JP2004319734A - Process for manufacturing electronic apparatus circuit device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an electronic apparatus circuit device in which high productivity essential to reflow processing can be ensured by a simple process in correspondence with reduction in the size of components or complicacy in the shape of the components. <P>SOLUTION: In order to manufacture an electronic apparatus circuit device by mounting an electronic component 32 through soldering on a circuit board 31 produced by forming a circuit pattern on the surface 21 of a metal base 20 having uneven thickness between the front surface 21 and the rear surface 22, a first stage comprising a step for adding solders having different melting points to respective surface areas of the circuit board having a different thickness between the front surface 21 and the rear surface 22 while spacing apart from each other and a step for mounting the electronic component 32, a second stage for heating the metal base 20 having the circuit board 31 in the first state, and a third stage for cooling the metal base 20 heated in the second stage, are carried out. In place of solders having different melting points, adding amount of solder having the same melting point may be controlled. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a circuit device for an electronic device, and more particularly to a method for manufacturing the device using a soldering process in a reflow furnace on a circuit board having a non-uniform thickness immediately below a flat surface.
[0002]
[Prior art]
A soldering process that is frequently used when mounting an electronic component on a circuit board is important for a technology of manufacturing an electronic device circuit device, and is used when a circuit portion is mounted on one surface side of a radiation fin. (For example, Patent Document 1)
[0003]
Ideally, a large amount of various electronic components can be mounted on a circuit board, and therefore, there is a strong tendency that various components having different heat capacities are subjected to the soldering process. Reflow processing methods disclosed in Patent Documents 2 and 3 are disclosed as taking into account such various kinds of electronic components.
[0004]
The reflow processing method performs the soldering processing with high productivity. For example, it is common to use a reflow furnace 3 provided with a carry-in port 1 and a carry-out port 2 as shown in FIG. . The inside of the reflow furnace 3 is provided with a transfer path 4 such as a belt conveyor that enables transfer from the carry-in port 1 to the carry-out port 2, and upper and lower heaters 5 and 6 that face each other across the transfer path 4. ing. When mounting the electronic component 8 on the circuit board using the reflow furnace 3, a conductive material such as copper foil is pasted on the insulating material 7 a on the base 7 outside the reflow furnace 3 in advance. Then, an etching process or the like is performed to form a circuit board 8, and cream solder is added to the mounting portion of the electronic component 9 on the circuit board 8. Then, the circuit board 8 on which the electronic components 9 are placed is transported from the carry-in port 1 to the carry-out port 2 by the transport path 4, and is heated by the upper and lower heaters 5 and 6 during the transport. The cream solder added onto the substrate 8 by the heating of the heaters 5 and 6 reaches the melting point and melts. After that, when the circuit board 8 is carried out from the carry-out port 2, the solder is solidified as the substrate 8 is cooled, and finally the solder is solidified. Then, the electronic component 9 is fixed to the circuit board 8, and the mounting operation is completed.
[0005]
Such a reflow soldering process is much used in a process of mounting electronic components on a circuit board because productivity is remarkably higher than in a direct mounting operation using a conventional soldering iron and mass production is possible.
[0006]
In order to prevent the variation in the progress of the soldering process between the electronic components having different temperature raising characteristics and the deterioration of the component quality due to the variation, the one disclosed in Patent Document 2 is designed according to the electronic components having different heat capacities. Heating means (near-infrared heater and far-infrared heater) are selected, and in the case of Patent Document 3, the transfer speed of the object to be soldered is different for each heating step such as preheating and main heating.
[0007]
[Patent Document 1]
Japanese Utility Model Laid-Open No. 5-87956 (pages 5-9, FIGS. 1 and 2)
[0008]
[Patent Document 2]
JP-A-8-64954 (pages 4 to 13, FIGS. 1, 6 and 7)
[0009]
[Patent Document 3]
JP-A-2000-183511 (pages 3 to 6, FIG. 1)
[0010]
[Problems to be solved by the invention]
As described above, the method disclosed in Patent Document 1 involves a soldering process or a bonding process using a heat-resistant adhesive for each mounting process of various types of electronic components, so that the process is complicated and there is a problem in productivity.
[0011]
Also, the soldering methods disclosed in Patent Literatures 2 and 3 by reflow processing that should compensate for this disadvantage have complicated processes, and this causes a prolonged tact time, and there is a limit to improvement in productivity.
[0012]
Furthermore, in recent years, electronic device circuit devices have been significantly reduced in size and weight. For example, in a motor device, a device such as an integrated motor unit and control board unit has been devised.
[0013]
Along with this, there are many restrictions on circuit device design. For example, the radiating fins disclosed in Patent Document 1 have a large occupied space, so that mounting them as they are is not welcomed. In addition, the shape of the substrate is inevitably complicated, and therefore, even if the soldering processes of Patent Documents 2 and 3 are performed, a bias in the heat capacity occurs in the substrate having a much larger heat capacity than the electronic component to be mounted. In this case, the effect of the response performed for each electronic component is diminished. That is, due to the difference in heat capacity of the substrate portion immediately below the surface area on which the electronic component is mounted, a delay in reaching the melting point temperature occurs due to insufficient heating at the solder-added portion, and solder processing is not reliably performed. On the contrary, there is a possibility that overheating is locally caused for a predetermined time or more, resulting in deterioration of electronic components.
[0014]
SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an electronic device circuit device capable of securing the original high productivity of reflow processing in a simple process in response to downsizing of components in the device and complicating component shapes accompanying the process. It is an object of the present invention to provide a manufacturing method.
[0015]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides an electronic device in which an electronic component is mounted on a circuit board formed by forming a circuit pattern on a surface of a metal base having an uneven thickness between the front and back surfaces by soldering. In order to manufacture a device circuit device, a step of separately adding a solder having a different temperature characteristic to each circuit board surface region having a different temperature rising characteristic and a step of mounting an electronic component are performed as a first step. And
[0016]
According to this, in the first stage, by adding a solder corresponding to the temperature-raising characteristic to each substrate surface region, when the second stage of heating the metal base in the first stage is performed, Even if there is a difference in the rate of temperature rise, it is possible to eliminate the difference in the progress of the soldering process caused by the difference.
[0017]
For example, paying attention to the melting point of the solder as the temperature characteristic, in the first stage, the solder having a different melting point is added to each surface region having a different heating rate while being separated. That is, by using a solder having a high melting point in a surface region having a large temperature rising rate and using a solder having a low melting point in a region having a small temperature rising rate, the solder added portions reach their melting points almost at the same time, and as a result, The timing of soldering on the substrate is aligned.
[0018]
Further, for example, attention is paid to the heat capacity as a temperature characteristic of the solder, and in the first stage, solders having the same melting point and different heat capacities are separately added to the surface regions having different heating rates. That is, by using a solder having a large heat capacity in the surface region where the heating rate is large and using a solder having a small heat capacity in the area where the heating rate is small, the solder-added portions reach their melting points almost at the same time, respectively. As a result, the timing of soldering on the substrate is aligned.
[0019]
Further, a third step of cooling the metal base heated in the second step by leaving it in the air or carrying it into a low-temperature constant-temperature bath is performed. Thus, the soldering can be completed in a state where the timings are aligned as described above.
[0020]
In other words, by going through the above first to third steps, the soldering timing can be made uniform at each of the solder-added portions on the substrate. The device can be manufactured.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 2A is a schematic view illustrating the back surface of the metal base 20 used in the present invention. As shown in the side view of FIG. 2B, of the front and back surfaces of the metal base 20, the front surface 21 has a flat surface shape for forming a substrate circuit, and the back surface 22 has an uneven shape assuming a direct connection to a motor. The metal base 20 itself is also used as a part of the motor housing. That is, as shown in the front view of FIG. 2A and the perspective view of FIG. 2C, a motor bearing 23, a cable hole 24, a mounting bracket 25, and the like are provided on the back surface 22 of the metal base 20. Are provided to form a complicated shape with many undulations. Further, the substrate circuit on the flat surface 21 of the metal base 20 is subjected to an etching process or the like on a conductive material such as a copper material coated on the surface 21 via a thermoplastic insulating sheet. Obtained by forming a pattern.
[0022]
FIG. 3 shows a process diagram of the present invention using the above-described metal base 20. In the first stage of this process, a cream solder (see FIG. 7) is applied to a portion to be joined of a substrate circuit 31 formed on a flat surface 21 of a metal base 20 having a complicated shape on a back surface 22 via an insulating sheet 30 via a known printing method. (Not shown), and an electronic component 32 such as an IC lead, a lead terminal, or a chip component is placed on the portion to be joined. At this time, a solder L of a low melting point material is added by printing to a portion having a relatively large thickness directly below the surface 21 of the metal base 20, and a solder H of a high melting point material is added to a portion having a relatively small thickness. Print.
[0023]
If the solders H and L are in contact with each other at the time of adding the solders H and L by printing, the solders are mixed at the time of subsequent melting of the solder, and the desired solder temperature characteristics may be obtained at each of the added portions. It becomes difficult. For this reason, when the solder is added to the surface 21, it is necessary to separate and separate the respective added portions by the solders H and L.
[0024]
Also, the melting point of the solder can be raised and lowered by adjusting the amount of metal in the solder. That is, for example, in the case of a ternary solder in which three metals of tin, bismuth, and lead are mixed, the melting point can be changed by increasing or decreasing the amount of the lead metal. Thus, the above-mentioned high melting point solder H and low melting point solder L can be easily obtained.
[0025]
Then, in this state, the metal base 20 is conveyed by a known conveying means through the entrance 33a onto the hot plate 34 heated and heated inside the reflow furnace 33 so that the cream solder on the substrate circuit 31 can be melted. Then, the inside of the reflow furnace 33 is heated (for example, 180 to 230 ° C.), and this is set as a second stage.
[0026]
At this time, the portion having a large thickness immediately below the surface 21 has a large heat capacity, so that the rate of temperature rise is slower than that of the portion having a small thickness. Since the high-melting-point solder H is added to each part, the timing at which each solder melts can be made uniform.
[0027]
Also, instead of adding a solder having a different melting point according to the thickness just below the surface 21 as described above, a solder having the same melting point may be used, and the amount of the solder added may be varied according to the thickness. good. In other words, if a small amount of solder is added to a large-thick portion and a large amount of solder is added to a small-thick portion, the small-addition amount solder portion has a small heat capacity, and the large-addition amount solder portion has a large heat capacity. The timing at which the solder melts can be made uniform.
[0028]
In any of the above cases, the influence of the electronic component 32 is not taken into account when considering the heat capacity that affects the melting of the solder. This is because there is a remarkable volume difference between the metal base 20 and the electronic component 32, and the effect of the electronic component 32 on the total heat capacity is limited. Therefore, the magnitude of the heat capacity substantially depends on the thickness of the metal base 20.
[0029]
By the way, the reason why the hot plate 34 is used as a heating means in the second stage is to supply heat to each solder added on the surface 21 of the metal base 20 in the thickness direction of the metal bases 20 having different heat capacities. It is. Further, this is also to prevent the electronic component 32 placed on the front surface 21 from being subjected to direct heat irradiation as shown in a conventional example (for example, FIG. 1 and Patent Document 2), thereby causing deterioration thereof. That is, a coil heater or an infrared radiation heater may be used as long as it is a heating means for heating the rear surface of the metal base 20 from below. When using a heater from above or a reflow furnace for heating the entire atmosphere in the furnace, a cover (not shown) covering the electronic component 32 is placed on the circuit board 31 to reduce the inferiority of the electronic component 32. Can be prevented.
[0030]
Then, after each of the solders is melted, the metal base 20 is carried out of the reflow furnace 33 from the outlet 33b. Then, as a third step, the electronic components 32 are fixed on the circuit board 31 by solidifying the solder by cooling.
[0031]
As such a cooling means, in addition to natural cooling, known means such as loading into a low-temperature constant temperature bath can be used, but as described above, there is a bias in heat capacity corresponding to the thickness of the metal base 20, In particular, it takes a relatively long time to cool the large thickness portion. This not only hinders the improvement of the productivity, but also causes the electronic component 32 fixed to the large-thickness portion to be prolonged in a high-temperature state, which may cause the component to be deteriorated.
[0032]
For this reason, in the present embodiment, the mold member 40 shown in FIG. 4 is immediately attached after the metal base 20 is carried out from the carry-out port 33b of the reflow furnace 33. As shown in FIG. 4, the mold member 40 is provided with a bearing groove so that it can be fitted to the motor bearing 23, the cable hole 24, and the protrusion or recess of the mounting bracket 25, respectively. 43, a cable hole groove 44, a bracket groove 45, and the like. The material of the mold member 40 is a thermal conductor having the same thermal conductivity as the metal base 20.
[0033]
Then, the mold member 40 is fitted to the metal base 20 in a state where the temperature is lower than that of the metal base 20, and the cooling is performed in this manner, whereby the third stage is completed, and all the processes of the present embodiment are completed. I do.
[0034]
In the present embodiment, a metal or an alloy is assumed as a material of the metal base 20 and the mold member 40. However, the metal base 20 and the mold member 40 have necessary heat resistance and heat conductivity, such as a carbon composite material and ceramics. If so, the material is not limited to the metal material, and a resin material may be used. Furthermore, if a low conductive material is used for the base 20, the above-mentioned thermoplastic insulating sheet 30 becomes unnecessary, and an effect of simplifying the constituent material of the circuit board 31 can be obtained.
[0035]
Further, in the present embodiment, a cream solder printing machine is used with the surface 21 of the metal base 20 forming the circuit board 31 as a flat surface, but if the surface 21 is a non-flat surface, it is scrambled. There is a possibility that the addition accuracy may be reduced by the action, and it becomes difficult to use a solder printing machine. In this case, by cutting the sheet-shaped solder into a required shape and adding it to the surface 21, it can be used as an alternative to the solder printing method.
[0036]
Further, in the present embodiment, the back surface 22 of the metal base 20 is a part of the motor housing. However, this is only an example of the back surface 22 having a complicated shape, and the present invention is not limited to this. Absent. As an example of providing a complicated shape of the back surface 22, a heat sink or a metal case for another use can be cited. Also, the surface 21 of the metal base 20 has a flat surface shape for forming a substrate circuit, but the present invention is not limited to this. That is, even if the surface 21 has a complicated shape, by adjusting the melting points and the added amounts of the solders H and L according to the thickness just below the solder-added portion on the surface 21, the temperature characteristics are changed. , A similar reflow process can be performed.
[0037]
【The invention's effect】
As is apparent from the above description, according to the method for manufacturing an electronic device circuit device of the present invention, even when the substrate shape becomes complicated, the heat capacity causing the temperature rise characteristic difference at a portion where the substrate thickness is different or the like. Even if the deviation occurs, by adding the solder having different temperature characteristics such as the melting point and the heat capacity corresponding to the deviation, the timing of the soldering can be made uniform at the soldered portion on the substrate. This makes it possible to perform a high-efficiency reflow process while preventing a long tact time.
[0038]
Furthermore, the efficiency of the soldering process can be further improved by fitting the low-temperature mold member to the substrate base during cooling after the reflow process.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a conventional reflow processing step. FIG. 2 (a) is a front view of a back surface of a metal base used in the present invention, (b) a side view of a metal base used in the present invention, and (c) is used in the present invention. FIG. 3 is a perspective view of a metal base. FIG. 3 is a reflow treatment process diagram used in the present invention. FIG. 4 is a perspective view of a mold member used in the present invention.
3 33 Reflow furnace 5 6 Heater 8 31 Circuit board 9 32 Electronic component 20 Metal base 21 Front surface 22 Back surface 34 Hot plate 40 Mold member H High melting point solder L Low melting point solder

Claims (3)

For a circuit board formed by forming a circuit pattern on the surface of a metal base with an uneven thickness between the front and back sides,
A step of separately adding solder having different temperature characteristics for each of the circuit board surface regions having different temperature raising characteristics,
Mounting the electronic component,
A first stage consisting of
A second stage of heating the metal base having the first stage circuit board;
Cooling the metal base heated in the second step.
A method for manufacturing an electronic device circuit device, comprising: 2. The electronic device according to claim 1, wherein a melting point is used as a temperature characteristic of the solder, and the solder having a different melting point is separately added to each of the surface regions having the different heating rates in the first step. 3. A method for manufacturing a circuit device. The heat capacity is used as a temperature characteristic of the solder, and the solder having the same melting point and a different heat capacity is separately added to each of the surface regions having the different heating rates in the first step. Method for manufacturing electronic device circuit device.

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