Through hole reflow soldering tinning method for connector

Abstract

The invention relates to a through hole reflow soldering tinning method for a connector, which comprises the following steps of: installing a tinning die in a tinning support plate, installing a steel mesh above the tinning die, filling a tin storage groove of the tinning die with solder paste, removing the steel mesh, picking up the tinning die, and installing the connector on a printed board. The tinning die is installed at the position of a welding through hole of a connector, a to-be-welded product is assembled and formed, the to-be-welded product assembled with the tinning die, a printed board and the connector is fed into a reflow oven, soldering tin in the tinning die is melted through heat, the melted soldering tin flows into the through hole due to the capillary and gravity effects, tinning of the through hole piece is achieved, and the soldering tin is welded to the connector. And after the to-be-welded product is taken out of the reflow boiler, the tinning mold is removed, and through hole reflow soldering is completed. In a word, the method has the advantages of being low in machining cost, short in machining period, high in tinning efficiency, wide in application range and high in welding qualification rate.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic product assembly and processing, and in particular relates to a through-hole reflow soldering tinning method for connectors. Background Art

[0002] Many electronic products in the aviation field use plug-in devices, such as connectors. When there are hundreds of connectors with a total of thousands of pins that need to be soldered, the traditional selective wave soldering method has the problems of low soldering efficiency, insufficient tin filling rate, and easy generation of soldering defects such as bridging, which can no longer meet the needs. At present, more through-hole reflow soldering technology is used, which can greatly improve the assembly efficiency and tinning pass rate; through-hole reflow soldering technology refers to the method of filling solder paste into the hole, arranging it to the edge of the hole, or putting a prefabricated solder ring on the top of the pin, arranging solder in the pin hole, the edge of the hole or above the hole, and melting the solder through the reflow oven. The molten solder fills / flows into the hole to achieve welding. However, the existing through-hole reflow soldering method has the problems of high tinning cost, difficult to control the amount of solder paste and poor adaptability to high-density printed circuit boards.

[0003] The existing through-hole reflow soldering tinning method still has the following problems during use: the tin paste is injected into the hole in the form of injection, the tinning efficiency is low, and the amount of solder paste is difficult to control; the solder paste is injected into the hole in the form of steel screen printing, and each new printed circuit board needs to develop a new steel screen and new test printing parameters, which increases costs and affects efficiency; during the plug-in process after the solder paste is injected into the hole, the pin is easy to push the solder paste out, resulting in insufficient solder; the solder paste is printed on the edge of the hole in the form of steel screen printing, and each new printed circuit board needs to open a new steel screen and new test printing parameters, which increases costs and affects efficiency, and printing the solder paste on the edge of the hole requires occupying the area on both sides of the through hole of the printed circuit board, which is not suitable for high-density printed circuit boards; the through hole spacing is small When solder paste is printed on the edge of the hole, it is disturbed by hot air and machine vibration during the welding process. When the solder between adjacent through-hole pins melts, it is easy to gather together, causing a short circuit, or insufficient tin on some pins. For some printed circuit boards with thicker thickness and higher device layout density, it is often necessary to use a stepped steel mesh or an overprinted steel mesh, resulting in higher processing costs. In addition, when the steel mesh is used to tin the high-density printed circuit board components with solder paste, when the demand for solder paste is too large, the steel mesh is thick and difficult to demold. In some processes that use prefabricated solder rings for tinning, there is not only the problem of short circuit when the solder ring melts, but also the problem of high customization cost and long installation time of prefabricated solder rings, resulting in increased costs and reduced efficiency.

[0004] Therefore, there is an urgent need for a through-hole reflow soldering tinning method for connectors to solve the above-mentioned problems. Summary of the invention

[0005] In view of this, the present invention proposes a through-hole reflow soldering tinning method for connectors, which is applied to the technical field of electronic product assembly and can solve the existing technical problems of high processing cost, long processing cycle and low product success rate.

[0006] In order to achieve the above technical objectives, the specific technical solutions adopted by the present invention are:

[0007] A through-hole reflow soldering tinning method for a connector comprises the following steps:

[0008] S1. Install the tinning mold into the tinning carrier plate, install the steel mesh above the tinning mold, fill the solder paste into the tin storage tank of the tinning mold, remove the steel mesh, and pick up the tinning mold;

[0009] S2. Install the connector on the printed circuit board, install the tinning mold on the soldering through hole of the connector, and assemble to form a product to be soldered;

[0010] S3, sending the product to be soldered, which is assembled with the tinning mold, printed circuit board, and connector, into a reflow oven, using heat to melt the solder in the tinning mold, and the melted solder flows into the through hole due to capillary and gravity effects, thereby achieving tinning of the through-hole parts;

[0011] S4, after the product to be soldered comes out of the reflow oven, remove the tinning mold and complete the through-hole reflow soldering;

[0012] The tinning mold in step S1 includes a mold bottom plate and a plurality of tin storage tanks arranged on the mold bottom plate, wherein the plurality of tin storage tanks are all opened upward and are evenly distributed on the top of the mold bottom plate;

[0013] The steel mesh in step S1 is provided with a plurality of tinning through holes matching the shape of the tinning mold, and the plurality of tinning through holes are evenly distributed on the surface of the steel mesh;

[0014] The tinning carrier plate in step S1 includes a plurality of mold mounting grooves matching the shape of the tinning mold, and the position of each mold mounting groove corresponds to the position of the corresponding tinning through hole in the horizontal direction during the process of filling the solder paste, and each mold mounting groove is located below the corresponding tinning through hole.

[0015] Furthermore, in step S2, the connector is provided with a plurality of upwardly extending plug pins, the plurality of plug pins extend vertically upward into the printed circuit board, and a plurality of tin storage tanks on the tinning mold are arranged in a one-to-one correspondence with the positions of the plug pins in the horizontal direction.

[0016] Furthermore, in step S2, the connector is provided with two connector mounting holes which open upward, and the two connector mounting holes are respectively located horizontally outside the plurality of connector pins.

[0017] Furthermore, in step S3, the solder paste is filled into the tin storage tank of the tinning mold by a silk screen printing method, wherein the filling of the solder paste is performed by a scraper.

[0018] Furthermore, in step S1, two horizontal ends of the mold bottom plate are provided with fixing through holes opening upward, and the two fixing through holes are respectively located on the outer sides of the plurality of tin storage tanks.

[0019] Furthermore, in step S1, the shape of the tin storage tank is a rectangular tank, and the multiple tin storage tanks are distributed in two rows, and the tin storage tanks in each row are evenly distributed in the lateral direction.

[0020] Furthermore, in step S1, the opening area and thickness of the tin storage tank inside the tinning mold meet the following requirements:

[0021]

[0022] S is the opening area of ​​the tin storage tank of the tinning mold, t1 is the thickness of the tinning mold, r1 is the radius of the connector pin at the soldering position, r2 is the radius of the soldering through hole, r3 is the radius of the through-hole surface pad, t2 is the thickness of the printed circuit board, k is the volume ratio of the solder paste alloy, μ, and the empirical coefficient.

[0023] By adopting the above technical solution, the present invention can also bring the following beneficial effects:

[0024] 1. The present invention mentions a through-hole reflow soldering tinning method for connectors, which can meet the qualified tinning requirements of through-hole reflow soldering of plug-in devices, solves the problem of high-density printed circuit board components having no tinning space and the problem of short circuits easily occurring in through-hole reflow soldering of fine-pitch through-hole devices, resulting in poor tinning, and has the advantages of low cost, less preparation work, batch processing, and high tinning efficiency. Moreover, the developed tinning mold can be used in printed circuit board components with different layouts when the printed circuit board thickness is similar, the connector pin spacing is similar, and the connector pin size is similar. It has strong versatility and is very suitable for promotion.

[0025] 2. The present invention mentions a through-hole reflow soldering tinning method for connectors. Compared with the original through-hole reflow soldering process without mold protection, during the welding process, a tinning mold is used to protect the solder paste when it melts and flows. It has good protection performance and can borrow space from the height direction to obtain a smaller printed circuit board surface area occupancy rate, thereby solving the problem of occupying a large surface area on both sides of the through-hole pins of the printed circuit board during tinning. Compared with the original technology, it does not require multiple adjustments to the steel mesh, can ensure the tinning amount of solder paste, improve the accuracy of tinning, and can be used for connector pins with multiple rows of fine-pitch through holes, thereby expanding the scope of use.

[0026] 3. The present invention mentions a through-hole reflow soldering tinning method for connectors, which can effectively solve the problems of demolding difficulty, easy short circuit after welding, and empty soldering of some pins caused by the use of steel mesh demolding method in the through-hole reflow soldering process, and achieves more than 99% one-time successful assembly, avoiding multiple production of steel meshes when introducing new products, while reducing the rework rate, reducing the manpower, material and time losses caused by rework, and saving economic costs. The tinning mold has a simple structure and is easy to produce, process and assemble, and can be used in through-hole reflow soldering technology in a variety of special scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 It is a schematic diagram of the connection structure of the tinning mold and the printed circuit board during the tinning process in the specific implementation manner of the present invention;

[0029] Figure 2 It is a schematic diagram of the connection structure between the tinning mold and the steel mesh during the tinning mold filling process according to a specific embodiment of the present invention;

[0030] Figure 3 It is a schematic diagram of the connection structure between the tin storage tank and the mold bottom plate in a specific embodiment of the present invention;

[0031] Figure 4 It is a schematic diagram of the connection structure between the mold installation groove and the upper tin carrier plate in a specific embodiment of the present invention;

[0032] Figure 5 It is a structural schematic diagram of a connector in a specific implementation manner of the present invention;

[0033] Figure 6 It is a schematic diagram of the structure of the steel mesh in a specific embodiment of the present invention;

[0034] Figure 7 It is a structural schematic diagram of a printed circuit board in a specific implementation manner of the present invention;

[0035] Figure 8 It is a schematic diagram of the connection structure of the welding through hole and the printed circuit board in a specific embodiment of the present invention;

[0036] Among them: 1. Steel mesh; 2. Tinning mold; 3. Tinning carrier board; 4. Printed circuit board; 5. Connector; 6. Mold base plate; 7. Tin storage tank; 8. Fixing through hole; 9. Mold mounting groove; 10. Plug mounting hole; 11. Plug pin; 12. Tinning through hole; 13. Screw mounting hole; 14. Welding through hole; 15. Through hole surface pad; 16. Mold clamping groove. DETAILED DESCRIPTION

[0037] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0038] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0039] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present invention, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0040] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention. The drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0041] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects described may be practiced without these specific details.

[0042] In one embodiment of the present invention, Figures 1 to 8 As shown, the present invention provides a through-hole reflow soldering tinning method for a connector 5, comprising the following steps:

[0043] Step S1, installing the tinning mold 2 into the tinning carrier plate 3, installing the steel mesh 1 above the tinning mold 2, filling the solder paste into the opening of the tinning mold 2 by a scraper, removing the steel mesh 1, and picking up the tinning mold 2;

[0044] Step S2, installing the connector 5 to a designated position on the printed circuit board 4, and installing the tinning mold 2 to the welding through hole 14 of the connector 5 to form a product to be welded;

[0045] Step S3, sending the product to be soldered, which is assembled with the tinning mold 2, the printed circuit board 4, and the connector 5, into a general equipment reflow furnace, using heat to melt the solder in the tinning mold, and the melted solder flows into the soldering through hole 4 due to capillary and gravity effects, thereby achieving tinning of the connector 5;

[0046] Step S4: After the product to be soldered leaves the reflow furnace, the tinning mold 2 is removed, and finally the through-hole reflow soldering is completed.

[0047] In this example, all tolerances in the tinning mold 2 are controlled at ±0.05mm; the tinning mold 2 includes a mold base plate 6 and a plurality of tin storage tanks 7 arranged on the mold base plate 6, and the plurality of tin storage tanks 7 are all opened upward and are evenly distributed on the top of the mold base plate 6; a plurality of tinning through holes 12 matching the shape of the tinning mold 2 are arranged on the steel mesh 1, and the plurality of tinning through holes 12 are evenly distributed on the surface of the steel mesh 1; the tinning carrier plate 3 includes a plurality of mold mounting grooves 9 matching the shape of the tinning mold 2, and the position of each mold mounting groove 9 corresponds to the position of the corresponding tinning through hole 12 in the horizontal direction during the process of filling the solder paste, and each mold mounting groove 9 is located below the corresponding tinning through hole 12.

[0048] In this example, the radius r1 of the pin of the connector 5 is 0.25 mm, the radius r2 of the soldering through hole 14 is 0.35 mm, the radius r3 of the through hole surface pad 15 is 0.5 mm, the through hole surface pad 15 is arranged on the top of the soldering through hole 14, the thickness t2 of the printed circuit board 4 is 3.5 mm, the volume ratio k of the solder alloy is 0.5, and the opening area and thickness of the tinning mold 2 are calculated according to the following formula:

[0049]

[0050] S. The opening area of ​​the tin storage tank 7 of the tinning mold 2; t1, the thickness of the tinning mold 2; r1, the radius of the pin 11 to be soldered; r2, the radius of the soldering through hole 14; r3, the radius of the through hole surface pad 15; t2, the thickness of the printed circuit board 4; k, the volume ratio of the solder paste alloy; μ, the empirical coefficient, the opening area and thickness of the tinning mold 2 obtained according to the empirical coefficient:

[0051]

[0052] According to the distribution of components on the printed circuit board 4 and the distribution of the connector pins 11 on the connector 5, the tin storage tank 7 is determined to be a rectangle with a length of L = 2.2 mm and a width of W = 0.9 mm. The area of ​​the tin storage tank 7 is calculated as follows:

[0053] S=L*W=1.98mm2

[0054] The tinning mold 2 and the tinning carrier plate 3 are made of 6061 aluminum alloy. The surface is not plated. The empirical coefficient μ is 0.9. Calculate the thickness of the tinning mold 2

[0055]

[0056] If the material or surface coating of the tinning mold 2 and the tinning carrier plate 3 is replaced, it is necessary to determine the opening area and make a test piece. The new μ is formulated by picking up the residual solder volume in the mold mounting groove 9 during the tinning mold 2 from the tinning carrier plate 3; for the convenience of processing, t1 is taken as 0.9mm, and the size of the tin storage tank 7 is L*W*t1=2.2mm*0.9mm*0.9mm.

[0057] The distribution and orientation of the welding through holes 14, the size and distribution and orientation of the screw mounting holes 13, and the distribution of components on the printed circuit board 4 are designed. The screw mounting holes 13 and the welding through holes 14 are all arranged on the upper surface of the printed circuit board 4. The tin storage groove 7 is in the shape of a rectangular groove. The multiple tin storage grooves 7 are distributed in two rows. The tin storage grooves 7 in each row are evenly distributed in the horizontal direction. The horizontal ends of the mold bottom plate 6 are provided with fixed through holes 8 opening upward. The two fixed through holes 8 are respectively located on the outsides of the multiple tin storage grooves 7, and the size and orientation are consistent with the screw mounting holes 13.

[0058] The tinning carrier 3 is designed according to the outer dimensions of the tinning mold 2 and the number of connectors 5 to be welded on a single printed circuit board 4. In this example, a total of ten connectors 5 are used on the printed circuit board 4. In order to facilitate the subsequent removal of the tinning mold 2 from the tool mounting groove, the size of the mold mounting groove 9 is slightly larger than the outer dimensions of the tinning mold 2. The length and width of the mold mounting groove 9 are respectively 0.1mm larger than the length and width of the tinning mold 2. In order to ensure that the surface of the steel mesh 1 is flush with the surface of the tinning mold 2 after the subsequent installation of the steel mesh 1, the depth of the mold mounting groove 9 is less than the thickness of the tinning mold 2 by 0.1mm, and is designed to be 0.8mm. In order to facilitate the clamping of the tinning mold 2 after tinning is completed, a mold clamping groove 16 is provided in the middle of the mold mounting groove 9. The mold mounting groove 9 and the mold clamping are both located on the upper surface of the tinning carrier 3, and the size of the mold clamping groove 16 is 10mm*3.0mm.

[0059] According to the outer dimensions of the tinning mold 2 and the orientation of the mold mounting groove 9, the thickness of the steel mesh 1 is set to 0.1 mm, the size of the tinning through hole 12 is slightly larger than the outer dimensions of the tinning mold 2, and the length and width of the tinning through hole 12 are respectively larger than the length and width of the tinning mold 2 by 0.05 mm.

[0060] The connector 5 in this example is provided with a plurality of upwardly extending plug pins 11, which are vertically extended upward into the printed circuit board 4, and the plurality of tin storage tanks 7 on the tinning mold 2 are arranged in a one-to-one correspondence with the horizontal positions of the plug pins 11. The connector 5 is also provided with two upwardly opening plug mounting holes 10, which are respectively located horizontally outside the plurality of plug pins 11.

[0061] In short, the present invention has the advantages of low processing cost, short processing cycle, high tinning efficiency, wide application range and high welding qualification rate.

[0062] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A through-hole reflow soldering method for connectors, characterized in that: The following steps are involved: S1, installing the tinning mold (2) into the tinning carrier plate (3), installing the steel mesh (1) above the tinning mold (2), filling the solder paste into the tin storage tank (7) of the tinning mold (2), removing the steel mesh (1), and picking up the tinning mold (2); S2, installing the connector (5) on the printed circuit board (4), installing the tinning mold (2) at the welding through hole (14) of the connector (5), and assembling to form a product to be welded; S3, sending the product to be soldered, which is assembled with the tinning mold (2), the printed circuit board (4), and the connector (5), into a reflow furnace, using heat to melt the solder in the tinning mold (2), and the melted solder flows into the soldering through hole (14) due to capillary and gravity effects, thereby achieving tinning of the connector (5); S4, after the product to be soldered comes out of the reflow oven, remove the tinning mold (2) to complete the through-hole reflow soldering; The tinning mold (2) in step S1 comprises a mold bottom plate (6) and a plurality of tin storage grooves (7) arranged on the mold bottom plate (6), wherein the plurality of tin storage grooves (7) are all opened upward and are evenly distributed on the top of the mold bottom plate (6); The steel mesh (1) in step S1 is provided with a plurality of tinning through holes (12) whose shapes match those of the tinning mold (2), and the plurality of tinning through holes (12) are evenly distributed on the surface of the steel mesh (1); The tinning carrier plate (3) in step S1 comprises a plurality of mold mounting grooves (9) whose shapes match those of the tinning mold (2); the position of each mold mounting groove (9) corresponds to the position of the corresponding tinning through hole (12) in the horizontal direction during the process of filling the solder paste; and each mold mounting groove (9) is located below the corresponding tinning through hole (12).

2. A through-hole reflow soldering method for connectors as claimed in claim 1, characterized in that: In step S2, the connector (5) is provided with a plurality of connector pins (11) extending upward, the plurality of connector pins (11) vertically extend upward into the printed circuit board (4), and a plurality of tin storage tanks (7) on the tinning mold (2) are arranged in a one-to-one correspondence with the positions of the connector pins (11) in the horizontal direction.

3. A through-hole reflow soldering method for connectors as claimed in claim 2, characterized in that: In the step S2, the connector (5) is further provided with two plug-in mounting holes (10) opening upward, and the two plug-in mounting holes (10) are respectively located horizontally outside the plurality of plug-in pins (11).

4. A through-hole reflow soldering method for connectors as claimed in claim 3, characterized in that: In the step S3, the solder paste is filled into the tin storage tank (7) of the tinning mold (2) by a silk screen printing method, wherein the filling of the solder paste is performed by a scraper.

5. A through-hole reflow soldering method for connectors as claimed in claim 4, characterized in that: In step S1, the two horizontal ends of the mold bottom plate (6) are provided with fixing through holes (8) opening upward, and the two fixing through holes (8) are respectively located on the outer sides of the plurality of tin storage tanks (7).

6. A through-hole reflow soldering method for connectors as claimed in claim 5, characterized in that: In the step S1, the tin storage groove (7) is in the shape of a rectangular groove, and the plurality of tin storage grooves (7) are distributed in two rows, and the tin storage grooves (7) in each row are evenly distributed in the transverse direction.

7. A through-hole reflow soldering method for connectors as claimed in claim 6, characterized in that: In the step S1, the opening area and thickness of the tin storage tank (7) inside the tinning mold (2) meet the following requirements: S is the opening area of ​​the tin storage tank (7) of the tinning mold (2), t1 is the thickness of the tinning mold (2), r1 is the radius of the connector pin (11) at the soldering position, r2 is the radius of the soldering through hole (14), r3 is the radius of the through hole surface pad (15), t2 is the thickness of the printed circuit board (4), k is the volume ratio of the solder paste alloy, μ, and the empirical coefficient.

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