JP4713444B2 - Reflow device - Google Patents

Description

  The present invention relates to a reflow apparatus for performing reflow soldering on a board on which a component is mounted.

  In recent years, lead-free solder (lead-free solder) has been developed and used. As such a lead-free solder, three types of alloys of Sn-Ag-Cu (tin / silver / copper), Sn-Cu (tin / copper), and Sn-Zn (tin / zinc) are often used. Has been. In particular, the Sn—Ag—Cu system is currently mainstream because of its high bonding strength and excellent reliability.

  However, the melting point of lead-free solder is about 220 ° C., which is considerably higher than the melting point (183 ° C.) of a conventional Sn—Pb eutectic solder made of an alloy of tin and lead. If the heat-resistant temperature (soldering temperature) is 240 ° C., the temperature range allowed during soldering is very narrow. Therefore, in order to ensure the reliability of the component mounted on the board, it is necessary to prevent the temperature of the solder from being excessively increased during soldering and to reduce the thermal damage of the mounted component. Furthermore, if the temperature at the time of soldering increases too much, the substrate itself may be deformed, eventually causing a solder joint failure. Care must be taken in managing the temperature.

  In general, when soldering a substrate of an electronic device and a surface-mount type mounting component, a reflow method using a reflow device that performs heating with infrared rays or hot air is widely used. In such a reflow method, a lead-free solder is preliminarily printed in a paste form at a location where a component is mounted on a substrate, and the component is placed thereon by an automatic mounting machine (chip mounter), and then a reflow device. The whole board is heated by a (heating furnace), and soldering is performed by melting the solder.

  By the way, in the above reflow method, for example, when mounting components and board materials having different heat capacities are collectively reflowed, the temperature distribution on the board is made uniform, and the variation in the peak temperature of each mounting part and soldering portion is as much as possible. It needs to be small.

  Therefore, in Patent Document 1, the reflow apparatus is provided with a preheating unit, a reflow unit, and a cooling unit, and when the substrate is transferred to these, the transfer speed in the preheating unit, the transfer speed in the reflow unit, and the cooling unit It is described that, even if lead-free solder having a high melting temperature is used, the substrate on which components having different dimensions and heat capacities and components having inferior heat resistance are placed is reflowed.

JP 2000-183511 A

  However, in the method described in Patent Document 1, when reflowing a metal substrate such as an aluminum substrate, it is difficult to make the temperature distribution on the substrate uniform due to the influence of the heat capacity of the metal part (aluminum). In addition, rapid cooling after reflow is difficult. Accordingly, as a result, there is a possibility that a thermal load (damage) is given to the substrate or the mounted component due to the heat from the metal part.

  The present invention has been made in consideration of the above-described problems, and can reduce variations in temperature distribution on a substrate even when reflow soldering is performed on a solder having a relatively high melting temperature such as lead-free solder. Furthermore, it aims at providing the reflow apparatus which can reduce the thermal load to a board | substrate or a mounting component.

  The reflow apparatus according to the present invention includes a transport means for transporting a substrate on which electrical components are arranged, a heating unit for performing reflow soldering of the electrical components after preheating the substrate, and the reflow soldering A reflow apparatus having a cooling unit that cools the applied substrate, wherein the transport unit includes a workpiece mounting unit in which a mounting surface on which the substrate is mounted is made of a resin material, The heating unit includes a heating plate portion that heats a lower portion of the workpiece placement portion, and the cooling portion includes a cooling plate portion that cools a lower portion of the workpiece placement portion. And

  According to such a configuration, heat from the heating plate portion is conducted from the lower part of the substrate to be reflow soldered to the substrate through the mounting surface made of the resin material. Similarly, heat from the substrate is conducted to the cooling plate portion through the mounting surface. In this case, since the substrate is in contact with the resin material, the adhesiveness with the mounting surface is high, and the thermal conductivity is improved. For this reason, for example, even when a metal substrate having a large heat capacity is used as the substrate, the temperature of the substrate can be made to quickly follow the temperature profile of the reflow device, and the components mounted on the substrate can be thermally It is possible to prevent damage caused by a heavy load and to shorten the cycle time.

  In this case, the resin material is preferably used when the continuous use temperature is 250 ° C. or higher, for example, even when lead-free solder having a high melting point can be used for reflow soldering. In addition, it is more preferable that the resin material is a fluororesin because it has high heat resistance and less wear.

  In addition, a work jig for supporting the substrate placed on the work placement unit, the work jig, the jig plate portion disposed between the placement surface and the substrate, Provided with a substrate support portion provided on a surface of the jig plate portion on the substrate side and supporting the substrate at a predetermined height position from the jig plate portion with three support surfaces; By point support, heat conduction from the heating plate portion to the substrate can be set appropriately. For this reason, while being able to suppress overheating of a board | substrate, the variation in overheating can be reduced and it becomes possible to perform the stable reflow soldering.

  In this case, by forming the jig plate portion and the substrate support portion with a metal containing titanium, it becomes possible to effectively prevent warpage and twisting of the jig plate portion and the substrate support portion, and the production lot. The heat conduction to each substrate can be made more uniform, and the durability of the jig plate portion and the like can be improved.

  Furthermore, the area of the support surface per piece is 0.28 to 0.83% with respect to the area of the substrate with which the support surface abuts, and the height of the substrate support portion is the jig plate. When the distance between the portion and the substrate is set to 0.08 to 0.12 mm, the heat conduction from the heating plate portion to the substrate via the substrate support portion can be made more uniform. For this reason, since the temperature difference on the substrate can be further reduced, the temperature profile can be easily set.

  According to the present invention, heat from the heating plate portion provided in the reflow apparatus is conducted from the lower part of the substrate to be reflow soldered to the substrate through the mounting surface made of the resin material. Similarly, heat from the substrate is conducted to the cooling plate portion through the mounting surface. Therefore, for example, even when a metal substrate having a large heat capacity is used as the substrate, the temperature of the substrate can be made to quickly follow the temperature profile of the reflow device, and the components mounted on the substrate While preventing damage due to the load, the cycle time can be shortened.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a reflow apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic side view showing a configuration of a reflow apparatus 10 according to an embodiment of the present invention. FIG. 2 is a schematic plan view showing the conveying means 22 of the reflow apparatus 10 shown in FIG.

  The reflow apparatus 10 includes a board (component mounting board) on which a carry-in section 12, a heating section (reflow section) 14, a cooling section 16 and a carry-out section 18 are arranged in order, components are arranged, and solder (lead-free solder) is printed. ) This is a device that performs reflow soldering of the component in the heating unit 14 while conveying 20 and cools it in the cooling unit 16. In the reflow apparatus 10 according to the present embodiment, the substrate 20 is transported through the respective parts in a state of being supported by the work jig 19 (hereinafter also referred to as a work W).

  In such a reflow apparatus 10, a belt conveyor 21 constituting a conveying means 22 is passed from a carry-in unit 12 through a heating unit 14 to a cooling unit 16, and a workpiece W (work jig) is interposed therebetween. The substrate 20) supported at 19 can be transported continuously. Further, on the downstream side of the cooling unit 16, the rotating roller unit 24 constituting the carry-out unit 18 is disposed so that the upper surface position thereof is substantially flush with the belt conveyor 21.

  Further, the reflow apparatus 10 includes a control unit (control panel) 26 that controls driving of the carry-in unit 12, the heating unit 14, the cooling unit 16, the carry-out unit 18, the conveyance unit 22, and the like. The control unit 26 is provided with an operation unit 28 configured, for example, as a touch panel so that the operator can operate the reflow device 10 and set various conditions.

  The conveying means 22 includes a belt conveyor 21 that faces an opening 30 a formed in the upper portion of the apparatus main body 30, and roller driving units 32 a and 32 b that circulate and drive the belt conveyor 21. On one side of the roller driving units 32a and 32b, for example, a driving source (not shown) configured by an AC servo motor is provided. Thereby, the belt conveyor 21 can be driven with high accuracy at a predetermined speed (for example, 1 mm / s to 10 mm / s) for a predetermined time.

  The belt conveyor 21 is spanned between the carry-in section 12 and the cooling section 16 as described above, and the parts other than those located in the heating section 14 are exposed to the outside, and the work W to be carried in, carried out, etc. Is easy. The belt conveyor 21 is made of a material having sufficient heat resistance for passing through the heating unit 14, for example, stainless steel. The stainless steel is also effective from the viewpoint of rust prevention and the like.

  Further, in such a belt conveyor 21, a placement surface 34 a on which a resin sheet 36 is laid is provided on a workpiece placement portion 34 that is an upper surface portion on which the workpiece W is placed. In the case of the present embodiment, the bottom surface of the work jig 19 is made of metal (for example, titanium), and the metal work jig 19 and the belt conveyor 21 made of metal (for example, stainless steel) are brought into contact with each other. In some cases, even if the surface contact is apparent, it may be a point contact microscopically. Therefore, by providing the resin sheet 36 made of a resin material, the adhesion between the bottom surface of the work jig 19 and the work placing part 34 is improved, and thereby, the work placing part 34 and the work W are placed between each other. The heat conductivity is improved.

  The resin sheet 36 needs to have sufficient heat resistance (for example, 250 ° C. or higher at continuous use temperature) in consideration of the passage of the heating unit 14, and has an appropriate thinness in consideration of the thermal conductivity ( For example, the thickness is preferably about 0.24 mm.

  As such a resin sheet 36, a fluorine resin material such as PTFE (polytetrafluoroethylene) or PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) can be suitably used, but the continuous use temperature is predetermined. Any resin material having a temperature of (for example, 250 ° C.) or higher is applicable. In addition, the fluororesin material such as PTFE has a continuous use temperature of 260 ° C., has a very high heat resistance, is flame retardant, has elasticity, and has a very low wear and friction coefficient. Is preferred. The resin sheet 36 has a thickness of, for example, about 0.24 mm and is relatively thin and has an appropriate elasticity. Therefore, the roller driving units 32a and 32b can be rolled without causing cracks or dropping off.

  The resin sheet 36 is detachably laid on the work placement portion 34 of the belt conveyor 21 so that it can be easily replaced when it is necessary to replace the resin sheet 36 due to deterioration over time.

  The carry-in portion 12 is a portion on which the work W (the substrate 20 supported by the work jig 19) is placed on the placement surface 34a (resin sheet 36) exposed to the outside from the opening 30a of the apparatus main body 30. , Located on the most upstream side of the conveying means 22.

  The heating section 14 is provided on the downstream side of the carry-in section 12 and is disposed between the forward path and the return path of the belt conveyor 21 to heat the workpiece W from below, and the heating plate section 38 and the belt. And an infrared heater 40 which is disposed opposite to the conveyor 21 and heats the workpiece W from above. A warm air fan 42 is disposed close to the infrared heater 40. For example, a heater 38a is accommodated in the heating plate portion 38 (see FIG. 4). The infrared heater 40 and the warm air fan 42 are disposed inside an apparatus upper cover 44 provided above the apparatus main body 30, and the belt conveyor 21 passes under the apparatus upper cover 44 in a tunnel shape.

  Six infrared heaters 40, hot air fans 42 and heating plate portions 38 are arranged in parallel in the direction of conveyance of the workpiece W. For example, temperature adjustment up to 300 ° C. can be performed in six zones using a digital temperature controller. PID control. For this reason, the preliminary heating process, the main heating process, and the like for the workpiece W can be easily and flexibly set.

  As described above, in the heating unit 14, the workpiece W passing by the belt conveyor 21 is radiantly heated from the upper part by the infrared heater 40 and the hot air fan 42, and directly (conducted) by the heating plate unit 38 from the lower part. Thus, the workpiece W can be heated sufficiently and quickly so as to sandwich the workpiece W from above and below. Thereby, the variation of the temperature distribution in the board | substrate 20 can be made small, and the thermal load (damage) to the mounting component 60 mounted in a board | substrate can be suppressed. At this time, the heat of the heating plate portion 38 that heats the workpiece W from below is transmitted from the workpiece mounting portion 34 to the workpiece W via the resin sheet 36.

  Note that if the number of infrared heaters 40 and heating plate portions 38 is increased and finer zone division is performed, the temperature in the reflow apparatus 10 can be controlled more finely in multiple stages. Can be further reduced.

  In order to prevent an excessive temperature rise (overheating) in the heating unit 14, the reflow device 10 also performs temperature management using a thermostat (not shown).

  The cooling unit 16 is a part that cools the workpiece W including the substrate 20 heated by the heating unit 14 and subjected to reflow soldering. The cooling unit 16 includes a water cooling unit 46 that directly (conductively) cools the workpiece W from below by circulating cooling water, and a cooling fan 48 that cools the workpiece W from above. The cooling fan 48 is not necessarily installed and may be installed as appropriate.

  The water cooling unit 46 is disposed between the forward path and the return path of the belt conveyor 21 and cools the workpiece W, and the cooling water heated by cooling the workpiece W with the cooling plate unit 50. And a cooler 54 introduced through a circulation path 52. The cooling plate unit 50 is configured as a heat exchanger in which piping (not shown) connected to the circulation path 52 is arranged in a meandering shape, for example. The cooler 54 is a device that cools the heated cooling water and recirculates it to the circulation path 52, and includes a cooling pump 56, a cooling fan (not shown), and the like. In the cooler 54, for example, a pipe (not shown) connected to the circulation path 52 may be arranged in a meandering shape and cooled using the cooling fan or the like.

  In such a cooling unit 16, the temperature of the circulating cooling water is set to, for example, 5 ° C to 35 ° C. The temperature of the cooling plate unit 50 is detected by a resistance temperature detector or the like and fed back to the cooler 54 for temperature management.

  The unloading section 18 is continuously arranged from the downstream end of the belt conveyor 21. When the work W conveyed by the belt conveyor 21 is slid onto the rotating roller section 24, the rotating roller section Stop smoothly on 24. For this reason, an operator or a predetermined robot (automatic machine) can easily carry out the workpiece W that has been reflow soldered and cooled to a predetermined temperature (for example, 60 ° C.). In addition, since the cooling fan 57 is installed in the upper part of the carrying-out part 18 and the workpiece | work W cooled by the cooling part 16 can be cooled more fully, a carrying-out operation | work can be performed more rapidly.

  Next, the workpiece | work W is demonstrated with reference to FIG.3 and FIG.4. FIG. 3 is a schematic sectional side view in which the work jig 19 and the substrate 20 constituting the work W are disassembled. FIG. 4 is a partially omitted cross-sectional view taken along line IV-IV in FIG. 2 and shows the workpiece W heated by the heating unit 14 while being transported by the transport means 22.

  As described above, the workpiece W is obtained by supporting the substrate 20 on which the reflow soldering is performed by the reflow apparatus 10 with the workpiece jig 19. As shown in FIG. 3, a printed circuit board 62 on which a wiring pattern is printed and a mounting component 60 is soldered is attached to a substrate 20 on a metal substrate 58, and the periphery of the metal substrate 58 and the printed circuit board 62 is attached. It is configured to be surrounded by a substrate case 64.

  The metal substrate 58 is made of, for example, aluminum, improves the rigidity of the substrate 20, and functions as a heat dissipation portion when the substrate 20 is mounted on a mounting target such as an automobile. Examples of the mounting component 60 include electrical components such as aluminum electrolytic capacitors, resistors, and semiconductor components. The substrate case 64 functions as an attachment portion when the substrate 20 is mounted on, for example, an automobile.

  The work jig 19 is provided with a support base (substrate support portion, shim) 65 on the upper surface, and is placed on the plate portion (jig plate portion) 66 on which the substrate 20 is placed, and the plate portion 66. And a positioning portion (jig positioning portion) 68 for positioning the substrate 20. Further, the work jig 19 is provided with a handling part (jig handling part) 70 for fixing and supporting the substrate 20 positioned and placed by the plate part 66 and the positioning part 68.

  As shown in FIG. 5, three support tables 65 are provided on the upper surface of the plate portion 66, that is, the plate portion 66 supports the substrate 20 at three points via the support table 65. In this case, the height of the support base 65 is set to 0.08 mm to 0.12 mm, and particularly preferably set to 0.1 mm. Further, the area of the surface where one support 65 contacts the substrate 20 is set to 0.28% to 0.83% of the area of the substrate 20 (metal substrate 58), particularly preferably about 0.6%. Set to Note that, for example, three support points 65 provided with three support bases 65 are more securely in contact with each other than the four point support provided with four, and there is no backlash, and the stability of the substrate 20 is high. Are provided on the plate portion 66.

  The handling unit 70 is provided with two columns 72 standing on the left and right ends of the upper surface of the plate unit 66, and is movable in the axial direction (vertical direction) of the column 72, and is positioned and fixed (not shown). The movable plate 74 is positioned and fixed at a desired position (height) by means.

  Therefore, in the workpiece W, after the substrate 20 is placed on the plate portion 66 (support base 65) under the positioning action of the positioning portion 68, the movable plate 74 is pushed down and sandwiched, and the movable plate 74 is held at a desired position. By fixing, the substrate 20 is reliably supported by the work jig 19 (see FIG. 4). Thereby, in the workpiece | work W, the position shift of the board | substrate 20 during conveyance with the belt conveyor 21 is prevented. Further, an operator or a predetermined robot (automatic machine) can easily handle the workpiece W by holding the handling unit 70 (movable plate 74), and the workability in the carry-in unit 12 and the carry-out unit 18 is improved. .

  In such a work jig 19, at least the plate portion 66 including the support base 65 is formed of titanium, for example. Of course, all the elements constituting the work jig 19 may be formed of titanium. Titanium has an excellent corrosion resistance because it forms an oxide film at room temperature, is less susceptible to rust, and has a good maintainability because it can easily remove contaminants such as dirt and dust on the surface. The specific gravity of titanium is a relatively light metal located between iron and aluminum, while it has a relatively high strength as a practical metal, but has a relatively good workability.

  Note that the work jig 19 may be formed of a stainless steel, aluminum or iron material, but in this case, when repeatedly used in the reflow apparatus 10, warping or twisting may occur due to heating or cooling. There is. However, titanium is a cemented carbide that has a relatively high melting point and hardly undergoes thermal shrinkage, and can effectively prevent the warping and twisting, and thus is particularly suitable as a material for the plate portion 66.

  Further, for example, when the plate portion 66 is formed of aluminum with respect to the metal substrate 58 formed of aluminum, wear of the support base 65 and the plate portion 66 which are jigs is promoted. On the other hand, in the case of titanium, wear over time can be delayed. For the work jig 19, for example, any material containing titanium such as JIS type 2 (JIS H4650) pure titanium or titanium alloy can be used effectively.

  As described above, in the workpiece W conveyed by the heating unit 14, the heat from the heating plate unit 38 is conducted to the plate unit 66 of the workpiece jig 19 through the belt conveyor 21 and the resin sheet 36, and the plate It is conducted with high efficiency from the portion 66 to the substrate 20 via the support base 65 (see FIG. 4).

  In this case, the heat transfer from the heating plate portion 38 to the substrate 20 is made uniform, and the temperature distribution on the substrate 20 is made uniform, so that the reflow soldering of the mounting component 60 can be performed reliably. That is, when designing the plate portion 66 including the support base 65 formed of titanium as described above (in this case, pure titanium JIS type 2), the following heat transfer of (a) to (c) is considered. There is a need. That is, (a) "heat conduction" which is the movement of heat in the solid, (b) "heat transfer" which is the movement of heat from the solid to the fluid (liquid or gas), (c) radiating electromagnetic waves. It is "heat radiation" that is the movement of heat by.

  By the way, when the plate portion 66 is brought into contact with the metal substrate 58 constituting the substrate 20 at a point, wear occurs at the point contact portion, so that the heat conduction from the plate portion 66 to the metal substrate 58 takes place over time. Changes will occur. Therefore, in order to reduce such wear, even if the plate portion 66 and the metal substrate 58 are brought into contact with each other on a wide surface, they eventually come into contact at some unspecified points within the contact surface. For this reason, variations in heat conduction and heat transfer occur, and the temperature distribution of the substrate 20 becomes non-uniform. Therefore, the contact between the metal substrate 58 and the plate portion 66 (support base 65) needs to be a surface larger than the point and smaller than the entire surface, and wear must be minimized.

In the present embodiment, the height of the support base 65 (hereinafter also referred to as the support base height) is set to a very small value, for example, 0.1 mm, so that heat conduction is higher than heat transfer. It becomes sufficiently large and the heat transfer during heat transfer is extremely small. That is, the heat quantity by heat conduction is Q1 [J], the heat quantity by heat transfer is Q2 [J], the heat conductivity is λ [W / (m · K)], and the heat transfer coefficient is h [W / (m ² · K). )], The rising temperature is ΔT [K], the height of the support base (shim height) is d [m], and the area of the substrate 20 (metal substrate 58) (hereinafter also referred to as the substrate area) is S1 [m ² ]. When the heating time (temperature rise time) is t [s], the heat quantities Q1 and Q2 are expressed by the following equations (1) and (2).
Q1 = λ · ΔT / d · S1 · t (1)
Q2 = h · ΔT · S1 · t (2)

Here, the thermal conductivity of titanium constituting the support base 65 and the plate portion 66 is λ = 21.9 [W / (m · K)], and the heat transfer coefficient h of stationary air is h = 4.64 [W / (M ² · K)], Q1 / Q2 = λ / (h · d) = 4.72 · 10 ⁴ when Q1 and Q2 are compared. Thereby, it is easily understood that the influence of heat conduction is extremely large compared to heat transfer.

  Furthermore, the heat radiation from the infrared heater 40 that heats the workpiece W from the upper part is extremely small compared to the heat conduction, and the heating unit 14 is not equipped with anything that generates electromagnetic waves. It can be said that the heat transfer at is very small. Therefore, the movement of heat to the workpiece W in the heating unit 14 becomes substantially accurate by considering heat conduction.

  Therefore, first, an examination experiment for setting the area of the surface where the support table contacts the substrate 20 (hereinafter also referred to as the support table area) was performed.

That is, as shown in FIG. 6, an experiment was performed in which the test work TW on which the substrate 20 was placed on the test jig 80 was heat-treated with the reflow apparatus 10. In this case, the height d (support height d) of the test support base 84 provided on the test plate portion 82 is 0.1 mm, and the support base area (shim area) S2 is 5 mm ² , 60 mm ² , 500 mm ^2. , 1000 mm ² , and 1500 m ^2, and the temperature of the substrate 20 was measured with a thermocouple (not shown), so that the influence of the support area S2 on the temperature of the substrate 20 was examined. In addition, the temperature measurement position was set to the temperature T1 at the central portion where the temperature is considered to be the highest and the temperature T2 at the end where the temperature is considered to be the lowest. Further, the flatness of the surface (upper surface) of the test support base 84 brought into contact with the substrate 20 (metal substrate 58) was set to 0.05 mm. The number of experiments was two.

  FIG. 7 is a graph showing the relationship between the support base area S2 when heated by the heating unit 14 and the temperatures T1 and T2 of the substrate 20 constituting the test work TW.

As shown in FIG. 7, the support base area S2 is 60 mm ² , and the temperature difference between the temperature T1 at the center of the substrate 20 and the temperature T2 at the end is the smallest, that is, the temperature distribution on the substrate 20 varies. There were few.

In this case, when the support base area S2 is smaller than 30 mm ² , the thermal difference is small and the temperature difference between the center portion T1 and the end portion T2 tends to increase. It was shown that the lead-free solder recommended lower temperature (230 ° C) may be exceeded. Further, when the support base area S2 is larger than 90 mm ^2, the influence of the flatness on the upper surface of the test support base 84 is increased, and thus the temperature variation tends to increase at each of the temperatures T1 and T2. . Accordingly, a support area S2 is preferably 30mm ² ~90mm ^2, in particular, results of a 60 mm ² preferably is obtained.

  Next, a test experiment for setting the support base height d was performed using the test work TW shown in FIG. 6 in the same manner as the test experiment for setting the support base area S2.

In this case, the support base area S2 is set to 60 mm ² and the height d (support base height d) of the test support base 84 is changed to 0 mm, 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, By measuring the temperature of the substrate 20 with a thermocouple, the influence of the height d of the support base on the temperature of the substrate 20 was examined. Note that the experimental conditions such as the temperature measurement position and the flatness of the test support base 84 were the same as in the examination experiment for setting the support base area S2. The number of experiments was 3 times.

  FIG. 8 is a graph showing the relationship between the height d of the support base when heated by the heating unit 14 and the temperatures T1 and T2 of the substrate 20 constituting the test work TW.

  As shown in FIG. 8, when the support base height d is 0 mm, the entire surface is brought into contact, resulting in excessive heat conduction. As a result, the mounting component recommended upper limit temperature (250 ° C.) is exceeded, and there are some problems in the entire contact surface. Due to the contact at a specific point, the variation in temperature distribution tended to increase. This showed the same tendency when the support height d was smaller than 0.08 mm.

  On the other hand, when the height d of the support base is larger than 0.12 mm, it is shown that the heat conduction is small and the temperature is lower than the recommended lower limit temperature of lead-free solder (220 ° C.). Furthermore, in such a case, the heat conduction decreased, and the variation in temperature distribution tended to increase due to the effect of no change in heat transfer. This is because the heat transfer is not affected by the height d of the support base, and the heat conduction decreases as the height d of the support base increases.

  Accordingly, the result is that the support height d is preferably 0.08 mm to 0.12 mm, and particularly preferably 0.1 [mm].

Incidentally, when the support base area S2 and 30mm ² ~90mm ² is a preferred range obtained by the above study experiment, the area of the support per the substrate area S1 of the substrate 20 shown in the following equation (3), i.e. The ratio of the support table area S2 can be calculated as shown in the following equations (4) to (6).
S1 = 120 · 90 = 10800 [mm ² ] (3)
S2 / S1 = 30/10800 · 100 = 0.28 [%] (4)
S2 / S1 = 60/10800 · 100 = 0.56 [%] (5)
S2 / S1 = 90/10800 · 100 = 0.83 [%] (6)

  Therefore, in the case of the reflow apparatus 10 according to the present embodiment, the support base area S2 that is an area per support base 65 constituting the work jig 19 is smaller than the substrate area S1 that is the area of the substrate 20. It is preferably 0.28% to 0.83%, and particularly preferably about 0.6%.

  And in the reflow apparatus 10 comprised as mentioned above, the temperature profile (temporal change of a temperature) for equalizing and optimizing the temperature distribution of the board | substrate 20 is set and performed, and the work W is made more Heat evenly.

  Such a temperature profile is based on these specifications in order to prevent damage or expansion (deformation) of the printed circuit board 62 mounted on the substrate 20 or the mounting component 60 (for example, electrolytic capacitor) having low heat resistance. Must be set. In this case, when reflow soldering is performed outside the recommended range of the mounting component 60, the reliability of the product is lowered. Furthermore, in the case of lead-free solder, when soldering is performed at a temperature lower than the recommended lower limit temperature (230 ° C.), mounting defects such as insufficient flux activity and unwelded solder may occur.

  Further, the substrate 20 constituting the workpiece W is composed of a metal substrate 58. For this reason, since the heat capacity of the metal part (aluminum) on the metal substrate 58 is large, it is necessary to cool the workpiece W after heating rapidly. If the cooling rate is slow, the workpiece W is released from the metal substrate 58. Due to this heat, a thermal load (damage) is applied to the printed circuit board 62 and the mounting component 60. For this reason, in the cooling part 16, the workpiece | work W after a heating shall be rapidly cooled by performing forced cooling with the water cooling part 46 and the cooling fan 48 which have the cooling plate part 50. FIG. Then, there is an advantage that the cooling time is shortened and the entire cycle time can be shortened.

  Therefore, the temperature profile in the reflow apparatus 10 according to the present embodiment is such that the substrate 20 has the highest temperature T1 at the center, the lowest temperature T2 at which the temperature is lowest, and the highest temperature. It is set based on each temperature condition of the upper temperature T3 of the electrolytic capacitor (not shown) that is considered to be the mounting component 60 having a large influence.

  As such a temperature condition, first, in the heating unit 14, all the temperatures of the substrate 20 are in the range of the temperatures T <b> 1 to T <b> 2, and the mounting component 60 needs to be within the recommended upper limit temperature of 250 ° C. It is said.

  Secondly, it is necessary that the temperature conditions of the mounting component 60 with low heat resistance, for example, an electrolytic capacitor satisfy the following (d) to (f). That is, (d) the preheating step is performed at 160 [° C.] for 120 [s], (e) the maximum heating step of 230 [° C.] is performed for 5 [s], and (f) the cooling step is performed at 200 [° C. It is to cool at -1 [° C / s] until the following.

  FIG. 9 shows a temperature profile based on the first and second temperature conditions. As shown in FIG. 9, in the reflow apparatus 10, in the state where the temperature T <b> 1 at the central portion considered to be the highest in the substrate 20 is shown in the temperature profile T <b> 1, the temperature T <b> 2 at the end considered to be the lowest is In the state shown in the temperature profile T2, the upper temperature T3 of the electrolytic capacitor considered to be the mounting component 60 having the greatest thermal influence is heated and cooled in the state shown in the temperature profile T3.

  That is, the workpiece W is subjected to a preheating step and a main heating step in the heating unit 14, a cooling step is performed in the cooling unit 16, and a carrying out process in the unloading unit 18 following the carrying-in process of the carry-in unit 12. It is carried out.

  In this case, in the temperature profile T3, the upper heat resistance temperature (160 ° C.) of the electrolytic capacitor is set in the preheating step, and is lower than the heat resistance temperature (240 ° C.) of the lower portion, which is a soldered portion of the electrolytic capacitor, in the main heating step. The recommended lower temperature limit for lead-free solder (230 ° C). Thereby, reflow soldering can be reliably performed without damaging the electrolytic capacitor considered to be the mounting component 60 having the greatest thermal influence. Moreover, since the temperature profile T1 is also set to the recommended upper limit temperature (250 ° C.) of the mounted component in the main heating step, the thermal load on the mounted component can be further reduced. On the other hand, since the temperature profile T2 is set to the recommended lower limit temperature (230 ° C.) of lead-free solder in this heating step, reflow soldering can be performed reliably.

  As described above, according to the temperature profiles T <b> 1 to T <b> 3, the uniformity of the temperature distribution of the substrate 20 can be further improved by using the work jig 19 having the plate portion 66 and the support base 65 formed of titanium. it can.

  In this case, heat from the heating plate portion 38 is conducted from the lower part of the work W to the substrate 20 through the resin sheet 36. Similarly, heat from the substrate 20 is conducted to the cooling plate unit 50 via the resin sheet 36. For this reason, even if it is the board | substrate 20 comprised from the metal substrate 58 with a large heat capacity, the temperature can be made to track rapidly each said temperature profile T1-T3, and the thermal to the mounting components 60 of the board | substrate 20 is carried out. While preventing damage due to the load, the cycle time can be shortened.

  That is, it is possible to effectively reduce the temperature difference between the mounting component 60 provided at the center of the substrate where the temperature is likely to rise and the mounting component 60 provided at the end of the substrate where the temperature is difficult to rise. The thermal load on the mounting component 60 can be reduced.

  Furthermore, in the cooling process in the temperature profiles T1 to T3, since cooling is performed at -1 [° C / s] up to 200 [° C] or less, the metal substrate 58 includes a metal portion (aluminum portion) having a large heat capacity. Also in the board | substrate 20, it is prevented effectively that the printed circuit board 62 and the mounting component 60 receive a thermal load by the influence of the heat from the metal part after a heating.

  Further, in this heating process, the temperature of each part of the substrate 20 can be surely set to the melting point (220 ° C.) or higher of the lead-free solder, so that the lead-free solder is not melted and the reliability of the substrate 20 is improved. Can be made.

  Further, as described above, since the temperature difference on the substrate 20 can be further reduced, there is an advantage that a temperature profile can be easily created.

  In the said embodiment, you may make it carry in and carry out the workpiece | work W in the carrying-in part 12 and the carrying-out part 18 using the robot which is not shown in figure.

  Moreover, in the heating part 14, the infrared heater 40 may be changed into a far infrared heater, and the heating plate part 38 may be changed into an infrared heater or a far infrared heater.

  It should be noted that the present invention is not limited to the above-described embodiment, and it is naturally possible to adopt various configurations without departing from the gist of the present invention.

It is a schematic side view which shows the structure of the reflow apparatus which concerns on one Embodiment of this invention. It is a schematic plan view which shows the conveyance means of the reflow apparatus shown in FIG. It is a schematic sectional side view which decomposed | disassembled the workpiece jig | tool and board | substrate which comprise a workpiece | work. FIG. 4 is a partially omitted cross-sectional view taken along line IV-IV in FIG. 2. It is a schematic plan view which shows the plate part of the workpiece jig which comprises a workpiece | work. FIG. 6 is a schematic cross-sectional side view showing a test work for setting the specifications of the plate portion shown in FIG. 5. It is a graph which shows the relationship between the support stand area S2 at the time of being heated by the heating part shown in FIG. 1, and the temperature of the board | substrate which comprises a test work. It is a graph which shows the relationship between the support stand height d at the time of being heated by the heating part shown in FIG. 1, and the temperature of the board | substrate which comprises a test work. It is a figure which shows the temperature profile used for the reflow apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Reflow apparatus 12 ... Carry-in part 14 ... Heating part 16 ... Cooling part 18 ... Unloading part 19 ... Work jig 20 ... Substrate 21 ... Belt conveyor 22 ... Conveying means 26 ... Control part 30 ... Apparatus body 34 ... Work place part 34a ... Placement surface 36 ... Resin sheet 38 ... Heating plate part 40 ... Infrared heater 46 ... Water cooling part 50 ... Cooling plate part 58 ... Metal substrate 60 ... Mounting component 62 ... Printed circuit board 64 ... Substrate case 65 ... Support base 66 ... Plate Part 68 ... Positioning part 70 ... Handling part W ... Workpiece

Claims (5)

Transport means for transporting a substrate on which electrical components are arranged;
A heating unit that performs reflow soldering of the electrical component after preheating the substrate;
A reflow apparatus having a cooling unit for cooling the reflow soldered substrate,
The transport means is provided with a work placement portion in which a placement surface on which the substrate is placed is made of a resin material,
The heating part is provided with a heating plate part for heating the lower part of the work placing part,
The cooling part is provided with a cooling plate part for cooling the lower part of the work placing part ,
Furthermore, it has a work jig for supporting the substrate placed on the work placement unit,
The work jig is a jig plate portion disposed between the mounting surface and the substrate,
A substrate support portion provided on a surface of the jig plate portion on the substrate side and supporting the substrate with a support surface at a predetermined height position from the jig plate portion;
The area of the support surface is 0.28 to 0.83% with respect to the area of the substrate with which the support surface abuts,
The height of the said board | substrate support part is a height which sets to 0.08-0.12 mm between the said jig | tool plate part and the said board | substrate, The reflow apparatus characterized by the above-mentioned . The reflow device according to claim 1,
The resin material has a continuous use temperature of 250 ° C. or higher. The reflow device according to claim 1,
The reflow apparatus, wherein the resin material is a fluororesin. The reflow device according to claim 1,
The substrate support unit supports the substrate by the three support surfaces, and the area of the support surface per piece is 0.28 to 0.83 with respect to the area of the substrate with which the support surface abuts. % Reflow device. The reflow device according to claim 4 , wherein
The jig plate portion and the substrate support portion are made of a metal containing titanium, and the reflow apparatus is characterized in that

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