Silicon based lacquer, its use as a substrate coating and substr

Details Silicon based lacquer, its use as a substrate coating and substr Silicon based lacquer, its use as a substrate coating and substr

1995-02-13

1998-03-31

Dean, Ralph H.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From silicon reactant having at least one...

528 10, 427387, 427515, 428447, C08G 7704

Patent

active

057340005

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a novel silicon based lacquer, its use as a substrate coating, and the thus-obtained substrates.
Hitherto, studies and efforts have been made to obtain lacquers endowed with improved technical properties, to be used as coatings for substrates which are typically used in extremely harsh environments. Examples of coatings which allow the coated substrates to be used in said harsh environment are coatings with properties such as: anti-contamination, anti-scratch, heat-resistance and refractory properties, low moisture permeability, resistance to chemicals, insulation properties, oxygen-barrier, high bulk resistivity, low friction coefficient, high adhesion on the substrates and the like.
The fields wherein said coatings may be used are various and numerous. One can cite, as illustrative, those fields wherein the coatings are protecting for active and passive electric, electronic, optical components and assemblies thereof against environmental stresses.
During the past years, research in the field of microelectronics has been directed to higher productivity and devices miniaturisation. Thus, the use of surface-mounted devices (SMD), rendering high-speed component placement possible, has lead to significant gain in productivity, the soldering of such surface mounted devices (SMD) on the printed circuits now being carried out on the face(s) of the circuit where the devices are lodged. The two soldering processes currently used are wave soldering and reflow soldering. The first of these two processes, the so-called wave soldering process, comprises the step of bringing the printed circuit bearing the SMDs adhered thereon into contact with a stationary wave within a flowing molten solder bath, the parameters of temperature and time being respectively about 260.degree. C. and about 10 s. The second process, so-called reflow soldering comprises the step of applying solder in the solid state at the contact pins of the SMD adhered on the printed circuit board followed by heating, using IR radiation or vapor phase transfer, of the foregoing assembly at a temperature of about 220.degree. C. for a period of time of about 30 s. The component and the substrate are thus submitted to somewhat drastic thermal conditions, but they must of course retain their properties, especially electronic properties, i.e. the shift due to the thermal treatment should be less than a few percent, typically less than 3%.
Concurrently, efforts have been directed to miniaturise the components themselves and new components such as new capacitors, have been developed. These new capacitors known as thin-film capacitors are obtained by laminating thin layers of metal, e.g. aluminium, and thin layers of a bulk dielectric material, the electrode pins of this SMD being obtained by deposition of metal, e.g. aluminium. Good and promising results have been obtained with such capacitors, obtained from films made of polyester e.g. polyethyleneterephtalate (PET) or polyethylenenaphtalate (PEN) and which have been metallized. An example of a manufacturing process of said new capacitors is the process known as Interleaf.RTM.. Processes for preparing thin-film capacitors are described in the following U.S. Pat. Nos. 4,741,876, 4,744,462, 4,533,813, 4,535,381, 4,531,268, 4,534,488, and 4,531,340.
However, these new components, such as the above thin-film capacitors suffer from certain drawbacks. One is that polyester foils are known to absorb water. This water will cause corrosion and erosion of aluminium electrodes (the metal foils), and also a capacitance shift which occurs due to moisture content changes, meaning that during the above-mentioned soldering processes the rapid evaporation of water will tend to cause delamination.
These problems connected with water are cumulated with the low melting-point of the polyester. Therefore, the use of thin film capacitors as microelectronic SMD which can withstand the soldering processes requires encapsulation of these thin films. The encapsulating casing has to be endowed with insulati

REFERENCES:
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patent: 4243692 (1981-01-01), Scholze et al.
patent: 4374696 (1983-02-01), Schmidt et al.
patent: 4840666 (1989-06-01), Schmidt et al.
patent: 4944964 (1990-07-01), Schmidt et al.
patent: 5401528 (1995-03-01), Schmidt
English translation of JP-A-343407/1992; U.S. Pat. No. 5,401,528 is a counterpart to PCT/EP92/00604.

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