JPH05152723A - Method of drying thick-film paste - Google Patents

Abstract

PURPOSE: To provide a method of drying a solvent-containing thick paste film applied onto a steel hybrid circuit board which is used for an electronic circuit, wherein solvent contained in the thick paste film is easily evaporated without inducing voids or cracks in the film. CONSTITUTION: A thick paste film 12 is applied onto a circuit board 10, and the circuit board 10 is exposed to a high-frequency alternating magnetic field 16 generated from a coil 14, where an alternating voltage is applied before it is fired or baked, whereby an eddy current is induced inside the circuit board 10. The eddy current generates heat to dry up the thick paste film, and the thick paste film 12 is heated from below to evaporate a solvent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal core wiring board for an electronic circuit, particularly a steel hybrid circuit board using a material having a magnetic element represented by iron as a metal core. It relates to a method of drying a thick film paste containing a solvent applied thereon.

[0002]

BACKGROUND OF THE INVENTION It is known to apply a thick film paste to a steel hybrid substrate or support to make SMD (Surface Mount Device) electronic circuits. Usually this is done by printing a thick film paste containing a solvent onto a steel hybrid plate or substrate, for example by a screen printing process. Before these thick film pastes are baked or baked in a normal oven, it is necessary to pre-dry the thick film pastes in a conventional drying oven to evaporate the solvent.

[0003]

Conventionally, heating a circuit board plate provided with a thick film paste to a desired temperature is accomplished by an infrared or similar heat radiator directed at the printing surface of the plate. Was there. However, this unfavorable heating from above leads to an undesirably fast drying of the surface of the paste, forming a crust and impeding the escape of solvent gas bubbles from the interior of the paste. Other drawbacks are then the presence of inconvenient void formation in the paste, or when relatively small gas bubbles are present over the already dried surface of the thick film paste, the relatively small gas bubbles become relatively small. To combine in large gas bubbles to create unwanted cracks and craters.

The object of the present invention therefore makes it possible, before the actual firing step, to dry the treated thick film paste on a steel hybrid support for circuit boards in a simple manner, that is to say the thick film paste. It is possible to evaporate the solvent contained therein without generating voids or cracks in the thick film paste.

[0005]

This object is achieved according to the invention by a method of drying a thick film paste containing a solvent and applied to a steel hybrid support substrate for a circuit board. The method comprises exposing a steel hybrid circuit board comprising an applied thick film paste to an alternating high frequency magnetic field prior to firing or baking the paste.

A particular advantage of the method according to the invention is that the steel hybrid circuit board is exposed to an alternating high frequency magnetic field in order to dry the applied thick film paste. This alternating high-frequency magnetic field induces a voltage in the steel hybrid circuit board or plate, which causes a short-circuit current in the plate, thus heating the plate by resistance heating and creating pores and cracks in the paste, respectively. Evaporate the solvent uniformly without forming.

The method according to the invention has proved to be advantageous at a given frequency, for example of the order of 10 KHz, and can be easily changed to about 150 ° C. by varying the amplitude of the alternating high frequency (HF) magnetic field. Heat the steel hybrid circuit board to the desired temperature up to temperature.
In actual tests, this temperature proved to be particularly suitable for predrying.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows that a substrate 12 of a steel hybrid circuit board, a supporting substrate or a plate 10 has already been coated with a coating 12 of a thick film paste containing a solvent. Before the coating 12 is fired or baked in a furnace, the support substrate 10 of the circuit board is exposed according to the invention to an alternating high frequency magnetic field, the magnetic field lines of which are indicated here by reference numeral 16. As shown in FIG. 1, this alternating high frequency magnetic field is generated in the usual way, for example in coil 14 by the application of an alternating voltage U.

The alternating high-frequency magnetic field causes magnetic field lines 16 of the magnetic field to penetrate the supporting substrate 10 of the steel hybrid circuit board, so that an eddy current is generated in the circuit board 10, so to speak, a desired temperature is generated from the inside thereof. To heat the circuit board.

FIG. 2 shows a steel hybrid circuit board 1
10 shows another arrangement using the method according to the invention for drying the coating 12 on the 0. Here, the coil 14 is
It is applied to a magnetic yoke or core 18 having an air gap formed between pole pieces 20 and 22. After applying the alternating high-frequency voltage U to the coil 14, the alternating high-frequency magnetic field formed between the pole pieces 20 and 22 is again shown here by the magnetic field lines 16, but in the steel hybrid circuit board 10 the aforementioned vortex It causes the generation of an electric current, which leads to the heating of the circuit board.

For the method according to the invention shown in FIGS. 1 and 2, the configuration for use is a typical example.
If the coated steel hybrid circuit board 10 is exposed to an alternating high frequency magnetic field to generate the desired eddy currents in the circuit board and generate heat to dry the thick film paste 12, the invention Other arrangements are also envisioned without limiting the scope. Therefore, the placement of the coil 14 is self-evident (like the example shown in FIG. 1) whether the coil is placed above or on the side of the steel hybrid circuit board 10.

By changing the amplitude of the alternating voltage U applied to the coil 14, the amplitude of the alternating magnetic field can be changed.
, The magnitude of the induced eddy currents can be easily changed and can be easily set to the desired heating temperature of the circuit board 10, preferably around 150 ° C. As indicated above, due to the alternating magnetic field, for example, about 10K
The frequency of Hz has been found to be particularly effective.

Further, the circuit board heated by the method of the present invention is exposed to an alternating high frequency magnetic field to generate a desired eddy current in the circuit board and generate heat for drying the thick film paste. If so, it is obvious that a steel hybrid circuit board made of any material is possible.

Because of this ease and effectiveness, the method according to the invention is suitable for the integration of automated processes for printed steel hybrid circuit boards and is used in the input of conventional baking furnaces by an easy method. It is also possible.

While the invention is described herein, it will be apparent to those of ordinary skill in the art that any modifications and variations can be made without departing from the spirit or scope of the invention described herein. .

[Brief description of drawings]

FIG. 1 illustrates an example arrangement for implementing the invention.

FIG. 2 shows an arrangement of another embodiment for carrying out the present invention.

[Explanation of symbols]

 10 ... Steel hybrid circuit board 12 ... Coating 14 ... Coil 16 ... Magnetic field line 18 ... Magnetic core 20, 22 ... Pole piece

Front Page Continuation (72) Inventor Peter Sommer 5020 Frechen 4, Siyubal Bembek 31 Be, Germany

Claims (7)

[Claims] 1. A method of drying a treated solvent-containing thick film paste on a steel hybrid circuit board for an electronic circuit before the thick film paste is fired in a furnace, the thick film paste comprising: A method of drying a thick film paste, which comprises the step of exposing the steel hybrid circuit board coated on to an alternating high frequency magnetic field for heating the circuit board. 2. The alternating high frequency magnetic field is about 10 KHz.
The drying method according to claim 1, which has a frequency of. 3. The method according to claim 2, wherein the exposing step includes the step of adjusting the amplitude of the alternating high frequency magnetic field so that the circuit board is heated to a temperature of about 150 ° C. 4. A step of applying a thick film paste containing a solvent onto a steel hybrid substrate, a step of heating the substrate having the applied thick film paste to dry the solvent, and then the thick film. In a method of manufacturing a circuit board, which comprises a step of firing a paste in a furnace, the step of heating to dry the solvent, the substrate containing a thick film paste containing the solvent is applied in an alternating magnetic field of high frequency. Arranging, thereby generating an eddy current in the steel hybrid substrate. 5. The method of claim 4, wherein the high frequency is approximately 10 KHz. 6. The method of claim 5, wherein the heating step includes adjusting the amplitude of the high frequency alternating magnetic field to heat the circuit board to a temperature of about 150 ° C. 7. The method of claim 4, wherein the heating step comprises adjusting the amplitude of the high frequency alternating magnetic field so that the circuit board is heated to a temperature of about 150 ° C.