JPS61289697A - Soldering - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a method of continuously heating a printed circuit board (hereinafter abbreviated as a board), etc., particularly for reflow soldering after mounting electronic components on a board. This relates to a heating method.

Conventional technology Conventionally, after applying solder material to a board and mounting electronic components, heating methods for continuous heating and reflow equipment include atmospheric heating, heating with hot air, infrared heating, and steam heating, which has recently begun to attract attention. There is heating using latent heat, etc. However, while atmospheric heating has advantages such as the ability to use N2 gas, it has the disadvantage that the temperature of the substrate, etc. that is the object to be heated is slow. Also, heating with hot air raises the temperature of the heated object faster than atmospheric heating.

If the wind speed is high, the parts may shift, and if the wind speed is slow, the temperature rises slowly.

Furthermore, although the infrared heating method can heat the object relatively efficiently, the speed of temperature increase varies depending on the difference in the infrared absorption rate of the object to be heated, which is a cause of temperature variations.

Furthermore, heating methods that utilize latent heat of vapor use liquids that boil at high temperatures, so there are problems in terms of heat shock to the objects to be heated, especially electronic components, and the working environment. Except for this, it has not become very popular.

Therefore, in recent years, as an improvement measure for these problems, a type that uses both infrared heating and hot air heating has been attracting attention. For example, as shown in Japanese Unexamined Patent Publication No. 60-6270, there is an example in which an infrared heater is used to preheat the object to be heated, and hot air is blown from above onto a part of the reflow process where the solder is melted. An example thereof is shown in FIG. In the figure, 1 is an infrared heater.

The object to be heated (not shown) is placed on the conveyor 2 from the position of arrow A, preheated by the infrared heater 1, and heated by hot air from the hot air generator 3 to melt the solder on the object. It's Nishide.

Another conventional example is Hiroshi Takakura "Cream solder removal flow furnace" Osaka Asa To Kagaku Co., Ltd. Technical data 84022
There are embodiments shown in 0P15 to Pe5e that use both hot air heating from above and partial infrared heater heating over the entire heating section along the tail. Its basic structure is shown in FIG. In the figure, reference numerals 4 and 6 are heaters for heating the atmosphere, and a fan 6 generates a downward wind to heat an object 8 on a conveyor 7, and infrared heaters 9 and 1o additionally heat the object.

Problems to be Solved by the Invention However, since the device shown in Fig. 6 heats only with hot air, it is difficult to solder objects with a large heat capacity.
There are cases where it is necessary to raise the temperature of the hot air to more than 400''C, which can lead to defects in parts with low heat resistance.

As shown in the figure, when the object to be heated 11 is large, the flow of hot air is not as shown by the arrow 12, and a retention point 13 of the flow is formed near the center of the object to be heated, and the heat transfer coefficient in that vicinity decreases. The temperature of the heated object tends to be lower than that of its surroundings. As a result, temperature variations within the same board become large, and the melting of the solder tends to be insufficient.

In view of the above problems, the present invention provides a stable heating reflow apparatus with little temperature variation.

Means for Solving the Problems In order to solve the above problems, the present invention preheats the substrate and then simultaneously heats it with an infrared heater and heats it by flowing hot air roughly parallel to the moving direction of the conveyor. The solder material is melted by melting the solder material.

Effects The present invention has the above-mentioned configuration, so that the temperature of the hot air can be kept at a relatively low temperature of around 250°C, the speed of the hot air can be kept at a speed that does not move the parts, and the direction of the hot air is generally horizontal, so that the temperature of the hot air can be kept at a relatively low temperature of around 250°C. Uniform heat transfer is now possible with no stagnation points, and infrared heaters require less energy per unit area, so heaters with a wide output wavelength range can be used and are less affected by the color tone of the heated object. There will be no need for it.

EXAMPLE Hereinafter, a soldering method according to an example of the present invention will be explained with reference to the drawings.

FIG. 1 is a front view showing the basic configuration of a soldering method according to a first embodiment of the present invention. In Figure 1, 1
4 is a preheating heater, and 16 is a conveyor. Furthermore, 16 is a fan for blowing hot air, 17 is a heater for heating the hot air, and 18 is an infrared heater for heating the substrate.

The operation of the soldering method configured as above will be explained.

In Fig. 1, the object to be heated is placed in the direction of the arrow from the position of arrow A, and heated to 120°C to 170°C using the preheating heater 14.
Heat to a range of °C. This temperature varies depending on the solder material used, but in the case of general pb-3n eutectic solder, it is generally around 150°C.

Next, the solder is melted by heating using a combination of hot air and infrared rays, which is a feature of this embodiment, and soldering is performed. In this process, the hot air heated by the heater 17 is transferred to the fan 1
6, the object to be heated 19 is sprayed and heated, and further heated with an infrared heater 18.

At this time, as shown in the figure, a suction port is provided in the subsequent process to circulate the air to keep the wind direction horizontal. As a result, as shown in FIG. 220, there is no stagnation point of hot air and uniform heating can be achieved.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a front view showing the basic structure of a soldering method according to a second embodiment of the present invention. In the figure, 21 is a preheating heater, and 22 is a conveyor. Furthermore, 23 is a fan for blowing hot air,
24 is a heater for heating hot air, and 26 is an infrared heater for heating the substrate. The above configuration is similar to the configuration shown in FIG.

The difference from the configuration shown in FIG. 1 is that a hot air blowing fan 27. The point is that a heater 28 for heating hot air is provided. By heating the object with hot air from above and below as described above, the hot air flows more stably in the horizontal direction, thereby stabilizing the temperature of the object to be heated.

Furthermore, as shown in FIG. 4, if the conveyor is a cenotype that supports both ends 29a and 29b of the object to be heated,
If heating is done only from above, the heat capacity of the stove is large, so the heat will be transferred toward the stove, resulting in lower temperatures at both ends.

Therefore, by heating from below, the portions 30a and 30b that were in the shadow of the object to be heated are also heated, thereby further reducing temperature variations.

In the first embodiment and the second embodiment, a propeller fan is shown as a blowing fan, but other types may be used as long as they can send hot air. Furthermore, although the infrared heating heater is shown as two rod-shaped heaters and a reflector, other infrared heaters may be used, and as long as the number and output are sufficient, it may be one, or three or more may be used. good.

FIG. 6 shows a typical temperature profile when the conveyor speed is 1 m/m. When heating only infrared rays on a double-sided steel foil test board, the board surface temperature was set at 236°.
The solder was not sufficiently melted unless the temperature was raised to 226°C, but the method of the present invention showed sufficient melting at 226°C.

Effects of the Invention As described above, the present invention enables heating by an infrared heater and heating by flowing hot air approximately parallel to the moving direction of the conveyor to be heated at the same time. Uniform heat soldering is now possible, which is less affected by the type of soldering.

[Brief explanation of the drawing]

Fig. 1 is a front view of the soldering method according to the first embodiment of the present invention, Fig. 2 is an explanatory diagram showing the flow of hot air in the soldering method, and Fig. 3 is a front view of the soldering method according to the first embodiment of the present invention. 4a is a front view of the main parts in the soldering method, FIG. 4 is a sectional view showing the state of the object to be heated, FIG. 6 is an explanatory diagram of the temperature profile, 6 and 7 are respectively front views of the conventional soldering method. FIG. 8 is an explanatory diagram showing the flow of hot air in the conventional hot air heating type soldering method. 14... Preheating heater, 15...
・Transport conveyor, 16... Fan for blowing hot air, 17... Heater for heating hot air, 18...
...Infrared heater for substrate heating. Name of agent: Patent attorney Toshio Nakao and 1 other person
2 Figure 4 urgently! ＞
Fly Pida tz, n-@屓し区” (singing) 1 Sott-18 Ua Ko>ra Figure 5 Figure 6 Figure 7 Figure 8

Claims (2)

[Claims] (1) In a device that heats and reflows printed circuit boards, etc. coated with solder material and mounted with electronic components etc. while being continuously conveyed by a conveyor, after preheating,
A soldering method characterized by heating by an infrared heater and simultaneously heating by flowing hot air approximately parallel to the moving direction of a conveyor. (2) The soldering method according to claim 1, characterized in that hot air is blown from both above and below the conveyor.