International Business Machines Corporation

Donald Herman Glatzel

David John Russell

Richard Allen Day

Voya Rista Markovich

Kostas I Papathomas

Anilkumar Chinuprasad Bhatt

Allen Frederick Moring

John R Mertz

Robert David Allen

Gregory Michael Wallraff

John M Lauffer

William Dinan Hinsberg

Jeffrey Donald Gelorme

William D Hinsberg, Iii

Logan L Simpson

Norman A Card

Joel L Roth

An improved photoimagable cationically polymerizable epoxy based solder mask is provided that contains a non-brominated epoxy resin system and from about 0.1 to about 15 parts, by weight per 100 parts of resin system, of a cationic photoinitiator. The non-brominated epoxy-resin system has solids that are comprised of from about 10% to about 80% by weight, of a polyol resin having epoxy functionality; from about 0% to about 90% by weight of a polyepoxy resin; and from about 25% to about 85% by weight of a difunctional epoxy resin. The photosensitive cationically polymerizable epoxy based system is especially useful as a solder mask and does not contain bromine.

Composition for photoimaging

According to the present invention, an improved photoimagable cationically polymerizable epoxy based solder mask is provided that contains a non-brominated epoxy resin system and from about 0.1 to about 15 parts, by weight per 100 parts of resin system, of a cationic photoinitiator. The non-brominated epoxy-resin system has solids that are comprised of from about 10% to about 80% by weight, of a polyol resin having epoxy functionality; from about 0% to about 90% by weight of a polyepoxy resin; and from about 25% to about 85% by weight of an difunctional epoxy resin. Since the photosensitive cationically polymerizable epoxy based solder mask does not contain bromine, it is particularly advantageous halogens in waste processing chemicals or in incinerated scrap circuit boards are regulated by environmental concerns. The photosensitive cationically polymerizable non-brominated epoxy based solder mask has a glass transition temperature greater than about 100&deg; C., preferably greater than about 110&deg; C. The solder mask dries to a tack-free film; thus, artwork used in the photoimaging process will not stick to the dried soldermask film. The polyol resin which is a condensation product of epichlorohydrin and bisphenol A, has a weight average molecular weight of between about 40,000 and 130,000. The polyepoxy resin is an epoxidized multi-functional bisphenol A formaldehyde novolak resin having a weight average molecular weight of 4,000 to 10,000. The epoxidized diglycidyl ether of bisphenol A has two epoxide groups per molecule, a melting point of between about 80&deg; C. and about 110&deg; C. and a weight average molecular weight of between about 600 and 2,500. The invention also relates to a cationically polymerized solder mask.

An improved photoimagable cationically polymerizable epoxy based coating material is provided, that is suitable for use on a variety of substrates including epoxy-glass laminate boards cured with dicyandiamide. The material includes an epoxy resin system consisting essentially of between about 10% and about 80% by weight of a polyol resin which is a condensation product of epichlorohydrin and bisphenol A having a molecular weight of between about 40,000 and 130,000; and between about 35% and 72% by weight of an epoxidized glycidyl ether of a brominated bisphenol A having a softening point of between about 60&deg; C. and about 110&deg; C. and a molecular weight of between about 600 and 2,500. Optionally, a third resin may be added to the resin system. To this resin system is added about 0.1 to about 15 parts by weight per 100 parts of resin of a cationic photoinitiator capable of initiating polymerization of said epoxidized resin system upon exposure to actinic radiation; the system being further characterized by having an absorbance of light in the 330 to 700 nm region of less than 0.1 for a 2.0 mil thick film. Optionally a photosensitizer such as perylene and its derivatives or anthracene and its derivatives may be added.

Information handling system with circuit assembly having holes filled with filler material

A process for manufacturing circuit boards comprising providing a circuitized substrate having a dielectric surface, providing a peel apart structure including a metal layer and a peelable film, laminating the peel apart structure to the circuitized substrate with the metal layer positioned adjacent said dielectric surface, forming holes in the circuitized substrate through the peel apart structure, applying a filler material including an organic base to the peel apart structure, applying a sacrificial film onto the filler material, and applying sufficient heat and pressure to the sacrificial film to force the filler material into the holes to substantially fill the holes is provided.

Process for manufacturing a circuit board with filled holes

Circuit boards are manufactured by forming a substrate with a dielectric surface, laminating a metal foil and a peelable film to the substrate, and forming holes in the substrate through the peelable film and foil. A filler material with an organic base may be filled with electroconductive particles or dielectric thermoconductive particles. The filler material is deposited onto a sacrificial carrier and the filler material is heated to at least partially cure it. The filler material is laminated onto the peelable film with sufficient heat and pressure to force the filler material to fill the holes. For thermoconductive filler the holes are filled sufficient for electrical connection through the holes. The peelable layer, sacrificial carrier and filler material remaining therebetween are peeled off the copper foil. The filler material is abraded to the level of the foil and is then copper plated. The copper is patterned to form a wiring layer. A permanent dielectric photoresist layer is formed over the wiring layer and via holes are formed through the photoimagable dielectric over pads and conductors of the wiring layer. Holes are formed through the substrate and the photoimagable dielectric, walls of the via holes, and walls of the through holes are copper plated. The copper plating on the photoimagable dielectric is patterned to form an exterior wiring layer which is covered by solder resist with windows over lands around the through holes and surface mount connection pads of the exterior wiring layer to form a high density circuitized substrate. Surface mount components and/or pin in hole components are attached to the circuitized substrate with solder joints between terminals of the components and the lands and/or connection pads to form a high density circuit board assembly. One or more of the circuit board assemblies are mounted in an enclosure with a power supply, CPU, RAM, and I/O means to form an improved information handling system with increased performance due to shorter signal flight times due to the high component density.

Circuit board with wiring sealing filled holes

A circuit assembly that includes a circuitized substrate having a dielectric interior layer with a first surface and at least one hole therein. A filler material substantially fills the hole within the dielectric interior layer. A first wiring layer is positioned on the first surface of the dielectric interior layer, wherein the first wiring layer substantially covers the hole and assists in retaining the filler material within the hole in the dielectric interior layer. A first dielectric photoresist layer is positioned on the first wiring layer and on the first surface of the dielectric interior layer. The first dielectric photoresist layer also includes at least one hole therein. The filler material also substantially fills the hole within the first dielectric photoresist layer. A second wiring layer is positioned on the first dielectric photoresist layer and includes a plurality of conductive pads as part thereof. At least one external component can be electrically coupled to the conductive pads of the second wiring layer.

Circuit board assemblies having filled vias free from bleed-out

A novel process for circuitizing a dielectric layer, particularly for adding wiring planes, which is employed in the fabrication of circuitized structures, that does not requiring drilling of vias, yet provides good adhesion of circuitization to dielectric layer. In its broadest sense the method comprises the following steps: a. providing: a substrate; a hydrophobic, uncured, photoimagable, dielectric film having a solvent content of from about 5 to 30%; metal foil; b. contacting the metal foil and the dielectric film so that a replicate image is formed in the dielectric film; c. disposing the dielectric film on the substrate either after step a or step b; d. etching the metal foil from the dielectric film after step c; e. after step d, photoimaging the dielectric film to form vias or through holes in the dielectric film; and then metallizing the film after step e, to provide circuitization atop the dielectric film. The invention also relates to the circuitized structures produce by the method.

Process for high resolution photoimageable dielectric

Circuit boards are manufactured by forming a substrate with a dielectric surface, laminating a metal foil to the substrate, and forming holes in the substrate through the foil. A filler material with an organic base may be filled with electroconductive particles or dielectric thermoconductive particles. The filler material is deposited into the holes and is heated to at least partially cure it. The surface of the filler material is seeded and electrolessly plated to form a conductive coating on the metal foil and the filler material. The coating is then patterned to form a wiring layer. A second set of holes may be formed in the circuitized substrate after the hole filling step, which are also electrolessly plated.

Process for manufacturing a circuit with filled holes

Photoimageable dielectric materials are coated on substrates, selectively exposed and developed, whereby small vias and interconnection openings are formed between adjacently spaced circuit layers. A conductive paste may be used to provide sequential layer interconnection and surface planarization. No adhesives are required in the manufacture of a circuit assembly having multiple circuit and dielectric layers, and the manufacturing method avoids the requirement for drilled through holes and blind vias.

Method for manufacturing a high density electronic circuit assembly

Circuit boards are manufactured by forming a substrate with a dielectric surface, laminating a metal foil and a peelable film to the substrate, and forming holes in the substrate through the peelable film and foil. A filler material with an organic base may be filled with electroconductive particles or dielectric thermoconductive particles. The filler material is laminated onto the peelable film with sufficient heat and pressure to force the filler material to fill the holes. For thermoconductive filler the holes are filled sufficient for electrical connection through the holes. The filler material is abraded to the level of the foil and is then copper plated. The copper is patterned to form a wiring layer. A permanent dielectric photoresist layer is formed over the wiring layer and via holes are formed through the photoimageable dielectric over pads and conductors of the wiring layer. Holes are formed through the substrate and the photoimageable dielectric, walls of the via holes, and walls of the through holes are copper plated. The copper plating on the photoimageable dielectric is patterned of form an exterior wiring layer. Components and/or pins are attached to the surface of the circuitized substrate with solder joints to form a high density circuit board assembly.

Manufacturing circuit board assemblies having filled vias

An improved photoimagable cationically polymerizable epoxy based coating material is provided, that is suitable for use on a variety of substrates including epoxy-glass laminate boards cured with dicyandiamide. The material includes an epoxy resin system consisting essentially of between about 10% and about 80% by weight of a polyol resin which is a condensation product of epichlorohydrin and bisphenol A having a molecular weight of between about 40,000 and 130,000; and between about 35% and 72% by weight of an epoxidized glycidyl ether of a brominated bisphenol A having a softening point of between about 60.degree. C. and about 110.degree. C. and a molecular weight of between about 600 and 2,500. Optionally, a third resin may be added to the resin system. To this resin system is added about 0.1 to about 15 parts by weight per 100 parts of resin of a cationic photoinitiator capable of initiating polymerization of said epoxidized resin system upon exposure to actinic radiation; the system being further characterized by having an absorbance of light in the 330 to 700 nm region of less than 0.1 for a 2.0 mil thick film. Optionally a photosensitizer such as perylene and its derivatives or anthracene and its derivatives may be added.

The present invention provides a photoimageable soldermask that may be applied using aqueous solvents, thereby reducing the emission of organic solvents. The soldermask contains an epoxy based resin system comprised of at least one epoxy resin, a coating agent, and preferably a cationic photoinitiator and a dye.

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New Milford, PA, United States of America

Donald Herman Glatzel