JP2020172676A - Manufacturing method of solder product - Google Patents

Abstract

To provide a manufacturing method of a solder product suitable for more delicate soldering.SOLUTION: A solder product having a shape such as an ingot or the like is manufactured by undergoing the steps of: preparing a solder raw material containing tin as a main component and a metal element other than lead as an auxiliary component (step 10); melting the prepared solder raw material with heat to form a molten metal (step 20); filtering the obtained molten metal with a filter of which aperture is set to 10 μm or smaller (step 30); and cooling the filtered molten metal to solidify by cooling (step 40).SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing a solder product.

In Patent Document 1, each raw material composed of Sn, Ag, Cu, Ni, and Sn—P alloy is melted and adjusted in an electric furnace, and silver (Ag) is 1.0 to 4.0% by weight and copper (Ag). It contains 2.0% by weight or less of Cu), 0.5% by weight or less of nickel (Ni), 0.2% by weight or less of phosphorus (P), and the balance consists of tin (Sn) and unavoidable impurities. It is described to manufacture lead-free) solder alloys.

Japanese Patent No. 3296289

Conventionally, the solder obtained by soldering may have an appearance defect such as protrusions and bumps. In addition, a phenomenon called "solder bridge" may occur in which the solder attached to a specific part and the other solder attached to another part are integrated. In this case, the integrated solder A short circuit will occur between them.
An object of the present invention is to provide a method for manufacturing a solder product, which is suitable for finer soldering.

The method for producing a solder product of the present invention comprises a heating step in which a raw material containing tin as a main component and a metal element other than lead as a sub-component is melted by heating to form a molten metal, and the molten metal has an opening of 10 μm or less. It includes a filtration step of filtering with a filter set in 1 and a cooling step of solidifying the filtered molten metal by cooling.
In such a method for manufacturing a solder product, the filter can be heated in the filtration step.
Further, in the filtration step, a stainless steel wire mesh can be used as the filter.
Further, in the heating step, the raw material can be characterized by containing copper as the metal element as the sub-component.
From another point of view, the method for producing a solder product of the present invention includes a heating process in which a raw material containing tin as a main component and a metal element other than lead as a sub component is melted by heating to form a molten metal. A take-out step of taking out a solid substance having a diameter of more than 10 μm and existing in the molten metal from the molten metal set at 230 ° C. to 260 ° C. and a solidification of the molten metal from which the solid substance was taken out by cooling. Includes a cooling step to allow.
In such a method for manufacturing a solder product, the taking-out step can be characterized in that the molten metal is set at 235 ° C to 250 ° C.
Further, the taking-out step can be characterized in that the solid matter having a size of more than 5 μm is taken out from the molten metal.

According to the present invention, it is possible to provide a method for manufacturing a solder product, which is suitable for finer soldering.

It is a flowchart which shows the manufacturing procedure of the solder product of this embodiment. (A) to (c) are diagrams for explaining the outline of the filtration process. (A) to (c) are diagrams for explaining the structure of the evaluation substrate used for the evaluation of the solder bridge. It is a figure which shows the relationship between the temperature and the viscosity in the solder melt obtained by melting the solder products of Example 1 and Comparative Example 3. (A) is a diagram showing the oxygen concentration distribution in the depth direction in the solder obtained by soldering the solder products of Example 1 and Comparative Example 3, and (b) shows the average oxygen concentration in each solder. It is a figure. 3 is an optical photograph of the residue remaining on the filter after the filtration step in the production of the solder product of Example 1. 6 is an SEM photograph of the residue shown in FIG. 6 is an SEM photograph of a needle-shaped body present in the residue shown in FIG. 7.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The size, thickness, and the like of each part in the drawings referred to in the following description may differ from the actual dimensions.
[Definition of terms]
First, definitions of some terms used in the present embodiment will be described.

(Lead-free solder)
The "lead-free solder" in the present embodiment means a mixture of a plurality of metal elements containing tin (Sn) as a main component and a metal element other than lead (Pb) as a sub-component.
Here, the metal element as a sub-component may be any metal element other than lead, and examples thereof include copper (Cu), silver (Ag), bismuth (Bi), zinc (Zn) and the like. Can be done. Among these, it is desirable to use copper, which can be obtained at low cost.
Further, the metal element as a sub-component may contain not only one type but also two or more types (for example, silver and copper).
Although the "lead-free solder" of the present embodiment is referred to as "lead-free", it may actually contain lead as an unavoidable impurity.

(Solder products)
The "solder product" in the present embodiment means a product used in soldering in which a target metal material is joined by the above-mentioned "lead-free solder".
Here, examples of the "solder product" include a plate-shaped product (ingot), a linear product (wire), a spherical product (ball), and the like.

(Solder raw material)
The "solder raw material" in the present embodiment means a material used as a raw material in manufacturing the above-mentioned "solder product".
Here, examples of the "solder raw material" include elemental metal elements constituting the above-mentioned main component and sub-component, alloys thereof, and the like. Further, in the present embodiment, as the "solder raw material", solder scraps generated as a result of soldering using the above-mentioned "solder product" may be used. These "solder raw materials" (particularly solder scraps) may contain oxides of various metals and various impurities.

(Solder)
The "solder" in the present embodiment means that the above-mentioned "solder product" is transferred and adhered to the metal material side to be joined as a result of joining by soldering.

(Relationship between "lead-free solder", "solder products", "solder raw materials" and "solder")
Therefore, in the present embodiment, a "solder raw material" is used to manufacture a "solder product" composed of "lead-free solder", and further, this "solder product" is used to solder to a target metal material. By attaching, "solder" will be transferred and adhered to the metal material.

(Melted hot water)
The "molten metal" in the present embodiment means a "solder raw material" which is a raw material of a "solder product" and is melted by heating.

(Solder melt)
The "solder melt" in the present embodiment refers to a product obtained by melting a "solder product" which is a raw material of "solder" by heating.

[Manufacturing method of solder products]
Next, a method for manufacturing a solder product according to the present embodiment will be described.
FIG. 1 is a flowchart showing a manufacturing procedure of the solder product of the present embodiment.

Here, first, a preparatory step for preparing a solder raw material, which is a raw material for a solder product, is executed (step 10).
In step 10, a solder raw material containing tin as a main component and containing a metal element other than lead is prepared. At this time, it is desirable that the composition ratio of each metal element is basically the same as the composition ratio of the target solder product. The solder raw material prepared in step 10 may actually contain lead as an unavoidable impurity.

Next, a heating step of heating the solder raw material prepared in step 10 and melting the solder raw material to form a molten metal is executed (step 20).
In step 20, if the above-mentioned solder raw material melts, the temperature may be appropriately set, but in the case of producing a solder product made of so-called lead-free solder, the temperature is set to about 300 ° C to 400 ° C. Is desirable.

Subsequently, a filtration step of filtering the molten metal obtained in step 20 with a filter (details will be described later) is executed (step 30). In the following description, the molten metal obtained by executing step 20 may be referred to as "melted metal before filtration", and the molten metal obtained by executing step 30 may be referred to as "melted metal after filtration". It may be called. The details of step 30 will be described later.

Then, the cooling step of cooling the molten metal after filtration obtained in step 30 and solidifying the molten metal after filtration to obtain a solder product is executed (step 40).
In step 40, it is possible to appropriately select a cooling method according to the shape (ingot, wire, ball, etc.) of the solder product to be obtained. For example, when it is desired to obtain an ingot-shaped solder product, the above-mentioned molten metal after filtration may be poured into a mold made of iron oxide or the like and hardened.

[Details of filtration process]
FIG. 2 is a diagram for explaining an outline of the filtration step of step 30.
Here, FIG. 2A is a diagram for explaining an outline of the filtration device 10 used in the filtration step. Further, FIG. 2B is a diagram for explaining a configuration example of the filter 12 (details will be described later) provided in the filtration device 10. Further, FIG. 2C is a diagram for explaining another configuration example of the filter 12.

(Configuration of filtration device)
The filtration device 10 discharges the molten metal 1 after filtration by supplying the molten metal 1 before filtration and accommodating the molten metal 1 before filtration, and filtering the molten metal 1 attached to the container 11 and before filtration. A filter 12 for heating the filter 12 and a heater 13 for heating the filter 12 are provided. Here, in the example shown in FIG. 2A, it is assumed that the temperature of the molten metal 1 before filtration is the temperature T1 before filtration, and the temperature of the molten metal 2 after filtration is the temperature T2 after filtration.

〔container〕
The container 11 has, for example, a tubular shape (cylindrical shape), and the two openings provided in the container 11 are arranged so as to face in the vertical direction (vertical direction). The container 11 may be made of any material, but from the viewpoint of suppressing mixing of oxides and the like into the molten metal 1 before filtration, it is desirable to use a metal material rather than a ceramic material. Further, among various metal materials, it is desirable to use a stainless steel material, particularly SUS316L, from the viewpoint of reducing the penetration into the molten metal 1 before filtration.

〔filter〕
The filter 12 has, for example, a plate shape (disk shape), and is attached so as to close the bottom of the container 11 described above. The opening s of the filter 12 of the present embodiment is set to 10 μm or less, more preferably 5 μm or less, and further preferably 3 μm or less. The filter 12 may also be made of any material (for example, an inorganic material, a metal material, an organic material), but from the viewpoint of suppressing mixing of oxides and the like into the molten metal 1 before filtration, it is more than a ceramic material. It is also desirable to use a metallic material. Further, among various metal materials, it is desirable to use a stainless steel material, particularly SUS316L, from the viewpoint of reducing the penetration into the molten metal 1 before filtration. Further, when the filter 12 made of a metal material is adopted, if it is possible to obtain the above-mentioned opening s, either a wire mesh made by knitting a metal wire or a punching metal made by punching a metal plate is adopted. It doesn't matter. However, as the filter 12, it is desirable to use a wire mesh that can easily obtain a smaller opening s. When a wire mesh is used as the filter 12, it is desirable to use a wire mesh that has been subjected to a sintering process from the viewpoint of suppressing the deviation of the opening s. Examples of the organic material that can be used as the filter 12 include various aramid resins and carbon fibers (carbon fibers).

When a wire mesh is used as the filter 12, various methods such as plain weave, twill weave, plain weave and twill weave may be adopted as the knitting method. Here, FIG. 2B illustrates a filter 12 using a plain weave, and FIG. 2C illustrates a filter 12 using a twill weave. As shown in these, when the diameter (width) of the metal wire (wire) used in each is the wire width w, the gap between the two adjacent wires is the opening s. In the examples shown in FIGS. 2B and 2C, the opening s is larger than the wire width w, but the present invention is not limited to this, and the opening s and the wire width w are equal to each other. In some cases, the opening s may be smaller than the wire width w.

〔heater〕
The heater 13 heats the filter 12 by using a heating source other than the molten metal 1 before filtration. Therefore, the heater 13 may directly heat the filter 12 by energization or the like, or indirectly heat the filter 12 by heat conduction through the container 11 or another member (not shown). May be good.

[Relationship between pre-filtration temperature and post-filtration temperature]
Here, the relationship between the pre-filtration temperature T1 of the pre-filtration molten metal 1 and the post-filtration temperature T2 of the post-filtration molten metal 2 will be described.
As described above, in the heating step of step 20, the solder raw material is heated to about 300 ° C. to 400 ° C. to melt it. However, the pre-filtration temperature T1 of the pre-filtration molten metal 1 is 230 ° C. to 260 ° C., more preferably about 235 ° C. to 250 ° C., and the maximum temperature is slightly lower than that at the time of melting.
On the other hand, it is desirable that the temperature T2 after filtration of the molten metal 2 after filtration is about 230 ° C. to 260 ° C. Here, if the temperature T2 after filtration is too low, the molten metal 2 after filtration begins to solidify during the execution of the filtration step or immediately after the execution of the filtration step, and the production efficiency of the solder product is significantly lowered.

(Operation of filtration device)
Then, the operation of the filtration device 10 in the filtration step of step 30 will be described more specifically.
First, in the heating step of step 20, the temperature of the unfiltered molten metal 1 obtained by heating the solder raw material to 300 ° C. to 400 ° C. is adjusted so as to be the pre-filtration temperature T1 (230 ° C. to 260 ° C.). .. Further, the filter 12 is heated in advance by using the heater 13.

Next, the pre-filtration molten metal 1 whose temperature has been adjusted to the pre-filtration temperature T1 is put into the container 11 to which the filter 12 is attached from above. Then, most of the unfiltered molten metal 1 put into the container 11 passes through the filter 12 and falls downward due to the action of gravity, and becomes the filtered molten metal 2. At this time, pressure may be applied to the unfiltered molten metal 1 existing in the container 11 and on the filter 12, if necessary. When pressure is applied, a gas such as nitrogen (before filtration) that does not easily oxidize the molten metal 1 before filtration and can apply pressure isotropically to the molten metal 1 before filtration (before filtration). It is desirable to use a gas that is inert to the molten metal 1.

Further, the filter 12 is heated by the heater 13 while filtering the molten metal 1 before filtration, and suppresses solidification of the molten metal in the filter 12. The heater 13 merely functions to assist the molten metal in passing through the filter 12, and the pre-filtration temperature T1 of the molten metal 1 before filtration in the container 11 is set to the set temperature (230). It is desirable not to perform excessive heating that exceeds (° C. to 260 ° C.).

Then, the molten metal 2 after filtration obtained by passing through the filter 12 is made into a solder product by the cooling step described above. On the other hand, the residue (not shown) that could not pass through the filter 12 remains on the filter 12. Then, when the heating by the heater 13 is completed after the filtration step is executed, the filter 12 to which the residue is attached is removed from the container 11 and discarded. After that, a new filter 12 is attached to the container 11.

Hereinafter, the present invention will be described in more detail based on Examples. However, the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.
The present inventor manufactured a plurality of types of solder products under manufacturing conditions in which the presence or absence of the filtration step and the opening s of the filter 12 used in the filtration step were different, and evaluated the performance of each obtained solder product.

[Explanation of each example and each comparative example]
Here, Table 1 shows the setting conditions of the filtration step in step 30 in the production of the solder products of Examples 1 to 3 and Comparative Examples 1 to 3.

Here, in each of Examples 1 to 3 and Comparative Examples 1 to 3, copper was used as a solder raw material at 0.7 wt. A solder product generally called "Sn0.7Cu" was manufactured using a mixture of a lump of tin and a lump of copper, which was made of% and the balance was tin. Therefore, in each of Examples 1 to 3 and Comparative Examples 1 to 3, the solder raw material did not contain solder debris such as dross.

(Example 1)
In the first embodiment, the solder product was manufactured by executing the filtration step by the filter 12 (filter: yes). More specifically, in Example 1, the unfiltered molten metal 1 obtained by heating the solder raw material is filtered by a filter 12 having an opening s of 3 μm, and the obtained post-filtered molten metal 2 is used. By cooling, a solder product was obtained.

(Example 2)
In Example 2, the solder product was manufactured by executing the filtration step by the filter 12 (filter: yes). More specifically, in Example 2, the molten metal 1 before filtration obtained by heating the solder raw material is filtered by a filter 12 having a mesh opening s of 5 μm, and the obtained molten metal 2 after filtration is used. By cooling, a solder product was obtained.

(Example 3)
In Example 3, the solder product was manufactured by executing the filtration step by the filter 12 (filter: yes). More specifically, in Example 3, the pre-filtration molten metal 1 obtained by heating the solder raw material is filtered by the filter 12 having the opening s set to 10 μm, and the obtained post-filtration molten metal 2 is obtained. By cooling, a solder product was obtained.

(Comparative Example 1)
In Comparative Example 1, a solder product was manufactured by executing the filtration step by the filter 12 (filter: yes). More specifically, in Comparative Example 1, the unfiltered molten metal 1 obtained by heating the solder raw material was filtered by a filter 12 having an opening s of 20 μm, and the obtained post-filtered molten metal 2 was obtained. By cooling, a solder product was obtained.

(Comparative Example 2)
In Comparative Example 2, a solder product was manufactured by executing the filtration step by the filter 12 (filter: yes). More specifically, in Comparative Example 2, the molten metal 1 before filtration obtained by heating the solder raw material was filtered by a filter 12 having an opening s of 100 μm, and the obtained molten metal 2 after filtration was filtered. By cooling, a solder product was obtained.

(Comparative Example 3)
In Comparative Example 3, the solder product was manufactured without executing the filtration step by the filter 12 (filter: none). More specifically, in Comparative Example 3, a solder product was obtained by cooling the molten metal 1 before filtration as it was.

[Evaluation of solder products]
Here, as a scale for evaluating the solder products of each example and each comparative example, the state of occurrence of bridges (solder bridges) in the solder obtained by using various solder products for soldering and melting of various solder products. The viscosity of the solder melt obtained in this process and the oxygen concentration in the solder obtained by using various solder products for soldering were used.

(Solder bridge)
First, the evaluation of the solder bridge will be described. Here, the solder bridges were evaluated for all the solder products of Examples 1 to 3 and Comparative Examples 1 to 3.

[Evaluation board]
FIG. 3 is a diagram for explaining the configuration of the evaluation substrate 100 used for evaluating the solder bridge. Here, FIG. 3A is a top view of the evaluation substrate 100 as viewed from the formation surface side of the first pattern group 101 to the third pattern group 103 (details will be described later). Further, FIG. 3B is a diagram for explaining the configuration of the first electrode group A to the fifth electrode group E (details will be described later) constituting the first pattern group 101. Further, FIG. 3C shows the electrode width F and the electrode height I of the simulated electrode 110 (details will be described later) in each of the first electrode group A to the fifth electrode group E, and two adjacent simulated electrodes. It is a figure for demonstrating the gap G and pitch H between 110.

The evaluation substrate 100 is composed of a rectangular glass epoxy (FR-4) plate (glass epoxy plate: thickness about 1.5 mm) and a plurality of simulated electrodes (thickness 18 μm) each composed of a copper layer. It has a pattern group formed on one surface of the glass epoxy plate. Then, the evaluation substrate 100 is obtained by removing a part of the copper foil in the substrate material having the glass epoxy plate and the copper foil by an etching treatment. In the following description, in the evaluation substrate 100 shown in FIG. 3A, the lateral direction (vertical direction in the figure) is referred to as "vertical direction", and the longitudinal direction (horizontal direction in the figure) is referred to as "horizontal". Called "direction".

On the evaluation substrate 100, as the pattern group, the first pattern group 101 arranged in the upper row in the vertical direction along the horizontal direction and the second pattern group 102 arranged in the middle row in the vertical direction along the horizontal direction. And a third pattern group 103 arranged side by side in the horizontal direction are formed in the lower row in the vertical direction. Since the first pattern group 101 to the third pattern group 103 have a common configuration, the first pattern group 101 will be described below as an example.

The first pattern group 101 includes a first electrode group A arranged on the leftmost side of the evaluation substrate 100, a second electrode group B arranged adjacent to the right side of the first electrode group A, and a second electrode group B. The third electrode group C arranged adjacent to the right side of the electrode group B, the fourth electrode group D arranged adjacent to the right side of the third electrode group C, and adjacent to the right side of the fourth electrode group D. Moreover, it has a fifth electrode group E arranged on the rightmost side in the figure of the evaluation substrate 100. Further, the first electrode group A, the second electrode group B, the third electrode group C, the fourth electrode group D, and the fifth electrode group E each have a rectangular simulated electrode 110 extending in the vertical direction. It is configured by arranging 31 pieces in the direction.

Here, in the first electrode group A, the electrode width F is set to 0.2 mm, the gap G is set to 0.5 mm, the pitch H is set to 0.7 mm, and the electrode height I is set to 15 mm. Further, in the second electrode group B, the electrode width F is set to 0.2 mm, the gap G is set to 0.4 mm, the pitch H is set to 0.6 mm, and the electrode height I is set to 15 mm. Further, in the third electrode group C, the electrode width F is set to 0.2 mm, the gap G is set to 0.3 mm, the pitch H is set to 0.5 mm, and the electrode height I is set to 15 mm. Furthermore, in the fourth electrode group D, the electrode width F is set to 0.2 mm, the gap G is set to 0.2 mm, the pitch H is set to 0.4 mm, and the electrode height I is set to 15 mm. In the fifth electrode group E, the electrode width F is set to 0.15 mm, the gap G is set to 0.15 mm, the pitch H is set to 0.3 mm, and the electrode height I is set to 15 mm.

As a result, the dimensions of the first electrode group A are 21 mm in width × 15 mm in length. The dimensions of the second electrode group B are 18 mm in width × 15 mm in length. Further, the dimensions of the third electrode group C are 15 mm in width × 15 mm in length. Furthermore, the dimensions of the fourth electrode group D are 12 mm in width × 15 mm in length. The dimensions of the fifth electrode group E are 9 mm in width × 15 mm in length.

Here, two types of the evaluation substrate 100 described above, one with a predetermined surface treatment and one without a predetermined surface treatment, were prepared. In the following description, the evaluation substrate 100 not subjected to the surface treatment is referred to as an "untreated substrate", and the evaluation substrate 100 subjected to the surface treatment is referred to as a "treated substrate". Here, the "untreated substrate" refers to a glass epoxy board in which a pattern group is formed by etching, and which is only washed with water. Further, the "treated substrate" refers to a glass epoxy board having a pattern group formed by etching, which has been washed with water to remove oxides present on the surface.

〔Test method〕
Next, a method for testing a solder bridge using the evaluation substrate 100 described above will be described. Here, the evaluation board 100 is soldered under the condition of imitating the so-called flow method of soldering.

First, a target solder product (here, any of the solder products of Examples 1 to 3 and Comparative Examples 1 to 3) is put into a solder bath (not shown) composed of SUS316L and heated. To obtain a solder melt obtained by melting a solder product. Next, the temperature of the solder melt in the solder bath was adjusted to 250 ° C. Subsequently, with respect to the solder melt in the solder bath, the evaluation substrate 100 (unprocessed substrate or treated) is in a state where the first pattern group 101 is on the upper side and the third pattern group 103 is on the lower side from above the solder tank. The finished substrate) was moved vertically downward, and the evaluation substrate 100 was immersed in the solder melt. The moving speed of the evaluation substrate 100 at this time was 60 mm / s. Then, with the entire evaluation substrate 100 immersed in the solder melt, the movement of the evaluation substrate 100 was stopped, and the evaluation substrate 100 was held (immersed) for only 3 seconds. After that, the evaluation substrate 100 immersed in the solder melt was taken out from the solder melt by moving the evaluation substrate 100 vertically upward in the solder bath. The moving speed of the evaluation substrate 100 at this time was 60 mm / s.

In the evaluation substrate 100 taken out from the solder melt in this way, the solder transferred from the solder melt and solidified with cooling adheres to each simulated electrode 110 provided on the evaluation substrate 100. Become. However, at this time, depending on the state of the original solder melt, the solder adhering to each of the two adjacent simulated electrodes 110 on the evaluation substrate 100 may be in an integrated state. Here, the integration of the solder adhering to the two adjacent simulated electrodes 110 is referred to as "a solder bridge has occurred".

〔Evaluation method〕
Subsequently, an evaluation method of the solder bridge with respect to the evaluation substrate 100 to which the solder is adhered in this manner will be described.
The evaluation substrate 100 (untreated substrate or treated substrate) to which the solder was attached, which was obtained by the above procedure, was visually observed, and the state of occurrence of the solder bridge in each was examined.
As described above, each evaluation substrate 100 is provided with three pattern groups (first pattern group 101 to third pattern group 103), and each pattern group has five electrode groups (first pattern group). 1 electrode group A to 5th electrode group E) are provided. Since each of the electrode groups is composed of 31 simulated electrodes 110, the maximum number of solder bridges generated in each electrode group is 30. Here, in one electrode group, even if two or more solder bridges are formed between two adjacent simulated electrodes 110, the number of solder bridges generated at this portion is 1. did. Further, when viewed as a whole of the evaluation substrate 100, the maximum number of solder bridges generated in each of the three electrode groups having the same configuration (for example, the three first electrode groups A) is 90.

〔Evaluation results〕
Now, the evaluation result of the solder bridge will be described.
Table 2 shows the state of occurrence of solder bridges on the treated substrate (evaluation substrate 100) that was soldered using the solder product of Example 1. Table 3 shows the state of occurrence of solder bridges on the treated substrate (evaluation substrate 100) that was soldered using the solder product of Comparative Example 3. Table 4 shows the state of occurrence of solder bridges on the untreated substrate (evaluation substrate 100) that was soldered using the solder product of Example 1. Table 5 shows the state of occurrence of solder bridges on the untreated substrate (evaluation substrate 100) that was soldered using the solder product of Comparative Example 3.

Here, Tables 2 to 5 show the solder bridges generated in each of the first electrode group A to the fifth electrode group E constituting the first pattern group 101 to the third pattern group 103 formed on the evaluation substrate 100. The relationship between the number of solder bridges generated in the three electrode groups having the same configuration (five of the first electrode group A to the fifth electrode group E) and the occurrence rate (%) is shown. ..

{Example 1 (processed substrate)}
First, with reference to Table 2, the state of occurrence of solder bridges on the treated substrate (evaluation substrate 100) that has been soldered using the solder product of Example 1 will be described. In the following, this will be referred to as "Example 1 (processed substrate)" (the same applies hereinafter).

In the case of Example 1 (treated substrate), the total number of solder bridges in all the first electrode group A is 0 (occurrence rate: 0%), and the total number of solder bridges in all the second electrode group B is 2 (). Occurrence rate: 2%), and the total number of solder bridges in all the third electrode group C was 11 (occurrence rate: 12%). Further, in the case of Example 1 (processed substrate), the total number of solder bridges in all the fourth electrode group D is 30 (occurrence rate: 33%), and the total number of solder bridges in all the fifth electrode group E is 44. The number was (incidence rate: 49%). Therefore, in the case of Example 1 (treated substrate), the occurrence rate of the solder bridge was 0% at the lowest, and 50% or less (49%) at the highest.

{Comparative Example 3 (Processed Substrate)}
Next, the case of Comparative Example 3 (processed substrate) will be described with reference to Table 3.
In the case of Comparative Example 3 (treated substrate), the total number of solder bridges in all the first electrode group A is 1 (occurrence rate: 1%), and the total number of solder bridges in all the second electrode group B is 10 (the total number of solder bridges). Occurrence rate: 11%), and the total number of solder bridges in all the third electrode group C was 22 (occurrence rate: 24%). Further, in the case of Comparative Example 3 (processed substrate), the total number of solder bridges in all the fourth electrode group D is 48 (occurrence rate: 53%), and the total number of solder bridges in all the fifth electrode group E is 81. The number was (incidence rate: 90%). Therefore, in the case of Comparative Example 3 (treated substrate), the occurrence rate of the solder bridge was 1% at the lowest, and greatly exceeded 50% (90%) at the highest.

{Example 1 (unprocessed substrate)}
Further, the case of Example 1 (unprocessed substrate) will be described with reference to Table 4.
In the case of Example 1 (untreated substrate), the total number of solder bridges in all the first electrode group A is 0 (occurrence rate: 0%), and the total number of solder bridges in all the second electrode group B is 0 (). Occurrence rate: 0%), and the total number of solder bridges in all the third electrode group C was 6 (occurrence rate: 6.7%). Further, in the case of Example 1 (untreated substrate), the total number of solder bridges in the total 4th electrode group D is 24 (occurrence rate: 27%), and the total number of solder bridges in the total 5th electrode group E is 25. The number was (incidence rate: 28%). Therefore, in the case of Example 1 (untreated substrate), the occurrence rate of the solder bridge was 0% at the lowest and 30% or less (28%) at the highest.

{Comparative Example 3 (Unprocessed Substrate)}
This time, the case of Comparative Example 3 (unprocessed substrate) will be described with reference to Table 5.
In the case of Comparative Example 3 (untreated substrate), the total number of solder bridges in all the first electrode group A is 76 (occurrence rate: 84%), and the total number of solder bridges in all the second electrode group B is 76 (). Occurrence rate: 84%), and the total number of solder bridges in all the third electrode group C was 75 (occurrence rate: 83%). Further, in the case of Comparative Example 3 (untreated substrate), the total number of solder bridges in all the fourth electrode group D is 81 (occurrence rate: 90%), and the total number of solder bridges in all the fifth electrode group E is 90. The number was (incidence rate: 100%). Therefore, in the case of Comparative Example 3 (untreated substrate), the occurrence rate of the solder bridge was 83% at the lowest and 100% (all) at the highest.

{Comparison between each example and each comparative example}
Although detailed description is not given here, the same tests and evaluations as in Example 1 and Comparative Example 3 were carried out for Example 2, Example 3, Comparative Example 1 and Comparative Example 2.
Table 6 shows a list of evaluation results when the evaluation substrate 100 (treated substrate or untreated substrate) is soldered using the solder products of Examples 1 to 3 and Comparative Examples 1 to 3. There is. In Table 6, as the evaluation results for the treated substrates, those with the highest solder bridge occurrence rate of 50% or less are indicated by "○", and those exceeding 50% are indicated by "×". Each is shown. Further, in Table 6, as the evaluation result for the untreated substrate, the maximum value of the occurrence rate of the solder bridge is "○" when it is 30% or less, and "x" when it is over 30%. Each is shown.

From Table 6, when the solder products of Examples 1 to 3 obtained by filtering using the filter 12 having the opening s of 10 μm or less are used, the filtration is performed using the filter having the opening s of 20 μm or more. It can be seen that the occurrence rate of the solder bridge is lower than that in the case of using the solder products of Comparative Examples 1 and 2. Further, when the solder products of Examples 1 to 3 obtained by filtering using the filter 12 having the opening s of 10 μm or less are used, the solder products of Comparative Example 3 not subjected to the filtration using the filter 12 are used. It can be seen that the occurrence rate of the solder bridge is lower than that in the case of the case.

(viscosity)
Next, the evaluation of viscosity will be described. Here, the viscosity of the solder products of Example 1 and Comparative Example 3 was evaluated.

〔Measuring method〕
Now, I will explain the viscosity measurement method that was executed this time.
First, the target solder product (here, the solder product of Example 1 or Comparative Example 3) is put into an alumina crucible (not shown) and heated in an argon atmosphere to solder. A solder melt obtained by melting the product was obtained. Next, the temperature of the solder melt in the crucible was adjusted to 300 ° C. Then, using a known vibration viscometer, the viscosity of the solder melt was measured every 5 ° C. until it reached 220 ° C. while gradually lowering the temperature of the solder melt from 300 ° C.

〔Measurement result〕
FIG. 4 is a diagram showing the relationship between temperature and viscosity in a solder melt obtained by melting the solder products of Example 1 and Comparative Example 3. In FIG. 4, the horizontal axis is temperature (° C.) and the vertical axis is viscosity (Pa · s).
It can be seen that the viscosities of both Example 1 and Comparative Example 3 gradually increase as the temperature decreases. However, in the range where the temperature is 220 ° C. to 300 ° C., the viscosity is about 0.0035 Pa · s to 0.004 Pa · s in Example 1, whereas the viscosity is 0.005 Pa · s in Comparative Example 3. It can be seen that the temperature is always higher than that of Example 1 at about s to 0.006 Pa · s. The fact that the viscosity is lower at the same temperature means that the solder melt obtained by using the solder product of Example 1 is "solder wet" as compared with the solder melt obtained by using the solder product of Comparative Example 3. It is considered to suggest that both "property" and "soldering property" can be good. In particular, if the latter "soldering property" is good, it can be said that the above-mentioned "solder bridge" is less likely to occur.

(Oxygen concentration)
Next, the evaluation of the oxygen concentration will be described. Here, the solder products of Example 1 and Comparative Example 3 were evaluated with respect to the oxygen concentration.

〔Measuring method〕
Now, I will explain the method of measuring oxygen concentration that was executed this time.
First, the soldered evaluation substrate 100 used in the evaluation of the solder bridge described above was produced by the procedure described above. At this time, the solder product of Example 1 or Comparative Example 3 was used as the raw material of the solder melt.
Then, for the solder transferred / adhered to the simulated electrode 110 provided on the evaluation substrate 100, oxygen in the depth direction in the solder is used by using a TOF-SIMS (Time of Flight-SIMS) device. The concentration and the average oxygen concentration in the solder were determined. Here, three samples are prepared for each of Example 1 and Comparative Example 3 (Examples 1-1 to 1-3 and Comparative Examples 3-1 to 3-3). did.

〔Measurement result〕
FIG. 5A is a diagram showing the oxygen concentration distribution in the depth direction in the solder obtained by soldering the solder products of Example 1 and Comparative Example 3. In FIG. 5A, the horizontal axis is the depth (depth (μm)) from the surface of the solder, and the vertical axis is the oxygen concentration (Ocontent [au]). Further, FIG. 5B is a diagram showing the average oxygen concentration in each solder. In FIG. 5B, the horizontal axis is the name of each Example and each Comparative Example, and the vertical axis is the average oxygen concentration (integral O content [a.u.]).

{Oxygen concentration distribution in the depth direction}
First, the oxygen concentration distribution in the depth direction in the solder will be described with reference to FIG. 5A.
As shown in FIG. 5A, in the case of solder obtained by soldering the solder product of Example 1 (Examples 1-1 to 1-3), the oxygen concentration in the vicinity of the surface of the solder is relative. However, the oxygen concentration at a depth of 1 μm or more from the surface is lower than that. On the other hand, in the case of solder obtained by soldering the solder product of Comparative Example 3 (Comparative Examples 3-1 to 3-3), the oxygen concentration of the solder has little relation to the depth and is generally It is getting higher. In particular, focusing on the oxygen concentration at a portion having a depth of 1 μm or more from the surface, Examples 1-1 to Example 1-3 are one digit or more as compared with Comparative Examples 3-1 to 3-3. It is understood that the oxygen concentration is low at the double digit level.

{Average oxygen concentration}
Subsequently, the average oxygen concentration in the solder will be described with reference to FIG. 5 (b).
As shown in FIG. 5B, in the solder obtained by soldering the solder product of Example 1 (Examples 1-1 to 1-3), the solder product of Comparative Example 3 is soldered. It is understood that the average oxygen concentration is lower by a double digit level as compared with the obtained solder (Comparative Examples 3-1 to 3-3).

{About oxygen in the solder}
From the above results, it is suggested that the solder obtained by using the solder product of Example 1 may contain less metal oxide in the solder than the solder obtained by using the solder product of Comparative Example 3. It is thought that it is doing. Here, the fact that the amount of metal oxide contained in the solder is small means that the amount of foreign matter (solid matter) remaining unmelted in the solder melt is reduced. The fact that the amount of foreign matter in the solder melt is reduced is considered to suggest that both "solder wetting property" and "solder breakability" can be improved.

[Residues generated by filtration]
FIG. 6 is an optical photograph of the residue remaining on the filter 12 after the filtration step of step 30 in the production of the solder product of Example 1.
Further, FIG. 7 is a SEM (Scanning Electron Microscope) photograph of the residue shown in FIG.
Further, FIG. 8 is an SEM photograph of the needle-shaped body present in the residue shown in FIG. 7.

First, as shown in FIG. 6, the residue as an example of the solid matter has an overall grayish color and has a structure formed by agglomerating sand-like particles. Therefore, it is suggested from the appearance that the residue shown in FIG. 6 contains a metal oxide.

Further, as shown in FIG. 7, the surface of the residue is like a cactus, and the needle-shaped spicules project from the surface of the residue. However, it is considered that such a needle-like body is actually present not only on the surface of the residue but also inside the residue.

Further, as shown in FIG. 8, the needle-like body existing in the residue has a length of about 100 μm to 200 μm and a diameter of about 12 μm to 20 μm. As is clear from FIG. 8, the cross section of the needle-shaped body has a polygonal shape. This is considered to suggest that this needle-shaped body is composed of some kind of single crystal body.

Then, when the needle-shaped body shown in FIG. 8 was subjected to elemental analysis using EPMA (Electron Probe Micro Analyzer), it was found that the needle-shaped body contained both tin and copper. .. From this result, it is suggested that this needle-shaped body is composed of an alloy of tin and copper, an oxide of tin and copper, and the like. When an experiment was conducted in which the residue was heated to 500 ° C., the needle-like body present in the residue did not melt at 500 ° C. and remained as it was. Therefore, it is considered that this spicule is not Cu ₆ Sn ₅ (melting point: about 435 ° C.), which is a kind of alloy of tin and copper.

Further, as is clear from FIG. 8, since the diameter of the needle-shaped body contained in the residue is more than 10 μm, this needle-shaped body cannot pass through the filter 12 in which the opening s is set to 10 μm or less. Therefore, it is considered that the solder products of Examples 1 to 3 do not contain such a needle-like body as a foreign substance.

On the other hand, this needle-shaped body can pass through the filter 12 in which the opening s is set to 20 μm or more. Further, this needle-shaped body can be maintained as it is in the absence of the filter 12. Therefore, it is considered that such needle-like bodies are contained as foreign matter in the solder products of Comparative Examples 1 to 3.

Therefore, when the solder products of Examples 1 to 3 are used, the evaluation result of the solder bridge is "○", and when the solder products of Comparative Examples 1 to 3 are used, the evaluation result of the solder bridge is "○". It is probable that it became "x".

Here, the diameter of the needle-shaped body present in the residue was about 12 μm to 20 μm as shown in FIG. However, it is considered that the diameter of this needle-shaped body does not exceed 10 μm from the beginning, but gradually increases with growth, and when it becomes thick to some extent, the increase in diameter slows down. ..

In recent years, especially in the field of smartphones and the like, the wiring pattern of a printed wiring board to be soldered has been miniaturized (thinning). For this reason, the so-called L / S (line / space) value of a printed wiring board has been less than 100 μm for several years, and recently, a value of 10 μm / 10 μm has been studied.

When soldering to a printed wiring board whose L / S is set to 10 μm / 10 μm, if a needle-like body with a diameter of less than 10 μm is present in the solder product that is the source of the solder, the above-mentioned solder bridge There is a concern that Therefore, when such a thing is taken into consideration, it is possible to use the filter 12 in which the opening s is set to 5 μm or less in the filtration step of step 30, as in the above-mentioned Examples 1 and 2. desirable.

[Other]
Here, a binary solder product called a Sn—Cu system containing tin (main component) and copper (sub component) has been described as an example. However, although detailed description is not given here, similar results have been obtained for other solder products containing tin as a main component.
Here, examples of binary solder products other than Sn—Cu are Sn—Ag, Sn—Bi, and Sn—Zn. Examples of the ternary solder product include Sn-Ag-Cu type, Sn-Ag-Bi type, Sn-Ag-In type, Sn-Zn-Bi type and Sn-Zn-Al type. .. Further, examples of the quaternary solder product include Sn-Ag-Cu-Bi type and Sn-Ag-In-Bi type. Furthermore, examples of the quintuple-based solder products include Sn-Ag-Cu-Ni-Ge series. The same result can be obtained for solder products of 6 elements or more.

Further, here, the method of filtering the molten metal formed by melting the solder raw material by using the filter 12 has been described as an example, but the present invention is not limited to this. For example, a technique such as centrifugation or solid-liquid separation may be used to remove solid matter having a diameter of more than 10 μm (more preferably more than 5 μm) and existing in the molten metal from the molten metal. ..

1 ... molten metal before filtration, 2 ... molten metal after filtration, 10 ... filtration device, 11 ... container, 12 ... filter, 13 ... heater, 100 ... evaluation substrate, 101 ... first pattern group, 102 ... second pattern group, 103 ... Third pattern group, 110 ... Simulated electrode

Claims (7)

A heating process in which a raw material containing tin as a main component and a metal element other than lead as an auxiliary component is melted by heating to form a molten metal.
A filtration step of filtering the molten metal with a filter having an opening of 10 μm or less,
A method for producing a solder product, which comprises a cooling step of solidifying the filtered molten metal by cooling. The method for manufacturing a solder product according to claim 1, wherein in the filtration step, the filter is heated. The method for manufacturing a solder product according to claim 1 or 2, wherein in the filtration step, a stainless steel wire mesh is used as the filter. The method for producing a solder product according to any one of claims 1 to 3, wherein in the heating step, the raw material contains copper as the metal element as a sub-component. A heating process in which a raw material containing tin as a main component and a metal element other than lead as an auxiliary component is melted by heating to form a molten metal.
A step of taking out a solid substance having a diameter of more than 10 μm and existing in the molten metal from the molten metal set at 230 ° C. to 260 ° C.
A method for producing a solder product, which comprises a cooling step of solidifying the molten metal from which the solid matter has been taken out by cooling. The method for manufacturing a solder product according to claim 5, wherein in the extraction step, the molten metal is set at 235 ° C to 250 ° C. The method for manufacturing a solder product according to claim 5 or 6, wherein in the taking-out step, the solid matter having a size of more than 5 μm is taken out from the molten metal.