JP4226944B2 - Manufacturing method of electronic device circuit device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing an electronic device circuit device, and more particularly to a method of manufacturing the above device using a soldering process in a reflow furnace on a circuit board in which the thickness just below a flat surface is unevenly formed.
[0002]
[Prior art]
The soldering process frequently used when mounting electronic components on a circuit board is important for the manufacturing technology of electronic device circuit devices, and is used when mounting a circuit portion on one side of a radiation fin. (For example, Patent Document 1)
[0003]
Also, it is ideal that various electronic components can be mounted in large quantities on the circuit board. For this reason, there is a strong tendency that various components having different heat capacities are subjected to soldering processing. And the reflow processing method shown in patent documents 2 and 3 is indicated as what considers correspondence to such many kinds of electronic parts.
[0004]
The reflow processing method performs 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. . Inside the reflow furnace 3, a conveyance path 4 such as a belt conveyor that enables conveyance from the carry-in entrance 1 to the carry-out exit 2, and upper and lower heaters 5 and 6 that face each other across the carry path 4 are provided. ing. When the electronic component 8 is mounted on the circuit board using the reflow furnace 3, a conductive material such as a copper foil is pasted on the insulator material 7 a on the base 7 in advance outside the reflow furnace 3. On the other hand, the circuit board 8 is formed by performing an etching process or the like, 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 component 9 is placed is transported from the transport entrance 1 toward the transport exit 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 to the substrate 8 by heating of the heaters 5 and 6 reaches the melting point and melts. Thereafter, 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 remarkably high in productivity and can be mass-produced as compared with a direct mounting operation using a conventional soldering iron, and is therefore frequently used in the mounting process of electronic components on a circuit board.
[0006]
And in order to prevent the deterioration of the quality of the parts accompanying the variation in the progress of the soldering process between the electronic components having different temperature rising characteristics, the one shown in Patent Document 2 is based on the electronic components having different heat capacities, A heating means (near infrared heater and far infrared heater) is selected, and the one in Patent Document 3 differs in the conveying speed of the soldering object for each heating process such as preheating or main heating.
[0007]
[Patent Document 1]
Japanese Utility Model Publication No. 5-87956 (pages 5 to 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 2000-183511 (pages 3 to 6, FIG. 1)
[0010]
[Problems to be solved by the invention]
As described above, the one disclosed in Patent Document 1 has a difficulty in productivity because the process is complicated because the soldering process and the heat-resistant adhesive are performed for each mounting process of various types of electronic components.
[0011]
Also, the soldering methods of Patent Documents 2 and 3 by reflow processing that should compensate for this drawback are complicated in process, and this becomes a factor in prolonging tact time, and there is a limit to improvement in productivity.
[0012]
Furthermore, recent electronic device circuit devices have been remarkably reduced in size and weight. For example, in a motor device, a contrivance has been made such as integrally configuring a motor unit and a control board unit.
[0013]
Accordingly, restrictions on circuit device design increase, and for example, the heat dissipating fins of Patent Document 1 have a large occupied space and are not welcomed to be mounted as they are. In addition, the complexity of the shape of the board portion is unavoidable, and therefore, even if the soldering process of Patent Documents 2 and 3 is performed, a deviation in heat capacity occurs in the board portion having a heat capacity much larger than the electronic component to be mounted. The effect of the correspondence that should have been performed for each electronic component is diminished. In other words, the heat capacity of the board part directly under the surface area where electronic components are mounted differs, resulting in a delay in reaching the melting point temperature due to insufficient temperature rise in the solder-added part, and solder processing is not performed reliably. On the contrary, there is a possibility that the electronic component may be deteriorated due to local overheating locally.
[0014]
In view of the above-described problems, the present invention provides an electronic device circuit device that can ensure high productivity inherent in reflow processing in a simple process in response to downsizing of components in the apparatus and complicated shape of the components. It is an object to provide a manufacturing method.
[0015]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention mounts electronic components on a circuit board formed by forming a circuit pattern on the surface of a metal base with uneven thickness between the front and back surfaces by soldering. to prepare the device circuit device, comprising the steps of temperature characteristics are added to be separated respectively different solder for each surface region of the circuit board different of Atsushi Nobori property based on a wall thickness of unequal, the electronic component The placing process is performed as the first stage.
[0016]
According to this, in the first stage, by adding a solder corresponding to the temperature rise characteristic for each substrate surface region, the second stage in which heating is performed on the metal base in the first stage is performed. Even if a temperature increase rate difference occurs, it is possible to eliminate the difference in the progress of the soldering process caused by this.
[0017]
For example, paying attention to the melting point as a temperature characteristic of the solder, in the first stage, solders having different melting points are added separately for each surface region having a different heating rate. That is, by using a solder having a high melting point in the surface region where the temperature rising rate is high, and using a solder having a low melting point in the region where the temperature rising rate is low, the solder added portions reach the melting points almost simultaneously, and as a result, The timing of soldering on the board will be aligned.
[0018]
Also, for example, paying attention to the heat capacity as the temperature characteristics of the solder, in the first stage, solders having the same melting point and different heat capacities are added separately for each surface region having a different heating rate. That is, by using a solder having a large heat capacity in a surface region where the temperature rising rate is high and using a solder having a small heat capacity in a region where the temperature rising rate is low, the solder added portion reaches the melting point almost at the same time. As a result, the soldering timing on the board is aligned.
[0019]
Further, the metal base heated from the back surface in the second stage is subjected to a third stage in which the metal base is cooled by being left in the atmosphere or carried into a low-temperature thermostatic bath. As a result, the soldering can be completed in a state where the timing is aligned as described above. Note that a mold member having a temperature lower than that of the metal base may be fitted to the back surface of the metal base, thereby cooling the metal base.
[0020]
That is, by passing through the first to third steps, the timing of soldering can be made uniform in each solder-added portion on the substrate, so that the tact time can be prevented from being prolonged and the electronic device circuit can be efficiently performed. The device can be manufactured.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2A is a schematic view showing 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 the formation of the substrate circuit, and the back surface 22 has an uneven shape assuming direct connection with the 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, the rear surface 22 of the metal base 20 has a motor bearing 23, a cable hole 24, a mounting bracket 25, and the like. Is provided and has a complex shape with many undulations. Further, the substrate circuit on the flat surface 21 of the metal base 20 described above performs 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]
A process diagram of the present invention using the metal base 20 is shown in FIG. In the first stage of this process, cream solder (see FIG. 5) is applied to a portion to be bonded of the substrate circuit 31 formed on the flat surface 21 of the metal base 20 having a complicated shape on the back surface 22 via the insulating sheet 30 by a known printing method. In addition, 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, the solder L of the low melting point material is added to the portion where the thickness just below the surface 21 of the metal base 20 is relatively large by printing, and the solder H of the high melting point material is added to the portion where the thickness is relatively small. Print.
[0023]
In addition, when the solder H and L are in contact with each other at the time of addition by printing of the solder H and L, the solder is mixed when the solder is melted thereafter, and desired solder temperature characteristics can be obtained at each added portion. It becomes difficult. For this reason, when the solder is added onto the surface 21, it is necessary to charge and separate the added portions of the solders H and L from each other.
[0024]
Further, the melting point of the solder can be raised and lowered by adjusting the amount of the metal in the solder. That is, for example, in the case of a ternary solder containing three metals of tin, bismuth, and lead, the melting point can be changed by increasing or decreasing the amount of lead metal. In this way, the high melting point solder H and the low melting point solder L described above can be easily obtained.
[0025]
Then, in this state, the metal base 20 is transferred to the hot plate 34 that is energized and heated inside the reflow furnace 33 via the transfer port 33a by a known transfer means so that the cream solder on the substrate circuit 31 can be melted. The inside of the reflow furnace 33 is heated (for example, 180 to 230 ° C.), and this is set as the second stage.
[0026]
At this time, the portion with a large thickness just below the surface 21 has a large heat capacity, so the rate of temperature rise is slower than the portion with a small thickness. However, as described above, the low melting point solder L is applied to the thick portion with a small thickness. Since the high melting point solder H is added to each portion, the timing at which each solder melts can be made uniform.
[0027]
In addition, instead of adding 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 is used, and the amount of addition of this solder is varied depending on the thickness. good. That is, if a small amount of solder is added to the large thickness portion and a large amount of solder is added to the small thickness portion, the small addition amount of the solder portion has a small heat capacity, and the large addition amount of the solder portion has a large heat capacity. The timing at which the solder melts can be aligned.
[0028]
In any of the above cases, the influence of the electronic component 32 is not taken into consideration when considering the heat capacity that affects the melting of the solder. This is because there is a marked volume difference between the metal base 20 and the electronic component 32, and the influence of the electronic component 32 on the overall heat capacity remains limited. For this reason, 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 base 20 having different heat capacities. It is. Furthermore, it is also for avoiding that the electronic component 32 mounted on the surface 21 is directly irradiated with heat as shown in the conventional example (for example, FIG. 1 and Patent Document 2) and is not deteriorated. That is, a coil heater or an infrared radiation heater may be used as long as it is a heating means from the lower side with respect to the back surface of the metal base 20. When using a heater from above or a reflow furnace that heats the entire atmosphere in the furnace, a cover (not shown) that covers the electronic component 32 is placed on the circuit board 31 to reduce the deterioration of the electronic component 32. It becomes possible to prevent.
[0030]
And after melting each solder, the metal base 20 is carried out of the reflow furnace 33 from the carry-out port 33b. Then, as a third stage, the solder is solidified by cooling, and each electronic component 32 is fixed on the circuit board 31.
[0031]
As such a cooling means, publicly-known means such as natural cooling or carrying into a low-temperature thermostat 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 improvement in productivity, but also leads to a prolonged high-temperature state of the electronic component 32 fixed to the large-thickness portion, which may cause component deterioration.
[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 unloaded from the unloading port 33b of the reflow furnace 33. As shown in FIG. 4, the mold member 40 has a groove for the bearing portion so that it can be fitted in correspondence with the convex portion and the concave portion of the motor bearing portion 23, the cable hole portion 24, and the mounting bracket 25 of FIG. 43, a cable hole groove 44, a bracket groove 45, and the like are formed. The material of the mold member 40 is a heat conductor having a thermal conductivity equivalent to that of 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 third stage is completed by performing cooling in this way, and all the steps of the present embodiment are completed. To do.
[0034]
In the present embodiment, a metal or an alloy is assumed as the 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 thermal conductivity, such as a carbon composite material and ceramics. If there is, it is not limited to a metal material, and a resin material may be used. Further, when a low conductive material is used for the base 20, the thermoplastic insulating sheet 30 is not necessary, and an effect of simplifying the constituent material of the circuit board 31 can be obtained.
[0035]
In the present embodiment, the cream solder printer is used with the surface 21 of the metal base 20 forming the circuit board 31 as a flat surface. However, when the surface 21 is a non-flat surface, squeeze is performed. Due to the action, the accuracy of addition may be reduced, and the use of a solder printer becomes difficult. In this case, it is possible to replace the solder printing method by cutting the sheet-like solder into a required shape and adding it onto the surface 21.
[0036]
Furthermore, in the present embodiment, the back surface 22 of the metal base 20 is a part of the motor housing. However, this is only shown as 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 giving the complicated shape of the back surface 22, a heat sink or a metal case for another use can be cited. Further, 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, the temperature characteristics are changed by adjusting the melting points and addition amounts of the solders H and L according to the thickness immediately below the solder addition portion on the surface 21. A similar reflow process can be performed.
[0037]
【The invention's effect】
As is clear from the above description, according to the method for manufacturing an electronic device circuit device of the present invention, even if the substrate shape is complicated, the heat capacity that causes the temperature rise characteristic difference in the portion where the substrate thickness is different, etc. Even if the bias occurs, the soldering timing can be made uniform at the solder-added portion on the substrate by adding solder having different temperature characteristics such as melting point and heat capacity. This makes it possible to perform highly efficient reflow processing that prevents the tact time from being prolonged.
[0038]
Furthermore, the efficiency of the soldering process can be further improved by fitting a low-temperature mold member to the board base portion during cooling after the reflow process.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a conventional reflow treatment process. FIG. 2A is a front view of a rear surface of a metal base used in the present invention. FIG. 1B is a side view of a metal base used in the present invention. FIG. 3 is a perspective view of a metal base 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 (4)

For circuit boards formed by forming circuit patterns on the surface of a metal base with uneven thickness between the front and back sides,
A step of temperature characteristics are added to be separated respectively different solder for each surface areas of different said circuit board having heating properties based on a wall thickness of unequal,
Placing the electronic component;
A first stage comprising:
A second stage in which the metal base having the circuit board in the first stage is heated only from the back surface ;
A third stage for cooling the metal base heated in the second stage,
A method of manufacturing an electronic device circuit device.   2. The electronic device according to claim 1, wherein a melting point is used as the temperature characteristic of the solder, and a solder having a different melting point is added separately for each surface region having a different temperature increase rate in the first stage. A method of manufacturing a circuit device.   2. The solder according to claim 1, wherein a heat capacity is used as a temperature characteristic of the solder, and solder of the same melting point having a different heat capacity is added separately for each surface region having a different heating rate in the first stage. Manufacturing method of electronic device circuit apparatus. In the third stage, cooling is performed by fitting a mold member having a shape corresponding to the shape of the back surface of the metal base having unevenness to the back surface of the metal base at a temperature lower than that of the metal base. The method of manufacturing an electronic device circuit device according to claim 1, wherein:

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