JPH0520509B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention is directed to Cu that has improved properties that electronic components should have, particularly gloss, contact resistance, solderability, etc.
-Relating to a method for producing Sn-based composite materials. [Prior art] Generally, when manufacturing electronic component materials, when Cu or Cu alloy material is plated with Sn or Sn alloy,
Reflow treatment is performed to prevent whisker generation, improve corrosion resistance, solderability, etc. This reflow process involves heating the material in the atmosphere using a heating method such as resistance heating or induction heating to melt the plating layer, or burning a combustion gas such as propane or butane in the atmosphere, and directly applying the flame. The plating layer is melted by applying it to the material. Furthermore, in order to perform heating efficiently, the heating section is sometimes surrounded by a refractory material or the like. [Problem to be solved by the invention] However, since Cu and Cu alloys have low electrical resistance, it is inherently inefficient to heat them by resistance heating or induction heating, and even if these methods are used, Because it comes into contact with oxygen in the atmosphere at high temperatures, the plated surface easily oxidizes, resulting in disadvantageous results for electronic parts, such as high contact resistance of plated products and reduced solderability. Furthermore, during reflow, the Sn or Sn alloy plated surface oxidizes.
The fluidity of molten Sn or Sn alloy deteriorates, which also causes poor surface gloss after solidification. This phenomenon becomes particularly noticeable when the plating thickness is 2 μm or more. In addition, when melting the plated metal by burning combustion gas such as propane or butane in the atmosphere and applying the flame directly to the material, the molten metal may be melted.
Defects caused by oxidation of Sn or Sn alloy when exposed to air are similar to those described above. Furthermore, even if the heated part is surrounded by refractories, etc., the oxygen concentration in the part directly exposed to the flame is very low, but the oxygen concentration in the part not exposed to the flame is high, and molten Sn or The Sn alloy plating layer is easily oxidized. Moreover, if the flame hits the entire material, the material will be heated too much and melt Sn or
There is a problem in that the diffusion layer formed by the reaction between the Sn alloy and the Cu or Cu alloy base material becomes thick, which adversely affects the surface gloss and solderability. The present invention has been made in view of the above circumstances, and provides a method for producing a Cu-Sn composite material by reflow treatment that has excellent properties as an electronic component, particularly surface gloss, solderability, electrical contact properties, etc. The purpose is to [Means for Solving the Problem] In order to achieve the above object, the present inventor has conducted intensive research on a method for preventing oxidation when obtaining a Cu-Sn composite material by reflow treatment.
This was made possible by heating and melting the plating layer using combustion gas controlled to a specific CO concentration. That is, the method for producing a reflow plated material according to the present invention is to prepare a Cu or Cu alloy material that has been plated with Sn or Sn alloy with a thickness of 0.3 to 10 μm by placing a mixed gas controlled at an air ratio of 1 or less in a separate chamber in advance. The method is characterized in that the combustion gas having a CO concentration of 1 to 7 vo% is introduced into a processing furnace, and a reflow treatment is performed within the processing furnace. In addition, at that time, in the processing furnace, the Cu
Alternatively, heat the Cu alloy material by blowing combustion gas at a wind speed of 1 m/sec or more in the direction of sheet passing, melt the plated layer while maintaining the inside of the processing furnace at 1 atm or more, and then rapidly cool it. This is a characteristic feature. [Operation] The operation of the present invention will be explained in detail below. First, Sn or Sn alloy is plated onto a Cu or Cu alloy strip or wire by electroplating or the like. The plating layer is determined by the use of the material.
Generally 10μm or less. If necessary, a layer of Cu or Ni may be provided as an intermediate plating layer. The CO concentration of the combustion gas blown onto this material is 1
The reason for setting it to ~7 vo% is that if the CO concentration is less than 1 vo%, the Sn or Sn alloy plated surface will be easily oxidized during reflow. When the Sn or Sn alloy plated surface is oxidized in this way, the molten Sn
Alternatively, the fluidity of the Sn alloy deteriorates, resulting in poor surface gloss after solidification. during reflow
To prevent oxidation of the Sn or Sn alloy plated surface, a CO concentration of 7 vo% or less is sufficient, and
Since a high CO concentration increases the risk of air pollution, the CO concentration should be between 1 and 7 vo%. To control CO concentration in this way,
A mixed gas whose air ratio is controlled to be less than 1 is combusted in a separate chamber in advance. Next, this combustion gas is introduced into a processing furnace and the material is heated to perform reflow processing. A desirable aspect of the reflow process is as shown below. FIG. 1 is a diagram showing an example of a reflow processing state. A processing furnace 1 is equipped with a large number of gas outlets 2, and a processing material 3 is passed between these gas outlets 2 to perform plating. The structure is such that after the layers are melted, they are cooled by a cooling layer 5. In this case, the CO concentration of the combustion gas is controlled in a separate chamber equipped with a burner 4, and the combustion gas is circulated by a circulation fan 6, as shown in FIG. 1b. Further, as shown in FIGS. 2 and 3, the gas outlet 2 has a structure that concentrates hot air to wave the processing material 3, and as shown in FIG.
are arranged so as to uniformly heat the plate in the width direction. The reason why the processing material is carried out in a reflow processing furnace is to prevent heat from escaping and to fill the furnace with combustion gas at a pressure of 1 atmosphere or more so that the plating layer does not come into contact with air in a molten state. The reason for maintaining 1 atmosphere is to prevent air from entering the furnace and to enhance the oxidation prevention effect of the plating layer. Furthermore, the wind speed is measured from a direction of 45 degrees to 135 degrees (see Figure 1) with respect to the direction in which the plated materials are passed through the processing furnace.
By spraying at a speed of 1 m/sec or more, the oxidation prevention effect of the plating layer is enhanced and it is possible to heat the plate almost uniformly in the width direction. After melting the plating layer in the processing furnace, it is desirable to rapidly cool the melted plating layer. The reason for this is that when Sn is in a molten state, the diffusion layer formed by the reaction between molten Sn or Sn alloy and Cu or Cu alloy base material components becomes thicker over time, which has a negative effect on surface gloss and solderability. It is. [Example] Next, an example of the present invention will be specifically described. In this example, a brass strip (C2600) and a phosphor bronze strip (C5210) with a thickness of 0.20 mm and a width of 300 mm were subjected to conventional degreasing and pickling, and then Sn or Sn--Pb alloy plating was applied thereto. This plating is done in a copper sulfate bath (copper sulfate 200g/,
After applying copper plating to a thickness of 0.5 μm using sulfuric acid (100g/), tin sulfate bath (stannic sulfate 55g/), sulfuric acid
100g/, additive 10g/) or a borofusating bath (stannic borofluoride 130g/, lead borofusate)
50g/, boric acid 125g/, boric acid 25g/,
Sn or Sn--Pb alloy plating was applied to a predetermined thickness (listed in Table 1) using peptone (5 g/). On the other hand, butane gas and air are mixed at a predetermined mixing ratio and the resulting gas is combusted in a combustion chamber.
5 m) and uniformly applied hot air to the strip at a predetermined wind speed to melt the Sn plating or Sn-Pb plating layer. At that time, the temperature of the combustion gas and
CO concentration was measured. For comparison, Sn or Sn-Pb alloy plated strips prepared in the same manner were introduced into a furnace burning butane gas, and the flame was
It was applied directly to the alloy plated strip to melt the Sn or Sn-Pb alloy plated layer. The strip with the Sn or Sn-Pb alloy plated layer melted in this way is immediately immersed in water (70°C).
After solidifying the molten Sn or molten Sn-Pb alloy,
Dry. Table 2 shows the results of measuring the specular gloss, contact resistance, and solderability of the Sn or Sn-Pb alloy plated strips obtained. The specular gloss was measured according to JIS Z 8741 method 3 (incidence angle 60 degrees), and the contact resistance was measured according to JIS C.
Measured in accordance with 5402, 5.4. Furthermore, solderability was evaluated in accordance with JIS C 0050, 4.6 (method: 1.235°C soldering bath method) using 25% rosin methanol as a flux and measuring the wetting time _t2 . As is clear from Table 2, the inventive examples yielded Cu-Sn composite materials with superior surface gloss, solderability, and electrical contact properties compared to the comparative examples.

【table】

【table】

[Table] (Note) The measurement points correspond to the symbols in Figure 5.
[Effects of the Invention] As explained above, according to the present invention, a Cu-Sn composite material having excellent surface properties can be obtained, and therefore a material particularly useful as an electronic component can be provided.

[Brief explanation of the drawing]

Figures 1a and b are explanatory diagrams showing the processing furnace and the reflow processing state, Figures 2 to 4 are explanatory diagrams showing the structure and arrangement example of the gas outlet, and Figure 5 is the material obtained in the example. It is a figure explaining the characteristic measurement point of. 1... Processing furnace, 2... Gas spout, 3... Processing material, 4... Burner, 5... Cooling tank, 6... Circulation fan.

Claims (1)

[Claims] 1. For a Cu or Cu alloy material plated with Sn or Sn alloy with a thickness of 0.3 to 10 μm, a mixed gas controlled to have an air ratio of 1 or less is combusted in a separate chamber in advance so that the CO concentration is 1. ~7vo% combustion gas is introduced into the processing furnace,
A method for producing a reflow-plated material, characterized by performing reflow treatment in this processing furnace. 2. Heat the Cu or Cu alloy material in the processing furnace by blowing combustion gas at a wind speed of 1 m/sec or more in the sheet-threading direction, and heat the plated layer while maintaining the inside of the processing furnace at 1 atmosphere or more. The method according to claim 1, characterized in that after melting, the method is rapidly cooled.