WO2023011228A1

WO2023011228A1 - Thermal print head substrate having composite lead-free protective layer and method for manufacturing same

Info

Publication number: WO2023011228A1
Application number: PCT/CN2022/107563
Authority: WO
Inventors: 徐继清; 王吉刚; 陈文卓; 山科佳弘
Original assignee: 山东华菱电子股份有限公司
Priority date: 2021-08-06
Filing date: 2022-07-25
Publication date: 2023-02-09
Also published as: CN114379240A; CN114379240B; JP2024517391A

Abstract

Disclosed are a thermal print head substrate having a composite lead-free protective layer and a method for manufacturing same. The thermal print head substrate is provided with an insulating substrate (1), a heat storage and preservation ground enamel layer (2), an electrode layer (3), a heating resistor layer (4), and a protective layer (5). The protective layer comprises at least two sub-protective layers, wherein the sub-protective layer close to the insulating substrate is a first protective layer (5A), and a second protective layer (5B) is compounded on the outer side of the first protective layer; the thermal expansion coefficients of the first protective layer and the second protective layer are 50×10^-7/°C-70×10^-7/°C, and the expansion coefficient of the second protective layer is less than or equal to the expansion coefficient of the first protective layer; the first protective layer has a Vickers hardness of 600-900 HV; and a glass enamel composition of the first protective layer comprises the following components in percentage by mass: 5-15% of B₂O₃, 25-50% of Al₂O₃, 5-30% of SiO₂, and 10-30% of glass fluxing agents, wherein the glass fluxing agents are BaO, ZnO, and CaO. The thermal print head substrate is lead-free, wear-resistant, and corrosion-resistant.

Description

Thermal print head substrate with composite lead-free protective layer and manufacturing method thereof

technical field

The embodiment of the present application relates to the technical field of thermal print head manufacturing, for example, a thermal print head substrate with a composite lead-free protective layer and a manufacturing method thereof, which has the characteristics of lead-free, wear-resistant, and corrosion-resistant.

Background technique

As we all know, the thermal print head includes a substrate made of insulating and heat-resistant materials. The substrate is provided with an underglaze layer for heat storage. The underglaze layer and the surface of the substrate are provided with wire electrodes, and a heating resistor layer is provided on the electrode surface to generate heat. The resistive body layer is covered with a protective layer.

The manufacturing process of the protective layer of the relevant thermal print head is as follows: select the protective layer slurry prepared by lead-containing silicate material, apply thick film technology such as printing or spraying to the surface of the heating resistor body layer and the electrode layer, and use belt sintering Furnace or box-type sintering furnace for sintering; after sintering, a dense film layer is formed. For related thermal print heads, PbO is often added to the wear-resistant protective layer as a sintering flux, thereby reducing the softening point of the glass, so that a glass glaze fired at a lower temperature can be realized. The glass glaze with lead oxide as a sintering aid has a wide firing temperature range and excellent sintering film quality, and has excellent comprehensive performance, and has been widely used; however, lead is an element that is not friendly to humans and the environment ,Not environmentally friendly. With the gradual enhancement of people's awareness of environmental protection, the toxicity of lead to humans and the pollution of the environment have attracted more and more attention from all aspects; lead-containing substances are discarded in electronic products.

Generally, some flux is added to the metal electrode paste for thick-film thermal printheads to reduce its sintering temperature. The firing temperature range of thick-film protective layer pastes commonly used for related thermal printheads is about 600-850°C. Ordinary lead-free silicate protective layer often lacks the fluxing effect of PbO, and its firing temperature is generally above 850°C, resulting in the incompatibility of related thick-film conductor pastes with related lead-free glass processes, so low-melting lead-free silicon The development of salt glass becomes very necessary.

The related lead-free glass system usually has the following characteristics: the low-melting lead-free glass of the phosphate system is relatively complex and there is a contradiction between the linear expansion coefficient and its chemical stability; the vanadate glass has a layered structure, which is easy to absorb water and form bubbles; Boron oxide in low-melting borosilicate lead-free glass can improve the thermal and chemical stability of the glass, reduce the high-temperature viscosity during sintering, have better high-temperature fluidity, and can form a denser film layer, thus being widely used research and promotion.

The related lead-free protective glass is generally made of borosilicate glass materials; boron oxide and silicon oxide are used as the glass skeleton, which has excellent chemical stability, but borosilicate glass often uses li ₂ O, Na Alkali metal oxides such as ₂ O and K ₂ O are used as fluxes. Due to their high viscosity at high temperature, the fluidity of the glass after melting is poor, and the surface of the film after firing is relatively rough; moreover, due to its insufficient hardness and weak wear resistance, it cannot handle Abrasion of thermal paper. In order to improve the physical hardness of lead-free silicate glass, alumina or other high-hard substance fillers are often added to the borosilicate base glass, but alumina or other high-hard substance fillers do not enter the glass network, which brings negative effects. The effect is that the internal network structure of the silicate protective layer becomes loose, its chemical stability decreases, acid and alkali resistance and water erosion resistance become poor, and it is difficult to meet the corrosion resistance requirements of the thermal print head protective layer. Application No. 201910933628.X reduces the content of Al ₂ O ₃ fillers and increases the content of SiO2, that is, increases the ratio of glass skeleton composition SiO ₂ : filler Al ₂ O ₃ content; thereby improving its compactness to improve its insulation and corrosion resistance; but When applied to the field of protective layer of thermal print head, often due to the low proportion of its internal high-hard filler Al ₂ O ₃ compared with glass skeleton SiO ₂ and B ₂ O ₃ , etc., resulting in insufficient wear resistance, a solution to wear and corrosion resistance Lead-free protective layer materials and structures become very necessary.

Contents of the invention

The following is an overview of the topics described in detail in this article. This summary is not intended to limit the scope of the claims.

The embodiment of the present application proposes a thermal print head substrate with a composite lead-free protective layer and a manufacturing method thereof, which can effectively improve the corrosion resistance and wear resistance of the insulating substrate, thereby ensuring the service life of the thermal print head.

The embodiment of the present application achieves through the following measures:

A thermal printing head substrate with a composite lead-free protective layer is provided with an insulating substrate, and the surface of the insulating substrate is sequentially provided with a heat storage and heat preservation underglaze layer, an electrode layer formed of a metal material, and a heating resistor formed of a semiconductor material. body layer and a corrosion-resistant and wear-resistant protective layer; the protective layer includes at least two sub-protective layers, wherein the sub-protective layer close to the insulating substrate is the first protective layer, and the second protective layer is compounded outside the first protective layer; The coefficient of thermal expansion of the first protective layer and the second protective layer is 50×10 ^-7 /°C-70×10 ^-7 /°C, and the expansion coefficient of the second protective layer is less than or equal to the expansion coefficient of the first protective layer;

The Vickers hardness of the first protective layer is 600-900HV, and the glass glaze composition of the first protective layer includes the following components in mass percentage: B ₂ O ₃ 5-15%; Al ₂ O ₃ 25-50% ; The content range of SiO ₂ is 5-30%; the content of glass flux is 10-30%, and the glass flux is BaO, ZnO and CaO.

In the glass glaze composition of the first protective layer described in the embodiment of the present application, in terms of the total mass percentage of the composition: B ₂ O ₃ 8-13%; Al ₂ O ₃ 40-45%; SiO ₂ content range 21-30% %.

In the glass glaze composition used to form the first protective layer in the embodiment of the present application, the glass flux is calculated by the total mass percentage of the composition, the content of BaO is in the range of 3-8%, and the content of ZnO is in the range of 2-6%. , the CaO content ranges from 5-20%.

In the embodiment of this application, in order to improve the hardness and wear resistance of the glass film layer, a certain content of Al ₂ O ₃ is often added as an internal filler; the Al ₂ O ₃ is spherical or flake Al ₂ O ₃ with a particle size of about 0.1-1 μm; When the content of Al ₂ O ₃ is too high, the surface roughness of the film layer is high, and the adhesion of the film layer is poor; when the content of Al ₂ O ₃ is too low, the hardness is insufficient and the wear resistance is weak.

The glass glaze composition of the second protective layer described in the embodiment of the present application comprises the following components, in terms of mass percentage: the content of B ₂ O ₃ is 10-30%, the content of Al ₂ O ₃ is 20-50%, and the content of SiO ₂ The range is 30-50%, and the glass enamel flux content is 1-5%, and the glass enamel flux is Na ₂ O and K ₂ O.

Furthermore, the glass glaze composition of the second protective layer described in the examples of the present application is based on the total mass percentage of the composition: the content of boron oxide B ₂ O ₃ is 10-30%, and the content of aluminum oxide Al ₂ O ₃ is 25-40% , SiO ₂ content in the range of 40-45%, the content of Na ₂ O in the glass glaze flux is 2.5-5%, and the content of K ₂ O is 0-5%.

The embodiment of the present application also has a third protective layer, the third protective layer is compounded on the outside of the second protective layer, the third protective layer is an ultra-high hardness protective layer formed of carbide, nitride or silicide, and the physical characteristic is Vickers Hardness ≥ 1200Hv.

The first protective layer and the third protective layer described in the embodiments of the present application partially or completely cover the effective area of the electrode layer.

The embodiment of the present application also proposes a method for manufacturing a thermal print head substrate with a composite lead-free protective layer as described above. After the first protective layer in the composite protective layer is sintered, the surface is planarized. After the treatment, Surface roughness ≤ 0.2 μm; the surface planarization treatment is to use a polishing abrasive belt made of aluminum oxide or silicon carbide with a particle size of 500-3000 mesh and a particle size of <50 μm for polishing; the polished product is cleaned, dried, and completed. The first protective layer is prepared, and then the second protective layer glass glaze composition slurry is printed and sintered on the outside of the first protective layer to form the second protective layer.

The embodiment of the present application also includes using magnetron sputtering or other processes to prepare high hardness carbide or nitride to the effective area of the third protection layer on the outside of the second protection layer to form the third protection layer.

The method for manufacturing a thermal print head substrate with a composite lead-free protective layer described in the embodiment of the present application specifically includes:

Step 1: sequentially prepare a thermal storage base glaze layer, a metal electrode layer, and a heating resistor layer on the surface of the insulating substrate; then print the first protective layer slurry on the heating resistor area, dry, and sinter to form the first protective layer;

Step 2: Use surface smoothing process, that is, use 3000 mesh, aluminum oxide or silicon carbide polishing abrasive belt with a particle size of about 5 μm for reciprocating polishing and grinding; the polished product is cleaned on the surface, using absolute ethanol as the cleaning medium Ultrasonic cleaning is carried out; the cleaned product is dried at 80-120°C;

Step 3: Printing, drying and sintering of the second protective layer on the treated substrate. Step: Print the second protective layer slurry on the electrode-coverable area to form the second protective layer and the corrosion-resistant protective layer.

Compared with the related technology in this application, the first lead-free protective layer is made of wear-resistant silicate glass with higher Webster hardness, and the second lead-free protective layer is made of lead-free silicate with better water resistance and moisture erosion Glass preparation, the third protective layer is an ultra-high hardness protective layer. This application can effectively deal with corrosion damage caused by corrosive or high-humidity environments. Three different functional protective layers provide wear protection, corrosion resistance protection and scratch resistance respectively. Injury protection, thereby improving product reliability.

Other aspects will be apparent to others upon reading and understanding the drawings and detailed description.

Description of drawings

The accompanying drawings are used to provide a further understanding of the technical solutions herein, and constitute a part of the description, and are used together with the embodiments of the application to explain the technical solutions herein, and do not constitute limitations to the technical solutions herein.

Accompanying drawing 1 is a kind of structural sectional view of the embodiment of the present application.

Accompanying drawing 2 is another structural sectional view of the embodiment of the present application.

Accompanying drawing 3 is the sectional view of the third structure of the embodiment of the present application.

Accompanying drawing 4 is the corrosion resistance preservation performance comparison of different lead-free protective layers in embodiment 1.

Accompanying drawing 5 is the wear resistance comparison of different lead-free protective layers in embodiment 3.

Accompanying drawing 6 is the comparison diagram of wear of the protective layer for different protective layers at equal distances in Example 3.

Reference signs: 1 alumina ceramic substrate, 2 bottom insulation glaze layer, 3 metal electrode layer, 4 heating resistor body layer, 5A first protective layer, 5B second protective layer, 5C third protective layer.

Detailed ways

The present application will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1 and Figure 2, this application provides a thermal printhead substrate with a composite lead-free protective layer, an insulating substrate is provided, and the surface of the insulating substrate is sequentially provided with a thermal storage and heat preservation underglaze layer, An electrode layer formed of a metal material, a heating resistor layer formed of a semiconductor material, and a corrosion-resistant and wear-resistant protective layer; the protective layer includes at least two sub-protective layers, wherein the sub-protective layer close to the insulating substrate is the first protective layer , the second protective layer is compounded on the outside of the first protective layer; the thermal expansion coefficient of the first protective layer and the second protective layer is 50×10 ^-7 /°C-70×10 ^-7 /°C, and the thermal expansion coefficient of the second protective layer less than or equal to the thermal expansion coefficient of the first protective layer;

The above setting is because the thermal print head usually uses alumina ceramic substrate as the base insulating substrate, and its thermal expansion coefficient is 68×10 ^-7 /°C-78×10 ^-7 /°C. In order to match the thermal expansion coefficient of the underlying insulating substrate, reduce the Stress brought by thermal shock caused by heating and cooling; therefore, its thermal expansion coefficient is slightly lower than that of the substrate, which is 50×10 ^-7 /℃-70×10 ^-7 /℃.

Because it is difficult for the related lead-free borosilicate glass to have both excellent acid and alkali resistance and water corrosion resistance, as well as excellent wear resistance, polarization often occurs; and the silicate used as the protective layer of the thermal print head Glass often deals with high humidity, ionized environments, and the abrasion of large granular substances in heat-sensitive paper;

In response to this phenomenon, the present application uses a certain amount of boron oxide in high borosilicate glass to form a stable and dense glass network; thereby improving its chemical stability, but its physical hardness is often low and its wear resistance is poor. Use its strong chemical stability as the second protective layer with corrosion resistance function, in which CaO, BaO, ZnO and alumina fillers are added to borosilicate glass, and Ca0-B ₂ O ₃ -SiO ₂ is used as the main crystal phase Ceramic glass phase (referred to as CBS ceramic glass phase), Ba0-B ₂ O ₃ -SiO ₂ ceramic glass phase as the main crystal phase, fine crystal particles are precipitated on the surface, thereby improving its strength and physical hardness; thereby improving its wear resistance ; but due to the addition of Al ₂ O ₃ , Al ³⁺ has a larger nuclear charge and preferentially combines with free oxygen, which reduces the number of boron-oxygen tetrahedrons and increases the number of boron-oxygen triangles, making the glass network structure loose, resulting in Its chemical stability decreases; and due to the addition _of _Al2O3 , its high-temperature viscosity increases, causing its fluidity to decrease, and it is often difficult to form a dense, high-smooth film; the application utilizes its high physical hardness and film strength as a The first protective layer for wear-resistant functions.

The Vickers hardness of the first protective layer described in this application is 600-900HV, and the glass glaze composition of the first protective layer comprises the following components, in terms of mass percentage: B ₂ O ₃ 5-15%; Al ₂ O ₃ 25- 50%; SiO ₂ content range 5-30%; glass flux: BaO, ZnO, CaO content 10-30%; the Al ₂ O ₃ is used as a wear-resistant filler in the first protective layer, using spherical or flake oxidation Aluminum Al ₂ O ₃ , the particle size is about 0.1-1μm; in order to improve the hardness and wear resistance of the glass film layer, alumina is often added as an internal filler; when the alumina content is too high, the surface roughness of the film layer is high and the film The layer bonding force is poor; when the alumina content is too low, its hardness is insufficient and the wear resistance is insufficient.

As shown in Table 1 below, in order to improve the hardness and wear resistance of the glass film, a certain amount of alumina is added as an internal filler; when the alumina content is too high, the surface roughness of the film layer is high and the film bonding force is poor; When it is too low, the hardness is insufficient and the wear resistance is insufficient. The alumina content ranges from 25-50%, which has a relatively low surface roughness, usually <0.4μm, and a high Vickers hardness, usually >600Hv.

As shown in Table 2 below, CaO and BaO are doped to form a CaO-B ₂ O ₃ -SiO ₂ ceramic glass phase (CBS glass for short) and Ba0-B ₂ O ₃ -SiO ₂ ceramic glass phase (BBS glass phase for short); It has good two-phase eutecticity in the range of 1-30% addition; it can precipitate CaSiO ₃ and BaSiO ₃ fine grains, thereby improving its film strength.

Table 1 Comparison of hardness, surface roughness and wear amount of different compositions

Table 2 Comparison of hardness, surface roughness, and wear amount of different CaO contents in the first protective layer of this application

The glass glaze composition of the second protective layer comprises the following components, in terms of mass percentage: the content of boron oxide B ₂ O ₃ is 10-30%; the content of aluminum oxide Al ₂ O ₃ is 20-50%; silicon dioxide The SiO ₂ content ranges from 30-50%; the glass glaze flux content is 1-5%, and the glass glaze flux is Na ₂ O, K ₂ O;

As shown in Table 3 below; Na ₂ O and K ₂ O as fluxes can provide free oxygen to transform the boron-oxygen triangle into a boron-oxygen tetrahedron; thereby changing the structure of boron from a layered structure to a framework structure, Thus creating conditions for the formation of a dense and uniform glass structure. When the boron oxide content is 10-30%, the protective film layer has excellent chemical stability, and its acid and alkali resistance and water erosion resistance are relatively good. When the boron oxide content is too much or too little, too many boron-oxygen triangles are formed inside, and the glass network structure is destroyed, thereby reducing its chemical stability.

Table 3 Weight loss comparison of acid and alkali resistance and water erosion resistance of different compositions

The application also has a third protective layer, the third protective layer is compounded on the outside of the second protective layer, the third protective layer is an ultra-high hardness protective layer formed of carbide, nitride or silicide, and its physical characteristics are Vickers hardness ≥ 1200Hv; the first protective layer and the third protective layer can not only cover the upper part of the heating resistor, but also partially or completely cover the effective area of the electrode layer.

The present application also proposes a method for manufacturing a thermal print head substrate with a composite lead-free protective layer as described above, which is characterized in that after the first protective layer in the composite protective layer is sintered, it is treated with surface planarization to smooth After surface treatment, the surface roughness is less than or equal to 0.2 μm; the surface planarization treatment is to use a polishing abrasive belt made of alumina material with a mesh number of 500-3000 and a particle size of less than 50 μm for polishing; the polished product is subjected to surface cleaning treatment, using Anhydrous ethanol or pure water is used as the cleaning medium for ultrasonic cleaning; the cleaned product is dried, the cleaned product is dried, and the substrate after the first protective layer is smoothed, and then printed and sintered for the second protective layer of glass The glaze composition slurries to form a second protective layer.

The method for manufacturing a thermal print head substrate with a composite lead-free protective layer described in this application specifically includes: Step 1: sequentially prepare a thermal storage underglaze layer, a metal electrode layer, and a heating resistor layer on the surface of an insulating substrate; A protective layer paste is printed on the area of the heating resistor, dried and sintered to form the first protective layer;

Step 2: Adopt surface smoothing process, that is, use 3000 mesh and a polishing abrasive belt made of alumina with a particle size of about 5 μm for reciprocating polishing and grinding; the polished product is subjected to surface cleaning treatment, and absolute ethanol is used as the cleaning medium for ultrasonic cleaning ;The cleaned product is dried at 80-120°C;

The application also includes step 4, using magnetron sputtering or other processes, on the outside of the second protective layer, preparing high-hard carbide or nitride to the effective area of the third protective layer to form the third protective layer.

Compared with the related technology in this application, the first lead-free protective layer is made of wear-resistant silicate glass with higher Vickers hardness; the second lead-free protective layer is made of lead-free silicate with better water resistance and moisture erosion Glass preparation; the third protective layer is an ultra-high hardness protective layer; this application can effectively deal with corrosion damage caused by corrosive or high-humidity environments; three different functional protective layers respectively provide wear protection, corrosion resistance protection and scratch resistance Injury protection; thereby improving product reliability.

Example 1:

This example provides a thermal print head, which is composed of 1 substrate, 2 underglaze layers, 3 electrode layers, 4 heating resistor layers, and 5 protective layers; the substrate 1 has heat resistance and insulation, and is generally an alumina ceramic substrate. The bottom glaze layer 2 mainly plays the role of heat storage and heat preservation, and isolates the resistance heating resistor body 4 from the substrate 1 and provides a smooth surface. The surface of the heating resistor body layer is covered with a lead-free silicate glass composite protective layer 5 with different functions for wear resistance Protective layer; the structure of the above-mentioned components and the interconnection relationship between them are the same as those in the related technology, and will not be repeated here.

As shown in Figure 1, the underglaze slurry containing one or more of the components of alumina, silicon oxide, magnesium oxide, etc., is printed on the surface of the insulating substrate 1 by screen printing or other thick film technology; use 1100-1200 After sintering at a high temperature of ℃, the thermal storage bottom glaze layer 2 of the heating resistor is formed; on the surface of the bottom glaze layer 2, the metal paste is printed on the surface of the thermal storage bottom glaze layer by a screen printing machine; The surface of the substrate is metallized; the metal electrode is patterned by photolithography.

Printing the heating resistor paste to the effective area by screen printing; forming the heating resistor body layer 4 after sintering; printing the lead-free glass glaze composition used to prepare the first protective layer on the heating resistor body area by using a thick film process; drying Afterwards, sintering to the heating resistor and the electrode area to be protected to form a wear-resistant first protective layer;

The lead-free glass glaze composition of the first protective layer is recorded by mass fraction, and the components are respectively: B ₂ O ₃ content 13%, SiO ₂ content 21%; Al ₂ 0 ₃ content 50%, BaO content 6%, CaO The content of ZnO is 4%, and the content of ZnO is 6%. The spherical Al ₂ 0 ₃ added as a filler has a particle size D50 of 0.5 μm;

The prepared lead-free first protective layer has a high Vickers hardness of about 650Hv; as shown in Figure 4, after the first lead-free protective layer is sintered, it is treated with a surface smoothing process, that is, it is made of alumina with a particle size of 800 mesh and a particle size of about 30 μm The polished abrasive belt is used for grinding and polishing; the polished surface is cleaned with pure water; the cleaned product is dried at 120°C; the processed substrate is printed with a second lead-free protective layer, dried and sintered process;

Wherein, the first protective layer after the surface planarization treatment has higher surface smoothness, and its surface roughness is about 0.15 μm; the second lead-free protective layer paste is printed on the electrode-coverable area to form the second protective layer. Corrosion protection layer; wherein the lead-free protective layer glass glaze composition used to prepare the second protection layer is in mass fraction: B ₂ O ₃ content is 20%, Al ₂ 0 ₃ content is 30%; SiO ₂ content range is 45%; The content of Na ₂ O is 2.5%, and the content of K ₂ O is 2.5%. The prepared lead-free second protective layer has excellent acid and alkali corrosion resistance, and the second lead-free protective layer is formed on a high-smooth surface with relatively high Excellent film-forming quality, strong bonding force of the film layer.

After drying and sintering, the thermal print head of Example 1 of the patent application is completed.

In this embodiment, a heating substrate with high surface smoothness and excellent wear resistance and corrosion resistance can be obtained, which can effectively ensure the service life of the product in a high humidity and corrosion environment.

Example 2:

As shown in Figure 2, the underglaze slurry containing one or more components of alumina, silicon oxide, magnesium oxide, etc., is printed on the surface of the insulating substrate 1 by screen printing or other thick film technology; use 1100-1200 After sintering at a high temperature of ℃, the thermal storage bottom glaze layer 2 of the heating resistor is formed; on the surface of the bottom glaze layer 2, the metal paste is printed on the surface of the thermal storage bottom glaze layer by a screen printing machine; Substrate metallization; use photolithography technology to pattern metal electrodes. Use screen printing or drawing process to print the thermal resistance paste to the effective area; form the heating resistor body layer 4 after sintering; use thick film technology to print the lead-free first protective layer paste on the heating resistor body area; after drying, sintering , wherein the lead-free glass glaze composition of the first protective layer, that is, the first protective layer is recorded in mass fraction, and the components are respectively: B ₂ O ₃ content 5%, SiO ₂ content 30%; Al ₂ 0 ₃ content 45%, The content of BaO is 8%, the content of CaO is 6%, and the content of ZnO is 6%. The spherical Al ₂ 0 ₃ added as a filler has a particle size D50 of 0.5 μm; The lead-free first protective layer prepared by this composition has a high Vickers hardness of about 700Hv;

Then the lead-free slurry of the second protective layer is printed to the electrode-coverable area to form a corrosion-resistant second protective layer; wherein the lead-free glass glaze composition of the second protective layer is recorded in mass fraction, and each component is respectively: B ₂ The content of _O3 is 10%; _the content of _Al2O3 is 35%; the content of _SiO2 is 50%; the content of _Na2O is about 5%; the lead-free protective layer prepared by this composition has excellent acid and alkali corrosion resistance; Prepare high-hard carbide or nitride to the effective area of the third protective layer by controlled sputtering or other processes. That is, the thermal print head of Example 2 of the present application is completed.

Example 3:

As shown in Figure 3, the underglaze slurry containing one or more of the components of alumina, silicon oxide, magnesium oxide, etc., is printed on the surface of the insulating substrate 1 by screen printing or other thick film technology; use 1100-1200 After sintering at a high temperature of ℃, the thermal storage bottom glaze layer 2 of the heating resistor is formed; on the surface of the bottom glaze layer 2, the metal paste is printed on the surface of the thermal storage bottom glaze layer by a screen printing machine; Metallize the surface of the substrate; use photolithography to pattern the metal electrodes. The heating resistor paste is printed on the effective area by screen printing or drawing process; the heating resistor body layer 4 is formed after sintering; the first protective layer paste is printed on the electrode-coverable area by thick film technology; after drying, sintering. Then print the second protective layer slurry to the electrode-coverable area to form a corrosion-resistant second protective layer; the glass glaze composition of the first protective layer and the second protective layer adopts the composition of Example 1, and no further details are used. Sputtering or other processes prepare high hardness carbide or nitride to the effective area of the third protective layer. That is, the thermal print head of Example 3 of the present application is completed.

As shown in Figure 5, the moisture resistance and ionization resistance tests were carried out for Embodiment 1 and Embodiment 2 respectively; the storage time comparison under 90% humidity, Na and K ion environment, the storage time under the corrosion environment of the first protective layer alone is 1 /5B(H), if the second protective layer is used alone, the storage time in the corrosive environment is 2B(H); if the composite structure lead-free protective layer is used, the storage period is 2B(H). Corrosion resistance The corrosion resistance of the composite structure protective layer is equivalent to that of the second protective layer alone, and the corrosion resistance is about 10 times that of the first protective layer alone; if converted according to the relevant acceleration coefficient, the composite structure of two protective layers and The three layers of protection can guarantee the normal use of the product life of 1-3 years.

As shown in Figure 6, using the same paper to travel to the same distance to compare the wear of the protective layer, the wear of the first protective layer alone is A (μm/km), and the wear of the second protective layer alone is 2A (μm) /km); the wear of the composite structure lead-free protective layer is about 1.5A (μm/km). Composite structure protection layer (including the third protection layer) is adopted with ultra-high hardness protection layer, and its wear is about 1/4A (μm/km) at the same distance; according to the conversion of product service life, two layers of protection layer with composite structure protection layer and The three layers of protection can respectively guarantee the service life of the product is about 40-50KM, 100-150KM.

This application is made of lead-free protective layers with different functionalities using a composite structure; the first protective layer has high physical hardness and excellent smoothness, thereby ensuring the wear resistance of the product; the first protective layer has undergone surface planarization treatment Finally, while providing excellent wear resistance, give the second protective layer a smooth substrate; thereby ensuring that the second protective layer can produce better bonding force and adhesion; thus the second protective layer can be improved wear resistance. The third protective layer is to deal with large granular substances such as stones and sandstone in the harsh printing environment; thus, ultra-high hardness protection can be achieved. So as to ensure the service life of the product and improve its reliability.

Claims

A thermal printing head substrate with a composite lead-free protective layer is provided with an insulating substrate, and the surface of the insulating substrate is sequentially provided with a heat storage and heat preservation underglaze layer, an electrode layer formed of a metal material, and a heating resistor formed of a semiconductor material. A body layer and a protective layer; wherein the protective layer includes at least two sub-protective layers, wherein the sub-protective layer close to the insulating substrate is the first protective layer, and the second protective layer is compounded outside the first protective layer; the first The thermal expansion coefficient of the protective layer and the second protective layer is 50×10 -7 /°C-70×10 -7 /°C, and the expansion coefficient of the second protective layer is less than or equal to the expansion coefficient of the first protective layer;

The Vickers hardness of the first protective layer is 600-900HV, and the glass glaze composition of the first protective layer comprises the following components in mass percentage: boron oxide B 2 O 3 5-15%; aluminum oxide Al 2 O 3 25-50%; the content range of silicon oxide SiO 2 is 5-30%; the content of glass flux is 10-30%, and the glass flux is barium oxide BaO, zinc oxide ZnO and calcium oxide CaO.
A thermal print head substrate with a composite lead-free protective layer according to claim 1, wherein, in the glass glaze composition of the first protective layer, in terms of the total mass percentage of the composition: boron oxide B 2 O 3 8-13%; aluminum oxide Al 2 O 3 40-45%; silicon oxide SiO 2 content range 21-30%.
A thermal print head substrate with a composite lead-free protective layer according to claim 1, wherein, in the glass flux in the glass glaze composition of the first protective layer, in terms of the total mass percentage of the composition, The content of barium oxide BaO is in the range of 3-8%, the content of zinc oxide ZnO is in the range of 2-6%, and the content of calcium oxide CaO is in the range of 5-20%.
A thermal printhead substrate with a composite lead-free protective layer according to claim 1, wherein the alumina Al 2 O 3 is used as a wear-resistant filler in the first protective layer, and spherical or flaky aluminum oxide Al is used. 2 O 3 , the particle size is about 0.1-1μm.
A thermal printhead substrate with a composite lead-free protective layer according to claim 1, wherein the glass glaze composition of the second protective layer comprises the following components in mass percentage: boron oxide B 2 O 3 The content of aluminum oxide is 10-30%; the content of aluminum oxide Al 2 O 3 is 20-50%; the content of silicon dioxide SiO 2 is in the range of 30-50%; the content of glass glaze flux is 1-5%, and the glass glaze flux is Na 2 O, K 2 O.
A thermal printhead substrate with a composite lead-free protective layer according to claim 5, wherein the glass glaze composition of the second protective layer is in terms of the total mass percentage of the composition: boron oxide B 2 O 3 The content is 10-30%; the content of aluminum oxide Al 2 O 3 is 25-40%; the content of silicon dioxide SiO 2 is 40-45%; the content of Na 2 O in the glass glaze flux is 2..5-5%, The content of K 2 O is 0-5%.
A thermal printhead substrate with a composite lead-free protective layer according to claim 1, wherein a third protective layer is also provided, the third protective layer is compounded on the outside of the second protective layer, and the third protective layer is carbonized The ultra-high hardness protective layer formed by compound, nitride or silicide has a physical characteristic of Vickers hardness ≥ 1200Hv.
A thermal print head substrate with a composite lead-free protective layer according to claim 7, wherein the first protective layer and the third protective layer partially or completely cover the effective area of the electrode layer.
A method for manufacturing a thermal printhead substrate with a composite lead-free protective layer as claimed in any one of claims 1-8, comprising: after the first protective layer in the composite protective layer is sintered, the surface is flat After the smoothness treatment, the surface roughness is ≤0.2μm; the surface flattening treatment is to use a polishing abrasive belt made of alumina material with a mesh number of 500-3000 and a particle size of <50μm for polishing; the polished product is cleaned , drying, and then printing and sintering the second protective layer glass glaze composition slurry on the outside of the first protective layer to form the second protective layer.
A method for manufacturing a thermal printhead substrate with a composite lead-free protective layer according to claim 9, comprising:

Step 1: sequentially prepare a thermal storage base glaze layer, a metal electrode layer, and a heating resistor layer on the surface of the insulating substrate; then print the first protective layer slurry on the heating resistor area, dry, and sinter to form the first protective layer;

Step 2: Adopt surface smoothing process, that is, use 3000 mesh and a polishing abrasive belt made of alumina with a particle size of about 5 μm for reciprocating polishing and grinding; the polished product is subjected to surface cleaning treatment, and absolute ethanol is used as the cleaning medium for ultrasonic cleaning ;The cleaned product is dried at 80-120°C;

Step 3: Printing, drying and sintering of the second protective layer on the treated substrate. Step: Print the second protective layer slurry on the electrode-coverable area to form the second protective layer and the corrosion-resistant protective layer.