A template for fabricating strain gauges with solder joint coating

Abstract

This invention relates to a strain gauge fabrication template for solder joint coating. The template includes an array of strain gauge photolithographic areas, a conductive strip photolithographic area, and a connecting line photolithographic area connecting the strain gauge photolithographic areas and the conductive strip photolithographic areas. The conductive strip photolithographic area is located around the strain gauge photolithographic areas and extends to each strain gauge photolithographic area. The connecting line photolithographic area connects each strain gauge photolithographic area and the conductive strip photolithographic area. This invention short-circuits all strain gauge patterns with connecting lines, and coats the solder joints by isolating the sensitive grid and using an electroplating process. Finally, by cutting the connecting lines, setting a protective layer for the sensitive grid, and cutting and shaping, a strain gauge with solder joint coating is obtained. Since the strain gauge itself is coated, flux is no longer needed during connection with other circuits.

Description

[0001] This invention patent application is a divisional application of Chinese invention patent application filed on December 31, 2020, with application number 202011640015.6 and title "A method for preparing a strain gauge with a solder joint coating and a preparation template thereof". Technical Field

[0002] This invention relates to the field of strain gauge fabrication templates, specifically to a strain gauge fabrication template with solder joint coating. Background Technology

[0003] A strain gauge is a sensor that measures the change in resistance as a function of force. It converts physical quantities such as force, pressure, tension, and weight into changes in resistance, thereby measuring these quantities. When an external force acts on a stationary object, stress and strain are generated. The reaction force generated within the object (towards the external force) is called stress, and the resulting displacement and deformation is called strain. Strain gauges are one of the most important sensors in electrical measurement technology, used for measuring mechanical quantities. As their name suggests, strain gauges are primarily used for strain measurement. In technical terms, "strain" includes tensile strain and compressive strain, distinguished by positive and negative signs. Therefore, strain gauges can measure both expansion and contraction.

[0004] During the manufacturing process of strain gauges, solder joints need to be tinned for connection to other circuits. However, the sensitive grid of the strain gauge is mainly made of special materials such as Evan or Karma, which contain aluminum and have small solder joints, making soldering more difficult. Furthermore, corrosive flux must be added, introducing uncontrollable factors into the reliability and stability of the solder joints.

[0005] The purpose of this invention is to design a strain gauge fabrication template for solder joint coating to address the problems existing in the prior art. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention provides a strain gauge preparation template for solder joint coating, which can effectively solve the problems existing in the prior art.

[0007] The technical solution of this invention is:

[0008] A strain gauge fabrication template for solder joint coating, the fabrication template comprising an array of strain gauge photolithography areas, a conductive strip photolithography area, and a connecting line photolithography area connecting the strain gauge photolithography areas and the conductive strip photolithography areas;

[0009] The conductive strip lithography area is located on the periphery of the strain gauge lithography area and extends to each strain gauge lithography area. The connecting line lithography area connects each strain gauge lithography area and the conductive strip lithography area.

[0010] Furthermore, the strain gauge fabrication method of the strain gauge fabrication template is as follows:

[0011] S1, Preparation of substrate composite layer: The metal foil coated with substrate slurry is heated and the substrate slurry is cured to obtain a substrate composite layer composed of metal foil and substrate, wherein the substrate composite layer includes an array of strain gauge photolithography areas.

[0012] S2, Fabricating strain gauge patterns: Photolithography is used to lithographically print the metal foil to obtain strain gauge patterns in each strain gauge region. The strain gauge patterns include sensitive grids and solder joints.

[0013] S3, Short-circuit strain gauge patterns: Short-circuit all the strain gauge patterns by connecting lines;

[0014] S4, Solder joint coating: Isolate the sensitive grid and coat the solder joints with a coating through an electroplating process to obtain a strain gauge pattern with the coating on the solder joints;

[0015] S5, Cut the connecting wire: The connecting wire is cut off by laser;

[0016] S6, Set a sensitive grid protective layer: Set a sensitive grid protective layer on the side of the strain gauge pattern corresponding to the sensitive grid to obtain a strain gauge array;

[0017] S7, Cutting and shaping: The strain gauge array is cut by laser to obtain a single strain gauge.

[0018] Furthermore, step S2 specifically includes:

[0019] The strain gauge template is applied to the substrate composite layer, and a strain gauge pattern is obtained in each strain gauge region through photolithography and the cooperation of the strain gauge template.

[0020] Furthermore, step S3 specifically includes:

[0021] The strain gauge template is covered on the substrate composite layer. Through photolithography and the cooperation of the strain gauge template, connecting lines that short-circuit each strain gauge pattern and conductive strips that connect all the connecting lines are obtained.

[0022] Further, in step S4, the electroplating process for depositing a film on the solder joint specifically involves:

[0023] By energizing the conductive strip through electroplated leads, all strain gauge patterns are energized, and then all solder joints are coated.

[0024] Furthermore, in step S4, the coating is either gold plating or tin plating.

[0025] Furthermore, the tin plating thickness is 5-100 micrometers, and the gold plating thickness is 0.5-1 micrometer.

[0026] Furthermore, between steps S5 and S6, the following is further included:

[0027] S5.1, Resistance Adjustment: Adjust the resistance of the sensitive grid of each strain gauge pattern to the required range.

[0028] Furthermore, in step S1, the composite layer further includes several strain gauge monitoring areas;

[0029] In step S2, after photolithography is performed on the metal foil, monitoring strain gauge patterns are further obtained in several of the strain gauge monitoring areas.

[0030] In step S3, the connecting line is not short-circuited to the monitoring strain gauge pattern.

[0031] Therefore, the present invention provides the following effects and / or advantages:

[0032] This invention involves short-circuiting all strain gauge patterns with connecting wires, isolating the sensitive grid, and applying a coating to the solder joints using an electroplating process. Finally, by cutting the connecting wires, applying a protective layer to the sensitive grid, and cutting the strain gauge into its final shape, a strain gauge with a coated solder joint is obtained. Since the strain gauge itself is coated, flux is no longer required when connecting it to other circuits.

[0033] This invention uses connecting lines to uniformly short-circuit all strain gauge patterns, thereby depositing a film on the weld points of the strain gauge patterns. This ensures the consistency of the film coating on all weld points, with the same degree of coverage. During the subsequent resistance adjustment process, the probe of the resistance adjustment instrument only needs to contact the weld point. Compared with the traditional workflow of adjusting the strain gauge first and then manually spot welding, this invention has a wide contact area for the probe of the resistance adjustment instrument, eliminating the need for precise contact at a specific location.

[0034] This invention prepares a strain gauge template, which includes a strain gauge photolithography area, a conductive strip photolithography area, and a connecting line photolithography area connecting the strain gauge photolithography area and the conductive strip photolithography area. This template provides a masking template for subsequent photolithography processes, thus allowing for the generation of pre-connected strain gauge patterns in a single photolithography step. This results in high work efficiency and high consistency.

[0035] It should be understood that the above summary and the following detailed description of the invention are exemplary and explanatory, and are intended to provide further explanation of the invention as claimed. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the process of the present invention.

[0037] Figure 2 A schematic diagram of the strain gauge template.

[0038] Figure 3 for Figure 2 Enlarged view of part A. Detailed Implementation

[0039] To facilitate understanding by those skilled in the art, the structure of the present invention will now be described in further detail with reference to the accompanying drawings:

[0040] A template for fabricating strain gauges with solder joint coating, reference Figure 2-3 The method for fabricating a strain gauge with a solder joint coating is described above. The fabrication template includes an array of strain gauge photolithography areas, a conductive strip photolithography area, and a connecting line photolithography area connecting the strain gauge photolithography areas and the conductive strip photolithography areas.

[0041] Furthermore, the preparation template strain gauge monitors the photolithography area.

[0042] refer to Figure 1 A method for preparing a strain gauge with solder joint coating includes the following steps:

[0043] S0, Fabrication of strain gauge template: The strain gauge template includes an array of strain gauge photolithography areas 1, a conductive strip photolithography area 2, and a connecting line photolithography area 3 connecting the strain gauge photolithography area 1 and the conductive strip photolithography area 2.

[0044] In this embodiment, reference Figure 2-3 The conductive strip lithography area is located outside the strain gauge lithography area and extends to each strain gauge lithography area. The width of the conductive strip lithography area is much larger than that of the connecting line lithography area, which connects each strain gauge lithography area and the conductive strip lithography area.

[0045] S1, Preparation of substrate composite layer: Heating the metal foil coated with the substrate to solidify the substrate slurry, thereby obtaining a substrate composite layer composed of the metal foil and the substrate, wherein the substrate composite layer includes an array of strain gauge regions;

[0046] In this embodiment, a base slurry is coated on a single side of the metal foil. The base slurry used in this embodiment is a polyimide slurry, and the metal foil is either Evan or Karma. Other materials may be used in other embodiments, and this is not limited here. The base slurry is cured by heating it to a certain temperature in an oven and then bonded to the metal foil. One surface of the metal foil is exposed to the base slurry, resulting in a base composite layer. An array of strain gauge regions is then planned within the base composite layer.

[0047] S2, Fabricating strain gauge patterns: The metal foil is photolithographically lithographically patterned to obtain strain gauge patterns in each strain gauge region. The strain gauge patterns include a sensitive grid and solder joints. Specifically, the strain gauge template is applied to the substrate composite layer, and the strain gauge patterns are obtained in each strain gauge region through the combination of photolithography and the strain gauge template.

[0048] S3, Shorting the strain gauge patterns: Shorting all the strain gauge patterns by connecting lines; specifically: through photolithography and the cooperation of the strain gauge template, connecting lines that short each strain gauge pattern and conductive strips connecting all the connecting lines are obtained.

[0049] In this embodiment, in steps S2-S3, the strain gauge template is covered onto the substrate composite layer, and photoresist is applied to the entire surface of each substrate composite layer through photolithography and the strain gauge template. After exposure with the strain gauge template, the areas not covered by the strain gauge template are washed away during development, and then etched to obtain a strain gauge pattern of metal foil with the same shape as the strain gauge template, and a composite layer with the strain gauge pattern attached. At the same time, the strain gauge pattern has connecting lines, which short-circuit the connecting lines and conductive strips of each strain gauge pattern.

[0050] S4, Solder joint coating: Isolate the sensitive grid and coat the solder joints with a coating through an electroplating process to obtain a strain gauge pattern with the coating on the solder joints;

[0051] In this embodiment, the sensitive grid is isolated by attaching it with adhesive tape. Current is then passed through the conductive strip via electroplated leads, thereby energizing all strain gauge patterns. Subsequently, a coating is deposited on all solder joints. This coating is either gold or tin plating. If the coating is tin, its thickness is 5-100 micrometers; if the coating is gold, its thickness is 0.5-1 micrometer. Specifically, in this embodiment, the tin thickness is 5 micrometers, 50 micrometers, or 100 micrometers, and the gold thickness is 0.5 micrometers, 0.8 micrometers, or 1 micrometer. Other thicknesses are also possible in other embodiments.

[0052] S5, Cut the connecting wire: The connecting wire is cut off by laser;

[0053] S5.1, Resistance Adjustment: Adjust the resistance of the sensitive grid of each strain gauge pattern to the required range;

[0054] In this embodiment, the tape needs to be removed before adjusting the resistance. Strain gauge resistance adjustment is a prior art technique; it can be achieved by grinding the sensitive grid, thereby adjusting the resistance of the sensitive grid of each strain gauge pattern to the required range. Specific resistance adjustment methods are not limited here, nor are they described in detail.

[0055] S6, Setting a Sensitive Grid Protective Layer: A sensitive grid protective layer is set on the side of the strain gauge pattern corresponding to the sensitive grid to obtain a strain gauge array. In this embodiment, a cover layer slurry is further coated on the side of the strain gauge pattern corresponding to the sensitive grid, and then heated and cured in a heating chamber to obtain the sensitive grid protective layer, thereby obtaining a complete strain gauge including a substrate, a sensitive grid, and a cover layer. The method for setting the sensitive grid protective layer is prior art and will not be described in detail here.

[0056] S7, Cutting and shaping: The strain gauge array is cut by laser to obtain a single strain gauge.

[0057] Further, refer to Figure 2-3 In this embodiment, a strain gauge monitoring photolithography area is provided on the strain gauge template.

[0058] In step S1, several strain gauge monitoring areas are further obtained in the composite layer by photolithography.

[0059] In step S2, after photolithography is performed on the metal foil, monitoring strain gauge patterns are further obtained in several of the strain gauge monitoring areas.

[0060] In step S3, the connecting line is not short-circuited to the monitoring strain gauge pattern.

[0061] During the photolithography process, because all strain gauge patterns are short-circuited by connecting lines, the resistance value of the strain gauge patterns cannot be obtained, making it impossible to precisely control the etching degree of the pattern during the photolithography process. This embodiment uses a resistance measuring instrument connected to monitor the strain gauge patterns, thereby monitoring their resistance value and precisely controlling parameters such as etching time in the etching process.

[0062] Furthermore, the strain gauge monitoring lithography area can be set on the periphery, corner, or center of the strain gauge template.

[0063] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A strain gauge fabrication template for solder joint coating, characterized in that: The fabrication template includes an array of strain gauge photolithography areas, a conductive strip photolithography area, and a connecting line photolithography area connecting the strain gauge photolithography areas and the conductive strip photolithography areas. The conductive strip lithography area is located on the periphery of the strain gauge lithography area and extends to each strain gauge lithography area. The connecting line lithography area connects each strain gauge lithography area and the conductive strip lithography area. The strain gauge preparation method for the strain gauge preparation template is as follows: S1, Preparation of substrate composite layer: The metal foil coated with substrate slurry is heated and the substrate slurry is cured to obtain a substrate composite layer composed of metal foil and substrate, wherein the substrate composite layer includes an array of strain gauge photolithography areas. S2, Fabricating strain gauge patterns: Photolithography is used to lithographically print the metal foil to obtain strain gauge patterns in each strain gauge region. The strain gauge patterns include sensitive grids and solder joints. S3, Short-circuit strain gauge patterns: Short-circuit all the strain gauge patterns by connecting lines; S4, Solder joint coating: Isolate the sensitive grid and coat the solder joints with a coating through an electroplating process to obtain a strain gauge pattern with the coating on the solder joints; S5, Cut the connecting wire: The connecting wire is cut off by laser; S6, Set a sensitive grid protective layer: Set a sensitive grid protective layer on the side of the strain gauge pattern corresponding to the sensitive grid to obtain a strain gauge array; S7, Cutting and shaping: The strain gauge array is cut by laser to obtain a single strain gauge.

2. The strain gauge fabrication template for solder joint coating according to claim 1, characterized in that: Step S2 is as follows: The strain gauge template is applied to the substrate composite layer, and a strain gauge pattern is obtained in each strain gauge region through photolithography and the cooperation of the strain gauge template.

3. The strain gauge fabrication template for solder joint coating according to claim 1, characterized in that: Step S3 is as follows: The strain gauge template is covered onto the substrate composite layer. Through photolithography and the cooperation of the strain gauge template, connecting lines that short-circuit each strain gauge pattern and conductive strips that connect all the connecting lines are obtained.

4. The strain gauge fabrication template for solder joint coating according to claim 1, characterized in that: In step S4, the electroplating process for depositing a film on the solder joint specifically involves: By energizing the conductive strip through electroplated leads, all strain gauge patterns are energized, and then all solder joints are coated.

5. A strain gauge fabrication template for solder joint coating according to claim 1 or 4, characterized in that: In step S4, the coating is either gold plating or tin plating.

6. The strain gauge fabrication template for solder joint coating according to claim 5, characterized in that: The tin plating has a thickness of 5-100 micrometers, and the gold plating has a thickness of 0.5-1 micrometer.

7. The strain gauge fabrication template for solder joint coating according to claim 1, characterized in that: Between steps S5 and S6, the following is further included: S5.1, Resistance Adjustment: Adjust the resistance of the sensitive grid of each strain gauge pattern to the required range.

8. The strain gauge fabrication template for solder joint coating according to claim 1, characterized in that: In step S1, the composite layer further includes several strain gauge monitoring areas; In step S2, after photolithography is performed on the metal foil, monitoring strain gauge patterns are further obtained in several of the strain gauge monitoring areas; In step S3, the connecting line is not short-circuited to the monitoring strain gauge pattern.

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