Solder alloy, solder paste, solder ball, preformed solder, and solder joint

Abstract

The invention provides a solder alloy, a solder paste, a solder ball, a preformed solder, and a solder joint, which have excellent drop impact resistance and thermal cycle resistance, are capable of suppressing the occurrence of chip erection and tin bonding and tin tips, and are also capable of suppressing the occurrence of electromigration. The solder alloy is composed of the following alloy components in percentage by mass: 0.3% to 1.9% of Ag, 0.40% to 1.00% of Cu, 0.5% to 4.9% of Bi, 0.00100% to 0.02000% of P and the balance of Sn. The alloy composition may also contain at least one of Ge, Co, and Ga in an amount of 0.06% by mass or less, respectively. In addition, the alloy composition may contain at least one of As, In, Zr, Mn, Ti, Zn, Fe, Al, Ni, Au, Mg, Cr, and Pt in an amount of 0.06% by mass or less, respectively.

Description

(19) State Intellectual Property Office (12) Invention Patent Application (10) Application Publication Number (43) Application Publication Date (21) Application Number 202511884417.3 (22) Application Date 2025.12.15 (30) Priority Data 2024-224522 2024.12.19 JP (71) Applicant Senju Metal Industries, Ltd. Address Japan (72) Inventors Takahiro Yokoyama, Shunsaku Yoshikawa, Takahiro Matsufuji (74) Patent Agency Beijing Linda Liu Intellectual Property Agency (General Partnership) 11277 Patent Attorneys Li Maojia, Li Enhua (51) Int.Cl. B23K 35 / 26 (2006.01) B23K 35 / 02 (2006.01) (54) Invention Title: Solder Alloy, Solder Paste, Solder Ball, Preformed Solder Alloy, and Brazed Joint (57) Abstract: This invention provides a solder alloy, solder paste, solder ball, preformed solder, and brazed joint, which have excellent resistance to drop impact and thermal cycling, can suppress chip stand-up and solder bridging / solder spikes, and can also suppress electromigration. The solder alloy has the following alloy composition by mass%: Ag: 0.3~1.9%, Cu: 0.40~1.00%, Bi: 0.5~4.9%, P: 0.00100~0.02000%, and the balance is Sn. The alloy composition may also contain at least one of Ge, Co, and Ga by mass% in amounts of less than 0.06%. In addition, the alloy composition may also contain at least one of As, In, Zr, Mn, Ti, Zn, Fe, Al, Ni, Au, Mg, Cr and Pt in an amount of less than 0.06% by mass. Claims 1 page, Description 12 pages, Drawings 1 page CN 122252858 A 2026.06.23 CN 1 22 25 28 58 A 1. A soft solder alloy, characterized in that it has the following alloy composition: Ag: 0.3~1.9%, Cu: 0.40~1.00%, Bi: 0.5~4.9%, P: 0.00100~0.02000% by mass, and the balance being Sn. 2. The soft solder alloy according to claim 1, wherein the alloy composition further contains Ga in an amount of less than 0.06% by mass. 3. The solder alloy according to claim 1 or 2, wherein the alloy composition further contains at least one of As, In, Zr, Mn, Ti, Zn, Fe, Al, Au, Mg and Pt in an amount of less than 0.06% by mass.4. The solder alloy according to claim 1 or 2, wherein the alloy composition satisfies all of the following formulas (1) to (3): 0.0007≤Ag×Cu×Bi×P≤0.0110 (1) 110≤Ag / (P×Cu)≤799 (2) 0.67≤(Ag+Bi) / (Ag+Cu+Bi)≤0.91 (3) In formulas (1) to (3), Ag, Cu, Bi and P respectively represent the content of the alloy composition in terms of mass%. 5. The solder alloy according to claim 3, wherein the alloy composition satisfies all of the following formulas (1) to (3): 0.0007≤Ag×Cu×Bi×P≤0.0110 (1) 110≤Ag / (P×Cu)≤799 (2) 0.67≤(Ag+Bi) / (Ag+Cu+Bi)≤0.91 (3) In formulas (1) to (3), Ag, Cu, Bi and P respectively represent the content of the alloy composition in terms of mass%. 6. A solder paste having solder powder composed of the solder alloy according to claim 1 or 2. 7. A solder paste having solder powder composed of the solder alloy according to claim 3. 8. A solder ball composed of the solder alloy according to claim 1 or 2. 9. A solder ball composed of the solder alloy according to claim 3. 10. A preformed solder, comprising the solder alloy of claim 1 or 2. 11. A preformed solder, comprising the solder alloy of claim 3. 12. A brazing joint having the solder alloy of claim 1 or 2. 13. A brazing joint having the solder alloy of claim 3. Claims 1 / 1 page 2 CN 122252858 A Solder alloy, solder paste, solder ball, preformed solder and brazing joint Technical Field

[0001] This invention relates to Sn-Ag-Cu-Bi-P solder alloy. Background Art

[0002] In household appliances such as washing machines, refrigerators, and air conditioners, and electronic devices such as televisions, video recorders, radios, computers, copiers, and communication equipment, mounting substrates carrying electronic components are used. In addition to single-layer substrates, mounting substrates are also used to achieve full functionality by stacking multiple substrates.

[0003] In the conduction between substrates and the mounting of electronic components onto substrates, methods such as surface mounting and mounting by inserting terminals into through-holes in the substrate can be cited. Examples of such mounting processes for printed circuit boards include wave soldering, reflow soldering, and manual soldering. Among these, wave soldering is typically used for mounting electronic components of a certain size.

[0004] For example, Patent Document 1 describes a study on forming brazed joints using wave soldering.The Sn-Ag-Cu-Bi-P solder alloy described in this document can suppress the formation of dross, improve volumetric strength (tensile strength) by forming intermetallic compounds from Ag, and improve wettability through P. Patent Document 2 investigated the tensile strength, wettability during wave soldering, solidus temperature, liquidus temperature, and number of bridging events of the Sn-Ag-Cu-Bi-P solder alloy.

[0005] Furthermore, Sn-Ag-Cu-Bi-P solder alloys not limited to wave soldering were investigated. Patent Document 3 disclosed a Sn-Ag-Cu-Bi-P solder alloy for paste solders or cored solders, achieving improvements in tensile strength, elongation, and thermal fatigue resistance. Patent Document 4 disclosed a Sn-Ag-Cu-Bi-P solder alloy for solder balls, investigating its impact resistance, yellowing, and thermal cycling resistance.

[0006] Patent Document 5 discloses a Sn-Ag-Cu-Bi solder alloy whose thermal cycling resistance was studied using a mounting substrate printed with solder paste. Patent Document 6 discloses a Sn-Ag-Cu-Bi-P solder alloy for piping connection and sealing, in which the liquidus temperature and solidus temperature were evaluated.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2007-7732

[0010] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2000-288772

[0011] Patent Document 3: Japanese Unexamined Patent Application Publication No. 10-34376

[0012] Patent Document 4: Japanese Unexamined Patent Application Publication No. 2004-261863

[0013] Patent Document 5: Japanese Unexamined Patent Application Publication No. 2011-183430

[0014] Patent Document 6: Japanese Unexamined Patent Application Publication No. 2-70033 Summary of the Invention

[0015] Problems to be Solved by the Invention

[0016] Sn-Ag-Cu-Bi-P solder alloys have been recognized to have various effects. The invention described in Patent Document 1 is an excellent invention exhibiting superior wettability and high tensile strength. In paragraph 0008 of Patent Document 1, as prior art, it is explained that when the cost is reduced by decreasing the content of expensive Ag, the tensile strength of the solder alloy is poor. Specification 1 / 12 pages 3 CN 122252858 A

[0017] In fact, according to the research results in paragraph 0027 of Patent Document 1, the tensile strength of Example 7, with an Ag content of 2% by mass, increased by approximately two times compared to Example 4, with an Ag content of 0.3% by mass. This is believed to be because, as described in paragraph 0020 of Patent Document 1, Ag and Sn form an intermetallic compound. Therefore, it can be understood that, according to the invention described in Patent Document 1, increasing the Ag content is preferable to improve tensile strength.

[0018] The invention described in Patent Document 2 also included a study on tensile strength, disclosing that the Ag content was 2.0 to 5.0% by mass. In paragraph 0008 of Patent Document 2, it was disclosed that when the Ag content was less than 2.0% by mass, the elongation decreased significantly due to the addition of Bi, failing to meet the characteristics required for a solder material. That is, the invention described in Patent Document 2 reflects the prior art described in Patent Document 1, and according to the invention described in Patent Document 2, the Ag content needs to be increased to 2.0% by mass or more. Furthermore, in the invention described in Patent Document 2, the contents of P and Ni were studied to suppress bridging.

[0019] In the invention described in Patent Document 3, in addition to tensile strength and elongation, thermal cycling resistance was also studied. In Patent Document 3, to avoid a decrease in tensile strength, only solder alloys with an Ag content of 2.0% or more were disclosed in the embodiments. That is, the invention described in Patent Document 3 reflects the content described and confirmed in Patent Documents 1 and 2.

[0020] In Patent Document 4, a solder alloy in which Ni is added to Sn-Ag-Cu-Bi-P is disclosed in the embodiments. The solder alloy described in Patent Document 4 is different from that in Patent Documents 1 to 3. Instead of studying tensile strength, it studies impact resistance. The content of Ag in the solder alloy composed of Sn-Ag-Cu-Bi-P-Ni disclosed in the embodiments is suppressed to a low level.

[0021] In the invention described in Patent Document 4, drop impact resistance was studied as described above. According to Patent Document 4, in order to improve drop impact resistance, the content of Cu needs to be suppressed to below 0.3% by mass. In detail, paragraph 0018 of Patent Document 4 states that if the content of Cu is below 0.3% by mass, the effect of suppressing intermetallic compounds is stronger than the increase of voids, resulting in better drop impact resistance. Thus, in the invention described in Patent Document 4, the Cu content is kept low in order to improve drop impact resistance.

[0022] In the invention described in Patent Document 5, the joint strength after thermal shock test was studied as a study of thermal cycling resistance. In Patent Document 5, Sn-Ag-Cu-Bi soft solder alloy is disclosed as a specific alloy composition. In paragraph 0015 of Patent Document 5, it is stated that in order to improve thermal cycling resistance, instead of using a soft solder alloy that is as soft as possible, the tensile strength of the soft solder alloy that is helpful in improving the joint strength of the brazed joint after the thermal shock test is increased, thereby improving the thermal stress resistance of the brazed joint.

[0023] Furthermore, paragraph 0010 of Patent Document 5 states that P may be contained as an element equivalent to Ge, Ga, and In. However, the content of these elements is not mentioned in Patent Document 5.In paragraph 0012 of Patent Document 5, the content of Ge, Ga, and In is specifically disclosed to be in the range of 0.05 to 1.0% by mass. Therefore, even when P is added to the solder alloy of Patent Document 5, the content of P must be in the range of 0.05 to 1.0% by mass.

[0024] In Patent Document 6, Sn-Ag-Cu-Bi-P is disclosed as a solder alloy for piping connection and sealing. Moreover, for such use, the content of Ag is preferably 0.1 to 0.4% by mass. In the alloy composition actually studied as an example in Patent Document 6, the content of Ag is 0.4% by mass or less. It is presumed that this is because, especially for use as a sealing material, the elongation of the solder alloy needs to be considered, and therefore the tensile strength is deliberately reduced.

[0025] However, in the inventions described in Patent Documents 1 to 6, it is necessary to consider the actual situation of electronic devices that have made significant progress in recent years. In particular, as issues of concern, chip lifting that may occur during the installation of electronic components and electromigration that may occur during operation can be listed.

[0026] Chip lifting is a phenomenon in which, when the solder alloy placed on the electrodes melts by heating, the solder alloy on one electrode (page 2 / 12, CN 122252858 A) begins to melt earlier than the solder alloy on the other electrode, and electronic components such as chips are pulled towards one electrode and tilted up. This is accompanied by the recent trend of thinner and smaller electronic devices, and the electronic components mounted on electronic devices are also developing towards miniaturization and lightweighting, thus chip lifting occurs frequently.

[0027] Regarding electromigration, with the advancement of miniaturization of electronic components, the current density increases when energized, and the number of electrons moving within the solder joint also increases. Therefore, the problem has gradually become more apparent in recent years. Electromigration can be explained as follows. The atoms constituting the solder joint collide with the electrons that generate the current, and momentum is transferred from the electrons to the atoms. The atoms that have gained momentum from the electron flow move to the anode side of the solder joint along with the electron flow. At this time, in the Cu-containing solder alloy, Cu segregates towards the anode side, generating vacancies on the cathode side of the solder joint. These vacancies gradually expand to form voids. As the voids grow, the resistance increases, the solder joint heats up due to Joule heating, or the electronic component's performance is hampered by a decrease in current density. Eventually, the solder joint breaks.

[0028] Thus, in recent years, there has been a search for solder alloys in Sn-Ag-Cu-Bi-P solder alloys that can suppress chip stand-up and electromigration while maintaining the previous properties. Therefore, it is urgent to study the solder alloys described in Patent Documents 1 to 6 in light of the actual situation of electronic components in recent years.

[0029] The objective of this invention is to provide a solder alloy, solder paste, solder balls, preformed solder, and solder joints that have excellent resistance to drop impact and thermal cycling, can suppress chip stand-up and the formation of solder bridging and solder spikes, and can also suppress electromigration.

[0030] Solution to the Problem

[0031] The inventors extracted a Sn-Ag-Cu-Bi-P solder alloy that is believed to be able to solve the above-mentioned problems from the Sn-Ag-Cu-Bi-P solder alloys specifically studied in Patent Documents 1 to 6, and conducted detailed research on it. First, we selected Sn-2Ag-0.5Cu-2Bi-0.005P from Example 7 of Patent Document 1, which utilizes Ag3Sn for precipitation enhancement; Sn-2.8Ag-0.5Cu-1.0Bi-0.005P-0.005Ni from the examples in Table 2 of Patent Document 2; Sn-2.8Ag-0.5Cu-1.0Bi-0.01P from the comparative examples in Table 2 of Patent Document 2; Sn-2Ag-0.5Cu-5Bi-0.003P from Comparative Example 2 of Patent Document 3; and Sn-2Ag-0.5Cu-5Bi-0.001P-0.005Ni from Example 1 of Patent Document 3. It should be noted that in the examples and comparative examples extracted from Patent Documents 1 to 6, when the element content is expressed as an integer, the first decimal place is considered as 0. The same applies below.

[0032] Next, in order to improve the drop impact resistance, Sn-1Ag-0.05Cu-1Bi-0.005P-0.05Ni from Patent Document 4, Example 11, where the Cu content was suppressed, was selected. Additionally, Sn-1.0Ag-0.5Cu-1.0Bi from Patent Document 5, Comparative Example 2, and Sn-0.2Ag-0.2Cu-3.8Bi from Patent Document 6 No. 3, which have low Ag content and are presumed to improve drop impact resistance, were selected.

[0033] First, Example 7 of Patent Document 1, Comparative Example 2 of Patent Document 3, and Example 1, etc., have a high Ag content, thus resulting in poor drop impact resistance. The examples and comparative examples of Patent Document 2, both with even higher Ag content, have resulted in more chip stand-up in addition to drop impact resistance.

[0034] Example 11 of Patent Document 4 has a low Cu content, thus resulting in poor thermal cycling resistance. Compared with Comparative Example 2 of Patent Document 5 and Example 7 of Patent Document 1, although the drop impact resistance is slightly improved, the absence of P results in the observation that bridging and / or solder spikes are more frequent. Patent Document No. 3 of Patent Document 6 shows poor thermal cycling resistance due to its low Ag content.

[0035] Furthermore, in addition to the above-mentioned observations, the aforementioned solder alloys disclosed in Patent Documents 2 and 6 also show the observation that chip stand-up is more frequent.Furthermore, insights into electromigration occurring in the aforementioned solder alloys disclosed in Patent Documents 4 and 6 were also obtained.

[0036] In view of the above insights, it is believed that it is not sufficient to simply increase the Ag content to precipitate a large amount of Ag3Sn, but rather that the solder alloy needs to be prepared to achieve a moderate hardness to improve drop impact resistance and / or thermal cycling resistance. In addition, it is believed that it is necessary to prepare the solder alloy such that two large endothermic alloy compositions can be observed during the thermal history measurement using DSC (Differential Scanning Calorimeter) in a temperature region higher than the solidus temperature when the solder alloy is heated, thus suppressing chip stand-up. Furthermore, it is also believed that it is necessary to suppress bridging and / or solder spike formation by adjusting the viscosity of the molten solder. In addition, it is believed that it is necessary to improve electromigration resistance (hereinafter referred to as "EM resistance") through moderate Ag3Sn precipitation and / or solid solution strengthening of the solder alloy brought about by Bi.

[0037] Here, the effect of the solder alloy is not that the effects brought by each constituent element are exerted separately, but rather that the effects are exerted synergistically as a whole. Therefore, it is impossible for a single composition to exert various effects simultaneously by separately adjusting each constituent element in order to improve each characteristic.

[0038] Therefore, in view of the above-mentioned insights, the inventors conducted a detailed exploration of the composition of Sn-Ag-Cu-Bi-P solder alloy. As a result, a solder alloy with excellent resistance to drop impact and thermal cycling, capable of suppressing chip stand-up and the generation of solder bridging and solder spikes, and also capable of suppressing electromigration was obtained, thus completing the present invention.

[0039] The present invention obtained based on this insight is as follows.

[0040] (0) A solder alloy, characterized in that, by mass%, it comprises Ag: 0.3~1.9%, Cu: 0.40~1.00%, Bi: 0.5~4.9%, P: 0.00100~0.02000%, and the balance is Sn.

[0041] (1) A solder alloy, characterized in that it has the following alloy composition: by mass%, it comprises Ag: 0.3~1.9%, Cu: 0.40~1.00%, Bi: 0.5~4.9%, P: 0.00100~0.02000%, and the balance is Sn.

[0042] (2) The solder alloy according to (0) or (1) above, wherein the alloy composition further comprises at least one of Ge, Co and Ga in an amount of 0.06% or less by mass%.

[0043] (3) The solder alloy according to any one of (0) to (2) above, wherein the alloy composition further contains at least one of As, In, Zr, Mn, Ti, Zn, Fe, Al, Au, Mg, Cr and Pt in an amount of 0.06% or less by mass.

[0044] (4) The solder alloy according to any one of (0) to (2) above, wherein the alloy composition further contains at least one of As, In, Zr, Mn, Ti, Zn, Fe, Al, Ni, Au, Mg, Cr and Pt in an amount of 0.06% or less by mass.

[0045] (5~6) A solder alloy according to any one of (0) to (4) above, wherein the alloy composition satisfies all of the following formulas (1) to (3):

[0046] 0.0007≤Ag×Cu×Bi×P≤0.0110 (1) formula

[0047] 110≤Ag / (P×Cu)≤799 (2) formula

[0048] 0.67≤(Ag+Bi) / (Ag+Cu+Bi)≤0.91 (3) formula

[0049] In formulas (1) to (3) above, Ag, Cu, Bi and P respectively represent the content in the alloy composition by mass%.

[0050] (7~8) A solder paste having solder powder composed of a solder alloy according to any one of (0) to (6) above.

[0051] (9~10) A solder ball composed of any one of the solder alloys described in (0) to (6) above.

[0052] (11~12) A preformed solder alloy composed of any one of the solder alloys described in (0) to (6) above.

[0053] (13~14) A brazed joint having any one of the solder alloys described in (0) to (6) above. Brief Description of the Drawings

[0054] FIG1 is a cross-sectional SEM photograph of the brazed joint, FIG1(a) is Comparative Example 1, and FIG1(b) is Example 22. Specification 4 / 12 pages 6 CN 122252858 A Detailed Description of the Embodiments

[0055] The present invention will be described in more detail below. In this specification, unless otherwise specified, “%” related to the alloy composition of the solder alloy means “mass %”.

[0056] 1. Solder alloy

[0057] (1) Ag: 0.3~1.9%

[0058] Ag is an element that improves drop impact resistance, thermal cycling resistance, and EM resistance, and suppresses chip stand-up. Ag can suppress the deformation of the solder alloy through Ag3Sn precipitation strengthening, thus contributing to the improvement of thermal cycling resistance and drop impact resistance. In addition, due to the precipitation of Ag3Sn, the movement of electrons is hindered, and the EM resistance is improved. Furthermore, in the thermal history using DSC, two large endothermic peaks are shown between the solidus temperature and the liquidus temperature during heating.

[0059] When the Ag content is less than 0.3%, the amount of Ag3Sn precipitated is insufficient, resulting in deterioration of heat cycle resistance and EM resistance. Furthermore, chip standing up is more frequent. The lower limit of the Ag content is 0.3% or more, preferably 0.4% or more, more preferably 0.5% or more, and even more preferably 0.6% or more.

[0060] On the other hand, when the Ag content exceeds 1.9%, Ag3Sn forms a network, thus deteriorating its resistance to drop impact. Additionally, when the Ag content reaches 2.5% or more, the endothermic peak becomes a single peak, leading to more chip standing up. The upper limit of the Ag content is 1.9% or less, preferably 1.7% or less, more preferably 1.6% or less, even more preferably 1.4% or less, even more preferably 1.3% or less, particularly preferably 1.2% or less, and most preferably 1.1% or less.

[0061] The preferred range of Ag content is 0.6% to 1.4%. The above upper and lower limits can define a more preferred range of Ag content.

[0062] (2) Cu: 0.40~1.00%

[0063] Cu is an element that improves thermal cycling resistance, EM resistance, and suppresses the formation of bridging and / or tin spikes. Cu6Sn5 formed by Cu and Sn is finely precipitated at the bonding interface, so the bonding interface will not break even when subjected to thermal stress caused by temperature difference. In addition, if the Cu content is 0.40~1.00%, it is close to the eutectic composition of Sn and Cu, and the rise of liquidus temperature is suppressed, so the formation of bridging and / or tin spikes can be suppressed. Furthermore, the intermetallic compound formed by Cu and Sn hinders the movement of electrons, so the EM resistance is improved.

[0064] When the Cu content is less than 0.40%, the amount of fine Cu6Sn5 precipitation is insufficient, and the thermal cycling resistance and EM resistance deteriorate. The lower limit of the Cu content is 0.40% or more, preferably 0.50% or more.

[0065] On the other hand, when the Cu content exceeds 1.00%, the liquidus temperature will rise, and the viscosity of the molten solder will increase when bonding at normal temperatures, thus causing more bridging and / or solder spikes. The upper limit of the Cu content is 1.0% or less, preferably 0.90% or less, more preferably 0.80% or less, further preferably 0.70% or less, and even more preferably 0.60% or less.

[0066] The preferred range of Cu is 0.40 to 0.70%. The above upper and lower limits can define a more preferred range of Cu content.

[0067] (3) Bi: 0.5 to 4.9%

[0068] Bi is an element that helps to improve the resistance to drop impact and EM resistance. Since Bi is dissolved in Sn, the solid solution strengthening of Sn and the lattice deformation of Sn hinder the movement of Cu, thereby improving the EM resistance.

[0069] When the Bi content is less than 0.5%, the solid solution strengthening of Sn becomes insufficient, and the EM resistance deteriorates.The lower limit of the Bi content is 0.5% or more, preferably 0.6% or more, more preferably 0.7% or more, further preferably 0.8% or more, particularly preferably 0.9% or more, and most preferably 1.0% or more.

[0070] On the other hand, when the Bi content exceeds 4.9%, the Bi content exceeds the solid solution limit of Bi, and therefore Bi segregates. Due to the hardening and / or embrittlement of the solder alloy, the drop impact resistance is poor. The upper limit of the Bi content is 4.9% or less, preferably 3.7% or less, more preferably 2.9% or less, further preferably 2.0% or less, even more preferably 1.9% or less, particularly preferably 1.5% or less, and most preferably 1.1% or less.

[0071] The preferred range of Bi is 0.5% to 3.7%. The above upper and lower limits can define a more preferred range of Bi content.

[0072] (4) P: 0.00100~0.02000%

[0073] P is an element that suppresses the formation of tin bridging and / or tin spikes. P remains on the surface of the molten solder and hinders the formation of tin oxide, thus appropriately maintaining the fluidity of the molten solder. Therefore, it is possible to suppress the formation of tin bridging and / or tin spikes that may occur during solidification.

[0074] When the content of P is less than 0.00100%, the formation of tin oxide cannot be suppressed, and tin bridging and / or tin spikes occur frequently. The lower limit of the content of P is 0.00100% or more, preferably 0.00200% or more, and more preferably 0.00300% or more.

[0075] On the other hand, when the content of P exceeds 0.0200%, intermetallic compounds of P will precipitate, and thus tin bridging and / or tin spikes occur frequently. The upper limit of the P content is 0.0200% or less, preferably 0.0170% or less, more preferably 0.0160% or less, further preferably 0.0150% or less, even more preferably 0.0110% or less, particularly preferably 0.00900% or less, and most preferably 0.00600% or less or 0.00400% or less.

[0076] The preferred range of P is 0.00300 to 0.0200%. The above upper and lower limits can define a more preferred range of the P content.

[0077] (5) Ge, Co and Ga are each in amounts of 0.06% or less, and at least one of them

[0078] In order to suppress the oxidation of the solder alloy, the solder alloy of the present invention may contain Ge, Co and Ga as arbitrary elements. If the content of the solder alloy containing these elements is 0.06% or less, the rise of the liquidus temperature can be suppressed, and thus the formation of bridging and / or tin spikes can be further suppressed. The content of each ingredient is preferably 0.006% or less, more preferably 0.005% or less. There is no particular limitation on the lower limit value, which can be 0.001% or more.Furthermore, if a composition contains at least one of these arbitrary elements, the total amount is 0.1% or less. The lower limit of the total amount is 0.001% or more.

[0079] (6) As, In, Zr, Mn, Ti, Zn, Fe, Al, Ni, Au, Mg, Cr and Pt are each in an amount of 0.06% or less, and at least one of them

[0080] The soft solder alloy of the present invention may contain at least one of As, In, Zr, Mn, Ti, Zn, Fe, Al, Ni, Au, Mg, Cr and Pt as arbitrary elements within a range that does not impair the above effects. The alloy composition may also contain As, In, Zr, Mn, Ti, Zn, Fe, Al, Ni, Au, Mg, Cr and Pt in an amount of 0.06% or less by mass. Among these arbitrary elements, it is further preferred to be the element group after removing Ni, an element whose melting point increases sharply by a small amount, from the above arbitrary elements. In detail, the alloy composition may also contain at least one of As, In, Zr, Mn, Ti, Zn, Fe, Al, Au, Mg, Cr, and Pt in amounts of 0.06% or less by mass%.

[0081] When the alloy composition contains at least one of As, In, Zr, Mn, Ti, Zn, Fe, Al, Ni, Au, Mg, Cr, and Pt, the upper limit of the content of each constituent element is preferably 0.06% or less. The lower limit is not particularly limited and is 0.001% or more. In addition, when a composition contains at least one of multiple of these arbitrary elements, the total amount is 0.1% or less. The lower limit of the total amount is 0.001% or more.

[0082] (7) (1)~(3)

[0083] 0.0007≤Ag×Cu×Bi×P≤0.0110 (1)

[0084] 110≤Ag / (P×Cu)≤799 (2)

[0085] 0.67≤(Ag+Bi) / (Ag+Cu+Bi)≤0.91 (3)

[0086] In the above (1)~(3) formulas, Ag, Cu, Bi and P respectively represent the content in the alloy composition by mass%.

[0087] The constituent elements of the soft solder alloy of the present invention have excellent resistance to drop impact and thermal cycling, and can suppress the generation of chip stand-up and tin bridging and tin spikes, and can also suppress the generation of electromigration. In order for a single component to simultaneously achieve these effects at a higher level, in addition to the content of each constituent element being within the above-mentioned range, it is further preferred to satisfy equations (1) to (3). The technical significance of each equation is as follows.

[0088] Equation (1) is a relationship based on the balance of the content of the essential elements.Equation (2) is a relationship between the contents of Ag, Cu, and P, which are elements capable of forming intermetallic compounds in the solder alloy of the present invention. The intermetallic compounds may affect various properties of the present invention depending on their precipitation location, morphology, size, etc. Therefore, if the solder alloy satisfies equation (2), a single component can exert a particularly excellent effect. Equation (3) consists of elements that improve the strengthening of the solder alloy of the present invention. Ag and Bi are elements that contribute to resistance to drop impacts. Ag, Cu, and Bi are elements that contribute to resistance to EM and / or thermal cycling. To achieve a balanced improvement in all properties to a high level, it is preferable to satisfy equation (3).

[0089] The upper limit of formula (1) is preferably 0.0110 or less, more preferably 0.0094 or less, even more preferably 0.0088 or less, even more preferably 0.0083 or less, particularly preferably 0.0081 or less, and most preferably selected from 0.0061 or less, 0.0050 or less, 0.0048 or less, 0.0033 or less, and 0.0031 or less. The lower limit of formula (1) is preferably 0.0007 or more, more preferably 0.0009 or more, further preferably 0.0010 or more, even more preferably 0.0011 or more, particularly preferably 0.0013 or more, and most preferably selected from 0.0014 or more, 0.0015 or more, 0.0017 or more, 0.0018 or more, 0.0020 or more, 0.0021 or more, 0.0022 or more, 0.0023 or more, 0.0025 or more, 0.0026 or more, and 0.0029 or more.

[0090] A further preferred range of formula (1) is 0.0017 to 0.0088. The above upper and lower limits can respectively define the more preferred range of formula (1).

[0091] The upper limit of formula (2) is preferably 799 or less, more preferably 733 or less, further preferably 611 or less, even more preferably 600 or less, particularly preferably 550 or less, and most preferably 524 or less, 458 or less, or 400 or less. The lower limit of formula (2) is preferably 110 or more, more preferably 129 or more, further preferably 138 or more, even more preferably 147 or more, particularly preferably 200 or more, and most preferably 244 or more, 267 or more, or 367 or more.

[0092] The further preferred range of formula (2) is 138 to 733. The above upper and lower limits can respectively define the more preferred range of formula (2).

[0093] The upper limit of formula (3) is preferably 0.91 or less, more preferably 0.89 or less, further preferably 0.86 or less, even more preferably 0.85 or less, particularly preferably 0.84 or less, and most preferably 0.83 or less or 0.81 or less.The lower limit of formula (3) is preferably 0.67 or higher, more preferably 0.68 or higher, even more preferably 0.72 or higher, even more preferably 0.74 or higher, particularly preferably 0.75 or higher, and most preferably selected from 0.76 or higher, 0.77 or higher, 0.78 or higher, 0.79 or higher, and 0.80 or higher.

[0094] The further preferred range of formula (3) is 0.76 to 0.89. The above upper and lower limits can respectively define the more preferred range of formula (1).

[0095] In the calculation of formulas (1) to (3), the values ​​shown in Tables 1 and 2, which are measured values ​​of alloy composition, are used. Regarding the values ​​calculated by formulas (1) to (3), formula (1) is calculated to the 4th decimal place, formula (2) is calculated to the 1st integer place, and formula (3) is calculated to the 2nd decimal place. This calculation rule is used in this application. In addition, all solder alloys must be processed in the same way, and therefore it is also intended to be used in calculations involving more solder alloys described in other documents, etc.

[0096] (8) Balance: Sn

[0097] The balance of the solder alloy of the present invention is Sn. In addition to the above-mentioned elements, it may contain unavoidable impurities. Even if unavoidable impurities are contained, the above-mentioned effects will not be affected. In addition, as will be said later, even if elements not contained in the present invention are contained as unavoidable impurities, the above-mentioned effects will not be affected.

[0098] 2. Solder paste

[0099] The solder paste of the present invention is a mixture of solder powder composed of the above-mentioned alloy composition and flux. The flux used in the specification of the present invention, page 7 / 12, CN 122252858 A, is not particularly limited as long as it can be soldered by conventional methods. Therefore, a substance that is appropriately mixed with commonly used rosin, organic acid, activator and solvent can be used. In this invention, the mixing ratio of the metal powder component and the flux component is not particularly limited, but preferably the metal powder component is 70-90% by mass and the flux component is 10-30% by mass.

[0100] 3. Solder Balls

[0101] The solder alloy of this invention can be used as solder balls. When used as solder balls, the solder alloy of this invention can be manufactured by the drop-addition method, which is a conventional method in the art. Alternatively, the brazed joint can be manufactured by processing the solder balls on an electrode printed with flux and joining them, which is a conventional method in the art. The particle size of the solder balls is preferably 1 μm or more, more preferably 10 μm or more, further preferably 20 μm or more, and particularly preferably 30 μm or more. The upper limit of the particle size of the solder balls is preferably 3000 μm or less, more preferably 1000 μm or less, further preferably 800 μm or less, and particularly preferably 600 μm or less.

[0102] 4. Preformed solder

[0103] The solder alloy of the present invention can be used as a preform.Examples of preform shapes include washers, rings, granules, discs, strips, and wires. They can also be used as solder bars.

[0104] 5. Brazing Joints

[0105] The brazing joints of the present invention are suitable for joining at least two or more components. There are no particular limitations on the components to be joined, such as semiconductors, power modules, inverter products, etc., which use the soft solder alloy of the present invention for electrical connection, including components such as elements, substrates, electronic components, printed circuit boards, insulating substrates, heat sinks, lead frames, and electrode terminals.

[0106] The joining method using the soft solder alloy of the present invention can be performed, for example, using reflow soldering as a conventional method. The melting temperature of the soft solder alloy during wave soldering can be approximately 20°C higher than the liquidus temperature. Furthermore, when joining using the soft solder alloy of the present invention, the cooling rate during solidification can be considered to further refine the alloy structure. For example, the brazing joint can be cooled at a cooling rate of 2~3°C / s or higher. Other joining conditions can be appropriately adjusted according to the alloy composition of the soft solder alloy.

[0107] 6. Applications

[0108] The solder alloy of the present invention can be effective in various soldering methods, especially by wave soldering. It is effective in the case of wave soldering of laminated substrates with multiple substrates stacked on top of each other. The composition of the jet solder used in wave soldering may change if it is used for a long time, so it can also be used as a supplementary solder for setting the jet solder to the desired composition. In this case, the supplementary solder can be supplemented by adjusting the composition within the scope of the present invention. The temperature of the jet solder used in wave soldering is approximately 230~260°C. In addition, other bonding conditions can be appropriately adjusted according to the alloy composition, solid fraction and liquid fraction of the solder alloy.

[0109] 7. Method for manufacturing solder alloy

[0110] The solder alloy of the present invention can be manufactured by pre-manufacturing SnAg alloy and SnCu alloy and melting them together with Bi and P. As a manufacturing example, alloys of Sn and Ag, and alloys of Sn and Cu, are manufactured by weighing each alloy in a predetermined amount and weighing Bi and P. The reason for this manufacturing method can be explained as follows: It takes a considerable amount of time to melt Ag (with a melting point of approximately 860°C) and Cu (with a melting point of approximately 1100°C) into Sn. In particular, Cu has a significant surface oxidation, so a long melting time will be affected by oxidation. On the other hand, if a SnAg alloy in which Ag is pre-melted into Sn and a SnCu alloy in which Cu is pre-melted into Sn are prepared in advance, the melting time into Sn can be significantly shortened.Regarding the intermetallic compounds formed during the production of each alloy, for example, Cu6Sn5 has a melting point of 415°C and Ag3Sn has a melting point of 480°C. These intermetallic compounds are mainly formed inside the alloy, so the possibility of oxidation is considered to be low.

[0111] The solder alloy of the present invention can be manufactured as a low-alpha-ray alloy by using low-alpha-ray materials as its raw materials. When such a low-alpha-ray alloy is used for the formation of solder bumps around the memory, it can suppress soft errors.

[0112] Examples

[0113] Solder alloys composed of the alloy compositions shown in Tables 1-2 were used as evaluation 1, and the drop impact test (DROP) was evaluated; as evaluation 2, the thermal cycling test (TCT) was evaluated; as evaluation 3, the chip stand-up test was evaluated; as evaluation 4, the solder bridging and solder tip test was evaluated; as evaluation 5, the EM resistance test was evaluated. The evaluation methods are described below.

[0114] Evaluation 1: Drop Impact Test (DROP)

[0115] The solder alloys shown in Tables 1 and 2 were atomized to form solder powder. These were mixed with a soldering flux (GLV manufactured by Senju Metal Industries, Ltd.) containing rosin, solvent, activator, thixotropic agent, organic acid, etc., to prepare solder pastes for each solder alloy. The solder paste contained 88% by mass of alloy powder and 12% by mass of flux.

[0116] The solder paste was printed on a 0.8 mm thick printed circuit board (material: FR-4) using a 100 μm thick metal mask. Five BGA components were mounted on each board using a pick-and-place machine. Reflow soldering was performed at a maximum temperature of 240°C and a holding time of 60 seconds to prepare two test boards. Then, each board was individually divided into five pieces, each containing one BGA component, to prepare a total of 10 evaluation samples.

[0117] Next, the two ends of the evaluation sample were fixed to the base with bolts so that the BGA components faced the base. In this state, the resistance value was measured according to the JEDEC standard, and an impact with an acceleration of 1500G was applied to evaluate the drop impact resistance. The cracking progress was evaluated by the number of drops up to 50% increase in resistance value from the initial value. A result of 100 or more drops was marked as "◎". A result of 90 or more but less than 100 drops was marked as "〇". A result of less than 90 drops was marked as "×".

[0118] Evaluation 2: Thermal Cycling Test (TCT)

[0119] Solder paste was prepared in the same manner as in Evaluation 1. The prepared test substrate was placed in a thermal cycling test apparatus with conditions set to low temperature -40°C, high temperature +125°C, and holding time of 10 minutes. The number of cycles at which the resistance value of at least one BGA component increased from the initial resistance value of 3~5Ω to more than 15Ω was determined. If the number of iterations exceeds 700, it is judged as "◎".The result is "0" if the number of cycles is 650-699. The result is "×" if the number of cycles is less than 650.

[0120] Evaluation 3: Chip Stand-up

[0121] Solder paste was prepared in the same manner as Evaluation 1. The solder paste was printed onto the Cu pads of a 6-layer printed circuit board (FR-4, Cu-OSP) using a 150μm metal mask, and 12 3216 chip resistors were mounted using a pick-and-place machine. Then, the test substrate was prepared by melting and reflowing under a heating condition of 245 °C for 40 seconds. The number of chips that stood up after mounting was counted. The result is "◎" if the number of chips that stood up was 0. The result is "0" if the number of chips that stood up was 1. The result is "×" if the number of chips that stood up was 2 or more.

[0122] Evaluation 4: Solder Linkage and Solder Tips

[0123] First, prepare a 4-terminal Sn-plated resistor with 12 terminals, each 0.5 mm wide and 0.8 mm apart. Insert the terminals into the through-hole of the epoxy glass printed circuit board (CEM-3). Introduce the solder alloys shown in Tables 1 and 2 into the solder bath and perform wave soldering. Wave soldering was performed using a Malcom FS-1 reflow oven simulator under the following test conditions.

[0124] Test Conditions

[0125] Solder bath: Malcom FS-1 reflow oven simulation demonstration device

[0126] Solder amount: 15kg Instruction manual 9 / 12 pages 11 CN 122252858 A

[0127] Flux: Senju Metal Industries, Ltd. flux (trade name: ES-1061SP2)

[0128] Solder temperature in the solder bath: 255℃

[0129] Visually evaluate whether bridging has occurred. In addition, visually check whether solder spikes are generated at the rounded corners. If no bridging or solder spikes are found, it is evaluated as "◎"; if the number of resistors with bridging or solder spikes is 1 to 2, it is evaluated as "〇"; if the number of resistors with bridging or solder spikes is 3 or more, it is evaluated as "×".

[0130] Evaluation 5: EM Resistance

[0131] For the EM test samples, solder balls with a diameter of 0.24 mm, made of the solder alloys shown in Tables 1 and 2, were used to reflow solder on a 12 mm × 12 mm package substrate with a Cu electrode having a diameter of 0.24 mm to create a package. Then, solder paste composed of Sn-3.0Ag-0.5Cu was printed on an epoxy glass substrate (FR-4) with a size of 29 mm × 19 mm and a thickness of 0.8 mm. The package prepared above was mounted on the substrate, and a reflow soldering test substrate was created under the conditions of a maximum temperature of 240°C and a holding time of 90 seconds.

[0132] The fabricated test substrate was connected to a compact variable switching power supply (manufactured by Kikusui Electronics Co., Ltd.: PAK-A). The test substrate was energized in a silicone oil bath maintained at 125°C, with a current density of 100 A / mm² and a voltage of 5.0 V. The resistance of the sample was continuously measured during energization, and the time required for the resistance to increase by 150% from its initial value was measured. Cases exceeding 350 hours were rated as "◎", cases between 300 and 350 hours were rated as "〇", and cases less than 300 hours were rated as "×".

[0133] The results are shown in Tables 1 and 2.

[0134] [Table 1] Specification 10 / 12 pages 12 CN 122252858 A

[0135]

[0136] [Table 2] Specification 11 / 12 pages 13 CN 122252858 A

[0137]

[0138] As can be seen from Tables 1 and 2, all evaluations of Examples 1 to 51 are “0” or “◎”. In particular, the results show that Examples 2, 3, 10 to 22, 26 to 45, and 47 to 50, which do not contain Ni and satisfy equations (1) to (3), all have evaluations of “◎”, and are superior in the examples.

[0139] On the other hand, Comparative Examples 1 and 2 have poor TCT, chip stand-up, and EM resistance due to the low Ag content. Comparative Example 3 has poor DROP due to the high Ag content. Comparative Examples 4 to 10 all have chip stand-up in addition to DROP due to the even higher Ag content.

[0140] Comparative Examples 11 and 12 had poor TCT and EM resistance due to low Cu content. Comparative Example 13 had high Cu content, resulting in frequent bridging and solder spikes. Comparative Example 14 had poor EM resistance due to low Bi content. Comparative Examples 15-19 had poor drop due to high Bi content. Comparative Examples 20-22 had frequent bridging and solder spikes due to inappropriate P content.

[0141] The results of observing the cross-section of the brazed joint for the samples whose EM resistance was evaluated are shown in FIG1. ​​FIG1 is a cross-sectional SEM photograph of the brazed joint, FIG1(a) is Comparative Example 1, and FIG1(b) is Example 22. It is clear from FIG1(a) that in the quadrilateral-enclosed area of ​​Comparative Example 1, Cu on the upper electrode is cut off, and Cu is deposited on the lower electrode. On the other hand, as clearly shown in Figure 1(b), no Cu movement was observed in the quadrilateral-enclosed region of Example 22. The same result was obtained in other examples. It should be noted that typical Cu erosion is a phenomenon where both electrodes are eroded, and Cu does not deposit on the other electrode; therefore, Cu erosion and electromigration can be easily distinguished.Description 12 / 12 Page 14 CN 122252858 A Figure 1 Description Drawings 1 / 1 Page 15 CN 122252858 A Abstract Abstract: The present invention provides a solder alloy, a solder paste, a solder ball, a preformed solder and a solder joint, which have excellent drop impact resistance and thermal cycle resistance, can suppress the generation of tombstoning and solder bridging·solder icicle, and can also suppress the generation of electromigration. The solder alloy has the following alloy composition: in mass%, Ag: 0.3-1.9%, Cu: 0.40- 1.00%, Bi: 0.5-4.9%, P: 0.00100-0.02000%, and the balance being Sn. The alloy composition may further contain at least one of Ge, Co, and Ga in an amount of 0.06% or less in mass%, respectively. In addition, the alloy composition may further contain at least one of As, In, Zr, Mn, Ti, Zn, Fe, Al, Ni, Au, Mg, Cr, and Pt in an amount of 0.06% or less in mass%.

Claims

1. A soft solder alloy, characterized in that, It has the following alloy composition by mass%: Ag: 0.3~1.9%, Cu: 0.40~1.00%, Bi: 0.5~4.9%, P: 0.00100~0.02000%, with the balance being Sn.

2. The solder alloy according to claim 1, wherein, The alloy composition also contains Ga in an amount of less than 0.06% by mass.

3. The solder alloy according to claim 1 or 2, wherein, The alloy composition also contains at least one of As, In, Zr, Mn, Ti, Zn, Fe, Al, Au, Mg and Pt in amounts of less than 0.06% by mass.

4. The solder alloy according to claim 1 or 2, wherein, The alloy composition satisfies all of the following equations (1) to (3): 0.0007≤Ag×Cu×Bi×P≤0.0110 (1) 110≤Ag / (P×Cu)≤799 (2) 0.67≤(Ag+Bi) / (Ag+Cu+Bi)≤0.91 (3) Formula In equations (1) to (3), Ag, Cu, Bi and P represent the content of the alloy composition in terms of mass%.

5. The solder alloy according to claim 3, wherein, The alloy composition satisfies all of the following equations (1) to (3): 0.0007≤Ag×Cu×Bi×P≤0.0110 (1) 110≤Ag / (P×Cu)≤799 (2) 0.67≤(Ag+Bi) / (Ag+Cu+Bi)≤0.91 (3) Formula In equations (1) to (3), Ag, Cu, Bi and P represent the content of the alloy composition in terms of mass%.

6. A solder paste having a solder powder composed of a solder alloy as described in claim 1 or 2.

7. A solder paste having a solder powder composed of the solder alloy of claim 3.

8. A solder ball comprising the solder alloy of claim 1 or 2.

9. A solder ball comprising the solder alloy of claim 3.

10. A preformed solder, comprising the solder alloy of claim 1 or 2.

11. A preformed solder, comprising the solder alloy of claim 3.

12. A brazing joint having the soft solder alloy as described in claim 1 or 2.

13. A brazing joint having the soft solder alloy of claim 3.

Images