MANUFACTURING LINE FOR SOLDERING

Abstract

The disclosure relates to a manufacturing line for soldered components on a circuit board, comprising a soldering oven including at least two temperature zones having a predetermined temperature profile, a transport apparatus embodied to transport circuit boards through the temperature zones, and a control system, wherein, in at least one of the temperature zones, at least two heating elements are arranged such that a to-be-soldered surface of each circuit board is heated by the heating elements, wherein, in at least one of the temperature zones, at least two air circulators are arranged in the transport direction offset from one another and facing the surface to be soldered, and wherein the control system is configured to control the heating elements and the air circulators such that the to-be-soldered surface of the circuit board is heated according to the predetermined temperature profile.

Claims

1-15. (canceled)

16. A manufacturing line for soldering components on a circuit board, the manufacturing line comprising: a soldering oven including at least two temperature zones having a predetermined temperature profile along a transport direction through the soldering oven, wherein at least one of the at least two temperature zones includes at least two air circulators offset from one another in the transport direction; a transport apparatus embodied to transport circuit boards through the at least two temperature zones of the soldering oven in the transport direction; and a control system, wherein: in at least one of the at least two temperature zones, at least two heating elements are disposed such that a to-be-soldered surface of each circuit board transported through the soldering oven is heated by the at least two heating elements; the at least two heating elements are offset from one another in the transport direction and are directed toward the to-be-soldered surface; the at least two air circulators are directed toward the to-be-soldered surface; and the control system is configured to control the at least two heating elements and the at least two air circulators such that the to-be-soldered surface of each circuit board is heated according to the predetermined temperature profile.

17. The manufacturing line of claim 16, wherein at least two additional heating elements are disposed in at least one of the at least two temperature zones such that an opposing surface of each circuit board is heated by the at least two additional heating elements, wherein the opposing surface is opposite the to-be-soldered surface, and wherein the at least two additional heating elements are offset from one another in the transport direction and are directed toward the opposing surface.

18. The manufacturing line of claim 17, wherein, in at least one of the temperature zones, two additional air circulators are offset from one another in the transport direction and are directed toward the opposing surface.

19. The manufacturing line of claim 18, wherein the control system is further configured to control the at least two heating elements, at least two additional heating elements, the at least two air circulators and the two additional air circulators such that both the to-be-soldered surface and the opposing surface of each circuit board are heated according to the predetermined temperature profile.

20. The manufacturing line of claim 19, wherein, according to the predetermined temperature profile, the to-be-soldered surface and the opposing surface of each circuit board are heated to different temperatures in at least one of the at least two temperature zones.

21. The manufacturing line of claim 18, wherein the at least two air circulators are controlled using revolutions per minute (RPM) and/or the two additional air circulators are controlled using RPM.

22. The manufacturing line of claim 21, wherein: according to the predetermined temperature profile, a temperature of a first temperature zone is greater than a temperature of a second temperature zone, the first temperature zone adjacent the second temperature zone; both the first temperature zone adjacent the second temperature zone includes air circulators and/or additional air circulators; and the RPM of the air circulators in the first temperature zone is less than or equal to the RPM of the air circulators in the second temperature zone, and/or the RPM of the additional air circulators in the first temperature zone is less than or equal to the RPM of the additional air circulators in the second temperature zone.

23. The manufacturing line of claim 16, wherein the soldering oven has at least three temperature zones, defining as a preheat zone, a soldering zone and a cooling zone.

24. The manufacturing line of claim 16, wherein the soldering oven is a reflow soldering oven.

25. The manufacturing line of claim 16, wherein the soldering oven is a backside reflow soldering oven.

26. The manufacturing line of claim 16, wherein the manufacturing line is embodied for soldering with a lead-free solder paste.

27. The manufacturing line of claim 16, wherein the transport apparatus is configured to transport the circuit boards through each of the at least two temperature zones at different transport speeds.

28. The manufacturing line of claim 16, wherein: the control system is configured with different operating modes stored therein for operating the manufacturing line; each operating mode includes a predetermined temperature profile of the at least two temperature zones; and a temperature profile of a given operating mode corresponds to the soldering oven, a type of solder paste applied for soldering in the solder oven, and/or types of the components.

29. The manufacturing line of 28, wherein: a first operating mode includes a first temperature profile; a second operating mode includes a second temperature profile different from the first temperature profile; and a difference between temperatures of the first temperature profile and the second temperature profile is controlled, at least in part, by the at least two air circulators.

30. The manufacturing line of claim 29, wherein the difference between the temperatures of the first temperature profile and the second temperature profile is further controlled, at least in part, by a transport speed of the transport apparatus.

Description

[0042] The invention will now be explained in greater detail based on the appended drawing, the figures of which show as follows:

[0043] FIG. 1 a schematic illustration of the manufacturing line of the invention;

[0044] FIG. 2a different temperature profiles;

[0045] FIG. 2b conversion times between temperature profiles with the manufacturing line of the invention;

[0046] FIG. 3 the lessening of reject rate with the manufacturing line of the invention.

[0047] FIG. 1 shows a schematic illustration of the manufacturing line of the invention with a soldering oven 3 and a transport apparatus, based on which a circuit board 2 with components 1 is transported in a transport direction rt with a transport speed vt through temperature zones Z1, Z2, Z3 of the soldering oven. In this example, components 1 are arranged on a surface 10 to be soldered and on an opposite surface 11. Of course, also other embodiments are possible. The soldering oven 3 includes in this example of an embodiment three temperature zones Z1, Z2, Z3. In the example shown here, four heating elements 60, 61, 62, 63 and three air circulators 70, 71, 72 are arranged in the first temperature zone Z1 offset one after the other in the transport direction rt. Also arranged in the first temperature zone Z1 offset one after the other in the transport direction rt are four additional heating elements 80, 81, 82, 83 and two additional air circulators 90, 91. For purposes of simplification, only the heating elements and air circulators of the first temperature zone Z1 are shown in this example of an embodiment. Preferably, each temperature zone Z1, Z2, Z3 of the soldering oven 3 should have at least one heating element.

[0048] Other embodiments are, of course, possible, especially relative to the number of heating elements; the, in given cases present, additional heating elements; the air circulators and the, in given cases present, additional air circulators. The number of air circulators is in the context of the invention preferably less than or equal to the number of heating elements and, in given cases, the number of additional air circulators is preferably less than or equal to the number of additional heating elements.

[0049] The transport plane is, in such case, arranged in parallel with the plane of the circuit board 2. In such case, such as shown in this example of an embodiment, the transport plane of the transport apparatus 4 can be arranged centrally between the heating elements 60, 61, 62, 63 and the additional heating elements 80, 81, 82, 83. It is, of course, also an option that the transport plane is arranged nearer or farther from the heating elements 60, 61, 62, 63 than from the additional heating elements 80, 81, 82, 83. For example, an option is to match the separation of the heating elements 60, 61, 62, 63 or the additional heating elements 80, 81, 82, 83 from the transport plane to the dimensions of the components 1.

[0050] The invention is suited especially also for such a non-symmetric construction, since RPMs f1, f2, f3 of the air circulators 70, 71, 72 can be controlled separately from RPMs g0, g1 of the additional air circulators 90, 91.

[0051] For setting RPMs f1, f2, f3, for example, a conventional rotational speed converter is used. Stored in the control system 5 are different operating modes 51, 52. For such purpose, the control system 5 includes, for example, a programmable logic control unit (PLC), such as commonly applied in process and automation technology.

[0052] Shown schematically in FIG. 2a are different temperature profiles Tp1, Tp2, which are commonly present in reflow soldering. In the preheat zone Z1, the component to be soldered is preheated. The actual soldering process (i.e., the forming of material bonded connections) takes place in the soldering zone Z2. This is where the temperature is, as a rule, the highest. In the cooling zone Z3, there is then a cooling of the soldered item. The two temperature profiles Tp1, Tp2 can be set by the choice of operating mode 51, 52.

[0053] According to the invention, in such case, the temperature profiles Tp1, Tp2 of the different operating modes 51, 52 are achieved just by changed operation of the air circulators 70, 71, 72 and, in given cases, the additional air circulator 90, 91. In the case of equal operation of the heating elements 60, 61, 62, 63 and, in given cases, the additional heating elements 80, 81, 82, 83 the temperatures present on the surface 10 of the circuit board 2 and, in given cases, on the opposite surface 11 of the circuit board 2 can be so set that a particular temperature profile Tp1, Tp2 is present in the temperature zones Z1, Z2.

[0054] In this way, conversion times can be avoided and delays in the manufacturing significantly minimized. This is shown in FIG. 2b. There, typical conversion times between typical temperature profiles with a process optimized manufacturing line A of the state of the art are compared with conversion times of the manufacturing line B of the invention. Experiments show that conversion times can be lessened with the manufacturing line of the invention to a tenth of what they were. This is a significant advantage, since idle times in the production can be similarly lessened. Also, costs are reduced therewith.

[0055] A further advantage of the invention is that backside reflow soldering with a lead-free solder paste 12 is enabled for the first time. By air circulators 70, 71, 72 and additional air circulators 90, 91 arranged in a temperature zone Z1, Z2, Z3 offset one after the other in the transport direction rt, a mixing of air layers in the direction perpendicular to the transport plane can be prevented. In this way, a stable and large temperature difference can be established between the surface 10 to be soldered and the other surface 11.

[0056] On the other hand, the manufacturing line of the invention provides with a soldering oven 3 embodied for reflow soldering improved results in the protective soldering of groups of components 1 on circuit boards. This is shown in FIG. 3. For such a standard process, a process optimized manufacturing line A of the state of the art was compared with the manufacturing line B of the invention. In such case, the number of defective solder locations was registered. Referred to as defective solder locations in the context of the present invention are solder locations with components 1, which have slipped on the circuit board 2 or have only partly melted solder joints. The experimental investigations show that the number of defective solder locations with the manufacturing line B of the invention can be lessened by about 30% in comparison with the manufacturing line A of the state of the art.

LIST OF REFERENCE CHARACTERS

[0057] 1 a component [0058] 2 circuit board [0059] 3 soldering oven [0060] 4 transport apparatus [0061] 5 control system [0062] 51,52, . . . operating modes [0063] 60,61, . . . heating elements [0064] 70,71, . . . air circulators [0065] 80,81, . . . additional heating elements [0066] 90,91, . . . additional air circulators [0067] 10 surface to be soldered [0068] 11 other surface [0069] 12 solder paste [0070] Z1,Z2, . . . temperature zones [0071] rt transport direction [0072] Tp,Tp1,Tp2, . . . temperature profiles [0073] f0, f1,f2,f3 RPMs of the air circulators [0074] g0,g1,g2,g3 . . . RPMs of the additional air circulators [0075] vt transport speed