High-humidity-climate-resistant heating substrate for thin film thermal printing head

Abstract

The utility model relates to the technical field of thermal printing head manufacturing, in particular to a heating substrate for a thin film thermal printing head, which is reasonable in structure, simple and convenient in process and capable of effectively reducing the problem of electrode corrosion caused by water vapor passing through an existing solder mask area or an existing packaging adhesive area and is resistant to high humidity climate. And an insulating solder mask layer formed by a PFA insulating material is also arranged, and the insulating solder mask layer covers the upper surface of the insulating substrate except for the peripheral area of the heating resistor body and the central area of the bonding electrodes. Compared with the prior art, the utility model has the advantages that the structure is reasonable, the process is simple and convenient, the product quality can be obviously improved, the service life can be obviously prolonged, and the like.

Description

Technical field:

[0001] The utility model relates to the technical field of thermal print head manufacturing, and specifically is a heating substrate for a thin film thermal print head that is resistant to high humidity climate and has a reasonable structure and simple process and can effectively reduce the problem of electrode corrosion caused by water vapor passing through an existing solder mask layer area or a packaging glue area. Background technology:

[0002] We know that the heating substrate for the thin film thermal print head includes an insulating substrate with an amorphous glaze coating formed on the surface. During the production process, a heating resistor layer is provided on the amorphous glaze coating, and a conductor layer covering the heating resistor layer is further provided. During the production, the conductor layer is formed into an electrode wire through photoengraving technology, and the resistor layer is formed into a plurality of heating resistors arranged along the main printing direction. Then, a non-conductive material mainly composed of silicon is used to form an insulating film protective layer and a conductive hard protective layer on the heating resistor and at least part of the electrode wire in sequence through magnetron sputtering. In the remaining electrode wire area, a modified epoxy resin-acrylic ink is used as an insulating solder resist material to protect the electrode wire. However, the water absorption rate of the insulating resin of most ink solder resist materials is about 0.2-0.5%. With the expansion of the application environment of the thermal print head, especially in a high humidity environment, water vapor will gradually enter the insulating solder resist layer and corrode the electrode wire, thereby reducing the reliability and service life of the product. Summary of the invention:

[0003] In view of the shortcomings and deficiencies in the prior art, the utility model proposes a heating substrate for a thin film thermal print head which is resistant to high humidity climates and has a reasonable structure and simple process, and can effectively reduce the problem of electrode corrosion caused by water vapor passing through the existing solder mask layer area or the packaging glue area.

[0004] The utility model achieves this through the following measures:

[0005] A heating substrate for a thin-film thermal print head that is resistant to high-humidity climates, comprising an insulating substrate, a base glaze layer on the surface of the insulating substrate, a heating resistor and electrode wires arranged on the base glaze layer, and a protective layer formed by magnetron sputtering on the upper surfaces of the heating resistor and part of the electrode wires. The invention is characterized in that an insulating solder resist layer formed of a PFA insulating material is also provided, and the insulating solder resist layer covers the upper surface of the insulating substrate except for the peripheral area of ​​the heating resistor and the central area of ​​the bonding electrode.

[0006] The peripheral area of ​​the heating resistor described in the utility model is an area 1 to 3 mm away from the center of the heating resistor. This is because during the operation of the print head, in order to allow the roller with the printing paper to only contact the central area of ​​the heating element above the heat storage base glaze, the insulating solder resist layer needs to maintain a certain distance from the heating element to prevent scratching the printing paper. The central area of ​​the bonding electrode is the center of the bonding electrode surface and the area is 80 to 90% of the bonding electrode area. If it is covered too much, it will affect the welding area of ​​the subsequent pressure welding project. If it is not covered enough, the pad will be exposed too much, which will reduce the effect of the PFA solder resist layer in preventing water vapor from entering the substrate.

[0007] The insulating solder resist layer formed by the PFA insulating material of the utility model overlaps with the protective layer, and the overlapping range is 2 to 4 mm. The protective layer is divided into an insulating protective layer and a conductive protective layer from bottom to top. In order to avoid the short circuit problem between the conductive protective layer and the electrode wire, the edge of the conductive protective layer will be narrower by 1 to 2 mm toward the heating element than the insulating protective layer. According to the different sizes of the substrate, the PFA insulating protective layer must cover the conductive protective layer with a width of at least 1 mm to better prevent water vapor from entering the interior of the substrate along the gap.

[0008] The thickness of the insulating solder mask formed by the PFA insulating material of the utility model ranges from 10 to 20 μm. Experiments have shown that the water absorption rates of the substrates printed with the ink solder mask and the PFA insulating solder mask of the same thickness are 0.24% and 0.05% respectively. The lower limit of the thickness is to consider that the foreign body protrusions of the lower protective film can be well covered, and the upper limit of the thickness is to consider the cheapness of pressure welding.

[0009] The protective layer of the utility model comprises an insulating protective layer and a conductive protective layer formed by magnetron sputtering, which cover the surface of the heating resistor and the surface of part of the electrode wire.

[0010] The utility model can overcome the problem of internal circuit corrosion caused by water vapor entering the original ink solder mask and packaging glue in a high humidity environment by arranging an insulating solder mask layer formed by a PFA material with extremely low water absorption on the surface of the heating substrate of the thin film thermal print head. In addition, by limiting the arrangement area of ​​the insulating solder mask formed by the PFA material, the protection effect of the internal circuit structure of the thin film thermal print head can be effectively improved without affecting the normal printing work.

[0011] Compared with the prior art, the utility model has the advantages of reasonable structure, simple process, and can significantly improve product quality and service life. Description of the drawings:

[0012] Attached Figure 1 The present invention is a partial structural schematic diagram of a heating substrate for an existing thin film thermal print head.

[0013] Attached Figure 2 It is a partial structural schematic diagram of the utility model.

[0014] Attached Figure 3 It is a schematic diagram of the cross-sectional structure of the utility model.

[0015] Figure markings: 10: insulating substrate; 20: heat storage base glaze layer; 30: substrate base glaze layer; 40: heating resistor; 50: wire electrode; 50a: bonding electrode; 50b: lead-out electrode; 50c: bonding electrode area not covered by PFA insulating solder resist layer; 50d: bonding electrode area covered by PFA insulating solder resist layer; 60, insulating protective layer; 610: insulating protective layer edge; 70, conductive protective layer; 80; PFA insulating solder resist layer; 810: covering protective layer area of ​​PFA insulating solder resist layer; 90, ink solder resist layer; 910, area not covered by ink solder resist layer. Specific implementation method:

[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0017] As attached Figure 1 As shown, in addition to the insulating protective layer 60 and the conductive protective layer 70, an ink solder resist layer 90 is arranged on the upper and lower parts of the bonding electrode 50a. The ink solder resist layer 90 is in the shape of a strip parallel to the length direction of the heating resistor 40. The area around the bonding electrode 50a forms an area 910 not covered by the ink solder resist layer. This results in that in a high humidity environment, even under the protection of the packaging glue, water vapor will enter the interior of the heating substrate along the gap between the ink solder resist layer and the packaging glue, corroding the internal electrode wire. In addition, the other side of the heating resistor 40 is only covered with the insulating protective layer 60 and the conductive protective layer 70, which will cause water vapor to enter the interior of the substrate from the gap between the ink solder resist base layer and the conductive protective layer, corroding the electrical circuit.

[0018] In order to solve the above problems, as shown in the attached Figure 2 As shown, the utility model proposes a heating substrate for a thin film thermal print head resistant to high humidity climate, and a PFA insulating solder resist layer 80 formed of a PFA insulating material is provided on the surface of the heating substrate for the thin film thermal print head, and the PFA insulating solder resist layer 80 covers the upper surface of the insulating substrate except for the peripheral area of ​​the heating resistor and the central area of ​​the bonding electrode; wherein the peripheral area of ​​the heating resistor is an area 1 to 3 mm away from the center of the heating resistor, and the central area of ​​the bonding electrode is an area at the center of the bonding electrode surface and an area of ​​80 to 90% of the bonding electrode area;

[0019] As attached Figure 2As shown, the PFA insulating solder resist layer 80 overlaps with the insulating protective layer 60 and the conductive protective layer 70, with an overlapping range of 2 to 4 mm to avoid the short circuit problem between the conductive layer and the electrode wire. The edge of the conductive protective layer is narrower than the insulating protective layer by 1 to 2 mm toward the heating element. According to experiments, the PFA insulating protective layer must cover the conductive protective layer with a width of at least 1 mm to better prevent water vapor from entering the interior of the substrate along the gap.

[0020] The thickness of the PFA insulating solder resist layer 80 is in the range of 10 to 20 μm. Experiments have shown that the water absorption rates of substrates printed with the same thickness of ink solder resist and PFA insulating solder resist are 0.24% and 0.05% respectively. The lower limit of the thickness (10 μm) is to consider that the foreign matter protrusions of the lower protective film can be well covered, and the upper limit of the thickness (20 μm) is to consider the cheapness of pressure welding.

[0021] The protective layer includes an insulating protective layer and a conductive protective layer formed by magnetron sputtering, which cover the surface of the heating resistor and part of the surface of the electrode wire.

[0022] In this example, an insulating solder mask layer formed by PFA material with extremely low water absorption is arranged on the surface of the heating substrate of the thin film thermal print head, which can overcome the internal circuit corrosion problem caused by the entry of water vapor into the original ink solder mask layer and the packaging glue in a high humidity environment. In addition, by limiting the arrangement area of ​​the insulating solder mask layer formed by the PFA material, the protection effect of the internal circuit structure of the thin film thermal print head can be effectively improved without affecting the normal printing work.

[0023] Compared with the prior art, the utility model has the advantages of reasonable structure, simple process, and can significantly improve product quality and service life.

Claims

1. A heating substrate for a thin-film thermal print head resistant to high humidity climate, comprising an insulating substrate, a base glaze layer on the surface of the insulating substrate, a heating resistor and an electrode wire arranged on the base glaze layer, and a protective layer formed by magnetron sputtering on the upper surface of the heating resistor and part of the electrode wire, characterized in that: An insulating solder resist layer formed of a PFA insulating material is also provided, and the insulating solder resist layer covers the upper surface of the insulating substrate except for the peripheral area of ​​the heating resistor and the central area of ​​the bonding electrode.

2. The high-humidity climate-resistant heat-generating substrate for a thin-film thermal print head according to claim 1, characterized in that: The heating resistor peripheral area is an area 1 to 3 mm away from the center of the heating resistor.

3. The high-humidity climate-resistant heat-generating substrate for a thin-film thermal print head according to claim 1, characterized in that: The bonding electrode central region is a region at the center of the bonding electrode surface and has an area of ​​80 to 90% of the bonding electrode area.

4. The high-humidity climate-resistant heat-generating substrate for a thin-film thermal print head according to claim 1, characterized in that: A protective layer is also provided, which is divided into an insulating protective layer and a conductive protective layer from bottom to top. The edge of the conductive protective layer is narrower than the insulating protective layer by 1 to 2 mm toward the heating element. The insulating solder resist layer formed by the PFA insulating material overlaps with the protective layer, and the overlapping range is 2 to 4 mm.

5. The high-humidity climate-resistant heat-generating substrate for a thin-film thermal print head according to claim 1, characterized in that: The thickness of the insulating solder resist layer formed by the PFA insulating material is in the range of 10 to 20 μm.

6. The high-humidity climate-resistant heat-generating substrate for a thin-film thermal print head according to claim 1, characterized in that: The protective layer includes an insulating protective layer and a conductive protective layer formed by magnetron sputtering, which cover the surface of the heating resistor and part of the surface of the electrode wire.

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