JP2009200072A - Reflow soldering apparatus and reflow soldering method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflow soldering apparatus easily heating components whose temperature does not rise easily, components whose temperature rises easily, and components weak to heat; or heating components whose temperature does not rise easily and a substrate surface weak to heat, up to the same temperature, in the reflow soldering apparatus which heats a printed circuit board mixedly mounting components whose temperature does not rise easily, components whose temperature rises easily, and components weak to heat by convection heating of hot air and radiation heating of a heater. <P>SOLUTION: The reflow soldering apparatus includes: a conveying means for a substrate mounted with components to be soldered; and upper and lower panel heaters for vertically heating the substrate placed in the conveying means. A number of blowout holes are provided at least in the upper panel heater, and a fan is installed at an upper portion of the upper panel heater. In the reflow soldering apparatus, the width direction of at least the upper panel heater is divided along a conveyance direction, upper panel heaters 3AZ, 3BZ, 3CZ including a plurality of areas having a number of blowout holes 3h are arranged, and setting temperature can be changed for each divided area. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a reflow soldering apparatus that heats a soldering portion of a board in order to electrically connect the solder mounted on the board such as a printed board.

  There is a technique for mounting an electronic device for configuring various circuits on a substrate on which various circuits of the electronic device are configured, for example, a printed circuit board. An electronic component such as a mounted chip component is electrically connected to a wiring portion of a printed board by soldering, and reflow soldering is usually performed as such a soldering technique. Reflow soldering is a soldering technique in which cream solder or the like is applied to a predetermined portion of a printed circuit board and then a soldered portion of the printed circuit board is heated in a reflow furnace.

  A reflow soldering apparatus for performing such reflow soldering includes a preheating zone, an intermediate heating zone, and a reflow heating arranged in a conveying direction of the conveyor on a main body of a reflow soldering apparatus to which a conveyor for conveying a printed board is attached. The printed circuit board and the entire electronic component mounted thereon are heated by heating means provided in each of the zones. As a heating means, one that heats by blowing hot air and one that uses heating by an infrared heater in addition thereto are known.

  However, since various electronic components are mixedly mounted in the printed circuit board, there is always a difference in heat capacity depending on the location of the heated portion in the substrate heating method in the conventional reflow soldering apparatus. Since each electronic component has a heat-resistant temperature and a heat-resistant guarantee time, it is required to minimize temperature variations in the substrate within a certain time. However, simply heating a printed circuit board with a mixture of large parts that are difficult to heat up or heat-sensitive parts by convection heating with hot air or radiant heating of the heater for a certain period of time. There is a problem in that it may not be within the predetermined range.

In order to solve the above problems, the temperature of the entire mounting board is raised by heat transfer heating using hot air as a heat source, and the portion to be heated that is difficult to raise is locally blown with a gas to transfer heat. There is known an invention of a reflow board heating method and apparatus capable of improving the temperature and heating up to a predetermined temperature and reflow soldering components that are difficult to increase in temperature and components that are vulnerable to heat (see Patent Document 1).
JP 2002-16352 A

Further, in the reflow soldering method for performing heating by hot air and radiant heat in at least one heating zone of a reflow furnace, the temperature of the hot air in at least one heating zone of the heating zone is set higher than a target temperature of the heating zone. An invention of a method for lowering the temperature is also known (see Patent Document 2).
JP-A-11-54903

Further, in the reflow soldering method, in response to the thermal load in the width direction of the circuit board to which the solder is applied, a hot gas having a uniform wind speed at different temperatures is divided into a plurality of width directions of the circuit board. An invention of a method of circulating and circulating the hot gas to be treated is known (see Patent Document 3).
JP-A-6-224545

  In addition, the development of solder that does not use toxic lead, that is, lead-free solder and its soldering technology, has been carried out, but lead-free solder that can achieve solderability equivalent to conventional solder containing lead Generally, its melting point is high. For example, Sn-Ag-Cu-based lead-free solder has a melting point of about 210 to 220 ° C., which is significantly higher than the melting point of Sn—Pb eutectic solder (about 183 ° C.) conventionally used. is there.

  However, the heat resistance temperature of electronic components for reflow soldering that are generally used at present is about 240 ° C., and only a temperature margin of about 20-30 ° C. compared with the melting point of lead-free solder, that is, the melting temperature. No (conventional temperature margin of about 50 to 80 ° C.).

  However, with such a slight temperature margin, sufficient heat of fusion is supplied to the solder of the parts to be soldered that exist on each part of the printed circuit board, and many electrons with different shapes, sizes, materials, hues, heat capacities, etc. There is a problem that it is difficult to perform uniform soldering by heating so that the temperature of the part to be soldered becomes uniform.

As an invention that solves the above problems and aims to perform uniform reflow soldering by uniformly melting lead-free solder within a slight temperature margin considering the heat-resistant temperature of electronic components, There is known an invention of a reflow soldering device characterized by the shape of the blowing surface of a hot air blowing nozzle for blowing hot air to a workpiece to be soldered and the flow of sucking and exhausting the blown hot air (See Patent Document 4).
Japanese Patent Laid-Open No. 2001-14427

  However, by controlling the hot air as in the inventions described in Patent Documents 1 to 4, when the printed circuit board is mounted with components that are difficult to rise in temperature and heat-sensitive components, the thermal load in the width direction is different, or lead When free solder is used and there is only a slight temperature margin considering the heat-resistant temperature of electronic parts, it is possible to heat evenly to some extent, but fine control is difficult and there are aspects that are not sufficient .

On the other hand, in the reflow soldering apparatus by heating only the heater that does not use convection heating of hot air, `` in the reflow apparatus that heats the printed wiring board in the furnace body and reflow solders the mounted components to the printed wiring board, A reflow apparatus comprising a plurality of local heating means capable of heating each part of the printed wiring board is known, and “a printed wiring board on which mounted components are mounted is uniformly heated. The printed wiring board is heated by a plurality of local heating means having such a temperature distribution pattern, and the temperature difference between the mounting component that easily rises in temperature and the mounting component that hardly rises in temperature can be reduced. It is shown that there exists an effect called "" (refer patent document 5).
JP 2002-324972 A

In addition, “in a reflow soldering apparatus in which solder is supplied to a printed board in advance, and the solder is heated and melted while the printed board is conveyed in a furnace by a conveyor, the conveying direction of the conveyor and A partition plate in the same direction divides the inside of the furnace into a plurality of directions perpendicular to the conveying direction of the conveyor, and for each of the divided areas, a temperature sensor for measuring the temperature of the area and heating the area. And a controller for controlling each heater on the basis of temperature data from the temperature sensor. The invention of “a reflow soldering apparatus” is known. The temperature can be finely adjusted according to the rate, so soldering can be performed under optimum conditions. ” (See Patent Document 6).
JP-A-10-145037

  However, the inventions described in Patent Documents 5 and 6 are only related to a reflow soldering apparatus that heats only by radiant heating of a heater, and reflow solder that heats a printed circuit board by convection heating of hot air and radiant heating of the heater. It is not suggested to apply to the attaching device.

  The present invention is intended to solve the above-described problems, and convection heating with hot air is applied to a printed circuit board in which components that are difficult to increase in temperature, components that are likely to increase in temperature, and components that are susceptible to heat are mixed. To provide a reflow soldering apparatus capable of easily heating these components or a component that is difficult to increase in temperature and a substrate surface that is susceptible to heat to the same temperature in a reflow soldering device that is heated by radiant heating of a heater. Another object of the present invention is to provide a reflow soldering method capable of simultaneously transporting substrates having different thermal loads and realizing different temperature profiles.

The present invention employs the following means in order to solve the above problems.
(1) A board conveying means on which a component to be soldered is mounted, an upper panel heater and a lower panel heater for heating the board placed on the conveying means from above and below, and at least a large number of the upper panel heaters. In a reflow soldering apparatus in which an ejection hole is provided and a fan is installed above the upper panel heater, the width direction of the upper panel heater is divided along the conveying direction, and a plurality of ejection holes are provided. The reflow soldering apparatus is characterized in that an upper panel heater composed of the above areas is configured, and the set temperature can be changed for each of the divided areas.
(2) Further, the width direction of the lower panel heater is divided along the conveying direction to form a lower panel heater composed of a plurality of areas, and the set temperature can be changed for each of the divided areas. The reflow soldering apparatus according to (1), which is characterized in that
(3) In the reflow soldering apparatus according to (1) or (2), the lower panel heater is provided with a number of ejection holes, and a fan is installed below the lower panel heater. is there.
(4) A plurality of areas of the upper panel heater, or a plurality of areas of the upper panel heater and the lower panel heater are divided into two or three areas, and at least one area has a higher temperature than the other areas. The reflow soldering apparatus according to any one of the above (1) to (3), wherein the reflow soldering apparatus is set.
(5) The upper panel heater and the lower panel heater are arranged three or more in the transport direction, and a preheating zone, an intermediate heating zone, and a reflow heating zone are configured. The reflow soldering apparatus according to any one of 4).
(6) A reflow soldering method using the reflow soldering apparatus according to any one of (1) to (5) above, wherein a plurality of areas of the upper panel heater, or the upper panel heater and the lower panel In this reflow soldering method, a plurality of substrates having different thermal loads are simultaneously transported along each of the areas divided into a plurality of areas of the heater.

  The present invention divides the width direction of a panel heater having a large number of ejection holes along the conveying direction to constitute a panel heater composed of a plurality of areas having a large number of ejection holes, and for each divided area. Since the set temperature can be changed, it is possible to easily uniformly heat a printed circuit board on which a component that is difficult to increase in temperature, a component that is likely to increase in temperature, or a component that is vulnerable to heat to be mounted to the same temperature. Also, different temperature profiles can be realized by simultaneously transporting substrates having different thermal loads. Furthermore, even when lead-free solder having a melting point of about 210 to 220 ° C. is used, the heat of fusion sufficient for the solder of the part to be soldered present on each part of the printed circuit board within a slight temperature margin up to about 240 ° C. Can be supplied.

The reflow soldering apparatus of the present invention has the same basic configuration as a conventional reflow soldering apparatus using both hot air and heating by an infrared heater, and a schematic diagram thereof is shown in FIG.
As shown in FIG. 1, a reflow soldering apparatus (heating furnace) (1) for heating and soldering a printed circuit board W on which components to be soldered are mounted, and the printed circuit board W in the heating furnace (1). The conveyance means (conveyance conveyor) (2), such as a pin chain conveyor and a mesh conveyor, which are conveyed in the direction of the arrow from the carry-in entrance to the carry-out exit, and the printed circuit board W placed on the carry conveyor (2) are heated from above and below. The upper panel heater (3), the lower panel heater (4), and the fan (5) installed above the upper panel heater (3) are provided.
Here, the printed circuit board W is a board in which a circuit is formed with a copper pattern or the like on an insulating material such as glass epoxy, and is mounted with components to be soldered after applying cream solder thereto.

In a normal case, the heating furnace (1) is composed of a preheating zone (6), an intermediate heating zone (7), a reflow heating zone (main heating zone) (8), and a cooling zone (9).
It is not divided into a preheating zone, an intermediate heating zone, and a reflow heating zone, and all functions can be provided by only one zone.
Each zone will be described in more detail.

In the preheating zone (6), an upper panel heater (3X) by infrared heating having a large number of ejection holes (3h) is arranged above the conveyor (2), and also below the conveyor (2). A lower panel heater (4X) is provided by infrared heating, and radiates and heats the printed circuit board W while controlling the temperature based on a predetermined temperature profile.
In addition, a fan (5) is provided on the ceiling wall of the preheating zone (6) above the upper panel heater (3X), and air or nitrogen gas, which is an atmospheric gas in the heating furnace (1), is supplied to the upper wall of the preheating zone (6). The printed circuit board W is blown onto the printed circuit board W so as to pass through a number of ejection holes (3h) of the panel heater (3X), and hot air heated by the panel heaters (3X) and (4X) is circulated to convectionly heat the printed circuit board W. To do. At that time, a rectifying plate is provided between the upper panel heater (3X) and the fan (5), and the air sent downward from the fan (5) is rectified by passing through the rectifying plate, and the upper panel heater (3X). You may make it reach.
Furthermore, in order to efficiently circulate hot air, it is preferable to provide a large number of ejection holes in the lower panel heater (4X). In that case, even if a fan is installed below the lower panel heater (4X) good.
In the preheating zone (6), the conveyed product (printed circuit board W) is heated from room temperature to a temperature of 130 to 150 ° C or 130 to 200 ° C.

Temperature data is acquired by attaching a thermocouple to the conveyed product. The temperature of the apparatus is set so that the acquired temperature data becomes a target profile.
As an example, the temperature of the hot air is detected by a hot air temperature sensor (10) disposed at a distance of 1 to 3 mm from the panel surface at the center of a number of ejection holes (3h) in the middle of the upper panel heater (3X), Control is performed by changing the power of one or both of the upper panel heater (3X) and the lower panel heater (4X) so as to eliminate the temperature difference compared with the set reference temperature of hot air.
The control method is the same in the intermediate heating zone and the reflow heating zone described below.

In the intermediate heating zone (7), the upper panel heater (3Y) and the lower panel heater (4Y) follow the upper panel heater (3X) and the lower panel heater (4X) in the preheating zone (6), respectively. The upper panel heater (3Y) is similarly provided with an ejection hole (3h), and a fan (5) is disposed above it.
In the intermediate heating zone (7), the printed circuit board W is heated to 130 to 200 ° C., typically 150 to 180 by radiant heating by the panel heaters (3Y) and (4Y) and convection heating of hot air by the fan (5). Heat to a temperature of ° C.
A plurality of intermediate heating zones may be provided. Up to about 10 zones can be provided.

The reflow heating zone (8) is provided with an upper panel heater (3Z), a lower panel heater (4Z), and a fan (5), and has substantially the same configuration as the preheating zone (6).
In this reflow heating zone (8), while controlling the temperature based on a predetermined temperature profile determined in advance, printing is performed by radiant heating by the panel heaters (3Z) and (4Z) and convection heating of hot air by the fan (5). The substrate W is quickly heated to a high temperature required for soldering, and the solder mounted on the substrate is soldered by melting cream solder.
In this reflow heating zone, the printed circuit board W is heated to a temperature 5 to 10 ° C. higher than the melting point of the solder, such as 183 ° C. (lead solder), 210 to 220 ° C. (lead-free solder), and the solder is melted.

  In the cooling zone (9), a cold air blower (11) is disposed on the ceiling wall of the zone, and the printed circuit board W soldered in the reflow heating zone (8) is cooled.

In the reflow soldering apparatus configured as described above, the present invention is configured so that the width direction of the upper panel heaters (3X), (3Y), and (3Z) having a number of ejection holes (3h) is along the conveying direction. A plurality of divided areas having a plurality of ejection holes (3h), for example, as shown in FIG. 2, an upper panel heater (3Z consisting of three divided areas (3AZ), (3BZ) and (3CZ)) ), And the set temperature can be changed for each divided area. Furthermore, the width direction of the lower panel heaters (4X), (4Y), and (4Z) is divided along the transport direction, and the lower side is composed of a plurality of areas facing (3AZ), (3BZ), and (3CZ) A panel heater may be configured so that the set temperature can be changed for each divided area.
The temperature of each divided area of the panel heater is set and controlled by providing a temperature sensor near the surface center of each area.

In the present invention, the upper panel heaters (3X), (3Y), and (3Z) having a large number of ejection holes (3h) have an effect of being uniformly heated, and in addition to that, the lower panel By dividing the heaters (4X), (4Y) and (4Z), the effect is further increased.
The number of divisions is not particularly limited as long as it is 2 or more, but 2 to 4 is preferable from the viewpoint of ease of production and saturation of effects.
For example, when the upper panel heaters (3X), (3Y), and (3Z) are divided into three (3A), (3B), and (3C) areas, respectively, the outer areas (3AX), (3AY), and (3A) 3FP), and a printed circuit board W passing through (3CX), (3CY) and (3CZ) is mounted with a QFP (quad flat package) which is difficult to raise temperature due to its large heat capacity, and the inner area (3BX) ), (3BY) and the printed circuit board W that passes through (3BZ), when small components that are likely to rise in temperature are mounted, the set temperature of the outer areas (3A) and (3C) is increased to increase the inner area. The set temperature of (3B) is lowered.

  Further, the upper panel heaters (3X), (3Y) and (3Z) are divided into two sections (3A) and (3B), respectively, and the set temperatures of one of the sections (3AX), (3AY) and (3AZ) are set. Increase the temperature to transfer the printed circuit board W1 having a large heat load, and at the same time, lower the set temperature in the other areas (3BX), (3BY) and (3BZ) to convey the printed circuit board W2 having a small heat load. Can do.

  In the present invention, as described above, for example, the width direction of the upper panel heater (3Z) having a large number of ejection holes (3h) is divided along the conveying direction to have a large number of ejection holes (3h). Since the upper panel heater is composed of a plurality of sections (3AZ), (3BZ) and (3CZ), each panel heater has a large number of ejection holes. The effect of being heated uniformly is remarkably improved.

It is the schematic of the reflow soldering apparatus of this invention. It is the schematic which shows the panel heater which consists of a several area | region divided | segmented of this invention.

Explanation of symbols

1 Reflow soldering equipment (heating furnace)
2 Conveying means (conveying conveyor)
3X Upper panel heater (preheating zone)
3Y Upper panel heater (intermediate heating zone)
3Z Upper panel heater (reflow heating zone)
3h A large number of ejection holes 3AZ of the upper panel heater One of a plurality of areas of the upper panel heater (reflow heating zone)
3BZ One of the multiple areas of the upper panel heater (reflow heating zone)
3CZ One of multiple zones of upper panel heater (reflow heating zone)
4X Lower panel heater (preheating zone)
4Y Lower panel heater (intermediate heating zone)
4Z Lower panel heater (reflow heating zone)
5 Fan 6 Preheating zone 7 Intermediate heating zone 8 Reflow heating zone 9 Cooling zone 10 Hot air temperature sensor 11 Cold air machine

Claims (6)

  A board conveying means for mounting a component to be soldered, an upper panel heater and a lower panel heater for heating the board placed on the conveying means from above and below, and at least a plurality of ejection holes in the upper panel heater In the reflow soldering apparatus in which a fan is installed above the upper panel heater, the width direction of the upper panel heater is divided along the transport direction and consists of a plurality of areas having a number of ejection holes. A reflow soldering apparatus comprising an upper panel heater, wherein a set temperature can be changed for each of the divided areas.   Furthermore, the width direction of the lower panel heater is divided along the conveying direction to form a lower panel heater composed of a plurality of areas, and the set temperature can be changed for each of the divided areas. The reflow soldering apparatus according to claim 1.   The reflow soldering apparatus according to claim 1 or 2, wherein a number of ejection holes are provided in the lower panel heater, and a fan is installed below the lower panel heater.   A plurality of areas of the upper panel heater or a plurality of areas of the upper panel heater and the lower panel heater are divided into two or three areas, and at least one area is set at a higher temperature than the other areas. The reflow soldering apparatus according to any one of claims 1 to 3, wherein the reflow soldering apparatus is provided.   The upper panel heater and the lower panel heater are arranged three or more in the transport direction, and a preheating zone, an intermediate heating zone, and a reflow heating zone are configured. The reflow soldering apparatus according to the item.   A reflow soldering method using the reflow soldering apparatus according to any one of claims 1 to 5, wherein a plurality of areas of the upper panel heater or a plurality of upper panel heaters and lower panel heaters are used. A reflow soldering method, wherein a plurality of substrates having different thermal loads are simultaneously transported along each of the divided areas.

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