CN114054883A

CN114054883A - Method for manufacturing selective welding nozzle, selective welding nozzle and selective welding assembly

Info

Publication number: CN114054883A
Application number: CN202010772382.5A
Authority: CN
Inventors: 覃仁树; 王永元; 李柏霖
Original assignee: DELTA ELECTRONICS (JIANGSU) Ltd
Current assignee: DELTA ELECTRONICS (JIANGSU) Ltd
Priority date: 2020-08-04
Filing date: 2020-08-04
Publication date: 2022-02-18
Anticipated expiration: 2040-08-04
Also published as: CN114054883B

Abstract

The invention provides a manufacturing method of a selective welding nozzle, the selective welding nozzle and a selective welding assembly, wherein the manufacturing method of the selective welding nozzle comprises the following steps: step S1, processing the industrial pure iron to obtain a matrix of the nozzle; step S2, nitriding the substrate to form a nitriding layer on the surface of the substrate; step S3, silver plating is carried out on the substrate processed in the step S2, so that a silver plating layer is formed on the surface of the nitriding layer; step S4, forming a nano silver layer on the surface of the silver plating layer; step S5, performing thermal oxidation on the substrate processed in step S4 to obtain the nozzle. The selective welding nozzle manufactured by the method has a composite structure; the corrosion resistance prolongs the service life of the nozzle; the energy consumption in the welding process is reduced due to good heat conductivity.

Description

Method for manufacturing selective welding nozzle, selective welding nozzle and selective welding assembly

Technical Field

The invention relates to the field of welding, in particular to a manufacturing method of a selective welding nozzle, the selective welding nozzle and a selective welding assembly.

Background

The selective wave soldering technology is a newly developed technology in the SMT technology, and the emergence of the technology greatly meets the assembly requirements of high-density and diversity mixed PCB boards. The selective wave soldering has the advantages of independent setting of welding spot parameters, small thermal shock to a PCB, small spraying amount of soldering flux, strong welding reliability and the like, and is gradually becoming an indispensable welding technology of a complex PCB.

In selective soldering, solder is pumped into a nozzle located in a tin bath. When solder is drawn into the nozzle, a small solder wave is generated and flows back into the tin bath.

The existing nozzles generally have the disadvantages of short life and poor thermal conductivity. On one hand, the nozzle is easy to corrode and damage (for example, a groove appears) due to the low purity of the material adopted by the nozzle substrate, and the surface appearance is changed and can not be used continuously; on the other hand, because the surface of the nozzle is not plated or only plated with a layer of tin, the thermal conductivity of the nozzle is poor, and the heat at the bottom of the nozzle cannot be better conducted to the tin and a welding point, so that the energy consumption is increased.

In addition, the nozzles with different specifications need to be replaced according to the specifications of different products in the selection welding process, so that the nozzles are easy to install and replace in the selection welding process, and the positions of the nozzles are consistent before and after replacement each time.

In order to solve the defects in the prior art, the application provides a manufacturing method of a selective welding nozzle, the selective welding nozzle and a selective welding assembly which solve the technical problems.

Disclosure of Invention

In order to solve the above technical problems, the present invention provides a method for manufacturing a selective welding nozzle, comprising the steps of:

step S1, processing the industrial pure iron to obtain a matrix of the nozzle;

step S2, nitriding the substrate to form a nitriding layer on the surface of the substrate;

step S3, silver plating is carried out on the substrate processed in the step S2, so that a silver plating layer is formed on the surface of the nitriding layer;

step S4, forming a nano silver layer on the surface of the silver plating layer;

step S5, performing thermal oxidation on the substrate processed in step S4 to obtain the nozzle.

In one embodiment, in step S1, the method further includes: the iron content of the substrate is 99.50-99.995%, the carbon content is less than or equal to 0.04%, and the roughness of the inner surface and the outer surface of the substrate is 0.02-0.08 micrometer.

In one embodiment, in step S2, the method further includes: the thickness of the nitriding layer is 1-1000 microns.

In one embodiment, in step S3, the method further includes: the thickness of the silver coating is 1-50 microns.

In one embodiment, in step S5, the method further includes: and through thermal oxidation treatment, the nano silver layer is converted into a nano silver oxide surface structure.

The invention also provides a corrosion-resistant selective welding nozzle with good thermal conductivity, which comprises:

the base body is made of industrial pure iron;

the nitriding layer is positioned on the surface of the substrate;

a silver coating layer positioned on the surface of the nitriding layer;

and the nano silver oxide surface structure is positioned on the surface of the silver plating layer.

In one embodiment, the silver coating is formed by rack plating and is coated on the nitriding layer, the nano silver oxide surface structure is obtained by thermal oxidation treatment of a nano silver coating, and the nano silver oxide surface structure is coated on the silver coating.

In one embodiment, the thickness of the silver coating is 1 to 50 μm, and the average diameter of the silver oxide particles of the nano silver oxide surface structure is 1 to 100 nm.

In one embodiment, the roughness of the inner surface and the outer surface of the nozzle is 0.02-0.08 micrometers, and the thickness of the nitriding layer is 1-1000 micrometers; the iron content of the substrate is 99.5-99.995%, and the carbon content is less than or equal to 0.04%.

The invention also provides a selective welding assembly which comprises a magnetic ring, a connector and a nozzle, wherein the magnetic ring is sleeved on the connector, the nozzle is clamped on the magnetic ring, and the magnetic ring attracts the nozzle through magnetic force.

In an embodiment, the connector includes a base and a convex column, the base and the convex column are hollow cylinders with different outer diameters, the convex column extends from the radial direction of the base, the inside of the convex column is communicated with the inside of the base, and the magnetic ring is sleeved on the convex column.

In one embodiment, the nozzle has an inlet with an inner diameter smaller than an outer diameter of the base, the base supporting the inlet.

In one embodiment, the magnet ring is made of samarium cobalt or alnico magnet, and the surface of the magnet ring is provided with a chromium nitride coating.

In one embodiment, the magnetic ring and the connector are in interference fit, and the interference range is 0.01 mm-0.09 mm.

In an embodiment, an inner diameter of the magnetic ring is smaller than an outer diameter of the convex column.

In one embodiment, the nozzle and the magnetic ring are in clearance fit, and the clearance amount ranges from 0.01mm to 0.09 mm.

In one embodiment, an inner diameter of a joint portion of the magnetic ring and the nozzle is larger than an outer diameter of the magnetic ring.

In an embodiment, the welding assembly further includes a fixing clamping groove and an inner nozzle, and the fixing clamping groove connects the connecting port and the inner nozzle.

In one embodiment, the inner nozzle has an inner layer and a chromium nitride coating, the inner layer is made of industrial pure iron, the iron content of the inner layer is 99.5-99.995%, and the carbon content is less than or equal to 0.04%.

In one embodiment, the selective soldering nozzle with the composite structure manufactured by the method has the advantages of long service life, good heat conductivity and good wettability of tin liquid, can save production and manufacturing cost and reduce energy consumption, and is very suitable for industrial application and popularization.

Compared with the existing nozzle, the selective welding nozzle and the manufacturing method thereof at least have the following advantages and effects:

1. the nozzle base material has high purity and extremely low carbon content, slows down the electrochemical corrosion rate of carbon as a cathode in the using process of the nozzle, and prolongs the service life of the nozzle;

2. nitriding treatment is carried out on the base body, so that the corrosion rate of the base body is further slowed down, the base body of the nozzle is protected from being corroded by air and the like, and the service life of the nozzle is prolonged;

3. the silver coating has high thermal conductivity, so that heat in a tin bath can be better conducted to tin waves and welding spots, and because the heat can be rapidly conducted through the silver coating, the heat loss is reduced, and the energy consumption in the production process is reduced;

4. the nano silver oxide can improve the heat-conducting property of the nozzle, and the nano silver oxide super-hydrophilic tin liquid improves the wettability of the nozzle and the tin liquid, so that the tin liquid is better adsorbed on the surface of the nozzle, the nozzle is further protected from being corroded by air, and the service life of the nozzle is prolonged.

The selective welding assembly of the present application has at least the following advantages: the nozzle is convenient to detach, replace and maintain, the magnetic ring and the nozzle are in clearance fit, the position of the nozzle is consistent before and after replacement at each time, welding is facilitated, and welding quality is improved.

Drawings

FIG. 1 is a flow chart of a method of making a selective welding nozzle.

Fig. 2 is a schematic view of a selective welding nozzle.

FIG. 3 is an enlarged view of a portion of the selective welding nozzle.

Fig. 4A is an exploded view of the three-dimensional structure of the selective welding assembly.

Fig. 4B is a perspective view of a selectively welded assembly.

FIG. 5 is a partial cross-sectional view of a selectively welded assembly.

Fig. 6 is a schematic structural view of a magnetic ring.

Fig. 7 is an assembly view of the hanger and the base.

Wherein the reference numerals are:

nozzle 10

Head 101

Middle part 102

Bottom 103

Base 110

Nitrided layer 111

Silver coating layer 112

Nano silver oxide surface structure 113

Nozzle outlet 1011

Nozzle inlet 1031

Magnetic ring 20

Connecting head 30

Base 301

Convex column 302

First screw part 303

Fixing clamp groove 40

Second screw part 401

Inner spout 50

Hanging tool 60

Joint part A

Detailed Description

The detailed description and technical contents of the present invention are described below with reference to the accompanying drawings.

FIG. 1 is a flow chart of a method of fabricating a selective welding nozzle; fig. 2 is a schematic view of a selective welding nozzle. Fig. 3 is a partial enlarged view of the selective welding nozzle. Referring to fig. 1 to 3 together, the method for manufacturing a selective welding nozzle of the present invention includes the following steps:

step S1, a commercially pure iron is processed to obtain the base body 110 of the nozzle 10.

The chemical components of the industrial pure iron are mainly iron, the electromagnetic property is good, the magnetic induction property is high, the diamagnetism is low, and the industrial pure iron can be used as an electromagnetic material. In some embodiments, the matrix has an iron content in the range of 99.5 to 99.995% and a carbon content of less than 0.04%.

Through right industrial pure iron carries out lathe work and correct grinding and forms the base member 110 of nozzle 10, and the inside and outside surface roughness Ra scope of base member after the correct grinding processing is 0.02 ~ 0.08 micron, and above-mentioned roughness scope is favorable to tin to be moist on nozzle 10 and is favorable to improving the cladding quality. The surface roughness value in the present application can be measured by using the existing surface roughness and detection method of the workpiece, for example, the roughness can be obtained by scribing 5 cm in the height direction on the head 101 of the nozzle 10 by using a surface roughness tester.

The substrate 110 may be shaped as a cylindrical structure, a conical structure, or a composite structure. Further, the base body of the cylindrical structure forms a cylindrical straight hole nozzle; the base body of the conical structure forms a conical nozzle; the matrix of the composite structure forms a composite structure nozzle. As shown in FIG. 2, the head 101 (the end near the welding point) of the substrate 110 is hollow and cylindrical, the middle 102 of the substrate 110 is hollow and conical, and the bottom 103 (the end far from the welding point) of the substrate is straight hole structure. The invention is not limited to this, the shape of the base body can be flexibly designed according to actual requirements, the shape of the base body determines the shape of the nozzle 10, and the head part 101, the middle part 102 and the bottom part 103 of the base body in the application refer to the same parts as the head part 101, the middle part 102 and the bottom part 103 of the nozzle.

Step S2, performing nitriding treatment on the substrate 110 to form a nitrided layer 111 on the surface of the substrate 110.

In some embodiments, the apparatus for performing step S2 is a pressure nitriding furnace, and a nitrided layer is formed on the surface of the substrate. The specific operation process is as follows: placing the base material obtained in the step S1 in a pressurizing nitriding furnace; setting the temperature and pressure of a pressurized nitriding furnace, for example, setting the temperature at about 550 ℃ and the pressure at about 5atm (5 standard atmospheres); starting the booster nitriding furnace to perform nitriding treatment, and obtaining a nitrided layer 111 after a predetermined time, for example, 5 hours. The temperature, pressure and time of the nitriding furnace can be selected according to the material and the thickness of the nitriding layer. Wherein, the nitriding layer is attached to the inner surface and the outer surface of the matrix, and the thickness of the nitriding layer ranges from 1 micron to 1000 microns.

In step S3, the substrate 110 processed in step S2 is silvered to form a silvered layer 112 on the surface of the nitrided layer 111.

In some embodiments, the apparatus performing step S3 is a rack, and the silver coating is performed on the surface of the nitrided layer to form the silver coating 112. Referring to fig. 7, which shows an assembly diagram of the hanger and the substrate, one end of the hanger 60 is pressed inside the substrate, for example, the supporting point of the hanger is close to the inlet of the substrate (the bottom of the substrate far from the welding point), and the height direction of the substrate is perpendicular to the bottom of the plating tank during hanging plating, so that the plating thickness at the outlet of the substrate (the head of the substrate close to the welding point) is uniform.

The thickness of the silver coating 112 is 10-12 microns, silver coating is carried out on the surface of the substrate according to reasonable current parameters, the roughness of the surface of the substrate cannot be influenced, and the surface roughness range after silver coating is still 0.02-0.08 microns.

Step S4, forming a nano-silver layer on the surface of the silver plating layer 112.

In some embodiments, after the substrate 110 is silvered, the nano-silver coating is grown directly in the silvered layer using an in-situ electrochemical fabrication process. A three-electrode system is adopted, the nozzle 10 (comprising a substrate 110, a nitriding layer and a silver coating layer, which is referred to as the nozzle 10 in the embodiment) in the manufacturing process is a working electrode, a platinum mesh is a counter electrode, a saturated calomel electrode is a reference electrode, the nozzle 10 is subjected to electrochemical constant current oxidation in an acidic sodium sulfate solution, then electrochemical constant current reduction is performed in an alkaline sodium sulfate solution, and a nano silver layer directly grows on the nozzle 10.

The specific operation process is as follows: cleaning the manufactured nozzle 10 and naturally airing; preparing an acidic sodium sulfate solution and an alkaline sodium sulfate solution; inserting the manufactured nozzle 10, the saturated calomel electrode and the platinum net into three holes of an electrolytic cell and respectively connecting the three electrodes of an electrochemical workstation; setting a positive constant current value of an electrochemical workstation, adding an acidic sodium sulfate solution into an electrolytic cell, carrying out electrochemical constant current oxidation, and growing a silver oxide crystal structure on a silver plating layer in situ; taking out the oxidized nozzle 10, cleaning and drying; respectively inserting the oxidized nozzle 10, the saturated calomel electrode and the platinum net into three holes of an electrolytic cell, setting a negative constant current value of an electrochemical workstation, adding an alkaline sodium sulfate solution into the electrolytic cell for electrochemical constant current reduction, stopping the constant current reduction process when the potential is reduced to be below-1.6V and basically keeps stable, and reducing all silver oxide crystals into nano silver at the moment; taking out the nozzle 10 with the nano silver layer, cleaning and drying.

In some embodiments, the nozzle 10 (including the substrate 110, the nitriding layer, the silver coating and the nano-silver layer) under fabrication is also subjected to a thermal oxidation treatment, and the nano-silver layer is replaced with a nano-silver oxide structure. The specific operation process is as follows: putting the manufactured nozzle 10 into an oven and then vacuumizing; charging air with one atmospheric pressure after drying treatment, and raising the temperature to 350 ℃ at the temperature rise speed of 30 ℃/S; and (3) keeping the temperature for 60 minutes, then closing the oven, and naturally cooling the nozzle 10 to room temperature along with the oven to obtain the nano silver oxide surface structure 113. Wherein, the technological parameters of the thermal oxidation treatment can be obtained through experiments aiming at different materials.

After the thermal oxidation treatment, the nozzle 10 is manufactured, and the nozzle 10 is taken out, packaged by dust-free paper and then placed in a plastic bag for sealing and storage.

The nozzle with the composite structure is obtained according to the manufacturing process. As shown in fig. 3, the selective soldering nozzle 10 is a composite structure, and sequentially includes a substrate 110, a nitriding layer 111, a silver plating layer 112, and a nano silver oxide surface structure 113.

The substrate 110 is made of industrial pure iron, the iron content is 99.5-99.995%, and the carbon content is below 0.04%. The substrate 110 has an iron content of at least 99.5% and 99.995%, although 99.7% is also possible. The carbon content of the substrate 110 is at least 0.04% and 0, but may be 0.02%. In one embodiment, the carbon content of the substrate 110 is 0.03%, the iron content is 99.9%, and the remaining elements are unavoidable residual elements, and the extremely low carbon content can slow down the electrochemical corrosion rate of carbon as a negative electrode during use, thereby prolonging the service life of the nozzle 10. The current alternative welding nozzle on the market is unusable after about two weeks of use due to erosion, whereas the nozzle 10 of the present invention lasts up to 26 days.

The nitriding layer 111 is positioned on the inner surface and the outer surface of the substrate 110, and the thickness of the nitriding layer 111 is 1-1000 microns. The nitrided layer has a thickness of at least 1 micron and 1000 microns, although 500 microns are also possible. The nitriding treatment is performed on the base body 110, so that the electrochemical corrosion resistance of the nozzle 10 in the production and use processes is improved, and the service life of the nozzle 10 is prolonged.

The silver plating layer 112 is located on the inner surface and the outer surface of the nitriding layer 111, and the thickness range of the silver plating layer 112 is 1-50 micrometers. The silver layer has a thickness of at least 1 micron and 50 microns, but may be 25 microns. The metal with the best heat conduction effect is silver, and the wettability of silver and tin is good, and the nozzle 10 of the present invention comprises a silver-plated layer, and has high heat conduction and wettability. The bottom 103 of the nozzle 10 (nozzle inlet) is immersed in the tin bath, the rest of the nozzle is outside the tin bath, and a solder wave is formed at the nozzle outlet, which solder wave is plated with tin at the solder joint. On one hand, the tin bath transmits heat to tin in the tin bath, the temperature of the tin in the tin bath is higher, the bottom 103 of the nozzle is contacted with the tin in the tin bath, and the heat in the tin bath is rapidly transmitted to tin waves at the outlet of the nozzle and welding spots corresponding to the nozzle through a silver coating layer of the nozzle; the temperature of the tin wave exposed in the flowing nitrogen protective atmosphere is lower than that of tin in the tin bath, and the temperature of the tin wave and the temperature of a welding spot are quickly increased through heat conduction of the silver coating, so that the tin wave and the welding spot are favorable for welding. On the other hand, the silver coating can quickly transfer heat, the heat loss is small, the set temperature of the tin bath is properly reduced, the tin wave can reach the ideal temperature of 300 ℃ for example, the welding is completed, and the lower the temperature in the tin bath is, the lower the set reasonable temperature in the tin furnace is, so that the energy consumption in the production process is reduced.

The nano silver oxide surface structure 113 is laid on the silver coating layer 112, and the average diameter range of silver oxide particles of the nano silver oxide surface structure is 1-100 nanometers. The silver oxide particles of the nano silver oxide surface structure have an average diameter of at least 1 nm and 100 nm, although 50 nm is also possible. Nanomaterials have many unique properties such as large surface, high number of surface active sites, superplastic ductility, catalytic properties, chemical activity, physical properties, etc. The characteristics of the nano material can improve the heat conducting property and the wetting property of the nozzle, and are beneficial to improving the welding quality. The surface of the nozzle is provided with a nano silver oxide surface structure which is super-hydrophilic to tin liquid, so that the wetting performance of the nozzle and the tin liquid is improved, the wetting between the nozzle and the tin liquid enables the soldering tin to be better adsorbed on the surface of the nozzle during welding, the nozzle is interrupted in tin spraying, and the attached tin on the surface of the nozzle can be further protected from being corroded by air when the nozzle is not sprayed with tin, so that the service life of the nozzle is prolonged.

In some embodiments, the selective welding nozzle of the present invention is a composite structure, and referring again to fig. 2, the nozzle 10 includes a head portion 101, a middle portion 102, and a bottom portion 103. Wherein the head 101 is cylindrical and comprises a nozzle outlet 1011; the middle portion 102 is conical, for example, at a cone angle of 30 degrees; the bottom 103 is a straight bore that includes a nozzle inlet 1031. Preferably, the nozzle 10 is integrally formed, i.e., the head 101, middle 102 and bottom 103 of the nozzle are integrally formed. The diameter of the nozzle 10 is gradually reduced from the bottom 103 to the head 101, which meets the hydromechanics requirement, controls the speed of the upward flow of the tin liquid in the nozzle, and improves the welding quality.

The nozzle, especially the nozzle head 101, has a surface roughness Ra of 0.02-0.08 micrometers, which is beneficial to wetting tin on the nozzle and improving the quality of a plating layer. The nozzle tip 101 has a surface roughness Ra of at least 0.02 microns and 0.08 microns, but may be 0.05 microns. The nozzle has proper surface roughness, so that the friction between the molten tin and the nozzle is increased, the upward-flowing speed of the molten tin in the nozzle, the speed of the redundant molten tin flowing back into a tin bath and the speed of the molten tin wave emitted to a welding spot are favorably controlled, the upward-flowing speed and the reflow speed of the molten tin, the appearance of the generated molten tin wave and the like are optimized, the welding quality is improved, and the false soldering and the missing soldering are avoided.

Fig. 4A is an exploded view of a perspective structure of a selectively welded assembly, fig. 4B is a perspective structural view of the selectively welded assembly, and fig. 5 is a partial sectional view of the selectively welded assembly. As shown in fig. 4A and 5, the selective welding assembly 1 includes the nozzle 10, the magnetic ring 20, the connector 30, the fixing slot 40, and the inner nozzle 50. The magnetic ring 20 is sleeved on the connector 30, the nozzle 10 is clamped on the magnetic ring 20, namely, the magnetic ring 20 is sleeved on the connector 30 with the magnetic ring 20, and the magnetic ring 20 attracts the nozzle 10 through magnetic force.

The joint between the magnetic ring 20 and the nozzle 10 is referred to as a joint a, for example, in fig. 5, the joint a corresponds to a joint between a straight hole structure and a tapered structure. The inner diameter of the engagement portion a is larger than the outer diameter of the magnetic ring, and between the nozzle inlet 1031 and the engagement portion a, the inner diameter of the nozzle 10 is larger than the outer diameter of the magnetic ring 20, i.e. the magnetic ring 20 is in clearance fit with the nozzle 10, so that the nozzle 10 can rotate along the magnetic ring 20. In some embodiments, the difference between the inner diameter of the joint portion A and the outer diameter of the magnetic ring is in the range of 0.01-0.09 mm. Namely, the range of the gap between the magnetic ring 20 and the nozzle 10 is 0.01-0.09 mm. The gap between the magnetic ring 20 and the nozzle 10 is at least 0.01mm and 0.09mm, and certainly can be 0.05 mm.

Can adopt threaded mode installation nozzle and connector among the current scheme, rotatory nozzle arrives the spacing point and accomplishes the installation. Because of the influence of factors such as wind direction and gravity, the molten tin in molten tin bath and the nozzle all can incline to one side slightly, adopts screw thread mode to make one side of nozzle be located molten tin inclined one side all the time, compares other positions this side nozzle and can receive more serious corrosion, if the unilateral serious corruption of nozzle, whole nozzle also can not continue to use. The rotating angle of the nozzle is adjusted through the magnetic ring, the nozzle in the inclined direction of the molten tin is flexibly switched, the corrosion degree of the nozzle in each direction is balanced, and the whole nozzle cannot be used due to serious corrosion in a certain direction of the nozzle. The magnetic ring and the nozzle are in clearance fit, the rotating angle can be adjusted regularly in the using process of the nozzle, so that the molten tin is more uniformly corroded on the nozzle, unilateral corrosion cannot be generated, the appearance of the inlet of the nozzle is favorably kept, and the service life of the nozzle is prolonged. By utilizing the magnetic ring, the nozzle is convenient to disassemble, replace and maintain, and the position of the nozzle is kept consistent before and after each installation. Therefore, the relative position relation between the nozzle and the welding spot can be adjusted once, and after the nozzle is replaced or maintained, the relative position relation between the nozzle and the welding spot is kept unchanged, so that the welding accuracy and consistency are improved.

The connector 30 includes a base 301 and a protruding column 302, the base 301 and the protruding column 302 are both hollow cylinders, the protruding column 302 extends from the base 301 in a radial direction, and preferably, the base 301 and the protruding column 302 are integrally formed. The outer diameter of the base 301 is larger than the outer diameter of the convex column 302, but the inner diameter of the base 301 is the same as the inner diameter of the convex column 302, the inner part of the convex column 302 is communicated with the inner part of the base 301, and the inner part of the connector 30 is communicated with the inner part of the nozzle 10. Referring to fig. 5, the magnetic ring 20 is sleeved on the convex column 302; when the connector 30 with the magnetic ring 20 is clamped at the joint a of the nozzle 10, the magnetic ring attracts the nozzle by magnetic force. The nozzle inlet 1031 has an inner diameter smaller than an outer diameter of the base 30, and the base 301 supports the nozzle inlet 1031. As shown in fig. 4B, the outer diameter of the nozzle inlet 1031 is equal to the outer diameter of the base 301, but the present invention is not limited thereto and can be flexibly designed according to actual requirements as long as the base can support the nozzle. The nozzle is sleeved on the convex column with the magnetic ring and supported by the base, and the stability of the nozzle is ensured through the magnetic force of the magnetic ring and the support of the base.

The inner diameter of the magnetic ring 20 is smaller than the outer diameter of the convex column 302, i.e. the convex column 302 and the magnetic ring are tightly matched. When the magnetic ring and the convex column 302 are installed, the connector 30 is cooled to a proper temperature, according to the principle of expansion with heat and contraction with cold, the outer diameter of the convex column 302 is reduced, when the outer diameter of the convex column 302 is reduced to be slightly smaller than the inner diameter of the magnetic ring, the magnetic ring 20 is sleeved, the connector expands after the temperature is raised, the magnetic ring and the convex column 302 are tightly matched, and the cold interference fit between the connector 30 and the magnetic ring 20 is realized. In some embodiments, the difference between the outer diameter of the stud 302 and the inner diameter of the magnetic ring 20 is in the range of 0.01-0.09 mm. Namely the interference range between the magnetic ring and the connector is 0.01-0.09 mm. The interference magnitude between the magnetic ring and the nozzle is at least 0.01mm and 0.09mm, and the interference magnitude between the magnetic ring and the nozzle can be 0.05 mm.

It should be noted that the shapes of the connector, the magnetic ring and the nozzle can be flexibly designed, as long as the three can be assembled correspondingly. The material of the connector 30 may be the same as that of the nozzle, or may be other materials as long as the requirement of corrosion resistance is satisfied.

One end of the base of the connector 30 is provided with a convex column 302, and the other end is provided with a first threaded portion 303. In this embodiment, the first thread portion 303 is an internal thread. The fixing groove 40 is located at the joint of the connecting head 30 and the inner nozzle 50. The fixing clip 40 has a second thread portion 401 and a third thread portion (not shown), which are disposed opposite to each other and have hollow interior portions for mutual communication. The inside and connector intercommunication of second screw thread portion 401, and second screw thread portion 401 is the internal thread fit connection of external screw thread and connector for realize the equipment of connector 30 and fixed slot 40.

One end of the inner nozzle 50 has a fourth threaded portion (not shown), which in this embodiment is an internal thread. The inside of the third thread part 402 is communicated with the inner nozzle 50, and the third thread part 402 is matched and connected with the inner thread of the inner nozzle by external threads, so that the inner nozzle 50 and the fixed clamping groove 40 are assembled.

It should be noted that the threaded connection is only one implementation manner, and the connection head, the inner nozzle, and the fixing slot may be assembled by other manners, such as a magnetic ring, a bolt, and the like.

The fixing clamping groove 40 is used for connecting the inner spray pipe 50 and the connector 30, and fixing a welding module (comprising a tin bath, a welding assembly, an electromagnetic pump and the like) on a selective welding machine table. The fixing slot 40 may be made of titanium alloy. It should be noted that the shapes of the connector, the fixing slot 40 and the inner nozzle 50 can be flexibly designed, as long as the three can be assembled correspondingly.

The inner spray pipe 50 is hung in the tin bath in a suspension mode through the fixed clamping groove 40, the electromagnetic pump generates electromagnetic force, and the electromagnetic force acts on the welding assembly to enable tin in the tin bath to sequentially pass through the inner spray pipe, the fixed clamping groove and the connector to enter the nozzle and be sprayed out of the nozzle to the corresponding welding point.

In the invention, the nozzle and the tin liquid are wet, so that the tin wave is stable, and the welding quality is ensured; the inner spray pipe is not wetted with the tin liquid, so that the resistance of the tin liquid when flowing in the inner spray pipe is reduced, and the inner spray pipe also needs to have magnetic conductivity and anti-corrosion capability. In one embodiment, the inner nozzle has an inner layer of commercially pure iron and a surface of chromium nitride coating adhered to the inner and outer surfaces of the inner layer. The content of each element in the industrial pure iron used for the inner layer is the same as that of the nozzle base body 110, but the invention is not limited thereto.

Referring to fig. 5 and 6 again, fig. 6 is a schematic structural view of the magnetic ring 20. The magnetic ring 20 is made of a samarium cobalt magnet or an alnico magnet which can resist the high temperature of 350 ℃, and the surface of the magnet ring is provided with a chromium nitride coating to protect the magnetic ring from being corroded by molten tin. In one embodiment, the magnetic ring 20 has an outer diameter of 14.04 to 14.045mm and an inner diameter of 13.55 to 13.555 mm. The inner diameter of the joint A between the nozzle 10 and the magnetic ring 20 is 14.19 to 14.275 mm. The magnetic ring 20 attracts the nozzle through magnetic force, the magnetic ring 20 and the nozzle 10 are in clearance fit, and the rotation angle can be adjusted regularly in the use process of the nozzle 10, so that the molten tin is more uniformly corroded on the nozzle, unilateral corrosion cannot be caused, the appearance of the nozzle inlet 1031 is kept, and the service life of the nozzle is prolonged.

For the following detailed description of the embodiments, please refer to fig. 1-6.

First embodiment

The selective welding nozzle in the first embodiment of the invention has a composite structure, and sequentially comprises a substrate 110, a nitriding layer 111, a silver coating layer 112 and a nano silver oxide surface structure 113. The carbon content of the base body 110 was 0.03%, the iron content was 99.9%, and the content of the remaining elements was 0.07%, and the nozzle base body 110 was formed by turning and finish grinding, and the roughness of the inner and outer surfaces of the nozzle base body 110 after finish grinding was 0.02 μm. And (3) nitriding the nozzle matrix 110 in a pressurized nitriding furnace for 5 hours by pressurized gas to obtain a surface nitriding layer 111 with the thickness of 1000 microns, wherein the temperature of the pressurized nitriding furnace is 550 ℃, and the pressure is 5 atm. And (3) coating the silver fog on the surface of the nozzle by using a hanger to form a silver coating 112 on the surface of the nitriding layer 111, wherein the thickness of the silver coating 112 is 10 micrometers, and the surface roughness of the substrate 110 is not influenced after coating, namely the surface roughness is still 0.02 micrometer. And then the selective welding nozzle with the silver coating 112 on the surface is prepared by an in-situ electrochemical preparation method to obtain the selective welding nozzle with the silver coating 112 on the surface being a nano silver coating. And then carrying out thermal oxidation treatment on the selective soldering nozzle with the nano silver layer as the outermost layer, and converting the nano silver layer into a nano silver oxide surface structure 113 to obtain the selective soldering nozzle with the nano silver oxide surface structure 113 as the outermost layer, wherein the average diameter range of silver oxide particles of the nano silver oxide surface structure 113 is 100 nanometers.

The shape of the nozzle in this embodiment is a composite structure comprising a head portion 101, a middle portion 102 and a bottom portion 103. The head 101 is a hollow cylinder, the middle 102 is a hollow cone, the bottom 103 is a straight hole, the hollow cylinder, the hollow conical tube and the straight hole are concentric and coaxial, and the hollow cylinder, the hollow conical tube and the straight hole are all communicated up and down.

The inlet diameter of the nozzle is the largest and the outlet diameter is smaller than the inlet diameter. The outer diameter of the nozzle inlet 1031 is 22mm, the inner diameter is 14.19mm, the inner diameter of the nozzle outlet is 10.81mm, the length of the nozzle is 47mm, the length of the hollow conical tube is 15mm, the length of the hollow column body is 20mm, and the length of the straight hole is 12 mm. The dimensions of the nozzle may be designed according to the shape of the PCB board, the components to be soldered, etc.

Second embodiment

The process flow steps for manufacturing the selective welding nozzle, the shape and the specific size of the selective welding nozzle in the second embodiment of the invention are basically the same as those of the first embodiment, and the selective welding nozzle in the embodiment is different from the first embodiment in that the material composition of the substrate 110 contains 0.02% of carbon, 99.9% of iron and 0.08% of the rest elements, the roughness of the inner and outer surfaces of the nozzle substrate 110 is 0.05 micron, the thickness of the nitriding layer 111 is 800 micron, the thickness of the silver plating layer 112 is 30 micron, and the average diameter range of silver oxide particles of the nano silver oxide surface structure 113 is 50 nm.

Third embodiment

The selective welding assembly of the third embodiment of the present invention includes a nozzle 10, a magnetic ring 20, a connector 30, a fixing slot 40 and an inner nozzle 50, and the selective welding nozzle of the first embodiment is used in this embodiment. The magnet ring 20 is made of a samarium cobalt magnet resistant to a high temperature of 350 ℃, and has a chromium nitride coating on the surface. When the magnetic ring 20 and the connector 30 are installed, the connector 30 is cooled to a proper temperature to reduce the outer diameter of the convex column 302, and then the magnetic ring 20 is sleeved, so that the cold interference fit between the connector 30 and the magnetic ring 20 is realized. After the magnetic ring 20 is installed, the bottom of the connector 30 is communicated with the inner nozzle 50 through the fixing clamping groove 40, the nozzle 10 is sleeved on the magnetic ring 20, the magnetic ring 20 sucks the nozzle 10 through magnetic force, and the assembly of the selective welding assembly is completed. The assembly sequence is not fixed and can be flexibly adjusted according to actual conditions. When the nozzle is assembled, the position of the nozzle is required to be regularly rotated or the severely corroded nozzle is replaced after the tin wave is unstable, and the connector, the magnetic ring and the inner spray pipe are fixed on the whole machine in daily use. Meanwhile, nozzles with different specifications and inner diameters need to be switched according to different PCB product requirements.

In this embodiment, the outer diameter of the magnetic ring 20 is 14.042mm, the inner diameter is 13.552mm, the thickness of the magnetic ring 20 is 0.49mm, and the inner diameter of the joint a of the nozzle 10 and the magnetic ring 20 is 14.19 mm. The outer diameter 14.042mm of the magnetic ring 20 is smaller than the inner diameter 14.19mm of the joint part A, and the difference is 0.148 mm. Namely, the magnetic ring 20 is in clearance fit with the nozzle, and the clearance is 0.148 mm. The magnetic ring 20 is sleeved on the convex column 302, and the outer diameter of the convex column 302 is 13.58 mm. The inner diameter 13.552mm of the magnetic ring 20 is smaller than the outer diameter 13.58mm of the convex column 302, and the difference is 0.028 mm. Namely, the magnetic ring and the convex column are in interference fit, and the interference magnitude is 0.028 mm.

The connector and the nozzle of the selective welding assembly are convenient to detach and replace; the magnetic ring and the nozzle are in clearance fit, so that the position of the nozzle is consistent before and after each replacement, and the rotation angle can be regularly adjusted in the using process, so that the molten tin is more uniformly corroded on the nozzle, unilateral corrosion cannot be caused, the appearance of the nozzle inlet is favorably kept, and the service life of the nozzle is prolonged.

The selective welding nozzle has a composite structure, the nozzle matrix is formed by fine grinding after turning industrial pure iron, and nitriding treatment is carried out on the surface after machining, so that the electrochemical corrosion rate of carbon serving as a cathode in the using process is slowed down by extremely low carbon content, and the service life of the nozzle is prolonged. The silver coating has high thermal conductivity, can be better with the heat conduction of tin bath to tin ripples and solder joint, because the heat can be through the quick conduction of silver coating, the heat loss reduces to the energy consumption in the production process has been reduced. The nano silver oxide can improve the heat-conducting property of the nozzle, and the nano silver oxide super-hydrophilic tin liquid improves the wettability of the nozzle and the tin liquid, so that the tin liquid is better adsorbed on the surface of the nozzle, the nozzle is further protected from being corroded by air, and the service life of the nozzle is prolonged. The nano silver treatment on the surface improves the heat conductivity and the wettability of the nozzle with tin liquid, does not need organic surface protection, and saves the cost.

Claims

1. A method for manufacturing a selective welding nozzle is characterized by comprising the following steps:

step S1, processing the industrial pure iron to obtain a matrix of the nozzle;

2. The method of manufacturing a selective welding nozzle according to claim 1, wherein in step S1, the method further comprises: the iron content of the substrate is 99.50-99.995%, the carbon content is less than or equal to 0.04%, and the roughness of the inner surface and the outer surface of the substrate is 0.02-0.08 micrometer.

3. The method of manufacturing a selective welding nozzle according to claim 1, wherein in step S2, the method further comprises: the thickness of the nitriding layer is 1-1000 microns.

4. The method of manufacturing a selective welding nozzle according to claim 1, wherein in step S3, the method further comprises: the thickness of the silver coating is 1-50 microns.

5. The method of manufacturing a selective welding nozzle according to claim 1, wherein in step S5, the method further comprises: and through thermal oxidation treatment, the nano silver layer is converted into a nano silver oxide surface structure.

6. A selective welding nozzle, comprising:

the base body is made of industrial pure iron;

the nitriding layer is positioned on the surface of the substrate;

a silver coating layer positioned on the surface of the nitriding layer;

7. The selective welding nozzle of claim 6, wherein the silver coating is formed by rack plating and applied to the nitriding layer, and the nano silver oxide surface structure is obtained by thermal oxidation of a nano silver layer, the nano silver oxide surface structure being applied to the silver coating.

8. The selective soldering nozzle according to any one of claims 6 or 7, wherein the silver plating layer has a thickness of 1 to 50 μm, and the silver oxide particles of the nano silver oxide surface structure have an average diameter of 1 to 100 nm.

9. A selective welding nozzle according to any one of claims 6 or 7, wherein the nozzle has an inner and outer surface roughness of 0.02 to 0.08 microns; the thickness of the nitriding layer is 1-1000 microns; the iron content of the substrate is 99.5-99.995%, and the carbon content is less than or equal to 0.04%. .

10. A selective welding assembly comprising a magnetic ring, a connector and a nozzle as claimed in any one of claims 6 to 9, the magnetic ring being fitted over the connector, the nozzle being clamped to the magnetic ring, the magnetic ring attracting the nozzle by magnetic force.

11. The selective welding assembly of claim 10, wherein the connector comprises a base and a stud, the base and the stud are hollow cylinders with different outer diameters, the stud extends radially from the base, the interior of the stud is connected to the interior of the base, and the magnetic ring is disposed on the stud.

12. The selective welding assembly of claim 11, wherein the nozzle has an inlet with an inner diameter smaller than an outer diameter of the base, the base supporting the inlet.

13. The selective welding assembly of any one of claims 10-12, wherein the magnet ring is made of samarium cobalt or alnico magnets and a surface of the magnet ring has a chromium nitride coating.

14. The selective welding assembly of any one of claims 10-12 wherein the magnetic ring and the connector are in interference fit, the interference range being 0.01mm to 0.09 mm.

15. The selective welding assembly of claim 11, wherein an inner diameter of the magnet ring is smaller than an outer diameter of the stud.

16. The selective welding assembly of any one of claims 10-12, wherein the nozzle is in clearance fit with the magnet ring, and the amount of clearance is in a range of 0.01mm to 0.09 mm.

17. The selective welding assembly of any one of claims 10-12, wherein an inner diameter of a junction of the magnet ring and the nozzle is greater than an outer diameter of the magnet ring.

18. The selective welding assembly of claim 11, further comprising a fixed clamping slot and an inner nozzle, wherein the fixed clamping slot connects the connector and the inner nozzle.

19. The selective welding assembly of claim 11, wherein the inner lance has an inner layer and a chromium nitride coating, the inner layer being formed of commercially pure iron and having an iron content of 99.5-99.995% and a carbon content of 0.04% or less.