Coating processes – Electrical product produced – Integrated circuit – printed circuit – or circuit board
Patent
1983-06-23
1984-11-27
Lusignan, Michael R.
Coating processes
Electrical product produced
Integrated circuit, printed circuit, or circuit board
427125, 118205, 118254, B05D 512, B05C 100
Patent
active
044851294
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
The invention is based on a method of through-contacting a circuit board in which the wall of a bore is provided with an electrically conductive coating. A through-contacted circuit board of this kind is known, for instance from German Patent Disclosure Document DE-OS No. 2 920 091, wherein it is explained that the roughened side wall of a bore is provided with a metallizing. A metallizing of this kind is applied in a known manner by means of cathodic sputtering and then is galvanically reinforced.
Other known methods for producing electrically conductive coatings on a surface are performed with rollon or brush-on methods. Screen-printing methods are also known for applying electrically conductive films.
A method is furthermore known from German Patent Disclosure Document DE-OS No. 3 014877 for coating an exhaust oxygen sensor electrode (lambda sensor), in which an electrically conductive liquid is introduced in a metered manner into a hollow body and distributed in the hollow body by means of an inflatable, finger-like part. Finally, electrically conductive pastes of the type under discussion are known, for instance from German Patent Disclosure Documents DE-OS No. 29 13 633 and DE-OS No. 30 02 112. Of the known conductive pastes, those having a high precious-metal content, preferably including silver, are particularly well suited for applying the through-contacting film according to the invention. Suitable conductive pastes are furthermore available in commerce from the Du Pont de Nemours company in the U. S. or in Dusseldorf, Federal Republic of Germany, an example being an AgPd paste having the code number 9473. This paste can be mixed as needed with a thinner sold by the same company and having the code number 9180. A suitable silver paste is sold under the code number 1110S by the ESL company in Pennsauken, N.J., for example.
ADVANTAGES OF THE INVENTION
The method according to the invention and having the coating effected by imprinting an electrically conductive past by means of an elastically deformable printing stamp makes it possible, in a particularly advantageous manner, to coat round or otherwise-shaped bores in circuit boards uniformly while dispensing the paste to be applied in a precisely metered manner. The proposed method is extremely economical when compared with previously conventional methods, since such expensive manufacturing techniques as vacuum processes are dispensed with. Because the pastes to be applied can be metered exactly, substantial savings in cost can be realized because of the savings in expensive precious metals.
As a result of the use of a printing block, backing support, and silver or silver-palladium paste, advantageous further developments of and improvements to the method disclosed in the main claim are possible. Imprinting the paste by means of a sharply pointed stamp, in particular, assures a complete coating and uniform application of the paste in the bore, because an imprinting stamp of this kind adapts itself particularly well to the inside contour of a bore. Picking up the printing paste from a flat printing block has the advantage that introducing the printing paste into the depression of the printing block can be accomplished particularly easily, for instance by brushing it on. The depth to which the printing block is etched is preferably on the order of 35 to 120 .mu.m. Particularly in the through-contacting of bores the diameter of which is small in proportion to the thickness of the circuit board, the use of a backing support has proved useful in order to press the elastically deformable imprinting stamp, with the paste to be applied, reliably against the entire surface of the bore. In bores of relatively slight depth, this backing support can be dispensed with at no disadvantage.
DRAWING
One exemplary embodiment of the invention is shown schematically in the drawing and explained in further detail in the following description. Shown are:
FIG. 1, the pickup of the conductive paste from a printing block by an elastically deformable
REFERENCES:
patent: 3301175 (1967-01-01), Polichette
patent: 3605616 (1971-09-01), Pannier
patent: 3701317 (1972-10-01), Miyamoto et al.
IBM Technical Disclosure Bulletin, vol. 21, No. 9, (Feb. 1979).
Grunwald Werner
Schmid Kurt
Jaconetty K. E.
Lusignan Michael R.
Robert & Bosch GmbH
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