Solder application stamp for applying solder on contact locations possessing small dimensions

Abstract

A solder application stamp embodied to transfer solder paste from a reservoir to a contact location of a circuit board. The solder stamp has a basic body having an end area and a protrusion, which protrudes out of the end area. The solder application to create solder paste dots of diameters as small as 10-300 ?m.

Claims

1. A solder application stamp embodied to transfer solder paste from a reservoir to a contact location of a circuit board, comprising: a basic body having an end area; and at least one protrusion, which protrudes out of said end area and has a protrusion area, wherein: said at least one protrusion, in a longitudinal section has an at least sectionally concave contour between said end area and said protrusion area; and whereby said solder application stamp is embodied to generate solder paste dots of a diameter of 10 ?m to 300 ?m.

2. The solder application stamp as claimed in claim 1, wherein: said protrusion area extends essentially parallel to said end area of said basic body.

3. The solder application stamp as claimed in claim 1, wherein: said protrusion area is so embodied that the ratio of said end area to said protrusion area corresponds at most to a factor of 10, preferably a factor of 7.5 and especially preferably a factor of 5.

4. The solder application stamp as claimed in claim 1, wherein: said protrusion area is so embodied that the ratio of said end area to said protrusion area corresponds at most to a factor of 35, preferably a factor of 21, and especially preferably a factor of 15.

5. The solder application stamp as claimed in claim 1, wherein: the maximum distance between said end area and said projected area and, thus, the height of the projection lies in the range of 50-250 ?m, preferably in the range of 80-150 ?m.

6. The solder application stamp as claimed in claim 1, wherein: the maximum distance between said end area and said projected area and, thus, the height of said projection lies in the range of 50-400 ?m, preferably in the range of 180-220 ?m, especially preferably in the range of 280-320 ?m.

7. The solder application stamp as claimed in claim 1, wherein: said projected area has a diameter in the range of 300-180 ?m, preferably in the range of 180-130 ?m, especially preferably in the range of 130-50 ?m.

8. The solder application stamp as claimed in claim 1, further comprising: a hydrophobic coating, which is applied on said basic body at least in a region adjoining the protrusion.

9. The use of a solder application stamp as claimed in claim 1, in an automated plant for repairing a circuit board, which has at least one defective component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be explained in greater detail based on the appended drawing, the figures of which show as follows:

(2) FIG. 1 is a flow diagram of the method of the invention,

(3) FIG. 2 is a schematic drawing illustrating the method steps,

(4) FIG. 3 is a schematic drawing of the solder application stamp of the invention; and

(5) FIG. 4 is a schematic bottom view of the solder application stamp of the invention.

(6) FIG. 1 shows a flow diagram of the method of the invention.

(7) In the first step, the defective component 2, which is secured via contact locations 3 mechanically and/or electrically on the circuit board 1, is removed. For this, the circuit board 1 is clamped into an automated plant, which has a circuit board holding unit. Preferably, the circuit board holding unit includes a facility for heating from underneath. This enables a preheating of the total circuit board 1. For removing the defective component 2 still soldered onto the circuit board 1, the automated plant is equipped with a multi-channel ring jet. The multi-channel ring jet is, in such case, embodied in such a manner that it, on the one hand, emits hot air and, on the other hand, can draw a vacuum, respectively air. In this way, the solder between the contact locations 3 of the defective component 2 and the contact locations 3 the circuit board 1 can be melted by means of the hot air. The size of the multi-channel ring jet is, in such case, dependent on the component size and is so selected that an essentially complete heating of the defective component 2, respectively the contact locations 3, occurs. After the solder 4 is melted, the defective component 2 is sucked in by means of the vacuum function of the multi-channel ring jet and the component 2 released from the circuit board 1.

(8) Preferably, in an intermediate step, it is provided that before additional working of the circuit board 1, there is a waiting period, until the automated plant and, thus, also the circuit board 1 have cooled off. Alternatively, the circuit board 1 can be further processed in an already cooled, second automated plant.

(9) In the second step, all circuit board side, contact locations 3, which have served for bonding the defective component 2 to the circuit board 1, are cleaned. Preferably, this cleaning occurs contactlessly. For this, the automated plant is equipped with a multi-channel cleaning jet. The multi-channel cleaning jet is, in turn, embodied in such a manner that it, on the one hand, emits hot air and, on the other hand, can draw a vacuum, respectively air, wherein the sucked air is conducted by a bypass through a filter. The contact locations 3 are visited by means of the multi-channel cleaning jet, wherein the hot air heats the remaining solder still present after removing the defective component 2, so that the solder can then be removed.

(10) In the third step, a solder paste 4 is applied on the cleaned circuit board side, contact locations 3. For this, the automated plant is equipped with a solder application stamp 5, which serves for transfer of the solder paste 4 from a reservoir 6 onto the contact location 3. The solder application stamp 5 is moved by a positioning unit of the automated plant over the reservoir 6 and at least partially brought into the reservoir 6, so that a wetting of the solder application stamp 5 occurs. In such case, the solder application stamp 5 is pushed into the reservoir 6 only up to a predefined first force, for example, 1 N.

(11) Following this, the solder application stamp 5 wetted with solder paste 4 is moved from the reservoir 6 to an earlier established position on the circuit board 1, where the substitute component 7 is to be secured. At the established, respectively predefined, position, the solder application stamp 5 is brought onto the circuit board side, contact location 3, for example, a copper pad, so that an applying, respectively transfer, of the solder paste 4 onto the contact location 3 occurs. In such case, the solder application stamp 5 is pushed with a predefined second force, for example, 0.7 N, onto the contact location 3. The positioning unit of the automated plant moves the solder application stamp 5 under force control, i.e. the force acting in the case of the setting, respectively pressing, of the solder application stamp 5 onto the contact location 3 is controlled by the positioning unit and should the force threaten to exceed a predefined (first and/or second) force, the setdown procedure is interrupted, respectively stopped.

(12) Serving as reservoir 6 can be, for example, a dip tub, which has a defined depth. The solder paste 4 is introduced into the dip tub 6 and extra solder paste 4 removed by means of a doctor blade. In this way, a very reproducible amount of solder paste 4 can be placed in the reservoir 6, respectively the dip tub. Additionally, the reservoir, respectively the dip tub, 6 can have a nano coating, in order to enable easy release of the solder paste 4.

(13) In the case, in which a plurality of contact locations 3 are to be provided with solder paste 4, the third step is correspondingly repeated multiple times or a solder application stamp 5 is used, which can simultaneously wet a number of contact locations 3.

(14) In the fourth step, the circuit board 1 is populated with a substitute component 7 provided for the defective component 2. In such case, the multi-channel ring jet already applied in the first step is used, in order to release the substitute component 7 from a component supply tape and to bring it to the desired position on the circuit board 1.

(15) In the fifth step, the substitute component 7 earlier placed on the circuit board 1 is soldered. In such case, the substitute component 7 placed on the preheated circuit board 1 is soldered onto the circuit board 1 by means of the hot air function of the multi-channel ring jet.

(16) FIG. 2 is a schematic drawing illustrating the method steps. In such case, there is shown in FIG. 2a), by way of example, a circuit board 1 with three components, wherein the left component 2 is defective. This defective component 2 is removed according to the above described, first step. FIG. 2b) shows the circuit board 1, after the defective component 2 has been removed and the circuit board side, contact locations 3 cleaned. FIG. 2c) shows the circuit board 1, after the solder paste 4 has been applied on the contact locations 3. FIG. 2d) shows the circuit board 1 with the substitute component 7 soldered on.

(17) FIG. 3 shows a schematic drawing of the solder application stamp 5 of the invention. This comprises a basic body 8 having an end area A.sub.E. Extending out of the end area A.sub.E is a protrusion 9, which has a protrusion area A.sub.P, which extends preferably essentially parallel to the end area A.sub.E of the basic body 8. Protrusion 9 is embodied in such a manner that it has in longitudinal section an at least sectionally concave contour 10 between the end area A.sub.E and the protrusion area A.sub.P. The solder application stamp 5 collects the solder paste 4 via the concave contour 10, when the solder application stamp 5 is brought into a reservoir 6.

(18) The maximum distance D of the projected area A.sub.P of the projection 9 from the end area A.sub.E of the basic body 8 lies in the range of 50-400 ?m, preferably in the range of 80-150 ?m. Found to be especially suitable is a maximum distance of about 300 ?m.

(19) The maximum distance D, in such case, is selected in such a manner that the end area A.sub.E of the basic body 8 is wetted with solder paste 4, when the solder application stamp 5 is introduced sufficiently into the reservoir 6 that the projected area A.sub.E contacts the floor of the reservoir 6. Such as already mentioned, there can serve as reservoir 6, for example, a dip tub, which, for example, has a depth in the range of 700 ?m to 400 ?m, preferably in the range of 400 ?m to 200 ?m, especially preferably in the range of 200 ?m to 40 ?m.

(20) FIG. 4 shows a schematic drawing of the bottom view of the solder application stamp 5. The end area A.sub.E is square in such case. Other options include, however, also other geometric forms, such as, for example, a round cross section. Protrusion 9 and, thus, also the protrusion area A.sub.p are embodied in such a manner that these have a round cross section. The cross sectional area of the protrusion 9 steadily decreases, in such case, from the end area A.sub.E to the protrusion area A.sub.P. Besides a round cross section, however, other options for geometric forms include especially rectangular or square cross-sectional shapes.

(21) The cross sectional area of the essentially square basic body 8 lies in the range of 0.16 mm.sup.2 to 0.64 mm.sup.2, preferably in the range of 0.64 mm.sup.2 to 1 mm.sup.2, especially preferably in the range of 1 mm.sup.2 to 2.25 mm.sup.2.

(22) The diameter of the projected area A.sub.P lies, as a function of contact location to be wetted, in the range of 300-180 ?m, preferably in the range of 180-130 ?m, especially preferably in the range of 130-50 ?m.

(23) Furthermore, the solder application stamp shown in FIG. 3 includes a hydrophobic coating (11), which is applied at least on a part of the surface of the basic body (8). As is evident from FIG. 3, the basic body is provided with the hydrophobic coating at least in the region adjoining the protrusion. The hydrophobic coating can, in such case, extend further over the entire basic body up to the side of the basic body facing away from the end area.

(24) Furthermore, as brought out above, it advantageous when the floor of the reservoir, respectively the dip tub, likewise is provided with a hydrophobic coating.

(25) A solder application stamp 5 constructed in such a manner can be used for repairing a circuit board 1 having at least one defective component 2, wherein the component 2 has at least one contact surface 3 having a maximum dimension of 500 ?m to 200 ?m, preferably a maximum dimension of 470 ?m to 160 ?m. In advantageous manner, the solder application stamp 5 can be used for repairing a circuit board 1 having at least one defective component 2, wherein the component 2 has at least two contact surfaces, wherein the contact locations 3 are separated from one another by 175 ?m, preferably 150 ?m, especially preferably 125 ?m.