KR102368282B1 - Clad materials for hermetic sealing of electronic components and method for the manufacture thereof - Google Patents

Abstract

An object of the present invention is to provide a clad material for airtight sealing of electronic components, comprising Kovar and a silver brazing material, which is excellent in punching workability, and a method for manufacturing the same. On the surface of the Kobar layer, the area ratio of the austenite phase occupied in the total area of the Kobar crystal grains calculated from the crystal phase distribution measurement by the electron beam backscattering diffraction method is 99.0 to 100.0%, and the average of the Kobar crystal grains The crystal grain size is set to 0.5 to 3.5 µm.

Description

Clad material for hermetic sealing of electronic components and manufacturing method thereof

The present invention relates to a clad material for hermetic sealing of electronic components and a method for manufacturing the same. In detail, it relates to a clad material for hermetic sealing of electronic components excellent in punching workability, and to a method for manufacturing the same.

Kovar is an Fe-Ni-Co alloy developed by Westinghouse of the United States, and since its thermal expansion characteristics match that of hard glass or ceramics over a wide temperature range, it is an optimal material for hermetic sealing of hard glass or ceramics. is known as Therefore, the sealing ring and lead which clad silver-type lead on the kovar are widely used as a hermetic sealing material of electronic components, such as a ceramic package.

The seal ring or lead clad with silver-based solder in kovar is usually manufactured by punching a thin clad plate made of kovar and silver-based brazing material. It has not always been easy to efficiently mass-produce the seal ring or lead by processing. Moreover, with the recent miniaturization of electronic devices, the request|requirement for the improvement of the punching processability of a clad material is increasing more and more.

Therefore, in view of this situation, research on a clad material made of Kovar and a silver-based brazing material with improved punching workability is in progress. Integration of crystal planes (200), (111), (220), (311) of the austenite phase and crystal planes (110), (200), (211) of the martensite phase in the X-ray diffraction diagram when measured by X-ray diffraction The ratio of the sum of the integrated strengths of the crystal planes 110, 200, and 211 of the martensite phase to the total strength is 0.5% or more and 10% or less, and the ratio of the sum of the integrated strengths of the martensite phase is 0.5% or more 10 % or less, a sealing material excellent in press punchability is reported, characterized in that the region of the depth is within 10% of the total thickness in the thickness direction from the planar outermost surface of the Fe-Ni-Co alloy sheet side. (Patent Document 1).

Based on the knowledge that the clad material described in Patent Document 1 has an effect of suppressing the generation of burrs by making it easier for the martensite phase introduced to the surface of the plate material to proceed to fracture during press punching processing, Fe-Ni-Co alloy It is characterized in that the amount of martensite phase from the outermost surface of the planar surface of the plate material to a specific depth is adjusted within a specific range. And, in patent document 1, cold rolling is performed on the plate|board material plane of a Fe-Ni-Co type|system|group with respect to the adjustment of a martensitic phase, and as a method other than carrying out using work-induced transformation and rolling, for example, surface grinding|polishing, , that a process-induced martensite phase can be produced also by methods, such as shot peening, is described.

Japanese Patent No. 3531814 Publication

In the prior art disclosed in Patent Document 1, an austenite phase of Kovar is rolled in a low-temperature region using an industrial cold rolling apparatus, and the temperature and reduction ratio at the time of rolling are controlled, thereby processing-induced transformation into a martensitic phase. to refine the crystal grains. And by refining the crystal grains, the punching workability of the clad material is improved.

However, as in the prior art, when crystal grains are refined by work hardening by rolling the clad material, martensite phase with good punching workability increases, but the thermal expansion coefficient, which is characteristic of Kovar, is greatly changed. there is a risk of throwing it away.

In addition, when the clad material is refined only by rolling processing, the thickness of the clad material that can be worked is limited or the processing process is limited depending on the cold rolling apparatus used. Mass production at a processing rate is not necessarily easy from the point of view of equipment.

In view of this situation, the subject of the present invention is for the hermetic sealing of electronic components, which can be mass-produced at a high processing rate and made of Kovar and silver brazing material, which can be mass-produced at a high processing rate, and has excellent punching workability while maintaining the thermal expansion coefficient, which is the original characteristic of Kovar. To provide a clad material and a method for manufacturing the same.

As a result of earnest examinations to solve the above problems, the present inventors do not refine crystal grains by work hardening as in the prior art, but perform heat treatment (300 to 600° C.) again after cold rolling following heat treatment. , found that the punching workability of the clad material was improved by achieving refinement of crystal grains while maintaining the state of the austenite phase with little or no induction of the martensite phase, and thus completed the present invention.

That is, the present invention is a clad material for hermetic sealing of electronic components having a silver-based brazing material layer and a Kovar layer,

On the surface of the Kobar layer, the area ratio of the austenite phase to the total area of the Kobar crystal grains calculated from the crystal phase distribution measurement by the electron beam backscattering diffraction method is 99.0 to 100.0%, and the average of the Kovar crystal grains It is a clad material for hermetic sealing of an electronic component whose crystal grain diameter is 0.5-3.5 micrometers.

Another aspect of the present invention relates to a method for manufacturing the clad material, that is,

A first step of bonding the silver-based brazing material layer and the Kovar layer to form a laminate;

a second step of heat-treating and cold rolling the laminate;

3rd process of heat-processing the said laminated body again following the 2nd process

It is a manufacturing method of the clad material for hermetic sealing of an electronic component containing.

According to the present invention, excellent punching workability (free machinability) while maintaining high sealing reliability because the crystal grains are refined in a state in which the austenite phase is maintained with no or almost no martensite phase. It becomes possible to provide the provided clad material for hermetic sealing of an electronic component. In addition, unlike the method of achieving refinement of crystal grains based on work hardening by rolling processing of clad materials as in the prior art, there are no significant restrictions on the performance of cold rolling equipment, etc., so mass production of various clad materials at a high working rate is it becomes possible

As described above, the clad material for hermetic sealing of electronic components according to the present invention (hereinafter referred to as "clad material") has a silver-based brazing material layer and a Kovar layer. And in the clad material, the area ratio of the austenite phase to the total area of the Kobar grains calculated from the crystal phase distribution measurement by the electron beam backscattering diffraction method on the surface of the Kobar layer is 99.0 to 100.0%, and It is characterized in that the average crystal grain size of the crystal grains is 0.5 to 3.5 μm. According to the present invention, since the crystal grains of the austenite phase are refined while the austenite phase is maintained without causing a phase change in the Kovar layer of the clad material by having these characteristics, according to the present invention, sealing reliability and punching workability It becomes possible to obtain a clad material exhibiting excellent performance from the viewpoint of

The silver-based brazing material constituting the silver-based brazing material layer is not particularly limited as long as it is a brazing material containing silver as a main component, for example, silver-copper alloy (copper concentration of 10 to 30 mass%), silver-copper-tin alloy (copper concentration of 20 -40 mass %, tin concentration 1-40 mass %), silver-copper-indium alloy (copper concentration 20-40 mass %, indium concentration 1-40 mass %), silver-copper-zinc alloy (copper concentration 20-40 mass %) mass %, zinc concentration 1-40 mass %) is mentioned. In addition, the thickness of the silver-based brazing filler metal layer is usually 0.01 to 0.1 mm.

As described above, Kovar constituting the Kovar layer is a Fe-Ni-Co alloy, and its composition is Fe (54 mass %), Ni (29 mass %), Co (17 mass %), Si, Trace amounts of Mn and the like are included. In addition, the thickness of the Kovar layer is usually 0.1 to 0.6 mm.

As described above, in the clad material of the present invention, the austenite occupied by the total area of the Kovar grains is calculated from the crystal phase distribution measurement by the electron beam backscattering diffraction method (EBSD (electron backscattering diffraction) method) on the surface of the Kobar layer. It is characterized in that the ratio of the area of the phase (γ:fcc) is 99.0 to 100.0%. This means that the clad material is an austenite single phase, or that the martensitic phase (α′:bcc) generated by processing-induced martensitic transformation during rolling is less than 1%. In the present invention, when the area ratio of the austenite phase is less than 99.0%, it becomes difficult for the clad material to obtain good punching workability, and since the martensite phase increases, there is a fear that the coefficient of thermal expansion is significantly changed.

In addition, the clad material of the present invention is characterized in that the average grain size of Kovar grains is 0.5 to 3.5 µm. Preferably, a clad material having an average grain size of Kovar grains of 0.7 to 3.4 µm is used. When the average grain size of the Kovar grains is outside the range of 0.5 to 3.5 µm, it becomes difficult to obtain high punching workability.

In this invention, in order to calculate the area ratio of the austenite phase which occupies in the total area of a Kobar crystal grain from the crystal phase distribution measurement by the electron beam backscattering diffraction method, it carries out normally as follows.

First, the surface of the Kovar layer of the clad material to be measured is subjected to surface treatment such as mechanical polishing or electrolytic polishing to remove minute irregularities based on the rolling pattern or the like. Next, the structure of the surface is observed using the scanning electron microscope attached to the EBSD, the orientation of all pixels within a predetermined measurement area on the surface of the Kovar image is measured at a step size of 0.1 µm, and the orientation difference between adjacent pixels is A boundary of 15° or more is regarded as a grain boundary, and a grain is specified in the measurement area. Subsequently, by counting the number of pixels in the grains of the austenite phase and multiplying the area per pixel, the area per each grain of the austenite phase is calculated, and the total area of the grains of the austenite phase can be obtained by summing them. Similarly, the total area of the crystal grains of the martensite phase can be calculated. Then, the area ratio (%) of the austenite phase is calculated by dividing the total area of the crystal grains of the austenite phase obtained in this way by the total area of the crystal grains of the austenite phase and the martensite phase and multiplying by 100.

In addition, what is necessary is just to measure the average grain size of a Kovar crystal grain based on JISG0551. Specifically, according to the cutting method, the surface of the Kovar phase of the clad material is subjected to surface treatment such as mechanical polishing to make the crystal grains easy to observe, and then, after the EBSD is attached to the metal structure of the Kovar layer, the scanning electron Take a picture using a microscope, draw a line using a pen or the like along the grain boundary of the photographed metal structure to make the grain boundary visible, draw two orthogonal straight lines to measure the number of grains cut by these lines, Then, by measuring the length of these lines and inserting their length and the number of crystal grains into a predetermined formula, the average particle diameter of Kovar crystal grains is computed.

The clad material of the present invention can be made into a multilayered structure of three or more layers by forming an intermediate layer between the silver-based brazing filler metal layer and the Kovar layer and/or on the Kovar layer within the range that does not impair punching workability.

The clad material is processed by normal punching, that is, a die having a hole shape formed in the outline shape of a desired airtight sealing material (for example, a seal ring or a lead) of an electronic component, and a mold comprising a punch fitted into the hole shape. By punching using a press machine, the hermetic sealing material of the electronic component of a predetermined shape is obtained. The clad material of the present invention is particularly preferably used for manufacturing a hermetic sealing material for electronic components, and particularly preferably for manufacturing a seal ring. When punching is performed, it is preferable to perform punching in the direction from the Kovar layer to the silver-based brazing filler metal layer in order to obtain good punchability.

Next, the manufacturing method of the clad material which concerns on this invention is demonstrated. The manufacturing method includes a first step of bonding a silver brazing material layer and a Kovar layer to form a laminate, a second step of heat-treating and cold rolling the laminate, and a second step, followed by heat treatment of the laminate again It is characterized in that it includes a third process.

In the first step, the silver-based brazing material layer and the Kovar layer are joined to form a laminate, but the specific method is not particularly limited. Generally, first, plate materials constituting each layer of the silver-based brazing material layer and the Kovar layer are prepared, respectively, and their surfaces are appropriately polished to homogenize, and then the silver-based brazing material layer and the Kovar layer are laminated, for example For example, after welding the periphery, cold pressing is performed for bonding, or, for example, a laser is irradiated to the abutting surface of the silver-based brazing material layer and the Kovar layer, and cold pressing is performed for bonding. A laminate is formed by bonding all or part of the bonding surfaces of the

Next, as a 2nd process, heat processing and cold rolling are performed with respect to the said laminated body obtained by the 1st process. Usually, the heat treatment is performed in the range of 500 to 800° C. for 1 to 60 minutes, and then cooled to room temperature and cold rolling is performed. By performing such heat treatment and cold rolling, bonding is ensured and a highly reliable laminate is obtained.

Finally, as the third step, following the second step, heat treatment and, if necessary, cold rolling are performed on the laminate again. Thereby, the clad material of the present invention excellent in punching workability can be obtained. The heat treatment performed in the third step is 300 to 600°C, preferably 400 to 550°C, and requires to be performed for 1 to 60 minutes. If the temperature is outside the range of 300 to 600°C, the crystal grains become coarse and the grain refinement is not sufficiently performed, so the punching workability does not improve, and a large amount of martensite phase is generated, making it difficult to maintain the Cobar's coefficient of thermal expansion. There are concerns. In the case of performing the cold rolling, if the reduction ratio at one time is 30% or more, there is a risk of cracks occurring in the welded portion or the like. Therefore, the reduction ratio at one time is preferably less than 30%.

After performing the heat treatment, it is preferable to perform cold rolling for the purpose of adjusting the performance or thickness. However, in order to prevent the formation of the martensite phase, the reduction ratio in this case is preferably less than 20%.

In this way, industrially, a clad material excellent in punching workability, in which the area ratio of the austenite phase to the total area of the Kovar grains is 99.0 to 100.0%, and the average grain size of the austenite phase is 0.5 to 3.5 µm, is industrially produced. can be provided stably.

Hereinafter, the present invention will be described in more detail by way of Examples. In addition, this invention is not limited to these.

Example

(Examples 1 to 6, Comparative Examples 1 to 4)

A silver-based brazing material (silver-85 mass% copper alloy) having a width of 15 mm and a thickness of 0.40 mm in a Kovar layer made of a Kovar alloy (product name: NAS29CO, manufactured by Nippon Yakin Corporation) having a width of 15 mm and a thickness of 1.5 mm The brazing filler metal layer was clad and heat-treated under the conditions shown in Table 1 {heat treatment (1)}, cooled to room temperature, and rolled at the reduction ratio shown in Table 1 to prepare a clad base material {rolling (1)}. Next, the clad base material was heat-treated again under the conditions shown in Table 1 {heat treatment (2)}, cooled to room temperature, and rolled at the reduction ratio shown in Table 1 {rolling (2)} to prepare a clad material. At this time, the thickness of the Kovar layer was 0.15 mm, and the thickness of the silver-based brazing material layer was 0.04 mm.

The rolled surface (surface) of the prepared Kovar layer of the clad material is wet-polished and electropolished to a mirror-finished state, and at a depth of 5 μm from the surface, electron beam backscattering diffraction (EBSD) is used to perform the EBSD system. Using a scanning electron microscope having (manufactured by Texem Laboratories, trade name: OIM System) (manufactured by Nippon Denshi Corporation, trade name: JSM-6500F), the average grain size of Kovar grains, and the austenite phase and martensite phase The grain area was measured. Regarding the measurement area, it was carried out in the range of 30 µm × 30 µm, a boundary with a difference in orientation between adjacent pixels of 15° or more was regarded as a grain boundary, and the scanning interval was set to step distance = 0.1 µm. The crystal grains were defined as having a crystal orientation difference of 15° or more. The austenite phase and the martensitic phase were distinguished by comparison of the crystal orientation map obtained by the EBSD method and the optical micrograph, and each of the austenite phase and the martensitic phase was confirmed in the optical micrograph. On the other hand, the average grain size of the Kobar crystal was calculated using the JIS standard (JIS G0551). Table 2 shows the results regarding the average grain size (µm) and the area ratio (%) of the austenite phase to the total grain area of the austenite phase and the martensite phase.

Further, using a 5 mm round mold, using a press machine (manufactured by Best Company), the clearance between the punch and the die was set to 5 µm, and the Kovar layer side of each cladding material according to Examples 1 to 6 and Comparative Examples 1 to 4 was used. A press test of vertical punching in the direction of the silver-based brazing filler metal layer was performed. The press test was performed at a pressing speed of 1 mm / s, and the maximum stress during pressing (N / mm 2 ) and the stress change at the end of punching from the maximum stress value were calculated as the stress difference (N / mm 2 ) from the maximum stress value. calculated.

In addition, the fracture surface after pressing was evaluated by observing the presence or absence of cracks and burrs (things of 8 µm or more) on the fracture surface using an optical microscope, respectively. Table 2 shows the evaluation results.

(Evaluation results)

As shown in Table 2, in the clad materials of Examples 1 to 4, the area ratio of the austenite phase on the surface of the Kobar layer was 99.3% or more, and the average crystallinity was higher than that of the clad materials of Comparative Examples 1 and 2. The Kovar layer was composed of Kovar grains with a small particle size. Further, as a result of the press test, it was confirmed that the clad materials of Examples 1 to 4 exhibited good press-punching workability because the difference in stress was small and no burrs were generated.

Claims (8)

It is a clad material for hermetic sealing of electronic components, which has a silver-based brazing material layer and a Kovar layer,
On the surface of the Kovar layer, the area ratio of the austenite phase to the total area of the Kovar crystal grains calculated from the crystal phase distribution measurement by the electron beam backscattering diffraction method is 99.0 to 100.0%, and the average of the Kovar crystal grains A clad material for hermetic sealing of electronic components, having a crystal grain size of 0.5 to 3.5 µm. According to claim 1,
A clad material for hermetic sealing of electronic components, used for manufacturing a seal ring. 3. The method of claim 1 or 2,
A clad material for hermetic sealing of electronic components, which is used for punching from the Kovar layer to the silver-based brazing material layer. It is a hermetic sealing material formed by punching a clad material for hermetic sealing of electronic components having a silver-based brazing material layer and a Kovar layer,
On the surface of the Kovar layer, the area ratio of the austenite phase to the total area of the Kovar crystal grains calculated from the crystal phase distribution measurement by the electron beam backscattering diffraction method is 99.0 to 100.0%, and the average of the Kovar crystal grains A hermetic sealing material having a crystal grain size of 0.5 to 3.5 µm. 5. The method of claim 4,
A hermetic sealing material formed by punching from the Kovar layer to the silver-based brazing material layer. 6. The method according to claim 4 or 5,
The hermetic sealant is a seal ring. A method for manufacturing a clad material for hermetic sealing of electronic components, which has a silver-based brazing material layer and a Kovar layer,
A first step of bonding the silver-based brazing material layer and the Kovar layer to form a laminate;
A second step of heat-treating and cold-rolling the laminate;
a third process of heat-treating the laminate again following the second process;
On the surface of the Kovar layer, the area ratio of the austenite phase to the total area of the Kovar crystal grains calculated from the crystal phase distribution measurement by the electron beam backscattering diffraction method is 99.0 to 100.0%, and the average of the Kovar crystal grains having a crystal grain size of 0.5 to 3.5 μm,
A method for manufacturing a clad material for hermetic sealing of electronic components. 8. The method of claim 7,
A method for producing a clad material for hermetic sealing of an electronic component, wherein the heat treatment in the second step is performed in a range of 500 to 800°C, and the heat treatment in the third step is performed in the range of 300 to 600°C.