Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
2000-09-19
2001-07-17
Diamond, Alan (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S192100, C204S192130, C204S192140, C204S192150, C204S192200, C427S471000, C427S096400, C427S097100, C427S099300, C427S534000, C427S536000, C427S537000, C427S248100, C427S255700, C427S533000, C427S377000, C427S314000, C156S272200, C156S272600
Reexamination Certificate
active
06261423
ABSTRACT:
FIELD OF THE INVENTION
The field of the invention is two sided substrate coating via physical vapor deposition.
BACKGROUND OF THE INVENTION
An integrated circuit (IC) package is a housing which environmentally protects the IC, facilitates testing of the IC, and facilitates the use of the IC in high-yield assembly processes. Such a package functions to protect an IC from mechanical and environmental stresses and electrostatic discharge. It also functions to provide a mechanical interface for testing, burn-in, and interconnection to a higher level of packaging such as a circuit card.
In many IC packages a substrate acts as an interconnecting layer between the terminals or pads on the IC, and the connectors or leads of the package. The substrate is typically mechanically and electrically coupled to both the IC and the package leads. The substrate may be made from a ceramic or organic material, may be rigid or flexible, and may comprise a single layer or multiple layers laminated together.
A substrate typically has two substantially planar sides located on opposite sides of the substrate. A substrate may include conductive patterns located on one or both of the planar sides, and may include conductive through holes or vias to provide a conductive path through the substrate. Substrate fabrication may include the steps of providing a base layer such as a polyimide film, forming vias in the base layer, covering the planar surfaces of the base layer with one or more metal layers and filling the vias with conductive material, removing portions of the metal layers to form the conductive pattern, and possibly coupling the resulting substrate with additional substrates to form a multi-layer substrate.
The step of forming vias in the base layer may be accomplished through the use of laser drilling. Although laser drilling provides many benefits, it typically leaves surface contaminants (“laser slag”) on the substrate surfaces. These surface contaminants are preferably removed prior to covering the surfaces with the metal layers. Although chemical and plasma cleaning methods are known, improvements in substrate cleaning have the potential of providing substantial economical and environmental savings.
The step of covering the surfaces of the base layer with one or more metal layers and filling the vias with conductive material is preferred to result in sufficient adhesion of the metal layers to the base layer so as to prevent future delamination. A measure of the ability to resist delamination is peel strength. Peel strength is typically measured as units of force per unit width such as lb/in or g/mm and is determined by measuring the amount of force required to peel a strip of the metal layer from the base layer.
Existing methods and devices sometimes produce an unsatisfactory result in that the resulting coated substrate suffer from relatively poor peel strength on one or more sides. Thus, it is desirable to develop new substrates having higher peel strengths, and methods and devices for producing such substrates.
SUMMARY OF THE INVENTION
The present invention is directed to improved substrates having higher, balanced peel strengths and methods and devices for producing such substrates. More specifically, a method particularly suited to coating substrates in which two sides of the substrate have unequal adhesion properties includes the steps of non-symmetrically coating the substrate by coating a first side under a first set of coating conditions and coating a second side under a second set of coating conditions wherein the coating conditions used to coat each side are varied so as to compensate for the unequal adhesion properties of the sides.
Also, a method for substrate preparation comprising the steps of: providing an annealed thermoplastic substrate base layer having a first surface and a second surface; stabilizing the substrate base layer in an environment having a baseline temperature and relative humidity; drilling vias in the base layer; subjecting the first and second surfaces of the base layer to ion processing so as to remove contaminants caused by drilling the vias and to prepare the first and second surfaces for sputtering; metalizing the base layer by first sputtering at least one metal layer onto the first surface of the base layer and subsequently sputtering at least one metal layer onto the second surface of the base layer said sputtering of the metal layers being controlled so as to prevent the temperature of the base layer from exceeding the annealing temperature of the base layer; allowing the metalized base layer to stabilize in an environment having the baseline temperature and relative humidity and then subjecting the metalized base layer to further processing so as to modify the metal layers into conductive patterns.
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.
REFERENCES:
patent: 5202220 (1993-04-01), Park et al.
patent: 5525369 (1996-06-01), Blackwell et al.
patent: 5840161 (1998-11-01), Woodard et al.
patent: 6153060 (2000-11-01), Pommer et al.
patent: 60-75835 (1985-04-01), None
patent: 2-193341 (1990-07-01), None
Avery Stephen M.
Pommer Richard J.
Roeters Glen
Brueske Curtis B.
Diamond Alan
Honeywell International , Inc.
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