Heating substrate for thermal printing head

Abstract

The utility model provides a heating substrate for a thermal printing head. The heating substrate comprises an insulating substrate, a ground coat layer, an electrode layer, a driving IC, a heating resistor body, a first insulating protective layer and a second insulating protective layer, the first insulating protection layer is arranged above the part, which is not bonded with the driving IC, of the electrode wire, the heating resistor body and the COM wire; the second insulating protective layer includes a resin sealing portion that completely covers and seals the driving IC, and a resin elastic connecting portion that elastically connects the resin sealing portion and the first insulating protective layer. According to the technical scheme of the utility model, the problem of printing head failure caused by cracking and separation at the overlapping part of the first insulation protection layer and the second insulation protection layer of the thermal printing head can be effectively solved.

Description

Technical Field

[0001] This utility model relates to the field of thermal printhead technology, specifically, it provides a heating substrate for thermal printheads. Background Technology

[0002] The existing thermal printhead heating substrate comprises an insulating substrate, a base glaze layer disposed on the surface of the insulating substrate, and electrode wires and heating resistors disposed above the base glaze layer. The electrode wires and heating resistors are covered with a wear-resistant first insulating protective layer. The first insulating protective layer has an opening larger than the size of the IC at the mounting pads of the driver IC. The driver IC and the pads on the heating substrate are connected at the opening using a BUMP process. At the same time, the opening is covered with epoxy resin encapsulant to form a second insulating protective layer above the driver IC. The second insulating protective layer overlaps with the opening edge of the first insulating protective layer and is on the upper layer.

[0003] During use, it was found that the coefficient of thermal expansion of the epoxy resin rigid encapsulant (20–100 ppm / ℃) is much greater than that of the first insulating protective layer (6.8–7.6 ppm / ℃). Furthermore, the epoxy resin rigid encapsulant becomes extremely hard after curing, lacking flexibility. While it provides high rigidity and structural strength, during subsequent high-temperature pressing or reflow, the mismatch in thermal expansion coefficients between the epoxy resin rigid encapsulant and the first insulating protective layer causes cracking and separation around the overlapping area. This leads to moisture and air contact with the internal circuitry, causing product failure. Epoxy resin flexible encapsulant, with its flexibility, can avoid these problems, but its hardness is insufficient to protect the driver IC. Utility Model Content

[0004] To address the problems existing in the prior art, this utility model provides a heating substrate for thermal printheads with a reasonable structure, simple process, and good weather resistance through embodiments. It can effectively solve the problem of product failure caused by the mismatch between the coefficient of thermal expansion (CTE) and the first insulating protective layer when the product undergoes subsequent high-temperature processing.

[0005] A heating substrate for a thermal printhead, comprising:

[0006] Insulating substrate;

[0007] A base glaze layer disposed on the upper surface of an insulating substrate;

[0008] An electrode layer and a driver IC are disposed on the upper surface of an insulating substrate. The electrode layer includes external signal pads, electrode wires, and COM wires. A portion of the electrode wires is disposed above the base glaze layer, with one end connected to the COM wire and the other end connected to the driver IC.

[0009] A heating resistor disposed on the electrode wire and located above the base glaze layer;

[0010] The first insulating protective layer is disposed on the part of the electrode wire that is not bonded to the driver IC, the heating resistor, and above the COM wire;

[0011] The second insulating protective layer includes a resin sealing portion and a resin elastic connecting portion. The resin sealing portion is disposed above the driver IC to completely cover the driver IC, and there is a gap between the resin sealing portion and the first insulating protective layer. The resin elastic connecting portion is disposed above the gap between the resin sealing portion and the first insulating protective layer to elastically connect the resin sealing portion and the first insulating protective layer.

[0012] In some embodiments, there is an overlap between the resin elastic connection portion and the resin sealing portion, and there is an overlap between the resin elastic connection portion and the first insulating protective layer.

[0013] In some embodiments, at the overlap between the resin elastic connection and the resin sealing portion, the resin elastic connection is located above the resin sealing portion; at the overlap between the resin elastic connection and the first insulating protective layer, the resin elastic connection is located above the first insulating protective layer.

[0014] In some embodiments, the overlap width between the resin elastic connection portion and the resin sealing portion is not less than 1.5 mm.

[0015] In some embodiments, the overlap width between the resin elastic connector and the first insulating protective layer is not less than 1.5 mm.

[0016] In some embodiments, the thickness of the resin elastic connection portion is greater than the thickness of the first insulating protective layer.

[0017] In some embodiments, the maximum thickness of the second insulating protective layer does not exceed 0.7 mm.

[0018] In some embodiments, the resin elastic connector completely covers the resin seal.

[0019] In some embodiments, the resin sealing portion is made of epoxy resin hard encapsulant, and the resin elastic connection portion is made of epoxy resin semi-hard encapsulant.

[0020] In some embodiments, the hardness of the epoxy resin rigid encapsulant is 85-100HD; the hardness of the epoxy resin semi-rigid encapsulant is 50-70HD.

[0021] The thermal printhead heating substrate provided by this utility model designs the second insulating protective layer as consisting of a resin sealing part that completely covers the driver IC and a resin elastic connection part that covers the exposed portion between the resin sealing part and the first insulating protective layer. By providing structural support and sealing protection for the driver IC through the resin sealing part, and achieving elastic connection between the resin sealing part and the first insulating protective layer through the resin elastic connection part, the structural strength required to protect other parts besides the IC can be met. At the same time, it can avoid cracking and separation around the overlapping position of the first insulating protective layer and the epoxy resin hard encapsulant, which would lead to moisture and air contact with the internal circuit of the product and cause product failure. It also provides sufficient strength support and protection for the driver IC, significantly improving product stability and quality. Attached Figure Description

[0022] Figure 1 This is a structural diagram of a heating substrate for a thermal printhead.

[0023] Figure 2 For existing heating substrates in Figure 1 Cross-sectional view along the AA direction;

[0024] Figure 3 This is a top view of an existing heating substrate;

[0025] Figure 4 For the embodiments of this utility model in Figure 1 Cross-sectional view along the AA direction;

[0026] Figure 5 For the embodiments of this utility model in Figure 1 Cross-sectional view along the BB direction;

[0027] Figure 6 This is a top view of an embodiment of the present utility model.

[0028] Numbers in the diagram

[0029] Insulating substrate 1, base glaze layer 2, electrode wire 3-1, external signal pad 3-2a, COM wire 3-2b, heating resistor 4, first insulating protective layer 5, driver IC 6, second insulating protective layer 7, resin sealing part 7-1, resin elastic connection part 7-2, window edge of the first insulating protective layer 8, first edge of the resin sealing part 9, first edge of the resin elastic connection part 10, second edge of the resin elastic connection part 11. Detailed Implementation

[0030] The present invention will now be further described based on preferred embodiments and with reference to the accompanying drawings.

[0031] Furthermore, for ease of understanding, various components on the drawings have been enlarged or reduced, but this is not intended to limit the scope of protection of this utility model.

[0032] In the description of the embodiments of this utility model, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this utility model is in use, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this utility model. Furthermore, in the description of this utility model, the terms "first," "second," etc., are used to distinguish different units, but these are not limited by the manufacturing order, nor should they be construed as indicating or implying relative importance. Their names may differ in the detailed description and claims of this utility model.

[0033] The terminology used in this specification is for illustrative purposes and is not intended to limit the scope of the invention. It should also be noted that, unless otherwise explicitly stated and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection via an intermediate medium; or they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of these terms in this invention.

[0034] Figure 1 This is a structural diagram of a heating substrate for a thermal printhead. Figure 2 For existing heating substrates in Figure 1 Cross-sectional view along the AA direction. Figure 3 This is a top view of an existing heating substrate, based on Figure 1 , Figure 2 , Figure 3 As described in the background art, an existing thermal printhead heating substrate comprises an insulating substrate 1, a base glaze layer 2 disposed on the surface of the insulating substrate, and electrode wires 3-1 and heating resistors 4 disposed above the base glaze layer. A wear-resistant first insulating protective layer 5 covers a portion of the electrode wires 3-1 and the heating resistors 4. The first insulating protective layer 5 has an opening larger than the IC size at the mounting pads of the driver IC 6. The driver IC 6 and the pads on the heating substrate are connected at the opening using a BUMP process. At the same time, the opening is covered with epoxy resin encapsulant to form a second insulating protective layer 7 above the driver IC 6. The second insulating protective layer 7 overlaps with the edge 8 of the opening of the first insulating protective layer and is on the upper layer.

[0035] During use, it was found that the coefficient of thermal expansion of the epoxy resin rigid encapsulant (20–100 ppm / ℃) is much greater than that of the first insulating protective layer 5 (6.8–7.6 ppm / ℃). Furthermore, the epoxy resin rigid encapsulant becomes extremely hard after curing, lacking flexibility. While it provides high rigidity and structural strength, during subsequent high-temperature pressing or reflow processes, the mismatch between the epoxy resin rigid encapsulant and the first insulating protective layer 5 causes cracking and separation around the overlapping area. This leads to moisture and air contact with the internal circuitry, causing product failure. The epoxy resin flexible encapsulant, with its flexibility, can avoid these problems, but its hardness is insufficient to protect the driver IC.

[0036] To address the aforementioned problems, this utility model provides a novel heating substrate for thermal printheads. Figure 4 For the embodiments of this utility model in Figure 1 Cross-sectional view along the AA direction; Figure 5 For the embodiments of this utility model in Figure 1 Cross-sectional view along the BB direction; Figure 6 This is a top view of an embodiment of the present utility model.

[0037] refer to Figure 1 , Figure 4 , Figure 5 and Figure 6 The thermal printhead heating substrate includes an insulating substrate 1, a base glaze layer 2, an electrode layer, a driver IC 6, a heating resistor 4, a first insulating protective layer 5, and a second insulating protective layer 7.

[0038] Specifically, a base glaze layer 2 is disposed on the upper surface of the insulating substrate 1; a driver IC 6 and an electrode layer are disposed on the upper surface of the insulating substrate 1. The electrode layer includes external signal pads 3-2a, electrode wires 3-1, and COM wires 3-2b. A portion of the electrode wires 3-1 is disposed above the base glaze layer 2, with one end connected to the COM wires 3-2b and the other end connected to the driver IC 6; a heating resistor 4 is disposed on the electrode wires 3-1 and located above the base glaze layer 2; a first insulating protective layer 5 is disposed above the electrode wires 3-1, the heating resistor 4, and the COM wires 3-2b. The protective layer 5 has an opening at the location of the driver IC6. The size of the opening is larger than the size of the IC. The electrode wire 3-1 and the driver IC6 at the opening are covered by the second insulating protective layer 7. The second insulating protective layer 7 is composed of a resin sealing part 7-1 and a resin elastic connection part 7-2. The resin sealing part 7-1 completely covers the driver IC6 at the opening of the first insulating protective layer 5. There is a gap between the outermost circumferential edge of the resin sealing part 7-1, i.e., the first edge 9 of the resin sealing part, and the opening edge 8 of the first insulating protective layer. That is, the first edge 9 of the resin sealing part and the opening edge 8 of the first insulating protective layer do not contact each other.

[0039] The resin elastic connector 7-2 is disposed above the gap between the resin sealing part 7-1 and the first insulating protective layer 5 to elastically connect the resin sealing part 7-1 and the first insulating protective layer 5. Specifically, the resin elastic connector 7-2 covers the resin sealing part 7-1 and the first insulating protective layer 5 at the gap between the first edge 9 of the resin sealing part and the window edge 8 of the first insulating protective layer, and the resin elastic connector 7-2 overlaps with both the resin sealing part 7-1 and the first insulating protective layer 5; furthermore, the overlap width between the resin elastic connector 7-2 and the resin sealing part 7-1, and the overlap width between the resin elastic connector 7-2 and the first insulating protective layer 5 are both not less than 1.5 mm. The overlap width between the resin elastic connector 7-2 and the resin sealing part 7-1 specifically refers to the horizontal distance between the first edge 10 of the resin elastic connector (i.e., the innermost circumferential edge of the resin elastic connector 7-2 that contacts the resin sealing part 7-1) and the first edge 9 of the resin sealing part, and the overlap width between the resin elastic connector 7-2 and the first insulating protective layer 5 specifically refers to the horizontal distance between the second edge 11 of the resin elastic connector (i.e., the outermost circumferential edge of the resin elastic connector 7-2 that contacts the first insulating protective layer 5) and the window edge 8 of the first insulating protective layer. The first insulating protective layer 5 and the second insulating protective layer 7 completely cover and tightly bond the printhead except for the solder pads connecting the external signal lines to isolate it from air and water.

[0040] Furthermore, the resin sealing part 7-1 uses epoxy resin hard encapsulant, and the resin elastic connection part 7-2 uses epoxy resin semi-rigid encapsulant. Epoxy resin adhesives are classified into soft adhesives, semi-rigid adhesives, and hard adhesives according to their hardness and flexibility after curing. Compared with soft adhesives, epoxy resin semi-rigid adhesives maintain a certain hardness after curing and can provide better structural strength; compared with hard adhesives, epoxy resin semi-rigid adhesives also have a certain degree of flexibility and can absorb a certain amount of impact and stress. By designing the resin sealing part 7-1 as an epoxy resin rigid encapsulant, it provides sufficient hardness and mechanical strength to provide structural support and sealing protection for the driver IC. The resin elastic connection part 7-2 is designed as an epoxy resin semi-rigid encapsulant, so that its structural strength is sufficient to protect other parts besides the IC, while its flexibility can absorb the stress caused by temperature changes due to the mismatch of thermal expansion coefficients. This can avoid the problem of cracking and separation around the overlapping position of the first insulating protective layer 5 and the epoxy resin rigid encapsulant, which would lead to moisture and air contact with the internal circuit of the product and cause product failure. At the same time, it provides sufficient strength support and protection for the IC, significantly improving product stability and quality.

[0041] In this invention, the hardness of the epoxy resin hard encapsulant is 85-100HD, and the hardness of the epoxy semi-hard encapsulant is 50-70HD.

[0042] The preferred embodiment of the heating substrate for the thermal printhead will be described below.

[0043] like Figure 1 , Figure 4 , Figure 5 and Figure 6 As shown, firstly, a base glaze layer 2 is formed on the upper surface of the insulating substrate 1 by screen printing and sintering. Then, a metal layer is formed on the insulating substrate 1 by screen printing and sintering. An electrode layer including electrode wires 3-1, external signal pads 3-2a, and COM wires 3-2b is formed by processes such as coating, light leakage, and etching.

[0044] The external signal pad 3-2a is used to transmit communication signals, the COM wire 3-2b is used to connect the power supply, and the electrode wire 3-1 is comb-shaped and is disposed between the external signal pad 3-2a and the COM wire 3-2b. A portion of the electrode wire extends from one side of the base glaze layer 2 to the other side of the base glaze layer 2 and is connected to the COM wire 3-2b through one end; the other end of the electrode wire is connected to the bonding pad of the driver IC6. The driver IC6 is connected to the substrate 1 through the BUMP process after the first insulating protective layer 5 is fabricated.

[0045] Furthermore, the portion of the electrode wire 3-1 located above the base glaze layer 2 is formed by drawing or printing resistive paste and sintering to form a heating resistor 4. Then, glass paste is printed above the remaining electrode wire 3-1, heating resistor 4, and COM wire 3-2b, except for the opening larger than the IC size reserved around the electrode wire 3-1 and the position for driving IC6 bonding in the electrode layer, and sintering is performed to form a first insulating protective layer 5 of wear-resistant glass material with a size larger than the IC size at the bonding driving IC6 position.

[0046] Next, the driver IC6 and the substrate 1 are connected by the BUMP process. On the driver IC6, a regularly shaped epoxy resin hard encapsulant is applied by casting or dispensing process to completely cover the driver IC6 and whose edges do not contact the window edge 8 of the first insulating protective layer. After curing, the resin sealing part 7-1 of the second insulating protective layer 7 is obtained. Between the window edge 8 of the first insulating protective layer 5 and the first edge 9 of the resin sealing part, a regularly shaped epoxy resin semi-rigid encapsulant is applied by casting or dispensing process to completely cover the remaining exposed part of the window, with a thickness greater than the first insulating protective layer 5, overlapping with both the first insulating protective layer 5 and the resin sealing part 7-1, and with an overlap width of not less than 1.5mm. After curing, the resin elastic connection part 7-2 of the second insulating protective layer 7 is obtained. The first insulating protective layer 5, the resin sealing part 7-1 of the second insulating protective layer, and the resin elastic connection part 7-2 together cover the entire part of the printhead except for the external signal pad 3-2a and are tightly bonded to isolate air and moisture.

[0047] In some preferred embodiments, the maximum thickness of the second insulating protective layer 7 does not exceed 0.7 mm to avoid interfering with the movement of printing consumables.

[0048] In some alternative embodiments, the overlap width between the resin elastic connector 7-2 and the first insulating protective layer 5 can be made wider without affecting the printed structure.

[0049] In some alternative embodiments, the overlap width between the resin elastic connector 7-2 and the resin sealing part 7-1 can be made wider without limiting the thickness, or even completely cover the resin sealing part 7-1.

[0050] The specific embodiments of this utility model have been described in detail above. For those skilled in the art, several improvements and modifications can be made to this utility model without departing from the principle of this utility model, and these improvements and modifications also fall within the protection scope of the claims of this utility model.

Claims

1. A heating substrate for a thermal printhead, comprising: Insulating substrate; A base glaze layer disposed on the upper surface of an insulating substrate; An electrode layer and a driver IC are disposed on the upper surface of an insulating substrate. The electrode layer includes external signal pads, electrode wires, and COM wires. A portion of the electrode wires is disposed above the base glaze layer, with one end connected to the COM wire and the other end connected to the driver IC. A heating resistor disposed on the electrode wire and located above the base glaze layer; Its characteristic is that it further includes: The first insulating protective layer is disposed on the part of the electrode wire that is not bonded to the driver IC, the heating resistor, and above the COM wire; The second insulating protective layer includes a resin sealing portion and a resin elastic connecting portion. The resin sealing portion is disposed above the driver IC to completely cover and seal the driver IC. There is a gap between the resin sealing portion and the first insulating protective layer. The resin elastic connecting portion is disposed above the gap between the resin sealing portion and the first insulating protective layer to elastically connect the resin sealing portion and the first insulating protective layer.

2. The heating substrate for a thermal printhead according to claim 1, characterized in that, There is an overlap between the resin elastic connection portion and the resin sealing portion, and there is an overlap between the resin elastic connection portion and the first insulating protective layer.

3. The heating substrate for a thermal printhead according to claim 2, characterized in that, At the overlap between the resin elastic connector and the resin sealing part, the resin elastic connector is located above the resin sealing part; at the overlap between the resin elastic connector and the first insulating protective layer, the resin elastic connector is located above the first insulating protective layer.

4. The heating substrate for a thermal printhead according to claim 2, characterized in that, The overlap width between the resin elastic connection part and the resin sealing part shall not be less than 1.5mm.

5. The heating substrate for a thermal printhead according to claim 2, characterized in that, The overlap width between the resin elastic connector and the first insulating protective layer is not less than 1.5 mm.

6. The heating substrate for a thermal printhead according to claim 1, characterized in that, The thickness of the resin elastic connector is greater than the thickness of the first insulating protective layer.

7. The heating substrate for a thermal printhead according to claim 1, characterized in that, The maximum thickness of the second insulating protective layer shall not exceed 0.7 mm.

8. The heating substrate for a thermal printhead according to claim 1, characterized in that, The resin elastic connector completely covers the resin sealing part.

9. The heating substrate for a thermal printhead according to claim 1, characterized in that, The resin sealing part uses epoxy resin hard encapsulant, and the resin elastic connection part uses epoxy resin semi-hard encapsulant.

10. The heating substrate for a thermal printhead according to claim 9, characterized in that, The epoxy resin rigid encapsulant has a hardness of 85-100 HD; the epoxy resin semi-rigid encapsulant has a hardness of 50-70 HD.

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