Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-06-18
2001-08-28
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S258000, C526S259000, C526S261000
Reexamination Certificate
active
06281314
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to organic materials useful in the fabrication and assembly of electronic circuit components and printed wire boards.
BACKGROUND OF THE INVENTION
The complementary components to active microelectronic conductive circuits are resistors, capacitors, and inductors, known as passive components. These components, both the active circuits and the passives, are supported and interconnected on printed wire boards (PWB) in microelectronic devices.
While the integration of active circuit functions using silicon integrated circuits has been a major success, the integration of passive components is still in the developmental stage. Many of the passive components remain discrete, individual components, and often exceed in number by an order of magnitude the number of active integrated circuits on PWBs. This has increased the complexity of the PWBs and decreased the available surface area for other devices. The only alternative in the past has been to increase the size of the printed wire boards.
More recent advances in circuit board design provide for planar components formed on layers of the printed wire board, or for components buried in recesses in the board, resulting in a higher packaging efficiency. This integration of passive components reduces the number of electrical contacts or transitions between the active and passive components, which provides a consequent improvement in electrical performance and a reduction in mechanical stress at these transition points.
The utilization of integral passive components would be particularly advantageous in thin-film packages, and there is a significant effort within the industry to develop organic materials that will function reliably as passive components in microelectronic devices, particularly for thin-film packages. Moreover, as it is expensive to discard printed wire boards, it would be a manufacturing advantage to have an organic material that can be reworked.
In order to achieve the required mechanical performance and desired reworkability, relatively high molecular weight thermoplastics would be the preferred compositions. These materials, however, have high viscosity or even a solid film form, which are drawbacks to the manufacturing process.
Today, one of the primary thrusts within the semiconductor industry is to develop suitable materials for passive components, and particularly materials that would be reworkable.
SUMMARY OF THE INVENTION
This invention is a curable composition for fabricating electronic circuit components, defined herein to be both active and passive components, such as, conductors, resistors, capacitors, and inductors. The composition comprises one or more compounds containing one or more maleimide functionality, or one or more compounds containing one or more vinyl functionality, or a combination of compounds containing maleimide or vinyl functionality, a free-radical initiator and/or a photoinitiator, and optionally one or more fillers.
A compound containing one maleimide functionality will be referred to hereinafter as a mono-functional maleimide compound. A compound containing more than one maleimide functionality will be referred to hereinafter as a poly-functional maleimide compound. A compound containing one vinyl functionality will be referred to hereinafter as a mono-functional vinyl compound. A compound containing more than one vinyl functionality will be referred to hereinafter as a poly-functional vinyl compound. The functionality is defined herein to be a carbon to carbon double bond.
The composition can be designed to be reworkable by choosing a major amount of mono-functional compounds for the composition.
In another embodiment, this invention is a cured composition that results after the curing of the just described curable composition.
In another embodiment, this invention is a circuit component in or on a printed wire board prepared from a composition comprising one or more mono- or polyfunctional maleimide compounds, or one or more mono- or polyfunctional vinyl compounds other than maleimide compounds, or a combination of maleimide and vinyl compounds, a free-radical initiator and/or a photoinitiator, and optionally one or more fillers. As used herein, the use of the word “in” or “on” in connection with printed wire board shall include the other.
In another embodiment, this invention is a method for making an electronic circuit component on a printed wire board from a reworkable curable composition comprising the steps:
(a) providing a curable composition comprising
(i) one or more mono-functional maleimide compounds, or one or more mono-functional vinyl compounds other than maleimide compounds, or a combination of maleimide and vinyl compounds, in a major amount effective to provide thermoplastic properties, and
(ii) optionally, one or more poly-functional maleimide compounds, or one or more poly-functional vinyl compounds other than maleimide compounds, or a combination of poly-functional maleimide and vinyl compounds, in a minor amount ineffective to diminish the thermoplastic properties of the cured composition,
(iii) a curing initiator selected from the group consisting of a free-radical initiator, a photoinitiator, and a combination of those;
(iv) optionally, one or more fillers; and
(v) optionally, one or more adhesion promoters;
(b) applying the curable composition to the printed wire board; and
(c) curing the composition in situ.
The ability to process these thermoplastic compositions to form electronic circuit components is achieved by using relatively low molecular weight reactive oligomers or pre-polymers and curing them in situ on the printed wire board substrate. The relatively low molecular weight translates to a lower viscosity and ease of application to the substrate.
DETAILED DESCRIPTION OF THE INVENTION
The maleimide and vinyl compounds used in the compositions for the fabrication of circuit components are curable compounds, meaning that they are capable of polymerization, with or without crosslinking. As used in this specification, to cure will mean to polymerize, with or without crosslinking. Cross-linking, as is understood in the art, is the attachment of two polymer chains by bridges of an element, a molecular group, or a compound, and in general will take place upon heating. As cross-linking density is increased, the properties of a material can be changed from thermoplastic to thermosetting, which consequently increases polymeric strength, heat-and electrical resistance, and resistance to solvents and other chemicals.
It is possible to prepare polymers of a wide range of cross-link density, from tacky, elastomeric to tough glassy polymers, by the judicious choice and amount of mono- or polyfunctional compounds. The greater proportion of polyfunctional compounds reacted, the greater the cross-link density. Consequently, to obtain thermoplastic properties, the compositions of this invention can be prepared from mono-functional compounds to limit the cross-link density. However, a minor amount of poly-functional compounds can be added to provide some cross-linking and strength to the composition, provided the amount of poly-functional compounds is limited to an amount that does not diminish the desired thermoplastic properties. Within these parameters, the strength and elasticity of individual circuit component compositions can be tailored to a particular end-use application.
The cross-link density can also be controlled to give a wide range of glass transition temperatures in the cured circuit component composition to withstand subsequent processing and operation temperatures. For some circuit component compositions, the Tg may be chosen so that the composition will reflow after cure, thus providing the ability to rework the circuit component on the substrate.
In the inventive compositions, the maleimide compounds and the vinyl compounds may be used independently, or in combination. The maleimide or vinyl compounds, or both, will be present in the curable circuit component compositions in an amount from 2 to 98 weight percen
Ma Bodan
Tong Quinn K.
Xiao Chaodong
Gennaro Jane E.
National Starch and Chemical Investment Holding Corporation
Pezzuto Helen L.
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