Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1998-08-04
2001-06-05
Huson, Gregory L. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S593000, C029S025420, C361S304000
Reexamination Certificate
active
06240621
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method of manufacturing a plurality of thin-film, surface-mountable, electronic components. Examples of such components include resistors, capacitors, inductors and fuses, but also passive networks, such as RC and LCR networks.
Such a method is known, for example, from U.S. Pat. No. 4,453,199, which relates specifically to the manufacture of a plurality of thin-film capacitors. The method therein described employs a glass plate as a substrate. Using masking techniques, an orthogonal matrix of discrete, thin-film electrode structures is provided on a major surface of this plate, with the aid of a sputtering or evaporation procedure, for example. Each such electrode structure comprises a bottom and top electrode layer, which are separated by an interposed insulator layer, the electrode layers being offset in such a manner that they only partially overlap one another. After provision of the electrode structures, the plate is cut into strips, each such strip carrying a linear array of electrode structures. Each strip is cut in such a manner that the bottom electrodes all terminate at a first long edge of the strip, but not at the oppositely situated second long edge, whereas the top electrodes all terminate at the second long edge of the strip, but not at the oppositely situated first long edge. Each strip is then provided with an electrical contact along its first and second long edges, using a technique such as sputter-coating. Once these contacts have been provided, the strip is cut into individual block-shaped components, each comprising an electrode structure and two electrical contacts.
The method described above has a serious disadvantage, in that the plate must be cut into strips before the electrical contacts can be provided. This is undesirable, because it means that the manufacturing process cannot be completed at plate level (being the most efficient and economic mass-production scenario), and must instead be completed on a relatively piecemeal basis using sub-units of the original substrate plate (which is more time consuming, and therefore expensive).
SUMMARY OF THE INVENTION
It is an object of the invention to alleviate this drawback. In particular, it is an object of the invention to provide an economic and efficient method of manufacturing a plurality of electronic components. More specifically, it is an object of the invention to provide a component-manufacturing method which allows the entire component to be completed at plate level, before the substrate is severed.
These and other objects are achieved according to the invention in a method as specified in the opening paragraph, characterized in that it comprises the following successive steps:
a) providing a substantially planar ceramic substrate having a first and second major surface which are mutually parallel, the substrate containing a series of mutually parallel slots which extend from the first major surface through to the second major surface, such slots serving to subdivide the substrate into elongated segments extending parallel to the slots and located between consecutive pairs thereof, each segment having two oppositely located walls extending along the edges of the adjacent slots, each segment carrying a thin-film electrode structure on at least one of its first and second major surfaces;
b) with the aid of a lithographic technique, providing electrical contacts which extend along both walls of each segment and which make electrical contact with the electrode structure on each segment;
c) severing the segments into individual block-shaped components by severing them along a series of lines extending substantially perpendicular to the longitudinal direction of each segment.
The method according to the invention employs a number of special techniques to achieve the goals stated above. In particular, the ceramic substrate in step (a) is subdivided into strip-like segments (which remain attached to one another) before provision of the electrical contacts, but is only actually severed into loose block-like components (which are fully separated from one another) after provision of the electrical contacts. Such subdivision allows the use of three-dimensional lithographic techniques to provide the electrical contacts on the exposed side walls of all the segments together (i.e. at plate level), without having to first physically sever the segments from one another (as in the prior art method). Such 3-D lithography will be discussed in more detail herebelow.
The term “ceramic” as employed throughout this text is intended to have a broad scope, and should be interpreted as including the following categories of (electrically insulating) materials:
Abrasives, such as alumina, silicon carbide and diamond;
Refractories, such as silica, quartz, aluminosilicate, magnesite and zirconia;
Vitreous materials, such as glass, glass ceramics and enamels;
Engineering ceramics, such as cermets and ceramic composites, together with various other oxides, carbides and nitrides.
In particular, the generic term “glass” includes various specific types of glass, such as soda glass, borosilicate glass, flint glass, quartz glass, etc.
Step (a) of the method according to the invention can be realized in different manners. On the one hand, the slots can be created in a ceramic plate before provision of the electrode structure. On the other hand, the electrode structure can be provided on a ceramic plate before creation of the slots.
A particular embodiment of the method according to the invention is characterized in that the slots in step (a) are formed by locally powder-blasting a continuous ceramic plate (on which the electrode structure may or may not already be present). This can, for example, be achieved by making a mask which contains apertures corresponding to the slots which are to be formed, and then powder-blasting the plate through the apertures until such time as the slots thus formed extend right through the plate. The mask thus used may, for example, take the form of a removable grid which is placed on the ceramic plate, or it may be a lithographic mask which is created on the surface of the ceramic plate by lamination, exposure and development of a curable resist.
An alternative embodiment to that in the previous paragraph is characterized in that the slots in step (a) are formed by:
attaching at least one rigid support strip across the width of a continuous ceramic plate (on which the electrode structure may or may not already be present);
cutting slots through the ceramic plate, which slots extend into, but not through, the support strip.
The cutting operation may be performed using a wire saw or laser beam, for example. In this embodiment, the integrity of the ceramic plate is maintained by the presence of the rigid support strip, which may be comprised of a material such as metal or ceramic, for example.
The inventive method lends itself to the manufacture of different types of component. For example:
(i) In a particular embodiment, the electrode structure in step (a) is comprised of a single thin film of conductive material which extends between both walls of each segment; the resulting component can then be employed as a thin-film resistor or fuse;
(ii) An alternative embodiment is characterized in that the electrode structure in step (a) successively comprises:
an underlayer of conductive material which extends to a first wall of each segment, but not the second wall;
a layer of insulating material which covers the underlayer;
an overlayer of conductive material which extends to the second wall of each segment, but not the first wall.
In this case, the resulting component can be employed as a thin-film capacitor. If so desired, it is possible to make a variant of this design, in which several layers of conductive materials are arranged in a stack in such a manner that alternate layers extend to alternate walls of each segment; in this manner, a multilayer capacitor is realized.
(iii) Another embodiment is characterized in that each component is a seriesconne
Nellissen Antonius J. M.
Van Grunsven Erik C. E.
Biren Steven R.
Huson Gregory L.
Trinh Minh
U.S. Philips Corporation
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