Highly stable heat generating substrate for thermal printhead

Abstract

The utility model relates to the technical field of thermal printing head manufacturing, and specifically relates to a high-stability heating substrate for thermal printing head, the common electrode and the bonding electrode adopt non-active metal electrodes, the individual electrode is composed of the lap joint of active metal electrode section and non-active metal electrode section, wherein the individual electrode of the area within 1cm adjacent to the heating resistor body is the non-active metal electrode section, and the rest individual electrodes are the active metal electrode section, the non-active metal electrode is the electrode section made of any one material or alloy of gold, copper, nickel, tungsten, titanium and chromium, and the active metal electrode section is the electrode section made of any one or alloy of aluminium and silver, compared with the prior art, the manufacturing cost is reduced, and the service life is prolonged.

Description

Technical fields:

[0001] This utility model relates to the field of thermal printhead manufacturing technology, specifically a heating substrate for a highly stable thermal printhead that has a reasonable structure, low production cost, and can effectively overcome product failures caused by easy oxidation, electromigration, and electrocorrosion of electrode wires. Background technology:

[0002] The thermal printhead is a crucial component of a thermal printer. Currently, the heating element of thermal printheads typically uses metals such as silver and aluminum to fabricate the electrode leads. These metals are reactive; for example, silver electrode leads can chemically react with sulfur in the air. In dry air, a layer of silver sulfide forms on the surface of the silver-sulfur electrode leads, affecting their conductivity. If the electrode leads near the heating element are made of silver or aluminum, problems such as oxidation, electromigration, and electro-corrosion are particularly severe, exacerbating electrode corrosion and reducing the product's electrical and weather resistance.

[0003] Using inert metals or metal alloys such as gold, tungsten, and titanium to fabricate electrode wires can overcome the above problems, but the overall cost increases dramatically. Furthermore, existing thermal printhead products do not have an insulating protective layer on some electrodes of the heating substrate, such as the bonding electrodes. This is because the bonding electrodes are connected to the control IC device and act as a signal bridge between the control IC device and the heating resistor during printing, sending relevant control signals to the corresponding heating resistor. After the control IC device is connected to the bonding electrode, it is encapsulated with an epoxy resin layer. Because the encapsulation layer is hygroscopic, this leads to severe electromigration and corrosion of the electrode wires in this area during operation, causing product circuit failures.

[0004] The CN213798824U high-performance thin-film thermal printhead heating substrate has a layered design for the electrodes in the heating element area, without considering the bonding area. In practical applications, the bonding electrode damage rate is higher, and it is easy to cause chip failure. Summary of the Invention:

[0005] This invention addresses the shortcomings and deficiencies of existing technologies by proposing a highly stable heating substrate for thermal printheads that features a reasonable structure, low production cost, and effectively overcomes product failures caused by easy oxidation, electromigration, and electrocorrosion of electrode wires.

[0006] This utility model achieves its purpose through the following measures:

[0007] A heating substrate for a high-stability thermal printhead includes a ceramic substrate with a heat-storing glaze layer. Electrode wires and a heating resistor are disposed on the heat-storing glaze layer. An outer protective layer is provided on the surface of the heating resistor and some of the electrode wires. The electrode wires include a common electrode, individual electrodes, and a bonding electrode. The heating resistor is disposed above the common electrode and individual electrodes. One end of each individual electrode is connected to the heating resistor, and the other end is connected to the bonding electrode. The common electrode and bonding electrode are made of inactive metal electrodes. Each individual electrode is composed of overlapping active and inactive metal electrode segments. The individual electrodes within 1 cm of the heating resistor are inactive metal electrode segments, while the remaining individual electrodes are active metal electrode segments. The inactive metal electrodes are made of any one of gold, copper, nickel, tungsten, titanium, or chromium, or their alloys. The active metal electrode segments are made of any one of aluminum or silver, or their alloys.

[0008] The thickness of the bonding electrode using a non-reactive metal electrode described in this invention is 0.1-1 μm. When the thickness of the bonding electrode is less than 0.1 μm, the stability and conductivity of the bonding electrode are low. When it is greater than 1 μm, it affects the thermal efficiency of the heating element of the thin film product.

[0009] The thickness of the active metal electrode segment of this invention ranges from 8 to 20 μm. The two ends of the active metal electrode segment overlap the non-active metal electrode segment. The overlap portion of the active metal electrode segment has a stepped structure, so that the thickness of the overlap portion is less than the thickness of the main body of the active metal electrode segment, thereby ensuring that the resistivity of the electrode wire after overlap meets the product requirements.

[0010] The outer protective layer of this invention includes an insulating protective layer. This insulating protective layer is provided above the heating resistor layer (excluding the bonding electrodes) and the electrode wires. The insulating protective layer is formed using SiO2, AlN, or Si3N4 with a resistivity greater than 10^11 Ω·m via high-power magnetron sputtering (CVD). Furthermore, a high-hardness, wear-resistant layer is also provided on the insulating protective layer. To ensure film formation, a film layer of SiC, WC, DLC, or TiAlN is formed using high-power magnetron sputtering (CVD or PVD). The thickness of the insulating protective layer is 4–10 μm. The density of the insulating layer is ensured by two printing and sintering processes, or a dense, high-resistivity film or insulating film is formed using magnetron sputtering. The thickness of the wear-resistant protective layer is 2–10 μm.

[0011] The thermal conductivity of the heat-storing glaze layer described in this invention is less than 1.5 W / mK, and the thickness of the heat-storing glaze layer is 15–200 μm. For products with low printing speeds, such as below 4 ips, the thickness is greater than 100 μm. For products with printing speeds of 4–10 ips, the thickness of the heat-storing glaze layer is 30–100 μm. For speeds above 10 ips, the thickness of the heat-storing glaze layer should be less than 30 μm but greater than 15 μm. If the thickness of the heat-storing glaze layer is too thin, it cannot fill the defects of the ceramic substrate.

[0012] The thickness of the heating resistor described in this invention is 2–8 μm.

[0013] This invention employs inactive metal electrode segments at the bonding electrode site, as well as on the common electrode and individual electrodes within 1 cm of the heating resistor. Without adding an additional insulating protective layer to the bonding electrode surface, this effectively prevents electrode corrosion, improves the product's electrical and weather resistance, and extends the printhead's lifespan. Furthermore, by using inactive metals or metal alloys only in the aforementioned areas, other parts can still use low-cost reactive metals such as aluminum or silver to fabricate the electrodes, reducing manufacturing costs. In addition, the dense insulating protective layer protects the heating resistor from external environmental influences, improving its stability; and the high-hardness wear-resistant layer enhances the printhead's wear resistance and extends its service life. Attached image description:

[0014] Appendix Figure 1 This is a planar schematic diagram of the electrode wire in this utility model.

[0015] Appendix Figure 2 This is a schematic diagram of the cross-sectional structure of this utility model.

[0016] Appendix Figure 3 yes Figure 2 A magnified view of a portion of point A in the middle.

[0017] Figure reference numerals: 1. Insulating substrate; 2. Heat storage glaze layer; 3. Electrode wire; 3-1. Cross-section of common electrode and individual electrode; 3-2. Individual electrode; 3-3. Bonding electrode; 4. Heating resistor; 5. Insulating protective layer; 6. Wear-resistant protective layer. Detailed implementation method:

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] Example 1:

[0020] This example provides a heating substrate for a thermal printhead, which includes a hard ceramic substrate used as an insulating substrate. A heat storage glaze layer is provided on the insulating substrate, and electrode wires and a heating resistor are disposed on the heat storage glaze layer. A corresponding outer protective layer is also provided. The outer protective layer includes a dense insulating protective layer and a high-hardness wear-resistant layer.

[0021] In this example, the electrode wires are divided into common electrodes, individual electrodes, and bonding electrodes. A heating resistor is provided at the junction of the common electrode and the individual electrodes. The individual electrodes and the common electrode in the heating part (within 1 cm from the center line of the heating resistor) are made of gold (Au), and the bonding electrode in the part without the insulating protective layer is also made of gold (Au).

[0022] In this example, the thickness of the heat storage glaze layer ranges from 5 to 50 μm, the heating resistor 4 is made of RuO2 material with a thickness range of 3 to 8 μm, the non-reactive metal electrode segment made of gold (Au) paste in the electrode wire has a thickness range of 0.2 μm, and the bonding electrode in the part without the insulating protective layer is also made of gold (Au) paste with a thickness range of 0.2 μm.

[0023] In this example, a dense insulating protective layer SiO2 with a thickness of 3-10 μm is formed on the heating resistor 4 by printing and sintering. Finally, a high-hardness wear-resistant layer SiC with a thickness of 2-6 μm is prepared on the protective layer by ion beam assisted reactive ion etching.

[0024] Example 2:

[0025] This example provides a heating substrate for a thermal printhead, wherein the inactive metal segments of the electrode wires in this example—the individual electrodes and common electrodes of the concentrated heating area and the bonding electrodes—are made of tungsten-titanium alloy (WTi) with a thickness ranging from 0.2 to 0.4 μm.

[0026] In this example, the thickness of the heat storage glaze layer ranges from 15 to 35 μm, and the heating resistor 4 uses a resistor layer made of ruthenium oxide material with a thickness range of 3 to 8 μm.

[0027] A dense insulating protective layer with a thickness of 2-8 μm was deposited on the heating resistor 4 using an ion beam assisted reactive ion etching process. Finally, a high-hardness wear-resistant layer C-SiC with a thickness of 1-6 μm was prepared on the protective layer using a vapor deposition process.

[0028] Example 3:

[0029] This example provides a heating substrate for a thermal printhead. The non-reactive metal electrode segment of the electrode wire in this example includes individual electrodes and a common electrode for the concentrated heating area, which are made of tungsten-titanium alloy (WTi) with a thickness of 0.4 μm. It also includes bonding electrodes in the areas without an insulating protective layer, which are made of gold (Au) with a thickness of 0.3 μm.

[0030] In this example, the thickness of the heat storage glaze layer ranges from 15 to 60 μm, the heating resistor 4 is made of TaSiO material with a thickness range of 0.1 to 2 μm, a dense insulating protective layer with a thickness range of 1.5 to 3.5 μm is deposited on the heating resistor layer using a magnetron sputtering film deposition process, and finally, a high-hardness wear-resistant layer C-SiC with a thickness range of 2 to 4 μm is prepared on the protective layer using a thin film vapor deposition process.

[0031] Example 1 uses a gold electrode, which can be formed by thick film printing. The process is easier to implement, but the cost is slightly higher. Example 2 uses a tungsten-titanium electrode, which can withstand high temperatures of over 1000°C in the heating element part. The product performance is more stable, but the efficiency is lower. Example 3 uses a high-temperature resistant tungsten-titanium electrode in the heating element part, while the bonding part has a lower temperature and can use a more stable gold electrode. The preparation efficiency is high and the cost is controlled.

Claims

1. A heating substrate for a high-stability thermal printhead, comprising a ceramic substrate, a heat-retaining glaze layer disposed on the ceramic substrate, electrode wires and a heating resistor disposed on the heat-retaining glaze layer, and an outer protective layer disposed on the surface of the heating resistor and part of the electrode wires, wherein... The electrode wire includes a common electrode, individual electrodes, and a bonding electrode. A heating resistor is disposed above the common electrode and the individual electrodes. One end of the individual electrode is connected to the heating resistor, and the other end is connected to the bonding electrode. The common electrode and the bonding electrode are made of inactive metal electrodes. The individual electrodes are composed of overlapping active and inactive metal electrode segments. Specifically, the individual electrodes within 1 cm of the heating resistor are inactive metal electrode segments, while the remaining individual electrodes are active metal electrode segments. The inactive metal electrodes are made of any one of gold, copper, nickel, tungsten, titanium, or chromium, or their alloys. The active metal electrode segments are made of any one of aluminum or silver, or their alloys.

2. The high-stability heat generating substrate for a thermal printhead according to claim 1, wherein The thickness of the bonding electrode using a non-reactive metal electrode is 0.1–1.0 μm. When the thickness of the bonding electrode is less than 0.1 μm, the stability and conductivity of the bonding electrode are low. When it is greater than 1 μm, it affects the thermal efficiency of the heating element of the thin film product.

3. The high-stability heat generating substrate for a thermal printhead according to claim 1, wherein The thickness of the active metal electrode segment ranges from 8 to 20 μm. The two ends of the active metal electrode segment overlap the non-active metal electrode segment. The overlap portion of the active metal electrode segment has a stepped structure, so that the thickness of the overlap portion is less than the thickness of the main body of the active metal electrode segment, thereby ensuring that the resistivity of the electrode wire after overlap meets the product requirements.

4. The high-stability heat generating substrate for a thermal printhead according to claim 1, wherein The outer protective layer includes an insulating protective layer, wherein an insulating protective layer is provided above the heating resistor layer (excluding the bonding electrode) and the electrode wire. The insulating protective layer is formed by high-power magnetron sputtering CVD using SiO2, AlN, or Si3N4 with a resistivity greater than 10^11 Ω·m.

5. The high-stability heat generating substrate for a thermal printhead according to claim 4, wherein A high-hardness wear-resistant layer is also provided on the insulating protective layer. To ensure the film formation effect, high-power magnetron sputtering technology is used to form any one of SiC, WC, DLC, and TiAlN films.

6. The high-stability heat generating substrate for a thermal printhead according to claim 5, wherein The thickness of the insulating protective layer is 4 to 10 μm. The density of the insulating layer is ensured by two printing and sintering processes or by forming a dense high-resistivity film or insulating film by magnetron sputtering. The thickness of the wear-resistant protective layer is 2 to 10 μm.

7. The high-stability heat generating substrate for a thermal printhead according to claim 1, wherein The thermal conductivity of the heat-storing glaze layer is less than 1.5 W / mK, and the thickness of the heat-storing glaze layer is 15–200 μm. For products with low printing speeds, such as below 4 ips, the thickness is greater than 100 μm. For products with printing speeds of 4–10 ips, the thickness of the heat-storing glaze layer is 30–100 μm. For speeds above 10 ips, the thickness of the heat-storing glaze layer should be less than 30 μm and greater than 15 μm.

8. The high-stability heat generating substrate for a thermal printhead according to claim 1, wherein The thickness of the heating resistor is 2–8 μm.

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