SOLDER ELEMENT

Abstract: The invention relates to a solder element for making electrically conducting connections on either side of a printed circuit board, comprising an electrically conducting wire which is provided with at least one body composed of solder material and flux material, wherein the body is preferably composed of solder material and provided with a recess in which the flux material is received, or the flux material is preferably accommodated between two bodies of solder material arranged on the wire.

Description: SOLDER ELEMENT The present invention relates to a solder element for making electrically conducting soldered connections on either side of a printed circuit board. The European patent application 126,164 describes a method for making a switch connection between both surfaces of a substrate, in particular a printed circuit board, wherein use is made of an electrically conducting wire provided with a ball of solder material. This solder element is soldered on the printed circuit board during its passage through a solder apparatus. During this passage flux material is first foamed on the side of the printed circuit board remote from the __ electrical elements, which material can pass through the bores in the printed circuit board. In the solder bath the ends of the solder element are subsequently soldered to the conducting surface of the printed circuit board, while under the influence of heat and as a result of the flux material having passed through the bores a soldered connection is likewise formed on the other side of the printed circuit board. This known method has the drawback that since operation takes place with flux material on only one side this flux material can pass through the bores in the printed circuit board in order to there form a soldered connection with the solder material from the solder ball. Flux material on the side of the printed circuit board where the electrical components are also situated is undesirable as a consequence of a supposedly harmful effect of the flux material on the electrical components. Another drawback is that on the side coming into contact with the flux material and solder material the conducting layer must extend to the perimeter of the bores since otherwise an inadequate soldered connection is realized. This considerably limits the design freedom for the circuit board. The present invention has for its object to provide a solder element for the above stated method with which the above stated drawbacks are however obviated as far as possible. The present invention is based on the discovery that by dosed, directed and measured use of flux material on the side of the printed circuit board on which the electrical components are situated, there will be substantially no harmful effect on these electrical components, so that in order to make the soldered connection on this side it is possible to dispense with the use of flux material which passes through the bore in the printed circuit board in more or less uncontrolled manner during passage through the flux bath. The present invention therefore provides a solder element for making electrically conducting connections on either side of a printed circuit board, comprising an electrically conducting wire which is provided with at least one body composed of solder material and flux material . According to a first embodiment the solder body can be composed of solder material and be provided with a recess in which the flux material is received. By direct¬ ing the recess in a particular direction it is even possible that, since the flux material flows out of this recess under the influence of heat, a soldered connection is made only in this flow direction. According to another embodiment the flux material is accommodated between two bodies of solder material arranged on the wire, with which configuration a soldered connection can be realized in one direction as well as in a number of directions. According to a third embodiment the flux material is incorporated in the body of solder material. According to a fourth embodiment the flux material is arranged on the outside of the body of solder material . Mentioned and other features of the solder ele- ment according to the invention will be further elucidat¬ ed hereinbelow with reference to a number of embodiments which are given only by way of example without the inven¬ tion being deemed limited thereto. In the drawing: figures 1-4 each show a view of different embodiments of the solder element according to the inven¬ tion; figures 5 and 6 show the method for making electrically conducting soldered connections on two sides of the printed circuit board with the solder element shown in figure 2; figure 7 shows a view of a variant corresponding with figure 6; and figure 8 shows a series of solder elements 2 which are arranged at mutual distance between two mutual¬ ly adhered strips of adhesive tape. Figure 1 shows a solder element 1 according to the invention. Solder element 1 comprises an electrically conducting wire 5 around which is arranged a cylindrical solder body 6 which consists of solder material 7 in which is incorporated flux material 8. Figure 2 shows a solder element 8 according to the invention built up of an electrically conducting wire 5 and two solder bodies 9 constructed as split rings and clamped as such on wire 5. The annular space 10 is filled with flux material 8 which is therefore enclosed in axial direction by the solder bodies 9. Figure 3 shows a solder element 3 according to the invention which is built up of two solder bodies 11 which take the form of a split ring, which solder bodies 11 are connected by a cross-piece 12, whereby the two bodies 11 are connected non-releasably to each other. This ensures a desired distance between the two bodies 11 and therefore ensures that a determined quantity of flux material 8 fills the space 13 located between bodies 11. Figure 4 shows another solder element 4 according to the invention which comprises a substantially cylindrical solder body 14 provided with a radially directed recess 15 which is filled with flux material 8. It will be apparent that, when heat is supplied to these solder elements, in the case of the solder elements 3 and 4 the outflow of flux material in particu¬ lar directions can be prevented (by cross-piece 12) or enhanced by the direction of the recess 15. Figures 5 and 6 show a method for making electrically conducting soldered connections on a printed circuit board 16 which comprises a non-conducting base 17 of plastic material having selectively arranged thereon strips 18-20 of electrically conducting material lying at a distance from the perimeter of the bores 21 arranged in the base 17. As shown in figure 5, the solder element 2 is placed with its legs protruding through bores 21 and bent round on the other side so that the solder element 2 cannot leave the printed circuit board 16 in undesirable manner. The printed circuit board 16 is subsequently guided through a solder apparatus wherein the underside 24 is provided with flux material and then solder material, whereby the legs 22 and 23 are welded via a soldered connection 25 to the strips 19 and 20. No flux material and solder material reaches the top side 26 but an adequate soldered connection 27 can be formed there according to the invention in that under the influence of heat the flux material 8 first flows and both the bodies 9 then melt to form the soldered connection to the electrically conducting strip 18. In the situation shown in figure 7 the solder element 2 extends with its leg 23 over an electrically conducting strip 29 provided with an electrically insu¬ lating layer 28. It is thus possible to realize an elec¬ trically conducting soldered connection between the strips 18, 19 and 20 while the electrically conducting strip 29 is bridged by solder element 2. This provides further freedom in the designing of printed circuit boards. As electrically conducting wire for solder ele¬ ments according to the invention any normal electrically conducting material can be used, such as copper. As solder material can be applied any typical solder material such as Sn/43Pb43/Bil4. As flux material can be applied any normal flux material as long as it flows before the solder material melts. Typical flux materials can for instance be used which contain 0.35% w/w halides. Figure 8 shows a plurality of solder elements 2 which are arranged with the electrically conducting wire at mutual distance between two strips of adhesive tape 30, 31. The solder elements can be mounted in the printed circuit board 16 in simple manner, for instance with a robot, in that the wire 5 between the strips of adhesive tape 30, 31 is cut out, wherein the length of the legs 22, 23 can still be chosen.

Claims: CLAIMS 1. Solder element for making electrically con¬ ducting connections on either side of a printed circuit, board, comprising an electrically conducting wire which is provided with at least one body composed of solder material and flux material . 2. Solder element as claimed in claim 1, wherein the body is composed of solder material and provided with a recess in which the flux material is received. 3. Solder element as claimed in claim 1, wherein the flux material is accommodated between two bodies of solder material arranged on the wire. 4. Solder element as claimed in claim 1, wherein the flux material is incorporated in the body of solder material . 5. Solder element as claimed in claim 1, wherein the flux material is arranged on the outside of the body of solder material .

Inventors: DE KEIZER JOHANNES CORNELIS, DEKKER JAN, GODIJN PAUL WILLEM, OUD MARTINUS ADRIANUS, WELLING ANTONIUS JOHANNES, DE KEIZER, JOHANNES, CORNELIS, DEKKER, JAN, GODIJN, PAUL, WILLEM, OUD, MARTINUS, ADRIANUS, WELLING, ANTONIUS, JOHANNES
Applicants: DEKKER JAN, GODIJN PAUL WILLEM, KEIZER JOHANNES CORNELIS DE, OUD MARTINUS ADRIANUS, WELLING ANTONIUS JOHANNES, WITMETAAL B V, DE KEIZER, JOHANNES, CORNELIS, DEKKER, JAN, GODIJN, PAUL, WILLEM, OUD, MARTINUS, ADRIANUS, WELLING, ANTONIUS, JOHANNES, WITMETAAL B.V.
Application year: 1996
Main classification: H01R9
IPC codes: H01R12, H05K1, H05K3