A pot key anti-glue overflow FPC board structure

Abstract

The utility model provides a kind of FPC board structure of pot key anti-glue overflow, including FPC board, pot key, the pot key is welded on the FPC board, the surface of the FPC board is equipped with covering film, the covering film is equipped with window area at the welding place of pot key, the window area is coated with solder resist ink, the pot key is completely located in the coating area of solder resist ink, the upper surface of the solder resist ink is higher than the upper surface of the covering film, the pin of the pot key, the solder resist ink directly below the pot key is all covered with glue.The utility model passes through the structure of optimizing FPC board, so that pot key meets waterproof requirement, and glue overflow caused by too much glue can not be caused, and covering film of FPC board can not be damaged.

Description

Technical Field

[0001] This utility model relates to the field of FPC board structure design, and in particular to an FPC board structure for preventing overflow of adhesive on dome buttons. Background Technology

[0002] Dome buttons are widely used in electronic products, especially small dome buttons, which are widely used in mobile phones, tablets, watches and other products. As product requirements become more stringent, more and more products require waterproofing, especially side buttons of products that integrate fingerprint recognition and dome button functions (such as the power button of new mobile phones). These products require that the solder pads and solder joints of the dome button and the FPC board area directly below the dome button be completely covered with glue to achieve waterproofing.

[0003] Currently, dome buttons utilize the capillary underfill principle for adhesive dispensing. Adhesive is applied between the bottom edge of the dome button and the FPC board. Due to capillary action, the adhesive quickly flows into the narrow gap between the dome button and the FPC board. Because of its high fluidity, the adhesive doesn't linger at the dome button pins, failing to effectively cover the solder joints and thus failing to provide waterproofing. Increasing the amount of adhesive dispensed can effectively cover the solder joints, but it also causes adhesive overflow. Excess adhesive flows away from the dome button, sticking to the FPC board's cover film. Once the adhesive dries, the material hardens. When the FPC board is installed on products like mobile phones, any impact that causes the adhesive to break will also shatter the cover film, requiring the FPC board to be repaired or rendered unusable.

[0004] Therefore, it is necessary to design an FPC board structure for preventing spillage of adhesive on dome buttons to overcome the above problems. Utility Model Content

[0005] The purpose of this utility model is to overcome the defects of the prior art and provide an FPC board structure for preventing overflow of adhesive in the dome button. This utility model solves at least some of the problems in the prior art.

[0006] This utility model is implemented as follows:

[0007] This utility model provides an FPC board structure for preventing overflow of adhesive on a dome button, including an FPC board and a dome button. The dome button is soldered to the FPC board. A cover film is provided on the surface of the FPC board. The cover film has a window area at the solder joint of the dome button. The window area is coated with solder resist ink. The dome button is completely located within the area coated with solder resist ink. The upper surface of the solder resist ink is higher than the upper surface of the cover film. The pins of the dome button and the solder resist ink directly below the dome button are covered with adhesive.

[0008] Furthermore, the upper surface of the solder resist ink is 10-30 μm higher than the upper surface of the cover film.

[0009] Furthermore, the top edge of the solder resist ink is at a right angle.

[0010] Furthermore, the pins of the dome button are located at both ends along its length, and the solder resist ink extends 1.3~1.5mm beyond the end of the dome button along its length.

[0011] Furthermore, the FPC board structure of the dome button anti-overflow adhesive also includes a fingerprint chip and a connector for electrical connection with the controller. The fingerprint chip and the connector are both soldered onto the FPC board, and the fingerprint chip and the dome button are both electrically connected to the connector.

[0012] Furthermore, a fingerprint chip reinforcing steel sheet is provided on the side of the FPC board opposite to the fingerprint chip, and the fingerprint chip reinforcing steel sheet is bonded to the FPC board.

[0013] Furthermore, the FPC board is in a bent state, the dome button is directly opposite the fingerprint chip, and the fingerprint chip reinforcing steel sheet is located between the dome button and the fingerprint chip.

[0014] Furthermore, a reinforcing steel sheet for the dome button is provided on the side of the FPC board opposite to the dome button, and the reinforcing steel sheet for the dome button is bonded to the FPC board.

[0015] Furthermore, the fingerprint chip reinforcing steel sheet is provided with a receiving groove, and the pot button reinforcing steel sheet is located in the receiving groove.

[0016] Furthermore, the reinforcing steel sheet for the button and the reinforcing steel sheet for the fingerprint chip are bonded and fixed together with double-sided adhesive.

[0017] This utility model has the following beneficial effects:

[0018] 1. This utility model provides an FPC board structure for preventing overflow of adhesive on dome buttons. The cover film has a windowed area at the solder joint of the dome button, and the windowed area is coated with solder resist ink. The dome button is completely located within the area coated with solder resist ink. The upper surface of the solder resist ink is higher than the upper surface of the cover film, forming a step between the solder resist ink and the cover film. By utilizing the surface tension of the adhesive, the adhesion between the adhesive and the solder resist ink, the adhesive's own anti-flow ability, and the "physical barrier" of the step structure, the adhesive will not overflow onto the cover film beyond the edge of the step. This utility model can ensure that the pins of the dome button and the solder resist ink directly below the dome button are effectively covered by adhesive without using too much adhesive, achieving a good waterproof effect.

[0019] 2. In this invention, for the glue to flow down the step, its center of gravity must decrease, which requires additional energy. With precise control of the glue application rate and no external pressure, the glue's own kinetic and potential energy are insufficient to overcome this energy barrier. When the leading edge of the glue flow is blocked by the step, subsequent glue, due to its high viscosity, will not easily "overflow" the edge of the step like water, but will accumulate until the resistance is overcome. In this design, the resistance of the step is always greater than the driving force of the glue. Specifically, after multiple tests, this invention demonstrates that when the solder resist ink extends outwards from the dome button by at least 1.3 mm, the glue will not cross the edge of the step formed by the solder resist ink while ensuring that the dome button pins are fully covered.

[0020] 3. In this utility model, the glue "shrinks" itself on the surface of the solder resist ink. The stepped edge of the solder resist ink acts like an invisible wall. Unless excessive glue is added or there is an external force pushing it, the glue will stay stably within the stepped area of ​​the solder resist ink and will not overflow onto the cover film, thus not damaging the cover film.

[0021] 4. In this utility model, the reinforcing steel sheet can effectively enhance the strength of the dome button, fingerprint chip, and connector, and extend the service life of the overall FPC board structure.

[0022] 5. In this utility model, the fingerprint chip reinforcing steel sheet is provided with a receiving groove, and the pot button reinforcing steel sheet is located in the receiving groove, making the overall structure of the FPC board more compact. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A schematic diagram of the FPC board used for the anti-overflow adhesive of the dome button provided in this embodiment of the utility model;

[0025] Figure 2 A schematic diagram of the FPC board structure for the anti-overflow adhesive of the dome button after installing the reinforcing steel sheet, provided for an embodiment of this utility model;

[0026] Figure 3 Provided for the embodiments of this utility model Figure 2 Enlarged view of the buttons on the middle pot;

[0027] Figure 4 Provided for the embodiments of this utility model Figure 2 Enlarged view on the right;

[0028] Figure 5 Provided for the embodiments of this utility model Figure 4 Enlarged view on the right.

[0029] In the diagram: 1. Dome button; 2. Fingerprint chip; 3. Connector; 4. Covering film; 5. First contact; 6. Second contact; 7. Pin; 8. Glue; 9. Reinforcing steel sheet for dome button; 10. Double-sided tape; 11. FPC board; 12. Reinforcing steel sheet for fingerprint chip; 13. Reinforcing steel sheet for connector; 14. Solder resist ink; 15. Step. Detailed Implementation

[0030] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.

[0031] In the description of this utility model, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They 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. Therefore, they should not be construed as limitations on this utility model.

[0032] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this utility model, unless otherwise stated, "several" means two or more.

[0033] like Figures 1-5This utility model embodiment provides an FPC board structure for anti-overflow adhesive of a dome button, including an FPC board 11 and a dome button 1. The dome button 1 is soldered onto the FPC board 11. The surface of the FPC board 11 is provided with a cover film 4. The cover film 4 has a window area at the solder joint of the dome button 1. The window area is the area not covered by the cover film. The window area is coated with solder resist ink 14. The solder pads soldered to the dome button 1 are exposed in the solder resist ink 14. Compared with the exposed solder pads of the cover film 4, the exposed solder pads of the solder resist ink 14 have higher precision. The dome button 1 is completely located within the coating area of ​​the solder resist ink 14. The upper surface of the solder resist ink 14 is higher than the upper surface of the cover film 4, that is, a step 15 is formed between the solder resist ink 14 and the cover film 4. The edge of the step 15 is right angled (that is, the top edge of the solder resist ink is right angled). The pins 7 of the dome button 1 and the solder resist ink 14 directly below the dome button 1 are covered with adhesive 8. In this embodiment, the upper surface of the solder resist ink 14 is 10-30 μm higher than the upper surface of the cover film 4. This invention provides a step formed by the solder resist ink 14 on the FPC board 11. The adhesive does not easily flow down the edge of the step because: firstly, the surface of the adhesive (liquid) has "surface tension": the attraction between liquid molecules causes the surface to tend to "contract to its minimum surface area" (similar to the principle of water droplets forming a sphere on a table). When the adhesive flows to the edge of the step, the surface tension generates a pulling force "along the tangential direction of the step surface," offsetting part of the downward pull of gravity on the adhesive; secondly, there is "adhesion" (intermolecular attraction, similar to the principle of tape sticking to an object) between the adhesive and the step surface (solder resist ink): the solder resist ink has a higher roughness than the smooth cover film, increasing the contact area between the adhesive and the solder resist ink, making the adhesion stronger; thirdly, the adhesive itself has "anti-flow capability": the adhesive used for FPC waterproofing is usually " High-viscosity fluids have high intermolecular friction and slow flow. When the adhesive reaches the edge of a step, the internal resistance caused by viscosity further slows down or even stops the flow. Gravity needs to overcome the resistance caused by viscosity to pull the adhesive downward. If the height difference of the step is not large (such as 10-30um in this application), the viscosity resistance is enough to offset gravity and make the adhesive "stop at the edge of the step". Fourth, there is the "physical obstruction" of the geometric structure of the step: the vertical height of the step requires the adhesive to "climb" over this height. If the adhesive wants to flow downward, it needs to overcome surface tension and adhesion to "detach from the edge of the step" and then fill the height difference downward. This process consumes gravitational potential energy and reduces the flow power. In addition, the edge of the step is a "right angle", and the "flow path" of the adhesive at the edge will change abruptly, forming local "eddy current resistance", which further slows down the flow.

[0034] In this invention, for the glue to flow down the step, its center of gravity needs to drop, which requires additional energy. With precise control of the glue application rate and no external pressure, the glue's own kinetic and potential energy are insufficient to overcome this energy barrier. When the leading edge of the glue flow is blocked by the step, subsequent glue, due to its high viscosity, will not easily "overflow" the edge like water, but will accumulate until the resistance is overcome. In this design, the resistance of the step is always greater than the driving force of the glue. Specifically, after multiple tests, this invention demonstrates that when the solder resist ink extends outwards from the dome button by at least 1.3 mm, the glue will not cross the edge of the step formed by the solder resist ink while ensuring that the dome button pins are fully covered. Figure 1 In this design, the dome button has pins at both ends along its length, and the solder resist ink extends 1.3mm beyond each end of the dome button's length. The length direction of the dome button is... Figure 1 The up and down directions in the middle.

[0035] In this invention, the adhesive "shrinks" itself onto the surface of the solder resist ink. The stepped edge of the solder resist ink acts like an invisible wall. Unless excessive adhesive is added or an external force is applied, the adhesive will remain stably within the stepped area of ​​the solder resist ink and will not overflow onto the cover film, thus preventing damage to the cover film.

[0036] The FPC board structure of the anti-overflow adhesive for the button also includes a fingerprint chip 2, which is soldered onto the FPC board 11.

[0037] The FPC board structure of the dome button anti-overflow adhesive also includes a connector 3 for electrical connection with the controller. The connector 3 is soldered onto the FPC board 11, and both the fingerprint chip 2 and the dome button 1 are electrically connected to the connector 3. In this embodiment, the fingerprint chip 2 is electrically connected to the controller inside the mobile phone through the connector 3, and the dome button 1 is also electrically connected to the controller inside the mobile phone through the connector 3. When the user only lightly touches the button cap on the side of the mobile phone, only the fingerprint chip 2 is triggered to perform fingerprint recognition and transmit the signal to the mobile phone controller. When the fingerprint is correct, the mobile phone controller issues a command to unlock the mobile phone. When the user touches and presses the button cap on the side of the mobile phone, the first contact 5 of the dome button and the second contact 6 of the dome button make contact. The branches of the fingerprint chip 2 and the dome button 1 are both connected to the mobile phone controller. When the fingerprint is correct, the mobile phone controller issues a command to unlock the mobile phone and light up the mobile phone screen.

[0038] The FPC board 11 has a fingerprint chip reinforcing steel sheet 12 on the side opposite to the fingerprint chip 2. The fingerprint chip reinforcing steel sheet 12 is bonded to the FPC board 11. The fingerprint chip reinforcing steel sheet 12 is a 3D steel sheet.

[0039] like Figure 2The FPC board 11 is bent, the dome button 1 is directly opposite the fingerprint chip 2, and the fingerprint chip reinforcing steel sheet 12 is located between the dome button 1 and the fingerprint chip 2.

[0040] The FPC board 11 has a reinforcing steel sheet 9 for the dome button 1 on the side opposite to the dome button 1, and the reinforcing steel sheet 9 is bonded to the FPC board 11. The fingerprint chip reinforcing steel sheet 12 has a receiving groove, and the reinforcing steel sheet 9 for the dome button 12 is located in the receiving groove, making the overall structure of the FPC board 11 more compact. The reinforcing steel sheet 9 for the dome button 1 and the fingerprint chip reinforcing steel sheet 12 are bonded and fixed with double-sided adhesive. The reinforcing steel sheet 9 for the dome button 1 can protect the dome button 1 and the solder resist ink 14.

[0041] The FPC board 11 has a fingerprint chip connector reinforcing steel sheet 13 on the side opposite to the connector 3, and the connector reinforcing steel sheet 13 is bonded to the FPC board 11. Preferably, the cover film 4 has windows at the locations where the reinforcing steel sheets are provided, so that the reinforcing steel sheets can be directly bonded to the substrate of the FPC board 11, resulting in better adhesion. The reinforcing steel sheets can effectively enhance the strength of the dome button 1, the fingerprint chip 2, and the connector 3, and extend the service life of the overall structure of the FPC board 11.

[0042] In this invention, the upper surface of the solder resist ink 14 is 10-30µm higher than the upper surface of the cover film 4. The adhesive will accumulate on the surface of the solder resist ink and will not flow onto the cover film of the FPC board, thus preventing adhesive overflow.

[0043] This invention optimizes the structure of the FPC board, enabling the dome button to meet waterproof requirements without overflowing due to excessive glue.

[0044] This utility model provides an FPC board structure for preventing glue spillage on dome buttons, resulting in a more aesthetically pleasing glue coverage, less glue usage, and lower manufacturing costs.

[0045] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0046] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An FPC board structure for preventing overflow of adhesive on dome buttons, characterized in that: The device includes an FPC board and a dome button. The dome button is soldered onto the FPC board. The surface of the FPC board is covered with a cover film. The cover film has a window area at the solder joint of the dome button. The window area is coated with solder resist ink. The dome button is completely located within the area coated with solder resist ink. The upper surface of the solder resist ink is higher than the upper surface of the cover film. The pins of the dome button and the solder resist ink directly below the dome button are covered with adhesive.

2. The FPC board structure for the anti-overflow adhesive of the dome button as described in claim 1, characterized in that: The upper surface of the solder resist ink is 10-30 μm higher than the upper surface of the cover film.

3. The FPC board structure for the anti-overflow adhesive of the dome button as described in claim 1, characterized in that: The top edge of the solder resist ink is at a right angle.

4. The FPC board structure for the anti-overflow adhesive of the dome button as described in claim 1, characterized in that: The pins of the dome button are located at both ends along its length. Along the length of the dome button, the solder resist ink extends 1.3~1.5mm beyond the end of the dome button.

5. The FPC board structure for the anti-overflow adhesive of the dome button as described in claim 1, characterized in that: It also includes a fingerprint chip and a connector for electrical connection with the controller. Both the fingerprint chip and the connector are soldered onto the FPC board, and both the fingerprint chip and the dome button are electrically connected to the connector.

6. The FPC board structure for the anti-overflow adhesive of the dome button as described in claim 5, characterized in that: The FPC board has a fingerprint chip reinforcing steel sheet on the side opposite to the fingerprint chip, and the fingerprint chip reinforcing steel sheet is bonded to the FPC board.

7. The FPC board structure for the anti-overflow adhesive of the dome button as described in claim 6, characterized in that: The FPC board is bent, the dome button is directly opposite the fingerprint chip, and the fingerprint chip reinforcing steel sheet is located between the dome button and the fingerprint chip.

8. The FPC board structure for the anti-overflow adhesive of the dome button as described in claim 7, characterized in that: The FPC board has a reinforcing steel sheet for the dome button on the side opposite to the dome button, and the reinforcing steel sheet for the dome button is bonded to the FPC board.

9. The FPC board structure for the anti-overflow adhesive of the dome button as described in claim 8, characterized in that: The fingerprint chip reinforcing steel sheet is provided with a receiving groove, and the pot button reinforcing steel sheet is located in the receiving groove.

10. The FPC board structure for the anti-overflow adhesive of the dome button as described in claim 9, characterized in that: The reinforcing steel sheet for the button and the reinforcing steel sheet for the fingerprint chip are bonded together with double-sided adhesive.

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