A high reliability thermal printhead

Abstract

The utility model relates to thermal printing head manufacturing technical field, specific say is with the ion capture encapsulation structure, can restrain the metal migration to take place, applicable to high temperature, high humidity environment under the high reliability thermal printing head, its characterized in that, be equipped with the composite encapsulation protective layer at control IC and partial electrode wire, be equipped with the composite encapsulation protective layer and include at least one layer ion capture protective layer close to control IC or electrode wire and the encapsulation adhesive layer located the outermost side, the utility model discloses an electrode protective layer with ion capture agent is arranged around the control IC of thermal printing head product, and the anion and cathion are captured, under the premise of basically not promoting the production cost, effectively improve the stability and durability of electrode material.

Description

Technical fields:

[0001] This utility model relates to the field of thermal printhead manufacturing technology, specifically to a highly reliable thermal printhead with an ion-capturing encapsulation structure that can suppress metal migration and is suitable for high-temperature and high-humidity environments. Background technology:

[0002] Traditional thick-film thermal printhead substrates typically use Au as the conductive electrode, which offers high stability but is also costly. More and more manufacturers are now using relatively cheaper metals such as Ag and Cu as electrodes. However, Ag and Cu metals have poor electrochemical stability and are prone to metal migration in high humidity or when exposed to moisture, causing short circuits and failures, thus affecting the printhead's lifespan and reliability.

[0003] Patent CN214137925U discloses a method of coating a dense protective material onto the surface of the encapsulating adhesive to block moisture penetration and improve the damage to control IC devices caused by the "popcorn effect." However, it does not address the electromigration of metal electrode terminals such as silver and copper. Patent CN 116945774 A discloses a method using two encapsulating layers with different water absorption rates; the first resin layer has lower hygroscopicity than the second resin layer, thus suppressing silver migration. However, it fails to address the influence of ions within the encapsulating resin. Therefore, effectively reducing moisture intrusion, suppressing ion-induced metal electromigration, and improving product reliability and lifespan remain pressing technical challenges.

[0004] Patent document CN110607052A discloses a prepreg, laminate, and printed circuit board, which utilizes a thermosetting resin mixture containing an ion trapping agent, including a cationic or anionic ion trapping agent, for prepreg application on a PCB circuit board to form a prepreg layer on the surface of the circuit board to trap free anions or cations in the working environment, thereby improving the service life and reliability of the circuit board. Summary of the Invention:

[0005] This invention addresses the problem of metal electrode migration and short circuits in existing thermal printheads when operating in high-temperature and high-humidity environments. It provides a packaging structure with an ion trapping agent protective layer, which significantly reduces the failure rate caused by ion migration by trapping ions, thereby improving the reliability and lifespan of the thermal printhead in high-humidity environments, resulting in a highly reliable thermal printhead.

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

[0007] A highly reliable thermal printhead is provided with an insulating substrate. A base glaze layer is disposed on the surface of the insulating substrate, and electrode wires are disposed on the surface of the base glaze layer. The electrode wires include comb-shaped individual electrodes, comb-shaped common electrodes, and COM electrodes. The key feature is that a composite encapsulation protective layer is provided at the control IC and some of the electrode wires. The composite encapsulation protective layer includes at least one ion-capturing protective layer close to the control IC or the electrode wires and an outermost encapsulating adhesive layer.

[0008] The ion-capturing protective layer of this invention is formed of a resin material containing an ion-capturing agent. The ion-capturing protective layer is closely attached to and covers the surface of the electrode wire. The control IC is mounted on top of the ion-capturing protective layer. An encapsulating adhesive layer covers the control IC and the ion-capturing protective layer and is integrated with the ion-capturing protective layer. Furthermore, the thickness of the ion-capturing protective layer is in the range of 1-50 μm. The ion-capturing protective layer is a cation-capturing protective layer, used to capture and fix mobile ions (metal cations generated by the electrode), thereby fundamentally disrupting the conditions for electromigration to occur.

[0009] This invention also includes an anion capture protective layer covering the cation capture protective layer and the upper surface of the control IC. The upper surface of the anion capture protective layer is an encapsulating adhesive layer. The anion capture protective layer is formed by a resin mixture containing anion capture agents, which is used to adsorb anions such as hydroxide ions and halogens in the environment, inhibit their migration to adjacent electrodes, and prevent the migration reaction from proceeding. Furthermore, the thickness of the anion capture protective layer is in the range of 1-50 μm.

[0010] The encapsulating adhesive layer described in this invention is the outermost protective layer, made of polymer composite material, with a thickness of 0.3-1mm, preferably with a coefficient of thermal expansion ≤ 1 / 3 mm.

[0011] With a temperature of 25 ppm / ℃ and a water absorption rate of ≤0.1%, it is designed to better match the thermal expansion coefficient of the ceramic substrate, reduce thermomechanical stress during equipment operation, and thus lower the risk of structural cracking.

[0012] The present invention comprises a comb-shaped individual electrode and a comb-shaped common electrode forming a comb-shaped electrode pair, with a heating resistor disposed in the middle of the comb-shaped electrode pair along the main printing direction; one end of the comb-shaped common electrode is connected to the heating resistor, and the other end is connected to the COM electrode; one end of the comb-shaped individual electrode is connected to the heating resistor, and the other end extends to form a pad for connection with a control IC device; a wear-resistant protective layer is provided on the surface of the heating resistor and the comb-shaped common electrode, and on part of the surface of the comb-shaped individual electrode.

[0013] The beneficial effects of this invention are that by setting an electrode protective layer with an ion trapping agent around the control IC of the thermal printhead product, cation and anion trapping is achieved. This effectively improves the stability and durability of the electrode material without significantly increasing production costs, and solves the short circuit problem caused by metal migration in the prior art. By rationally selecting the setting area and thickness of each protective layer, the adaptability of the thermal printhead to the working environment is improved, the product life is extended, and long-term reliability is significantly improved. Attached image description:

[0014] Appendix Figure 1 This is a cross-sectional schematic diagram of the heating substrate for the thermal printhead finally formed in Example 1.

[0015] Appendix Figure 2 This is a planar schematic diagram of a multilayer encapsulation protective layer for the heating substrate of the thermal printhead finally formed in Example 1.

[0016] Appendix Figure 3 This is a cross-sectional schematic diagram of a multilayer encapsulation protective layer for the heating substrate of the thermal printhead finally formed in Example 2.

[0017] Appendix Figure 4 This is a planar schematic diagram of a multilayer encapsulation protective layer for the heating substrate of the thermal printhead finally formed in Example 2.

[0018] Reference numerals: 1-Insulating substrate, 2-Base glaze layer, 3b-Comb-shaped individual electrodes, 3a-Comb-shaped common electrode, 4-Heating resistor, 5-Wear-resistant protective layer, 6-Control IC device, 7a1-Cation trapping protective layer, 7a2-Anion trapping protective layer, 7d-Encapsulation layer. Detailed implementation method:

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0020] Example 1

[0021] This embodiment provides a highly reliable thermal printhead, including an insulating substrate 1. An amorphous glass base glaze layer 2 is formed on the surface of the insulating substrate 1 by screen printing and sintering at 900-1300℃. Electrode pastes such as silver and copper are printed and sintered on the base glaze layer 2 and a portion of the insulating substrate 1, and a comb-shaped common electrode 3a and comb-shaped individual electrodes 3b are formed by photolithography. A heating resistor 4 is formed on the comb-shaped electrode pair formed by the comb-shaped common electrode 3a and the comb-shaped individual electrodes 3b by printing or spraying and sintering at 800-950℃. A wear-resistant protective layer 5 is formed on the surface of the heating resistor 4 and the comb-shaped common electrode 3a, and on a portion of the surface of the comb-shaped individual electrodes 3b by printing and sintering at 500-900℃. An IC controller 6 is soldered to one end of the comb-shaped individual electrodes 3b by pressure bonding or wire bonding. A cation capture protective layer 7a1 and an encapsulation layer 7d are disposed on the comb-shaped individual electrodes 3b and the control IC device 6 of the control IC section.

[0022] The cation-capturing protective layer 7a1 is a cation-capturing layer that directly covers the control IC device 6 and the comb-shaped individual electrodes 3b, with a thickness controlled at 1-50 μm. The cation-capturing layer is composed of resin and cation-capturing agent, and is uniformly filled between the IC device 6 and part of the comb-shaped individual electrodes 3b by spraying. It is then cured by baking at 120°C for 30 minutes in a curing oven. The encapsulation layer 7d is a polymer composite encapsulant with a thickness of 0.3-1 mm, a coefficient of thermal expansion ≤25 ppm / °C, and a water absorption rate ≤0.1%. It is printed onto the area of ​​the control IC device 6, covering the first electrode protective layer 7a1, the IC device 6, and part of the electrodes 3b.

[0023] Example 2

[0024] This embodiment provides a highly reliable thermal printhead, including an insulating substrate 1. An amorphous glass base glaze layer 2 is formed on the surface of the insulating substrate 1 by screen printing and sintering at 900-1300℃. Electrode pastes such as silver and copper are printed and sintered on the base glaze layer 2 and a portion of the insulating substrate 1, and a comb-shaped common electrode 3a and comb-shaped individual electrodes 3b are formed by photolithography. A heating resistor 4 is formed on the comb-shaped electrode pair formed by the comb-shaped common electrode 3a and the comb-shaped individual electrodes 3b by printing or spraying and sintering at 800-950℃. A wear-resistant protective layer 5 is formed on the surface of the heating resistor 4 and the comb-shaped common electrode 3a, and on a portion of the surface of the comb-shaped individual electrodes 3b by printing and sintering at 500-900℃. An IC controller 6 is soldered to one end of the comb-shaped individual electrode 3b by pressure bonding or wire bonding. A cation trapping protective layer 7a1, an anion trapping protective layer 7a2, and an encapsulation layer 7d are sequentially disposed on the comb-shaped individual electrodes 3b and the control IC device 6 of the control IC.

[0025] The cation capture protective layer 7a1 directly covers the control IC device 6 and the electrode 3b, and the thickness is controlled to be 1-50μm.

[0026] The anion protection layer 7a2 is an anion trapping layer, which is disposed on the upper surface of the cation trapping protection layer 7a1 and the control IC, and its thickness is controlled to be 1-50μm.

[0027] The encapsulation layer 7d is a polymer composite encapsulant with a thickness of 0.3-1mm, a coefficient of thermal expansion ≤25ppm / ℃, and a water absorption rate ≤0.1%. It is printed on the area of ​​the control IC device 6, covering the first electrode protective layer 7a1, the second electrode protective layer 7a2, the IC device 6, and part of the electrode 3b.

[0028] Comparative Example 1

[0029] This comparative example provides a highly reliable thermal printhead, including an insulating substrate 1. An amorphous glass base glaze layer 2 is formed on the surface of the insulating substrate 1 by screen printing and sintering at 900-1300℃. Electrode pastes such as silver and copper are printed and sintered on the base glaze layer 2 and a portion of the insulating substrate 1, and comb-shaped common electrodes 3a and comb-shaped individual electrodes 3b are formed by photolithography. A heating resistor 4 is formed on the comb-shaped electrode pair formed by the comb-shaped common electrodes 3a and comb-shaped individual electrodes 3b by printing or spraying and sintering at 800-950℃. A wear-resistant protective layer 5 is formed on the surface of the heating resistor 4 and the comb-shaped common electrode 3a, and on a portion of the surface of the comb-shaped individual electrodes 3b by printing and sintering at 500-900℃. An IC controller 6 is soldered to one end of the comb-shaped individual electrode 3b by pressure bonding or wire bonding. An encapsulation layer 7d is disposed on the comb-shaped individual electrodes 3b and the control IC device 6 of the control IC section.

[0030] In this embodiment, the product underwent accelerated aging testing at 85°C, 85% relative humidity, and 10.5V power supply for 1000 hours without any migration or short circuit issues. In contrast, the comparative sample using only low-absorption encapsulating adhesive (without cation / anion scavengers) showed metal migration in some samples after approximately 750 hours of power supply, leading to short circuits or high-resistance failures in the thermal printhead.

[0031] The beneficial effects of this invention are that by setting an electrode protective layer with an ion trapping agent around the control IC of the thermal printhead product, cation and anion trapping is achieved. This effectively improves the stability and durability of the electrode material without significantly increasing production costs, and solves the short circuit problem caused by metal migration in the prior art. By rationally selecting the setting area and thickness of each protective layer, the adaptability of the thermal printhead to the working environment is improved, the product life is extended, and long-term reliability is significantly improved.

Claims

1. A high-reliability thermal printhead, comprising an insulating substrate, wherein a base glaze layer is disposed on the surface of the insulating substrate, and electrode wires are disposed on the surface of the base glaze layer, the electrode wires including comb-shaped individual electrodes, comb-shaped common electrodes, and COM electrodes, characterized in that, A composite encapsulation protective layer is provided at the control IC and part of the electrode wires. The composite encapsulation protective layer includes at least one ion trapping protective layer close to the control IC or electrode wires and an outermost encapsulating adhesive layer.

2. The high-reliability thermal printhead according to claim 1, characterized in that, The ion-capturing protective layer is formed of a resin material containing an ion-capturing agent. The ion-capturing protective layer is in close contact with and covers the surface of the electrode wire. The control IC is mounted on top of the ion-capturing protective layer. An encapsulating adhesive layer covers the control IC and the ion-capturing protective layer and is integrated with the ion-capturing protective layer.

3. The high-reliability thermal printhead according to claim 2, characterized in that, The thickness of the ion trapping protective layer ranges from 1 to 50 μm, and the ion trapping protective layer is a cation trapping protective layer.

4. The high-reliability thermal printhead according to claim 3, characterized in that, It also includes an anion capture protective layer covering the cation capture protective layer and the upper surface of the control IC. The upper surface of the anion capture protective layer is an encapsulating adhesive layer, and the thickness of the anion capture protective layer ranges from 1 to 50 μm.

5. The high-reliability thermal printhead according to claim 1, characterized in that, The encapsulating adhesive layer is the outermost protective layer, with a thickness of 0.3-1mm.

6. The high-reliability thermal printhead according to claim 1, characterized in that, The individual comb-shaped electrodes and the common comb-shaped electrode form a comb-shaped electrode pair, and the heating resistor is disposed in the middle of the comb-shaped electrode pair along the main printing direction; one end of the common comb-shaped electrode is connected to the heating resistor, and the other end is connected to the COM electrode; one end of the individual comb-shaped electrode is connected to the heating resistor, and the other end extends to form a pad for connection with the control IC device; a wear-resistant protective layer is provided on the surface of the heating resistor and the common comb-shaped electrode, and on part of the surface of the individual comb-shaped electrodes.

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