A processing technique suitable for TVS decks
By directly forming a glass passivation layer on TVS chips using screen printing technology, the problems of complex and environmentally unfriendly existing processes are solved, achieving a simple and efficient tabletop treatment and improving production efficiency and product reliability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BESTBRIGHT ELECTRONICS
- Filing Date
- 2026-02-28
- Publication Date
- 2026-06-26
Smart Images
Figure CN122294974A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of transient voltage suppressor diode (TVS) manufacturing technology, and in particular to a processing technology suitable for TVS mesa. Background Technology
[0002] TVS (Transient Voltage Suppressor) diodes are widely used in consumer electronics, automotive electronics, industrial control, and communication equipment as highly efficient circuit protection devices. During TVS manufacturing, glass passivation is typically used to protect the chip surface to achieve an ideal electric field distribution and long-term stability at the PN junction edge region. After passivation, a window needs to be created on the glass layer to facilitate subsequent metallization and other processes.
[0003] The currently prevalent mesa processing technology in the industry is a combination of photolithography and chemical etching. Its core process is: glass coating → glass passivation → resist coating → exposure → development → hard baking → HF acid wet etching → resist removal. The working principle of this process is as follows: a photoresist mask with a specific mesa pattern is formed on the surface of the glass passivation layer through secondary resist coating and photolithography. Then, HF acid is used to wet-etch the glass areas not protected by the photoresist. Finally, the photoresist is removed and the surface is cleaned to obtain the desired mesa. However, the existing technology has the following drawbacks: 1. The process is complex, involving at least several steps such as coating, pre-baking, exposure, development, post-baking, etching, coating removal, and cleaning. It is highly dependent on production equipment (such as spin coaters, lithography machines, wet etching tanks, etc.), with high investment and maintenance costs and a long production cycle. 2. HF acid is extremely corrosive and toxic, posing a significant threat to human health and safe production. Its storage, use, and waste liquid treatment all require strict special management and high investment, which is not in line with the development trend of green manufacturing. 3. The process control requirements are stringent. The photolithography process is extremely sensitive to environmental cleanliness, temperature and humidity, and exposure alignment accuracy, which can easily lead to defects such as incomplete development, film damage, and pattern distortion. In addition, the uniformity of HF wet etching and lateral drilling are difficult to control precisely, which may affect the mesa size accuracy and edge morphology, posing a potential risk to the consistency of the final electrical performance parameters of the device (such as breakdown voltage and leakage current). 4. Photoresist is a disposable consumable, and HF acid is continuously consumed during the etching process, resulting in material waste. HF acid is also continuously consumed during the etching process, increasing material costs.
[0004] Therefore, there is an urgent need for a TVS countertop treatment process that is simplified, low-cost, safe, environmentally friendly, and easy to control, in order to overcome the above-mentioned shortcomings. Summary of the Invention
[0005] The purpose of this invention is to provide a TVS (Transformer of Sealing and Static Electricity) surface treatment process that is simplified, low-cost, safe, environmentally friendly, and easy to control, in order to overcome many problems caused by the secondary photolithography and HF wet etching processes in the prior art. The solution of this invention is as follows: A processing technique for TVS countertops includes the following steps: S1. Provide TVS chip substrates that have completed diffusion to form PN junctions and alloying processes; S2. Using a pre-designed screen printing plate, pour glass paste onto the screen printing plate and smooth it with a squeegee. Under the pressure of the squeegee, the glass paste is selectively coated onto the pre-designed grooves and areas to be covered on the substrate surface to form a wet film pattern consistent with the cutout pattern of the screen printing plate. S3. Dry the printed substrate at low temperature to remove some of the organic solvents in the glass paste, so that the wet film pattern can be initially set. S4. Place the pre-dried substrate in a high-temperature sintering furnace and perform heat treatment according to a temperature curve that includes debinding, sintering, and cooling stages. This causes the organic binder in the glass slurry to volatilize or decompose, and the glass powder particles to melt, flow, and densify, forming a firmly adhered glass passivation layer on the surface of the semiconductor substrate. S5. The unprinted countertop areas are naturally exposed, completing the countertop treatment.
[0006] In step S2, the cutout pattern of the screen printing plate corresponds to the area on the chip where the glass passivation layer needs to be formed, and the uncut area of the screen printing plate corresponds to the mesa area in the chip design.
[0007] In step S2, the glass paste is composed of a mixture of glass powder and an organic carrier, which is a mixture of binder and solvent used to adjust the printing performance of the glass paste.
[0008] The overall technical solution of the present invention is as follows: using screen printing technology, glass paste is directly and selectively coated onto pre-planned mesa and trench areas on a semiconductor substrate, and then cured by one-time high-temperature sintering, simultaneously realizing the patterning and passivation functions of the glass layer, thereby completely eliminating the complex and dangerous steps such as secondary coating, photolithography, HF wet etching, and resist removal in traditional processes.
[0009] Compared with the prior art, the overall process steps of this invention are as follows: In the existing technology (before improvement): glass coating → glass passivation → adhesive coating → exposure → development → hard baking → HF acid wet etching → adhesive removal; The process of this invention (after improvement): Glass coating (screen printing) → Glass passivation Compared with the prior art, the distinguishing technical features of the present invention are as follows: 1. Existing technology uses a "subtractive process"; that is, first uniformly cover the entire area with a glass layer and a protective adhesive layer, then define the pattern through photolithography, and finally etch away the unwanted parts with HF acid; the present invention uses an "additive process"; that is, only add (print) glass material directly at the required location to form the desired pattern in one step, avoiding material waste and complicated pattern transfer and removal steps.
[0010] 2. Existing technologies rely on "photochemical patterning," which uses the photosensitive reaction and development of photoresist to form a temporary mask. This method offers high pattern precision but is complex and costly. This invention, however, relies on "physical mask patterning," which uses a screen printing plate with a fixed pattern to directly deposit the paste. Once the screen printing plate is made, it can be reused tens of thousands of times, simplifying the pattern definition process to a single printing action.
[0011] 3. Existing technologies require the use of high-risk or specialized chemicals such as photoresist, HF acid, or BOE etching solution and resist remover, as well as precision and complex equipment such as photolithography machines, spin coaters, and wet etching equipment. The core material of this invention is glass paste (composed of glass powder, organic carriers, etc.), and the core equipment is a screen printing machine and a high-temperature sintering furnace. It completely eliminates the use of photoresist and HF acid.
[0012] 4. The traditional multiple steps of "coating → pre-baking → exposure → development → post-baking → HF etching → adhesive removal → cleaning" are simplified into three main steps: "screen printing → pre-baking → sintering". The production cycle is significantly shortened, the equipment investment and maintenance costs are greatly reduced, and the safety, health and environmental risks brought by HF acid are completely eliminated.
[0013] Beneficial effects:
[0014] 1. It eliminates multiple complex processes such as secondary photolithography, HF acid etching, and resist removal, reducing the number of process steps by more than 40%. The operation process is simple, and the requirements for environmental conditions and operator skill level are significantly reduced, making it easier to achieve process standardization in large-scale production. At the same time, through the precise design and direct positioning of the screen template, no additional alignment operation is required, reducing the risk of error accumulation caused by the superposition of processes, and making the molding accuracy easier to control.
[0015] 2. This invention adopts a precision printing method, reducing material waste rate to below 5%, which is a significant saving compared to the material loss rate of about 30% in traditional processes. It also eliminates the procurement and storage costs of expensive chemicals such as photoresist and HF acid. The purchase cost of screen printing equipment is only 1 / 10 to 1 / 20 of that of photolithography equipment, and no additional environmental protection equipment is required, making equipment maintenance convenient. In terms of labor, after the process steps are simplified, the number of operators required for a single production line is reduced by more than 30%, significantly reducing labor costs.
[0016] 3. Traditional HF acid etching easily leads to defects such as burrs and defects on the mesa edges. However, this invention directly forms the mesa through screen printing, avoiding damage to the passivation layer caused by chemical etching. The mesa edges are smooth and the contours are clear, significantly improving structural integrity. This allows the device breakdown voltage consistency error to be controlled within ±2% (compared to ±5% to ±8% for traditional processes), and surge current withstand capability is improved by more than 15%. At the same time, the screen template dimensional accuracy is stable over a long period, and printing parameters are easy to control precisely. The mesa dimensional error between different batches of products can be controlled within ±0.02mm, greatly improving product consistency. Furthermore, there is no chemical residue on the mesa surface, and the printed glass layer bonds more tightly to the substrate. The device's lifespan in high temperature and high humidity environments is extended by more than 20%, significantly improving long-term operational reliability.
[0017] 4. This invention completely eliminates the use of toxic and harmful chemicals such as HF acid, avoiding the safety risks and environmental pressures brought about by their storage, use and waste liquid treatment. There is no emission of toxic and harmful substances, reducing environmental protection investment and conforming to the green, safe and sustainable development trend of modern manufacturing industry.
[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 This is a schematic diagram of the process flow of the present invention.
[0021] Figure 2 This is a schematic diagram of the process of screen printing according to the present invention.
[0022] Figure 3 This is a schematic diagram of the process after coating the glass slurry according to the present invention. Detailed Implementation
[0023] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.
[0024] The components of the embodiments of the invention described and shown in the accompanying drawings can typically be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.
[0025] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0026] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0028] like Figure 1-3 As shown, a processing method for TVS countertops according to the present invention includes the following steps: S1. Provide TVS chip substrates that have completed diffusion to form PN junctions and alloying processes; S2. Using a pre-designed screen printing plate, pour glass paste onto the screen printing plate and smooth it with a squeegee. Under the pressure of the squeegee, the glass paste is selectively coated onto the pre-designed grooves and areas to be covered on the substrate surface to form a wet film pattern consistent with the cutout pattern of the screen printing plate. S3. Dry the printed substrate at low temperature to remove some of the organic solvents in the glass paste, so that the wet film pattern can be initially set. S4. Place the pre-dried substrate in a high-temperature sintering furnace and perform heat treatment according to a temperature curve that includes debinding, sintering, and cooling stages. This causes the organic binder in the glass slurry to volatilize or decompose, and the glass powder particles to melt, flow, and densify, forming a firmly adhered glass passivation layer on the surface of the semiconductor substrate. S5. The unprinted countertop areas are naturally exposed, completing the countertop treatment.
[0029] Furthermore, in step S2, the cutout pattern of the screen printing plate corresponds to the area on the chip where the glass passivation layer needs to be formed, and the uncut area of the screen printing plate corresponds to the mesa area in the chip design.
[0030] Furthermore, in step S2, the glass paste is composed of a mixture of glass powder and an organic carrier, which is a mixture of binder and solvent used to adjust the printing performance of the glass paste.
[0031] Furthermore, in step S2, the squeegee pressure during screen printing is 0.1-0.5MPa, the angle between the squeegee and the screen is 30-60°, the printing speed is 50-200mm / s, and the spacing between the screen and the substrate is 0.1-0.5mm.
[0032] Furthermore, in step S3, the pre-drying temperature is 80-150℃, and the holding time is 10-30 minutes.
[0033] Furthermore, in the high-temperature sintering and curing process of step S4: The temperature during the glue removal stage is 300-500℃, and the holding time is 10-30 minutes; The sintering temperature is 600-900℃, and the holding time is 20-60 minutes. During the cooling phase, the temperature is reduced to room temperature at a rate of 5-15℃ / min.
[0034] Furthermore, in step S2, the size error of the cutout pattern on the screen printing plate is controlled within ±0.01mm, and the mesh count of the screen printing plate is 200-500 meshes.
[0035] To more clearly illustrate the technical solution of this invention, two implementable examples are provided below: Example 1: A novel TVS countertop treatment process, the specific steps of which are as follows: S1. Substrate preparation: Select silicon-based TVS chip substrates that have completed the diffusion to form PN junctions and alloying processes. Remove oil and impurities from the substrate surface using plasma cleaning equipment to ensure surface cleanliness. S2. Screen Printing: The glass paste is prepared by mixing glass powder and an organic carrier in a mass ratio of 7:3. The organic carrier is a mixture of ethyl cellulose and terpineol. A 300-mesh screen is selected, with a cutout pattern size error of ±0.008mm, accurately corresponding to the chip trench and the area to be covered. The screen printing process parameters are set as follows: squeegee pressure 0.3MPa, squeegee and screen angle 45°, printing speed 100mm / s, and screen and substrate distance 0.3mm. The glass paste is selectively coated on the substrate surface to form a preset wet film pattern. S3. Pre-drying: Place the printed substrate into a forced-air drying oven and keep it at 120℃ for 20 minutes to remove organic solvents such as terpineol from the paste and allow the wet film to be initially set. S4. High-temperature sintering and curing: Place the pre-dried substrate in a box-type sintering furnace and process it according to the following temperature curve: heat up to 400℃ at a rate of 10℃ / min and hold for 20min (resin removal stage); continue to heat up to 750℃ and hold for 40min (sintering stage); finally cool to room temperature at a rate of 10℃ / min (cooling stage) to form a dense glass passivation layer, and the tabletop area is naturally exposed.
[0036] Glass powder particles melt, flow, and densify, forming good adhesion and wetting with the surface of the semiconductor substrate, ultimately forming a strong, dense, insulating glass layer with good passivation effect.
[0037] Testing revealed that the TVS devices prepared using the process described in this embodiment have smooth, burr-free mesa edges, a dimensional error of ±0.015mm, a breakdown voltage consistency error of ±1.8%, and surge current withstand capability that is 18% higher than that of products prepared using traditional processes. Furthermore, the production process produces no toxic or harmful substances and has a material waste rate of only 3%.
[0038] Example 2: A novel TVS countertop treatment process, the specific steps of which are as follows: S1. Substrate preparation: Provide silicon carbide-based TVS chip substrates that have completed the necessary semiconductor processes, which are ultrasonically cleaned with deionized water and then dried for later use. S2. Screen Printing: The glass paste is prepared by mixing glass powder and an organic carrier at a mass ratio of 6:4. The organic carrier is a mixture of polyvinyl acetate and ethanol. A 400-mesh screen is selected, and the size error of the cutout pattern is ±0.005mm. The screen printing process parameters are: squeegee pressure 0.2MPa, squeegee-screen angle 50°, printing speed 80mm / s, and screen-substrate spacing 0.2mm, to achieve selective coating of the glass paste. S3. Pre-drying: Place the substrate in a vacuum drying oven and hold at 100℃ for 25 minutes to complete the wet film setting. S4. High-temperature sintering and curing: Place the substrate in a tube sintering furnace, raise the temperature at a rate of 8℃ / min, raise it to 350℃ and hold for 25 minutes (adhesive removal stage); continue to raise the temperature to 800℃ and hold for 30 minutes (sintering stage); cool to room temperature at a rate of 8℃ / min (cooling stage) to complete the table surface treatment.
[0039] The test results show that the TVS device prepared in this embodiment has a mesa size error of ±0.01mm, a breakdown voltage consistency error of ±1.5%, a surge current withstand capability improved by 20%, and a material waste rate of 2.5%, which meets the performance requirements of high voltage TVS devices.
[0040] This invention is mainly applied to the mesa molding manufacturing of transient voltage suppressor diodes (TVS). It is suitable for the production of TVS devices of various power levels, such as low voltage, medium voltage, and high voltage, and various packaging forms such as surface mount and through-hole. It can be widely used in the mass production of TVS devices in consumer electronics, automotive electronics, industrial control, communication equipment, new energy and other fields. It is especially suitable for large-scale production scenarios with high requirements for production efficiency, cost control and product reliability.
[0041] This invention creatively changes the formation method of TVS glass passivation tabletop by introducing screen printing, a direct forming additive process. It replaces the complex, dangerous, and expensive photochemical-chemical etching combination process with a simple, safe, and economical physical printing, which is a fundamental innovation in the field.
[0042] This embodiment does not impose any limitation on the shape, material, structure, etc. of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.
Claims
1. A process for processing a TVS deck, characterized by, Includes the following steps: S1. Provide TVS chip substrates that have completed diffusion to form PN junctions and alloying processes; S2. Using a pre-designed screen printing plate, pour glass paste onto the screen printing plate and smooth it with a squeegee. Under the pressure of the squeegee, the glass paste is selectively coated onto the pre-designed grooves and areas to be covered on the substrate surface to form a wet film pattern consistent with the cutout pattern of the screen printing plate. S3. Dry the printed substrate at low temperature to remove some of the organic solvents in the glass paste, so that the wet film pattern can be initially set. S4. Place the pre-dried substrate in a high-temperature sintering furnace and perform heat treatment according to a temperature curve that includes debinding, sintering, and cooling stages. This causes the organic binder in the glass slurry to volatilize or decompose, and the glass powder particles to melt, flow, and densify, forming a firmly adhered glass passivation layer on the surface of the semiconductor substrate. S5. The unprinted countertop areas are naturally exposed, completing the countertop treatment.
2. The process for a TVS deck according to claim 1, wherein, In step S2, the cutout pattern of the screen printing plate corresponds to the area on the chip where the glass passivation layer needs to be formed, and the uncut area of the screen printing plate corresponds to the mesa area in the chip design.
3. The process for a TVS deck according to claim 1, wherein, In step S2, the glass paste is composed of a mixture of glass powder and an organic carrier, which is a mixture of binder and solvent used to adjust the printing performance of the glass paste.
4. The process for processing a TVS deck as claimed in claim 1, wherein, In step S2, the squeegee pressure during screen printing is 0.1-0.5MPa, the angle between the squeegee and the screen is 30-60°, the printing speed is 50-200mm / s, and the spacing between the screen and the substrate is 0.1-0.5mm.
5. The process for processing a TVS deck as claimed in claim 1, wherein, In step S3, the pre-drying temperature is 80-150℃, and the holding time is 10-30 min.
6. The process for processing a TVS deck as claimed in claim 1, wherein, In the high-temperature sintering and curing process of step S4: The temperature during the glue removal stage is 300-500℃, and the holding time is 10-30 minutes; The sintering temperature is 600-900℃, and the holding time is 20-60 minutes. During the cooling phase, the temperature is reduced to room temperature at a rate of 5-15℃ / min.
7. The process for processing a TVS deck as claimed in claim 1, wherein, In step S2, the size error of the cutout pattern on the screen printing plate is controlled within ±0.01mm, and the mesh count of the screen printing plate is 200-500 mesh.