Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1998-05-13
2001-11-27
Thompson, Gregory (Department: 2835)
Metal working
Method of mechanical manufacture
Electrical device making
C029S846000, C428S901000
Reexamination Certificate
active
06321443
ABSTRACT:
The invention is in the field of the manufacture of printed circuit boards and more particularly relates to multilayer, electrical and optical connecting substrates having multiple functions and a method for the manufacture thereof as a whole or the starting and intermediate products thereof.
Printed circuit boards are nowadays ever more complex electromechanical and even opto-electromechanical multilayer structures, during whose development and manufacture it is necessary to fulfil a number of functions, which can be subdivided into primary and secondary functions.
Primary functions e.g. relate to the presence of signal conductors to the components and the power supply of said components. It also relates to the provision of a mechanically manipulatable support or carrier structure with suitable assembly or mounting faces for components to be loaded and standardized interfaces for connection to other system parts.
Secondary functions e.g. relate to the electromagnetic shielding of the printed circuit board and to the integration of passive electrical components such as resistors, capacitors, inductance coils and passive optical components such as waveguides, splitters, combiners, mirrors, into the actual connecting substrate. They relate to mechanical functions such as the adaptation of the temperature coefficient of the support structure to the components. In addition, flexible connecting elements can be integrated into the connecting substrate. They also relate to thermal functions, such as passive or active cooling and heat management, i.e. heat distribution or dissipation.
Hereinafter are described disadvantages of conventional multilayer structure from the standpoint of the primary and secondary functions.
Undifferentiated mixing of the functions: nowadays primary and secondary functions, as enumerated hereinbefore, are “merged” into a unit. Such an undifferentiated multilayer structure is e.g. disclosed in FR-2,117,172 and U.S. Pat. No. 4,830,691. In such multilayer structures signal conductors and power supply conductors are embedded in a dielectric serving as a mechanical support. Components are connected by layers of signal conductors and power supply conductors. Several such layers are interconnected by means of interfacial connections, which pass through several planes. It is disadvantageous that the relatively long and therefore necessarily large diameter through holes have to pass through the entire multilayer structure. It is also disadvantageous that the interfacial connections often have to pierce electrically conductive planes, which makes necessary additional precautions against short-circuits.
Complexity of the undifferentiated mixing: modern integrated circuits are ever more complex with respect to their functions and are used in ever larger numbers on printed circuit boards. In addition, the switching frequencies are rising. This leads to high layer, densely wired multilayer structures, which simultaneously must dissipate high power losses. This high heat production requires additional heat conducting elements, whose thermal interfacial connections take up wiring space, whose layout additionally increases the complexity of the multilayer structures, which may give rise to compatibility problems. With such “merged” units, modifications and redesign can lead to project delays. It is also disadvantageous that it is difficult or even impossible to pretest the inner wiring planes of the multilayer structures, which gives rise to a reduced efficiency risk.
Miniaturization: miniaturization is no longer limited to the smallest dimensions of conductor spacings in integrated circuits and instead applies to the actual equipment. Pocket televisions, portable personal computers (laptops to palmtops), hand cameras and other highly complex equipment necessarily require connecting substrates with small dimensions. It is therefore necessary to adapt the shape and design of the connecting substrates to the equipment shapes. Suitable for this purpose are flexible, particularly rigid-flexible connecting substrates with flexible connectors, such as flexible extension arms and interfaces. It is known that the manufacture of rigid-flexible connecting substrates according to conventional methods is complicated and expensive.
Heat dissipation and waste heat control: nowadays the heat dissipation generally takes place by introduction via heat conducting materials into the multilayer structure. Such a heat dissipating multilayer structure is e.g. disclosed in EP-451,541. In the interior of the multilayer structure the heat is passed via heat conducting materials and over relatively large distances to the border or edge of the multilayer structure. In order to solve this thermal problem, it is necessary to have galvanic interfacial connections, whose task is merely to direct the heat into and then out of the connecting substrate.
The problem of the present invention is to seek a solution with which it is possible to fundamentally avoid the disadvantages of the necessarily increasing complexity of modern connecting substrates. The invention provides a multilayer structure with high density connecting networks, which allows a good heat management, whose components are connected by means of very short signal conductors, whose electrical or optical circuit can be pretested and where the rigid-flexible portions can be easily produced with different hardnesses and bending radii. However, it must be possible to use in preferred manner known, proven methods, materials, etc. For example, for the production of the conductor structures, it must be possible to use known wet chemical and etching methods. The further processing, particularly the loading and contacting, must be compatible with known systems, e.g. soldering, wire bonding, etc.
The set problem is solved by the invention defined in the claims.
The idea according to the invention is based on functional analysis or, in other words, the differentiation of a functionally separated structural principle of functions such as “power supply”, “signal conductor”, “mechanical support”, “assembly faces”, “heat sinks”, “flexible connectors” and “interfaces to the exterior”.
This analysis shows that the observed complexity of modern connecting substrates can essentially be reduced to the interaction of two characteristics, namely the interaction of the functional complexity with the structural complexity.
Functional complexity and structural complexity are proportional to one another and in each case comprise three basic characteristics, which electrical and/or optical connecting substrates have to fulfil, namely signal switching, thermal and mechanical characteristics. The denser the desired signal switching, functional complexity (high data throughout) is to be, the higher the requirements made on the signal switching, structural complexity (conductor and component density) of the connecting substrate. The higher the resulting thermal, functional complexity (heat densities and gradients), the more effective must be the thermal, structural complexity (thermal layout, heat sinks) of the connecting substrates. The higher the mechanical, functional complexity (hardnesses, bending radii and stiffnesses) as a local function on the connecting substrates, the higher the demands made on the mechanical, structural complexity (rigid-flexible areas, local stiffness, etc.) of the connecting substrate.
The presently worked out, proportional interconnection between the functional complexity and structural complexity, as well as the minimum set of necessary characteristics, here the signal switching, thermal and mechanical characteristics, covers and completely describes the functions for the purpose of a functionally separated design of a connecting substrate.
From the standpoint of the functional and structural complexity and their characteristics, the set problem of the invention can be reworded. In a first approximation signal switching, thermal and mechanical characteristics of the structural complexity of connecting substrates to be manufactured can be co
Barte Hans-Jürg
Losert Ewald
Meyer Heinrich
Röhrs Günter
Rudolf Frank
Dyconex Patente AG
Rankin, Hill Porter & Clark LLP
Thompson Gregory
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