part of the die bonder of this invention. It is a figure which shows the example of the surface cleaning unit of this invention. It is the figure which showed typically a mode when a void and a wetting defect arise. It is a figure which shows the defective part of a fillet shape. It is the figure which showed typically the die-bonding connection part after processing with the solder surface cleaning unit of this invention. It is a figure which shows hydrogen concentration distribution in the die bonder furnace of this invention. It is a figure which shows the principal part of another die bonder of this invention. It is a figure which shows the principal part of another die bonder of this invention. It is a figure which shows the principal part of another die bonder of this invention. It is a figure which shows the example of another surface cleaning unit of this invention. It is a figure which shows the example of another surface cleaning unit of this invention. It is a figure which shows the principal part of the conventional die bonder. It is a figure which shows the example of another surface cleaning unit of this invention. It is a figure which shows the example of the die bonder apparatus which partitioned off the surface cleaning process and other processes with the wall.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  FIG. 1 is an enlarged view of a main part of a die bonder having a solder surface cleaning unit of the present invention. This die bonder 1 has a guide frame 4 for intermittently moving a lead frame or substrate 3 as a member to be joined in a furnace covered with a cover 2 in order to block outside air, and the lead frame or substrate 3 has four open windows 6a, 6b, 6c, 6d at predetermined positions on the upper surface of the cover (furnace) 2 along the moving direction 5 of the cover 3. If it demonstrates along a die-bonding process, a 1st process is a supply process of a solder, and will supply the elongate wire solder 7 to the lead frame or the board | substrate 3 through the opening window 6a. Explaining this process in detail, the wire solder 7 delivered from the solder supply nozzle 9 comes into contact with the lead frame or the substrate 3 whose lower surface is heated by the heater 8, and the tip of the wire solder 7 is melted to lead. The frame or the substrate 3 is wetted and solder is supplied (supplied solder 10).

  In the second step of the die bonder of the present invention shown in FIG. 1, the solder forming rod 11 descends from the opening window 6 b and pushes the supplied solder 10, and wets and spreads in a desired shape on the lead frame or the substrate 3. (Wet spread solder 12).

  In the third step, the surface cleaning unit 13 installed in the opening window 6c removes or reduces the oxide film on the surface of the solder 12 that has spread to a desired shape on the lead frame or the substrate 3. (Solder 14 subjected to surface cleaning treatment). Therefore, the amount of Sn oxide film on the surface of the solder 14 subjected to the surface cleaning process is significantly reduced as compared with the method without the conventional surface cleaning unit 13.

  In the fourth step, the collet 16 that has adsorbed the semiconductor chip 15 descends, and the semiconductor chip 15 is mounted and bonded to the solder 14 that has spread out. As a result, the semiconductor chip 15 is joined to the lead frame or the substrate 3 via the solder connection portion 17. As the quality of these die bond joints 17, the void ratio (volume ratio of bubbles contained per unit volume of molten solder) can be suppressed as compared with the conventional method. The void ratio can be measured by an X-ray observation apparatus, an ultrasonic flaw detection apparatus, or the like.

  For comparison, a conventional die bonder device 120 is shown in FIG. 12, but three opening windows 6a, 6b, 6d are provided at predetermined positions on the upper surface of the cover (furnace) 2 along the moving direction 5 of the lead frame or substrate 3. It is what you have. In the first step, the wire solder 7 sent out from the solder supply nozzle 9 contacts the lead frame or the substrate 3 whose lower surface is heated by the heater 8, and the tip of the wire solder 7 is melted to lead the lead frame or The substrate 3 is wetted and solder is supplied (supplied solder 10). In the second step, the solder forming rod 11 wets and spreads in a desired shape (wet spread solder 12), and in the third step, the collet 16 adsorbing the semiconductor chip 15 descends and becomes wet spread solder 12. Although the semiconductor chip 15 is mounted and bonded (solder 121 at the bonding portion), in the conventional method, the oxide film existing on the wet solder 12 remains as it is at the interface with the semiconductor chip 15 or inside the solder 121. This is completely different from the present invention.

  In the die bonder apparatus of the present invention shown in FIG. 1, in order to further improve the quality of the solder joint (die bond quality), in the second step, the solder forming rod 11 is lowered from the opening window 6b, and the solder is desired. When wetting and spreading the shape, wetting may be promoted by applying vibrations such as ultrasonic waves within a range where solder does not scatter to unnecessary portions. Further, wetting can be promoted even if the lead frame or the substrate 3 is displaced several times in the horizontal direction, the vertical direction, or the rotational direction. In addition, it is possible to improve the quality by providing a groove or a recess at the tip of the forming rod 11 so that the solder can easily spread into a desired shape, and a heating function so as not to lower the solder fluidity. Can be made.

  Further, in the step of mounting and bonding the semiconductor chip 15 in the fourth step, wetting may be promoted by operating with an amplitude that does not shift in the x, y, and z directions, or by applying ultrasonic vibration or the like. Good. Thereby, quality improvement can be expected. Further, in order to further eliminate the influence of the oxide film on the surface, the semiconductor chip 15 may be made to enter from a substantially lateral direction in parallel with the lead frame or the surface of the substrate 3. As a result, the oxide film can be mounted while being excluded at the edge of the tip of the semiconductor chip. Alternatively, the collet 16 may have a collar shape, and the oxide film may be excluded from the joint using the collar of the collet 16. This can also be expected to improve quality.

  Since these processes are fluxless processes using no flux, the portion (furnace) covered with the cover 2 in the die bonder 1 is shielded from the outside air (atmosphere) in order to make the solder surface difficult to oxidize. The atmosphere inside the cover (furnace) 2 should be filled with nitrogen or a mixed gas of nitrogen and hydrogen, and the oxygen concentration remaining inside should be kept as low as possible. For this reason, it is important to reduce the entry of oxygen from the outside by reducing the shapes of the lead frame or the entrance 18 and the exit 19 inside the cover (furnace) 2 of the substrate 3 as much as possible.

  An example of the solder surface cleaning unit 13 is shown in FIG. 2, and plasma processing is performed on the surface of the molten solder 12 on the lead frame or the substrate 3 by using a nozzle 21 at atmospheric pressure. The nozzle 21 is mainly composed of a counter electrode 22 and a dielectric 23, and a power source 24 is connected to the electrodes. A processing gas is introduced from a gas introduction port 25, and a plasma 26 is generated by applying an electric field between electrodes by a power source 24. The material of the dielectric 23 is glass, quartz glass, alumina or the like, but is not limited thereto.

  Here, a mixed gas of nitrogen and hydrogen used as the atmosphere of the present plasma apparatus was used as the processing gas. The higher the hydrogen concentration, the higher the ability to clean the surface, but an explosion-proof structure is required and the cost is high. Therefore, it is desirable to use a hydrogen concentration of about 4% below the explosion limit. The hydrogen plasma generated in this way is used to treat the surface of the molten solder 12, and at this time, a reaction product is generated.

Of the oxide film on the solder surface, the reaction formula for SnO2 is shown:
(Chemical formula 1)
SnO2 + 4H * → Sn + 2H2O
Thus, tin oxide mainly present on the surface of the solder is reduced to Sn, but H2O is generated in the furnace.

  If these products are left as they are, the lead frame or the periphery of the substrate 3 is contaminated, and if it is continuously processed, the furnace interior 2 is also contaminated. Therefore, the exhaust port 27 is disposed in the vicinity of the nozzle 21.

  The exhaust port 27 is not simply exhausted naturally by a tube for ventilation to the outside of the cover (furnace) 2, but forced exhaust by suction with an impeller or the like is more effective in removing reaction products. . Even if it processes continuously by this, quality degradation will not be caused.

  In the example of FIG. 2, the exhaust port 27 is disposed in the vicinity of the nozzle 21 of the surface cleaning unit 13. However, as in the example of FIG. 13, the exhaust port 27 is provided in a ring shape surrounding the outer periphery of the nozzle 21. It may be a body structure. That is, plasma is generated in the central portion of the nozzle, and a hole through which the plasma is ejected toward the lead frame or the substrate 3 is opened, and an exhaust port 27 is continuously installed on the outer periphery. The reaction product is sucked in, has an integral structure, and is compact in shape.

  Next, the reason for reaching such an invention will be described. Conventionally, a large number of void defects have been observed in large-area solder joints by die bonding. It has been estimated that the main cause of this void is that oxygen remains even when the die bonder furnace is filled with nitrogen or a mixed gas of nitrogen and hydrogen, and the solder is oxidized by this residual oxygen. Therefore, die bonding experiments were performed on a semiconductor chip as a substrate under various oxygen concentration conditions. As a result, it was found that the surface oxide film of the wire solder 7 supplied to the lead frame or the substrate 3 is involved in the generation of voids. The result is shown in FIG.

  FIG. 3 is a schematic view of solder wetting in the case of a conventional die bonding process. The normal wire solder 7 has a difference in thickness depending on the solder material, manufacturing conditions, and storage conditions, but an oxide film 47 always exists on the surface. Accordingly, the wire solder comes into contact with the lead frame or the substrate 3 in the first step, and when the molten solder is supplied, the oxide film 41 derived from the wire solder 7 is placed on the supplied solder 10. I understood it. Then, even if the solder 10 supplied to the lead frame or the substrate 3 is pushed and spread by the solder forming rod 11 in the next step, basically, the oxide film 42 remains on the wet spread solder 12. It was.

  Usually, in the die-bonding process, nitrogen or a mixed gas of nitrogen and hydrogen is used as the atmospheric gas, and the oxygen concentration in the portion (furnace) covered with the cover 2 is controlled to be low. On the other hand, a composition often used as a solder material is a solder mainly composed of Sn, and the surface of the solder is usually covered with an Sn oxide film. However, it is desirable that the Sn oxide film is stable, and the die bonding process is performed in as short a time as possible in order to secure the number of production per unit time, so that the time that can be maintained at a high temperature is short, It was found that even in an atmosphere where hydrogen is mixed, the reduction of the oxide film cannot be expected so much at about 200 ° C. to 300 ° C. at which the solder joins. Therefore, the oxide film 42 is always left on the wet spread solder without being removed. For this reason, even if the semiconductor chip 15 is mounted and bonded to this, the bonding is inhibited by the oxide film 42. That is, it was found that the oxide film 42 is partially broken and dispersed (the broken and dispersed oxide film 45), but leads to the void 43 and the wetting defect 44.

  Even if the surface of the solder 12 that has spread out is agitated or the semiconductor chip 15 is mounted, the oxide film 42 is promoted to break and disperse even if the device is applied with ultrasonic vibrations. Cannot be removed and remains in the bonding layer. Further, when the amount of residual oxygen in the furnace is large, the oxide film 42 remaining on the solder surface hinders the smooth fillet formation around the semiconductor chip 15, and as shown in FIG. It turned out to be.

  Summarizing the above study results, reduction and removal of the Sn oxide film on the solder surface is not expected much in the reducing atmosphere containing hydrogen in the vicinity of the normal soldering temperature and each processing time in the normal mass production process. Can not. Further, even if the oxide film remaining on the surface is mechanically destroyed and dispersed in the subsequent process, it remains in the solder joint, causing voids, poor wetting, and poor fillet shape. In general, once the oxide film is removed from the solder, an oxide film is immediately formed if oxygen is present in the surrounding area. The oxide film grows easily as the temperature increases. Accordingly, it has been found that it is important to remove the oxide film 42 on the surface of the molten solder 12 immediately before mounting and joining the semiconductor chip 15 in order to ensure die bond quality.

  For this reason, the solder cleaning unit 13 is provided immediately before the semiconductor chip 15 is mounted on and joined to the molten solder 12. At this time, as a method for removing the oxide film, it was found that a mechanical method is not effective because a residue remains in the joint, and a method in which the residue does not remain in the joint is necessary. It is important to eliminate the influence of the reaction product.

  Next, using such a solder surface cleaning unit 13, the quality is improved by a die bonding process in which the surface of the molten solder 12 is processed immediately before the semiconductor chip is bonded to and mounted on the lead frame or the substrate 3. Will be explained.

  FIG. 5 shows the change of the solder oxide film in the die bonding process when the surface cleaning unit 13 is used. The oxide film 47 remaining on the surface of the wire solder 7 remains as the oxide film 41 on the melted solder 10 when the wire solder is supplied to the lead frame or the substrate 3, and then in the spanker process which is the second process. Although it remains on the surface of the molten solder 12 as the oxide film 42, the amount of the surface oxide film of the solder 14 is greatly reduced when passing through the solder surface cleaning unit 13. For this reason, when the semiconductor chip 15 is mounted and bonded to the solder 14 having a small oxide film in the fourth step in this way, voids and wetting defects are difficult to occur in the bonded portion, and a high-quality bonded portion is obtained. be able to.

  Another effect of the present invention will be described. The plasma treatment which is an example of the surface cleaning unit 13 can effectively remove and reduce the oxide film on the surface of the solder 12 which is melted before the semiconductor chip 15 is mounted and bonded. This eliminates the need for maintaining the residual oxygen concentration and the hydrogen concentration at high levels throughout the furnace. Generally, the gas flow rate and the device structure are considered so that the residual oxygen concentration is about 200 ppm or less, and the hydrogen concentration is about 4% or less below the explosion limit. However, in order to keep hydrogen at about 4% throughout the furnace, the amount of gas used during the operation of the equipment is large, which hinders cost reduction. However, in the present invention, even if the residual oxygen concentration in the furnace is high and the solder surface is somewhat oxidized, it can be reduced by the surface cleaning unit 13 installed immediately before the semiconductor chip 15 is mounted and bonded. It doesn't matter.

  Since hydrogen is required for the plasma processing, a mixed gas of hydrogen and nitrogen is introduced from the gas inlet 25 of the nozzle 21 of the surface cleaning unit 13 to concentrate the hydrogen in the plasma processing portion. The concentration of can be suppressed. For this reason, if it sees in the whole furnace, the usage-amount of hydrogen can be reduced. As a result, the hydrogen gas concentration distribution is obtained in the die bonder furnace. FIG. 6 shows the hydrogen concentration distribution when the die bonder device is viewed from above. The hydrogen concentration is indicated by the contour line 61. The hydrogen concentration is shown to decrease as it goes from a to e. That is, although the hydrogen concentration was set to the highest around 4% in the vicinity of the opening window 6c, the hydrogen concentration was low in the vicinity of the entrance 18 and the exit 19 of the conveyor, and the total amount of hydrogen used could be reduced. Further, since the hydrogen concentration is low on average, it is advantageous in terms of safety.

  Here, one surface cleaning unit 13 is installed per die bonder facility, but a plurality of surface cleaning units 13 may be arranged. For example, as shown in FIG. 7, the processing nozzle 72 of the surface processing unit 13 is installed between the first process and the second process, and the surface of the solder 10 supplied to the lead frame or the substrate 3 is processed once. The surface of the molten solder 14 is again cleaned before the step of mounting and joining the semiconductor chip 15. By making the process into two steps, the time required to pass through the conveyor in the furnace can be effectively used, and the cleaning can be surely performed and the quality can be improved. At this time, although not shown, by installing an exhaust port as shown in FIGS. 2 and 13 in the vicinity of the processing nozzles 72 and 73, contamination in the furnace is prevented and long-term stable quality is ensured. It is valid.

  As another method, as shown in FIG. 8, in the step of supplying the first wire solder, the surface cleaning nozzle 74 is installed to clean the surface of the substrate and the supplied solder surface. These processes can be performed simultaneously, which is effective in improving quality. Although not shown in FIG. 8, by installing an exhaust port as shown in FIGS. 2 and 13 in the vicinity of the processing nozzles 73 and 74, contamination in the furnace is prevented and long-term stable quality is ensured. It is effective for securing.

  As another method, as shown in FIG. 9, in the third step of mounting and bonding the semiconductor chip 15 to the lead frame or the solder 12 supplied to the substrate 3, the processing nozzle 74 of the surface cleaning unit 13 is provided. It is also possible to install. As a result, the device area can be reduced. If the apparatus can be downsized, the amount of atmospheric gas used in the furnace can be reduced, and the cost can be reduced.

  From the above, by using the die bonder apparatus having the surface cleaning unit 13, it is possible to reduce voids as defects in solder joints with no contamination in the furnace over a long period of time, low hydrogen consumption, and low cost. is there.

  An example of another solder surface cleaning unit 13 is shown in FIG. 10, and plasma processing is performed on the surface of the solder 12 on the lead frame or the substrate 3 using a torch type nozzle 31 at atmospheric pressure. Is. In the torch type nozzle 31, a center electrode 33 is disposed at the center of the counter electrode 32, and an insulator 34 is provided on each electrode surface. A high frequency power source 35 is connected to the center electrode 33. A processing gas is supplied from a gas inlet 36 to generate plasma in the discharge space 37 and irradiate a nozzle-shaped plasma 39 from a gas outlet 38. As the processing gas, a mixed gas of nitrogen and hydrogen used as the atmosphere of the plasma apparatus was used. As a result, hydrogen plasma is generated, and the oxide film present on the surface of the molten solder 12 on the lead frame or the substrate 3 can be reduced.

  At this time, reaction products are generated. If these are left untreated, the lead frame or the periphery of the substrate 3 is contaminated, and if the processing is continuously performed, the inside of the furnace is also contaminated. Arranged. Even if it processes continuously by this, quality degradation will not be caused. In addition, by introducing a gas containing hydrogen from the gas introduction port 36, not only the effect of removing the oxide film on the melted solder surface can be improved, but also the amount of hydrogen used can be reduced and the cost can be reduced.

  Here, in the above embodiment, as the surface cleaning unit, the dielectric barrier system is shown in FIG. 2 and the torch type remote system is shown in FIG. 10, but the present invention is not limited to this. Alternatively, one electrode may be placed under the substrate to generate a direct type plasma for processing. This method has an advantage that simultaneous processing at a plurality of locations is possible because the processing area is large.

  An example of another solder surface cleaning unit is shown in FIG. This method irradiates a laser beam, and a laser beam 102 generated from a laser oscillator 101 passes through an optical fiber 103, an optical lens system 104, etc., and a lead frame or a molten solder 14 on a substrate 3 is formed. The surface is irradiated. Since the inside of the furnace has an atmosphere with a low oxygen concentration and there is also reducing hydrogen, it is possible to effectively remove the surface oxide film of the solder. Here, a YAG laser beam or an excimer laser beam pulse laser is suitable as the laser, but is not limited thereto. Moreover, it is also possible to arrange in a line shape instead of a nozzle shape.

  In addition, when the area of the solder to be processed is wide, the laser beam is irradiated in a donut shape so that the overall output is not a mountain shape (convex shape) with a high output at the center part, It is also possible to deal with a wide area. Such a donut-shaped laser beam shape is also effective when the laser output at the center is too high and damage due to temperature is a concern.

  As described above, the oxide film on the surface of the solder 12 supplied to the lead frame or the substrate 3 can be reduced and removed immediately before the semiconductor chip 15 is mounted and bonded by the laser beam, thereby improving the quality of the bonded portion. be able to.

  Here, it is conceivable that a residue is generated by surface cleaning using laser irradiation, and installing an exhaust port in the vicinity of the nozzle 104 prevents contamination of parts other than the joint, Effective for preventing contamination.

  In addition, since the higher the hydrogen concentration around the surface cleaning unit, the higher the efficiency of removing the oxide film, the mixed gas of hydrogen and an inert gas is close to the irradiation unit 104 of the surface cleaning unit that irradiates the laser beam. The amount of hydrogen gas used can be reduced and the cost can be reduced by providing the hydrogen concentration distribution.

  In FIG. 14, the third step (surface cleaning unit 13) of the main part of the die bonder shown in FIG. 1 is divided by the atmosphere in the cover (furnace) 2 in which the outside air is blocked by the other steps and the inner wall 51.52. An example is shown. In the present invention, a mixed gas of hydrogen and an inert gas is supplied from a position close to the surface cleaning unit 13, and the hydrogen concentration in the vicinity of the third step that requires the highest hydrogen gas concentration is peaked. As described above, the atmosphere in the cover 2 is configured such that the hydrogen concentration decreases toward the entrance 18 and the exit 19 of the conveyor.

  By installing the inner wall 51.52 shown in FIG. 14 and the lead frame which is placed on the guide rail 4 and moves between the processes, or the doors 53 and 54 which are opened and closed only when the substrate 3 passes, the hydrogen usage amount is reduced. Further, the hydrogen concentration can be kept high only in the vicinity of the surface cleaning unit 13 by reducing the number. In addition, since the lead frame or the substrate 3 is very thin, the opening / closing doors 53 and 54 may be provided with holes that can pass through instead of the doors to increase the ventilation resistance.

  From the above examples, by using a die bonder device having a surface cleaning unit, there is no long-term contamination in the furnace, low hydrogen consumption, low cost, and reduction of voids that cause defects in solder joints. Is possible.

DESCRIPTION OF SYMBOLS 1 ... Main part of die bonder of this invention, 2 ... Cover (furnace), 3 ... Lead frame or board, 4 ... Guide rail, 5 ... Lead frame or moving direction of board, 6a, 6b, 6c, 6c-1 , 6c-2, 6d ... opening window, 7 ... wire solder, 8 ... heater,
9 ... Solder supply nozzle, 10 ... Solder supplied, 11 ... Solder forming rod,
DESCRIPTION OF SYMBOLS 12 ... Solder which spreads, 13 ... Surface cleaning unit, 14 ... Solder which performed surface cleaning process, 15 ... Semiconductor chip, 16 ... Collet, 17 ... Solder connection part,
18 ... Entrance to the furnace, 19 ... Exit from the furnace, 21 ... Nozzle,
22 ... Electrode, 23 ... Dielectric, 24 ... Power source, 25 ... Gas inlet, 26 ... Plasma, 27 ... Exhaust port,
31 ... Nozzle, 32 ... Electrode, 33 ... Center electrode, 34 ... Insulator, 35 ... Power supply,
36 ... Gas inlet, 37 ... Discharge space, 38 ... Gas outlet, 39 ... Plasma,
40 ... Exhaust port, 41 ... Oxide film derived from wire solder, 42 ... Oxide film on wet spread solder, 43 ... Void, 44 ... Poor wetting, 45 ... Oxidized film destroyed and dispersed, 46 ... Irregular fillet shape 47 ... An oxide film remaining on the surface of the wire solder,
61 ... contour lines of hydrogen concentration distribution,
71 ... Plasma generator, 72, 73, 74 ... Processing nozzle,
DESCRIPTION OF SYMBOLS 101 ... Laser oscillator, 102 ... Laser beam, 103 ... Optical fiber, 104 ... Optical system lens,
120... Main part of a conventional die bonder device, 121.

Claims (16)

In a die bonder device for joining a plurality of members to be joined by forming a solder joint,
Solder supply means for supplying solder to the members to be joined;
A surface cleaning means for reducing and removing the surface oxide film of the solder supplied to the member to be joined by using gas;
Exhaust means for exhausting the gas used for the reduction of the solder;
Heating means for heating and melting the solder;
A die bonder apparatus comprising a joining means for joining another member to be joined to the molten solder from which the surface oxide has been removed and supplied to the member to be joined. The die bonder device according to claim 1,
The die bonder apparatus characterized in that the surface cleaning means removes the oxide film by performing plasma treatment under atmospheric pressure. The die bonder device according to claim 1,
The die bonder apparatus characterized in that the surface cleaning means removes the oxide film by laser irradiation. In the die bonder device according to any one of claims 1 to 3,
The gas is a mixed gas of hydrogen and an inert gas,
A die bonder apparatus characterized in that the atmosphere in the furnace is configured such that the hydrogen concentration is high in the vicinity of the surface cleaning means and the hydrogen concentration decreases as the distance from the surface cleaning means increases. The die bonder device according to claim 4,
A die bonder characterized in that the hydrogen concentration in the furnace is suppressed to 4% or less.   6. The die bonder device according to claim 1, wherein the exhaust means exhausts the gas by suction. The die bonder device according to claim 2,
The die bonder apparatus characterized in that the exhaust means exhausts through an exhaust port integrally provided on an outer periphery of a nozzle for generating plasma of the surface cleaning means. In the die bonder device according to any one of claims 1 to 7,
A die bonder apparatus, wherein a partition member is provided between the surface cleaning means and the joining means, and the exhaust means is provided closer to the surface cleaning means than the partition member. In the die bonder device according to any one of claims 1 to 8,
A die bonder device comprising a second cleaning means for cleaning a member to be joined before the solder is supplied. In the die bonder device according to any one of claims 1 to 9,
A die bonder apparatus comprising: a third cleaning means for supplying a surface of the solder before being joined to the other member to be joined and to be joined to the other member. In a die-bonding method for joining a plurality of members to be joined by forming a solder joint,
A surface cleaning step of reducing and removing the oxide film on the surface of the solder supplied to the member to be joined using gas,
Exhausting the gas used to reduce the solder;
Supplying the solder from which the oxide film has been removed to the member to be joined;
Heating and melting the solder; and
A step of joining another member to be joined to the molten solder from which the surface oxide has been removed and supplied to the member to be joined;
A die-bonding method comprising: The die-bonding method according to claim 11, wherein
In the surface cleaning step, a plasma treatment is performed on the solder at atmospheric pressure. The die-bonding method according to claim 11, wherein
In the surface cleaning step, the solder is irradiated with a laser. The die-bonding method according to any one of claims 11 to 13,
A die bonding method characterized in that the hydrogen concentration is high in the vicinity of the position where the surface cleaning step is performed, and the hydrogen concentration decreases with increasing distance from the position. The die bonding method according to any one of claims 11 to 14,
In the exhaust process, the gas is exhausted by suction, and the die-bonding method is characterized. The die-bonding method according to claim 14, wherein
The die bonding method, wherein the hydrogen concentration is 4% or less.

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