Continuous furnace

Details Continuous furnace Continuous furnace

1991-01-10

1993-04-06

Yuen, Henry C.

Heating

Advancing structure flexing, looping or coiling sheet, web...

432 5, 432 8, 34105, F27B 928

Patent

active

051998688

DESCRIPTION:

BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national phase of PCT/DE/90/00376 filed May 22, 1990 and based upon German National Application P 39 16 922.7 filed May 24, 1989 under the International Convention.


FIELD OF THE INVENTION

The invention relates to a continuous furnace for the simultaneous two-sided sintering of sintered layers upon substrates, particularly for producing thick-film integrated circuits, the furnace having a muffle and a drivable conveyor belt supporting the substrates and longitudinally traversing the muffle, this belt being endlessly led back outside the muffle.


BACKGROUND OF THE INVENTION

In the known continuous furnaces of this kind, the conveyor belt forms in the muffle a plane support surface for the substrates. Because quality can be compromised during sintering due to the surface contact between the sintered layers and the conveyor belt, specially designed carrier devices are required for the substrates, which hold the substrates at the edges freely suspended above the conveyor belt. This permits this way making sintering without surface contact even for bottom-side layers. However, the disadvantages of these carrier devices are considerable, since the format can vary only within very narrow limits. The carriers are also partially exposed to heavy wear by high temperatures. The mass of the carrier can influence the sintering temperature profile or the temperature buildup time, and they cannot be operated with the usual automatic substrate loading systems.


OBJECT OF THE INVENTION

It is an object of the invention to provide an improved continuous furnace of the aforementioned kind, so that in the case of two-sided substrate coating, the sintering process can be carried out just like in the case of one-sided coating of substrates, thus preserving for the two-sided substrate coating process the advantages of the known sintering process for one-sided coating of substrates, such as format flexibility, elimination of carrier devices and the use of standard substrate loading systems.


SUMMARY OF THE INVENTION

This object is attained in accordance with the invention by providing the mutually facing inner edges of the individual belts are so that they run lower than the outer edges facing away from each other The substrates which are self-supporting between two parallel lateral edges lie with one lateral edge on the belt surface of one of the individual belts and with the other lateral edge on the belt surface of the other individual belt.
As a result, the individual belts with their inclined belt surfaces, when seen in cross section, form an approximately V-shaped opening angle, so that the substrates rest only with their lateral edges on the individual belts and remain untouched at their bottom coating side. The self-supporting arrangement of the substrates includes the possibility of separate process gas flows for the top side of the substrate and for its bottom side. The possibility of simultaneous two-sided sintering of coatings on a substrate reduces the production costs almost by one half. Furthermore, other cost advantages result from the possibility to process substrate sizes over a wider range and from the elimination of the carrier devices The automatic loading and unloading of the conveyor belt from and into storage can be rationally performed by already existing and proven devices.
Suitably, both individual belts are inclined with respect to the horizontal by equal angles, so that they form a symmetric arrangement with respect to the vertical median when, in addition thereto, the two individual belts have the same width. The inclined belt surfaces of the two individual belts can define between them an opening angle between 80.degree. and 170.degree..
Preferably, in the muffle, the inclined belt surfaces of both individual belts each constitute a plane surface. In a further preferred embodiment, the muffle has mutually inclined muffle bottoms, just like the mutually inclined belt surfaces of the individual belts, the individual belts being supp

REFERENCES:
patent: 3711961 (1973-01-01), Spiegel et al.
patent: 3779696 (1973-12-01), Poore et al.
patent: 4065251 (1977-12-01), Croft et al.
patent: 4080158 (1978-03-01), Kondo et al.
patent: 4408986 (1983-10-01), Soraya et al.

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