JPH04133392A - Reflow soldering circuit board - Google Patents

Abstract

PURPOSE:To prevent deviation, rise of an electronic component, or warpage, etc., of a reflow soldered circuit board by providing a heating element for aiding melting of solder on the board. CONSTITUTION:Conductors 12 of a predetermined pattern are formed on a printed circuit board or a thin film circuit board 10. Solders 14 are formed in the same pattern as that of the conductor 12, and attached on the conductors 12. The electrodes of electronic components 16, 18 are placed on the solders 14. Then, the board 10 is heated by both infrared ray heaters 24, 26 of a heating passage and a heating element 20, and the components 16, 18 are secured to the board 10 while melting the solders 14. In this case, since the element 20 is adhered to substantially entire surface of the board 10 as a solid layer, the temperature distribution of the board 10 can be made uniform to obtain desired quality of soldering.

Description

[Detailed Description of the Invention] [Summary] In order to prevent electronic components from shifting or standing up, or warping of the wiring board, a heating element that helps melt the solder is provided on the reflow solder row wiring board.

[Industrial application field]

The present invention relates to a reflow solder row wiring board.

[Conventional technology]

Reflow solder line wiring boards are used for surface-mount type semiconductor products, and are used to place electronic components on top of solder that has been adhered to the surface of the wiring board in a predetermined pattern, and to fix various electronic components while melting the solder. This is what I did. In order to melt the solder adhering to the surface of the wiring board, the wiring board is heated together with the electronic components using an infrared heater, hot air, or the like.

[Problems to be Solved by the Invention] Surface-mounted semiconductor products have many electronic components mounted at high density, and the number of solders increases in proportion to the number of electronic components. Furthermore, various electronic components having different sizes and shapes are mounted on one wiring board. The temperature of an infrared heater, hot air, or the like during reflow is neither too high nor too low, and is controlled to a temperature suitable for melting the solder. However, even if the temperature of the infrared heater, hot air, etc. is controlled, temperature unevenness occurs on the wiring board, and the quality of soldering may change depending on the position. For example, the temperature at the periphery of a wiring board is lower than that at the center, and even within a wiring board, the temperature tends to be lower near large electronic components, resulting in uneven temperature distribution and problems such as misalignment or standing up of electronic components. Problems may occur. In addition, the temperature of the wiring board itself is less likely to rise than the electronic components, and this can cause wicking, where the solder that should be bonded between the wiring board and the electronic components is sucked up toward the electronic components. There is a problem with the board warping.

SUMMARY OF THE INVENTION An object of the present invention is to provide a wiring board with reflow soldering that prevents electronic components from shifting or standing up, or warping of the wiring board.

[Means to solve the problem]

In the reflow soldered wiring board according to the present invention, solder is adhered in a predetermined pattern, electronic components are attached to the solder while melting the solder, and a heating element is provided to help melt the solder. This is a characteristic feature.

[For production]

In the above configuration, welding can be performed while melting the solder while supplying electricity to the heating element.

In addition, when using an external heat source, a heating element is attached to a location where the temperature is likely to be low depending on the position and type of electronic components to be attached to the wiring board, and the wiring board is heated by the external heat source and this heating element. and weld. This solves the problem when the temperature of the wiring board itself is more difficult to rise than the electronic components, and since welding can be performed with a uniform temperature distribution, the desired quality of soldering can be ensured.

[Example] FIGS. 1 and 2 show a first embodiment of the present invention, FIG. 1 shows a printed wiring board or thin film wiring board 10 after soldering, and FIG. 2 shows a printed wiring board or thin film wiring board 10 after soldering. It shows where you are. A predetermined pattern of conductors 12 is formed on the surface of the printed wiring board or thin film wiring board 10.

As shown in FIG. 2, solder 14 is formed in the same pattern as conductor 12 and is deposited over conductor 12. As shown in FIG. The solder 14 is made of cream solder, for example, and adheres to the wiring Fi, 10 by itself and is held in place. Electrode portions of electronic components 16 and 18 called chip components are placed on these solders 14. Furthermore, the heating element 20 is adhered to almost the entire surface of the back surface of the wiring board 10 as a solid layer. The heating element 20 is made of, for example, a thick ceramic resistive material, and generates heat when energized.

This wiring board 10 is heated in a heating furnace.

The heating furnace includes upper and lower infrared heaters 24 and 26, and a wiring board 10.
It consists of a transport heald 28 that can be grasped on both sides. The conveyor belt 28 is connected to a drive means (not shown), and can sequentially pass the wiring boards 10 between the infrared heaters 24, 26. Furthermore, electrodes 30 for heating the heating element 20 are incorporated in the conveyor belt 2, and these electrodes 3
0 is connected to a power source (not shown) to energize the heating element 20.

Therefore, in this embodiment, wiring board 10 is heated by both infrared heaters 24, 26 and heating element 20, melting solder 14 while fixing electronic components 1.6.18 to wiring board 10. In this case, since the heating element 20 is attached as a border layer to almost the entire surface of the wiring board 10,
The temperature distribution can be made uniform, and the desired quality of soldering can be ensured. In this way, the first
Soldering is completed as shown in the figure.

Note that if the heating element 20 can generate a sufficient amount of heat, soldering can be performed simply by energizing the heating element 20 without using the infrared heaters 24 and 26. Furthermore, since the heating element 20 is a resistor, the wiring board 10
Even if it remains, it will not interfere with the subsequent use of the wiring board 10. Further, this heating element 20 can also be used as a shield pattern, a ground pattern, etc.

FIG. 3 shows a second embodiment of the present invention, in which conductors 12 in a predetermined pattern are formed on the front and back surfaces of a wiring board 10, and solder 14 is adhered onto the conductors I2. Reference numeral 32 denotes a through hole that connects the conductor work 2 on the front and back surfaces of the wiring board 10. FIG. 3 shows the state before the electronic component is mounted, and the electric bridge portion of the electronic component can be attached to the solder 14 in the same manner as in the first embodiment. In this embodiment, the heating element 2o is inserted into the wiring board 10 and can heat the wiring board 10 from inside. In such a case, the heating element 20 can be formed of nichrome wire or the like.

FIG. 4 shows a third embodiment of the present invention, and schematically shows electronic components 34 arranged on the surface of a wiring board 10. In FIG. Each electronic component 34 is attached on the conductor 12 formed on the surface of the wiring board IO and the solder 14 attached thereon. Although each electronic component 34 is arranged so as to occupy a considerable portion of the surface of the wiring board 100, there is a part of the open space, and the heating element 2 is provided in that part. By providing the heating element 2 in the empty space in this way,
The quality of soldering during reflow can be improved without changing the design conditions of the wiring board 10. In this case, heat from an external heating means is placed near the heating element 20 on the wiring board 10.
It is effective when there are parts that prevent transmission. It is also effective when the part of the heating element 20 corresponds to the ear of the wiring Ifi, 10 and is removed at the end.

[Effects of the Invention] As explained above, in the reflow soldering wire plate according to the present invention, solder is attached in a predetermined pattern, electronic components are attached to the solder while melting the solder,
Since the configuration is provided with a heating element that helps melt the solder, welding can be performed while melting the solder while applying electricity to the heating element, improving the temperature conditions for solder welding and achieving the desired soldering. Quality can be ensured.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a reflow soldering wire board according to a first embodiment of the present invention, FIG. 2 is a sectional view showing a wiring board during heating, and FIG. 3 is a diagram showing a second embodiment of the present invention. , FIG. 4 is a diagram showing a third embodiment of the present invention. DESCRIPTION OF SYMBOLS 10... Wiring board, 12... Conductor, 14... Solder, 16.18... Component, 20... Heating element. A diagram showing a first embodiment of the present invention

Claims (1)

[Claims] A wiring board with reflow soldering, characterized in that solder is adhered in a predetermined pattern, electronic components are attached to the solder while melting the solder, and a heating element is provided to help melt the solder.