In wave soldering processes, a work piece, e.g. a printed circuit board, which is to undergo soldering treatment is passed over at least one wave of solder created by means of a solder reservoir. Advantageously, an inert gas atmosphere is created above the solder reservoir, whereby oxygen is largely excluded. At least part of the work piece is brought into contact with the wave of solder. As solder, typically tin alloys are used. Such soldering devices are known e.g. from DE 195 41 445 A1 or DE 29 823 860 U1 .

The device as disclosed in DE 29 823 860 U1 uses diffusers provided as porous tubes with a specified pore size to supply nitrogen. From US 2008/0067219 A1 , it is known to use a gas diffuser to evenly distribute inert gas with a low gas flow across the entire area of the wave.

The use of an inert gas such as nitrogen serves to prevent oxidation of the solder. In wave soldering, oxidation is further increased by the wave agitation used in wave soldering processes. Oxidation not only generates substantial amounts of dross, but also negatively influences the solder joint quality and reliability. Using inert gases, such as nitrogen, essentially avoids these negative effects.

One of the biggest problems in connection with the use of inert gases is that the diffusers are subject to contamination and blockage. This is especially the case when using a porous tube as a diffuser. The reason for this problem mainly lies in the fact that, before a printed circuit board is transported to the solder wave, it is sprayed with flux, which consists of rosin and organic solvent. Flux is thus volatile and will condense on the surface of the diffuser. Also, in case the diffuser is adjacent to the surface of the molten solder, it is also easily contaminated by solder. A diffuser contaminated and partly blocked in this way can lead to an unbalanced gas distribution. Thus, regular cleaning and maintenance procedures are necessary. However, current cleaning procedures are cumbersome as well as time and cost consuming. Also, additional equipment and wet chemicals are typically used, leading to added costs.

The object of the invention is thus to provide a more efficient and less time and cost intensive method for cleaning diffusers and also other components used in a wave soldering apparatus. This object is achieved by the device with the features of claim 1 and a method with the features of claim 6.

With the invention, a highly effective device and method for cleaning components of a wave soldering apparatus which have been exposed to solder and/or flux during wave soldering is provided. The device and method according to the invention are easy to use and can be maintained or used at low cost.

Preferred embodiments of the invention are the subject matter of dependent claims. According to a preferred embodiment, the holding means for holding a component to be cleaned within the treatment chamber is provided as a holding means for a diffuser, wherein an inert gas, especially nitrogen, can be blown into the treatment chamber through the holding means and into and/or through the diffuser. Hereby a positive pressure relative to the surrounding area of the treatment chamber can be maintained within the diffuser. Thus, solder and/or flux separated from the diffuser during execution of the method according to the invention can be effectively removed from (blown of) the diffuser.

According to a preferred embodiment, the heating means for heating the treatment chamber is provided as a heating board, and/or the transportation means is provided as a convection fan. These means are highly reliable and can be maintained in a cost effective manner. Especially the heating board can be at least in part permeable, so that heat (for example hot gas) generated by the heating board can easily be transported towards the component to be cleaned by means of e.g. a convection fan. Expediently, an exhaust port is provided in the treatment chamber, through which inert gas blown into the chamber and/or solder/flux removed from the component to be cleaned, especially the diffuser, can be removed from the treatment chamber. According to a preferred embodiment of the inventive device, the transportation means, the heating device and the holding means are arranged in such a way that heat generated by the heating means is transported towards a component to be cleaned, especially a diffuser, held by the holding means. This arrangement provides a highly effective device and method for cleaning components exposed to solder and/or flux.

According to a preferred embodiment of the method of the invention, the temperature generated in the treatment chamber initially ramps up to a predetermined temperature substantially lower than a sintering temperature of the component located in the treatment chamber, especially to a temperature of about 400°- 600 'Ό, is then maintained at the predetermined temperature for a predetermined time, and is then ramped down to a temperature, at which the component located in a treatment chamber can be removed, preferably a temperature, at which the component can be manually removed from the treatment chamber, for example room temperature. Preferably, the predetermined temperature is maintained for about three to ten minutes, preferably four to six minutes, more preferably five minutes.

Further advantages and embodiments of the invention will become apparent from the description and the appended figures.

It should be noted that the previously mentioned features and the features to be further described in the following are usable not only in the respectively indicated combinations, but also in further combinations or taken alone, without departing from the scope of the present invention.

The invention is explained hereinafter in detail with reference to the appended figures. In the drawings: Figure 1 shows a schematic side view of a preferred embodiment of the device according to the invention, and

Figure 2 shows a diagram indicating temperatures and nitrogen flow generated during performance of the method according to the invention.

In figure 1 , a preferred embodiment of a device according to the invention is generally designated 100. The device 100 comprises a treatment chamber 102. This treatment chamber comprises at least one opening 104, in which a tube connector 106, constituting a holding means, is inserted. Component 106 is referred to a tube connector because it serves to hold a diffuser typically provided as a porous tube, according to the illustrated embodiment of the invention. A door, through which components to be cleaned can be inserted into and removed from the treatment chamber is not explicitly shown. Nitrogen or another expedient inert gas can be blown into the treatment chamber 102 through the tube connector 106, as will be described further in the following.

Within the treatment chamber, there is provided at least one heating board 1 10 constituting a heating means.

Furthermore, the treatment chamber 102 is provided with at least one convection fan 1 12, serving as transportation means for transporting heat within the treatment chamber 102.

The heating board 1 10 and the convection fan 1 12 are arranged in such a way, that heat generated by the heating board can be transported towards the tube connector 106 and an element held by the tube connector, for example a tube-like diffuser 120. The diffuser will typically be provided as a porous tube made of a metal or metal alloy powders, for example stainless steel, with a sintering temperature of about I SOO'C.

For reasons of simplicity, only one tube connector 106 holding one diffuser 120 is shown in figure 1 . Obviously it is possible to construct a tube holder to hold a number of diffusers or other elements to be cleaned within the treatment chamber. As immediately follows from figure 1 , nitrogen blown through the tube connector 106 (indicated by arrow 108) will also be blown through the diffuser 120 whereby a positive pressure relative to the surrounding parts of the treatment chamber can be maintained within the diffuser 120.

In order to be able to discharge nitrogen blown into the treatment chamber 102, the treatment chamber is provided with an exhaust port 1 14. The heat generated by the heating board 1 10 is transported towards the diffuser 120 by means of the convection fan 1 12, as mentioned. This heat, in combination with the nitrogen flowing though the diffuser 120, provides an effective cleaning of the diffuser 120, as will be explained in the following: When a diffuser to be cleaned is inserted into the treatment chamber 102, the temperature within the treatment chamber is typically room temperature. During a first phase 202, as shown in figure 2, the temperature within the treatment chamber 102 is ramped up to a desired predetermined temperature, typically somewhere within the region of 400-600 This temperature is chosen so that it is substantially lower than the sintering temperature of the diffuser (porous tube) to be cleaned, which typically lies around 1 .300 'Ό. This desired temperature is maintained over a second period 204, after which it is ramped down, typically back to room temperature, in a third period 206.

In some cases there can be a slight occurrence of metal oxidation contamination on the tube surface. In these cases, pre-treatment with hydrogen can be applied for reduction after the period 202 and before the period 204.

During the second period 204, nitrogen is blown through the tube connector 106 and the diffuser, as indicated by step function 208.

Typically, the second phase 204 has a duration of about five minutes. At said desired (predetermined) temperatures, solder particles as well as flux contaminating the diffuser 120 will drop off the diffuser, since no wetting occurs between the (tin alloy) solder and (stainless steel) diffuser. Also, flux decomposes at these temperatures. By providing a sufficiently large nitrogen flow during this phase, both contaminations (solder and flux) are effectively blown off the diffuser, and can be discharged through the exhaust port together with the nitrogen.

During the third phase 206, the temperature of the treatment chamber 102 and the diffuser 120 located therein is typically brought back down to room temperature, so that the diffuser can be manually removed from the treatment chamber 102.

If necessary or desired, additional washing and drying steps can be performed. In order to provide an automated functioning of the method as described, the treatment chamber can be provided with thermal detection and control systems.