Apparatus and method for wave soldering

Abstract

The invention relates to a device (10) for wave soldering, comprising a soldering nozzle (12) for generating a solder wave and a soldering mask (22) with through-openings (38) in the area of soldered connections to be formed, said soldering mask (22) being fixedly accommodated within a receiving opening (20) of the soldering nozzle (12).

Description

[0001] Description

[0002] title

[0003] Apparatus and method for wave soldering

[0004] Technical field

[0005] The invention relates to a wave soldering device, characterized in that it can be used to solder connection pins to a printed circuit board, particularly when the pins are very close together in the area of ​​the solder joints on the circuit board, without forming solder bridges between them. The invention further relates to a wave soldering method using a device designed according to the invention.

[0006] State of the art

[0007] From DE 195 41 340 A1, it is known to generate a single solder wave using a soldering nozzle. Areas of a printed circuit board to be soldered can be transported by means of conveyor devices into the area of ​​the solder wave and lowered there so far in the direction of the solder wave and then raised again so that the solder of the solder wave forms the solder joints on the printed circuit board.

[0008] To solder only specific areas of printed circuit boards or to protect already soldered components from solder waves, it is also known to use so-called solder masks, which, for example, have recesses to protect already soldered components and / or through-holes in the area where the solder wave solders the components to the printed circuit board (DE 10 2010 002 150 A1, US 4,739,919). Typically, the solder mask is mounted together with the printed circuit board, or the two elements form a single assembly. Disclosure of the invention

[0009] The wave soldering device according to the invention, with the features of claim 1, has the advantage that it enables the use of one and the same solder mask for forming solder joints on a plurality of assemblies to be soldered. The invention is based on the idea of, on the one hand, forming the solder mask together with the soldering nozzle as a single unit, and on the other hand, transforming or dividing the single solder wave rising in the soldering nozzle and filling the cross-section of the soldering nozzle into a plurality of partial solder waves through the openings of the solder mask, wherein the arrangement of the partial solder waves is adapted to the solder joints to be formed in the area of ​​the printed circuit board.

[0010] In light of the above explanations, a wave soldering device according to the invention, comprising the features of claim 1, therefore includes a soldering nozzle for generating a solder wave, and further a soldering mask in which openings for forming partial solder waves from the solder wave are formed, wherein the openings have distances to each other corresponding to the distances of solder joints to be produced, wherein the soldering mask is fixedly held within the soldering nozzle, and wherein the soldering mask is designed in such a way that solder does not adhere to the soldering mask.

[0011] Advantageous further developments of the device according to the invention for wave soldering are listed in the dependent claims.

[0012] To ensure a long service life for the solder mask, in particular to prevent the formation of oxides on the solder mask, and to prevent solder from adhering to the solder mask, the solder mask is made of stainless steel and has a roughness depth R on the surfaces that come into contact with the solder. z The surface roughness has a maximum of 0.8 mm. It has been found that, in practice, solder adhesion can be reliably prevented at such low roughness depths. Alternatively, another solder-repellent material can be selected that withstands the solder temperatures without material or geometric changes to the solder mask. In a preferred embodiment of the solder mask's positioning within the soldering nozzle, the solder mask can be held in place by (at least) one magnetic element.

[0013] Particularly, but not exclusively, in connection with such a magnetic element, it is advantageous if the solder mask has a flat section with openings, which is bounded by an edge section arranged perpendicular to the flat section and limiting the flat section at its edges. The magnetic element can be brought into operative contact with the solder mask via this edge section, whereby the solder wave can act across the entire cross-section of the flat section into the area of ​​the openings (for the solder joints to be formed).

[0014] Another preferred design of the soldering nozzle provides that it has a block-shaped base body with vertically extending bores for supplying solder, which open into a projection arranged on the top side of the base body with a blind-shaped receiving opening for the solder mask.

[0015] The invention further relates to a wave soldering method using a device designed according to the invention as described above. The method is characterized in that the device is used to solder connecting pins to the printed circuit board (PCB), the connecting pins penetrating metallized through-holes of the PCB and projecting beyond the PCB on the device side. The through-holes in the solder mask have a diameter that is at most 30% larger than the diameter of the through-holes in the PCB. This latter feature, in particular, achieves a capillary effect that enables the solder to be drawn (independently) into or rise to the through-holes of the PCB.

[0016] In a preferred embodiment of the method described so far, the device is used to solder connection pins to a printed circuit board (PCB) that have a minimum spacing of 1.0 mm, and in particular less than 1.0 mm. Regarding the application of the solder to the solder joints, there are two basic methods, which can be used depending on the spacing between the connection pins and other parameters: In a first embodiment, the soldering nozzle is fixed in place, and the PCB is moved above the solder mask, with the connection pins dipping into the partial solder waves projecting above the solder mask.Such a method is particularly possible when there are relatively large distances between the connection pins, as this prevents a soldered connection pin from forming a solder bridge to an adjacent connection pin when there are several rows of connection pins, during its relative movement between the partial solder waves.

[0017] However, especially with connection pins that are relatively close together, it is advisable, in light of the above, that the soldering nozzle is fixed in place and that the connection pins of the circuit board are immersed in the through-holes in the solder mask in order to reliably avoid solder bridges between the connection pins.

[0018] In a further development of the last proposal, it is specifically intended that the connecting pins are immersed into the openings of the solder mask to a level at which the partial solder waves protruding above the solder mask on the side facing the circuit board come into contact with the circuit board in the area of ​​the through-holes.

[0019] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments of the invention and from the drawings.

[0020] Brief description of the drawings

[0021] Fig. 1 shows an exploded view of a soldering nozzle with an insert forming a solder mask in the soldering nozzle and a printed circuit board with connection pins to be soldered; Fig. 2 shows the arrangement according to Fig. 1 in a perspective, cutaway view.

[0022] Fig. 3 shows the arrangement according to Figs. 1 and 2 with connection pins immersed in openings of the solder mask in a cutaway, perspective view.

[0023] Fig. 4 shows the arrangement according to Figs. 1 and 2 in a sectional view during a soldering process with a detailed magnification and

[0024] Fig. 5 shows a side view of a solder mask with partial solder waves.

[0025] Embodiments of the invention

[0026] Identical elements or elements with the same function are provided with the same reference numbers in the figures.

[0027] Figures 1 and 2 show the essential components of a wave soldering device 10. The device 10 has a soldering nozzle 12 with a block-shaped base body 14. A projection 18 extends from a top surface 16 of the base body 14, with a receiving opening 20 for a solder mask 22. At least one, and in the illustrated embodiment several, riser bores 24 for solder L are provided within the base body 14. The solder L is injected under pressure into the at least one riser bore 24 on the side of the base body 14 facing away from the projection 18. The at least one riser bore 24 opens into the bottom region 26 of the projection 18 on the side facing the base body 14.

[0028] The extension 18 has, by way of example, two parallel side walls 28, 29 with semicircular wall sections 30 that connect the two side walls 28, 29. The side walls 28, 29 and the wall sections 30 define the receiving opening 20, which is formed in the form of a blind hole 32 in the extension 18. The blind hole 32, or receiving opening 20, serves to receive the solder mask 22, the upper surface of which is preferably flush with the upper surface of the extension 18. The solder mask 22 has a flat section 34, the shape of which is adapted to the cross-section of the receiving opening 20 in the extension 18, wherein the edge of the section 34 is bounded on the side facing the receiving opening 20 by a circumferential side wall 36. The dimensions of the solder mask 22 are such that it is preferably received without a gap within the receiving opening 20.

[0029] Furthermore, the flat section 34 exhibits a multitude of

[0030] Through-holes 38 are provided, each of which is round and has a diameter D (Fig. 2, 3). The hole pattern or the dimensions of the through-holes 38 are adapted to the arrangement of solder joints to be formed in the area of ​​a printed circuit board 1, as will be explained in more detail below.

[0031] The solder mask 22 is made of stainless steel and is designed such that solder L does not adhere to its surface. For this purpose, the solder mask 22 is provided with a roughness depth R on the surfaces that come into contact with the solder L. z exhibits a maximum of 0.8.

[0032] To mount the solder mask 22 in the extension 18, the solder mask 22 can be inserted into the receiving opening 20. Furthermore, a magnetic element 40 is provided, as shown in Fig. 4, to position and fix the solder mask 22 within the extension 18. This magnetic element interacts with the ferromagnetic material of the solder mask 22 and, in particular, prevents vertical movement of the solder mask 22 in the receiving opening 20.

[0033] Using the device 10 described so far, solder joints can be created in the area of ​​the circuit board 1, which serve to metallize

[0034] Connecting pins 4, which penetrate through the through-holes 3 in the printed circuit board 1, are connected to the through-holes 3 (see detail in Fig. 4). The connecting pins 4 penetrate the printed circuit board 1 completely and protrude beyond the printed circuit board 1 on the side facing the solder mask 22. The diameter d of the through-holes 3 in the printed circuit board 1 is preferably adapted to the diameter D of the through-holes 38 in the solder mask 22 such that the diameter D of the through-holes 38 is a maximum of 30% larger than the diameter d of the through-holes 3 in the printed circuit board 1. This creates a capillary effect when the solder L comes into contact with the through-holes 3 and 38, causing the solder L to rise into the through-holes 3 of the printed circuit board 1.

[0035] Figure 4 shows the device 10 together with the circuit board 1 and the connection pins 4 during the soldering process. It can be seen in particular that the connection pins 4 and the circuit board 1 are lowered towards the extension 18 to such an extent that the connection pins 4 penetrate the through-holes 38 of the solder mask 22. The solder L also penetrates the through-holes 38 and forms partial solder waves TW on the side facing the circuit board 1. This means that the single solder wave present in the area of ​​the solder mask 22 below section 34 is split or subdivided into a plurality of partial solder waves TW, each of which serves to form a solder joint between a connection pin 4 and the circuit board 1.The underside of the circuit board 1 facing the solder mask 22 is preferably arranged in direct contact with the section 34 of the solder mask 22, or has only a small distance a to the top of the solder mask 22, so that the partial solder waves TW reach the area of ​​the through-holes 3 of the circuit board 1 and the solder L rises into the through-holes 3 by capillary action.

[0036] In Fig. 4, arrows 42 show how the solder L reaches the area of ​​the extension 18 through the riser holes 24 and also comes into contact with the connection pins 4 or the through-holes 3 of the printed circuit board 1. Crucially, the solder mask 22, as shown in Fig. 5, forms partial solder waves TW on the upper side facing away from the extension 18, which project beyond the upper side of the solder mask 22 in the area of ​​section 34 in a spherical segment shape.

[0037] Furthermore, Fig. 5 also illustrates the case where the solder joints can be formed by moving the circuit board 1 with the connection pins 4 above the solder mask 22 in the horizontal direction of arrow 44. The essential point here is simply that the geometry of the connection pins 4 or the solder board 1 allows the connection pins 4 or the through-holes 3 to be wetted with solder L when the connection pins 4 are brought into contact with the partial solder waves TW. The device 10 described so far can be modified or adapted in various ways without deviating from the inventive concept. In particular, it is also mentioned that such a device 10 can be used not only to solder connection pins 4 to a circuit board 1, but also, in principle, to solder joints that are very closely spaced from one another, whereby the arrangement or...The hole pattern of the through-holes 38 on the solder mask 22 must be adapted according to the arrangement of the solder joints.

Claims

Claims 1. Device (10) for wave soldering, comprising a soldering nozzle (12) for generating a solder wave, comprising a solder mask (22) for forming partial solder waves (TW) from the solder wave, wherein the solder mask (22) has through-openings (38) in the area of ​​solder joints to be formed by means of the partial solder waves (TW), wherein the solder mask (22) is fixedly received within a receiving opening (20) of the soldering nozzle (12), and wherein the solder mask (22) is designed such that solder (L) does not adhere to the solder mask (22).

2. Device according to claim 1, characterized in that the solder mask (22) is made of stainless steel and has a roughness depth R on the surfaces that come into contact with the solder (L). z has a maximum of 0.

8.

3. Device according to claim 1 or 2, characterized in that the solder mask (22) is held in the receiving opening (20) of the solder nozzle (12) by a magnetic element (40).

4. Device according to one of claims 1 to 3, characterized in that the solder mask (22) has a flat section (34) with the through-openings (38) which is surrounded by a side wall (36) which is preferably arranged perpendicular to the flat section (34) and which limits the flat section (34).

5. Device according to one of claims 1 to 4, characterized in that the soldering nozzle (12) has a block-shaped base body (14) with at least one rising bore (24) for supplying the solder (L), which is located in a a projection (18) arranged on the upper side (16) of the base body (14), in which the blind-hole-like receiving opening (20) for the solder mask (22) is formed.

6. A method for wave soldering using a device (10) configured according to any one of claims 1 to 5, wherein the device (10) is used to solder metallized through-holes (3) in a printed circuit board (1) to the printed circuit board (1) with connecting pins (4) penetrating the through-holes (3) and projecting beyond the printed circuit board (1) on the side of the solder mask (22), and wherein the through-holes (38) in the solder mask (22) have a diameter (D) that is at most 30% larger than the diameter (d) of the through-holes (3) in the printed circuit board (1).

7. Method according to claim 6, characterized in that the device (10) is used to solder connection pins (4) to the circuit board (1) which have a minimum distance of <= 1.0 mm.

8. Method according to claim 6 or 7, characterized in that the soldering nozzle (12) is arranged in a fixed position, and that the printed circuit board (1) is moved horizontally above the solder mask (22), wherein the connecting pins (4) dip into partial solder waves (TW) projecting beyond the solder mask (22).

9. Method according to claim 6 or 7, characterized in that the soldering nozzle (12) is arranged in a fixed position, and that the connecting pins (4) of the circuit board (1) are immersed in the through-holes (38) of the solder mask (22) in a vertical direction.

10. Method according to claim 9, characterized in that, that the printed circuit board (1) is lowered to the level of the solder mask (22) or at a small distance, so that partial solder waves (TW) protruding above the solder mask (22) enter the through holes (3) of the printed circuit board (1).

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