Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1991-02-26
1993-03-16
Ryan, Patrick J.
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
428137, 428209, 4284111, 4284735, 4284744, 428901, B32B 900
Patent
active
051943166
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a laminar polymer sheet and to products made from such a sheet.
Published EP-A-0213774 describes methods of making uniaxially electrically conductive articles by making through-holes in a laminar polymer sheet, plating metal in the holes, and removing surface laminae from the sheet to leave the plated metal in each through-hole projecting beyond the main surfaces of the sheet. These conductive articles are commerically valuable as compliant electrical connection interfaces, for example for connecting microcircuit chips to other elements in an electronic device. The through-holes can be made conveniently small (preferably not more than 200 micrometers diameter) and may be close-packed so that random positioning of the article between opposed connection sites produces electrical connection when the sites are brought into contact with the opposite main surfaces of the article. Other forms of such articles are described in copending British Patent Applications 8802567, 8802565, 8802568, 8815447.1, 8819895.7, and 8823053.7, the disclosures of all of which are incorporated herein by reference.
In view of the wide use of polyimide materials in microelectronic devices, it is desirable to use polyimides for the uniaxially conductive articles, but this leads to problems in selecting suitable materials for the removable surface laminae.
The present invention relates to a novel laminar structure which is useful for various purposes, and is especially advantageous for making the aforementioned uniaxially conductive articles.
The invention accordingly provides a laminar sheet comprising a layer of polyimide material laminated in direct contact with a layer of amorphous, preferably amorphous aromatic, polyamide material.
It will be understood that references to sheets include elongate tape-like sheets and other forms of substantially continuous laminar structures, in which individual laminae are preferably homogeneous. For the purpose of making the aforesaid uniaxially electrically conductive sheets, it is preferable to use a sheet with each of the two main surfaces of the layer of polyimide material laminated in direct contact with a layer of aromatic polyamide material. It may be convenient in many cases that the polyimide layer is substantially co-extensive with the polyamide layer(s).
References to the respective layers being "laminated" do not imply any particular method of making the laminar structure. Solvent casting or melt coating of one material onto the other may be used, for example, as an alternative to lamination of two pre-existing solid films, provided that the desired laminar structure is achieved. For solvent casting, many solvents and solvent blends can be used including, for example:
n-methyl pyrrolidone/10% methanol blend
methanol/chloroform blend
dimethyl formamide (DMF)
dimethyl acetamide (DMAC).
If desired, small quantities of additives (e.g. UV absorbing chromophores such as aromatic carbonyl compounds, e.g. benzophenone) can be included.
Preferred amorphous polyamides include aliphatic/aromatic polyamides, trimethylhexamethylene diamine (preferably containing a mixture of 2,2,4- and 2,4,4-trimethylhexamethylene diamine isomers), bisaminomethylnorbornane isomers with one or more aliphatic, cycloaliphatic or aromatic dicarboxylic acids e.g. terephthalic acid and optionally including one or more amino acid or lactam e.g. epsilon-caprolactam comonomers, and bis-(4-amino-3-methylcyclohexyl) methane, propane with adipic and azeleic acids, and polyamides based on the condensation of trans cyclohexane-1,4-dicarboxylic acid with the trimethylhexamethylene diamine isomers mentioned above. acid.
Other preferred polyamides include those based on polyether and polyamide blocks, especially the so called "polyether-ester amide block copolymers" of repeating unit: ##STR1## wherein A represents a polyamide sequence of average molecular weight in the range of from 300 to 15,000, preferably from 800 to 5000; and B represents a linear or branched polyoxyalkylene sequence of average molecul
Horner Patrick J.
Ludden Michael J.
Nyholm Peter
Penneck Richard J.
Smith Nicholas J. G.
Burkard Herbert G.
Krynski W.
Novack Sheri M.
Raychem Limited
Ryan Patrick J.
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