CN111151911A

CN111151911A - Corrosion-resistant high-strength low-temperature welding material and preparation method thereof

Info

Publication number: CN111151911A
Application number: CN202010141875.9A
Authority: CN
Inventors: 徐永巧
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-03-04
Filing date: 2020-03-04
Publication date: 2020-05-15

Abstract

The invention provides a corrosion-resistant high-strength welding material which is characterized by comprising the following components in percentage by mass: 50-70% of Sn, 15-25% of Bi, 5-10% of Pb, Mn: 0.1-1%, La: 0.1-0.5%, Ca: 0.1-2%, Cu 0.25-0.5%, Al 0.1-0.5%, wherein the ratio of Bi to Pb is 2:1-3: 1. The welding material has the advantages of outstanding corrosion resistance, excellent mechanical property, simple preparation and few components, and is suitable for industrial production.

Description

Corrosion-resistant high-strength low-temperature welding material and preparation method thereof

Technical Field

The invention relates to a metal welding material and a preparation method thereof.

Background

Electronic components and electronic materials incorporated in electronic devices are deteriorated and destroyed when exposed to high temperatures without heat resistance. Such electronic parts and electronic materials must be soldered at low temperature, and for this purpose, a solder having a low melting point, that is, a low-temperature solder must be used. The low-temperature solder is not specifically defined, but generally means a solder having a solidus temperature and a liquidus temperature (melting point) lower than 183 ℃ which is a eutectic temperature of Pb-63 Sn. Among conventional low-temperature solders, there are Sn-52Bi-32Pb (melting point: 95 ℃ C.), Sn-54Bi-20Cd (melting point: 103 ℃ C.), Sn-40Pb-40Bi (melting point: 113 ℃ C.), Sn-51In (melting point: 117 ℃ C.), Sn-58Bi (melting point: 139 ℃ C.), Sn-32Pb-18Cd (melting point: 143 ℃ C.), and Sn-32Cd (melting point: 175 ℃ C.). . Since the solidus temperature and the liquidus temperature can be adjusted by adding Pb and Cd in appropriate amounts, low-temperature solders having various melting points can be obtained. However, low-temperature solders containing Pb and Cd have a public hazard that adversely affects human bodies, and thus their use is regulated. Thus, low temperature solders containing no or low amounts of Pb and Cd are required.

In addition, the solder material also needs to have excellent mechanical properties (tensile strength, bending, elongation, etc.) in the soldered portion. That is, when a tensile force is applied to the soldered base material, the soldered portion is easily torn off, and the function of the electronic device is completely damaged. Similarly, when a bending force is applied to the base material of the brazed portion, the solder must have ductility to the extent that the solder can be easily bent and does not crack. In addition, the solder is required to have corrosion resistance. When the soldered electronic device is used only indoors, there is no difference in cooling and heating, and no corrosion problem is involved because of the good environment. However, electronic devices used in devices for data communication offices, automobiles, military devices, space-related devices, outdoor entertainment devices, and the like are often installed outdoors, and corrosion of solder becomes a problem.

Disclosure of Invention

Aiming at the problems, the invention provides a corrosion-resistant high-strength low-temperature welding material which is characterized by comprising the following components in percentage by mass:

50-70% of Sn, 15-25% of Bi, 5-10% of Pb, Mn: 0.1-1%, La: 0.1-0.5%, Ca: 0.1-2%, Cu 0.25-0.5%, Al 0.1-0.5%, wherein the ratio of Bi to Pb is 2:1-3: 1.

Preferably, the welding material comprises the following components: 67.1% of Sn, 20% of Bi, 10% of Pb, Mn: 0.5%, La: 0.4 percent; ca: 1%, Cu 0.5%, and Al 0.5%.

Preferably, the welding material comprises the following components: 67.1% of Sn, 22.5% of Bi, 7.5% of Pb, Mn: 0.5%, La: 0.4 percent; ca: 1%, Cu 0.5%, and Al 0.5%.

Preferably, the alloy phase includes a Sn-Pb-Bi ternary phase, a Pb-Bi-La-Ca quaternary phase and a Pb-Bi, Sn-Bi binary phase.

The present invention also provides a method for manufacturing the above-described welding material, characterized in that the manufacturing method comprises:

a. putting the raw materials into a crucible for melting, heating the metal to 400 ℃, and fully stirring after the metal is melted;

b. then naturally cooling the melted metal to 330-350 ℃, and maintaining for 15-20 minutes;

c. and taking out impurities on the surface of the melted alloy, and then putting the alloy into a die.

Preferably, the four metals Pb-Bi-La-Ca are added according to a certain proportion in the step a, the Pb-Bi metal is added according to a certain proportion after melting, and finally Sn and the rest other metals are added.

Preferably, the ratio of Pb-Bi-La-Ca added is 1:1:0.1: 1.

Preferably, the ratio of Pb-Bi added is 1: 1.

Lanthanum: the rare earth element (RE) can purify the alloy solution and effectively improve the mechanical properties and corrosion resistance of the welding material at room temperature and high temperature. In addition, the rare earth element can narrow the solidification temperature range of the alloy so as to improve the casting performance of the alloy, reduce the cracking of welding seams and improve the compactness of castings. As the rare earth element, gadolinium (Gd), yttrium (Y), neodymium (Nd), samarium (Sm), praseodymium (Pr), lanthanum (La), cerium (Ce) and the like are commonly used. However, elements such as Gd, Y, Nd, Sm and the like are expensive, and the use of these rare earth elements can greatly increase the production cost. In contrast, Pr, La and Ce are relatively economical rare earth elements, and La is a relatively easily available rare earth element among the three economical rare earth elements, so La is selected as an added alloying element. When the La element is less than 3 wt.%, the improvement effect on corrosion resistance, fluidity, and thermal conductivity is limited, and the La addition amount should not be excessively high in order to keep the production cost low. The La content in the present invention should be set in the range of 0.1 to 0.5% in consideration of the performance improvement effect and the production cost.

Bi and Pb: bi element is one of alloying elements commonly added in the alloy and has double functions of solid solution strengthening and aging strengthening. The addition of a proper amount of Bi can improve the plasticity, improve the melt fluidity, improve the casting performance and reduce the melting temperature. The addition of a small amount of Bi can improve the fluidity of the solder, and the bismuth alloy has the characteristic of no shrinkage during solidification and can produce the effect of strengthening the mechanical property of the alloy and be used for casting and printing type and high-precision casting molds. However, when the amount of Bi is too large, the fluidity of Bi alloy is rather lowered, and the weld material tends to be microscopically cracked or cracked. For this purpose, the Bi content is controlled as follows: 15 to 25 percent. Pb element is also one of common alloy additives, and lead is subjected to the action of oxygen, water and carbon dioxide in the air, and the surface of the lead is quickly oxidized to generate a protective film; under heating, lead can be combined with oxygen, sulfur and halogen quickly; lead hardly reacts with cold hydrochloric acid and cold sulfuric acid and can react with hot or concentrated hydrochloric acid and sulfuric acid; lead reacts with dilute nitric acid but not with concentrated nitric acid; lead can be slowly dissolved in a strongly alkaline solution. The Pb element can improve the fluidity of the alloy and forms an alloy phase with Bi. Because metals such as Bi in the welding material have active chemical properties, Sn-Bi-Pb forms an alloy phase of a matrix phase, and a compact oxide protective film is easily formed on the surface, so that the corrosion resistance of the welding material is improved. The invention finds that the corrosion resistance and the mechanical property can be better improved when the proportion of Bi and Pb is controlled, and is proved by the examples. It is presumed that a certain alloy phase ratio can synergistically promote the effects.

Calcium: the addition of the alkaline earth element Ca can advantageously improve the metallurgical quality, and at the same time, the addition cost of the Ca element is low, and the reason for adding the Ca is that: 1) the ignition temperature of the alloy melt is increased, the oxidation of the alloy during melting and heat treatment is reduced, and particularly, the small amount of Ca (for example, the content of Ca is 0.1 wt.%) can improve the oxidation resistance and heat resistance of the solder; 2) ca can refine solder grains and improve the corrosion resistance and creep resistance of the solder. In view of this, the Ca content of the low-cost high-thermal-conductivity die-casting solder of the present invention needs to be designed to be 0.1-2%.

Manganese: a small amount of Mn can form Fe-M compound with Fe element, thereby improving the corrosion resistance of the alloy. The Mn content in the high thermal conductive welding material according to the present invention should be set to 0.1 to 1%.

The alloy phase comprises Sn-Bi-Pb as a matrix phase, a small amount of Pb-Bi-La-Ca quaternary phase and Pb-Bi phase and other possible phase states. In the technical scheme, compared with the traditional Sn-Pb or Sn-Bi solder, the solder taking Sn-Bi-Pb as the matrix phase has better ductility and fluidity and higher thermal conductivity and corrosion resistance. The Pb-Bi-La-Ca quaternary phase can effectively improve the mechanical property and the creep resistance of the alloy, and the Pb-Bi phase can further improve the heat-conducting property, reduce the influence of other alloy elements on the heat-conducting property and improve the mechanical property of the alloy. Different alloy phases with different proportions are mutually promoted and have synergistic effect, and finally, the corrosion resistance, the mechanical property and other properties of the solder are enhanced, and the unexpected technical effect is achieved. Therefore, the solder with the microstructure has better mechanical property and corrosion resistance.

Detailed Description

Preparation of examples 1-2 and comparative examples 1-5

a. Putting four metals of Pb-Bi-La-Ca which are added according to the ratio of 1:1:0.1:1 into a crucible for melting, heating to 400 ℃, adding the Pb-Bi metal according to the ratio of 1:1 after the metals are melted, stirring and melting while keeping the temperature, finally adding Sn and the rest other metals, and fully stirring, wherein the specific addition amount is shown in the following table;

	Example 1	Example 2	Comparative example 1	Comparative example 2	Comparative example 3	Comparative example 4	Comparative example 5
								Sn	67.1%	67.1%	72.1%	67.1%	67.1%	71.1%	68.1%
Bi	20%	22.5%	25%	15%	25%	20%	20%
								Pb	10%	7.5%	0	15%	5%	10%	10%
Mn	0.5％	0.5％	0.5％	0.5％	0.5％	0.5％	0.5％
								La	0.4％	0.4％	0.4％	0.4％	0.4％	0	0.4％
Ca	1％	1％	1％	1％	1％	1％	0
								Cu	0.5%	0.5%	0.5%	0.5%	0.5%	0.5%	0.5%
Al	0.5%	0.5%	0.5%	0.5%	0.5%	0.5%	0.5%
								Bi：Pb	2：1	3:1	-	1：1	5：1	2：1	2：1。

Example 3

a. Putting all the formulations shown in the example 1 into a crucible for melting, heating to 400 ℃, and fully stirring after the metal is melted;

The workability of each solder was evaluated. The processed solder (thickness: 1.5mm) was repeatedly rolled and annealed, and when cracking and breaking occurred, the processing was completed, and when cracking and breaking did not occur, the processing was performed until the thickness reached 50 μm.

Using the pressed 0.1mm thick plate, in a vacuum atmosphere at 830 degrees C10 mm x 20mm alumina between brazing, 3mm x 4mm x 40mm test piece, through four-point bending test according to JIS R1601 determination of 10 point breaking strength. (test method was carried out according to JIS R1601).

After 6 hours of testing in acid salt spray, the resulting 0.1mm thick plates were tested for breaking strength according to the GB T10125-1997 standard, and the degree of breaking strength reduction was calculated as a percentage in comparison with the non-corroded.

Example 1

Example 2

Example 3

Comparative example 1

Comparative example 2

Comparative example 3

Comparative example 4

Comparative example 5

Rolling process

Thickness of 50um Cracking of

Thickness of 200mm Cracking of

Thickness of 1mm Cracking of

The thickness is 200um Cracking of

The thickness is 500um Cracking of

The thickness is 100um Cracking of

Post braze fracture strength

400Mpa

380Mpa

324Mpa

251Mpa

365Mpa

298Mpa

275Mpa

291Mpa

Fracture strength after corrosion Decrease by%

5%

9%

20%

14%

18%

32%

26%

From the above results, it can be seen that the different alloy phases mutually promote and cooperate to finally realize the enhancement of other performances of the solder, such as corrosion resistance, mechanics and the like, and have unexpected technical effects.

Claims

1. The corrosion-resistant high-strength low-temperature welding material is characterized by comprising the following components in percentage by mass:

2. The soldering material according to claim 1, wherein the soldering material comprises the following components: 67.1% of Sn, 20% of Bi, 10% of Pb, Mn: 0.5%, La: 0.4 percent; ca: 1%, Cu 0.5%, and Al 0.5%.

3. The soldering material according to claim 1, wherein the soldering material comprises the following components: 67.1% of Sn, 22.5% of Bi, 7.5% of Pb, Mn: 0.5%, La: 0.4 percent; ca: 1%, Cu 0.5%, and Al 0.5%.

4. The low-temperature solder material according to claim 1, wherein the alloy phase includes a ternary Sn-Pb-Bi phase, a quaternary Pb-Bi-La-Ca phase, and a binary Pb-Bi, Sn-Bi phase.

5. A manufacturing method of manufacturing the low-temperature solder material according to claim 1, characterized by comprising:

6. The method of claim 5, wherein the four metals Pb-Bi-La-Ca are added in a predetermined ratio in the step a, the Pb-Bi metal is added in a predetermined ratio after melting, and finally Sn and the remaining metals are added.

7. The method according to claim 6, wherein the ratio of Pb-Bi-La-Ca is 1:1:0.1: 1.

8. The method according to claim 6, wherein the ratio of Pb-Bi added is 1: 1.