Method and tool for controlling tin overflow in micro-strip plate large-area welding fuzz button mounting hole

Abstract

The invention relates to the technical field of electronic assembly, in particular to a method and a tool for controlling tin overflow in fuzz button mounting holes welded on a micro-strip board in a large area, the micro-strip board is welded on a metal plate in a large area through welding flux, one or more fuzz button mounting holes are distributed in the metal plate, and the fuzz button mounting holes are used for subsequent fuzz button mounting. And interconnection with a metal bonding pad on the microstrip plate is carried out. By optimizing the design of the micro-strip plate bonding pad and the solder mask and by means of the welding tool, excessive solder is prevented from escaping into the fuzz button mounting hole during welding, the problem of tin overflowing in the fuzz button mounting hole of the micro-strip plate in large-area welding in the existing vertical interconnection microwave structure and the like is solved, and the product percent of pass and the production efficiency are greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of electronic assembly, and in particular to a method and tooling for controlling tin overflow in a large-area welding button mounting hole of a microstrip board. Background Art

[0002] With the rapid development of electronic technology, electronic products are also developing rapidly towards miniaturization, high integration and high reliability. Traditional circuits are transmitted along the plane of the product, which has the problem of occupying a large area. The use of a vertical interconnection structure can effectively compress the relative occupied area and achieve miniaturization and high integration of electronic products. The wool button includes an insulator and an elastic needle installed in the insulator. The axial end face of the wool button contacts the corresponding microstrip board pad, which can achieve welding-free vertical interconnection between boards. In the case of miniaturization and high integration, whether in the RF or low-frequency field, it is increasingly respected and widely used.

[0003] In microwave circuits, in order to ensure good grounding and heat dissipation of the microstrip board and increase the rigidity of the microstrip board, the microstrip board and the metal carrier are generally connected and fixed by large-area welding; at the same time, one or more button mounting holes are arranged in the metal carrier to achieve vertical interconnection between the microstrip boards with the help of the buttons. However, when the microstrip board and the metal carrier are welded over a large area, the molten solder tends to flow, resulting in a series of problems such as solder accumulation in the button mounting hole and short circuit connection.

[0004] To solve the above problems, currently, control measures such as increasing solder resist, reducing the amount of solder, and controlling the welding temperature are generally adopted, but there is still a 30% to 50% probability of solder accumulation or connection short circuit. At present, in order to ensure the yield rate, measures such as soldering iron desoldering are generally used for rework, which can ensure that the requirements are met in most cases. However, on the one hand, for products with a large number of fur buttons installed, the yield rate is almost zero at one time, and a large amount of rework work is faced; on the other hand, the method of soldering iron desoldering has the risk of pads falling off, and the pads falling off can only be scrapped; at the same time, in the case of small-sized fur buttons or thick metal carriers, the existing rework measures cannot be implemented.

[0005] In view of the above-mentioned defects, the inventors of the present invention finally obtained the present invention after a long period of research and practice. Summary of the invention

[0006] The purpose of the present invention is to solve the problem of solder accumulation and connection short circuit in the button mounting hole caused by the flow of molten solder when the microstrip board is welded to the metal carrier over a large area, and provide a method and tooling for controlling the tin overflow in the button mounting hole when the microstrip board is welded over a large area.

[0007] In order to achieve the above object, the present invention discloses a method for controlling tin overflow in a large-area welding button mounting hole of a microstrip board, comprising the following steps:

[0008] S1, cleaning the welding surface of the microstrip board and the welding surface of the metal plate;

[0009] S2, pre-solder;

[0010] S3, fix the microstrip board and the metal plate;

[0011] S4, install welding tooling;

[0012] S5, performing welding.

[0013] In the step S1, the welding surface of the microstrip board and the welding surface of the metal plate are both surface-plated, and the plating method is gold plating, gold plating, nickel-gold plating, silver plating or tin plating.

[0014] In the step S2, the solder is tin-based eutectic solder.

[0015] In step S5, the welding method is one of vacuum vapor phase welding, reflow welding and low temperature vacuum brazing, and the welding peak temperature is set at 20°C to 30°C above the melting point of the solder.

[0016] The present invention also discloses a welding tool for controlling tin overflow in a large-area welding button installation hole of a microstrip board, comprising a plug cap, a plug column and a vent hole. The welding tool is integrally formed and connected to the microstrip board and the metal plate through the plug column.

[0017] The welding surface of the microstrip board is provided with one or more button-mounted contact pads and microstrip board screw mounting holes. The button-mounted contact pads include metal pads and isolation belts. The isolation belts are arranged at the periphery of the metal pads.

[0018] The metal plate is provided with one or more fur button mounting holes and metal plate screw mounting holes, and the inner plating layers of the fur button mounting holes and the metal plate screw mounting holes are non-weldable plating layers.

[0019] The isolation belt is a green oil solder resist or a bare dielectric layer, the outer diameter of the isolation belt is 0.5 mm larger than the diameter of the button mounting hole, and the inner diameter of the isolation belt is 0-0.5 mm larger than the diameter of the metal pad.

[0020] The plug diameter d is Where D is the diameter of the button mounting hole, α is the thermal expansion coefficient of the welding fixture, and ΔT is the difference between the peak welding temperature and room temperature.

[0021] The diameter of the plug cap is 4mm to 8mm larger than the diameter of the plug column, the thickness of the plug cap is 2mm to 6mm, the air vent is a through hole with a diameter of 0.5mm to 1mm, and the length of the welding tool is 10mm to 16mm larger than the thickness of the metal plate.

[0022] Compared with the prior art, the beneficial effect of the present invention is that the method and tooling for controlling tin overflow in the mounting holes of the rough buttons for large-area welding of the microstrip board proposed in the present invention effectively controls the tin overflow in the mounting holes of the rough buttons for large-area welding of the microstrip board through the design of the isolation belt of the microstrip board, the control of the welding peak temperature and the design of the welding tooling, and can achieve a yield rate of 98% to 100%; effectively avoids a large amount of rework work after welding, improves production efficiency, especially for products with small-sized rough buttons or thick metal carriers, greatly improves the product yield and reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the installation of a welding tool in an embodiment;

[0024] Figure 2 A schematic diagram of the structure of the welding surface of the microstrip board of an embodiment;

[0025] Figure 3 It is a structural schematic diagram of the microstrip board fur button installation contact pad of the embodiment;

[0026] Figure 4 A schematic diagram of the metal plate welding surface structure of an embodiment;

[0027] FIG5( a ) is a schematic front view of the welding tool structure of the embodiment;

[0028] FIG5( b ) is a schematic bottom view of the welding tool structure of the embodiment;

[0029] Figure 6 This is the situation inside the installation hole of the fur button without using the method of the present application;

[0030] Figure 7 The present invention discloses a condition inside a wool button installation hole using the method of the present application.

[0031] The numbers in the figure represent:

[0032] 1-microstrip board; 11-button mounting contact pad; 111-metal pad; 112-isolation tape; 12-microstrip board screw mounting hole; 2-metal plate; 21-button mounting hole; 22-metal plate screw mounting hole; 3-welding tooling; 31-plug cap; 32-plug column; 33-vent hole; 4-solder. DETAILED DESCRIPTION

[0033] The above and other technical features and advantages of the present invention are described in more detail below in conjunction with the accompanying drawings.

[0034] Example 1

[0035] like Figure 1-4 As shown in the figure, it is a schematic diagram of the metal plate structure of this embodiment, the material is brass alloy, the thickness is 5mm, and the diameter of the button installation hole is The welding surface is plated with silver, and the button mounting holes and screw mounting holes are plated with chrome; Figure 2 As shown in the figure, it is a schematic diagram of the microstrip board structure of this embodiment, which is a multi-layer structure. The material is RO4350B of Rogers Company. The outer diameter of the isolation belt of the wool button contact pad is The inner diameter is 0.58±0.25mm, the welding surface coating is electroplated gold, the isolation belt is green oil solder resist, and the thickness is about 10μm; as shown in Figure 5, it is a schematic diagram of the welding tooling structure of this embodiment, the material is polytetrafluoroethylene, the plug cap thickness is 4mm, the diameter is 10mm, and the plug column diameter is The diameter of the air hole is 0.5mm and the overall length of the welding tooling is 15mm.

[0036] A method for effectively controlling the tin overflow in the mounting hole of the button when welding a large area of ​​a microstrip board is as follows:

[0037] Step (1) cleaning the microstrip board and the metal plate welding surface, and baking the microstrip board in an oven at 110° C. for 2-3 hours;

[0038] Step (2) Select Sn63Pb37 solder sheet, shape the solder sheet according to the shape and size of the soldering surface, then place the solder sheet on the soldering surface of the metal plate, and apply an appropriate amount of flux;

[0039] Step (3) placing the microstrip board on the solder pad so that the metal plate, the solder pad and the microstrip board form a sandwich structure, and fixing them with screws or a tooling press plate to form an assembly;

[0040] Step (4) installing welding tools in the button mounting holes of the metal plate one by one, self-checking and ensuring that they are installed in place;

[0041] Step (5) The welding temperature is set to 210°C according to the temperature curve recommended by Sn63Pb37 solder, and the welding peak temperature is set to 210°C. The assembly is welded using vacuum vapor phase welding. After welding, a 10x magnifying glass is used to check for tin overflow in the hole. Figure 6 This is the situation in the installation hole of the button without using the method of the present application. It can be seen that the solder has overflowed, which has affected the subsequent installation of the button. It must be removed by rework, and it is easy to remove it uncleanly, resulting in unqualified products. Figure 7 For the installation situation of the hair button in the hole using the method of the present application, there is no solder overflow in the hole, which meets the product design requirements.

[0042] Example 2

[0043] like Figure 1-4 As shown in the figure, it is a schematic diagram of the metal plate structure of this embodiment, the material is aluminum alloy, the thickness is 10mm, and the diameter of the button installation hole is The welding surface is plated with silver, and the inner layer of the button mounting hole and the screw mounting hole is conductive oxide; Figure 2 As shown in the figure, it is a schematic diagram of the microstrip board structure of this embodiment, which is a multi-layer structure. The material is RO4350B of Rogers Company. The outer diameter of the isolation belt of the wool button contact pad is The inner diameter is 0.5±0.05mm, the welding surface coating is electroplated gold, the isolation belt is green oil solder resist, and the thickness is about 10μm; as shown in Figure 5, it is a schematic diagram of the welding tooling structure of this embodiment, the material is polytetrafluoroethylene, the plug cap thickness is 4mm, the diameter is 8mm, and the plug column diameter is The diameter of the air hole is 0.5mm and the overall length of the welding tooling is 20mm.

[0044] The specific process steps are the same as in Example 1.

[0045] By adopting the above process method, the tin overflow in the mounting hole of the large-area welding button of the microstrip board can be effectively controlled, and the yield rate can be achieved by 98% to 100%. It effectively avoids a large amount of rework work after welding and improves production efficiency, especially for products with small-sized buttons or thick metal carriers, which greatly improves the product yield rate and reduces costs.

[0046] The above description is only a preferred embodiment of the present invention, which is only illustrative and not restrictive of the present invention. Those skilled in the art understand that many changes, modifications, and even equivalences may be made to the present invention within the spirit and scope defined by the claims of the present invention, but all of them will fall within the scope of protection of the present invention.

Claims

1. A method for controlling tin overflow in a large-area welding button mounting hole of a microstrip board, characterized in that: The following steps are involved: S1, cleaning the welding surface of the microstrip board and the welding surface of the metal plate; S2, pre-solder; S3, fix the microstrip board and the metal plate; S4, install welding tooling; S5, performing welding.

2. A method for controlling tin overflow in a button mounting hole during large-area welding of a microstrip board as claimed in claim 1, characterized in that: In the step S1, the welding surface of the microstrip board and the welding surface of the metal plate are both surface-plated, and the plating method is gold plating, chemical gold plating, nickel-gold plating, silver plating or tin plating.

3. A method for controlling tin overflow in a button mounting hole of a microstrip board during large-area welding as claimed in claim 1, characterized in that: In step S2, the solder is tin-based eutectic solder.

4. A method for controlling tin overflow in a button mounting hole during large-area welding of a microstrip board as claimed in claim 1, characterized in that: In step S5, the welding method is one of vacuum vapor phase welding, reflow welding and low temperature vacuum brazing, and the welding peak temperature is set at 20°C to 30°C above the melting point of the solder.

5. A welding tool for controlling tin overflow in the installation hole of a button when welding a large area of ​​a microstrip board, characterized in that: It comprises a plug cap, a plug column and a vent hole. The welding tool is integrally formed and made of polytetrafluoroethylene. The welding tool is connected with the microstrip plate and the metal plate through the plug column.

6. A welding tool for controlling tin overflow in a button mounting hole during large-area welding of a microstrip board as claimed in claim 5, characterized in that: The welding surface of the microstrip board is provided with one or more button-mounted contact pads and microstrip board screw mounting holes. The button-mounted contact pads include metal pads and isolation belts. The isolation belts are arranged at the periphery of the metal pads.

7. A welding tool for controlling tin overflow in a button mounting hole during large-area welding of a microstrip board as claimed in claim 6, characterized in that: The metal plate is provided with one or more fur button mounting holes and metal plate screw mounting holes, and the inner plating layers of the fur button mounting holes and the metal plate screw mounting holes are non-weldable plating layers.

8. A welding tool for controlling tin overflow in a button mounting hole during large-area welding of a microstrip board as claimed in claim 6, characterized in that: The isolation belt is a green oil solder resist or a bare dielectric layer, the outer diameter of the isolation belt is 0.5 mm larger than the diameter of the button mounting hole, and the inner diameter of the isolation belt is 0-0.5 mm larger than the diameter of the metal pad.

9. A welding tool for controlling tin overflow in a button mounting hole during large-area welding of a microstrip board as claimed in claim 7, characterized in that: The plug diameter d is Where D is the diameter of the button mounting hole, α is the thermal expansion coefficient of the welding fixture, and ΔT is the difference between the welding peak temperature and room temperature.

10. A welding tool for controlling tin overflow in a button mounting hole during large-area welding of a microstrip board as claimed in claim 5, characterized in that: The diameter of the plug cap is 4mm to 8mm larger than the diameter of the plug column, the thickness of the plug cap is 2mm to 6mm, the air vent is a through hole with a diameter of 0.5mm to 1mm, and the length of the welding tool is 10mm to 16mm larger than the thickness of the metal plate.

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