Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1997-12-31
2001-05-22
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S846000, C029S852000, C029S830000, C174S266000, C427S097100
Reexamination Certificate
active
06233820
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method for manufacturing a multilayer microwave board in which individual layers of plated laminate can be provided with a conductor pattern and in which, in a repeated process, individual layers or semimanufactures are subsequently bonded or provided with holes, which holes are then plated for realizing connections between the separate conductor patterns.
The invention also relates to a multilayer microwave board comprising a bonded package of laminate provided with conductors and plated layers and with connections between the conductors in the form of plated through-holes.
The invention furthermore relates to a method for tuning a multilayer board provided with blind or buried vias.
Both multilayer microwave boards and related manufacturing methods are well-known in the art. Nevertheless, their field of application is limited owing to the expensive and time-consuming production and the high ratio of rejects. Moreover, several restrictions apply, particularly with respect to the realization of connections between the various conductor patterns, the so-called vias. Various types of connections that are possible in the manufacturing of conventional multilayer printed circuit boards, cannot, or only at a high ratio of rejects, be realized. Especially the production of blind vias, buried vias and sequential blind vias presents difficulties and the manufacturing of interlocked vias is even considered to be impossible. Also microwave multilayers comprising more than three layers are practically non-existent.
SUMMARY OF THE INVENTION
The present method according to the invention is aimed at obviating these difficulties by the application of a simple and excellently reproducible method and is characterised in that the multilayer microwave board can be produced in one operation during which all layers are simultaneously bonded together to form a multilayer, which multilayer is subsequently provided with holes, which holes are then plated after which any excess plating is removed.
The multilayer microwave board according to the invention is characterised in that the holes penetrate the entire package and are at least substantially plated between the conductor patterns to be connected.
The method for tuning a multilayer microwave board manufactured according to a method well-known in the art is characterised in that after the actual production of the board a hole is drilled to at least one buried via in the board between a stripline and a plated hole, such that this connection is at least substantially ohmic in nature.
According to the known method, individual layers of plated laminate are provided with a conductor pattern and, where necessary, drilled after which the resulting holes are plated. These layers are then bonded under high pressure and temperature conditions. By repeatedly bonding the thus obtained semimanufactures and again drilling and plating the resulting holes, it is possible to realize more complex products.
Products realized on the basis of said known method are characterised by a high ratio of rejects, particularly since connections between the conductor pattern and plated holes fail at the high temperature and pressure required for the bonding process. This is particularly due to fluctuations in coefficients of expansion between metal parts and the laminate, although the high pressure and temperature also render the laminate viscous as a result of which any asymmetry surrounding a plated through-hole may cause a crack.
In the new, inventive method this problem is not experienced. It is further characterised in that the holes are provided by drilling right through the bonded package. Subsequently the holes are fully plated in a way known in the art after which any excess plating is mechanically removed, for instance by means of a drill.
A most favorable embodiment of the method is characterised in that a diameter of the drill is selected depending on the type of laminate and on the diameter of the plated hole in order to obtain optimized wave properties of the connection between the conductor pattern and the plating at that position. A favorable selection would for instance be a diameter of approximately 1.15 times the diameter of the plated hole.
A further favorable embodiment of the method is characterised in that the excess plating, depending on the type of laminate and the diameter of the plated hole, is removed in axial direction such that the wave properties of the connection between the conductor pattern and the plating at that position are optimized. It may then be effected that the connection at that position is at least substantially purely ohmic. A favorable implementation of this method, using a standard type of laminate of for instance {fraction (3/100)} inch is characterised in that a volume of excess plating is retained in axial direction at a length of 10-50 &mgr;m.
Since excess plating is mechanically removed in a multilayer microwave board according to the invention, the board is further characterised in that the holes, where the plating has been mechanically removed, have a larger diameter than the plated holes.
Depending on the type of laminate and the diameter of the plated hole, the larger diameter can be again selected such to yield favorable wave properties of the connection between the conductor pattern and the plating at that position, using a standard laminate of {fraction (3/100)} inch, for instance approximately 1.15 times the diameter of the plated hole.
A still further favorable embodiment of the multilayer microwave board according to the invention is furthermore characterised in that, depending on the type of laminate and the diameter of the plated hole, the plating between the conductor patterns to be connected extends at least slightly further in axial direction than merely the distance between these conductor patterns in order to obtain optimized wave properties of the connection at that position, for instance over 10-50 &mgr;m.
REFERENCES:
patent: 3895435 (1975-07-01), Turner et al.
patent: 4179800 (1979-12-01), Takaba et al.
patent: 4468414 (1984-08-01), Van Vonno
patent: 4916808 (1990-04-01), Sanborn et al.
patent: 4975142 (1990-12-01), Iannacone et al.
Chang Rick Kiltae
Hollandse Signaalapparaten B.V.
Oblon, Spivak, McClelland, Maier & Nuestadt, P.C.
Young Lee
LandOfFree
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