JP5919545B2 - Solder material and mounting body - Google Patents

Description

  The present invention mainly relates to a solder material and a mounting body in a solder paste or the like used for soldering an electronic circuit board.

  In an electronic circuit board, generally, a Cu substrate electrode whose electrode material is Cu is often used. In general electronic components mounted on an electronic circuit board, Cu component electrodes in which Sn is plated on Cu are used. However, in-vehicle products such as electric compressors, DC / DC converters, inverters, and headlamps, there are cases where Au component electrodes that have been subjected to Au flash plating by flash processing that performs thin plating in a short time may be used. The reason is that, on the joint surface between the Au component electrode and the solder material, wettability is improved, so that a large fillet is formed and joint reliability is increased. As an example, an electronic circuit board having a Cu substrate electrode and an electronic component having a Cu component electrode or an Au component electrode are joined by soldering to form a mounting body. FIG. 9 shows a schematic cross-sectional view of the mounted body.

  The mounting body 900 includes an electronic circuit board 930 having Cu substrate electrodes 931 and 932, an electronic component 920 having an Au component electrode 921 on the Cu substrate electrode 931, an electronic component 940 having a Cu component electrode 941 on the Cu substrate electrode 932, The solder portions 911 and 912 are formed using a solder material having a composition of Sn—Ag—Bi—In.

  For soldering the electronic circuit board 930 and the electronic components 920 and 940 used here, a solder material having a composition of Sn—Ag—Bi—In composed of four kinds of elements is used (for example, a patent) Reference 1). In such a solder material, thermal fatigue characteristics related to fatigue failure caused by thermal stress accompanying temperature change are enhanced by a technique called a solid solution strengthening mechanism. Here, the solid solution strengthening mechanism is a technique that makes it difficult for the solder material to deteriorate by replacing some of the metal atoms arranged in a lattice with different kinds of metal atoms and distorting the lattice.

  In the solder material having the Sn—Ag—Bi—In composition described above, In is dissolved in the Sn lattice, and the thermal fatigue characteristics are enhanced. Specifically, Sn-3.5 mass% A solder material having a composition such as Ag-0.5 mass% Bi-6 mass% In is used. Here, Ag and Bi are added. Ag is added for improving the alloy strength and lowering the melting point by precipitation strengthening, and Bi is added for lowering the melting point.

Japanese Patent No. 3040929

  However, in the case of soldering to the Au component electrode 921, it has been found that a solder material having a composition of Sn—Ag—Bi—In does not necessarily have a sufficiently high thermal fatigue characteristic. On the other hand, in the case of soldering to the Cu component electrode 941, the thermal fatigue characteristics were kept high.

  The inventors have analyzed the reason as follows. That is, in a solder material having a composition of Sn—Ag—Bi—In, the thermal fatigue characteristics change depending on the In content. The thermal fatigue property here is that the occurrence of cracks is not confirmed by observation of the cross section of the soldered joint after the temperature cycle test is carried out under the test conditions of −40 ° C./150° C. (reliability test conditions for in-vehicle products). Shown in number of cycles. For example, the composition of the solder material after soldering is Sn-3.5 mass% Ag-0.5 mass% Bi-6 mass% In and Sn-3.5 mass% Ag-0.5 mass% Bi-5. When compared with 0.5 mass% In, the number of cycles in the temperature cycle test is 2300 cycles and 2150 cycles, and the number of cycles (thermal fatigue characteristics) decreases as In decreases.

  The alloy strength related to thermal fatigue characteristics increases as the In content increases, but becomes maximum when the In content is approximately 6% by mass, and decreases when the In content exceeds this. That is, when the In content is about 6% by mass, the number of cycles in the temperature cycle test is high, so that the thermal fatigue characteristics are the highest. Therefore, in order to effectively use the solid solution strengthening mechanism by In, it is desirable to control the In content of the solder material more accurately.

  This will be described in detail below. First, in a combination of a Cu component electrode and a solder material having a composition of Sn—Ag—Bi—In, Cu and In are not highly reactive, so that the Sn lattice that contributes to the improvement of thermal fatigue characteristics is fixed. Since the In content of the dissolved In does not change during soldering, the thermal fatigue characteristics are kept high.

  On the other hand, for the Au component electrode, Ni plating having a film thickness of 1 to 5 μm is applied on the Cu electrode, and Au flash plating having a film thickness of 0.03 to 0.07 μm is further applied on the Ni plating. In this structure, Au melts into Sn-Ag-Bi-In during soldering with heating, and Ni plating is exposed. The Ni plating has a composition of 90 mass% Ni and 10 mass% P, and since In and P are highly reactive, In reacts with P to form a compound InP having an In-P composition. Generate. As a result, the amount of In dissolved in the Sn lattice, which contributes to the improvement of thermal fatigue characteristics, decreases, and the substantial In content decreases.

  Here, when the In content of the Sn-Ag-Bi-In solder material before soldering is increased in order to enhance the thermal fatigue characteristics of the Au component electrode in which the In content after soldering decreases. The thermal fatigue characteristics of the Au component electrode are enhanced. However, when the same solder material is used in consideration of workability for soldering of an electronic component mounted on one electronic circuit board, the Cu component electrode of the electronic component is made of In before the soldering. On the contrary, the thermal fatigue characteristics decrease depending on the increase in In from the content. Thus, even if the In content of the solder material before soldering is simply increased in order to prevent a decrease in In after the soldering of the Au component electrode, the thermal fatigue characteristics of the Cu component electrode are decreased. Therefore, it was necessary to examine means other than the addition of In.

  The present invention solves the above-mentioned conventional problems, and satisfies the thermal fatigue characteristics of Au component electrodes even in a mounted body after soldering with an electronic component having an Au component electrode mounted on an electronic circuit board. It is an object of the present invention to provide a solder material and a mounting body that can be used.

To achieve the above objective,
The first invention is
5.6 to 6.8% by mass of In,
0.3-4.0 mass% Ag,
0.2 to 1.0 mass% Bi,
0.054 to 9.0% by mass of Ga,
The balance is a solder material characterized in that it is only 79.2% by mass or more of Sn.

In the first invention,
6.3 to 6.8% by mass of In,
2.3 to 3.7 mass% Ag,
0.3-1.0 mass% Bi;
Containing 1.0-5.0 mass% Ga,
The balance is preferably only 83.5% by mass or more of Sn.

  In 1st invention, it is preferable to contain 2.0-9.0 mass% Ga.

  In 1st invention, it is preferable to contain 3.0-9.0 mass% Ga.

  In 1st invention, it is preferable to contain 6.0-9.0 mass% Ga.

The second invention is a mounting body characterized in that an electronic component having an Au component electrode and an electronic circuit board having a substrate electrode are joined by the solder material of the first invention.

In the second invention, the Au component electrode preferably has Ni plating containing P.

In the second invention, the substrate electrode is preferably a Cu substrate electrode or an Au substrate electrode.

According to the configuration of the first invention, it is possible to provide a solder material that can satisfy the thermal fatigue characteristics of the Au component electrode mounted on the electronic circuit board after soldering.

Moreover, the structure of the said 2nd invention can provide the mounting body with which the Au component electrode mounted in the electronic circuit board after soldering satisfy | filled the thermal fatigue characteristic.

The graph which shows the reliability test result of the alloy with the composition of Sn-3.5 mass% Ag-0.5 mass% Bi which added In for demonstrating the solder material of Embodiment 1 in this invention. Schematic configuration diagram showing the configuration of the Au electrode prepared as a sample Outline of measuring In content after joining of Cu electrode or Au electrode prepared as sample and alloy having composition of Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In Illustration For explaining the solder material according to the first embodiment of the present invention, an alloy having a composition of Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In is used. The graph which shows the analysis result of In content rate inside each solder after soldering to an electrode and an Au electrode was performed Ga is added to the composition of 90 mass% Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In for explaining the solder material according to the first embodiment of the present invention. Showing the analysis result of the In content in the solder after the soldering to the Au electrode using the alloy was performed Ga is added to the composition of 90 mass% Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In for explaining the solder material according to the first embodiment of the present invention. Graph showing the liquidus of an alloy Schematic sectional view of a mounting body according to an embodiment of the present invention Schematic configuration diagram showing composition of substrate electrode, solder material and component electrode before and after soldering Schematic cross-sectional view of a mounting body using conventional solder materials

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
First, the principle regarding the solder material according to the first embodiment will be described with reference to FIG.

  FIG. 1 shows the reliability of an alloy having a composition of Sn-3.5 mass% Ag-0.5 mass% Bi to which In is added for explaining the solder material according to the first embodiment of the present invention. It is a graph which shows a property test result.

  In FIG. 1, the In content on the horizontal axis is a substantial In content of In that is dissolved in the solder after soldering, more specifically, In that is dissolved in the Sn lattice. .

  The number of test cycles on the vertical axis is the FR5 board with the FR grade (FR) (Frame Regentant Grade) mounted with a chip capacitor of 1608 size (1.6 mm x 0.8 mm). This is the number of cycles in which generation of cracks was not confirmed by cross-sectional observation of the soldered joint after being performed under the test conditions of 40 ° C./150° C.

  In the reliability test of in-vehicle products mounted in the vicinity of the engine of an automobile, the number of cycles of 2000 cycles or more is required in the required specifications (in this case, thermal fatigue characteristics must be satisfied when the number of cycles is 2000 cycles or more. And).

  The number of cycles is 5.5% by mass (2150 cycles), 6.0% by mass (2300 cycles), and 6.5% by mass (2200 cycles) of the In content dissolved in the solder after soldering. In some cases, it is 2000 cycles or more, but when the In content is 5.0% by mass or less or 7.0% by mass or more, it is less than 2000 cycles.

A quadratic function obtained by using an approximate curve using the above numerical data (Expression 1)
(Number of test cycles)
= −410.7 × (In content) ² + 4919.6 × (In content) -12446
It is illustrated as a graph.

  Therefore, the range of In content that can secure the number of cycles of 2000 cycles or more, which is the vehicle-mounted standard, is approximately 5.2 to 6.8% by mass, and the management width is approximately ± 0.8% by mass.

  And since the fluctuation range of the In content of the solder alloy in mass production is about ± 0.5 mass%, the In content is 4.7 (= 5.2-0.5) mass% or more and 7.3 ( = 6.8 + 0.5) mass% or less, but more preferably 5.7 (= 5.2 + 0.5) mass% or more and 6.3 (= 6.8−0.5) mass% or less. .

  Next, the influence of P contained in the Ni plating will be described with reference mainly to FIGS.

  As the Au electrode and Cu electrode used here, a sample prepared for measurement is used.

  FIG. 2 is a schematic configuration diagram showing a configuration of an Au electrode prepared as a sample, and FIG. 3 shows a Cu electrode and an Au electrode prepared as a sample and Sn-3.5 mass% Ag-0.5 mass% Bi. It is a schematic explanatory drawing which measures In content rate after joining with the alloy which has a composition of -6.0 mass% In.

  The Au electrode prepared as a sample is a Cu foil with a Cu electrode having a film thickness of 35 μm, and Ni plating with a film thickness of 1 to 5 μm is used as an electroless plating that does not require energization like electroplating. The Au flash plating having a film thickness of 0.03 to 0.07 μm is applied on the Ni plating.

  For example, the thickness of Ni plating is 3 μm, and the thickness of Au flash plating is 0.05 μm.

  A solder material having a composition of Sn-3.5% by mass, Ag-0.5% by mass, Bi-6.0% by mass, In has a shape with a diameter of 5 mm and a thickness of 0.15 mm. And heated on a hot plate at 240 ° C. for 30 seconds and gradually cooled at room temperature.

  The center part of the cross section polished so that the vertical cross section appears is analyzed by a method using EDX (Energy Dispersive X-ray spectroscopy), and the In content is measured.

  Here, the central portion is a position corresponding to a position at a half of the thickness of the solder and a half of the solder spreading width.

  FIG. 4 shows an example of an alloy having a composition of Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In after soldering to a Cu electrode and an Au electrode. It is a graph which shows the analysis result of In content rate in each solder.

  The measured In content of In dissolved in the Sn lattice, which contributes to the improvement of thermal fatigue properties, has decreased from the initial In content of 6.0% by mass. The Cu electrode is 5.9% by mass, and the Au electrode is 5.1% by mass.

  With respect to the Au electrode, Au diffuses into the solder during heating, and Ni plating having a composition of 90 mass% Ni and 10 mass% P formed under the Au flash plating is exposed.

  As described above, since In reacts with P to produce compound InP, the amount of In dissolved in the Sn lattice decreases, and the substantial In content in the case of the Au electrode Is significantly reduced as compared with the Cu electrode.

  For this reason, since the range of In content corresponding to the vehicle-mounted standard is approximately 5.2 to 6.8% by mass as described above, the Au electrode does not satisfy the vehicle-mounted standard.

Since the specific gravity of Ni plating is 7.9 g / cm ³ , the weight of P contained in the Ni plating is 7.9 × T × using the Ni plating film thickness T and the Ni plating area S. The weight of P contained in the Ni plating varies in proportion to the thickness T of the Ni plating.

  Based on such a phenomenon, the present inventors have found that the addition of an element that reacts more easily with P and forms a compound than In is effective in suppressing the decrease in In content. I found it.

  Among many elements, an element found as such an element is Ga (gallium) which reacts with P to form a GaP compound, which will be described below.

  Here, the solder material according to the present embodiment will be specifically described with reference to FIGS.

  FIG. 5 shows a composition of 90 mass% Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In for explaining the solder material according to the first embodiment of the present invention. It is a graph which shows the analysis result of In content in the solder after soldering with respect to Au electrode was performed using the alloy with which Ga was added.

  FIG. 6 shows a composition of 90 mass% Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In for explaining the solder material according to the first embodiment of the present invention. It is a graph which shows the liquidus line 601 of the alloy with which Ga was added with respect to it.

  First, the lower limit of the Ga content will be described with reference mainly to FIG.

  Here, the analysis is performed by the same method as described above, and the In content after the soldering with the Au electrode is measured.

  The sample is prepared as follows.

  89.8 g of Sn is put into a ceramic crucible and left in an electric jacket heater whose temperature is adjusted to 500 ° C.

  6.0 g of In is added after it is confirmed that Sn has melted, and stirring is performed for 3 minutes.

  0.5 g of Bi is charged and stirring is further performed for 3 minutes.

  3.5 g of Ag is charged and stirring is further performed for 3 minutes.

  0.2 g of Ga is charged and further stirring for 3 minutes is performed.

  Thereafter, the crucible is taken out from the electric jacket heater and immersed in a container filled with water at 25 ° C. to be cooled.

  The In content is (1) 5.1% by mass when the Ga content is zero, but (2) When the Ga content increases, the decrease in In is suppressed, (3) When the Ga content is 0.2% by mass, it is 5.51% by mass, and (4) When the Ga content is 0.4% by mass, it is approximately 5.97% by mass.

  (5) Even if the Ga content is 0.5% by mass, 0.6% by mass, 0.7% by mass, and 0.8% by mass, there is almost no change in the In content.

When an approximate straight line is drawn using numerical values when the Ga content is 0 mass% to 0.4 mass%, a linear function (Equation 2)
(In content)
= 2.18 x (Ga content) + 5.084
Is obtained.

  Therefore, in order to secure the In content of 5.2% by mass or more necessary for satisfying the vehicle-mounted standard even in combination with the Au electrode, the Ga content is preferably 0.054% by mass or more. . If the Ga content is 0.054% by mass or more, the In content after soldering is 5.2% by mass or more even in combination with the Au electrode, and the reliability of the on-vehicle standard can be satisfied.

  However, since the fluctuation range of the In content of the solder alloy in mass production is approximately ± 0.5% by mass, the In content may be slightly reduced.

In such a case, the approximate straight line is a linear function in which the graph of (Equation 2) has undergone a downward movement corresponding to −0.5 mass%, which is the lower limit of the fluctuation range in mass production (Equation 3)
(In content)
= 2.18 x (Ga content) + 4.584
The In content is 4.7 mass% when the Ga content is 0.054 mass%.

  Therefore, when the lower limit of the fluctuation range in mass production is considered, in order to secure an In content of 5.2% by mass or more, the Ga content has a margin of 0.28% by mass or more (this value is It is more preferable that (5.2−4.584) /2.18=0.283≈0.28). In the above description, the case where an alloy having a composition of 90 mass% Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In is used has been described. Since the content ratio varies with a certain ratio, even when the In content ratio is different, it can be handled accordingly.

  Next, the upper limit of the Ga content will be described with reference mainly to FIG.

  That is, when the Ga content is too large, the liquidus temperature is lowered, so that the heat resistance is lowered and the reliability is deteriorated.

  More specifically, the liquidus temperature represented by the liquidus line 601 is 232 ° C. when the Ga content is 0% by mass, and 200 ° C. when the Ga content is 9% by mass. When the Ga content is 29% by mass, the temperature is 150 ° C. Here, the liquidus temperature is a temperature at which all the alloy heated from the solid state is melted to be in a liquid state.

  Table 1 explains the relationship between the Ga content and the reliability when the Ga content is 0.5% by mass, 1% by mass,..., 30% by mass. The shape change after the temperature cycle test is evaluated (the same applies to other tables, but the unit attached to the numerical data is mass%).

信頼性の評価に関しては、○は形状変化が発生していないことを示しており、△は部分的な形状変化が発生していることを示しており、×は全体で形状変化が発生していることを示している。

Regarding the evaluation of reliability, ◯ indicates that no shape change has occurred, △ indicates that a partial shape change has occurred, and x indicates that the shape change has occurred as a whole. It shows that.

  Therefore, it is desirable that the Ga content is 9% by mass or less in order to guarantee a state in which the shape change important for good soldering does not occur.

  Table 2 explains the relationship between the various compositions of the solder material before soldering and the change in the In content of the solder material after soldering for compositions 1 to 21 and comparative examples, and the reliability and strength are determined. ing.

Ｉｎ含有率変化についての残量は、Ａｕ電極に対するはんだ付けが行われた後の、はんだ内部におけるＩｎ含有率の分析を、ＥＤＸを利用して行うことにより測定される。

The remaining amount with respect to the change in the In content is measured by performing an analysis of the In content in the solder after the soldering to the Au electrode is performed using EDX.

  Regarding the determination about the change in In content, ○ indicates that the In content after soldering is included in the range of 5.2 to 6.8% by mass, and x indicates In content It shows that the rate is in the range of less than 5.2% by mass.

  Regarding reliability judgment, ○ indicates that the standard is satisfied, based on the fact that the number of cycles of the temperature cycle test in the reliability test of in-vehicle products satisfies the required specification of 2000 cycles or more, × Indicates that the standard is not satisfied. Furthermore, on the basis that the required specifications of 2200 cycles or more are satisfied, ◯ indicates that the standard is satisfied, and × indicates that the standard is not satisfied. In addition, a product for which the number of cycles of 2000 cycles or more is required in the required specification is a vehicle-mounted product in the engine room. Further, a product for which the number of cycles of 2200 cycles or more is required in the required specification is a vehicle-mounted product near the engine. A product for which the number of cycles of 2300 cycles or more is required in the required specifications is an in-vehicle product directly mounted on an automobile engine, that is, an in-vehicle product in contact with the engine.

  Regarding the strength judgment, based on the tensile strength of the solder material, ○ indicates that it satisfies 60 MPa or more and can be used for chip parts up to 0.9 mm × 0.8 mm, and ◎ indicates that 65 MPa or more is satisfied and QFP (quad flat ◎ indicates that it can be used for large-sized semiconductor parts such as package) and BGA (ball grid array), and ◎ indicates that it can be used for large-sized parts such as aluminum electrolytic capacitors and module parts. ◎◎◎ satisfies 75MPa or more and indicates that it can be used for heavy parts such as coils and transformers. In addition, the tensile strength is measured with a No. 4 test piece of JIS Z 2201.

  From the reliability determination of the compositions 1-21, it can be seen that the decrease in the In content was suppressed by containing Ga in the solder material having the Sn-Ag-Bi-In composition. Moreover, in order to satisfy a stricter vehicle-mounted reference | standard, it turns out that it is desirable that Ga content rate is 3.0 mass% or more.

  In the comparative example, since an effective element was not added to suppress the decrease in the In content, the In content after soldering was 5.1 mass% (the change in In content was −0.9%). Since it was (mass%), the judgment about it is x.

  Next, specific examples of the solder joining method are given as processes 1 to 3 below.

  First, as Process 1, an example in which an electronic component having a Cu component electrode and an electronic circuit substrate having an Au substrate electrode are joined by reflow soldering using a solder material having composition 1 will be described. Solder material of composition 1 (Sn-3.5 mass% Ag-0.5 mass% Bi-6 mass% In-0.1 mass% Ga solder alloy) into solder grains having a particle size distribution of 25 to 45 μm in diameter Process. The solder grains 88% by mass and flux 12% by mass are mixed to form a paste. This paste is printed on the Au substrate electrode of the substrate using a metal mask with a screen printer (“SP70” manufactured by Panasonic Corporation). The metal mask has a laser-processed thickness of 120 μm, and an opening of 0.8 mm × 0.8 mm is formed in accordance with the chip resistance of 1608 size. The substrate is 1.6 mm thick and the material is FR5. The Au substrate electrode on the substrate is formed by subjecting a Cu electrode to Ni plating with a thickness of 2 μm and applying Au flash plating with a thickness of 0.05 μm thereon. On the Au substrate electrode after paste printing, a 1608 size chip resistor having a Cu component electrode is mounted with a chip mounter (“BM123” manufactured by Panasonic Corporation). The substrate on which the chip components are mounted is heated and soldered in a reflow furnace (“REF” manufactured by Panasonic Corporation). Heating is performed in an air atmosphere at a preheating temperature of 160 ° C. for 60 seconds, a reflow temperature of 250 ° C. for 20 seconds. The solder is heated and melted to a temperature equal to or higher than the melting point, and Au melts into the melted solder, thereby exposing the Ni plating. The Ni plating is composed of 90% by mass of Ni and 10% by mass of P. Since P and Ga are highly reactive, P reacts with Ga to produce a compound GaP. Even if the amount of In changes, reliability is maintained because a necessary amount of In that contributes to the improvement of thermal fatigue characteristics is secured.

  Next, as Process 2, an example in which an electronic component having a Cu component electrode and an electronic circuit substrate having an Au substrate electrode are joined by a soldering iron using a solder material having composition 1 will be described. A solder material of composition 1 (Sn-3.5 mass% Ag-0.5 mass% Bi-6 mass% In-0.1 mass% Ga solder alloy) is processed into a thread shape having a diameter of 0.8 mm. This thread solder is used for soldering with a soldering iron. During soldering, flux is used to remove oxide on the surface of the Au substrate electrode. The substrate is 1.6 mm thick and the material is FR5. The Au substrate electrode on the substrate is formed by subjecting a Cu electrode to Ni plating with a thickness of 2 μm and applying Au flash plating with a thickness of 0.05 μm thereon. On this Au substrate electrode, a 1608 size chip resistor having a Cu component electrode is mounted with precision tweezers. Heating is performed in 5 seconds with a soldering iron in contact. The solder is heated and melted to a temperature equal to or higher than the melting point, and Au melts into the melted solder, thereby exposing the Ni plating. The Ni plating is composed of 90% by mass of Ni and 10% by mass of P. Since P and Ga are highly reactive, P reacts with Ga to produce a compound GaP. Even if the amount of In changes, reliability is maintained because a necessary amount of In that contributes to the improvement of thermal fatigue characteristics is secured.

  Next, as Process 3, an example in which an electronic component having an Au component electrode and an electronic circuit substrate having a Cu substrate electrode are joined by reflow soldering using a solder material having composition 1 will be described. Solder material of composition 1 (Sn-3.5 mass% Ag-0.5 mass% Bi-6 mass% In-0.1 mass% Ga solder alloy) into solder grains having a particle size distribution of 25 to 45 μm in diameter Process. The solder grains 88% by mass and flux 12% by mass are mixed to form a paste. This paste is printed on the Cu substrate electrode of the substrate using a metal mask with a screen printer (“SP70” manufactured by Panasonic Corporation). The metal mask has a laser-processed thickness of 120 μm, and four openings of 0.9 mm × 0.8 mm are formed in accordance with the crystal resonator chip. The Au component electrode included in the crystal resonator chip is formed by applying Ni plating with a film thickness of 2 μm to a Cu electrode and applying Au flash plating with a film thickness of 0.05 μm thereon. The substrate is 1.6 mm thick and the material is FR5. A Cu substrate electrode is formed on the substrate. A crystal resonator chip is mounted on a Cu substrate electrode after paste printing by a chip mounter (“BM123” manufactured by Panasonic Corporation). The substrate on which the chip components are mounted is heated and soldered in a reflow furnace (“REF” manufactured by Panasonic Corporation). Heating is performed in an air atmosphere at a preheating temperature of 160 ° C. for 60 seconds, a reflow temperature of 250 ° C. for 20 seconds. The solder is heated and melted to a temperature equal to or higher than the melting point, and Au melts into the melted solder, thereby exposing the Ni plating. The Ni plating is composed of 90% by mass of Ni and 10% by mass of P. Since P and Ga are highly reactive, P reacts with Ga to produce a compound GaP. Even if the amount of In changes, reliability is maintained because a necessary amount of In that contributes to the improvement of thermal fatigue characteristics is secured.

  Next, Table 3 explains the relationship between the various compositions of the solder material not containing Bi and the change in the In content for compositions 22 to 25, and the reliability is determined. The various determinations are the same as in Table 2 above.

この表３の組成２２〜２５においては、信頼性判定の結果が全て基準を満足しているから、はんだ材料にＢｉが含有されていなくとも、Ｉｎ含有率の変化に影響を与えないことがわかる。

In the compositions 22 to 25 in Table 3, since the reliability determination results all satisfy the standard, it can be seen that the change in In content is not affected even if Bi is not contained in the solder material. .

  Bi of the solder material is added to adjust the melting temperature of the alloy, and the amount of Bi does not affect the thermal fatigue characteristics of the solder material.

  From the results of the reliability determination of compositions 1 to 25 in Tables 2 and 3, the Ga content is 0.054% by mass or more in order to satisfy the reliability evaluation of the in-vehicle product even in soldering to the Au electrode. Desirably, it is 0 mass% or less, and considering the lower limit of the fluctuation range in mass production, the Ga content is more desirably 0.28 mass% to 9.0 mass% with a slight margin.

  Moreover, the content rate of Ag which comprises the solder material in embodiment is determined for the following reasons. As described above, since the thermal fatigue characteristics are improved by the solid solution strengthening action of In against Sn, the thermal fatigue characteristics vary greatly depending on the amount of In. However, since Ag does not dissolve in Sn, thermal fatigue characteristics do not change greatly.

In addition, since the amount of Ag affects the melting point of the solder material, if the Ag content exceeds 4% by mass, the melting point becomes 235 ° C. or more, and the wetting spread during soldering deteriorates, so it cannot be used. Therefore, the maximum value of the Ag content is 4% by mass. Further, when the Ag content is decreased, the amount of Ag ₃ Sn deposited on the Sn phase is decreased and the mechanical strength characteristics are lowered. Therefore, the minimum value of the Ag content is set to 0.3% by mass.

  Next, the content rate of Bi which comprises the solder material in embodiment is determined for the following reasons. As described in Table 3, the minimum value can be zero because it does not affect the thermal fatigue characteristics of the solder material. Further, since Bi has a property of segregating inside the solder alloy, if it exceeds 1% by mass, the amount of segregation increases and the alloy becomes brittle and cannot be used. Therefore, the maximum Bi content is set to 1% by mass.

  From the above, since Ag and Bi do not affect the thermal fatigue characteristics of the solder material, the effect of the In content in Sn-Ag-Bi-In is similarly handled in Sn-Ag-In and Sn-Bi-In. I think you can.

  In addition, about the composition of solder material, in FIG. 5, FIG. 6, it is "90 mass% Sn-3.5 mass% Ag-0.5 mass% Bi-6. “Composition of 0% by mass In” is replaced with the composition of solder material in Tables 2 and 3, and “89.9% by mass Sn−3.5% by mass Ag−0.5% by mass”. % Bi-6.0 mass% In-0.1 mass% Ga ", and the Sn content is reduced by the addition of Ga. It is considered that a small amount of Sn does not affect the change in the In content.

  As is clear from the above description, the solder material of the present invention has 5.6 to 6.8% by mass of In, 0.3 to 4.0% by mass of Ag, and 0 to 1.0% by mass. Bi and 0.054 to 9.0% by mass of Ga, and the balance is only 79.2% by mass or more of Sn.

  The mounting body of the present invention is characterized in that an electronic component having an Au component electrode and an electronic circuit board having a substrate electrode are joined by the solder material described above, and is mounted on the electronic circuit board after soldering. It is possible to provide a mounting body that can satisfy the thermal fatigue characteristics of the Au component electrode.

  Further, in the above-described solder joining method, an electronic component having an Au component electrode and an electronic circuit board having a substrate electrode are joined by the solder material described above. This makes it possible to satisfy the thermal fatigue characteristics of the Au component electrode mounted on the electronic circuit board after soldering.

  Further, the amount of Ga contained is desirably an amount corresponding to the amount of P contained in the Ni plating.

  Moreover, since the solder part formed using the solder material having the composition of Cu electrode and Sn—Ag—Bi—In—Ga does not form an intermetallic compound with Cu and Ga, thermal fatigue characteristics The degree of influence is considered to be small.

  FIG. 7 shows a schematic cross-sectional view of the mounting body according to the embodiment of the present invention. The mounting body 700 includes an electronic circuit board 730 having Cu substrate electrodes 731 and 732, an electronic component 720 having an Au component electrode 721 on the Cu substrate electrode 731, an electronic component 740 having a Cu component electrode 741 on the Cu substrate electrode 732, They are joined by solder portions 711 and 712 formed using a solder material having a composition of Sn—Ag—Bi—In—Ga. The mounting body 700 having such a configuration satisfies the required specifications for the reliability test of the in-vehicle product.

  Further, the Cu substrate electrodes 731 and 732 may be Au substrate electrodes.

  Moreover, the typical block diagram before and behind soldering of the solder part 711 and Cu board | substrate electrode 731 which were formed using the solder material which has the composition of Au component electrode 721 and Sn-Ag-Bi-In-Ga. As shown in FIG. The figure shown on the upper side of FIG. 8 shows the configuration before soldering, and the lower figure at the tip of the arrow shows after soldering. In the Au component electrode having Ni plating containing P, a GaP compound indicated by a small circle is generated on the solder portion after soldering. Generation of this GaP compound helps to prevent a decrease in the In content in the solder material.

  In addition, this time, Ga was added to the solder material having the Sn-Ag-Bi-In composition, but even if Co (cobalt) or Mo (molybdenum) is used in place of Ga, the inclusion of In in the solder material is possible. Helps prevent rate decline.

  The solder material and the mounting body in the present invention can satisfy thermal fatigue characteristics even in soldering to an Au component electrode, and are useful for use in, for example, a solder paste used for soldering an electronic circuit board. .

601 Liquid phase line 700 Mounting body 711, 712 Solder part 720, 740 Electronic component 721 Au component electrode 730 Electronic circuit board 731, 732 Cu substrate electrode 741 Cu component electrode

Claims (8)

5.6 to 6.8% by mass of In,
0.3-4.0 mass% Ag,
0.2 to 1.0 mass% Bi,
0.054 to 9.0% by mass of Ga,
The balance is only 79.2% by mass or more of Sn,
Solder material. 6.3 to 6.8% by mass of In,
2.3 to 3.7 mass% Ag,
0.3-1.0 mass% Bi;
Containing 1.0-5.0 mass% Ga,
The balance is only 83.5% by mass or more of Sn,
The solder material according to claim 1. It contains 2.0 to 9.0% by mass of Ga,
The solder material according to claim 1. It contains 3.0 to 9.0% by mass of Ga,
The solder material according to claim 1. 6.0 to 9.0% by mass of Ga,
The solder material according to claim 1. An electronic component having an Au component electrode and an electronic circuit board having a substrate electrode are joined by the solder material according to any one of claims 1 to 5 ,
Implementation body. The Au component electrode has Ni plating containing P,
The mounting body according to claim 6 . The substrate electrode is a Cu substrate electrode or an Au substrate electrode,
The mounting body according to claim 6 .

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