JP2013193092A - Solder material and mounting body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that a conventional solder material does not necessarily exhibit a sufficiently high thermal fatigue property in soldering an Au electrode which is subjected to Au flash plating by flash treatment for plating thinly in a short time.SOLUTION: A solder material is utilized in soldering an Au electrode including Ni plating containing P, and contains 3-8 mass% of In, 0.3-4.0 mass% of Ag, and 0.4-0.6 mass% of only one kind of component among Cr, Ni, Fe, Co, Zn, Si, Ge, Ga, and Al, wherein the balance is 87.4 mass% or more of Sn.

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.

  For soldering an electronic circuit board, a solder material having a composition of Sn—Ag—Bi—In composed of four kinds of elements is used (for example, see Patent Document 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.

  Sn-3.5mass% Ag-0.5mass% Bi-6mass% In, Sn-3.5mass% Ag-0.5mass% Bi-8mass% In and Sn-2.5mass depending on the difference in In content Compositions such as% Ag-2.5 mass% Bi-3 mass% In are utilized.

  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 an Au electrode that has been subjected to flash processing for performing Au flash plating in a short time, the above-described conventional solder material does not necessarily have sufficiently high thermal fatigue characteristics. There was found.

  The inventor analyzes the reason as follows.

  That is, in the solder material having the Sn—Ag—Bi—In composition described above, the thermal fatigue characteristics vary depending on the In content.

  The alloy strength related to thermal fatigue characteristics increases as the In content increases, but becomes maximum when the In content is approximately 6 mass%, and decreases when the In content exceeds this.

  That is, the thermal fatigue characteristics are the highest when the In content is about 6 mass%.

  Therefore, in order to effectively use the solid solution strengthening mechanism by In, it is desirable to control In content more accurately.

  By the way, in general, in an electronic circuit board, a Cu electrode whose electrode material is Cu is often used.

  In the combination of a Cu electrode and a solder material having a composition of Sn—Ag—Bi—In, Cu and In are not highly reactive, so they can be dissolved in the Sn lattice contributing to the improvement of thermal fatigue characteristics. The In content of In is not changed during soldering, and the state of high thermal fatigue characteristics is maintained.

  However, in consumer products such as mobile phones and smartphones, and in-vehicle products such as headlamps and ECUs (Electronic Control Units), high bonding reliability is required, so the aforementioned Au electrodes may be used. is there.

  In the combination of the Au electrode and the solder material having the Sn-Ag-Bi-In composition, as will be described in more detail below, the In content changes during soldering, and the thermal fatigue characteristics are reduced. May decrease.

  That is, for the Au 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. Have a structure.

  For this reason, Au melts into Sn-Ag-Bi-In during soldering with heating, and Ni plating is exposed.

  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 produce a compound InP having an In-P composition. .

  Then, the In dissolved in the Sn lattice contributes to the improvement of the thermal fatigue characteristics, and the substantial In content is greatly reduced as compared with the case of the Cu electrode. Will fall.

  For example, when the composition of Sn-3.5 mass% Ag-0.5 mass% Bi-6 mass% In changes to the composition of Sn-3.5 mass% Ag-0.5 mass% Bi-5.5 mass% In, the temperature cycle test The number of cycles in which electrical continuity can be ensured after the test conditions of -40 ° C / 150 ° C are reduced from 3360 cycles to 3040 cycles.

  In view of the above-described conventional problems, an object of the present invention is to provide a solder material and a mounting body that can maintain higher thermal fatigue characteristics even in soldering to an Au electrode.

1st this invention is a solder material utilized for soldering of Au electrode which has Ni plating containing P,
3-8 mass% In,
0.3 to 4.0 mass% Ag;
0.4 to 0.6 mass% of Cr, Ni, Fe, Co, Zn, Si, Ge, Ga and Al, and only one type of component,
The balance is a solder material characterized in that it is Sn of 87.4 mass% or more.

  According to a second aspect of the present invention, there is provided a mounting body in which an electronic component having an Au electrode and an electronic circuit board having a substrate electrode are joined by the solder material according to the first aspect of the present invention.

  According to the present invention, it is possible to provide a solder material and a mounting body capable of maintaining higher thermal fatigue characteristics even in soldering to an Au electrode.

The graph which shows the reliability test result of the alloy with the composition of Sn-3.5mass% Ag-0.5mass% Bi which added In for demonstrating the solder material of Embodiment 1 in this invention. 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 in each solder after soldering to an electrode was performed 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 to which Cr is added is used. The graph which shows the analysis result of In content in the solder after the soldering to the Au electrode is performed Solid line of an alloy having a composition of Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In to which Cr is added for explaining the solder material according to the first embodiment of the present invention And graph showing liquidus For explaining the solder material according to the second embodiment of the present invention, an alloy having a composition of Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In added with Zn is used. The graph which shows the analysis result of In content in the solder after the soldering to the Au electrode is performed Solid line of an alloy having a composition of Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In to which Zn is added for explaining the solder material according to the second embodiment of the present invention And graph showing liquidus Schematic sectional view of a mounting body according to an embodiment of the present invention

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

(Embodiment 1)
First, the principle of the first embodiment will be described with reference mainly to FIGS.

  FIG. 1 is a reliability test 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 result.

  Further, FIG. 2 uses an alloy having a composition of 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. FIG. 6 is a graph showing analysis results of In content in each solder after soldering to a Cu electrode and an Au electrode.

  First, the importance of the In content will be described with reference mainly to FIG.

  The In content of the horizontal axis is a substantial In content of In that is dissolved in the solder, 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). It is the number of cycles that can ensure electrical continuity after being carried out under test conditions of 40 ° C / 150 ° C.

  In the reliability test under in-vehicle conditions, the number of cycles of 3000 cycles or more is required in the required specifications.

  The number of cycles is 3000 cycles or more when the In content is 5.5 mass%, 6.0 mass%, and 6.5 mass%, but the In content is 5.0 mass% or less or 7.0 mass% or more. In some cases, it is less than 3000 cycles.

A quadratic function obtained by using an approximate curve using the above numerical data (Expression 1)
(Number of test cycles)
= −570.7 × (In content) ² + 6964 × (In content) -17926
It is illustrated as a graph.

  Therefore, the range of In content that can secure the number of cycles of 3000 cycles or more, which is the vehicle-mounted standard, is approximately 5.4 to 6.8 mass%, and the management width is approximately ± 0.7 mass%.

  Since the variation range of the In content of the solder alloy in mass production is approximately ± 0.5 mass%, the median value of the In content is 5.9 (= 5.4 + 0.5) mass% or more 6.3 ( = 6.8−0.5) mass% or less is desirable.

  In addition, the range of In content rate which can ensure the cycle number of 1000 cycles or more which is a consumer standard is about 3-8 mass%.

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

  The Au electrode is a Cu foil having a film thickness of 35 μm, and Ni plating having a film thickness of 1 to 5 μm is applied on the Cu electrode as electroless plating that does not require energization like electroplating, It has a structure in which Au flash plating having a film thickness of 0.03 to 0.07 μm is applied on Ni plating.

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

  Solder material having a composition of Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In is supplied on the Cu electrode and Au electrode in a shape of 5 mm in diameter and 0.15 mm in thickness, respectively. And heated on a hot plate at 240 ° C. for 30 seconds and slowly 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.

  The measured substantial In content of In dissolved in the Sn lattice contributing to the improvement of thermal fatigue properties has decreased from the initial In content of 6.0 mass%, It is 5.9 mass% for the Cu electrode, and a smaller 5.1 mass% for the Au electrode.

  As for 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.

  And 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 compared with that in the case of the Cu electrode. Will be greatly reduced.

  For this reason, since the range of In content corresponding to the vehicle-mounted standard is approximately 5.4 to 6.8 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.

  In light of such a phenomenon, the present inventor has found that the addition of an element that reacts more easily with P and forms a compound than In is effective for suppressing a decrease in In content. It was.

One of the many elements found as such is one that reacts with In, such as Cr ₃ P, Cr ₂ P, Cr ₁₂ P ₇ , CrP and CrP ₂ , described below. Cr, which produces a variety of compounds.

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

  FIG. 3 has a composition of Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In to which Cr is added to explain the solder material of the first embodiment of the present invention. It is a graph which shows the analysis result of the In content rate in the solder after soldering with respect to Au electrode was performed using the other alloy.

  FIG. 4 shows a composition of Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In to which Cr is added for explaining the solder material of the first embodiment of the present invention. It is a graph which shows the solidus line 401 and the liquidus line 402 of an alloy.

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

  Here, it is assumed that the Ni plating film thickness approaches the upper limit and the P content is maximum, and the thermal fatigue characteristics are not good from this viewpoint, so that the Ni plating film thickness is 5 μm. The prepared sample is analyzed by the same method as described above, and the In content after the soldering is measured.

  The sample is prepared as follows.

  89.5 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.

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

  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 mass% when the Cr content is zero. (2) When the Cr content is increased, the decrease in In is suppressed, 3) When the Cr content is 0.2 mass%, the mass is 5.5 mass%, and (4) When the Cr content is 0.4 mass%, the mass is approximately 6 mass%.

When an approximate straight line is drawn using numerical values when the Cr content is 0 mass% to 0.4 mass%, a linear function (Equation 2)
(In content)
= 2.11 x (Cr content) + 5.126
Is obtained.

  Therefore, in order to secure the In content of 5.4 mass% or more necessary for satisfying the vehicle-mounted standard even in combination with the Au electrode, the Cr content is preferably 0.1 mass% or more. If the Cr content is 0.1 mass% or more, the In content after soldering is 5.4 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 about ± 0.5 mass%, the In content may be slightly reduced for that reason.

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)
= 2.11 × (Cr content) +4.626
The In content is 4.9 (= 5.4-0.5) mass% when the Cr content is 0.1 mass%.

  Therefore, when the lower limit of the fluctuation range in mass production is taken into consideration, in order to secure an In content of 5.4 mass% or more, it is more desirable that the Cr content is 0.4 mass% or more with a slight margin.

  In the above description, the case where an alloy having a composition of Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In is used has been described. However, since In and Cr react at a certain ratio. The case where the In content is different can be handled in the same manner.

For example, in the case where an alloy having a composition of Sn-3.5 mass% Ag-0.5 mass% Bi-5.0 mass% In having an In content of 1 mass% is used, the approximate straight line is The graph of (2) received a downward movement corresponding to -1 mass% which is a decrease value of the In content (In content)
= 2.11 x (Cr content) + 4.126
This is a graph (shown by a one-dot chain line).

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

  That is, when the Cr content is too high, the liquidus temperature rises, so that the meltability is lowered and the wetting and spreading property tends to be deteriorated.

  More specifically, the solidus temperature represented by the solidus 401 is stable in the range of 210-220 ° C., but the liquidus temperature represented by the liquidus 402 is Cr When the content rate increases, the temperature rises. When the Cr content rate is 0.1 mass%, the temperature is 320 ° C, and when the Cr content rate is 0.4 mass%, the temperature is 540 ° C.

  Here, the solidus temperature is a temperature at which the alloy heated from the solid state starts to melt, and the liquidus temperature is a temperature at which all the alloy heated from the solid state finishes melting.

  Table 1 explains the relationship between the Cr content and the wetting spread when the Cr content is 0.1 mass%, 0.2 mass%,..., 1.0 mass%. (The same applies to the other tables, but the unit attached to the numerical data is mass%).

  Here, it is assumed that the Ni plating film thickness approaches the lower limit and the P content is minimum, and the wetting spreadability is not good from this viewpoint, so that the Ni plating film thickness is 1 μm. For the prepared sample, the wetting spread rate is measured by the spread test method defined in JIS Z 3197 “Flux test method for soldering”.

  Regarding the evaluation of the wetting spread, ◯ indicates that the wetting spread rate is 90% or more, Δ indicates that the wetting spread rate is 85% or more and less than 90%, and x indicates the wetting spread rate. Is less than 85%.

  Therefore, in order to guarantee a wetting spread rate of 90% or more which is important for good soldering, it is desirable that the Cr content is 0.6 mass% or less.

  Table 2 explains the relationship between various compositions and changes in In content for Examples 1a to 6a and Comparative Examples, and the reliability is determined.

  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 the In content, ○ indicates that the change in the In content is within ± 0.5 mass%, which is the fluctuation range of the In content in mass production, and × indicates the change in the In content is ± It indicates that it is not within 0.5 mass%.

  Regarding reliability determination, “◯” indicates that the criterion is satisfied, and “X” indicates that the criterion is not satisfied.

  In the comparative example, since an effective element is not added to suppress the decrease in the In content, the change in the In content is −0.9 mass%, and the determination for the change is ×.

  In short, in order to maintain higher thermal fatigue characteristics even when soldering to the Au electrode, it is desirable that the Cr content is 0.1 mass% or more and 0.6 mass% or less, considering the lower limit of the fluctuation range in mass production. In this case, the Cr content is more preferably 0.4 mass% or more and 0.6 mass% or less with a little margin.

  In Example 1a, 0.1 mass% of Cr is added, and the change in In content is −0.4 mass%. Since the amount is 3.6 mass%, the on-vehicle standard is not satisfied.

  In Example 6a, 0.3 mass% of Cr was added, and the change in In content was −0.3 mass%. Since the amount is 3.7 mass%, the on-vehicle standard is not satisfied.

  Next, Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% to which Ni, Fe, Co, Si, Ge and Al having similar properties, which are specific examples of elements other than Cr, are added. The case where an alloy having an In composition is used will be specifically described.

  In these cases, the sample is prepared in the same manner as in the case of Cr described above, and measurement and evaluation are performed in the same manner.

(When Ni is added)
In content rate is (5.4) mass% or less when (1) Ni content rate is zero, (2) When Ni content rate increases, the decrease of In is suppressed, (3) When the Ni content exceeds about 0.03 mass%, it becomes 5.4 mass% or more, and (4) when the Ni content becomes 0.12 mass%, it becomes about 6 mass%.

  When an approximate straight line is drawn as a graph of a linear function obtained by using the above numerical data, in order to secure an In content of 5.4 mass% or more that satisfies the reliability of the on-vehicle standard, 0.04 mass% or more It can be seen that the Ni content is desirable.

  However, as in the case of Cr, if the Ni content is too large, the liquidus temperature rises and the meltability decreases, and the wetting spreadability tends to deteriorate. It can be seen that a Ni content of 0.8 mass% or less is desirable to ensure.

  In short, in order to maintain higher thermal fatigue characteristics even in soldering to the Au electrode and satisfy the reliability of the on-vehicle standard, the Ni content is desirably 0.04 mass% or more and 0.8 mass% or less. It is more desirable that the content rate is 0.12 mass% or more and 0.8 mass% or less with a little margin.

(When Fe is added)
The In content is (5.4) mass% or less when the (1) Fe content is zero. (2) When the Fe content increases, the decrease in In is suppressed, (3) When the Fe content exceeds about 0.02 mass%, it becomes 5.4 mass% or more, and (4) when the Fe content becomes 0.08 mass%, it becomes about 6 mass%.

  When an approximate straight line is drawn as a graph of a linear function obtained by using the above numerical data, in order to secure an In content of 5.4 mass% or more that satisfies the reliability of the on-vehicle standard, 0.04 mass% or more It can be seen that the Fe content is desirable.

  However, as in the case of Cr, if the Fe content is too large, the liquidus temperature rises and the meltability decreases, and the wettability tends to deteriorate. It can be seen that an Fe content of 0.6 mass% or less is desirable to ensure.

  In short, it is desirable that the Fe content is 0.04 mass% or more and 0.6 mass% or less in order to maintain higher thermal fatigue characteristics even in soldering to the Au electrode and satisfy the reliability of the in-vehicle standard. It is more desirable that the content rate is 0.08 mass% or more and 0.6 mass% or less with a little margin.

(When Co is added)
In content rate is (5.4) mass% or less when (1) Co content rate is zero, but (2) When Co content rate increases, decrease of In is suppressed, (3) When the Co content exceeds about 0.03 mass%, it becomes 5.4 mass% or more, and (4) when the Co content becomes 0.18 mass%, it becomes about 6 mass%.

  When an approximate straight line is drawn as a graph of a linear function obtained by using the above numerical data, in order to ensure an In content of 5.4 mass% or more that satisfies the reliability of the vehicle-mounted standard, 0.05 mass% or more It can be seen that the Co content of is desirable.

  However, as in the case of Cr, if the Co content is too large, the liquidus temperature rises and the meltability decreases, and the wetting spreadability tends to deteriorate. It can be seen that a Co content of 1.1 mass% or less is desirable to ensure.

  In short, it is desirable that the Co content is 0.05 mass% or more and 1.1 mass% or less in order to maintain higher thermal fatigue characteristics even in soldering to the Au electrode and satisfy the reliability of the in-vehicle standard. It is more desirable that the content rate is 0.18 mass% or more and 1.1 mass% or less with a little margin.

(When Si is added)
The In content is (5.4) mass% or less when (1) the Si content is zero, but (2) when the Si content is increased, the decrease in In is suppressed. (3) When the Si content exceeds about 0.3 mass%, it becomes 5.4 mass% or more, and (4) when the Si content becomes 0.8 mass%, it becomes about 6 mass%.

  When an approximate straight line is drawn as a graph of a linear function obtained by using the above numerical data, in order to secure an In content of 5.4 mass% or more that satisfies the reliability of the on-vehicle standard, 0.2 mass% or more It can be seen that the Si content is desirable.

  However, as in the case of Cr, if the Si content is too large, the liquidus temperature rises and the meltability decreases, and the wetting spreadability tends to deteriorate. It can be seen that a Si content of 1.0 mass% or less is desirable to ensure.

  In short, in order to maintain higher thermal fatigue characteristics even in soldering to the Au electrode and satisfy the reliability of the in-vehicle standard, the Si content is desirably 0.2 mass% or more and 1.0 mass% or less. It is more desirable that the content rate is 0.8 mass% or more and 1.0 mass% or less with a little margin.

(When Ge is added)
The In content is (5.4) mass% or less when the (1) Ge content is zero, but (2) When the Ge content increases, the decrease in In is suppressed, (3) When the Ge content exceeds approximately 0.4 mass%, it is 5.4 mass% or more, and (4) when the Ge content is 1.1 mass%, it is approximately 6 mass%.

  When an approximate straight line is drawn as a graph of a linear function obtained by using the above numerical data, in order to secure an In content of 5.4 mass% or more that satisfies the reliability of the vehicle-mounted standard, 0.4 mass% or more It can be seen that the Ge content of is desirable.

  However, as in the case of Cr, if the Ge content is too high, the liquidus temperature rises and the meltability decreases, and the wettability tends to deteriorate. It can be seen that a Ge content of 1.9 mass% or less is desirable to ensure.

  In short, in order to maintain higher thermal fatigue characteristics even in soldering to the Au electrode and satisfy the reliability of the on-vehicle standard, the Ge content is desirably 0.4 mass% or more and 1.9 mass% or less. It is more desirable that the content rate is 1.1 mass% or more and 1.9 mass% or less with a little margin.

(When Al is added)
In content rate is (5.4) mass% or less when (1) Al content rate is zero, but (2) When Al content rate increases, decrease of In is suppressed, (3) When the Al content exceeds about 0.3 mass%, it becomes 5.4 mass% or more, and (4) when the Al content becomes 0.7 mass%, it becomes about 6 mass%.

  When an approximate straight line is drawn as a graph of a linear function obtained by using the above numerical data, in order to ensure an In content of 5.4 mass% or more that satisfies the reliability of the on-vehicle standard, 0.3 mass% or more It can be seen that the Al content of is desirable.

  However, as in the case of Cr, if the Al content is too large, the liquidus temperature rises and the meltability decreases, and the wettability tends to deteriorate. It can be seen that an Al content of 1.7 mass% or less is desirable to guarantee.

  In short, in order to maintain higher thermal fatigue characteristics even in soldering to the Au electrode and satisfy the reliability of the on-vehicle standard, the Al content is desirably 0.3 mass% or more and 1.7 mass% or less. It is more desirable that the content rate is 0.7 mass% or more and 1.7 mass% or less with a little margin.

  Of course, Cr, Ni, Fe, Co, Si, Ge, and Al may be added alone, but some of them may be added in combination.

  Table 3 explains the relationship between various compositions to which a plurality of types of elements are added and the change in In content for Examples 1b to 10b and Comparative Examples, and the reliability is determined.

  The remaining amount and determination regarding the change in In content, and the reliability determination are the same as those described above (see Table 2).

  In Example 1b, 0.2 mass% of Cr and 0.3 mass% of Si are added, and the change in In content is −0.1 mass%, and the determination about it is ○. Since the remaining amount with respect to the change in In content is 3.9 mass%, the on-vehicle standard is not satisfied.

  In Example 2b, 0.7 mass% Si and 0.3 mass% Al were added, and the change in In content was −0.1 mass%, and the determination about it was ○. Since the remaining amount with respect to the change in In content is 6.9 mass%, the on-vehicle standard is not satisfied.

  In Example 6b, 0.6 mass% Si and 0.7 mass% Ge were added, and the change in In content was −0.1 mass%, and the determination about it was “good”. Since the remaining amount with respect to the change in In content is 3.9 mass%, the on-vehicle standard is not satisfied.

  In Example 8b, 0.8 mass% Co and 0.8 mass% Ge were added, and the change in In content was -0.2 mass%, and the determination about it was o. Since the remaining amount with respect to the change in In content is 3.8 mass%, the on-vehicle standard is not satisfied.

  Further, in Example 10b, 0.2 mass% Ni and 0.4 mass% Si are added, and the change in In content is -0.1 mass%, and the determination about it is ○. Since the remaining amount with respect to the change in In content is 4.9 mass%, the on-vehicle standard is not satisfied.

(Embodiment 2)
Next, the solder material of the present embodiment will be specifically described with reference mainly to FIGS.

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

  Further, FIG. 6 has a composition of Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In to which Zn is added for explaining the solder material according to the second embodiment of the present invention. 5 is a graph showing a solid phase line 601 and a liquid phase line 602 of the alloy.

  The solder material of the present embodiment is similar to the solder material of the first embodiment described above, but in this embodiment, it is slightly different from the above-described Cr, Ni, Fe, Co, Si, Ge, and Al. Elements having properties are added.

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

  Sample preparation and analysis are performed by a method similar to the method in the first embodiment described above, and the In content after the soldering is measured.

  The In content is (1) 5.1 mass% when the Zn content is zero, but (2) When the Zn content increases, the decrease in In is suppressed, 3) When the Zn content is 0.2 mass%, it is 5.4 mass%, and (4) When the Zn content is 0.5 mass%, it is approximately 6 mass%.

When an approximate straight line is drawn using numerical values when the Zn content is 0 mass% to 0.5 mass%, a linear function (Equation 4)
(In content)
= 1.91 x (Zn content) + 5.079
Is obtained.

  Therefore, in order to secure the In content of 5.4 mass% or more necessary for satisfying the on-vehicle standard even in combination with the Au electrode, the Zn content is preferably 0.2 mass% or more.

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

  That is, if the Zn content is too high, the liquidus temperature is lowered, so that the primary surface in the double-sided mounting is easily remelted in the reflow process of the secondary surface, and bonding failure is likely to occur.

  More specifically, although the solidus temperature represented by the solidus 601 is stable in the range of 190 to 200 ° C., the liquidus temperature represented by the liquidus 602 is Zn When the content rate increases, it decreases, and when the Zn content rate is 4 mass%, it is 222 ° C, and when the Zn content rate is 8 mass%, it is 200 ° C.

  Table 4 explains the relationship between Zn content and remelting when the Zn content is 3.0 mass%, 3.5 mass%,..., 5.5 mass%, and evaluation of remelting is performed. ing.

  Here, an FR5 substrate having a substrate thickness of 0.8 mm is used, and a sample prepared so that a 1.0 mm pitch BGA (Ball Grid Array) is formed by soldering at a peak temperature of 250 ° C. The measurement of the void shape before and after reheating at a peak temperature of 250 ° C. is performed by a method by X-ray observation.

  Regarding the evaluation of remelting, ◯ indicates that the void shape has changed before and after reheating, and x indicates that the void shape has not changed.

  Of course, it is understood that such a change in void shape is caused by remelting.

  Therefore, in order to guarantee the suppression of remelting, which is important for good soldering, the Zn content is preferably 4.0 mass% or less.

  Table 5 explains the relationship between various compositions and changes in In content for Examples 1c to 6c and Comparative Examples, and the reliability is determined.

  The remaining amount and determination regarding the change in In content, and the reliability determination are the same as those described above (see Table 2).

  In Example 1c, 0.2 mass% of Zn was added, and the change in In content was -0.5 mass%. Since the amount is 3.5 mass%, the on-vehicle standard is not satisfied.

  Further, in Example 6c, 3.5 mass% of Zn was added, the In content rate change was -0.2 mass%, and the determination about that was ○, but the remaining In content rate change was Since the amount is 3.8 mass%, the on-vehicle standard is not satisfied.

  In short, in order to maintain higher thermal fatigue characteristics even in soldering to the Au electrode, it is desirable that the Zn content is 0.2 mass% or more and 4.0 mass% or less, and the Zn content is 0. It is more desirable to be 5 mass% or more and 4.0 mass% or less.

  Next, an alloy having a composition of Sn-3.5 mass% Ag-0.5 mass% Bi-6.0 mass% In to which Ga having similar properties, which is a specific example of an element other than Zn, is used. The case will be specifically described.

  Also in this case, the sample is prepared in the same manner as in the case of Zn described above, and measurement and evaluation are performed in the same manner.

(When Ga is added)
In content is (5.4) mass% or less when (1) Ga content is zero, (2) When Ga content is increased, the decrease in In is suppressed, (3) When the Ga content exceeds about 0.05 mass%, it becomes 5.4 mass% or more, and (4) When the Ga content becomes 0.5 mass%, the In content becomes about 6 mass%.

  When an approximate straight line is drawn as a graph of a linear function obtained by using the above numerical data, in order to ensure an In content of 5.4 mass% or more that satisfies the reliability of the vehicle-mounted standard, 0.05 mass% or more It can be seen that the Ga content is desirable.

  However, as in the case of Zn, if the Ga content is too high, the liquidus temperature is lowered and the primary surface in double-sided mounting is remelted in the reflow process of the secondary surface, which tends to cause poor bonding. Therefore, it can be seen that a Ga content of 4 mass% or less is desirable in order to guarantee suppression of remelting.

  In short, in order to maintain higher thermal fatigue characteristics even in soldering to the Au electrode and satisfy the reliability of the on-vehicle standard, the Ga content is desirably 0.05 mass% or more and 4.0 mass% or less. It is more desirable that the content is 0.5 mass% or more and 4.0 mass% or less with a little margin.

  As is clear from the above description, the solder material of the present invention is a solder material used for soldering an Au electrode having Ni plating containing P, and contains 3 to 8 mass% In and 0.3. -4.0 mass% Ag and 0.4-0.6 mass% of Cr, Ni, Fe, Co, Zn, Si, Ge, Ga and Al, and only one type of component, with the balance being , 87.4 mass% or more of Sn.

  Such a solder material desirably contains 0.2 to 1.0 mass% Bi.

  In addition, the amount of only one of the components Cr, Ni, Fe, Co, Zn, Si, Ge, Ga, and Al contained therein may be an amount corresponding to the amount of P included in the Ni plating. desirable.

  Further, when two or more kinds of components of Cr, Ni, Fe, Co, Zn, Si, Ge, Ga and Al are included, the total amount of these two or more kinds of components is P. It is desirable that the amount corresponds to the amount.

  In addition, an electronic component 720 having Au electrodes 721 and 722 and an electronic circuit having substrate electrodes 731 and 732 as shown in FIG. 7 which is a schematic cross-sectional view of the mounting body according to the embodiment of the present invention. A mounting body in which the substrate 730 is joined by the solder material is included in the present invention. The electronic component 720 and the electronic circuit board 730 are joined by solder portions 711 and 712 formed using the above-described solder material.

  The solder material and the mounting body in the present invention can maintain higher thermal fatigue characteristics even when soldering to an Au electrode, and for example, for use in solder paste used for soldering an electronic circuit board. Useful.

401 Solid phase line 402 Liquid phase line 601 Solid phase line 602 Liquid phase line 711, 712 Solder part 720 Electronic component 721, 722 Au electrode 730 Electronic circuit board 731, 732 Substrate electrode

Claims (2)

A solder material used for soldering an Au electrode having Ni plating containing P,
3-8 mass% In,
0.3 to 4.0 mass% Ag;
0.4 to 0.6 mass% of Cr, Ni, Fe, Co, Zn, Si, Ge, Ga and Al, and only one type of component,
The remainder is 87.4 mass% or more of Sn.   An electronic component having an Au electrode and an electronic circuit board having a substrate electrode are joined by the solder material according to claim 1.

Images