NL1024476C2 - Device for selective soldering of components on a print plate with classical connecting wires includes means to blow oxygen on solder to make sure its flow in correct direction to prevent formation of bridges between connecting wires - Google Patents

Abstract

Device for the selective soldering of components on a printed plate (6) provided with classical connecting wires (9). The solder (7) always flows in the correct direction, opposite to the movement of the print plate, in order to prevent formation of bridges between the connecting wires. This is achieved by blowing a gas low in oxygen content against the solder so that the solder is forced to flow in the correct direction. The gas feed can be quickly switched on and off in order to achieve optimal blowing during soldering. In order to force the solder still more to flow in the correct direction, the outflow pipe (4) is made from partly moistenable material and partly non-moistenable material.

Description

DEVICE FOR SELECTIVE SOLDERING.

The invention relates to a device for soldering onto printed circuit boards of components, which are provided with traditional connecting wires.

Increasingly, so-called components are used for surface mounting, which generally have small dimensions and which are soldered to a printed circuit board by means of a reflow soldering process. A large number of printed circuit boards also contain components for which the reflow process is less suitable. This generally concerns components such as connectors and electrolytic capacitors which are provided with traditional connection wires, and wherein the connection wires protrude through openings provided in the printed circuit board beyond the bottom of the printed circuit board. A soldered connection must then be made on this underside. For making these solder connections, a soldering device is known, comprising: - a vessel for storing and heating molten solder; - transport device for transporting and discharging objects to be soldered over the vessel; At least one tube protruding vertically above the soldering vessel; through which the molten solder flows and overflows through the outlet opening, back into the vessel described above; pumping device for supplying molten solder to the underside of the tube 30; and transport device for moving the underside of the objects to be soldered and the top of the tube at least in close proximity to each other.

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The tube thus forms a small wave soldering device. I

I Hereby it is possible to carry out the soldering process. I

I by just moving the printed circuit board over the soldering wave. I

I This will cause the solder along the connecting wires and the I

I 5 flow into the holes on the bottom of the printed circuit board. I

The prior art device has as I

I have a disadvantage that the solder is not always in the right I

I direction, that is, in the I

I opposite direction of the circuit board movement. I

I 10 The interplay of forces during soldering leads to an I

I unstable flow behavior of the solder. This leads to I

I bridging between two or more connection pins. This I

I also means that in the design of the printed circuit board I

I must take into account the room for this I

Flowing-out solder current; after all, I

I no components are present. I

I In the current state of the art, the form of I

I the vertical protruding tube forced the solder to I

I flow out one side, but this does not always lead to I

The desired result. I

The object of the invention is to provide an I

Such a soldering device in which the solder is always I

I in the right direction, opposite to the movement of the I

I printed circuit board. I

Experience has shown that, with a stable outflow I

I of the solder in the right direction, bridging becomes I

I and the soldering current will surround surrounding components I

I do not damage. I

According to a first embodiment, an oxygen-poor I

I blow gas against the solder, such that the solder I

I is forced to flow in one direction. I

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According to a specific embodiment, the gas supply can be switched on and off quickly in order to be able to blow as optimally as possible during soldering.

To obtain an optimum soldering temperature, it is desirable to adjust the gas temperature.

According to another preferred embodiment, the vertical outflow tube is provided on the outflow side with a wettable material, while the remaining part of the tube is made from a non-wettable material. The non-wettable material will repel solder and the solder will drain along the wettable material that attracts solder.

According to another preferred embodiment, a strip of material is mounted next to the vertical outflow tube.

This strip is made of wettable material and will attract solder. Instead of a strip, it is also possible to use other shapes, for example around wettable material.

It is noted that a device is known from German patent specification DE19807696 wherein a low-oxygen gas is supplied around a vertically protruding tube through which molten solder flows and overflows through the outlet opening. In this device the heated gas is used to obtain a low-oxygen soldering environment. The solder in this device does not overflow in one particular direction, but over the entire edge of the vertically protruding tube, which demands more free space on the printed circuit board.

The invention will be explained in more detail below with reference to the accompanying figures, in which: figure 1 shows a schematic overview of a device according to the invention; 1024476_

Figure 2 is a schematic overview of the device I

for the supply of the oxygen-depleted gas and for the fast I

switching on and off this gas; I

figure 3 shows a detail view of a vertical I

5 outlet tube with wettable portion; I

Figure 4 is a detailed view of a vertical I

outflow tube with wettable strip. I

Figure 1 shows a soldering vessel (1) that is filled I

with molten solder (7). For melting and the I

10 to keep the solder melted are the position of the I

heating elements not included in the technology

drawing. I

A vertically protruding tube I is present in the soldering vessel (1)

(4). Solder (7) becomes I by means of pump (3)

15 of the soldering vessel (1) through the vertical tube (4) I

pumped. The solder (7) will then be taken from the vertical I

projecting tube (4) back into the soldering vessel (1). I

To make a soldered connection, a te I

soldering the printed circuit board (6) by means of a transport I

Device of which only the grippers (8) are drawn, I

up to a short distance from the vertically protruding tube I

(4). The circuit board (6) is then passed over the I

vertically protruding tube (4) dragged, the I

flooding solder (7) via the bottom of circuit board I

(6) the connection between the printed circuit board (6) and the I

connecting wires (9) to the components (10). I

To force the solder (7) during the soldering process I

to extend over the inclined plane (5) of the vertically protruding

tube (4) is to be flooded behind the vertical I

A protruding tube (4) through a blower (12) an I

low oxygen gas, for example nitrogen, in the correct I

direction across the outflow opening (19) of the vertical I

protruding tube (4). I

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The gas (18) flows via the blower mouth (12) against the flowing solder (7) in the direction of the inclined surface (5). The solder will choose the path of the least resistance and will flow back over the inclined surface (5) of the vertical tube 5 (4) into the solder vessel (1).

Figure 2 shows a device for quickly switching off the supplied oxygen-depleted gas (18). This may be necessary to prevent the liquid solder (7) from being blown through holes present in the printed circuit board (6). The device consists of a heating element (11) through which an oxygen-poor gas (18) is blown.

Heating the oxygen-depleted gas (18) is necessary to not force the liquid solder joint to solidify.

A distribution valve (15) is open, whereby the supplied oxygen-depleted gas (18) is blown into the free space via outflow mouth (16). The distribution valve (15) is closed during soldering. As a result, the gas (18) will be blown through blow nozzle (12) against the solder (7). A cylinder (17) ensures that the distribution valve (15) can be opened and closed quickly, as a result of which the low-oxygen gas (18) can switch in a short time between blowing against the solder (7) or in the free space.

Thus, liquid solder is prevented from ending up on unwanted places on the printed circuit board (6).

Figure 3 shows another embodiment for forcing the solder to flow in one direction. In this embodiment, use is made of wettable and non-wettable materials used. The property of a wettable material 1024478

I 6 I

I is that the solder (7) attracts, while a non I

I repels wettable material solder (7). I

The solder which flows from the vertical tube (4) will I

I through the oblique plane (5) made of an I

Wettable material are attracted. The I

I vertically protruding tube (4) is made from a staple I

I wettable material, for example stainless steel, and I

I will reject solder. I

Figure 4 shows an embodiment of an I

I vertically protruding tube (4) made from a staple I

A wettable material with a conductive strip (14). The I

The conductive strip (14) is made of a wettable material

I made and this will cause the outflowing solder (7) I

I 15. I

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Claims (5)

A solder device comprising: - a vessel (1) for containing and heating molten solder (7); - transport device (8) for transporting and discharging objects to be soldered over the vessel (1); - at least one tube (4) protruding above the soldering vessel (1); through which the molten solder (7) flows and overflows through the outflow opening (19), back into the vessel (1) described above; - pumping device (3) for supplying molten solder (7) to the underside of the tube (4); and conveying device (8) for moving the underside of the objects to be soldered and the top of the tube (4) at least in close proximity to each other, characterized in that through the outflow opening (19) the oxygen-poor gas (18) it is blown that the solder (7) that overflows through the outflow opening (19) drains in the correct direction. 2. Soldering device as claimed in claim 1, characterized in that the vertically extending tube (4) is made on one or more sides of a wettable material (5) and on the remaining sides of non-wettable material (4), so that the solder (7) will flow in the correct direction along the wettable part (5). 3. A soldering device as claimed in claim 1 and / or 2, characterized in that a wettable strip (14) is mounted next to the vertically protruding tube (4), so that the solder (7) overflowing through the outlet opening (19) runs along this strip (14) will drain. 1024476 I 8 I A soldering device as claimed in claim 1, characterized in that the supply of the oxygen-poor gas (18) can be switched on and off quickly. The device consists of a heating element (11) through which a low-oxygen gas (18) is blown. A distribution valve (15) is open, through which the oxygen-depleted gas (18) supplied is blown into the free space via outflow mouth (16). The distributor valve (15) is closed during soldering. As a result, the gas will be blown through blow nozzle (12) against the solder (7). A cylinder (17) ensures that the II manifold valve (15) can be quickly opened and closed II, so that the low-oxygen gas (18) can switch in a short II time between blowing against the solder (7) on II or the free space. I 5. A soldering device as claimed in claim 1, characterized in that the temperature of the oxygen-poor gas II (18), which flows out of the outflow tube (12), is regulated II so as not to coagulate the liquid solder (7). . For this purpose, the low-oxygen gas (18) is first passed through a heating element (11) and heats up to the desired temperature and then blown through the outflow tube I (12). I 1024476