JPH04270062A - Heat conductive reflow soldering device - Google Patents

Abstract

PURPOSE:To optimumly execute conditioning in a reflow corresponding to the difference of a heat capacity in parts mounted on a substrate in a heat conductive reflow soldering device. CONSTITUTION:Heater block 11 for preheating, heater block 12 for reflow, heater block 21 for adjusting cooling speed of the substrate and block 13 for cooling the substrate are arranged. The heater block 12 for reflow is finely divided into three heater blocks 12a, 12b, 12c which are capable of controlling temps. While conveying the parts-mounted substrate P with an endless belt 16 disposed between pulleys 14, 15, the substrate P is heated with the heater blocks 11, 12 through the conveying belt 16. On the heater block 12 for reflow, solder paste applied between the substrate and the mounted parts, is melted. According to the heat capacity of mounted parts, to one or two of finely divided heater blocks 12a, 12b, 12c energizing is turned off or the setting temp. is individually set low.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer reflow soldering apparatus mainly suitable for heat transfer reflow soldering of workpieces having good thermal conductivity (eg, component-mounted aluminum substrates, ceramic substrates).

0003

2. Description of the Related Art As shown in FIG. 3, a conventional heat transfer reflow soldering device arranges three to five heater blocks 11 and 12 formed to have approximately the same dimensions, and Preheating and reflowing are performed. In the illustrated example, three heater blocks are used for preheating.
1, and a reflow heater block 12 is placed separately on the downstream side thereof. A workpiece cooling block 13 is arranged downstream of this reflow heater block 12. Furthermore, from the pulley 14 at one end to the pulley 15 at the other end,
The workpiece conveyance belt 16 is wrapped around the belt endlessly. Then, this workpiece conveying belt 16 is connected to each block 11,
By rotating through the upper surfaces of heater blocks 12 and 13, while conveying the workpiece P placed on this belt 16, the heat generated from each heater block 11 and 12 is transmitted to the workpiece P through the conveyor belt 16, The workpiece P is forcibly cooled by the workpiece cooling block 13 through the conveyor belt 16.

As shown in FIG. 4, the temperature profile of the workpiece (component mounting board) P is such that the workpiece P is preheated at a relatively low temperature of 180° C. or less on the plurality of preheating heater blocks 11. On the reflow heater block 12, the workpiece P is heated to a high temperature of 210° C. or higher to melt the solder paste applied to the workpiece P. The workpiece P that has passed through the reflow heater block 12 is cooled down to 150° C. or lower by a cooling plate that is air-cooled in the workpiece cooling block 13. As a result, the molten solder is solidified, and a solder joint portion is formed between the board and the mounted component to conductively connect them.

[0005]

[Problem to be solved by the invention] In this way, conventionally,
The heater block group is divided into one for preheating and one for reflow, and a part of the heater block group is used as the heater block 12 for reflow. Unable to obtain appropriate reflow time and temperature. For this reason, there have been problems such as damage to components mounted on the board due to higher temperatures than necessary, and reflow failures occurring at lower temperatures than necessary.

[0006] The present invention has been made in view of the above points, and it is an object of the present invention to optimize reflow conditions in a heat transfer reflow soldering apparatus in response to differences in heat capacity of components mounted on a board. The purpose is to

[Configuration of the invention]

[0008]

[Means for Solving the Problems] The present invention provides a method for moving the workpiece P from the reflow heater block 12 while transporting the workpiece P.
In a heat transfer reflow soldering device that performs reflow soldering using heat conducted to the reflow soldering device, the reflow heater block 12 is subdivided into a plurality of blocks whose temperature can be controlled individually.

[0009]

[Operation] The present invention provides a plurality of reflow heater blocks 12 according to differences in heat capacity of components mounted on a board.
The optimum reflow time and temperature can be obtained by selectively controlling the energization on/off and changing the set temperature individually.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. 1 and 2.

As shown in FIG. 1, a reflow heater block 12 is arranged downstream of a plurality of preheat heater blocks 11.
A heater block 21 for adjusting the workpiece cooling rate is arranged on the downstream side of the heater block 21 for adjusting the workpiece cooling rate.
A workpiece cooling block 13 is arranged downstream of the workpiece.

[0012] The temperature of the plurality of preheating heater blocks 11 can be individually controlled. The reflow heater block 12 has almost the same dimensions as one preheat heater block 11 as a whole, but the first heater block 12a and the second heater block 12 are individually temperature controllable.
It is subdivided into three blocks: b and third heater block 12c. The workpiece cooling rate adjusting heater block 21 is a temperature controllable heater block formed to have approximately the same dimensions as the preheating heater block 11. The workpiece cooling block 13 includes an air-cooled cooling plate on the workpiece transfer surface.

Further, a workpiece conveyance belt 16 is wound endlessly from the pulley 14 at one end to the pulley 15 at the other end. By continuously transporting the upper rotating part of this workpiece conveyance belt 16 via the upper surface of each block 11, 12, 21, 13, the workpiece (component mounting board) P placed on this belt 16 is continuously transported. While being conveyed, the heat generated from each heater block 11, 12, 21 is transmitted to the workpiece P through the conveyor belt 16, or the workpiece P is forcibly cooled through the conveyor belt 16 by the workpiece cooling block 13.

Next, the operation of the embodiment shown in FIG. 1 will be explained with reference to FIG.

By individually setting the temperature of a plurality of preheating heater blocks 11 for the continuously operated workpiece conveyor belt 16, the workpiece P can be heated through the conveyor belt 16.
Preheat to below 180°C under optimal heating conditions.

On the reflow heater block 12 which is subdivided into a plurality of parts, a first heater block 12a, a second heater block 12b and a third heater block 12c are divided according to the difference in heat capacity of the components mounted on the board. Optimum reflow time and temperature can be obtained by selectively controlling energization on/off or individually changing the set temperature.

For example, as shown by the solid line in FIG. 2, a large amount of heat is transferred from the first heater block 12a set at the highest temperature (260° C.) to the substrate of the work P through the conveyor belt 16, and the substrate is heated to 210° C. In order to maintain the substrate temperature as the reflow peak temperature, the first heater block 12a is heated to a lower temperature (2
The substrate is heated by the second heater block 12b and the third heater block 12c set at a temperature of 35°C. In this way, when the reflow peak temperature is suppressed to a low range, it is possible to minimize the thermal influence on the components mounted on the board.

Alternatively, as shown by the two-dot chain line in FIG. 2, the first, second and third heater blocks 12a, 1
2b, 12c are all set to a common temperature (254°C) and only the first heater block 12a is turned on, and the first and second heater blocks 12a
, 12b and the case where all of the first, second, and third heater blocks 12a, 12b, and 12c are energized may be selected depending on the heat capacity of the components mounted on the board.

In this way, the reflow heater block 12a is divided into three parts according to the heat capacity of the components mounted on the board.
, 12b, 12c, or by lowering the set temperature. Therefore, heat transfer reflow soldering can be performed continuously under optimal soldering conditions even on a board on which components having different heat capacities are mounted.

Next, with the solder paste applied between the board and the mounted components melted by this reflow heating, the workpiece is transferred to the workpiece cooling rate adjustment heater block 21. 21 to slow down the cooling rate of the workpiece. By adjusting the heating of the board with a small amount of heat so as to slow down the cooling rate of the metal board, which has good thermal conductivity, especially for mounted components with a large heat capacity, the temperature on this heater block 21 is gradually reduced at a rate that does not drop below 180 °C. cooled down. By controlling the temperature of the heater block 21, an arbitrary cooling rate can be obtained.

Therefore, at the initial stage when the molten solder between the board and the mounted component solidifies and a solder joint is formed, the rate of temperature drop on the board side of the solder joint and the rate of temperature drop on the component side are different. This prevents significant imbalance in the temperature distribution of the solder joint, suppressing the generation of internal stress in the solder joint, and ensuring a constant strength of the joint.

Heater block 21 for adjusting workpiece cooling speed
The workpiece P that has passed through the workpiece cooling block 13 is rapidly cooled down to 150° C. or lower by an air-cooled cooling plate.

[0023]

Effects of the Invention According to the present invention, the reflow heater block of the heat transfer reflow soldering device is subdivided into multiple blocks whose temperature can be individually controlled. Even boards loaded with components can be soldered continuously under optimal soldering conditions. Furthermore, by setting the individual temperatures of the subdivided reflow heater blocks, the reflow peak temperature can be suppressed to a low range, and the thermal influence on the mounted components can be minimized.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of a heat transfer reflow soldering apparatus of the present invention.

FIG. 2 is a graph showing a temperature profile of the heat transfer reflow soldering device same as above.

FIG. 3 is a plan view showing a conventional heat transfer reflow soldering apparatus.

FIG. 4 is a graph showing a temperature profile of the conventional heat transfer reflow soldering apparatus same as above.

[Explanation of symbols]

P Work

Claims (1)

[Claims] 1. In an apparatus that performs reflow soldering using heat conducted from a reflow heater block to a workpiece while transporting a workpiece, the reflow heater block is subdivided into a plurality of blocks whose temperature can be individually controlled. A heat transfer reflow soldering device characterized by: