US4632798A
Expired / Lapsed
US
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Encapsulation of electronic components with anisotropic thermoplastic polymers
Assignee: Celanese Corp
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Filing: 1984-06-18
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Granted: 1986-12-30
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Expires: 2004-06-18
Abstract
Abstract An improved thermoplastic molding composition is provided which is particularly suited for use in the impervious void-free encapsulation on a relatively expeditious basis of an electronic component wherein the preformed electronic component is positioned in a mold cavity prior to the introduction of the molding composition via injection molding. The molding composition comprises a melt processable thermotropic liquid crystalline polymer which is of a relatively low weight average molecular weight of approximately 4,000 to 25,000 (e.g. approximately 4,000 to 10,000) and which is substantially incapable of further chain growth upon heating. Uniformly dispersed within the liquid crystalline polymer is approximately 40 to 80 percent by weight (e.g. approximately 50 to 75 percent by weight) of a particulate inorganic material (preferably of silicon dioxide) which serves to advantageously decrease its volumetric coefficient of thermal expansion and to advantageously increase its thermal conductivity. In a preferred embodiment the electronic component which is encapsulated is a semiconductor device, such as relatively delicate quad or dual-in-line integrated circuit device which is assembled onto a flat prestamped lead frame or other conductive device having a plurality of leads which extend outside the area which is encapsulated. The resulting encapsulated electronic component is well protected in spite of the relatively low molecular weight of the liquid crystalline polymer and is capable of satisfactory service for an extended period of time even if adverse environmental conditions are encountered. A rugged commonly non-burning and relatively inexpensive package is provided.
Inventors
- 👤 Nancy C. Eickman
- 👤 Charles E. McChesney
- 👤 Gary E. Williams
- 👤 Hyun-Nam Yoon
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 20:53
CPC Classifications
C; C08; C08L; C08L67/00; C08L67/02; H; H10; H10W; H10W74/00; H10W74/40; H10W74/47; C08G; C08G63/00; C08G63/02; C08G63/60; C08G63/605; C08K; C08K3/00; C08K3/34; C08K3/36; C08L77/00; C08L77/12; H01; H01B; H01B3/00; H01B3/18; H01B3/30; H01B3/42; Y; Y10; Y10T; Y10T428/00; Y10T428/23; Y10T428/239
Claims Analysis
Total Claims: 35
Claim 1
Independent Claim
218 words
A method for imperviously encapsulating on a relatively expeditious basis an electronic component using a novel composition incorporating a thermoplastic polymer which forms an anisotropic melt phase comprising: (1) introducing the electronic component to be encapsulated within a mold cavity, (2) completely filling the mold cavity surrounding said electronic component by injection at an elevated temperature of a molding composition comprising (a) a molten thermoplastic melt processable polymer which is capable of forming an anisotropic melt phase, has a weight average molecular weight of approximately 4,000 to 25,000, and which is substantially incapable of further chain growth upon heating as evidenced by an increase in the weight average molecular weight of no more than 15 percent when heated in an inert atmosphere for 30 minutes while at a temperature of 340° C., and (b) approximately 40 to 80 percent by weight based upon the total weight of the molding composition of a particulate inorganic material substantially uniformly dispersed in component (a) which is capable of decreasing the volumetric coefficient of thermal expansion and increasing the thermal conductivity of component (a), (3) cooling the contents of the mold cavity to allow said molding composition to solidify and to form an impervious package around said electronic component, and (4) removing said resulting imperviously encapsulated electronic component from said mold cavity.
Claim 2
Independent Claim
218 words
A method for imperviously encapsulating on a relatively expeditious basis an electronic component using a novel composition incorporating a thermoplastic polymer which forms an anisotropic melt phase comprising: (1) introducing the electronic component to be encapsulated within a mold cavity, (2) completely filling the mold cavity surrounding said electronic component by injection at an elevated temperature of a molding composition comprising (a) a molten thermoplastic melt processable polymer which is capable of forming an anisotropic melt phase, has a weight average molecular weight of approximately 4,000 to 25,000, and which is substantially incapable of further chain growth upon heating as evidenced by an increase in the weight average molecular weight of no more than 15 percent when heated in an inert atmosphere for 30 minutes while at a temperature of 340° C., and (b) approximately 40 to 80 percent by weight based upon the total weight of the molding composition of a particulate inorganic material substantially uniformly dispersed in component (a) which is capable of decreasing the volumetric coefficient of thermal expansion and increasing the thermal conductivity of component (a), (3) cooling the contents of the mold cavity to allow said molding composition to solidify and to form an impervious package around said electronic component, and (4) removing said resulting imperviously encapsulated electronic component from said mold cavity.
Claim 3
Dependent Claim
23 words
A method for imperviously encapsulating an electronic component according to the method of claim 1 wherein said electronic component is a semiconductor device.
Claim 4
Dependent Claim
45 words
A method for imperviously encapsulating an electronic component according to the method of claim 1 wherein said electronic component is an integrated circuit device which is assembled onto a flat prestamped lead frame having plurality of leads which extend outside the area which is encapsulated.
Claim 5
Dependent Claim
61 words
A method for imperviously encapsulating an electronic component according to the method of claim 1 wherein during step (2) the mold cavity is provided at a temperature of approximately 100° to 250° C., and the molding composition is introduced into the mold at a temperature of approximately 250° to 390° C. while under a pressure of approximately 100 to 1000 psi.
Claim 6
Dependent Claim
31 words
A method for imperviously encapsulating an electronic component according to the method of claim 4 wherein during step (2) the total molding cycle is conducted in less than one (1) minute.
Claim 7
Dependent Claim
47 words
A method for imperviously encapsulating an electronic component according to claim 1 wherein said molding composition exhibits a melt viscosity within the range of approximately 300 to 2500 poise at a shear rate of 100 sec. -1 and at the temperature it assumes while being injection molded.
Claim 8
Dependent Claim
55 words
A method for imperviously encapsulating an electronic component according to the method of claim 1 wherein said melt processable polymer which is capable of forming an anisotropic melt phase is selected from the group consisting of wholly aromatic polyesters, aromatic-aliphatic polyesters, wholly aromatic poly(ester-amides), aromatic-aliphatic poly(esteramides), aromatic polyazomethines, aromatic polyester-carbonates, and mixtures of the foregoing.
Claim 9
Dependent Claim
36 words
A method for imperviously encapsulating an electronic component according to the method of claim 1 wherein said melt processable polymer is wholly aromatic in the sense that each moiety present contributes at least one aromatic ring.
Claim 10
Dependent Claim
25 words
A method for imperviously encapsulating an electronic component according to the method of claim 1 wherein said melt processable polymer is a wholly aromatic polyester.
Claim 11
Dependent Claim
25 words
A method for imperviously encapsulating an electronic component according to the method of claim 1 wherein said melt processable polymer is a wholly aromatic poly(esteramide).
Claim 12
Dependent Claim
36 words
A method for imperviously encapsulating an electronic component according to the method of claim 1 wherein said melt processable polymer includes not less than about 10 mole percent of recurring units which include a naphthalene moiety.
Claim 13
Dependent Claim
49 words
A method for imperviously encapsulating an electronic component according to the method of claim 1 wherein said melt processable polymer includes not less than about 10 mole percent of recurring units which include a naphthalene moiety selected from the group consisting of 6-oxy-2-naphthoyl moiety, 2,6-dioxynaphthalene moiety, and 2,6-dicarboxynaphthalene moiety.
Claim 14
Dependent Claim
262 words
A method for imperviously encapsulating an electronic component according to the method of claim 1 wherein said melt processable polymer is a polyester which may include amide linkages which was formed through a polymerization reaction in a polymerization zone of monomers to yield a polymer having recurring moieties selected from the group consisting of the following where in each instance Ar comprises at least one aromatic ring: ##STR12## where Y is O, NH, or NR, and Z is NH or NR where R is an alkyl group of 1 to 6 carbon atoms or an aryl group, ##STR13## where Z is NH or NR where R is an alkyl group of 1 to 6 carbon atoms or an aryl group, and (f) mixtures of the foregoing; and wherein there was provided in the polymerization zone during said polymerization reaction an approximately 1 to 4 percent molar excess of aromatic dicarboxylic acid monomer and/or an esterified derivative thereof which during the polymerization reaction imparted dicarboxyaryl units to the interior of the polymer chains of the resulting polymer and caused the polymer chains to terminate in carboxylic acid end groups and/or an esterified derivative thereof wherein the polymer chain achieved the required molecular weight through the depletion of other monomers present in the polymerization zone to yield a polyester product which was substantially incapable of additional chain growth upon subsequent heating as evidenced by an increase in the weight average molecular weight of no more than 10 percent when heat in an inert atmosphere for 30 minutes while at a temperature of 340° C.
Claim 15
Dependent Claim
25 words
A method for imperviously encapsulating an electronic component according to the method of claim 13 wherein said polymerization reaction was carried out in the melt.
Claim 16
Dependent Claim
48 words
A method for imperviously encapsulating an electronic component according to the method of claim 13 wherein any monomer present in the polymerization zone which would otherwise include a hydroxyl group and/or an amine group was provided as a lower acyl ester of about 2 to 4 carbon atoms.
Claim 17
Dependent Claim
40 words
A method for imperviously encapsulating an electronic component according to the method of claim 13 wherein any monomer present in the reaction zone which would otherwise include a hydroxyl group and/or an amine group was provided as an acetate ester.
Claim 18
Dependent Claim
51 words
A method for imperviously encapsulating an electronic component according to the method of claim 13 wherein said polyester product exhibited an inherent viscosity of approximately 0.8 to 3.0 when dissolved in a concentration of 0.1 percent by weight in pentafluorophenol at 60° C. prior being amixed with said particulate inorganic material.
Claim 19
Dependent Claim
45 words
A method for imperviously encapsulating an electronic component according to the method of claim 13 wherein there was provided in the polymerization zone during said polymerization reaction an approximately 2.0 to 4.2 percent molar excess of aromatic dicarboxylic acid monomer and/or an esterified derivative thereof.
Claim 20
Dependent Claim
40 words
A method for imperviously encapsulating an electronic component according to the method of claim 13 wherein said melt processable polymer which is capable of forming an anisotropic melt phase has a weight average molecular weight of approximately 4,000 to 10,000.
Claim 21
Dependent Claim
210 words
A method for imperviously encapsulating an electronic component according to the method of claim 1 wherein said melt processable polymer is a wholly aromatic polyester which was formed through a polymerization reaction in a polymerization zone of ester-forming monomers to yield a polymer which consisted essentially of moieties I and II wherein: I is ##STR14## and II is ##STR15## wherein said polyester comprised approximately 20 to 45 mole percent of moiety I, and approximately 55 to 80 mole percent of moiety II, and wherein there was provided in the polymerization zone during said polymerization reaction an approximately 2.0 to 4.2 percent molar excess of aromatic dicarboxylic acid monomer which during the polymerization reaction imparted dicarboxyaryl units to the interior of the polymer chains of the resulting polymer and caused the polymer chains to terminate in carboxylic acid end groups wherein the polymer chains achieved the required molecular weight through the depletion of other monomers present in the polymerization zone to yield a whooly aromatic polyester product which was substantially incapable of additional chain growth upon subsequent heating as evidenced by an increase in the weight average molecular weight of no more than 10 percent when heated in an inert atmosphere for 30 minutes while at a temperature of 340° C.
Claim 22
Dependent Claim
40 words
A method for imperviously encapsulating an electronic component according to the method of claim 20 wherein said melt processable polymer which is capable of forming an anisotropic melt phase has a weight average molecular weight of approximately 4,000 to 10,000.
Claim 23
Dependent Claim
277 words
A method for imperviously encapsulating an electronic component according to claim 1 wherein said melt processable polymer is a wholly aromatic poly(ester-amide) which was formed through a polymerization reaction in a polymerization zone of ester-forming and amide-forming reactants to yield a polymer which consisted essentially of moieties I, II, III, and IV, in the quantities indicated wherein in each instance Ar is at least one aromatic ring, and wherein: ##STR16## II is ##STR17## III is --Y--Ar--Z-- where Y is O, NH, or NR, and z is NH or NR where R is an alkyl group of 1 to 6 carbon atoms or an aryl group, and IV is --O--Ar--O-- wherein said poly(ester-amide) comprised approximately 40 to 80 mole percent of moiety I, approximately 5 to 30 mole percent of moiety II, approximately 5 to 30 mole percent of moiety III, and approximately 0 to 25 mole percent of moiety IV; and wherein there was provided in the polymerization zone during said polymerization reaction an approximately 1 to 4 percent molar excess of aromatic dicarboxylic acid monomer which during the polymerization reaction imparted dicarboxyaryl units to the interior of the chains of the resulting polymer and caused the polymer chains to terminate in carboxylic acid end groups wherein the polymer chains achieved the required molecular weight through the depletion of other reactants present in the polymerization zone to yield a wholly aromatic poly(ester-amide) product which was substantially incapable of additional chain growth upon subsequent heating as evidenced by an increase in the weight average molecular weight of no more than 10 percent when heated in an inert atmosphere for 30 minutes while at a temperature of 340° C.
Claim 24
Dependent Claim
40 words
A method for imperviously encapsulating an electronic component according to the method of claim 22 wherein said melt processable polymer which is capable of forming an anisotropic melt phase has a weight average molecular weight of approximately 4,000 to 10,000.
Claim 25
Dependent Claim
37 words
A method for imperviously encapsulating an electronic component according to claim 1 wherein said melt processable polymer which is capable of forming an anisotropic melt phase has a weight average molecular weight of approximately 4,000 to 10,000.
Claim 26
Dependent Claim
43 words
A method for imperviously encapsulating an electronic component according to claim 1 wherein said particulate inorganic material is present in said molding composition in a concentration of approximately 50 to 75 percent by weight based upon the total weight of the molding composition.
Claim 27
Dependent Claim
53 words
A method for imperviously encapsulating an electronic component according to claim 1 wherein said particulate inorganic material has a weight average particle size of approximately 1 to 50 microns with at least 99 percent by weight of the particles being below 100 microns, and an average aspect ratio of no more than 2.1.
Claim 28
Dependent Claim
21 words
A method for imperviously encapsulating an electronic component according to claim 1 wherein said particulate inorganic material is particulate silicon dioxide.
Claim 29
Dependent Claim
20 words
A method for imperviously encapsulating an electronic component according to claim 27 wherein said particulate silicon dioxide is fused silica.
Claim 30
Dependent Claim
36 words
A method for imperviously encapsulating an electronic component according to claim 1 wherein said particulate inorganic material is fused silica which bears a surface coating which aids in accomplishing its substantially uniform dispersal in component (a).
Claim 31
Dependent Claim
37 words
A method for imperviously encapsulating an electronic component according to claim 1 wherein said particulate inorganic material is fused silica which bears a silane surface coating which aids in accomplishing its substantially uniform dispersal in component (a).
Claim 32
Dependent Claim
37 words
A method for imperviously encapsulating an electronic component according to claim 1 wherein said molding composition includes less than 50 parts per million of water-extractable alkali metal, and less than 100 parts per million of water-extractable halogen.
Claim 33
Dependent Claim
43 words
A method for imperviously encapsulating an electronic component according to claim 1 wherein following encapsulation the solidified molding composition exhibits a volumetric coefficient of thermal expansion of no more than 150×10 -6 cm. 3 /cm. 3 ° C. at 60° to 110° C.
Claim 34
Dependent Claim
33 words
A method for imperviously encapsulating an electronic component according to claim 1 wherein following encapsulation the solidified molding composition exhibits a thermal conductivity of at least 10×10 -4 cal.-cm./sec. cm. 2 ° C.
Claim 35
Dependent Claim
45 words
A method for imperviously encapsulating an electronic component according to claim 1 wherein following encapsulation the solidified molding composition exhibits hydrolytic stability as evidenced by a retention of at least 75 percent of the flexural strength thereof following 200 hours in water at 110° C.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-12-29 | 1990-06-30 | 1990-12-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-12-29 | 1994-06-30 | 1994-12-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-12-29 | 1998-06-30 | 1998-12-30 | $7700.00 | Window Closed / Lapsed |