Linear via punch

Details Linear via punch Linear via punch

1997-03-12

2003-09-23

Dexter, Clark F. (Department: 3724)

Cutting

With work immobilizer

Means to clamp work

C083S553000, C083S588000, C083S620000, C083S637000, C083S687000, C083S929100

Reexamination Certificate

active

06622603

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to the formation of holes in a substrate material, typically an unfired, ceramic “greensheet,” for the purpose of fabricating electronic circuit components which are ultimately used in the manufacture of electronic devices such as computers or the like.
BACKGROUND OF THE INVENTION
Circuit boards with multiple VLSI circuit chips are called Multichip Modules (MCM). The use of VLSI circuits presents interface problems relating to the interconnection of the integrated circuits to other circuits and the placement of the integrated circuits on a ceramic circuit board (MCM-C). As VLSI technology has advanced, the density of circuits on a single VLSI chip has increased and the necessary interconnection for VLSI chips has become increasingly difficult to achieve in a limited space. An MCM-C design object is to increase the ratio of the total area occupied by silicon to the total board area, called silicon efficiency ratio. The MCM-C packaging limits the speed and size of a system. Because the physical interconnection is a limiting design factor, a way to accommodate more circuit interconnections is necessary.
In a typical configuration, semiconductor chips are mounted in cavities on multilayer circuit boards and the circuit boards accommodate intercircuit connections through tiny vertical holes or vias between the layers. The chips are connected to the vias using a controlled-collapsed-chip-connection technique called C-4. The vias are filled with a conductive material, such as molybdenum paste, which creates a connection to the VLSI circuit. The size of the holes dictates the size of the connection and the number of connections that can be placed on the multilayer circuit board.
There are a number of methods for creating small holes in precision tooling to facilitate the punching of vias. Such methods include dry or laser cutting and electrical discharge machining (EDM). The precision tooling of each of these methods facilitates the punching of vias as small as 0.01778 cm (0.007 in.) in dielectric material as thin as 0.00762 cm (0.003 in.). The precision tooling is used in a master punch and die assembly.
In the precision punching method, each precision via hole is punched in a workplace or substrate using precision tooling which includes a precision punch assembly and a precision die assembly. The punches of the precision tooling device are guided by precision holes in one or more precision plates. The cutting edge of the die plate is formed by precision openings in the die plate. The precision of the tooling is the limiting factor in providing a precision punch substrate. Prior art is directed to the precision necessary to create the smallest possible precision holes in a substrate.
The vias necessary to create the circuit interconnection have previously been created by a punch and die device which is fabricated by making a die mask or plate using EDM. The plate is fabricated from 0.127 cm (0.050 in.) tool steel. Precision holes as small as 0.1651 cm (0.0065 in.) are burned through two plates at one time by EDM at a rate of 6 holes per hour. The plates are then used in a precision tooling device. The size of the substrate hole punched by the precision tooling is limited by the size of the smallest plate opening which can be created by EDM, namely 0.01651 cm (0.0065 in.). The EDM plate facilitates punching holes with an accuracy of 0.00762 cm (0.003 in.) true position. These tool steel plates are heavy, expensive, and require sharpening. The sharpening consumes time and can only be done several times before the die must be replaced due to wear.
A method for producing precision dies is disclosed in co-pending U.S. patent application Ser. No. 08/660,611 filed Jun. 6, 1996 and titled “Precision Punch and Die and Construction.” The copending application is incorporated herein by reference.
Numerous types of punching devices are found in the prior art. For example, U.S. Pat. No. 4,821,614 describes a punch apparatus with a single punch element and a programmable apparatus to selectively move a carriage which supports the sheet of material being punched. Another punch apparatus with a single element is described in U.S. Pat. No. 4,872,381. IBM Technical Disclosure Bulletin, Vol. 20, No. 4, September 1977, pages 1379-80, discusses a punch apparatus with a plurality of individually activated, programmable, punching elements. The substrate to be punched is supported by a movable table. IBM TDB, Vol. 26, No. 10A, March, 1984, pages 5100-02, describes a mechanical punch with a dense array of punches which is electromechanically affixed to a platen which is driven downward at the appropriate time causing a push rod and punch carrier to be driven down. Simultaneously, a punch is driven down, thereby piercing the substrate material. IBM TDB, Vol. 30, No. 6, November, 1987, pages 355-58, describes a punching apparatus in which a single punch is used to form vias in the substrate by performing punching with the substrate moving at a constant velocity (“on the fly”). IBM TDB, Vol. 31, No. 9, February, 1989, pages 140-41, discusses a flexpunch machine which uses a punch and die assembly to produce the entire via pattern in the substrate. The punch and die assembly moves at a constant rate while punching the substrate.
Another conventional alternative to a single punch machine is to have an array of equally spaced punches mounted on a bar spanning the width of the substrate being punched and perpendicular to the direction of the movement of the substrate. With this arrangement, the substrate is moved in the direction of the Y-axis and the punches are fired simultaneously as needed. If the spacing of the punches exceeds the grid size of the holes, and if the ratio of grid size to punch spacing is an integer, then the number of passes of the substrate required to complete the punching task is equal to this ratio. For each pass of the substrate, the material is indexed one grid unit along the X-axis and a discrete indexing device for incremental movement of the substrate along the X-axis is required. Further, due to physical size requirements and electric power usage, the simultaneous firing of the punches on the array requires an independent power supply for each punch. The drawbacks of this system include the power supply problems and the requirement that a discrete indexing device, movable in the X direction, be provided.
None of the aforementioned references utilize a punch head having a fixed partial via pattern corresponding to a line of ups which is created from a via fill mask, to perforate a substrate which is supported by a precision die which is also created from the via fill mask having a full array pattern of vias. A problem exists with punching a constantly moving substrate because the punch speed must be extremely high with respect to the substrate speed in order to avoid any distortion such as ripping, tearing, or the like. Conventional systems which punch “on the fly” must use an extremely large power supply to obtain the necessary punch speed relative to the substrate speed. The need for a large power supply for each punch in an array is impractical because large power supplies have correspondingly large physical size and electric power requirements which limit their use to a single punch or a die set having several plural punches affixed to it.
A conventional system includes cluster punches and cluster dies which are used to punch vias with both being moved together about the surface of the substrate punching a single pattern of holes (ups) multiple times, as required, in the substrate. An illustration of such a prior art system is shown in FIG.
5
. In
FIG. 5
punch and die assembly
62
is positioned to sandwich greensheet
60
. A single pattern is punched in one operation. Also illustrated are positioning system
92
, hole verifier
94
, and controller
96
. The drawback in this system is that the punch and die assembly is subject to alignment errors with respect to the substrate and that, as the number of holes require

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