CN115460766A

CN115460766A - Through hole reflow soldering pad structure and through hole reflow soldering method

Info

Publication number: CN115460766A
Application number: CN202211220921.XA
Authority: CN
Inventors: 刘修伦
Original assignee: Goertek Techology Co Ltd
Current assignee: Goertek Techology Co Ltd
Priority date: 2022-09-30
Filing date: 2022-09-30
Publication date: 2022-12-09

Abstract

The invention discloses a through hole reflow soldering pad structure and a through hole reflow soldering method, wherein the through hole reflow soldering pad structure comprises: the PCB board is provided with a through hole; the through hole welding pad comprises a first tray body and a second tray body which are respectively arranged on two opposite sides of the PCB, and a column body arranged in the through hole, wherein the column body connects the first tray body and the second tray body, the column body is provided with a through hole for inserting pins of an inserting device, and two ends of the through hole respectively penetrate through the first tray body and the second tray body; the solder layer is arranged on one side, far away from the PCB, of the first disc body; the solder ring is arranged on one side of the solder layer, which is far away from the first disc body, and an inner hole of the solder ring can be used for the pin to pass through; the solder layer and the solder ring are used for reflowing into the through hole after being heated and melted so as to perform soldering fixation on the pin. The technical scheme of the invention can improve the reliability of through hole reflow soldering and improve the production efficiency.

Description

Through hole reflow soldering pad structure and through hole reflow soldering method

Technical Field

The invention relates to the field of electronic device packaging, in particular to a through hole reflow soldering pad structure and a through hole reflow soldering method.

Background

At present, a plug device with pins has two welding processes, one is a wave soldering process, and the other is a through hole reflow soldering process. In the wave soldering process, after other surface-mounted components are pasted on a PCB, the pins of the plug-in device are soldered through the tin-spraying wave soldering equipment. The through hole reflow soldering process can finish the chip mounting work of the PCB once, and the wave soldering is not needed after surface mounting, so that the chip mounting process can be saved.

In the conventional through hole reflow soldering process, in order to fix the pins, two common processing methods are used, one is to locally thicken the reflow device packaging part of the screen plate to increase the amount of tin, the other is to reduce the diameter of the via holes of the fixed devices, and the through holes are filled with less soldering tin to fix the pins. But the problems of poor welding such as insufficient solder joint, insufficient tin-climbing and the like can be found in the reflow soldering of the through hole in the application process. Simply increase steel mesh opening and increase the tin volume, produce tin pearl easily in welding process, lead to the risk of the inside short circuit of high density PCB board. Simply reduce the via hole diameter of PCB board, soldering tin on the one hand can reduce the welding reliability too little, and on the other hand is because the aperture is less, and the device pin is difficult to insert and leads to the material loading difficulty in the hole.

Disclosure of Invention

The invention mainly aims to provide a through hole reflow soldering pad structure, aiming at improving the reliability of through hole reflow soldering and improving the production efficiency.

In order to achieve the above object, the present invention provides a via reflow pad structure, including:

the PCB is provided with a through hole; and

the through hole welding pad comprises a first tray body and a second tray body which are respectively arranged on two opposite sides of the PCB, and a column body arranged in the through hole, wherein the column body connects the first tray body and the second tray body, the column body is provided with a through hole for inserting pins of an inserting device, and two ends of the through hole respectively penetrate through the first tray body and the second tray body;

the solder layer is arranged on one side, far away from the PCB, of the first disc body; and

the solder ring is arranged on one side of the solder layer, which is far away from the first disc body, and an inner hole of the solder ring can be penetrated by the pin; the solder layer and the solder ring are used for reflowing into the through hole after being heated and melted so as to perform soldering fixation on the pin.

In one embodiment, the inner bore diameter of the solder ring is greater than the inner bore diameter of the first disk, and the outer diameter of the solder ring is less than the outer diameter of the first disk.

In one embodiment, the inner hole diameter of the solder ring is 1.2 to 1.3 times the inner hole diameter of the first disc, and the outer diameter of the solder ring is 0.7 to 0.8 times the outer diameter of the first disc.

In one embodiment, the thickness of the solder layer ranges from 0.08mm to 0.12mm.

In one embodiment, the diameter of the pin is L, the diameter of the inner hole of the first tray body is D1, and the diameter of the inner hole of the second tray body is D2, wherein D1 > D2 > L.

In one embodiment, D1 ≧ L +2A, D2= L + A, where A is a constant greater than zero.

In one embodiment, the inner wall surface of the through hole is an inclined surface extending from the periphery of the inner hole of the first tray body towards the periphery of the inner hole of the second tray body in an inclined manner.

In one embodiment, the cross-sectional dimension of the via decreases gradually from the first tray toward the second tray.

In one embodiment, the via hole is a truncated cone-shaped hole tapered from the first tray body toward the second tray body.

The invention also provides a through hole reflow soldering method, which comprises the following steps:

providing a PCB board provided with a through hole welding disc; the PCB is provided with a through hole, the through hole pad comprises a first tray body and a second tray body which are respectively arranged on two opposite sides of the PCB, and a column body arranged in the through hole, the column body connects the first tray body and the second tray body, the column body is provided with a through hole for inserting pins of an inserting device, and two ends of the through hole respectively penetrate through the first tray body and the second tray body;

printing a solder layer on one side of the first disc body, which faces away from the PCB;

a solder ring is attached to the surface of one side, away from the first disc body, of the solder layer;

inserting a pin of an inserting device into the through hole after penetrating through the solder ring;

and heating the PCB board subjected to the steps in a reflow furnace until the solder layer and the solder ring are melted and mixed together to reflow into the through hole so as to solder the pin.

According to the technical scheme, the solder layer (such as a tin paste layer) and the solder ring (such as a tin ring) are sequentially stacked on the top surface of the first disc body of the through hole pad, and during soldering, the solder ring and the solder layer are heated, melted and mixed together and reflow along the through hole so as to solder the pin of the plug-in device. This technical scheme only needs the attached solder ring on the surface on solder layer, and in welding process, the solder ring can melt and increase the solder volume, and then makes the solder volume of backward flow to the downthehole increase to there is sufficient solder in the downthehole when guaranteeing to weld, is favorable to the pin of more reliable fixed grafting device, guarantees welding quality. So, can promote through-hole reflow soldering's reliability, promote production efficiency.

Drawings

In order to more clearly illustrate the embodiments or technical solutions of the present invention, the drawings used in the embodiments or technical solutions of the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a cross-sectional view of a through-hole reflow pad structure according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a stacked structure of the via reflow pad structure of FIG. 1;

FIG. 3 is a top view of a solder ring and via pad stack;

fig. 4 is a flowchart illustrating a method for reflow soldering of through holes according to an embodiment of the present invention.

The reference numbers indicate:

reference numerals	Name (R)	Reference numerals	Name(s)
				10	PCB board	201	Via hole
20	Through-hole pad	30	Solder layer
				21	First disc body	40	Solder ring
22	Second plate body	50	Plug-in device
				23	Column body	51	Pin

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.

It should be noted that if directional indications (such as up, down, left, right, front, back, 8230) \8230;) are involved in the embodiment of the present invention, the directional indications are only used to explain the relative positional relationship between the components in a specific posture, the motion situation, etc., and if the specific posture is changed, the directional indications are correspondingly changed.

In addition, if there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the feature. In addition, if the meaning of "and/or" and/or "appears throughout, the meaning includes three parallel schemes, for example," A and/or B "includes scheme A, or scheme B, or a scheme satisfying both schemes A and B. In addition, technical solutions between the embodiments may be combined with each other, but must be based on the realization of the technical solutions by a person skilled in the art, and when the technical solutions are contradictory to each other or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

The invention provides a through hole reflow soldering pad structure.

Referring to fig. 1 and 2, in an embodiment of the present invention, the via reflow pad structure includes a PCB board 10, a via pad 20, a solder layer 30, and a solder ring 40. The PCB 10 is provided with a through hole; the through hole pad 20 comprises a first tray body 21 and a second tray body 22 which are respectively arranged on two opposite sides of the PCB 10, and a column 23 arranged in the through hole, wherein the column 23 connects the first tray body 21 and the second tray body 22, the column 23 is provided with a through hole 201 for inserting a pin 51 of a plug-in device 50, and two ends of the through hole 201 respectively penetrate through the first tray body 21 and the second tray body 22; the solder layer 30 is arranged on one side of the first disc body 21 far away from the PCB board 10; the solder ring 40 is disposed on a side of the solder layer 30 away from the first disc body 21, and an inner hole of the solder ring 40 is for the pin 51 to pass through; the solder layer 30 and the solder ring 40 are used to reflow into the via 201 after being melted by heat to solder and fix the pin 51.

Specifically, the PCB 10 (i.e. the printed circuit board) is provided with through holes extending in the thickness direction and penetrating through two sides of the through holes, through hole pads 20 are disposed in the through holes, the through hole pads 20 are used for pins 51 of the plug device 50 to be plugged, and the number of the through hole pads 20 is adapted to the number of the pins 51 of the plug device 50. For example, as shown in fig. 1, the plug device 50 has two pins 51, and accordingly, two through hole pads 20 are disposed on the PCB board 10, and each pin 51 of the plug device 50 can be inserted into the corresponding through hole pad 20 respectively and then soldered and fixed. For convenience of description, the following description mainly takes as an example a soldering structure of one of the leads 51 and the corresponding through hole pad 20. The via pad 20 includes opposing first and

second trays

21 and 22, and a post 23 connected between the first and

second trays

21 and 22. The first tray body 21 can be disposed on the top side of the PCB 10, the second tray body 22 can be disposed on the bottom side of the PCB 10, the column 23 is disposed in the through hole of the PCB 10, the column 23 is hollow and has a through hole 201, two ends of the through hole 201 respectively penetrate through the first tray body 21 and the second tray body 22, that is, the first tray body 21 and the second tray body 22 are both annular, the inner hole periphery of the first tray body 21 is connected with one port periphery of the through hole 201, and the inner hole periphery of the second tray body 22 is connected with the other port periphery of the through hole 201. It can be understood that, in order to enable the pin 51 of the plug device 50 to be smoothly inserted into the via 201, a certain assembly gap is generally reserved between the inner circumferential surface of the via 201 and the outer circumferential surface of the pin 51, where the assembly gap is a distance that is reserved on one side after the pin 51 is inserted into the via 201, so that the pin 51 has a large moving margin inside the via 201 after being inserted. The top surface (i.e. the side far away from the PCB 10) of the first disc body 21 can be provided with a solder layer 30 by means of screen printing, the solder ring 40 can be directly attached to the top surface of the solder layer 30 as a surface mount material, and for the convenience of attaching the solder ring 40, the solder ring 40 is made into a hollow cylinder shape, and the upper and lower surfaces are horizontally smooth. The solder ring 40 and the solder layer 30 are made of solder, and can be reflowed into the via hole 201 for soldering after being heated and melted.

In general, soldering is used for soldering electronic components, and thus the solder layer 30 may be a solder paste layer, and the solder ring 40 may be a solder ring. The following description will be given mainly taking the solder layer 30 as a solder paste layer and the solder ring 40 as a tin ring as an example. When the socket device 50 is soldered, a solder paste layer (i.e., the solder layer 30) is printed on the top surface of the first tray body 21 by a screen printing method, and the thickness of the solder paste layer is generally about 0.1 mm; then attaching the solder ring (i.e., solder ring 40) to the top surface of the solder paste layer; inserting the pin 51 of the plug device 50 into the via hole 201 after penetrating through the inner hole of the tin ring; and then placing the PCB 10 assembled with the plug-in device 50 into a reflow oven for heating, and with the rise of temperature, melting and mixing the tin ring and the tin paste layer together, reflowing into the via holes 201 to solder and fix the pins 51.

The technical scheme of the invention is that a solder layer 30 (such as a tin paste layer) and a solder ring 40 (such as a tin ring) are sequentially stacked on the top surface of a first disc body 21 of a through hole pad 20, and when in welding, the solder ring 40 and the solder layer 30 are heated, melted and mixed together to reflow along a through hole 201 so as to weld a pin 51 of a plug-in device 50. According to the technical scheme, the solder ring 40 is only required to be attached to the surface of the solder layer 30, and in the welding process, the solder ring 40 can be melted to increase the amount of the solder, so that the amount of the solder reflowing into the via hole 201 is increased, sufficient solder is arranged in the via hole 201 during welding, the pin 51 of the plug-in device 50 can be more reliably fixed, and the welding quality is ensured. So, can promote through-hole reflow soldering's reliability, promote production efficiency.

In order to make the size of the solder ring 40 (e.g., tin ring) as large as possible, it is also avoided that the solder overflows the first disk body when the solder ring 40 melts, so that the solder flows to a nearby position and poor soldering of a device at the nearby position occurs. As shown in FIG. 3, in one embodiment, the inner bore diameter of the solder ring 40 is larger than the inner bore diameter of the first disk 21, and the outer diameter of the solder ring 40 is smaller than the outer diameter of the first disk 21. Specifically, the inner hole of the solder ring 40 and the inner hole of the first tray 21 are both required to be designed to be penetrated by the pin 51 of the plug device 50, and if the inner hole diameter of the solder ring 40 is designed to be equal to the inner hole diameter of the first tray 21, the inner hole diameter of the actually produced solder ring 40 may be too small to prevent the pin 51 of the plug device 50 from penetrating due to inevitable tolerance during production and manufacturing. Therefore, during design, the inner diameter of the solder ring 40 is slightly larger than the inner diameter of the first disc 21, so as to ensure that the inner diameter of the solder ring 40 can be used for the pin 51 to pass through smoothly even if there is tolerance. The outer diameter of the solder ring 40 is smaller than the outer diameter of the first disc 21, so as to ensure that the solder ring 40 does not overflow the first disc 21 when melting, which may cause device soldering in a nearby position.

Further, the inner hole diameter of the solder ring 40 is 1.2 to 1.3 times the inner hole diameter of the first disc 21, and the outer diameter of the solder ring 40 is 0.7 to 0.8 times the outer diameter of the first disc 21. That is, the inner hole diameter of the solder ring 40 is 20% to 30% larger than the inner hole diameter of the first disc 21, and the outer diameter of the solder ring 40 is 20% to 30% smaller than the outer diameter of the first disc 21, so that the size of the solder ring 40 can be ensured to be as large as possible to increase the solder amount, and meanwhile, the solder ring 40 can be ensured not to overflow the first disc 21 when being melted to cause the continuous welding of devices at nearby positions.

The solder layer 30 is generally screen-printed on the surface of the first disc body 21, and the thickness of the solder layer 30 is generally not too thick, and in one embodiment, the thickness of the solder layer 30 is in a range of 0.08mm to 0.12mm. For example, the solder layer 30 (e.g., a layer of solder paste) can have a thickness of about 0.1 mm.

In the above embodiment, the amount of solder can be increased by adding the solder ring 40 to meet the requirement of reflow soldering of a part of the through holes of the PCB. However, because the size of the through-hole pad 20 is small, the solder ring 40 (e.g., tin ring) cannot be made large, and for some thicker PCB boards 10, the through-hole will be deeper, and the amount of solder (e.g., the amount of tin) required for the via 201 of the through-hole pad 20 will be larger. In order to further ensure the reliability of soldering and avoid the risk of poor soldering due to insufficient solder amount, the via 201 of the through-hole pad 20 needs to be further designed.

Referring to fig. 1, based on the above embodiment, in an embodiment, the diameter of the pin 51 is L, the diameter of the inner hole of the first tray 21 is D1, and the diameter of the inner hole of the second tray 22 is D2, where D1 > D2 > L. In the present embodiment, the inner hole diameter of the first tray 21 and the inner hole diameter of the second tray 22 are both larger than the diameter of the pins 51 of the plug device 50, so as to ensure that the pins 51 of the plug device 50 can be inserted smoothly. In the inserting process, the pins 51 of the inserting device 50 firstly pass through the inner holes of the first tray body 21 from top to bottom, and then are inserted into the through holes 201, and the pins 51 can be conveniently inserted due to the large diameter of the inner holes of the first tray body 21. The inner diameter of the second tray 22 may be designed to be smaller than that of the first tray 21 so that the pins 51 can be inserted.

Further, the diameter of the pin 51 is L, the diameter of the inner hole of the first tray 21 is D1, the diameter of the inner hole of the second tray 22 is D2, D1 is greater than or equal to L +2a, and D2= L + a, where a is a constant greater than zero. Specifically, the size of the via 201 of the through-hole pad 20 needs to be designed according to the diameter of the pin 51 of the connector device 50 and a certain assembly gap (a single-side reserved distance after the pin 51 is placed in the via 201) is reserved. The inner hole diameter of the first tray body 21 is at least L +2A, so that the inner hole diameter of the first tray body 21 is reserved to be large, and the pins 51 can be conveniently inserted. The inner hole diameter of the second tray 22 is L + a, and the hole diameter is smaller, but the pin 51 of the plug device 50 can be accommodated.

As shown in fig. 1, in one embodiment, the inner wall surface of the via 201 is an inclined surface extending from the inner hole periphery of the first tray 21 to the inner hole periphery of the second tray 22. In this embodiment, by setting the inner wall surface of the via hole 201 as an inclined surface, the solder flows into the via hole 201 after the solder layer 30 and the solder ring 40 are melted, and flows downwards along the inner wall surface of the via hole 201, the flowing speed of the solder can be reduced by the inclined inner wall surface, so that the solder can be ensured to fill the whole via hole 201, and the problem of empty soldering caused by the inner bubble due to the too fast flowing speed is reduced.

To further reduce the amount of solder required for the via 201, in one embodiment, the cross-sectional dimension of the via 201 decreases from the first tray 21 toward the second tray 22. Thus, compared with the conventional through hole pad adopting a cylindrical through hole with a uniform cross-sectional dimension, the volume of the through hole 201 can be reduced, and the required solder amount can be reduced.

Optionally, the through hole 201 is a truncated cone-shaped hole that tapers from the first tray 21 toward the second tray 22. Set up via hole 201 to the round platform form, compare in cylindric via hole, the volume is littleer, and required solder volume is also less, can guarantee that the solder can fill up via hole 201. And the inner wall surface of the circular truncated cone-shaped via hole 201 is an inclined surface, so that the flowing speed of the solder can be slowed down, the whole via hole 201 can be filled with the solder, and the problem of empty soldering caused by internal bubbles due to the fact that the flowing speed is too high is solved.

The amount of solder required for a conventional through-hole package and the through-hole package of the present application is calculated in conjunction with a specific embodiment. As shown in fig. 1, it is assumed that the thickness of the PCB 10 is H, the pin 51 of the plug device 50 is cylindrical with a diameter L, and the assembly gap between the pin 51 of the plug device 50 and the via 201 is a, where the assembly gap is a distance between the pin 51 and the via 201 after being placed in the via 201.

In a conventional through-hole package, the through-hole of the through-hole pad is a cylindrical hole with a uniform cross-sectional dimension, and if the through-hole needs to be filled, the volume occupied by the pin 51 of the device is removed on the basis of the whole cylindrical through-hole, the required soldering tin amount V ₁ About:

in the through-hole package of the present application, the through-hole 201 of the through-hole pad 20 is a circular truncated cone-shaped holeThe inner hole diameter D1 of the tray body 21 is (L + 2A), the inner hole diameter D2 of the second tray body 22 is (L + A), and the required solder volume V ₂ About:

as can be seen from the above equations (1) and (2): v ₂ ＜V ₁

In addition, a solder ring 40 (e.g., a tin ring) is further designed in the present application, the height of the tin ring is h, the width of the tin ring is r, and for convenience of calculation, the tin ring is placed close to the via hole 201 of the through hole pad 20, and the solder volume V provided by the tin ring ₃ About:

in the technical scheme of the application, the through hole 201 of the through hole pad 20 is in a circular truncated cone shape, the inner hole diameter of the second tray body 22 (also called bottom surface pad) of the through hole pad 20 is smaller than the inner hole diameter of the first tray body 21 (also called top surface pad), and the required soldering tin amount is smaller than that of the conventional through hole packaging as can be known from the theoretical calculation. In addition, due to the fact that the solder ring 40 (tin ring) is designed, certain tin amount can be provided for welding, sufficient tin amount is provided in the via hole 201 when welding is guaranteed, the more reliable fixing of the pin 51 of the plug-in device 50 is facilitated, and welding quality is guaranteed. Although the inner hole diameter of the second tray 22 is small, the inner hole diameter of the first tray 21 is unchanged, so that the normal insertion of the pins 51 of the plug device 50 into the through holes 201 is not influenced, and the assembly efficiency can be ensured; and the inner wall surface of the via hole 201 is in a step design with an inclined surface, when the soldering tin flows into the via hole 201 after being melted, the flowing speed of the soldering tin is reduced by the inclined surface design, the whole via hole 201 can be filled with the soldering tin, and the problem of empty welding caused by internal bubbles due to the fact that the flowing speed is too high is solved. Therefore, the risk of short circuit of PCB welding caused by insufficient soldering of through hole reflow soldering and poor solder ball generation can be solved, and the reliability of through hole reflow soldering is improved. By solving the problems, the process flow is simplified, the production efficiency is improved, and the assembly density of the circuit board, particularly the high-density circuit board, is improved.

The invention also provides a through hole reflow soldering method.

Referring to fig. 4, in an embodiment of the present invention, a through hole reflow soldering method includes the following steps:

s1, providing a PCB 10 provided with a through hole pad 20; the PCB 10 is provided with a through hole, the through hole pad 20 comprises a first tray body 21 and a second tray body 22 which are respectively arranged at two opposite sides of the PCB 10, and a column body 23 arranged in the through hole, the column body 23 connects the first tray body 21 and the second tray body 22, the column body 23 is provided with a through hole 201 for inserting a pin 51 of an inserting device 50, and two ends of the through hole 201 respectively penetrate through the first tray body 21 and the second tray body 22;

s2, printing a solder layer 30 on one side of the first disc body 21, which is far away from the PCB 10;

s3, attaching a solder ring 40 to the side, away from the first disc body 21, of the solder layer 30;

s4, inserting the pins 51 of the plug-in device 50 into the via holes 201 after penetrating through the solder ring 40;

and S5, heating the PCB 10 which is subjected to the steps in a reflow furnace until the solder layer 30 and the solder ring 40 are melted and mixed together to reflow into the through hole 201 so as to solder the pin (51).

Specifically, the following description will be given mainly taking the solder layer 30 as a solder paste layer and the solder ring 40 as a tin ring as an example. When the socket device 50 is soldered, a solder paste layer (i.e., the solder layer 30) is printed on the top surface of the first tray body 21 by a screen printing method, and the thickness of the solder paste layer is generally about 0.1 mm; then attaching the solder ring (i.e., solder ring 40) to the top surface of the solder paste layer; inserting a pin 51 of the plug-in device 50 into the via hole 201 after penetrating through an inner hole of the tin ring; and then, the PCB 10 assembled with the plug-in device 50 is placed in a reflow furnace for heating, and with the rise of the temperature, the tin ring and the tin paste layer are melted and mixed together to reflow into the via hole 201 so as to weld and fix the pin 51. Therefore, enough solder can be ensured in the via hole 201 during welding, which is beneficial to more reliably fixing the pin 51 of the plug device 50 and ensuring the welding quality. So, can promote through-hole reflow soldering's reliability, promote production efficiency.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification and the drawings, or any other related technical fields, which are directly or indirectly applied to the present invention, are included in the scope of the present invention.

Claims

1. A via reflow pad structure, comprising:

the PCB is provided with a through hole; and

2. The via reflow pad structure of claim 1, wherein an inner hole diameter of the solder ring is larger than an inner hole diameter of the first tray body, and an outer diameter of the solder ring is smaller than an outer diameter of the first tray body.

3. The via reflow pad structure of claim 2, wherein the solder ring has an inner hole diameter that is 1.2 to 1.3 times the inner hole diameter of the first tray and an outer diameter that is 0.7 to 0.8 times the outer diameter of the first tray.

4. The via reflow pad structure of claim 1, wherein the solder layer has a thickness in a range of 0.08mm to 0.12mm.

5. The via reflow pad structure of any of claims 1 to 4, wherein the leads have a diameter L, the first body has an inner hole diameter D1, the second body has an inner hole diameter D2, wherein D1 > D2 > L.

6. The via reflow pad structure of claim 5, wherein D1 ≧ L +2A, D2= L + A, where A is a constant greater than zero.

7. The via reflow pad structure of claim 5, wherein the inner wall surface of the via is beveled extending obliquely from the inner hole periphery of the first tray toward the inner hole periphery of the second tray.

8. The via reflow pad structure of claim 5, wherein the via tapers in cross-sectional dimension from the first tray toward the second tray.

9. The through-hole reflow pad structure of claim 8, wherein the via is a frustoconical hole that tapers from the first tray toward the second tray.

10. A through hole reflow soldering method is characterized by comprising the following steps:

inserting a pin of a plug-in device into the through hole after penetrating through the solder ring;