Plastic and nonmetallic article shaping or treating: processes – With severing – removing material from preform mechanically,... – Making hole or aperture in article
Reexamination Certificate
2002-07-22
2004-10-05
Ortiz, Angela (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With severing, removing material from preform mechanically,...
Making hole or aperture in article
C264S250000, C264S267000, C029S852000
Reexamination Certificate
active
06800232
ABSTRACT:
FIELD OF THE INVENTION
The field of the invention is the filling of electronic substrate vias and thru-holes.
BACKGROUND OF THE INVENTION
Electronic substrates such as printed wiring boards and interconnects often comprise plated vias and thru-holes. These holes (the terms “hole” and “holes” will often be used herein to refer to both vias and thru-holes if the text is applicable to both vias and thru-holes) are often filled with a conductive paste or other fill material, typically by forcing the material into the hole from one end of the hole. For the sake of this disclosure, the end of a hole through which fill material enters the hole will be referred to as the “entrance”, and the opposite end of the hole as the “exit”.
When filling holes, it is important that the exits of the holes not be in contact with any surface that will later be removed from the substrate before the fill material sets or cures. Thus, if one side of the substrate is resting on a tooling plate during the fill process, there should be some separation between the tooling plate and the exit of the hole in order to prevent material drag-out as the substrate is removed from the tooling plate.
However, such separation is not always easy to achieve. Substrates tend to be relatively flexible, and the filling process often exerts a downward force on the substrate. Thus, any mechanism used to provide the required separation must be adequate to maintain that separation while pressure is applied to the substrate. Providing proper separation is made more difficult because of the need to be able to handle a large number of different hole patterns as utilizing a single stand-off for multiple hole-patterns runs the risk of having portions of the stand-off intended to support the substrate positioned directly beneath a hole to be filled.
One method of supporting a substrate during filling is to provide a tooling plate or other support having thru-holes formed in it, placing the substrate to be filled on top of such a support in a manner that the holes to be filled align with thru-holes of the support, and filling the thru-holes. Examples of such supports and their use can be found in U.S. Pat. No. 6,276,055, U.S. Pat. No. 6,282,782, and GB2246912. Unfortunately, known supports tend to be inadequate in applications where a substrate comprises a larger number of holes having minimum separation between holes such as in a grid-array arrangement. In such an application, one might simply remove an entire area of the support corresponding to the area containing the holes, but doing so would leave that area of the substrate unsupported. Moreover, even if the support comprises individual holes rather than a removed area, there is a chance that the support will distort under the pressures applied during filling with a corresponding misalignment between the thru-holes of the support and the holes of the substrate. Known supports are often relatively expensive to manufacture as well.
Possible solutions utilizing etched tooling plates are the subject of co-pending U.S. patent applications Ser. No. 10/039,942 (“Etched Hole-Fill Stand-Off”) and 10/040,118 (“Hole Filling Using An Etched Hole-Fill Stand-Off”), herein incorporated by reference in their entireties. However, the solutions presented in those applications may not be suitable for all applications. Thus, there is a continuing need for improved methods and devices to facilitate hole filling.
SUMMARY OF THE INVENTION
Methods for improved electronic substrate via and thru-hole filling, particularly through the use of drilled stand-offs formed by control-depth drilling oversized non-thru-holes and the use of inserted support pillars to prevent sagging of the substrate during filling. In particular, through the use of: (1) via fill stand off adapted for use with a substrate comprising at least two via holes to be filled, each of the via holes having a diameter of X mils, the standoff comprising at least one recess formed by control-depth drilling of holes having a diameter at least Y times X mils where Y is one of 3, 9, and 12; and (2) a via fill standoff adapted for use with a substrate comprising at least one via hole to be filled, the standoff comprising: at least one recess; and at least one support pillar positioned within the recess wherein the support pillar is not an integral part of the standoff.
It is contemplated that a benefit to be obtained by the formation of stand-off recesses by controlled depth drilling of oversized holes is the retention of material in the standoff with the retained material adding to the total surface area available to support a substrate being filled.
It is contemplated that a benefit to be obtained by the formation of stand-off recesses by controlled depth drilling of oversized holes is the retention of material in the standoff with the retained material adding to the total surface area available to support a substrate being filled.
It is contemplated that a benefit to be obtained through the use of inserted support pillars is to increase the total amount of standoff surface area available to support a substrate being filled.
It is contemplated that a benefit to be obtained in forming a standoff by removing material from an otherwise solid, planar, and homogenous standoff in a manner that avoids creating thru-holes in the standoff is to provide a more rigid standoff better suited for supporting a substrate being filled.
It is contemplated that forming a stand-off having a recess where the edge of the recess is beveled may provide adequate clearance during filling of thru-holes near the edge of the recess while maximizing the ability of the stand-off to support a substrate being filled. It is also contemplated that use of such a bevel will help preventing embossing or other types of damage to the surface of the substrate being supported that contacts the stand-off, particularly when the substrate is forced against the stand-off during the filling process.
The methods and devices disclosed herein are particularly well suited for use when via and/or through hole filling is accomplished through the use of pressure fill heads as described in the following co-pending applications, each of which is incorporated herein by reference in its entirety: Ser. Nos. 09/752,503; 09/752,629; 10/039,942; 10/040,118; 10/026,135; 10/026,382; 10/026,337; and 10/026,338.
Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components.
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Lewis Charles W.
Pedigo Jesse
Schug Joseph
Greenberg & Traurig, LLP
Krietzman, Esq. Mark
Ortiz Angela
TTM Advanced Circuits, Inc.
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