Dielectric structure and method of formation

Details Dielectric structure and method of formation Dielectric structure and method of formation

1999-12-10

2002-12-17

Copenheaver, Blaine (Department: 1771)

Stock material or miscellaneous articles

Structurally defined web or sheet

Including aperture

C428S413000, C428S901000, C174S261000, C174S262000

Reexamination Certificate

active

06495239

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a dielectric structure, and an associated method of fabrication, wherein two fully cured photoimageable dielectric (PID) layers of the structure are interfaced by a partially cured PID layer.
2. Related Art
Mechanical or laser drilling of holes in dielectric layers of a multilayer dielectric structure is expensive. Such drilling would potentially be eliminated if the dielectric layers were to include fully cured PID layers having photovias. However, a practical method of adhesively joining a pair of such fully cured PID layers is needed. Note that a PID layer is a layer that comprises PID material.
SUMMARY OF THE INVENTION
The present invention provides a method for forming a dielectric structure, comprising the steps of:
forming a first layer, wherein the first layer includes a first fully cured photoimageable dielectric (PID) material;
nonadhesively forming a sticker layer on the first layer, wherein the sticker layer includes a partially cured PID material; and
nonadhesively forming a second layer on the sticker layer, wherein the second layer includes a second fully cured PID material.
The present invention provides a method for forming a dielectric structure, comprising the steps of:
forming a first layer, wherein the first layer includes a first fully cured photoimageable dielectric (PID) material;
nonadhesively forming a sticker layer on the first layer, wherein the sticker layer includes an internal power plane sandwiched between a first sheet of a partially cured PID material and a second sheet of the partially cured PID material;
nonadhesively forming a second layer on the sticker layer, wherein the second layer includes a second fully cured PID material.
The present invention provides a dielectric structure, comprising:
a first layer having a first fully cured photoimageable dielectric (PID) material;
a second layer having a second fully cured PID material; and
a sticker layer having a partially cured PID material, wherein the sticker layer is nonadhesively sandwiched between the first layer and the second layer.
The present invention has the advantage of replacing laser-drilled or mechanically-drilled vias with photovias, which potentially reduces the costs associated with forming vias in layers of a dielectric structure.
The present invention has the advantage of allowing formation of a via with a relatively high aspect ratio (i.e., ratio of via height to via diameter). For example, a sidewall of a typical photovia makes an angle of about 10 degrees with a via axis. In contrast, a sidewall of a typical laser-drilled via makes an angle of about 20 to 30 degrees with the via axis.
The present invention has the advantage that a PID layer (i.e., a layer comprising PID material) does not include glass fibers. Conventional, non-PID dielectric layers typically contains glass fibers. A dielectric layer that includes glass fibers is susceptible to having metallic material, such as copper, growing along a glass fiber so as to form a short between two conductors touched by the glass fiber.
The present invention has the advantage of being able to utilize continuous rolls of PID material for making partially cured PID layers, which is less expensive than using conventional pre-cut panels of dielectric material.


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McGrath, Peter “Multilayer PCB Manufacture”, Printed Circuit Fabrication 1978-1998, vol. 21, No. 2, pp. 20-24, Feb. 1998.

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