JPH0582952A - Soldering method of electronic component - Google Patents

Abstract

PURPOSE:To provide a method in which soldering treatment is enabled at a low temperature and the quantity of solder is reduced, which can also correspond to a fine circuit pattern and in which an electronic component can be soldered and fixed to a printed board with high accuracy. CONSTITUTION:An electronic component 1 is temporarily fixed previously to a printed board 2, the removal treatment of oxide films is executed at the contact positions of the external terminal of the electronic component 1 and the conductive pattern of the printed board 2, the contact positions are coated with polybutene 4 as a heating medium, dispersion solder 5, in which fine particle-shaped molten solder is dispersed into polybutene, is sprayed against the contact positions coated with polybutene 4, and the electronic component 1 is soldered and fixed to the printed board 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of soldering an electronic component which is applied to solder a surface mount type electronic component to a printed board.

[0002]

2. Description of the Related Art Conventionally, in order to mount a surface mount type electronic component on a printed circuit board, mainly wave soldering,
Reflow soldering is applied.

Among them, in wave soldering, an adhesive is applied to a component mounting surface of a printed circuit board by a dispenser,
After temporarily fixing and fixing the electronic component to the board surface of the printed circuit board with this adhesive, contact the mounting surface of the electronic component with the heat-fluidized solder wave to connect the external terminals of the electronic device and the conductive pattern of the printed circuit board. The contact points of are fixedly connected.

In reflow soldering, paste solder, which is a mixture of solder powder and flux, is applied to the component mounting surface of the printed circuit board by screen printing, and the paste solder is contacted to mount the electronic component on the plate surface of the printed circuit board. After that, the paste solder is melted in the reflow furnace to connect and fix the contact points between the external terminal of the electronic component and the conductive pattern of the printed board.

However, since the solder is fluidized and used in the wave soldering, a short circuit is likely to occur due to a solder bridge between adjacent patterns when the conductive pattern of the printed circuit board is formed with a fine circuit. The melting of the solder requires heating at about 250 to 270 [deg.] C., which limits the applicable electronic components from this melting temperature.
In addition, since the molten solder rises in an arc shape due to surface tension and is attached, not only the amount of the attached solder increases but it is difficult to control the film thickness. Further, since the molten solder is stored in the stirrer or the tank, it has a drawback that it is easily contaminated with time.

In reflow soldering, since paste solder is printed by screen printing, it is difficult to perform appropriate printing according to a fine circuit. Further, since it is difficult to make the temperature distribution in the reflow furnace uniform, the mounting deviation of the electronic component is likely to occur due to the difference in the surface tension of the remelted solder depending on the location. In order to melt the solder, a high-temperature heat treatment of about 210 to 240 ° C. is required, and not only the material cost of the paste solder increases due to the inclusion of the flux, but also the cost increases.
There are drawbacks such as contamination by flux tars.

[0007]

DISCLOSURE OF THE INVENTION The present invention is an excellent electronic component that can be soldered at a low temperature and requires a small amount of solder, and is free from contamination by flux tars and capable of handling fine circuit patterns. An object of the present invention is to provide a soldering method.

[0008]

In the method for soldering an electronic component according to the present invention, the electronic component is temporarily fixed and fixed to a printed circuit board in advance, and a contact point between an external terminal of the electronic component and a conductive pattern of the printed circuit board is provided. After the oxide film has been removed, the polybutene is applied as a heat medium to the contact point, and then the dispersion solder in which fine-grained molten solder is dispersed in the polybutene is blown to the contact point where the polybutene is applied. The electronic parts are attached to the printed circuit board by soldering.

[0009]

In this electronic component soldering method, polybutene which can prevent oxidation is applied as a heat medium after the oxide film is removed from the contact points between the external terminals of the electronic component and the conductive pattern of the printed circuit board, and the polybutene is applied. Dispersion solder in which fine-grained molten solder is dispersed in polybutene is sprayed onto the contact points, and this dispersion solder connects and fixes the external terminals of the electronic component and the conductive pattern of the printed circuit board, reducing the soldering temperature. It can be securely fixed with a small amount of solder, the cost associated with soldering can be reduced, there is no contamination due to flux tar, etc., and the molten solder of the dispersion solder is also fine-grained, and it is also applied to soldering to fine circuit patterns. be able to.

[0010]

The method of soldering an electronic component according to the present invention uses polybutene as a heating medium. This polybutene (also referred to as "polybutylene") is a polymer of 1-butene and 2butene (commercially available from Nippon Oil Co., Ltd.), and although the viscosity varies depending on the molecular weight, it is suitable for the present invention at room temperature. At about 10,000 cps and 190 to
It is preferable to have a viscosity of about 10 cps at a temperature of 200 ° C. The polybutene is preferable as a heat medium for transmitting the heat of the molten solder to the object to be coated because it has heat resistance and prevents oxidation of the object to be coated and can be stably used at a temperature of 190 ° C. or higher for a long time.

As the dispersion solder, finely divided molten solder having an average particle diameter of 10 μ is dispersed in liquid polybutene. This dispersion solder is obtained by adding a solder composition to liquid polybutene in a weight ratio of 50 Vol% or less based on polybutene. If the addition amount of the solder composition is large, it is difficult to atomize the solder. Therefore, in order to obtain a dispersion solder in which molten solder having an average particle diameter of 10 μm is dispersed in liquid polybutene, 5% by volume or less of the solder composition may be added. A suspension of this solder composition and liquid polybutene is 190 ° C. or higher, preferably 19 ° C. or higher in a nitrogen gas or argon gas atmosphere.
The solder is melted by heating it to 0 to 200 ° C., and stirred by a homogenizer to obtain a dispersion solder in which the molten solder is uniformly dispersed in liquid polybutene. An ultra-high speed homogenizer (for example, manufactured by Polytron) was used as the homogenizer, and
5000 to 30,000 times under the temperature condition of 0 to 200 ° C /
Stir for a minute. In order to obtain the one having an average particle size of 10 μ by this stirring, the treatment may be performed 10000 times / minute or more for about 1 to 5 minutes. When the molten solder is dispersed in the liquid polybutene, the molten solder is not immediately cooled due to the spraying described later, so that the molten solder can be attached in the molten state to the contact point between the electronic component and the printed board.

In order to solder an electronic component using the heat medium and the dispersion solder, first, the electronic component 1 is temporarily fixed to the printed board 2 with the adhesive 3 and the external terminals of the electronic component 1 and the print are printed. After the oxide film is removed from at least the contact points of the conductive pattern of the substrate 2 and then washed, liquid polybutene 4 is applied as a heat medium to the contact points where the oxide film has been removed to prevent reoxidation. The polybutene 4 may be spray-applied in a dot shape toward the plate surface of the printed circuit board 2 by using a dispenser D as shown in FIG. 1. The amount of pressure applied to the liquid surface and the pressure application time Since the coating amount can be controlled, it is possible to properly coat even a fine spot.

After applying this polybutene, dispersion solder is sprayed from an injection nozzle of a soldering device, which will be described later, to the electronic component 1 temporarily fixed to the printed board 2 as shown in FIG.

As the soldering device, as shown in FIG. 3, a homogenizer tank 10 for containing a solder / polybutene suspension is provided.
And a mechanism for ejecting the dispersion solder 5 produced in the homogenizer tank 10 can be used. The solder bath of the homogenizer tank 10 is hermetically sealed and placed in an inert atmosphere. However, even when placed in the atmosphere, the polybutene substantially shields the solder from the air, so that oxidation of the solder can be prevented. The homogenizer tank 10
The inside of the is maintained at a temperature that keeps the solder in a molten state by a heater (not shown). The homogenizer tank 10 is equipped with a homogenizer 11.
The dispersion solder 5 in which fine-grained molten solder is dispersed in polybutene is produced by stirring the suspension of solder and polybutene with the blade 12 of No. 1. Nitrogen gas is introduced into the homogenizer tank 10 from the nitrogen tank 13 to prevent the solder from being oxidized. Further, the dispersion solder 5 obtained in the homogenizer tank 10 can be introduced into the solder bath 17 by the heat resistant pump 14 via the pipe lines 15 and 16 and sprayed from the injection nozzle 18 onto the printed circuit board 2. Nitrogen gas is preferably introduced into the solder bath 17 from a nitrogen tank 24 to prevent the solder from oxidizing.
The remaining dispersion solder 5 is returned to the bottom of the homogenizer tank 10 via the return conduit 19. It is advisable to keep the temperature of the conduit through which the dispersion solder 5 flows in a warm or heated state,
Further, as the material of the tank, the bath, the pipeline, and the nozzle, it is preferable to use those lined with stainless steel. The amount of solder adhered on the printed board can be set to an appropriate amount by determining the concentration, flow rate and contact time of the dispersion solder. Further, the conduit 15 can be provided with a solder densitometer 20 that utilizes, for example, light transmission to monitor the concentration of dispersion solder. The concentration detection is converted into an electric signal to be compared with the limit concentration by the comparator 21, and when a solder shortage occurs, the control valve 23 of the solder tank 22 may be opened to replenish the solder.

Since the polybutene 4 is applied in advance to the sprayed spot of the dispersion solder 5, the oxidation of the spot is prevented, and the dispersion solder 5 containing the molten solder is surely secured by the mutual adhesive force of the polybutene. By adhering, the contact between the external terminal of the electronic component and the conductive pattern of the printed board can be soldered and fixed with high accuracy. This amount of adhesion can be freely set within the range of about 10 to 100 μm, and the solder deposit itself can be prevented from being oxidized because it is covered and protected with polybutene. By performing a cleaning process after this soldering, a series of soldering steps can be completed.

[0016]

As described above, according to the method for soldering an electronic component according to the present invention, (1) a soldering point which has been cleaned by removing an oxide film before spraying dispersion solder is used. Oxidation is prevented by applying polybutene, so that dispersion solder in which fine-grained molten solder is dispersed in polybutene can be reliably attached. (2) Since polybutene is used as the heat medium, the soldering temperature is 1
Soldering can be performed at a low temperature of about 90 to 200 ° C. (3) Since the solder is dispersed in the polybutene, it does not come into direct contact with the atmosphere or other atmospheres, so that it is possible to prevent oxidation and thus no solder defects occur. (4) The dispersion solder has an average particle diameter of several μ to several tens of μ, for example, about 10 μ, and since the solder / polybutene ratio is low, it can be attached in a state close to electroplating. The solder film thickness can be freely controlled within the range of about 10 to 100 μm, and it is possible to prevent a solder bridge between patterns even if the circuit pattern is minute. (5) Since it is not necessary to include flux in the dispersion solder, it is possible to prevent the electronic parts and the printed circuit board from being contaminated with tar.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a coating step of polybutene in a method according to the present invention.

FIG. 2 is an explanatory view showing a soldering step in the method according to the present invention.

FIG. 3 is an explanatory diagram showing an example of a soldering device that can be used in the method according to the present invention.

[Explanation of symbols]

 1 Electronic Component 2 Printed Circuit Board 4 Polybutene 5 Dispersion Solder

Claims (1)

[Claims] 1. An electronic component is temporarily fixed to a printed circuit board in advance, the oxide film is removed from the contact point between the external terminal of the electronic component and the conductive pattern of the printed circuit board, and then the heat medium is applied to the contact point. As polybutene is applied, then spraying a dispersion solder in which finely-divided molten solder is dispersed in polybutene to the contact points where the polybutene is applied, and electronic components are fixed by soldering to a printed circuit board. A method for soldering electronic parts, characterized by: