Flat composite brazing filler metal and preparation method and application thereof
By incorporating through-holes in the solder and embedding high-melting-point metal balls, the problems of weld voids and uneven thickness are solved, achieving high quality and stability of the weld layer, making it suitable for welding electronic components.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SOLDERWELL MICROELECTRONIC PACKAGING MATERIALS CO LTD
- Filing Date
- 2024-08-13
- Publication Date
- 2026-06-23
AI Technical Summary
Existing brazing filler metals are prone to producing weld voids and uneven thickness during the welding process, which leads to a decrease in the reliability and impact resistance of the weld layer, and the gas generated during the welding process cannot be effectively discharged.
A flat composite brazing filler metal is designed with uniformly distributed through holes, and a metal ball is embedded in each through hole. The melting point of the metal ball is higher than that of the brazing filler metal to ensure that it does not melt during the welding process. The gap between the through holes and the metal ball is used for gas discharge, which improves the uniformity and strength of the weld layer.
It effectively reduces the weld void rate, improves the thickness uniformity and welding strength of the weld layer, and ensures the stability and reliability of the welding quality.
Smart Images
Figure CN118989716B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of brazing filler metal technology, specifically to a flat composite brazing filler metal, its preparation method, and its application. Background Technology
[0002] Soldering is a connection method that uses a soldering alloy heated to a temperature below but above the melting point of the two electronic components to secure them together. During service, the solder joints between electronic components are subjected to severe tests such as thermal stress, high-density current, and power cycling. With the increasing precision and integration of electronic components, the requirements for solder joint quality are becoming increasingly stringent. The solder void ratio and thickness uniformity of the solder joint both affect its quality. If the solder void ratio is too high or the thickness uniformity is poor, the reliability of the solder joint will decrease, its resistance to thermal cycling and impact will deteriorate, and the solder joint will be prone to cracking or even breakage, potentially causing irreparable damage to the components.
[0003] Soldering with brazing filler metal is currently generally achieved through reduction soldering using fluxes, formic acid, or hydrogen. During soldering, the flux itself or the flux itself reducing the oxide film on the soldering surface and the solder surface will generate gas. Since there is no way for the gas to escape, it is trapped within the solder joint and difficult to dissipate, or even impossible to dissipate, thus causing considerable difficulties in reducing the solder void rate and improving solder quality. Simultaneously, because the solder is fluid after melting and lacks support capacity, the direction of pressure on the soldering surfaces of the upper and lower electronic components during soldering is often not perpendicular to the soldering surface, leading to a tilted solder layer and uneven solder layer thickness. In areas with thicker solder layers, the thermal resistance is higher, causing heat generated by the electronic components to accumulate in these areas, resulting in localized overheating and potentially causing component failure or burnout. In areas with thinner solder layers, insufficient solder makes the solder layer prone to voids, and a high void rate increases the thermal resistance of the solder joint.
[0004] Therefore, reducing the weld void rate and improving the thickness uniformity of the weld layer are crucial for improving the quality of the weld layer and ensuring the reliable operation of electronic components during service. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a flat composite solder, its preparation method and application.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In the first aspect, a flat composite brazing filler metal is provided, wherein the flat brazing filler metal is provided with a plurality of evenly distributed through holes and metal balls embedded in the through holes;
[0007] The through-hole is shaped like at least one of ellipse and polygon, and the area of the through-hole is 2-8 times the area of the large circle of the metal sphere; the melting point of the metal sphere is ≥200℃, which is the same as the melting point of the brazing filler metal; the diameter of the metal sphere is the same as the thickness of the flat brazing filler metal.
[0008] In some embodiments, the area of the through hole is 4-6 times the area of the great circle of the metal sphere.
[0009] In some embodiments, the spacing between adjacent through holes is 3-9 mm.
[0010] In some embodiments, the polygon is at least one of a right triangle, an isosceles triangle, a rectangle, a trapezoid, a parallelogram, and a rhombus.
[0011] In some embodiments, the metal is at least one selected from copper, copper alloys, nickel, nickel alloys, silver, silver alloys, and gold.
[0012] In some embodiments, the flat solder is one of tin-based solder, lead-based solder, bismuth-based solder, indium-based solder, zinc-based solder, antimony-based solder, and aluminum-based solder.
[0013] In some embodiments, the surface of the flat composite solder includes flux.
[0014] Secondly, a method for preparing the flat composite solder is provided, comprising the following steps:
[0015] The raw materials for the brazing filler metal are melted and cast into ingots according to a certain ratio, and then the ingots are rolled into flat brazing filler metal.
[0016] A through hole is punched into a flat brazing filler metal, and then a metal ball is embedded into the through hole to obtain a flat composite brazing filler metal.
[0017] In some embodiments, the method for preparing the flat composite solder further includes coating the surface of the flat composite solder with flux.
[0018] Thirdly, the application of the aforementioned flat composite solder in the soldering of electronic components is provided.
[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention has multiple evenly distributed through holes on the flat brazing filler metal, and embeds metal balls with a melting point 200°C higher than that of the brazing filler metal into the through holes, so that the metal balls will not roll, and there will be no loss, misalignment or stacking of metal balls, which improves the uniformity of the distribution of metal balls in the brazing filler metal, thereby improving the thickness uniformity of the weld layer; on the other hand, there is a gap between the through holes and the metal balls, which allows the gas generated during the welding process to be discharged from the gap, reducing the weld void rate; furthermore, the metal balls will not melt during the welding process, and the wetting effect of the metal balls and the molten brazing filler metal improves the weld strength. Attached Figure Description
[0020] Figure 1 This is a structural diagram of the flat composite solder of Example 1;
[0021] Figure 2 This is a structural diagram of the flat composite solder in Example 7;
[0022] Figure 3 This is a structural diagram of the flat composite brazing filler metal in Example 9. Detailed Implementation
[0023] To facilitate understanding of the present invention, a more comprehensive description will be given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.
[0024] As used in this article:
[0025] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.
[0026] The conjunction "composed of" excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of" appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.
[0027] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1-5” is disclosed, the described range should be interpreted as including ranges “1-4”, “1-3”, “1-2”, “1-2 and 4-5”, “1-3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.
[0028] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.
[0029] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (K is any number representing a multiplier). It is important to understand that, unlike the number of parts by mass, the sum of the mass parts of all components is not limited to 100 parts.
[0030] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).
[0031] In one aspect, a flat composite brazing filler metal is provided, wherein the flat brazing filler metal has a plurality of evenly distributed through holes and metal balls embedded in the through holes;
[0032] The through-hole is shaped like at least one of ellipse and polygon, and the area of the through-hole is 2-8 times the area of the large circle of the metal sphere; the melting point of the metal sphere is ≥200℃, which is the same as the melting point of the brazing filler metal; the diameter of the metal sphere is the same as the thickness of the flat brazing filler metal.
[0033] Specifically, the ratio of the area of the through hole to the area of the large circle of the metal sphere can be, but is not limited to, 2, 2.2, 2.5, 2.7, 3, 3.3, 3.5, 3.8, 4, 4.2, 4.5, 4.7, 5, 5.3, 5.5, 5.8, 6.2, 6.5, 6.7, 7, 7.3, 7.5, 7.8, or 8.
[0034] Specifically, the melting point of the metal ball and the melting point of the brazing filler metal can be, but are not limited to, 200°C, 220°C, 250°C, 270°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, or 1200°C.
[0035] The present invention has multiple evenly distributed through holes on a flat brazing filler metal, and embeds metal balls into the through holes, so that the metal balls will not roll, and there will be no loss, misalignment or stacking of metal balls. This improves the uniformity of the distribution of metal balls in the brazing filler metal, thereby improving the thickness uniformity of the weld layer.
[0036] When the through hole is elliptical, the diameter of the metal ball is the same as the minor axis of the ellipse, that is, the major circle of the metal ball is tangent to the minor axis of the ellipse, so that the metal ball can be stably embedded inside the through hole; if the through hole is polygonal, the metal ball is tangent to at least two sides of the polygon, so that the metal ball can be stably embedded inside the through hole.
[0037] The ratio of the through-hole area to the large circumference area of the metal sphere is one of the factors affecting the welding performance of flat composite brazing filler metal. This invention selects a specific ratio of through-hole area to the large circumference area of the metal sphere. This not only ensures that the metal sphere is stably embedded inside the through-hole and does not fall out, but also allows gas generated during welding to escape through the gap between the edge of the through-hole and the edge of the metal sphere. Furthermore, it ensures that the molten brazing filler metal fills the gap completely and distributes evenly, reducing the weld void rate, improving the uniformity of the weld layer thickness, and enhancing the welding quality. If the ratio of the through-hole area to the large circumference area of the metal sphere is less than 2, the gas generated during welding is difficult to escape, resulting in a high weld void rate. If the ratio is greater than 8, too much brazing filler metal is missing, preventing the molten brazing filler metal from flowing back to fill the gap during welding, leading to an increased weld void rate and even incomplete welds. Therefore, this invention further optimizes the ratio of the through-hole area to the large circumference area of the metal sphere to be 4-6 to obtain a flat brazing filler metal with a low weld void rate and uniform weld layer thickness.
[0038] By limiting the melting point difference between the metal ball and the brazing filler metal to at least 200°C, it is ensured that the metal ball will not melt during the welding process, preventing the weld layer from tilting due to uneven flow of molten brazing filler metal and improving the uniformity of the weld layer thickness. If the diameter of the metal ball is smaller than the thickness of the flat brazing filler metal, the upper and lower welding surfaces will not contact the metal ball when the brazing filler metal melts, resulting in uneven flow of molten brazing filler metal. Furthermore, air bubbles may exist between the brazing filler metal and the metal ball, leading to a decrease in the uniformity of the weld layer thickness and potentially an increase in the void rate in thinner sections of the weld layer. If the diameter of the metal ball is larger than the thickness of the flat brazing filler metal, the molten brazing filler metal will be suspended in mid-air, preventing the upper and lower welding surfaces from contacting the molten brazing filler metal, leading to an increase in the weld void rate and even incomplete welds. In addition, because the diameter of the metal ball is larger than the thickness of the flat brazing filler metal, the thickness of the molten brazing filler metal is thinner than the metal ball, making it impossible to control the uniformity of brazing filler metal distribution through the metal ball, thus reducing the uniformity of the weld layer thickness.
[0039] In some embodiments, the spacing between adjacent through holes is 3-9 mm; for example, it can be, but is not limited to, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, or 8 mm.
[0040] In this invention, the spacing between adjacent through holes refers to the distance between the edges of adjacent through holes. If the spacing between adjacent through holes is less than 3mm, it will be inconvenient to demold during the processing of the through holes. Moreover, if the through holes are too dense, the strength of the flat brazing filler metal will decrease, resulting in deformation of the flat brazing filler metal and even tearing of the through holes, thus reducing the yield of flat brazing filler metal with through holes on the surface. If the spacing between adjacent through holes is greater than 9mm, the gas generated during the welding process will not be easy to escape due to the distance between the through holes, resulting in an increase in the welding void rate.
[0041] In some embodiments, the polygon is at least one of a right triangle, an isosceles triangle, a rectangle, a trapezoid, a parallelogram, and a rhombus.
[0042] Compared to polygonal shapes, elliptical through holes have several advantages. First, the edges of elliptical through holes are smooth, making them easy to demold during processing. This makes processing easier and less costly, which helps improve the yield of flat brazing filler metals with through holes on their surfaces. Second, when a metal ball is inscribed within an elliptical through hole, the contact area between the through hole and the metal ball is larger, which further improves the stability of the metal ball. The preferred shape of the through hole in this invention is elliptical.
[0043] In some embodiments, the metal is at least one selected from copper, copper alloys, nickel, nickel alloys, silver, silver alloys, and gold.
[0044] The metal spheres composed of the aforementioned metals can ensure that the metal spheres and molten brazing filler metal are wetted during the welding process, reducing the weld void rate and improving the uniformity and stability of the weld layer, thereby improving the weld quality.
[0045] In some embodiments, the flat solder is one of tin-based solder, lead-based solder, bismuth-based solder, indium-based solder, zinc-based solder, antimony-based solder, and aluminum-based solder.
[0046] The flat solder in this invention can be prepared by methods known in the art; or by purchasing commercially available products.
[0047] In some embodiments, the surface of the flat composite solder includes flux.
[0048] Secondly, the method for preparing the flat composite solder of the present invention includes the following steps:
[0049] The raw materials for the brazing filler metal are melted and cast into ingots according to a certain ratio, and then the ingots are rolled into flat brazing filler metal.
[0050] A through hole is punched into a flat brazing filler metal, and then a metal ball is embedded into the through hole to obtain a flat composite brazing filler metal.
[0051] Those skilled in the art can select different melting temperatures, casting temperatures, and rolling processes based on the different raw materials.
[0052] In some embodiments, the method for preparing the flat composite solder further includes coating the surface of the flat composite solder with flux.
[0053] In this invention, flux is coated onto the surface of the flat composite brazing filler metal to remove the oxide layer on the filler metal surface and the welding surface, thereby improving the welding quality. If formic acid or hydrogen is used for reduction welding, the surface of the flat composite brazing filler metal may not be coated with flux; the oxide layer on the filler metal surface and the welding surface can be removed by formic acid or hydrogen, thus improving the welding quality.
[0054] Specifically, the present invention does not impose specific restrictions on the method of coating the flux, as long as the flux can be coated onto the surface of the flat composite solder, such as brushing, dipping, rolling, and spraying.
[0055] Thirdly, the application of the aforementioned flat composite solder in the soldering of electronic components is provided.
[0056] Example 1
[0057] like Figure 1As shown, this embodiment provides a flat composite brazing filler metal with multiple evenly distributed elliptical through holes. The dimensions of the flat brazing filler metal are 57*48.5*0.3mm, the ratio of the area of the through hole to the area of the large circle of the metal ball is 5, the minor axis of the ellipse is 0.3mm, the diameter of the metal ball is 0.3mm, and the spacing between adjacent through holes is 3mm. The metal ball is a copper ball with a melting point of 1085℃, and the flat brazing filler metal is Sn95Sb5 with a melting point of 240℃.
[0058] This embodiment also provides a method for preparing a flat composite solder, including the following steps:
[0059] Tin ingots and antimony ingots with a mass ratio of Sn:Sb = 95:5 are smelted and cast to obtain Sn95Sb5 ingots. The Sn95Sb5 ingots are then rolled to form flat brazing filler metal with a thickness of 0.3 mm.
[0060] Elliptical through holes are punched out on a flat brazing filler metal. The spacing between adjacent through holes is 3 mm, the minor axis of the ellipse is 0.3 mm, and the area of the through hole is 5 times the area of the major circle of the metal sphere.
[0061] The metal ball is embedded in the elliptical through hole and punched to obtain a flat composite brazing filler metal with dimensions of 57*48.5*0.3mm.
[0062] Example 2
[0063] This embodiment provides a flat composite brazing filler metal. The only difference between this flat composite brazing filler metal and that of Embodiment 1 is that the ratio of the area of the through hole to the area of the large circle of the metal sphere is 4. All other aspects are the same as those of Embodiment 1.
[0064] Example 3
[0065] This embodiment provides a flat composite brazing filler metal. The only difference between this flat composite brazing filler metal and Embodiment 1 is that the ratio of the area of the through hole to the area of the large circle of the metal sphere is 3. All other aspects are the same as in Embodiment 1.
[0066] Example 4
[0067] This embodiment provides a flat composite brazing filler metal. The only difference between this flat composite brazing filler metal and that of Embodiment 1 is that the ratio of the area of the through hole to the area of the large circle of the metal sphere is 6. All other aspects are the same as those of Embodiment 1.
[0068] Example 5
[0069] This embodiment provides a flat composite brazing filler metal. The only difference between this flat composite brazing filler metal and that in Embodiment 1 is that the ratio of the area of the through hole to the area of the large circle of the metal sphere is 2. All other aspects are the same as in Embodiment 1.
[0070] Example 6
[0071] This embodiment provides a flat composite brazing filler metal. The only difference between this flat composite brazing filler metal and that of Embodiment 1 is that the ratio of the area of the through hole to the area of the large circle of the metal sphere is 8. All other aspects are the same as those of Embodiment 1.
[0072] Example 7
[0073] like Figure 2 As shown, this embodiment provides a flat composite brazing filler metal. The only difference between this flat composite brazing filler metal and Embodiment 1 is that the shape of the through hole is rectangular, and the rest is the same as Embodiment 1.
[0074] Example 8
[0075] This embodiment provides a flat composite brazing filler metal. The only difference between the flat composite brazing filler metal in this embodiment and that in Embodiment 1 is that the shape of the through hole is a right triangle with two right-angled sides of 1mm and 0.71mm respectively. All other aspects are the same as in Embodiment 1.
[0076] Example 9
[0077] like Figure 3 As shown, this embodiment provides a flat composite brazing filler metal. The only difference between the flat composite brazing filler metal in this embodiment and that in embodiment 1 is that the shape of the through hole is an isosceles triangle with a base of 1.04 mm and a waist of 0.856 mm. All other aspects are the same as in embodiment 1.
[0078] Example 10
[0079] This embodiment provides a flat composite brazing filler metal. The only difference between the flat composite brazing filler metal in this embodiment and that in Embodiment 1 is that the shape of the through hole is a right trapezoid with an upper base of 0.9 mm, a lower base of 1.455 mm, and a waist of 0.3 mm. All other aspects are the same as in Embodiment 1.
[0080] Example 11
[0081] This embodiment provides a flat composite brazing filler metal. The only difference between this flat composite brazing filler metal and Embodiment 1 is that the spacing between adjacent through holes is 9 mm, and all other aspects are the same as in Embodiment 1.
[0082] Example 12
[0083] This embodiment provides a flat composite brazing filler metal. The only difference between this flat composite brazing filler metal and that of Embodiment 1 is that the metal balls are nickel balls with a melting point of 1445°C. All other aspects are the same as those of Embodiment 1.
[0084] Example 13
[0085] This embodiment provides a flat composite brazing filler metal. The only difference between the flat composite brazing filler metal in this embodiment and that in Embodiment 1 is that the metal balls are Ag72Cu28 balls with a melting point of 779℃. All other aspects are the same as in Embodiment 1.
[0086] Example 14
[0087] This embodiment provides a flat composite solder. The only difference between the flat composite solder in this embodiment and that in Embodiment 1 is that the surface of the flat composite solder is coated with rosin-based flux, and the mass of the flux is 0.4% of the mass of the flat composite solder. All other aspects are the same as in Embodiment 1.
[0088] Comparative Example 1
[0089] This comparative example provides a flat composite brazing filler metal. The only difference between this flat composite brazing filler metal and Example 1 is that the ratio of the area of the through hole to the area of the large circle of the metal sphere is 1.33. All other aspects are the same as Example 1.
[0090] Comparative Example 2
[0091] This comparative example provides a flat composite brazing filler metal. The only difference between this flat composite brazing filler metal and Example 1 is that the ratio of the area of the through hole to the area of the large circle of the metal sphere is 10. All other aspects are the same as in Example 1.
[0092] Comparative Example 3
[0093] This comparative example provides a flat composite brazing filler metal. The only difference between this flat composite brazing filler metal and Example 1 is that the shape of the through hole is a regular hexagon with a side length of 0.173; the ratio of the area of the through hole to the area of the large circle of the metal sphere is 1.1. All other aspects are the same as in Example 1.
[0094] Comparative Example 4
[0095] This comparative example provides a flat composite brazing filler metal. The only difference between this flat composite brazing filler metal and Example 1 is that the through hole is circular with a diameter of 0.3 mm. All other aspects are the same as in Example 1.
[0096] Comparative Example 5
[0097] This comparative example provides a flat composite brazing filler metal. The only difference between this flat composite brazing filler metal and Example 1 is that the spacing between adjacent through holes is 12 mm, and all other aspects are the same as in Example 1.
[0098] Comparative Example 6
[0099] This comparative example provides a flat composite brazing filler metal. The only difference between this flat composite brazing filler metal and Example 1 is that the metal ball is a lead ball with a melting point of 327°C. All other aspects are the same as in Example 1.
[0100] Comparative Example 7
[0101] This comparative example provides a flat composite brazing filler metal. The only difference between this flat composite brazing filler metal and Example 1 is that there is no metal ball embedded in the through hole. All other aspects are the same as Example 1.
[0102] Comparative Example 8
[0103] This comparative example provides a flat composite solder, the preparation method of which includes the following steps:
[0104] Tin ingots and antimony ingots with a mass ratio of Sn:Sb = 95:5 are melted and cast into ingots, which are then rolled into flat brazing filler metal with a thickness of 0.3 mm. The melting point of the flat brazing filler metal is 240℃.
[0105] Then, copper balls with a diameter of 0.3 mm and a melting point of 1085 °C are evenly sprinkled on the surface of the flat brazing filler metal. The copper balls are then pressed into the interior of the flat brazing filler metal. After cutting, a flat composite brazing filler metal with dimensions of 57*48.5*0.3 mm is obtained.
[0106] Comparative Example 9
[0107] This comparative example provides a flat composite solder, the preparation method of which includes the following steps:
[0108] Tin ingots and antimony ingots with a mass ratio of Sn:Sb = 95:5 were mixed and melted to obtain a molten liquid;
[0109] Then, copper balls with a diameter of 0.3 mm and a melting point of 1085 °C are added to the molten liquid and cooled to solidify into brazing filler metal blocks;
[0110] The brazing filler block is rolled and cut to obtain a flat composite brazing filler with dimensions of 57*48.5*0.3mm.
[0111] Comparative Example 10
[0112] This comparative example provides a flat composite solder, the preparation method of which includes the following steps:
[0113] Sn95Sb5 alloy solder powder is mixed with copper balls with a diameter of 0.3mm, and then pressed into a flat composite solder with a size of 57*48.5*0.3mm.
[0114] Comparative Example 11
[0115] This comparative example provides a flat solder, the preparation method of which includes the following steps:
[0116] Tin ingots and antimony ingots with a mass ratio of Sn:Sb = 95:5 are smelted and cast to obtain Sn95Sb5 ingots. The Sn95Sb5 ingots are then rolled and punched to obtain flat brazing filler metal with dimensions of 57*48.5*0.3mm. The melting point of the flat brazing filler metal is 240℃.
[0117] Comparative Example 12
[0118] This comparative example provides a flat solder. The only difference between this flat solder and Comparative Example 11 is that the surface of the flat solder is coated with the same flux as in Example 11, and the mass of the flux is 0.4% of the mass of the flat solder.
[0119] Performance testing
[0120] The welding performance of the flat composite brazing filler metal or flat brazing filler metal obtained in the above embodiments and comparative examples was tested.
[0121] The preparation method of the welded parts is as follows:
[0122] Material to be soldered: Copper-clad DBC board with dimensions of 57*48.5*2mm;
[0123] Welding method: Flat composite brazing filler metal or flat brazing filler metal without flux on the surface is used as test group 1, and flat composite brazing filler metal or flat brazing filler metal coated with flux on the surface is used as test group 2.
[0124] The welding method for test group 1 is as follows: the flat composite solder or flat solder of test group 1 is sandwiched between two copper-clad DBC boards and vacuum formic acid reflow soldering is performed to obtain the welded parts;
[0125] The welding method for test group 2 is as follows: the flat composite solder or flat solder of test group 2 is sandwiched between two copper-clad DBC boards and subjected to atmospheric pressure reflow welding to obtain the welded parts;
[0126] The test method for weld void rate is as follows: use an ultrasonic scanner to detect voids in the welded parts. The smaller the void rate of the weld layer, the better the weld quality.
[0127] The test method for weld layer thickness difference is as follows: measure the maximum and minimum thickness of the welded parts with a micrometer. Weld layer thickness difference = maximum thickness - minimum thickness. The larger the weld layer thickness difference, the more uneven the thickness of the weld layer, that is, the greater the tilt of the weld layer.
[0128] The performance test results are shown in Table 1.
[0129] Table 1 Performance Test Results
[0130]
[0131]
[0132] As can be seen from the data of test group 1 in Table 1, for flat brazing filler metals without flux on the surface, the welding void rate of the flat composite brazing filler metal without flux on the surface of the present invention is 0.02-1.01%, and the difference in weld layer thickness is 0.003-0.025mm, which significantly improves the welding void rate and the difference in weld layer thickness.
[0133] Comparing Examples 1-6 and Comparative Examples 1-2, it can be seen that when the ratio of the area of the through hole to the area of the large circle of the metal sphere is 4-6, the weld void rate of the obtained flat composite brazing filler metal is 0.02-0.50%, and the weld layer thickness difference is 0.003-0.009 mm. This indicates that when the ratio of the area of the through hole to the area of the large circle of the metal sphere is 4-6, the weld void rate and weld layer thickness difference of the obtained flat composite brazing filler metal are lower.
[0134] Comparing Examples 1, 7-10 and 3-4, it can be seen that the shape of the through hole can only achieve a flat composite brazing filler metal with lower welding void ratio and weld layer thickness difference within the protection scope of the present invention.
[0135] Comparing Examples 1, 11 and 5, it can be seen that when the spacing between adjacent through holes is 3-9 mm, the weld void rate of the resulting flat brazing filler metal is 0.02-1.01%, and the weld layer thickness difference is 0.003-0.025 mm. This indicates that a spacing of 3-9 mm between adjacent through holes can reduce the weld void rate and weld layer thickness difference of the flat composite brazing filler metal.
[0136] Comparing Examples 1, 12-13 and Comparative Example 6, it can be seen that when the melting point of the metal ball is less than 200°C, the welding void rate and the difference in welding layer thickness of the resulting flat composite brazing filler metal are significantly increased.
[0137] Comparing Comparative Examples 7 and 11, it can be seen that in Comparative Example 7, by setting through holes in the flat brazing filler metal, the weld void rate of the flat composite brazing filler metal can be reduced. However, since no metal balls are embedded in the through holes, the difference in weld layer thickness is not significantly improved. Comparing Example 1 and 7, it can be seen that although setting through holes in the flat brazing filler metal in Comparative Example 7 can reduce the weld void rate, the lack of metal balls embedded in the through holes causes the weld layer to tilt, resulting in a larger weld void rate in thinner areas. This weakens the effect of the through holes in reducing the weld void rate, leading to an overall higher weld void rate compared to Example 1. Comparing Example 1 and 11, it can be seen that setting through holes in the flat brazing filler metal and embedding metal balls in the through holes can significantly reduce the weld void rate and the difference in weld layer thickness.
[0138] Comparing Example 1 and Comparative Examples 8-10, it can be seen that the method of sprinkling metal balls on the surface of the solder and then pressing them into the solder has several drawbacks. During the preparation of the flat composite solder, the metal balls roll, leading to loss, misalignment, and stacking, resulting in uneven distribution of the metal balls and increasing the weld void rate and weld layer thickness difference of the flat composite solder. The method of adding metal balls to molten solder and then solidifying it also results in uneven distribution of the metal balls due to their random distribution in the molten solder, thus increasing the weld void rate and weld layer thickness difference of the flat composite solder. The method of mixing solder powder and metal balls and then pressing them into flat composite solder has several drawbacks. First, the solder in the flat composite solder prepared by this method is prone to oxidation, resulting in a high weld void rate. Second, the cost of preparing flat composite solder by this method is high, which is not conducive to industrial production.
[0139] Data from test group 2 (i.e., Example 14 and Comparative Example 12) show that the welding void rate and weld layer thickness difference of the flat composite solder with flux on the surface of the present invention are significantly improved for flat solder with flux on the surface.
[0140] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention and not to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A flat composite brazing filler metal, characterized in that, The flat brazing filler metal has multiple evenly distributed through holes and metal balls embedded inside the through holes; The through-hole is elliptical and / or polygonal in shape, and the area of the through-hole is 2-8 times the area of the large circle of the metal ball; the melting point of the metal ball is at least 200°C higher than the melting point of the brazing filler metal; the diameter of the metal ball is the same as the thickness of the flat brazing filler metal. The metal sphere is made of at least one of the following materials: copper, copper alloy, nickel, nickel alloy, silver, silver alloy, and gold. The flat solder is one of tin-based solder, lead-based solder, bismuth-based solder, indium-based solder, zinc-based solder, antimony-based solder, and aluminum-based solder.
2. The flat composite brazing filler metal as described in claim 1, characterized in that, The area of the through hole is 4-6 times the area of the large circle of the metal sphere.
3. The flat composite brazing filler metal as described in claim 1, characterized in that, The spacing between adjacent through holes is 3-9 mm.
4. The flat composite brazing filler metal as described in claim 1, characterized in that, The polygon is at least one of an isosceles triangle, a rectangle, a trapezoid, and a parallelogram.
5. The flat composite brazing filler metal according to any one of claims 1-4, characterized in that, The surface of the flat composite solder includes flux.
6. A method for preparing a flat composite solder as described in any one of claims 1-5, characterized in that, Includes the following steps: The raw materials for the brazing filler metal are melted and cast into ingots according to a certain ratio, and then the ingots are rolled into flat brazing filler metal. A through hole is punched into a flat brazing filler metal, and then a metal ball is embedded into the through hole to obtain a flat composite brazing filler metal.
7. The method for preparing the flat composite solder as described in claim 6, characterized in that, The method for preparing the flat composite solder also includes coating the surface of the flat composite solder with flux.
8. The application of the flat composite solder as described in any one of claims 1-5 in the soldering of electronic components.