KR101477077B1 - Brazing method between molibdenum and titanium alloy - Google Patents

Abstract

The present invention relates to a method for brazing heterogeneous molybdenum and titanium alloys. The present invention includes (a) a first heating step in which an Ag-Cu-based filler metal is arranged at a bonding portion of the molybdenum and titanium alloys, heating is performed up to 25°C to 100°C under the melting point of the Ag-Cu-based filler metal, and the state is maintained for a predetermined period of time; (b) a secondary heating step in which heating is performed up to 25°C to 100°C over the melting point of the Ag-Cu-based filler metal in the first heating step and the state is maintained for a predetermined period of time; and (c) a cooling step in which the Ag-Cu-based filler metal is cooled. According to the present invention, the melting point is much lower than the phase transformation temperature of Ti and Ti wettability is excellent, and thus no phase transformation is caused in the Ti alloy and sound brazing bonding is possible.

Description

{BRAZING METHOD BETWEEN MOLIBDENUM AND TITANIUM ALLOY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to brazing of heterogeneous materials, and more particularly, to a brazing method of molybdenum and titanium alloys in which a dissimilar metal such as molybdenum and a titanium alloy can be joined by brazing using a filler metal.

Brazing, commonly referred to as hard soldering, is a method in which two materials are bonded together by placing a filler metal between two materials and then melting the filler metal.

Such brazing is used when a filler metal is melted at a relatively high temperature of 450 DEG C or higher, so that the joints of the two materials are required to have excellent mechanical properties even in a relatively high temperature environment.

Such conditions may be exemplified by metals such as ceramics, stainless steel, or titanium alloys, and various types of filler metals may be used.

For example, Ni-based materials are used as filler metals when stainless steel is bonded to each other by brazing, and filler metals used when titanium alloys are bonded to each other by a brazing method One selected from the group consisting of aluminum (Al), silver (Ag), titanium (Ti), and zirconium (Zr).

The following Patent Document indicates that various materials classified into four types such as aluminum (Al), silver (Ag), titanium (Ti), and zirconium (Zr) are used for the brazing of the titanium alloy.

Korean Patent Publication No. 10-2011-0010145 (January 31, 2011)

However, the above-mentioned patent documents can use various materials classified into four types such as aluminum (Al) based, silver (Ag) based, titanium (Ti) based and zirconium (Zr) based on the brazing of the titanium alloy, It is not applicable to filler metals for brazing between dissimilar metals such as titanium alloys.

As such, brazing has a limitation that it is difficult or impossible to apply to the bonding of dissimilar materials, and in particular, the technique for bonding the filler metals for brazing between dissimilar metals such as molybdenum and titanium alloys, .

In view of the above, the present invention is capable of stably removing oxide or organic substances contained in a bonding material or filler metal by maintaining a vacuum zone below the melting point of the filler metal before reaching the brazing temperature, The brazing of molybdenum and titanium alloys which can prevent the change of physical properties of the titanium alloy without inducing the phase transformation of the alloy and improve the wettability with the titanium alloy so that a good brazing bond can be formed between the molybdenum and the titanium alloy of different kinds. The purpose of the method is to provide.

In order to achieve the above object, the present invention provides a method of manufacturing a semiconductor device, comprising the steps of: (a) disposing an Ag-Cu filler metal in a junction of molybdenum and a titanium alloy; (B) a second heating step in which the Ag-Cu-based filler metal is heated to a temperature of 25 to 100 ° C above the melting point of the Ag-Cu-based filler metal and held for a predetermined time in a first heating step, and (c) And a cooling step of cooling the filler metal. The present invention also provides a method of brazing a molybdenum-titanium alloy.

In the brazing method according to the present invention, the molybdenum may be pure molybdenum or a molybdenum alloy. In the brazing method according to the present invention, the Ag-Cu-based filler metal may include 60 to 70% of Ag, 30 to 40% of Cu, and 1 to 3% of Ti in weight percent.

In the brazing method according to the present invention, the steps (a) and (b) may be performed in a vacuum atmosphere.

In the brazing method according to the present invention, the holding time of the first heating step may be 10 minutes to 1 hour.

In the brazing method according to the present invention, the holding time of the second heating step may be 20 minutes or less. In the brazing method according to the present invention, the holding time of the second heating step may be 5 to 10 minutes.

In the brazing method according to the present invention, the cooling step may be performed by furnace cooling.

The brazing method of the present invention is significantly lower than the? Transition temperature of 995 占 폚 of the titanium alloy by using an Ag-Cu alloy having a melting point of about 820 占 폚 as a filler metal. Thus, at a brazing temperature of 50 占 폚 above the brazing material melting point, It is possible to prevent changes in physical properties of the titanium alloy to be bonded with molybdenum, which is a heterogeneous material, without causing a phase transformation.

In addition, the present invention has the effect of improving the wettability of a filler metal using an Ag-Cu alloy with a titanium alloy that is bonded to molybdenum, which is a dissimilar material, at the time of brazing by containing a small amount of a Ti component.

In addition, the present invention can be applied to a molybdenum-titanium alloy or filler metal, which is a heterogeneous material, by keeping it in a vacuum atmosphere at 25 to 100 ° C for about 10 minutes to 1 hour under the melting point of the Ag-Cu alloy before reaching the brazing temperature The oxide or organic material can be stably removed.

Further, the present invention can remove oxides or organic substances contained in molybdenum, titanium alloys, and filler metals when the brazing of different kinds of materials, prevent the change of the physical properties of the titanium alloys, and improve the wettability with the titanium alloys, It is possible to achieve a sound brazing bond between molybdenum and titanium alloy, which is difficult to bond.

FIG. 1 is a flow chart of a brazing method of a molybdenum and a titanium alloy according to the present invention, FIG. 2 is a photograph showing a result of evaluation of wettability between a filler metal used in the embodiment of the present invention and a molybdenum and a titanium alloy, FIG. 3 is a graph for explaining the heating and cooling process at the time of brazing according to the embodiment of the present invention, FIG. 4 is a photograph showing that a phase transformation occurs in the titanium alloy at the time of brazing according to Comparative Example 2, Sectional photograph of a brazed joint in which brazing was performed under the condition of heating to 760 占 폚 using Ag-Cu-based filler metal according to an embodiment of the present invention, holding for 30 minutes and holding at 860 占 폚 for 30 minutes, FIG. 7 is a photograph of the titanium alloy structure adjacent to the interface of FIG. 4 (a texture) and the result of the EDS analysis of the structure, Fig. 8 is a photograph showing the photograph of the filler metal tissue (③ tissue) of Fig. 4 and the EDS analysis result of this tissue, Fig. 9 is a graph showing the results of EDS analysis of the interfacial tissue FIG. 10 is a photograph showing the observation of the molybdenum texture (⑤ texture) adjacent to the interface of FIG. 4 and the EDS analysis of the structure of the molten metal Results.

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

It should also be understood that the terms or words used in the present specification and claims should not be construed in a conventional and dictionary sense and that the inventors may properly define the concept of the term to best describe its invention And should be construed in accordance with the principles and meanings and concepts consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely preferred embodiments of the present invention and do not represent all the technical ideas of the present invention, so that various equivalents And the scope of the present invention is not limited to the following embodiments.

In the present invention, 'pure metal' is a metal consisting of a single element and includes a small amount of impurities that are unintentionally and unintentionally incorporated in the manufacturing process. "Alloy" is a metal containing one or more metals or nonmetals having different properties and containing a small amount of impurities that are unintentionally and unintentionally incorporated in the manufacturing process.

1 shows a procedure of a brazing method of a molybdenum-titanium alloy according to the present invention.

As shown in the figure, a filler metal, which is an Ag-Cu alloy containing a small amount of Ti, is disposed between the molybdenum and the titanium alloy, which are different kinds of bonding materials (S10). Next, the first heating operation is performed (S20), the second heating operation is performed (S30), and the brazing metal is cooled to complete the brazing of the molybdenum and the titanium alloy, which are different materials, at step S40.

Specifically, the molybdenum, the titanium alloy, and the filler metal of S10 are as follows. The molybdenum may include pure molybdenum as well as an alloy containing molybdenum as a main component. The titanium alloy may be a Ti-Al-V alloy, but any alloy containing titanium as a main component may be used. The Ag-Cu-based filler metal may comprise 60 to 70% of Ag, 30 to 40% of Cu, and 1 to 3% of Ti, and the Ag-Cu-based filler metal may include 60 to 70% % Or less, preferably 0.1 wt% or less, more preferably 0.01 wt% or less.

In the present invention, the reason why each alloy element contained in the Ag-Cu-based filler metal is added is as follows. The Ag and Cu contents are maintained at a low melting point around 815 ° C so that the brazing can be performed at a temperature much lower than the? Phase transformation temperature of the titanium alloy of 995 ° C. When the brazing is simultaneously performed, the tensile strength of the joint is at least 400 MPa The adjusted range to allow. This is because when the temperature is outside the above range, the brazing temperature rises or the bonding strength is low, which is not suitable.

The Ti is for improving the wettability of the Ag-Cu alloy with the titanium alloy, which is the base material for bonding, because the wettability of the Ag-Cu alloy with molybdenum is poor. The reason for this is that the effect of improving the wettability is not sufficient when the content is less than 1% by weight, and the melting point is remarkably increased to about 900 캜 when the content exceeds 3% by weight. The impurities include the inevitable impurities contained in the raw material or the manufacturing process of the Ag-Cu-based filler metal.

Specifically, in the first heating operation of S20, a high purity inert gas atmosphere or a vacuum atmosphere is selected to prevent the reaction between the base material and gases such as oxygen, nitrogen, and hydrogen in the atmosphere, as in S20-1, After the filler is heated to the temperature below the melting point of the metal, it is completed by reaching the first heating time as in S20-3.

In this case, a vacuum atmosphere having a degree of vacuum of 1 10 ^-3 torr or less, preferably 1 10 ^-4 torr or less is selected as the first heating atmosphere condition. This is because efficient decomposition and removal of foreign matter adhered to the base material or the brazing material is performed.

In addition, the first heating temperature condition is that the heating temperature of the Ag-Cu-based filler metal is heated to 25 to 100 캜, preferably to 740 to 780 캜, and more preferably to 750 to 770 캜, . This is because when the heating temperature of the Ag-Cu-based filler metal is lower than 100 占 폚 below the melting point of the Ag-Cu-based filler metal, it is too low to maintain the heat of the filler metal and / If it is below 25 캜, it is too close to the melting point of the filler metal.

The first heating and holding time conditions are maintained for 10 minutes to 5 hours, preferably 20 minutes to 1 hour, and more preferably 25 minutes to 50 minutes. This is because, if the time is less than 10 minutes, the effect of uniformizing the heat distribution becomes ineffective, and if it exceeds 5 hours, the heat distribution uniformization is completed, but the energy is wasted due to the time delay.

 Specifically, in the second heating operation of S30, as in S30-1, a high purity inert gas atmosphere or vacuum atmosphere is selected to prevent the reaction between the base material and gases such as oxygen, nitrogen, and hydrogen in the atmosphere, and as in S30-2 Is heated to a temperature above the melting point of the filler metal, and is then completed by reaching a second heating time as in S30-3.

In this case, a high purity inert gas atmosphere is selected as the second heating atmosphere condition. This is because efficient decomposition and removal of foreign matter adhered to the base material or the brazing material is performed.

The second heating temperature condition is that the heating temperature of the Ag-Cu-based filler metal is heated to 25 to 100 캜 above the melting point, preferably to 840 to 880 캜, more preferably to 850 to 870 캜 . This is because when the heating temperature is lower than the melting point of 25 ° C, the filler metal is not sufficiently melted to make a sound bonding. If the heating temperature exceeds 100 ° C, the flowability of the filler metal and the bonding erosion are affected.

The second heating and holding time condition is maintained for 30 minutes or less, preferably for 5 minutes to 20 minutes, and more preferably for 5 minutes to 10 minutes. This is because the brazing joint is less stable in less than 5 minutes and less than 20 minutes in brazed joint strength.

 Specifically, the filler metal cooling of S40 is cooled by furnace cooling. This is to prevent the abrupt cooling from causing rapid shrinkage of the brazed jointed product and causing cracks in the jointed portion. For example, it is preferable that cooling is performed at a rate of 3 ° C / min to 7 ° C / min. When the temperature is slower than 3 ° C / min, the time required for the brazing bonding becomes excessive, The heat transfer of the joint portion may not be maintained uniformly, and the joint portion may be cracked.

The method of brazing a molybdenum and a titanium alloy according to the present invention comprises the steps of: (a) placing an Ag-Cu filler metal in a joining portion of molybdenum and a titanium alloy, (B) a second heating step of heating to a temperature of 25 to 100 DEG C above the melting point of the Ag-Cu-based filler metal in the first heating step and holding the same for a predetermined time, and (c) And a cooling step of cooling the Ag-Cu-based filler metal.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described more specifically with reference to FIGS. 2 to 10 through Examples and Comparative Examples of the present invention.

Composition of bonded and filler metals

In this embodiment, Ti-Al-V alloy is used as the titanium alloy 10 which is one of the base materials for brazing bonding, pure molybdenum (purity 99.95%) is used as molybdenum (1) As the metal 20, an Ag-Cu alloy was used.

For comparison with this embodiment, BNi-2 alloy (Comparative Example 1) and Ag-5Pd alloy (Comparative Example 2), which are different filler metals, were used for the base material 1, Brazing bonding was performed.

The specific chemical compositions of these base metals and filler metals are shown in Table 1 below.

Kinds Chemical composition (% by weight) Melting point join
metal Ti alloy Ti-6Al-4V-0.25Fe-0.2O 1660 ° C molybdenum Mo (purity 99.5%) 2617 ° C filler
metal Example Bal Ag-35.3Cu-1.75Ti 815 ℃ Comparative Example 1 BNi-2 1000 ℃ Comparative Example 2 Ag-5Pd 985 ° C

Evaluation of filler metal wettability

If the wettability between the bonding metal (base material) and the filler metal is poor in the brazing process as described above, not only a good bonding is achieved, but the filler metal is not completely filled in the bonding gap when the bonding gap is large, resulting in incomplete bonding.

Thus, the wettability of the molybdenum (1) and the titanium alloy (10) was evaluated as to whether or not the Ag-Cu alloy 20 used in the present example had a wettability. Specifically, in the evaluation of wettability, a filler metal piece was placed on the surface of a base material made of molybdenum and a Ti alloy, and then heated to a brazing temperature and maintained for 30 minutes. .

2, it can be seen that the wettability of the Ag-Cu alloy 20 with the molybdenum 1 is low, but the wettability with the titanium alloy 10 is very good. have. Thus, it can be seen that the good wettability with the titanium alloy 10 at the time of brazing can largely offset the low wettability with the molybdenum 1.

Brazing method

The brazing was carried out in a vacuum of 1 10 ^-4 torr through the heating and cooling method shown in FIG. For example, the upper part of the bonding metal is processed to 36 mm (width) to 40 mm (length) to 12 mm (thickness), and the lower part to 40 mm (width) to 40 mm (length) to 16 mm Milling was performed on the surface so as to have roughness. Subsequently, the bonded portion of the bonded material was degreased and pickled to be in a clean state. Then, the filler metal was adhered to the joint, and then brazing was performed by charging it into a vacuum heating furnace (vacuum degree 5 ㅧ 10 ^-5 torr or less).

Specifically, the heating was carried out for 200 minutes regardless of the type of filler metal, and the unstable temperature distribution was stably maintained, and foreign materials such as oxides and oils adhering to the surface of the base metal and the filler metal were sufficiently removed through thermal decomposition A first heating step of holding at 760 ° C for 30 minutes was carried out. At this time, in order to confirm the effect of the presence of the first heating step, it was confirmed that the brazing was performed immediately without holding at 760 ° C, and the difference between brazing after holding at 760 ° C for 30 minutes and brazing was confirmed.

After the first heating step, a method of heating to the final brazing temperature and holding it for a predetermined time (second heating step) was used. In this case, the brazing temperature was set at 50 ° C above the melting point of the filler metal. In order to confirm the influence of the holding time at the brazing temperature on the brazing bonding, the base material and the filler metal according to the present embodiment were used, Brazing was carried out at 0, 10, 20 and 30 minutes, respectively. In the cooling method, the furnace cooling method was used after the second heating step. At this time, the cooling rate per minute was about 5 ° C.

Further, in the case of Comparative Example 1, the brazing was performed three times under the condition of the first heating step of holding at 760 ° C for 30 minutes and the second heating step of holding at 1050 ° C for 30 minutes.

Further, in the case of Comparative Example 2, the brazing was performed three times under the condition of the second heating step of holding at 1035 캜 for 30 minutes after the first heating step of holding at 760 캜 for 30 minutes.

Table 2 below shows the brazing specimens subjected to the above conditions.

No. Filler metal First heating Second heating Cooling Remarks Temperature (℃) Time (minutes) Temperature (℃) Time (minutes) One Ag-Cu 760 30 860 0 Cold working Example 2 Ag-Cu 760 30 860 10 Cold working Example 3 Ag-Cu 760 30 860 20 Cold working Example 4 Ag-Cu 760 30 860 30 Cold working Example 5 Ag-Cu 760 0 860 30 Cold working Comparative Example 6 BNi-2 760 30 1050 30 Cold working Comparative Example 7 Ag-5Pd 760 30 1035 30 Cold working Comparative Example

Analysis of brazed joint tissue

In the case of Comparative Example 1, brazing was not performed. As shown in Fig. 4, the brazing temperature was as high as 1035 DEG C, and it was observed that phase transformation occurred in the titanium alloy as the base material for bonding. As a result, molybdenum and titanium It was confirmed that it is not suitable for brazing of alloys.

5 is a cross-sectional photograph of a brazed joint in which brazing is performed under the condition of heating to 760 ° C. using an Ag-Cu-based filler metal according to an embodiment of the present invention, holding for 30 minutes, and holding at 860 ° C. for 30 minutes .

Fig. 6 is a photograph showing the structure (i. E., The titanium alloy structure adjacent to the interface) of Fig. 5 and the EDS analysis result of this structure. As can be seen in FIG. 5, no phase transformation of the titanium structure was observed, and component analysis revealed that a small amount of Mo, Ag, and Cu were diffused.

FIG. 7 is a photograph showing an observation of the ② structure (that is, the interfacial structure of the titanium alloy and the filler metal) of FIG. 5 and the EDS analysis result of this structure. As can be seen from FIG. 6, a diffusion layer containing a considerable amount of Cu and Ag in the Ti alloy is observed at the interface between the titanium alloy and the filler metal.

Fig. 8 is a photograph showing the ③ structure (i.e., filler metal structure) of Fig. 5 and the EDS analysis result of this structure. As shown in Fig. 8, it is confirmed that a considerable amount of Ti and Mo are diffused into the filler metal.

9 is a photograph of the ④ texture (ie, the interfacial structure of the filler metal and molybdenum) of FIG. 5 and the EDS analysis result of this structure. As can be seen from Fig. 9, a diffusion layer in which a considerable amount of Ag, Cu and Ti are diffused into molybdenum is observed at the interface between the filler metal and the molybdenum.

FIG. 10 is a photograph showing the ⑤ texture (ie, molybdenum structure adjacent to the interface) of FIG. 5 and the EDS analysis result of this structure. As can be seen in Fig. 10, it is observed that small amounts of Ag, Cu and Ti are also diffused into the molybdenum adjacent to the interface. As a result of observation of the microstructure, it was confirmed that the bonding itself was good, and the content of Ti and Cu was relatively high at the bonding interface.

Tensile test of brazed joint

In order to evaluate the tensile properties of the joint portion of the brazing material obtained through the above brazing process, a round bar having a diameter of 10 mm was processed by a wire cutting method, and a round bar was again subjected to a tensile specimen according to ASTM E8, Tensile tests were performed using a tensile tester, and Table 3 below shows the results.

No. Filler metal The tensile strength
(MPa) Yield strength
(MPa) Elongation
(%) Remarks One Ag-Cu 423 349 0.32 Example 2 Ag-Cu 400 329 0.56 Example 3 Ag-Cu 377 275 0.49 Example 4 Ag-Cu 293 180 0.50 Example 5 Ag-Cu 269 165 0.38 Comparative Example 6 BNi-2 - - - Comparative Example 7 Ag-5Pd 460 440 0.92 Comparative Example

As shown in Table 3, the tensile test of the brazing material showed the best tensile properties in the case of the test piece No. 7, which was brazed according to the comparative example 2. However, since it causes phase transformation in the titanium alloy, It is difficult to use for brazing of alloys.

In the case of Specimen No. 5 in which the same base metal and filler metal as in the present embodiment were used and brazing was performed immediately at the brazing temperature without the first heating step, the specimen No. The tensile strength of the joint is lower than that of specimens Nos. 1 to 3, as well as the tensile strength of the joint is remarkably low. Therefore, it can be seen that the first heating step in the brazing of molybdenum and titanium alloy is advantageous in improving the brazing property compared to the case in which the first heating step is not performed.

The specimen No. 4, which was held for 30 minutes in the second heating step, had a lower tensile strength at the joint portion than the specimens Nos. 1 to 3 maintained at 0, 10 and 20 minutes in the second heating step, It is considered that as the holding time increases, the compound is formed at the junction and the weaker phase increases with time.

On the other hand, Specimen No. 1 having no holding time in the second heating step is advantageous in terms of bonding strength but is disadvantageous in terms of realizing stable brazing bonding. Therefore, when considering the stability of the brazing joint and the aspect of the bonding strength, the holding time in the second heating step is most preferably 5 minutes to 20 minutes.

When the Ag-Cu brazing material having a melting point as low as about 815 to 820 DEG C is used in the dissimilar metal brazing joint between the molybdenum and the titanium alloy of the present invention from such Examples and Comparative Examples, And that when the Ag-Cu brazing material contains a small amount of Ti, the wettability with the titanium alloy may be improved, which may be advantageous for brazing, and that when heating for brazing When the brazing material is heated to the brazing temperature after being kept at a temperature of 25 to 100 ° C. for a certain time under the melting point of the brazing material, the foreign matter adhering to the surface of the brazing material or the base material is effectively removed before the brazing is performed, It can be seen that a suitable surface state can be obtained.

1: molybdenum 10: titanium alloy
20: filler metal

Claims (7)

(a) a first heating step of disposing an Ag-Cu filler metal at a junction of molybdenum and a titanium alloy, heating the alloy to a temperature of 25 to 100 캜 below the melting point of the Ag-Cu-based filler metal and holding the alloy for a predetermined time;
(b) a second heating step of heating the Ag-Cu-based filler metal to a temperature in the range of 25 to 100 占 폚 over a melting point of the Ag-Cu-based filler metal in a first heating step; And
(c) a cooling step of cooling the Ag-Cu-based filler metal by furnace cooling,
Ag is brazed at a melting point of 815 캜, which is lower than 995 캜, which is the β-phase transformation temperature of the titanium alloy, and when the brazing is further brazed, the tensile strength of the joint is 400 MPa or more And the Cu is brazed at a melting point of 815 캜 which is lower than the β-phase transformation temperature of the titanium alloy at a temperature of 815 캜. When the brazing is performed, the tensile strength of the welded portion is 30 to 40% And Ti is 1 to 3%, which is not more than 3% by weight, which is higher than 1% by weight, in which the wettability improving effect is insufficient,
≪ / RTI > wherein the molybdenum and titanium alloys are brazed.
The method according to claim 1,
Wherein the molybdenum is pure molybdenum or a molybdenum alloy.
The method according to claim 1,
Wherein the holding time of the first heating step is 10 minutes to 1 hour.
The method according to claim 1,
Wherein the holding time of the second heating step is 20 minutes or less.
The method according to claim 1,
And the holding time of the second heating step is 5 minutes to 10 minutes.
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