Soldering tape pressing device, string welding machine and welding method for soldering tape and battery cell

Abstract

The present application provides a solder tape pressing device, a string welding machine, and a welding method for a solder tape and a battery cell. The pressing device includes: a pressing plate; a plurality of pressing needle groups, which are arranged at intervals on the pressing plate along a first direction. Each pressing needle group has a first pressing needle and a second pressing needle. The first pressing needle and the second pressing needle are spaced apart by a preset distance along the first direction. The ends of the first pressing needle and the second pressing needle away from the pressing plate both have pressing heads; and a plurality of heating through-holes, which penetrate the pressing plate along the thickness direction of the pressing plate, and the plurality of heating through-holes are distributed at intervals along the first direction. Among them, the gap between the first pressing needle and the second pressing needle in each pressing needle group corresponds to at least one heating through-hole. The pressing device and the string welding machine of the present application can selectively heat the solder joint area by setting heating through-holes corresponding to the gaps between the pressing needle groups, which is beneficial to avoiding warping of the battery cell due to a large temperature difference and avoiding the failure of the insulating glue.

Description

Technical Field

[0001] The present application mainly relates to the field of photovoltaics, and specifically relates to a solder ribbon pressing device, a string welding machine, and a welding method for solder ribbon and solar cell. Background Art

[0002] In the production process of photovoltaics, it is necessary to weld the solder ribbon on the solar cell. The welding process is basically as follows. The solar cell realizes the welding process through an automatic string welding machine. During the welding process, the solder ribbon contacts the electrode area of the solar cell through a positioning step, and a pressing tool is used to make the solder ribbon closely adhere to the electrode surface. Subsequently, it enters a heating lamp box, and under the action of external heat sources such as infrared, hot air, and laser, the solder ribbon and the electrode of the solar cell are welded together. During single-sided welding, the solar cell will warp due to heat, and the heat radiation will cause the insulating glue on the solar cell to fail.

[0003] Therefore, how to avoid the warping of the solar cell due to heat during welding and avoid the failure of the insulating glue is an urgent problem to be solved. Summary of the Invention

[0004] The technical problem to be solved by the present application is to provide a solder ribbon pressing device, a string welding machine, and a welding method for solder ribbon and solar cell, which can avoid the warping of the solar cell due to a high temperature difference during welding and avoid the failure of the insulating glue.

[0005] The technical solution adopted by the present application to solve the above technical problem is a solder ribbon pressing device, including: a pressing plate; a plurality of pressing needle groups, the plurality of pressing needle groups are arranged on the pressing plate at intervals in a first direction, each pressing needle group has a first pressing needle and a second pressing needle, the first pressing needle and the second pressing needle are spaced apart by a preset distance in the first direction, and both ends of the first pressing needle and the second pressing needle away from the pressing plate have pressing heads; and a plurality of heating through-holes, penetrating the pressing plate in the thickness direction of the pressing plate, the plurality of heating through-holes are distributed at intervals in the first direction, wherein the gap between the first pressing needle and the second pressing needle in each pressing needle group corresponds to at least one of the heating through-holes.

[0006] In an embodiment of the present application, some of the first pressing needles are movably connected to the pressing plate along the axial direction of the first pressing needle, and some of the second pressing needles are movably connected to the pressing plate along the axial direction of the second pressing needle.

[0007] In an embodiment of the present application, the pressing plate has a plurality of pressing needle holes, one end of some of the first pressing needles away from their pressing heads is arranged in the corresponding pressing needle holes along their axial directions, and one end of some of the second pressing needles away from their pressing heads is arranged in the corresponding pressing needle holes.

[0008] In an embodiment of the present application, it further includes a plurality of springs. The springs are sleeved on a part of the first pressing needles and a part of the second pressing needles. One end of each spring abuts against the pressing plate, and the other end abuts against the pressing heads of the corresponding first pressing needles and second pressing needles.

[0009] In an embodiment of the present application, the cross-sectional area of the pressing head of the first pressing needle is larger than the cross-sectional area of the main body portion of the first pressing needle, and the cross-sectional area of the pressing head of the second pressing needle is larger than the cross-sectional area of the main body portion of the second pressing needle.

[0010] In an embodiment of the present application, a plurality of light-transmitting windows are formed in the pressing plate.

[0011] To solve the above technical problems, the present application also provides a string welding machine, including: a heating unit; and the pressing device as described above, and the pressing device is located below the heating unit.

[0012] In an embodiment of the present application, it further includes a light-shielding plate, and the light-shielding plate is disposed between the heating unit and the pressing device.

[0013] To solve the above technical problems, the present application also provides a welding method for a welding tape and a battery cell. The welding tape and the battery cell are welded by using the string welding machine as described above. During welding, the projection of the heating through-hole and the corresponding welding point along the thickness direction overlaps, and the heating unit heats the welding point corresponding to the heating through-hole through the heating through-hole.

[0014] In an embodiment of the present application, it further includes coating an intermediate substance on the welding point before welding.

[0015] The pressing device and the string welding machine of the present application can selectively heat the welding point area by setting heating through-holes corresponding to the gaps between the pressing needle groups, which is beneficial to avoiding warping of the battery cell due to a large temperature difference and avoiding the failure of the insulating glue. Description of the Drawings

[0016] To make the above objects, features, and advantages of the present application more obvious and understandable, the following detailed description of the specific embodiments of the present application is provided in conjunction with the accompanying drawings, where:

[0017] Figure 1 is a front view schematic diagram of a string welding machine according to an embodiment of the present application;

[0018] Figure 2 is a left view schematic diagram of a string welding machine according to an embodiment of the present application;

[0019] Figure 3 is a top view schematic diagram of a string welding machine according to an embodiment of the present application;

[0020] Figure 4 is Figure 1 a partial enlarged view of the part within the rectangular dashed box;

[0021] Figure 5 is Figure 4 a partial enlarged view of the circular part in;

[0022] Figure 6 is Figure 3 a partial enlarged view of the circular part in;

[0023] Figure 7 is a top view schematic diagram of a pressing plate according to an embodiment of the present application. Detailed implementation manners

[0024] To make the above objects, features and advantages of the present application more obvious and understandable, the following detailed description of the specific implementation manners of the present application is provided in conjunction with the accompanying drawings.

[0025] In the following description, many specific details are set forth in order to fully understand the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0026] As shown in the present application and the claims, unless the context clearly indicates otherwise, words such as "a", "an", "one" and / or "the" are not specifically singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0027] In addition, it should be noted that the use of words such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Without further statement, the above words have no special meaning, and therefore cannot be understood as a limitation on the protection scope of the present application. In addition, although the terms used in the present application are selected from well-known and commonly used terms, some of the terms mentioned in the specification of the present application may be selected by the applicant according to his or her judgment. Their detailed meanings are described in the relevant parts of the description herein. In addition, it is required to understand the present application not only through the actual terms used, but also through the meaning implied by each term.

[0028] The present application uses flowcharts to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the operations before or below do not necessarily need to be executed precisely in order. On the contrary, they can be executed in reverse order or simultaneously. At the same time, or other operations can be added to these processes, or one or several steps can be removed from these processes.

[0029] Figure 1 is a front view schematic diagram of a string welding machine according to an embodiment of the present application, Figure 2 is a left view schematic diagram of a string welding machine according to an embodiment of the present application, Figure 3 is a top view schematic diagram of a string welding machine according to an embodiment of the present application. Refer to Figure 1 As shown, the string welding machine 100 has a box body 110, a heating unit 120 located inside the box body 110, and a conveyor belt 130. The heating unit 120 includes components such as infrared heating lamps and hot air heaters that can be used to heat the welding tape. The conveyor belt 130 is located below the heating unit 120, and the heating unit 120 can heat the objects located on the conveyor belt 130.

[0030] The welding process of the welding tape and the battery cell is as follows. Refer to Figure 3 the top view shown, in Figure 3 , three battery cells 140 are adjacent and distributed along the first direction D1 on the conveyor belt 130, and eight welding tapes 150 are laid on each battery cell. Refer to Figure 1 As shown, Figure 1 shows the situation after the conveyor belt 130 conveys the bonded welding tape and battery cell into the box body 110. Refer to Figure 2 As shown in the left view, before the welding tape 150 and the battery cell 140 enter the box body 110, an external force is applied to the welding tape 150 towards the battery cell 140 through the pressing device 160, so that the welding tape 150 is attached to the battery cell 140. Then, the conveyor belt 130 carries the welding tape 150 and the battery cell 140 into the box body 110. Under the heating of the heating unit 120, the welding points on the welding tape 150 and the battery cell 140 are welded and connected.

[0031] It should be noted that the above description is only exemplary and does not constitute a limitation to the present application. For example, the arrangement method and quantity of the battery cells during welding are not limited to the above examples, and the specific quantity of the welding tape can be set according to actual needs and is not limited to the above eight.

[0032] The pressing device of the present application can prevent the battery cell from warping due to heat and prevent the insulating glue on the battery cell from failing.

[0033] Next, the pressing device of the present application will be described through specific embodiments.

[0034] Figure 4 is Figure 1 a partial enlarged view of the rectangular dashed box part in Figure 4 As shown, the pressing device includes a pressing plate 161, a plurality of pressing needle groups 162, and a plurality of heating through holes 163.

[0035] Specifically, the pressing plate 161 has opposite first surface 161a and second surface 161b along the thickness direction D2. Among them, asFigure 1 As shown, during welding, the first surface 161a faces the heating unit 120, and the second surface 161b faces the battery cell 140. The pressing plate 161 has a thickness H1 in the thickness direction D2, that is, the distance between the first surface 161a and the second surface 161b in the thickness direction D2 is H1. Refer to Figure 3 As shown, the pressing plate 161 has a width W1 in the first direction D1 and a length L1 in the third direction D3. It can be understood that the present application does not limit the length L1, width W1, and thickness H1 of the pressing plate 161, and they can all be set according to actual requirements.

[0036] Continue to refer to Figure 4 As shown, Figure 4 A total of 8 pressing pin groups 162 are shown in

[0037] Figure 3 Figure 4 and Figure 4 Figure 3 Figure 3 Figure 4 Figure 4 Figure 4

[0038]

[0039] Figure 5 Figure 4 Figure 6 Figure 3 Next, the pressing pin group will be described in detail through an embodiment.

[0039] Figure 5 is Figure 4 a partial enlarged view of the circled part in Figure 6 is Figure 3 a partial enlarged view of the circled part in Figure 5As shown, the needle pressing group has a first needle 162a and a second needle 162b. The axes of the first needle 162a and the second needle 162b are spaced apart by a preset distance L2 along the first direction D1. One end of the first needle 162a and one end of the second needle 162b are both connected to the pressing plate 161. The ends of the first needle 162a and the second needle 162b away from the pressing plate 161 respectively have a first pressing head 162a-1 and a second pressing head 162b-1.

[0040] In some embodiments, referring to Figure 5 As shown, the pressing plate 161 has a plurality of needle pressing holes (not shown in the figure). One end of some of the first needles 162a in the pressing device away from their first pressing heads 162a-1 is arranged in the corresponding needle pressing holes along their axial directions. One end of some of the second needles 162b in the pressing device away from their second pressing heads 162b-1 is arranged in the corresponding needle pressing holes. The above-mentioned some first needles and some second needles can move axially in their respective needle pressing holes, that is, they are movably connected to the pressing plate 161 along the thickness direction D2.

[0041] Continue to refer to Figure 5 As shown, the pressing device further includes a plurality of springs 164. Specifically, referring to Figure 5 As shown, springs 164 are sleeved on both the first needle 162a and the second needle 162b that are movably connected to the pressing plate 161. One end of the spring 164 abuts against the pressing plate 161, and the other end abuts against the first pressing head 162a-1 of the corresponding first needle 162a and the second pressing head 162b-1 of the corresponding second needle 162b. When the first pressing head 162a-1 applies pressure to the welding tape 150 to make it fit with the battery cell 140, the spring 164 sleeved on the first needle 162a can prevent the battery cell 140 from being broken due to the impact of rigid pressure. The above description also applies to the second needle 162b and will not be elaborated further.

[0042] It should be noted that the first needle and the second needle in the same needle pressing group can both be movably connected to the pressing plate along the thickness direction D2, or any one can be movably connected to the pressing plate and the other can be fixedly connected to the pressing plate. The present application does not limit the number of the first needle and the second needle that are movably connected to the pressing plate along the thickness direction D2. When some of the first needles and some of the second needles are movably connected to the pressing plate, the remaining first needles and second needles can be fixedly connected to the pressing plate. When the movably connected first needles and second needles apply pressure to the welding tape to make it fit with the battery cell, the springs sleeved on these first needles and second needles can provide buffering for the first needles and second needles fixedly connected to the pressing plate, avoiding breaking the battery cell.

[0043] Refer to Figure 5As shown, in some other embodiments, the cross-sectional area of the first pressing head 162a-1 of the first pressing pin 162a is larger than the cross-sectional area of the first main body portion 162a-2 of the first pressing pin 162a. Similarly, the cross-sectional area of the second pressing head 162b-2 of the second pressing pin 162b is larger than the cross-sectional area of the second main body portion 162b-2 of the second pressing pin 162b. The cross-sectional area of the first pressing head 162a-1 refers to the area of the cross-section of the first pressing head 162a-1 perpendicular to the thickness direction D2. The above description also applies to the first main body portion 162a-2, the second pressing head 162b-1, and the second main body portion 162b-2, and will not be elaborated here. The first pressing head and the second pressing head are used to apply pressure to the welding tape 150. Increasing the areas of the first pressing head and the second pressing head can prevent the welding tape and the battery cell from cracking due to excessive pressure.

[0044] Returning to Figure 4 As shown, the pressing device further includes a plurality of heating through-holes 163, which are arranged at intervals along the first direction D1, and the heating through-holes 163 penetrate through the pressing plate 161 along the thickness direction D2. The gap between the first pressing pin 162a and the second pressing pin 162b in each pressing pin group 162 corresponds to at least one heating through-hole 163. Specifically, referring to Figure 5 As shown, it can be seen that there is a gap 162c between the first pressing pin 162a and the second pressing pin 162b, and the gap 162c corresponds to a heating through-hole 163 in the thickness direction D2. Referring to Figure 5 As shown, the size of the gap 162c in the thickness direction D2 can be changed by adjusting the preset distance L2.

[0045] During welding, the first pressing pin 162a and the second pressing pin 162b are distributed on both sides of the solder joint 141 in the first direction D1, the heating through-hole 163 is located above the solder joint 141 in the thickness direction D2, and the projections of the heating through-hole 163 and the solder joint 141 in the thickness direction D2 overlap. Combining Figure 1 As shown, when the heating unit 120 heats the welding tape 150 and the battery cell 140, the thermal radiation released by the heating unit 120 can heat the solder joint 141 corresponding to the heating through-hole 163 through the heating through-hole 163 on the pressing plate 161. For the non-solder joint area on the battery cell, the pressing plate 161 between the non-solder joint area and the heating unit can prevent the thermal radiation released by the heating unit from directly irradiating the battery cell in the non-solder joint area. Thus, compared with the prior art in which the thermal radiation directly irradiates the battery cell in the non-solder joint area, the welding tape pressing device in the present application can effectively reduce the peak temperature of the battery cell, thereby reducing the temperature difference of the battery cell before and after welding, and further avoiding the warping of the battery cell due to the large temperature difference, and can also prevent the thermal radiation released by the heating unit from directly irradiating the photoresist, thereby preventing the insulating glue between the welding tape and the battery cell from failing due to high temperature.

[0046] Figure 6 yes Figure 3 The enlarged view of the circled part in the figure is shown in Figure 1. In order to more clearly understand the positional relationship between the pressure needle group, the heating through hole and the solder joint during welding, the following is combined with the Figure 5 and Figure 6 Further explanation is given as shown.

[0047] exist Figure 6 In the embodiment, the first pressing pin 162a and the second pressing pin 162b are distributed on both sides of the solder joint 141 along the first direction D1. Figure 6 In the embodiment, the cross-sections of the first pressing pin 162a and the second pressing pin 162b are circular and are tangent to the two sides of the welding point 141 respectively. Figure 5 As shown, in order to improve the efficiency of heat radiation welding the solder strip 150 and the solder joint 141 through the heating through hole 163, the first pressing needle 162a and / or the second pressing needle 162b should be avoided as much as possible from overlapping with the projection of the solder joint 141 in the thickness direction D2. It can be understood that the first pressing needle 162a and / or the second pressing needle 162b is allowed to partially overlap with the projection of the solder joint 141 in the thickness direction D2, but the first pressing needle 162a and the second pressing needle 162b should not completely cover the solder joint 141.

[0048] Continue to refer Figure 5 As shown, in some embodiments, the cross section of the heating through hole 163 perpendicular to the thickness direction D2 may be consistent with or different from the solder joint 141. The projections of the heating through hole 163 and the solder joint 141 in the thickness direction D2 partially overlap, so that the heat radiation released by the heating unit can effectively weld the solder strip and the solder joint. In other embodiments, the number of the heating through holes 163 corresponding to the gap 162c of the pressure needle group 162 in the thickness direction D2 is not limited to Figure 5 One of, for example, can also be any number such as two or three.

[0049] refer to Figure 7 FIG. 1 is a top view of a pressing plate according to an embodiment of the present application. In some embodiments, a plurality of light-transmitting windows 161c are provided on the pressing plate 161. Specifically, Figure 7 As shown, the light-transmitting window 161c extends along the first direction D1, and a plurality of light-transmitting windows 161c are spaced apart along the third direction D3. The light-transmitting windows 161c can allow heat radiation to heat a specific area on the battery cell, thereby improving the heating efficiency. It is understood that the number, shape, and area of the light-transmitting windows can be set according to requirements and are not limited to Figure 7 The embodiment shown in .

[0050] In the pressing device in the above embodiments of the present application, by providing heating through holes corresponding to the gaps between the pressing needle groups, the solder joint area can be selectively heated, thereby reducing the temperature difference of the battery cell before and after welding, further avoiding warping of the battery cell due to a large temperature difference, and avoiding the high-temperature failure of the insulating glue between the solder tape and the battery cell.

[0051] The present application also proposes a string welding machine to solve the above problems. Refer to Figure 1 As shown, the string welding machine 100 includes: a heating unit 120 and the pressing device 160 as described above. The pressing device 160 applies an external force to the solder tape 150 to make it fit with the solder joints on the battery cell 140. Under the action of the heating unit 120, the solder tape 150 and the battery cell 140 are welded together.

[0052] In one embodiment, the string welding machine 100 further includes a shielding plate 170. Refer to Figure 1 As shown, the light shielding plate 170 is disposed between the heating unit 120 and the pressing device 160. In Figure 1 , the light shielding plate 170 corresponds to the gap between two adjacent battery cells 140 in the thickness direction D2, so as to avoid the high-temperature failure of the insulating glue coated on the solder tape between the battery cells. For other details of the string welding machine, reference can be made to the relevant descriptions above, and will not be elaborated here.

[0053] In the string welding machine in the above embodiments of the present application, by providing heating through holes corresponding to the gaps between the pressing needle groups, the solder joint area can be selectively heated, which is beneficial to avoiding warping of the battery cell due to heat and avoiding the failure of the insulating glue.

[0054] The present application also proposes a welding method for the solder tape and the battery cell to solve the above problems. Refer to Figure 2 As shown, this welding method uses the string welding machine as described above to weld the solder joints of the solder tape 150 and the battery cell 140. During welding, the projection of the heating through hole 163 and the corresponding solder joint in the thickness direction D2 overlaps. Among them, the heating unit 120 heats the solder joint corresponding to the heating through hole 163 through the heating through hole 163.

[0055] Refer to Figure 5 As shown, in one embodiment, before welding, an intermediate layer 180 is coated on the solder joint 141. The intermediate layer 180 includes one or more of conductive solder paste, conductive tape, or conductive glue. The intermediate layer helps to weld the solder tape and the solder joint 141.

[0056] In the welding method in the above embodiments of the present application, during welding, making the projection of the heating through hole and the corresponding solder joint overlap in the thickness direction is beneficial to avoiding warping of the battery cell due to a large temperature difference and avoiding the high-temperature failure of the insulating glue between the solder tape and the battery cell.

[0057] The basic concepts have been described above. Obviously, for those skilled in the art, the above application disclosure is only for illustration and does not constitute a limitation to this application. Although not explicitly stated here, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are proposed in this application, so such modifications, improvements, and corrections still fall within the spirit and scope of the exemplary embodiments of this application.

[0058] Meanwhile, this application uses specific terms to describe the embodiments of this application. Such as "one embodiment", "an embodiment", and / or "some embodiments" mean a certain feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that the "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more at different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application can be appropriately combined.

[0059] In some embodiments, numbers are used to describe the components and the quantity of attributes. It should be understood that such numbers used for the description of embodiments are, in some examples, modified by the modifiers "about", "approximately", or "substantially". Unless otherwise stated, "about", "approximately", or "substantially" indicate that the said numbers allow a variation of ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, and such approximate values may change according to the characteristics required by individual embodiments. In some embodiments, the numerical parameters should consider the specified significant digits and adopt the method of retaining the general number of digits. Although the numerical ranges and parameters used to confirm the breadth of the scope in some embodiments of this application are approximate values, in specific embodiments, such numerical settings are made as precise as possible within the feasible range.

Claims

1. A solder strip pressing device, characterized in that, Comprising: A pressing plate; A plurality of press needle groups, which are arranged on the pressing plate at intervals in the first direction and the third direction. Each press needle group has a first press needle and a second press needle. The first press needle and the second press needle are spaced apart by a preset distance in the first direction. The ends of the first press needle and the second press needle away from the pressing plate both have a pressing head; and A plurality of heating through-holes penetrate the pressing plate in the thickness direction of the pressing plate. The plurality of heating through-holes are distributed at intervals in the first direction and the third direction. The gap between the first press needle and the second press needle in each press needle group corresponds to at least one of the heating through-holes. Wherein, two adjacent heating through-holes in the third direction are separated by the pressing plate located therebetween. Heat radiation heats the solder joints corresponding to the heating through-holes through the heating through-holes located on the pressing plate, and the pressing plate prevents the heat radiation from directly irradiating the non-solder joint area.

2. The pressing device according to claim 1, wherein Part of the first press needles are movably connected to the pressing plate along the axial direction of the first press needles, and part of the second press needles are movably connected to the pressing plate along the axial direction of the second press needles.

3. The pressing device according to claim 2, characterized in that, The pressing plate has a plurality of press needle holes. One end of the part of the first press needles away from their pressing heads is arranged in the corresponding press needle holes along their axial directions, and one end of the part of the second press needles away from their pressing heads is arranged in the corresponding press needle holes.

4. The pressing device according to claim 3, characterized in that, It further includes a plurality of springs. The springs are sleeved on the part of the first press needles, and the springs are sleeved on the part of the second press needles. Wherein, one end of each spring abuts against the pressing plate, and the other end abuts against the pressing heads of the corresponding first press needles and second press needles.

5. The pressing device according to claim 1, characterized in that, The cross-sectional area of the pressing head of the first press needle is larger than the cross-sectional area of the main body part of the first press needle, and the cross-sectional area of the pressing head of the second press needle is larger than the cross-sectional area of the main body part of the second press needle.

6. The pressing device according to claim 1, wherein A plurality of light-transmitting windows are formed on the pressing plate.

7. A string welding machine, characterized in that, Comprising: A heating unit; And The pressing device according to any one of claims 1 to 6, and the pressing device is located below the heating unit.

8. The string welding machine according to claim 7, wherein, It further includes a light-shielding plate, and the light-shielding plate is arranged between the heating unit and the pressing device.

9. A welding method for a welding tape and a battery cell, characterized in that, Using the string welding machine according to claim 7 or 8 to weld the solder tape to the solder joints of the battery cells. During welding, the projection of the heating through-hole and the corresponding solder joint in the thickness direction overlaps, and the heating unit heats the solder joint corresponding to the heating through-hole through the heating through-hole.

10. The welding method according to claim 9, characterized in that, It further includes coating an intermediate substance on the solder joints before welding.

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