CN115717242B - Method for chemically thinning and flattening titanium foil - Google Patents
Method for chemically thinning and flattening titanium foil Download PDFInfo
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- CN115717242B CN115717242B CN202310033284.3A CN202310033284A CN115717242B CN 115717242 B CN115717242 B CN 115717242B CN 202310033284 A CN202310033284 A CN 202310033284A CN 115717242 B CN115717242 B CN 115717242B
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Abstract
The invention discloses a method for chemically thinning and flattening titanium foil, relates to the field of semiconductor preparation, and aims to prepare a wrinkle-free titanium foil soldering lug; the key points of the technical scheme are as follows: a method for chemically thinning and flattening a titanium foil is characterized by comprising the following steps: s1: degreasing and cleaning the surface of the titanium foil, and ultrasonically cleaning the titanium foil with the thickness of 10 to 15 mu m and the width of 140 to 150mm to remove oil stains and impurities on the surface for later use; s2: titanium foil pretreatment, namely placing the titanium foil treated in the step S1 in liquid nitrogen under normal pressure for supercooling treatment, and soaking for 30-60min; s3: thinning the titanium foil, namely transferring and immersing the titanium foil processed in the step S2 in an HNO3/HF mixed solution for chemical thinning etching, wherein the thinning time is 30-60S, and the transferring time is 3-5S; s4: the surface is cleaned again and vacuum dried. The method for chemically thinning and flattening the titanium foil can obtain the wrinkle-free ultrathin titanium foil soldering lug.
Description
Technical Field
The invention relates to the technical field of semiconductor preparation, in particular to a method for chemically thinning and flattening a titanium foil.
Background
The AMB (Active Metal Brazing) process is a further development of the DBC process technology, and is a method for realizing the joint of ceramics and metals by utilizing the reaction of Active metals and ceramics to generate a reaction layer which can be wetted by liquid Brazing filler metals. Compared with the DBC technology, the ceramic copper-clad substrate obtained by the AMB method is better in thermal conductivity and insulation reliability, has more excellent thermal cycle reliability, and is more suitable for being used in high-voltage and high-power semiconductor devices.
The soldering lug/solder is one of the cores of the AMB technology, wherein the soldering lug is a Ti foil soldering lug mainly comprising an active element Ti, when the soldering lug is sintered at high temperature, an interface reaction will occur between copper and ceramic, the interface reaction is weak, the bonding strength of a product is not high, and copper-ceramic bonding cannot be realized; if the interface reaction is too strong, the interface reaction layer is too thick, which also causes the product performance to be reduced, and the selection of a proper soldering lug is very important. The thickness of the Ti foil welding piece is an important control factor, the mature rolling process is mainly used for producing foils with the thickness of more than or equal to 10 micrometers, the thickness of the Ti foil welding piece for active metal brazing is about 2-5 micrometers, and within the range, the thinner the Ti foil welding piece is, the higher the copper-ceramic bonding strength is, the better the performance is. At present, a rolling process is adopted to produce Ti foil soldering lugs with the width of 132-150mm and the thickness of 2-5 microns, the yield is low, and the cost is increased greatly compared with soldering lugs with the thickness of 10 microns.
The chemical thinning process of the Ti foil provides an idea for producing ultrathin soldering lugs, the prior chemical thinning method of the Ti foil still mainly takes a hydrofluoric acid/fluoride object system as a main object, wherein HF/HNO3 is mainly used as the main object, after the system is chemically thinned, the surface of the Ti foil is easy to wrinkle at present, so that AMB sintering stability is poor, the voidage of a copper-ceramic bonding interface of the Ti foil is unstable, bad hidden dangers exist, the interface voidage can influence the insulating strength of a ceramic substrate under extreme conditions, and device failure can be caused under serious conditions.
In the field of ceramic copper-clad substrates, the preparation of wide, ultrathin (less than 10 mu m) and wrinkle-free Ti foil soldering lugs based on the use of an AMB (advanced micro electro mechanical system) process is in urgent need of development.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for chemically thinning and flattening a titanium foil, which can be used for preparing a wrinkle-free and ultrathin titanium foil soldering lug.
The technical purpose of the invention is realized by the following technical scheme: a method for chemically thinning and flattening a titanium foil comprises the following steps:
s1: degreasing and cleaning the surface of the titanium foil, and ultrasonically cleaning the titanium foil with the thickness of 10-15 mu m and the width of 140-150mm to remove oil stains and impurities on the surface for later use;
s2: titanium foil pretreatment, namely placing the titanium foil treated in the step S1 in liquid nitrogen under normal pressure for supercooling treatment, and soaking for 30-60min;
s3: thinning the titanium foil, namely taking the titanium foil treated in the step S2, transferring and immersing the titanium foil in an HNO3/HF mixed solution for chemical thinning etching, wherein the thinning time is 30-60S, and the transferring time is 3-5S;
s4: the surface is cleaned again and vacuum dried.
By adopting the technical proposal, the utility model has the advantages that,
the invention is further configured to: in the S3 step, the HNO3/HF mixed solution contains 3-5% by mass of HF, 25-30% by mass of HNO3, and the balance of pure water.
By adopting the technical proposal, the utility model has the advantages that,
the invention is further configured to: in the step S3, the titanium foil soldering lug is thinned, the thickness is 4.5-6.0 mu m, and the width is 140-150mm.
The invention is further configured to: in step S4, the vacuum drying is carried out, the drying temperature is 70-100 ℃, the heat preservation is 20-40min, the heating rate is 10-15 ℃/min, and the vacuum degree is 50-100Pa.
The invention is further configured to: in step S1, the ultrasonic cleaning includes pure water ultrasonic cleaning and absolute ethanol ultrasonic cleaning.
The invention is further configured to: and S4, carrying out secondary water washing on the titanium foil, carrying out ultrasonic cleaning on the titanium foil by using absolute ethyl alcohol after water washing, and finally carrying out vacuum drying on the titanium foil.
The invention is further configured to: in the step S2, after soaking, the space is pressurized to be more than or equal to 10MPa, and then transportation is carried out.
The invention is further configured to: the chemical thinning etching temperature is 30 to 35 ℃.
In conclusion, the invention has the following beneficial effects: the method comprises the following steps of firstly, carrying out surface oil removal cleaning on the surface of the titanium foil to ensure that no obvious impurities exist on the surface of the titanium foil, carrying out pretreatment on the titanium foil by using a titanium foil soldering lug, namely carrying out supercooling treatment on the titanium foil by using liquid nitrogen, changing the internal structure and the stress state of the titanium foil in a low-temperature environment, being beneficial to keeping the processing stress in the soldering lug in the thinning process and reducing wrinkles; the optimal proportion is optimized to obtain an HNO3/HF mixed solution with the optimal HNO3 content, the titanium foil thinning process is smooth, and the surface microstructure is smooth; in conclusion, the preparation method of the chemically thinned and flattened titanium foil provided by the invention integrally eliminates the wrinkling condition of the chemically thinned titanium foil, is obviously beneficial to AMB sintering stability, and reduces the risk of devices.
Drawings
FIG. 1 is a schematic flow diagram of the present invention;
FIG. 2 is an SEM micrograph of a thinned titanium foil of example one;
FIG. 3 is an SEM micrograph of a thinned titanium foil of comparative example I;
FIG. 4 is a scan of the ultrasonic bonding interface after sintering of a thinned titanium foil AMB according to an embodiment;
fig. 5 is a scan of the ultrasonic bonding interface after sintering of the thinned titanium foil AMB of comparative example.
Detailed Description
The invention is described in detail below with reference to the figures and examples.
Referring to the attached drawing 1, the main steps of chemically thinning and flattening the titanium foil include degreasing and cleaning the surface of the titanium foil, then performing pretreatment on the titanium foil, thinning the titanium foil, and finally performing surface cleaning and drying.
The first embodiment is as follows: a preparation method of a chemically thinned and flattened titanium foil comprises the following steps:
s1: degreasing and cleaning the surface of the titanium foil;
and (3) sequentially carrying out water washing ultrasonic cleaning and absolute ethyl alcohol ultrasonic cleaning on the titanium foil with the thickness of 10 mu m and the width of 140mm to remove oil stains and impurities on the surface for later use.
S2: pretreating a titanium foil;
and (3) placing the titanium foil treated in the step (S1) in liquid nitrogen for supercooling treatment at normal pressure, and soaking for 30min.
S3: thinning the titanium foil;
and (3) taking the titanium foil processed in the step (S2), rapidly transferring and immersing the titanium foil in HNO3/HF mixed solution for chemical thinning etching under the high-pressure environment and the environmental pressure of 10MPa, wherein the thinning time is 30S, and the transferring time is 3S.
S4: cleaning the surface;
and (4) taking the titanium foil obtained in the step (S3), washing the titanium foil for the second time, ultrasonically cleaning the titanium foil by using absolute ethyl alcohol after washing, and finally drying the titanium foil in vacuum.
Wherein the HNO3/HF mixed solution comprises 3% of HF, 30% of HNO3, the balance of pure water, a chemical thinning etching temperature of 35 ℃, and a titanium foil tab having an average thickness of 4.7 μm and a width of 140mm after thinning.
In step S4, the vacuum drying is carried out, the drying temperature is 80 ℃, the heat preservation time is 20min, the heating rate is 10 ℃/min, and the vacuum degree is 100Pa under low vacuum.
The second embodiment: a preparation method of a chemically thinned and flattened titanium foil comprises the following steps:
s1: degreasing and cleaning the surface of the titanium foil;
and (3) sequentially carrying out water washing ultrasonic cleaning and absolute ethyl alcohol ultrasonic cleaning on the titanium foil with the thickness of 15 mu m and the width of 140mm to remove oil stains and impurities on the surface for later use.
S2: pretreating a titanium foil;
and (3) placing the titanium foil treated in the step (S1) in liquid nitrogen for supercooling treatment at normal pressure, and soaking for 30min.
S3: thinning the titanium foil;
and (3) taking the titanium foil processed in the step (S2), rapidly transferring and immersing the titanium foil in HNO3/HF mixed solution for chemical thinning etching under the high-pressure environment and the environmental pressure of 15MPa, wherein the thinning time is 40S, and the transferring time is 3S.
S4: cleaning the surface;
and (4) taking the titanium foil obtained in the step (S3), washing the titanium foil for the second time, ultrasonically cleaning the titanium foil by using absolute ethyl alcohol after washing, and finally drying the titanium foil in vacuum.
Wherein the HNO3/HF mixed solution comprises 5% of HF, 30% of HNO3, and pure water as balance, the chemical thinning etching temperature is 35 deg.C, and the titanium foil bonding sheet has an average thickness of 5.3 μm and a width of 140mm after being thinned.
In step S4, the vacuum drying is carried out, the drying temperature is 80 ℃, the heat preservation time is 20min, the heating rate is 10 ℃/min, and the vacuum degree is 100Pa under low vacuum.
Comparative example one: the preparation method of the thinned titanium foil comprises the following steps:
s1: degreasing and cleaning the surface of the titanium foil;
and sequentially washing the titanium foil with the thickness of 15 mu m and the width of 140mm by using water washing ultrasonic waves and absolute ethyl alcohol ultrasonic waves to remove oil stains and impurities on the surface for later use.
S2: thinning the titanium foil;
and (4) taking the titanium foil processed in the step (S2), rapidly transferring and immersing the titanium foil in an HNO3/HF mixed solution for chemical thinning etching, and taking out the titanium foil with the thinning time of 45S.
S4: cleaning the surface;
and (4) taking the titanium foil obtained in the step (S3), carrying out secondary water washing on the titanium foil, carrying out ultrasonic cleaning on the titanium foil by using absolute ethyl alcohol after water washing, and finally carrying out vacuum drying on the titanium foil.
Wherein the HNO3/HF mixed solution comprises 5% of HF, 10% of HNO3, and pure water as balance, the chemical thinning and etching temperature is 35 ℃, and the titanium foil soldering lug has an average thickness of 5.5 μm and a width of 140mm after being thinned;
in step S4, the vacuum drying is carried out, the drying temperature is 80 ℃, the heat preservation time is 20min, the heating rate is 10 ℃/min, and the vacuum degree is 100Pa under low vacuum.
The following compares the performance of the first, second and first comparative examples:
referring to fig. 2 and 3, fig. 2 is a SEM micrograph of the first example showing a significantly smooth surface, while fig. 3 is a SEM micrograph of the first comparative example showing a rough surface; fig. 4 and 5 are scans of the ultrasonic bonding interface after AMB sintering in example one and comparative example one, fig. 4 being able to meet the sintering requirement, while fig. 5 is unable to meet the sintering requirement.
The above description is only a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above embodiments, and all technical solutions that belong to the idea of the present invention belong to the scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.
Claims (8)
1. A method for chemically thinning and flattening a titanium foil is characterized by comprising the following steps:
s1: degreasing and cleaning the surface of the titanium foil, and ultrasonically cleaning the titanium foil with the thickness of 10-15 mu m and the width of 140-150mm to remove oil stains and impurities on the surface for later use;
s2: titanium foil pretreatment, namely placing the titanium foil treated in the step S1 in liquid nitrogen under normal pressure for supercooling treatment, and soaking for 30-60min;
s3: thinning the titanium foil, namely taking the titanium foil treated in the step S2, transferring and immersing the titanium foil in an HNO3/HF mixed solution for chemical thinning etching, wherein the thinning time is 30-60S, and the transferring time is 3-5S;
s4: the surface is cleaned again and vacuum dried.
2. A method for chemically thinning and flattening titanium foil according to claim 1, characterized in that: in the S3 step, the HNO3/HF mixed solution has the ingredients including 3-5% by mass of HF, 25-30% by mass of HNO3, and the balance pure water.
3. A method of chemically thinning a flattened titanium foil as claimed in claim 2 wherein: in the step S3, the titanium foil soldering lug is thinned to have the thickness of 4.5-6.0 mu m and the width of 140-150mm.
4. A method for chemically thinning and flattening titanium foil according to claim 1, characterized in that: in step S4, the vacuum drying is carried out, the drying temperature is 70-100 ℃, the heat preservation is 20-40min, the heating rate is 10-15 ℃/min, and the vacuum degree is 50-100Pa.
5. A method of chemically thinning a flattened titanium foil as claimed in claim 1, wherein: in step S1, the ultrasonic cleaning includes pure water ultrasonic cleaning and absolute ethyl alcohol ultrasonic cleaning.
6. The method of chemically thinning a flattened titanium foil as claimed in claim 4, wherein: and S4, carrying out secondary water washing on the titanium foil, carrying out ultrasonic cleaning on the titanium foil by using absolute ethyl alcohol after the water washing, and finally carrying out vacuum drying on the titanium foil.
7. A method for chemically thinning and flattening titanium foil according to claim 1, characterized in that: in the step S2, after soaking, the space is pressurized to be more than or equal to 10MPa, and then transportation is carried out.
8. A method of chemically thinning a flattened titanium foil as claimed in claim 3 wherein: the chemical thinning etching temperature is 30 to 35 ℃.
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| CN202310033284.3A CN115717242B (en) | 2023-01-10 | 2023-01-10 | Method for chemically thinning and flattening titanium foil |
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| CN202310033284.3A CN115717242B (en) | 2023-01-10 | 2023-01-10 | Method for chemically thinning and flattening titanium foil |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4370192A (en) * | 1980-10-20 | 1983-01-25 | American Microsystems, Inc. | Apparatus for chemical etching of silicon |
| EP0201910A1 (en) * | 1985-05-14 | 1986-11-20 | Inland Steel Company | Diffusion alloy steel foil |
| US5222282A (en) * | 1992-01-13 | 1993-06-29 | Texas Instruments Incorporated | Method for reducing thickness of a high-strength low-ductility metal foil on thin strip element |
| JP2001303223A (en) * | 2000-04-24 | 2001-10-31 | Sumitomo Metal Ind Ltd | Method for manufacturing titanium sheet excellent in formability |
| CN111785643A (en) * | 2020-06-12 | 2020-10-16 | 江苏富乐德半导体科技有限公司 | Titanium foil chemical thinning method |
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2023
- 2023-01-10 CN CN202310033284.3A patent/CN115717242B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4370192A (en) * | 1980-10-20 | 1983-01-25 | American Microsystems, Inc. | Apparatus for chemical etching of silicon |
| EP0201910A1 (en) * | 1985-05-14 | 1986-11-20 | Inland Steel Company | Diffusion alloy steel foil |
| US5222282A (en) * | 1992-01-13 | 1993-06-29 | Texas Instruments Incorporated | Method for reducing thickness of a high-strength low-ductility metal foil on thin strip element |
| JP2001303223A (en) * | 2000-04-24 | 2001-10-31 | Sumitomo Metal Ind Ltd | Method for manufacturing titanium sheet excellent in formability |
| CN111785643A (en) * | 2020-06-12 | 2020-10-16 | 江苏富乐德半导体科技有限公司 | Titanium foil chemical thinning method |
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