DE9110924U1 - Device for the dosed application of adhesive to circuit boards - Google Patents

Description

6 IN 1 EN

Siemens AG

Device for the dosed application of adhesive to circuit boards
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When circuit boards are automatically fitted with SMD components, drops of adhesive are first placed in the specified placement positions on the circuit board, which fix the subsequently applied SMD components to the circuit board until the soldering process. A movable dosing device is provided for the dosed application of the adhesive to the circuit boards, from whose dosing needle a drop of adhesive is pressed onto the circuit board after approaching an application point. If the adhesive supply in this dosing device is used up or the dosing needle is clogged, no adhesive is applied to the circuit board. In this case, the SMD components placed in the downstream placement stations are not fixed to the circuit boards.

The invention specified in claim 1 is based on the problem of creating a device for the metered application of adhesive to circuit boards, in which the application of adhesive drops to the respective application points can be reliably monitored.

This problem is solved by the measures of claim 1.

The advantages achieved with the invention are in particular that, due to the special arrangement of the light source and optical sensor, the output signals of the sensor before and after the application of a drop of adhesive are significantly different and thus a reliable statement can be made about the presence of a drop of adhesive. Since the control of the drops of adhesive placed takes place at the same time as the dosing, downstream control devices can be omitted.

An advantageous embodiment of the invention is defined in claim

6 H 41 EN

2. The development according to claim 2 enables a particularly high signal swing of the output signals of the sensor due to the flat beam guidance between the light source and the sensor.
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An embodiment of the invention is explained with reference to Figures 1 and 2.

Show it:
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Figure 1 shows a device for the metered application of adhesive to circuit boards before applying a drop of adhesive and

Figure 2 shows the device according to Figure 1 after the application of a drop of adhesive.

Figure 1 shows a highly simplified schematic representation of a dosing device Dv that can be moved in the X, Y and Z directions, the dosing needle Dn of which is located exactly above an application point A of a circuit board designated Lp. On one side, a light source Lq is attached to the dosing device Dv using a holder Hl, while on the opposite side, an optical sensor S is attached to the dosing device Dv using a holder H2. The optical axes AOl and AO2 of the light source Lq and sensor S, which are arranged symmetrically to the Z direction in the illustrated embodiment, enclose an angle W that should be at least 30° and preferably at least 90°.

In the measuring position of the dosing device Dv shown in Fig. 1, which is above the actual application position, the optical axes AOl and AO2 of the light source Lq and sensor S intersect exactly at the intended application point A on the surface of the circuit board Lp. The light beam Ls generated by the light source Lq therefore hits the application point A in this measuring position, whereby the reflected light Ll is detected by the sensor S and its output

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signal ASl is fed to a device designated EV.

After the measuring process described above, the dosing device Dv is lowered in the Z direction into the actual application position and in this position a drop of adhesive KT is pressed from the dosing needle Dn onto the circuit board Lp. The dosing device Dv then moves up again in the Z direction, whereby this movement up after the application of the drop of adhesive KT is shown in Fig. 2. It can be seen that the light beam Ls of the light source Lq is reflected by the drop of adhesive KT, whereby the reflected light is designated L2. Since the light L2 now detected by the sensor S differs significantly in its intensity from the light Ll reflected in the measuring position according to Fig. 1, the sensor S generates an output signal AS2 which differs significantly from the output signal ASl. The device EV for comparing the output signals ASl and AS2 then generates a comparison signal VS based on the signal swing mentioned, which allows the conclusion that a drop of glue KT was actually applied to the circuit board Lp. If the output signals ASl and AS2 do not differ or only differ slightly, no comparison signal VS is output and it can be concluded that no drop of glue was applied. In this case, the cause of the fault can then be remedied immediately.

Claims (2)

6 HMDE Protection Claims 1. Device for the metered application of adhesive to printed circuit boards (PCBs), with a dosing device (Dv) which can be moved in the X, Y and Z directions and from whose dosing needle (Dn) a drop of adhesive (KT) is pressed onto the circuit board (Lp) after approaching an application point (A),
10 a light source (Lq) which can be moved with the dosing device (Dv), the light beam (Ls) of which is directed at the application point (A) in a measuring position of the dosing device (Dv) located above the application position,
15 an optical sensor (S) movable with the dosing device (Dv) for detecting the light (Ll, L2) reflected from the application point (A) or from an adhesive drop (KT) in the area of the measuring position of the dosing device (Dv) and
20 a device (EV) for comparing the output signals (ASl, AS2) of the sensor (S) before and after the application of a drop of adhesive (KT), whereby - the optical axes (AOl, A02) of the light source (Lq) and the sensor (S) enclose an angle (W) of at least (3O ⁰ C). 2. Device according to claim 1, characterized, that the optical axes (AOl, AO2) of the light source (Lq) and sensor (S) enclose an angle (W) of at least 90°.