DE2315228A1 - METHOD AND DEVICE FOR APPLYING SOLDER TO A SELECTED PART OF A WORKPIECE - Google Patents

Description

Method and apparatus for applying solder to a selected part of a workpiece

The invention relates to a method and an apparatus for applying solder to a selected part of a workpiece.

It is known to apply solder to a selected part of a workpiece to be applied, for example to an electrical connection terminal made of a material that can be wetted with solder, namely by means of a method in which the part of the connection element to which no solder is to be applied, Covered with a high temperature and solder resistant material that creates a structural barrier to the selected Part to which the solder is to be applied forms adjacent atmosphere.

A method of applying solder to a selected part of a workpiece, that selected part being a having dry flux coating, is characterized according to the invention, .that the workpiece in a channel

4U9 & 41/0470

. Bayerische Vereinsbank Munich 823101
Postsdieck 54782

AMP 3156 - 2 -

of non-wettable solder-resistant material, for example Chromium or polytetrafluoroethylene, is arranged that the channel has such a width and the clearance between the Channel and the workpiece is such that the molten solder does not enter the channel that the selected part is outside of the channel and the remainder of the workpiece located immediately adjacent the selected part within the channel and that molten solder is supplied to the selected part of the workpiece o

A device for carrying out the method according to the invention is characterized by a channel made of a non-wettable solder-resistant material, for example chrome or polytetrafluoroethylene, for receiving the workpiece such that the selected part thereof is outside the Channel is located, while the remaining part of the workpiece immediately adjacent to the selected part is within of the channel, and by a device for supplying molten solder to the selected part, the Channel has such a width and the clearance between the workpiece and the channel is such that molten Solder does not enter the channel so the solder is only applied to the selected part.

Embodiments of the invention are described in more detail below with reference to the figures. In the figures demonstrate:

Figure 1 is a schematic perspective illustration an apparatus for applying solder by wave soldering to a selected part of a Workpiece in the form of an electrical connection pin, that forms part of a terminal strip?

Figure 2 is an enlarged sectional view along the line IX-II from Figure 1}

FIG. 3 shows an enlarged sectional view along the line III-III from FIG

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FIG. 4 shows a partially sectioned plan view along the line IV-IV of FIG. 1;

Figure 5 is a side plan view of a pin, wherein a selected part according to the invention is covered with "solder?

FIG. 6 is a plan view of the pin of FIG Figure 5?

Figure 7 is a plan view of another pin, again with a selected portion is provided with solder according to the invention?

FIG. 8 shows a section along the line VIII-VIII from FIG.

FIG. 9 shows a section along the line IX-IX from FIG. 5J

FIG. 10 shows an enlarged part of a section along the line X-X of FIG. 7, where the ordinate the width of the plumb line in η and the abscissa the length of the plumb line in inches

FIG. 11 shows, in section, an enlarged detail of part of the connection pin shown in FIGS. 5 and 6, this being inserted into a metallized opening in a plate}

FIG. 12 shows, in section, an enlarged detail of the connection element shown in FIG. 11, wherein the solder was melted again and the clearance between the metallized opening and the connecting element used and forms the contact surfaces surrounding the connecting element?

FIG. 13 shows a perspective illustration of part of the device from FIG a mechanism for flattening a solder tape applied to a selected part of an electrical Connection element is applied, provided is j

FIG. 14 shows an enlarged section through the flattening mechanism 5

Figure 15 is a diagrammatic representation of a photomicrograph of a pair of electrical connector pins with flattened solder strips in approx. 15x magnification:

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FIG. 16 shows a graphic representation of a microphotograph of a cross section by an electrical connection pin with a flattened solder tape, enlarged approximately 100 times; and

Figure 17 is an enlarged cross-section of a part

an electrical connector pin with a flattened solder tape, the pin in a metallized opening of a plate is arranged.

A device 1 for applying solder to a selected part of a workpiece in the form of an electrical connection element 2, which forms part of a strip 4 of connecting elements, has a supply roll 6 for the Strip 4 and means, not shown, for successively advancing the strip 4 through a flux application station 6, a flux drying station 10 and a bath l6. The connection elements 2 are next to each other at a distance arranged from each other along the strip 4, which in the longitudinal direction is first fed to the flux application station 8 in the form of a flux bath. The connection elements 2 are successively coated with a layer of flux. The entire surface of each connection element 2 is with Flux covered; in a modified embodiment, the flux can also only be applied to selected parts of the element, the solder material to receive, are applied.

The strip 4 is then passed through the flux drying station 10 conveyed in which the flux is solidified by the application of heat. Finally, the strip 4 by a solder wave 20 formed in the bath 16 and then conveyed to a take-up roll (not shown).

The bath l6 has an open top, and from this On the side, a fastening device 12 is received in the bath l6. The fastening device 12 extends to

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down from a pair of spaced apart rails 14 which extend over the top of the bath 16. The fastening device 12 is located above Means for forming a solder wave, which are provided in the bath 16 in the form of a damming device 18, the fastening device 12 partially immersed in the shaft 20 of molten solder formed by the damming device 18 is.

According to FIGS. 2, 3 and 4, the fastening device 12 has one fastened to each rail 14 by means of screws 26 Suspension plate 24 on as well as a pair of channels that extend downward from the suspension plate 24.

Each channel consists of an upper plate 28, 28 'which is spaced from a lower plate 36, 36' by an intermediate layer 42, 42 '. The plates and the intermediate layer of each channel are braced together and extend downward from the plate 24 by means of bolts JO and nuts 46. Opposite flat surfaces 32, 38 or 32 *, 38 ^{1 of} the upper and lower plates and an edge 52, 52 * of each intermediate layer 42, 42 'form a pair of passages 51 »51 *» through which the connecting pins 2 move freely can if they are conveyed through the container l6.

Each lower plate 36, 36 * has a rounded surface 50, 50 · formed. A further stowage device 49 is between opposing end surfaces 48, 48 of the top plates 28, 28 and opposing surfaces 50, 50 of the lower plates 36, 36 'are defined.

The plates 28, 28 'and 36, 36' consist of non-wettable solder-resistant material, for example chromium or polytetrafluoroethylene. The intermediate layers 42, 42 * exist also made of non-wettable solder-resistant material.

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Slots 54, 54 * in the intermediate layers 42, 42 * ensure an adjustment of the narrowing area of the passages 511 51 * defined by the edges 52, 52 and for an adjustment to define selected parts of each pin 2 above the further storage device 49

Similarly, the plate 24 is provided with elongated slots 56, each of which receives the shank of a respective screw bolt 30. The slots allow adjustment of the plates 28 and 36 with respect to the corresponding plates 28 * and 36 ¹ , by sliding, with respect to the respective plates 28 * and 36 1, so that the width of the second damming device 49 can be changed.

In operation, the fastening device 12 is partially immersed in the solder wave 20, with the plates 36 and 36 * Damp the solder wave and lift a part 57 of it up into the second damming device 49. That is, the rounded ones Areas 50 and 50 channel a sufficient amount Mass of molten solder, so that the raised shaft portion 57 is formed, the width of which is equal to the width of the between the storage device 49 formed by the plates is limited. Consequently the solder wave 20 is hindered by the presence of the fastening device 12 so that a begiaizter Raised shaft portion 57 is formed which extends to a central portion of each terminal conveyed through the channels 2 hits and covers it. Between the opposite surfaces 32, 38 and 32 *, 38 * and the corresponding Opposite surfaces of the connecting elements 2 are clearances provided that a passage of the Allow connecting elements 2 through the passages 51 »51 ', however, prevent molten solder from spreading over the surfaces of the connecting elements, this solder only adheres to the selected parts of the connection elements which pass through the second damming device 49. Consequently forms the presence of the non-wettable solder-resistant

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Material adjacent to the solder-wettable surfaces of each flux-covered terminal pin 2, however this does not touch, a solder flow barrier without a positive structural barrier in the form of a barrier layer applied directly to the pin surfaces or cover is necessary.

The solder is partially prevented from flowing into the passages 51 »51 * between adjacent connecting pins 2 by the fact that the solder flow takes place in a direction running in the longitudinal direction to the second damming device 49 and not transversely thereto; however mainly in that the channels are made of non-wettable solder-resistant material and the width of the passage in each channel is small, thereby creating an anti-capillary action relative to the molten solder. Molten solder is a high-density liquid with high surface tension compared to a liquid such as water. As a result, molten solder tends not to splash, but rather to clump up. The molten solder shows no tendency to enter the passages by splashing, capillary action, or flowing along wettable surfaces. Molten solder that does splash into a passage does not flow far because of its inherent inertia and is quickly absorbed back into the larger solder mass as a result of surface tension and agglomeration forces, which are reinforced by the repellent properties of the non-wettable solder-resistant material of the channels. The solder tends to enter between the plates 28, 36 and 28 ¹ , 36 and then immediately flow out again.

After the selective soldering step, the strip can be fed to a further station at which the superfluous Flux is removed from each connector.

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FIG. 7 shows an enlarged plan view of an electrical connection pin 2. Each from the fastening device protruding pin 2 is solidified with a Band 58 of solder material provided, the width of this Tape by the presence of the channels of the fastening device 12 forming non-wettable solder-resistant material is precisely regulated. Figure 8 shows that each of the flat surfaces of the electrical connection pin 2 their own Has solder layer · Correspondingly, layers 60 and 64 of generally convex cross-section are located on opposite one another flat surfaces of the connecting step 2, and additional layers 62 and 66 of generally convex-domed Cross-section are on the other opposite sides of the pin. Together form the layers 60, 62, 64 and 66 a generally elliptical solder tape which encloses the pin 2.

In the example shown in Figure 10, the layer 60 has a maximum width _t of about 5000 Ax and the layer 64 has a maximum thickness p of about 3,500 .. The end portions 6O ¹ of the layer 60, which determine the bandwidth of the layer form in Relative to the surface 2 * of the pin 2, a relatively shallow acute angle and not an oblique angle. This angle is known as the dihedral angle which indicates the degree of wetting between the solder and the wettable material of the terminal pin. Since the solder is applied in a molten state, the surface tension should create a relatively smooth front bow in each of layers 60 and 64. When viewed, however, these surfaces appear irregular in terms of their curvature. This can be explained in part by the changes in the surface of the layers 60 and 64 as the pins are advanced through the fastening device 12. When the connector pins out of the raised. Section 57 of the solder wave on taucfaeiaj becomes a. Expiry esa from

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Excess solder causes it to break the surface of the the terminal pins of applied molten solder changed will. In addition, the solidification of the applied solder takes place at unequal speed, which leads to further Irregularities are caused in the solder layers.

In the embodiment described above, although the electrical connection pins 2 are in the form of a strip by the fastening device 12} however, a single electrical connection element can be inserted into the passages 51, 51 * introduced the fastening device and the fastening device 12 can be dipped into the solder bath l6 by hand.

Example I.

Gold-plated electrical connector pins that are made of metal with a thickness of 0.558 mm were punched and formed, were on a carrier strip at a distance of 3 | 175 nm from each other intended. The connector pins were from a supply roll at a speed of about 90 cm / sec through a flux bath conveyed from molten rosin. The connection pins were completely coated with the flux, and this was then dried. The connecting pins coated with flux were then replaced by those made of polytetrafluoroethylene manufactured fastening device 12 conveyed. The intermediate layers 42 and 42 'had a thickness of 0.7 ^ 2 mm, so that the connecting pins, whose thickness is 0.558 mm move well through the fastener could. The fixture was partially immersed in a wave solder wave soldering machine. 6O-4O solder a temperature of 249 C was selectively applied to form solder ribbons of regulated widths on the terminal pins. The connector pins were moved on to a solvent bath where all traces were still present Flux removed. The soldering tapes

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send connector pins were then wound onto a supply roll.

Example II

Gold-plated connection pins 0.558 mm thick, which were arranged on a carrier strip at intervals of 3> 175 mm, were dipped by hand in a flux bath made of rosin and then dried so that the connection pins were provided with a flux coating. Then a plurality of flux-coated terminal pins were placed in the fixture, and these were then hand dipped in a molten solder tape of 60-4O solder at a temperature of 24 ° C. The subsequent investigation showed that the desired solder layers in the form of individual strips had been applied in a sufficient manner by the immersion process. The duration of the immersion process depends on the results required.

Experiments show that the thickness of the solder tape on the selected part of a connection pin reverses with time varies during which the pin is exposed to the heat of the Solder bath is exposed. Accordingly, there is a long dwell time of a terminal pin in the solder bath a corresponding thinner solder tape

Normally, the close spacing between the faces 32 _s 38 and 32 *, 38 ¹ would be that a small width that the passages 51 '5I ¹ "generate a capillary effect, whereby a complete spreading of the molten solder would be caused by a wettable surface, but it It is believed that in the fastener 12, the presence of the non-wettable solder resistant material repels the solder

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and its tendency to agglomerate and form bulges under the action of its surface tension is increased. Accordingly, the forces resulting from the surface tension and repulsive nature of the non-wettable material overcome both the capillary action and the spreading action of the flux present on the solder wettable surface of each pin. The spread of the solder is also limited by the presence of trapped gases between the intermediate layers kZ and 42 *. However, the presence of such gas inclusions is difficult to regulate and therefore cannot be used to precisely and effectively prevent the spread of solder.

If electrical connection pins or other workpieces in Strip shape are conveyed through the fastening device, care must be taken to ensure that the distance between adjacent pins is not so tight that one Creates capillary action between the pins and thereby the effectiveness of the non-wettable solder-resistant material in terms of limiting the spread of solder.

In FIGS. 5 and 6, a further connection element 68 is illustrated which is made in one piece with a strip 70. A plurality of similar connection elements arranged side by side can be connected to the strip 70 and provided with solder strips 72 which have been applied to the surfaces of the connection elements in the manner described above. As shown in Figure 9, the connector 68 is square in cross-section and the flat surfaces of the connector are provided with convex solder layers 74, 76, 78 and 80 adhered to them. As Figure 5 shows, the solder strip 72 curved elongated edges 82 that ^ n the surface of the connecting element 68 formed si I, '.ie first impinge upon the solder wave when

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the strip is conveyed through this. The margins 82 have been found to occur because of the promoted Connection el ement masses of molten solder in the passages 51, 51 'displaced laterally. On all of the others However, the surface of the connection element is the soldering tape to a predetermined bandwidth in the described Way limited. As the figure shows, the connecting element 68 has a hook-shaped end section 84. As a result, the fastening device must have a passage have, which corresponds to the hook-shaped end portion of the connecting element, so that the same is through the Can move passage and contacting the end portion 84 with solder is avoided.

As shown in Figures 11 and 12, the connector pin is inserted into an opening 86 of a plate 88. Both the plate and the opening 86 are coated with a metal layer 90 covered. The solder tape 72 is in the metallized opening 86 arranged.

Figure 12 illustrates how the solder tape 72 by means of a suitable method is brought to melt again and the clearance between the metallized opening 86 and the inserted pin 68 completely fills. In addition, a sufficient amount of solder is provided so that the Remelt abutment surfaces 92 and 94 at each open End of the metallized opening 86 are formed, which adhere the pin 68 enclosing this. Since according to The method described in Figure 1 has removed all flux residues from the terminal pin, the solder does not run off the connector pin. In addition, there is a capillary effect due to the space between the Opening and the inserted connector pin, so that a good Solder flow and the formation of the contact surfaces guaranteed are.

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As FIG. 13 shows, the device 1 according to FIG. 1 is modified by providing an additional mechanism 100. The connecting pins are now not wound directly onto a supply reel, but the connecting pins 2 on the strip k pass through the mechanism 100 arranged between the containers 16 and the winding roller (not shown) or be arranged between the container 16 and the mechanism 100.

The mechanism 100 includes an electric motor 110 that rotates a cam 112 to reciprocate a sub Spring-loaded stamp 114, which is in a cylindrical bearing arranged in the upper part of a housing Il8 Il6 is slidably mounted. The stamp 114 has a Wave 120 (Figure 14). At the lower end of the shaft 120, a plate 122 is attached, which with the punch 114 on a cleat 126 is movable to and from this.

According to FIGS. 7, 8 and 10, the solder tape 58 originally formed on each of the connection pins 2 is of a generally oval configuration in cross section. In addition, the thickness of the solder tape varies considerably along the length of each pin 2. For example, as shown in FIG. 10, the thickness of layer 60 varies from 0 to about 5000/1 . The thickness of the solder tape 58 also varies slightly with the various individual connection pins 2 which are conveyed through the container 16. This difference in the thickness of the solder tape 58 can result in difficulties in inserting the pins 2 through metal-coated openings in plates made of substrate material. Usually the diameters of the openings are relatively constant and are somewhat smaller than the overall diameter of the soldering tape 58, so that a firm metal-to-metal contact between the soldering tape and the metal coating of the opening is possible; thereby liable

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when remelting the solder bath 58, the solder on the metal layer in the opening. A tight fit is desirable, but this is only necessary temporarily and
therefore need not be so tight that it serves as a means of permanently connecting the terminal pin to the opening. It has been found to be desirable to have a fit that holds the individual terminal pins positively in their positions, but does not require too large a holding craft, as would be required for permanent attachment of the pins in the metallized openings. This type of fit is created by the mechanism 100 by which the solder tape 58 is flattened.

Figure 14 shows the solder tape 124 during the flattening process. In the flattening process, the hardened solder tape does not behave like a completely elastic or deformable substance. On the contrary, it is a tin-lead alloy that is not cold- hardenable txn.d which is a partially deformable and partially non-deformable substance
behaves. That is, the solder tape 124 is partly elastically deformed and partly elastically deformed during the flattening step
crushed and broken. As a result, on opposite sides of the flattened solder tape 124 upper and lower
lower planar surfaces 128 and 130 are formed while a portion of the dislodged solder is formed into upper and lower flanges 132 and 134, respectively, which have a large number of hairline cracks.

Figure 15 illustrates the bulged shape of the flanges 132, 134 on a pair of terminal pins 2. The extent of this bulging is, of course, related
with the thickness of the solder tape on the flattening parts.

The structural effects of the flattening process are shown in Figure 16 shown. The solder distribution is not absolutely symmetrical

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metric, although the lack of symmetry is not critical to the invention; however it is too note that it is generally necessary to have at least some of the solder on all four sides of the pin 2 is liable. The solder layers I36, 138 attached to the upper or lower flat surface of the connector pin 2 are equivalent to the flattened solder layers 60 and 64 of FIG. Similarly, the ones are convex Solder layers 140 and 142 adhered to the right and left flat surfaces of the terminal pin 2, the solder layers 62 or 66 according to FIG. 8 essentially equivalent. The flattening process forms flattened surfaces 128 and 130 on solder layers I36 and I38. The flattening step also remits in the formation of a break line 144 at the junction between the upper and lower Solder layer 136 and I38 and the right and left solder layers l40 and l42. At the lower left corner of the connector pin 2, no break line is formed because the solder distribution is not symmetrical, but at the area of the lower left corner was relatively thin. However, this factor has no influence on the operation of the invention as long as it is sufficient Amount of solder on each connector pin adheres to break lines at three corners of each soldered lead pin. Each break line 144 defines one Place where one of the flanges 132 or 134 over the Solder layers 140 and 142 adhering to the side portions of the terminal pin 2 hang. It has been found that this overhanging sections are traversed by hairline cracks 146 over their entire length. Some of these hairline cracks are in Figure 16 cannot be seen. Further hairline cracks 146 are formed in circumferential sections of the solder tape where the effect the flattening process is most noticeable. The hairline cracks have a strong weakening of the structural strength and rigidity of the solder tape result, so that Circumferential sections of the solder tape are more easily sheared off

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can, while each of the solder taped pins 2 is pressed into a suitable opening. Also, the flattened surfaces 128 and 130 are the solder tapes deformed so far that they are not on the inner surfaces of the openings into which the connecting pins are inserted, attack. Thus, there is contact between the solder taped connector pins and the openings into which they are are inserted on the right and left solder layers l40, 142 and the protruding flanges 132, 134 restricted. This limited contact significantly reduces the frictional resistance when inserting the connector pin, which would otherwise be present if the solder tapes were in contact with a larger surface area on the periphery of the openings would arrive. So a plurality of connections can pin can be used simultaneously without excessive frictional resistance to the introduction. As already mentioned, the flanges 132 and 134 are hairline cracks criss-crossed and therefore tend to be with the introduction of Terminal pins provided with solder tape can be sheared off relatively easily into suitable openings.

FIG. 17 illustrates the insertion of a terminal post with a flattened solder ribbon 124 into an opening 86 in FIG a plate 88. The plate and the opening are coated with a metal layer 90. The flattened solder tape 124 has a width that is greater than the diameter of the metal-coated opening 86. The portion of the flattened Solder tape 124 extending beyond the diameter of opening 86 has low structural strength, and when the pin is pushed into the opening, the protruding flanges are flattened from the main body of the Solder tape easily separated or sheared off. Sections of the sheared solder tape can be partially with the Solder tape remain in contact and form solder tabs 148 that extend outwardly across the outer surface of plate 88. It is not necessary to remove these solder noses 148 separately, since when the solder is melted again, the previously

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xuxd, relating to the opening 86, draws all of the molten solder, including the tabs 148, into the opening.

Patent claims

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Claims (6)

AMP 3156 - £ - ■ ... patent claims 1. "A method for applying solder to a selected part of a workpiece, this selected part having a dry flux coating, characterized in that the workpiece (2) in a channel (28, 28 ¹ J 36, 36 *) made of non-wettable solder-resistant Material, for example chromium or polytetrafluoroethylene, is arranged so that the channel (28, 28 »} 36, 36 ·) has such a width and the clearance between the workpiece and the channel is such that the molten solder (20) does not enter the Channel occurs that the selected part outside the channel (28, 28 * 5 36, 36 ¹ ) and the remainder of the workpiece (2) is arranged immediately adjacent to the selected part within the channel and that the selected part of the workpiece is molten solder (20 ) is supplied. 2. The method according to claim 1, wherein the workpiece is a connecting element which forms part of a strip of connecting elements, characterized in that adjacent connecting elements (2) are arranged at a distance from one another which is sufficient to form a capillary action between the To avoid connecting elements (2), and that a channel section (38, 38 ¹ ) is positioned in a known per se, formed in a bath (16) of molten solder wave (20) that the selected part of the workpiece the molten solder is exposed to form a band of solder around the selected part. 3. The method according to claim 2, characterized in that that subsequent to the formation of the solder tape around the selected part around opposite Sides (128, I30) of the solder tape (124) deformed by pressure will. 4 09841/0470 AMP 3156 '- d - 4. Apparatus for carrying out the method according to claim 1, characterized 'by a channel (28, 28 * 5 36 »36 ·) made of a non-wettable solder-resistant material, for example chromium or polytetrafluoroethylene, for receiving the workpiece (2) such that the selected part of it is outside the channel, during which the selected. Part immediately adjacent remaining part of the workpiece (2) is located within the channel (28, 28 ¹ J 36, 36 »), and by a device for supplying molten solder (20) to the selected part, the channel (28, 28 ·} 36, 36 ·) has such a width and the clearance between the workpiece (2) and the channel is such that molten solder (20) does not enter the channel, so that the solder only hits the. selected part is applied. 5 · Device according to claim 4, wherein the workpiece is a connecting element and forms part of a strip of connection elements and wherein the device comprises a solder bath and a device arranged in the bath for generating a solder wave and a mechanism for conveying the Strip of connection el emen th through the channel, characterized in that adjacent Connection elements (2) are arranged at a distance from one another which is sufficient to generate a capillary effect between the connection elements (2) to prevent, and that the channel (28, 28 »; 36, 36 ♦) in the generated solder wave (20) is positioned so that when the strip of connectors is conveyed through the channel (28, 28 * 5 36, 36), the selected portion of the workpiece is exposed to the molten solder (20) having a tape of solder around the selected portion forms. 6. Apparatus according to claim 5 »characterized by a mechanism (100) for pressing opposite sides (128, 130) of the solder tape (124) together after the solder tape (124) has been formed around the selected part of the workpiece ^ Qgg4« J / Q47 Q