NL8202688A - Polyamide acids having carboxy gps. reacted with mono:amino:silane - giving polyimide(s) with improved heat stability - Google Patents

Abstract

A polyamide acid in which 2-60% esp. 10-40% of the COOH gps. present are reacted with a mono-aminosilane (I) is claimed. (I) is pref. a cpd. (I) in which Alk is 1-4C alkyl, R1 is 1-3C alkoxy, 1-3C alkyl or benzyl, and R2 is -(CH2)m- in which m= 1-4, or p-C6H4-. Pref. polyamide acid has the formula (II) in which R3 is chosen from (III), (IV), (V), (VI) in which R5 is -(CH2)m-in which m= 1-4, -CO-, -O-, -SO-, -SO2- or -CONH- and R6 is H or -CONH2, R4 is (VII), (VIII) in which R7 is -(CH2)m- where m= 1-4, -CO-, -O-, -SO- and -SO2- and n is at least 15. (II) is reacted with (I) in organic solvent soln. to give the modified polyamide acid. When subjected to imidisation at elevated temps., the modified polyamide acids give polyimides with improved heat resistance and adhesion. The compsns. can be applied by spraying, casting or dipping to give coating or passivating layers in electronic components such as semiconductors, chips, ICs, printed circuits, electrical conductors, etc.

Description

EHN 10,389 1 N.V. Philips' Incandescent lamp factories in Eindhoven "Polyamic acid derivative, process for its manufacture and polyindide obtained by imidization of the polyamic acid derivative".

The invention relates to a derivative of polyamic acid which, after imidization, yields a polyamide derivative with improved properties and in particular has an improved heat resistance. The derivative of the polyamic acid can advantageously be applied to, for example, all kinds of electronic components such as semiconductor elements, chips, ICs, circuits, electrical conductors. The relevant component is provided with a solution of the derivative of polyamic acid, for example by means of a spraying, pouring or dipping process. After imidization as a result of a heat treatment, the polyamic acid derivative is converted into a polyimide derivative which forms a heat-resistant, well-adhering coating or passivation layer on the electrical component.

The polyamic acid derivative according to the invention is a polyamic acid, of which 2-60% of the carboxylic acid present in the polyamic acid.

15 boxyl groups have been reacted with a mono-aminosilane.

Preferably 10-40% of the carboxyl groups are reacted with a mono-aminosilane.

In a further preferred form of the polyamic acid derivative according to the invention, the carboxyl-20 groups present in the polyamic acid are reacted with a mono-aminosilane corresponding to the formula OAlk -Si-R2 “NH2 (1) OAlk • 25 in which

Alk is an alkyl group of 1-4 carbon atoms, Rj is an alkoxy group of 1-3 carbon atoms, an alkyl group of just 1-3 carbon atoms or a benzyl group, and R2 is a bivalent organic radical corresponding to the formula 30 - (CH2) m "/ Where m = 1-4, or to the formula -4r \ -.

A very suitable mono-aminosilane is 1-aminopropyltriethoxysilane.

The derivative of the invention is prepared by treating a solution of polyamic acid in an organic solvent with the monoamino silane.

The reaction takes place under stirring at normal temperature. A suitable organic solvent is, for example, dimethylacetamide or 5 N-methyl-2-pyrrolidone.

The starting product, the polyamic acid, is a known commercially available substance. The polyamic acid as used in the method according to the invention can be represented by the formula --HN-OCv .COOH

10 (2) HOOC ^ ^ CO-NH-R --- L n wherein is a bivalent organic radical selected from the group consisting of: 0 · 0-0 · 0-s-Q-R6 and ^ ~ Λ-νϊΏΧ. o - »- o where R ^ is a bivalent organic radical selected from the group consisting of: - (CH ~) —-, where m = 1-4, <4'm - CO — o -, - SO— —SO2 — and — CONH—, and Rg is a hydrogen atom or a —CONH2 group, R ^ is a tetravalent organic radical selected from the group consisting of: -dpQ-£> -'-Q- wherein R ^ is a bivalent organic radical is selected from the group consisting of: - (CS ^ np ·, where m = 1-4, - CO -, - O -, - SO—, and —SO ^ - and n is at least 15.

The polyamic acid of formula (2) is of a conventional type. For this, reference can be made to United States Patent 3,943,065. The polyamic acid is prepared by reacting an organic dianhydride of the formula 8202688 1 ΐτ. · * ΡΗΝ 10.389 3 / ^ χ Χ ° χ <> 4 \> ° <3> ΝχΚ with an equivalent amount of an organic dia-5 mine of the formula —R3 —NH2 (4) in which and have the meanings indicated above.

The method according to the invention preferably starts from a polyamic acid which is obtained by reacting pyromellitic dianhydride 10 or 3.3 ', 4.41-benzofenontetracarboxylic dianhydride with an equivalent amount of 4,4'-diaminodiphenyl ether or 4.4' diaminodiphenyl ether-3-carboxamide.

It is pointed out that from Japanese patent application 50-17816 a modified polyamic acid is known which is obtained by using an excess of the organic dianhydride compared to the organic diamine. The resulting modified polyamic acid has, compared to the normal polyamic acid obtained as indicated above, by reaction of equivalent amounts of the dianhydride and the diamine, a shorter average molecular length and an excess of dianhydride end groups. The terminal dianhydride groups are reacted according to the Japanese patent application with an aminosilane corresponding to the formula NH2- (CH2) 2 - NH - (CH2) 3 - Si - (OR.) 2 k 25 wherein R 1, an alkyl group of 1- Is 3 carbon atoms and R 2 is an alkyl group, alkoxy group or phenoxy group.

Experiments have shown that the reaction with the aforementioned aminosilane yields an insoluble product which is not suitable for further imidization.

In a favorable embodiment of the method according to the invention, the polyamic acid of the formula (2) is treated with a mono-aminosilane of the formula (1), with 2-60% of the - COOH - groups as shown in formula (2) ) is converted to the group of the formula OAlk - CO —NH — R2 —Si — R1 (5) QAlk wherein Alk, R., and R2 have the previously mentioned meaning.

3202688 PHN 10.389 4

The invention also relates to a polyimide derivative obtained by imidization of the polyamic acid derivative described above.

The imidization is effected by gradually heating the derivative of the polyamide-5 acid after it has been applied to a substrate such as a silicon wafer to a temperature of about 250 to 350 ° C. The resulting polyimide derivative has improved thermal stability and shows good adhesion to the substrate.

As a result of the heat treatment, according to the invention not only the usual imidization occurs in which the —COCH groups of the polyamic acid (formula 2) react with the amino groups present in the polyamic acid which originate from the organic diamine (formula 4) but also reaction of the -COOH groups of the polyamic acid with the amino groups from the mono-aminosilane 15 (formula 5).

Preferably, the polyimide derivative obtained after imidization is immersed in water for several hours and then heated again at a temperature of, for example, 150 ° C. As a result of this post-treatment, a hydrolysis of the alkoxy groups bound to the Si-atoam is likely to take place and subsequently a condensation to form "Si-O-Si" structures.

The invention is further elucidated by means of the following exemplary embodiments and with reference to the drawing, in which Figures 1 and 2 both represent a graph showing the results of a heat treatment of different polyimides according to the invention. The heating time in hours is shown on the horizontal axis and the weight in percent of the initial weight of the polyimide on the vertical axis.

Embodiment Example 1 In a dry 500-ml flask equipped with stirrer, Calcium chloride tube and a sluice system suitable for the addition of solid under an inert atmosphere, 10.0 g (49.94 m.mol) of 4,4-diaminodiphenyl ether and 160 g of dry freshly distilled dimethylacetamide (DMAC) is added, keeping the flask contents under nitrogen throughout the preparation. To the vigorously stirred ice-cooled solution, 10.89 g (49.94 mole) of pyrellic acid anhydride is added through the sluice system. After the reaction is complete, the polyamic acid solution thus prepared is transferred to a cylindrical measuring vessel 8202688 PHN 10.389 5 v of a rotary viscometer. 5.52 g (24.98 mole) of aminopropyltriethyoxysilane is added to the solution, which corresponds to 25% by weight based on the carboxyl content of the polyamic acid. The spindle associated with the measuring vessel is placed in the measuring vessel and the liquid mixture is slid off at a sliding speed of 10 sec. . In a span of about three hours, the viscosity ranges from about 12 poises to about 300 poises and remains constant thereafter.

The solution is applied to an aluminum foil in a layer thickness of about 200 µm, then heated in a nitrogen atmosphere at 150 ° C for 1 hour and then at 300 ° C for another hour. The foil with the obtained polyimide derivative is dipped in water for several hours and then heated at 150 ° C for 1 hour.

A thermogravimetry measurement is carried out isothermally at 500 ° C in atmospheric oxygen on the product thus obtained. The results 15 are shown in the curve 1 (broken line) of the graph 1.

The graph horizontally shows the number of hours of heating at 500 ° C and vertically the weight of the polyimide expressed as a percentage of the initial weight. The results of honor; thermo-graphimetric measurements on the above polyamic acid that has not been treated with the amino silane are shown in curve 2 (solid line).

Output example 2

In a flask as described in embodiment 1, 10 g. (49.94 moles) 4.4-diaminodiphenyl ether, 1.35 g. (5.55 moles) 25 4,4'-diaminodiphenyl ether-3-carboxamide combined with 170 g.

N-methyl-2-pyrrolidone. The flask is kept under an N2 atmosphere throughout the preparation. 6.05 g are added to the ice-cooled solution with stirring. (27.75 moles) pyromellitic anhydride and 8.94 g.

(27.75 moles) benzophenone tetracarboxylic anhydride. After the reaction is complete, the cooling is removed and 2.46 g is added to the resulting polyamic acid solution. (11.09 mMol) aminopropyltriethoxy silane added with stirring.

The solution of the polyamic acid derivative thus prepared is placed on an aluminum foil and heated at 350 ° C for 1 hour.

The polyimide derivative formed was subjected to a thermogravimetric measurement as indicated in Example 1. The results are shown in curve 1 of the graph 2. The same test was carried out with a polyimide derivative according to the invention which 8202688 * * - · · ; PHN 10.389 6 was obtained according to the above procedure, whereby instead of 2.46 g. of the amino silane, 1.23 g. of the amino silane is added. The results are shown in curve 2 of graph 2.

A comparative test has also been carried out with a polyimide obtained according to the above example, but without the use of aminosilane. The results are shown in curve 3 of graph 2.

10 15 20 25 30 35 8 202 688

Claims (6)

1. Polyamic acid derivative of which 2-60% of the carboxyl groups present in the polyamic acid have been reacted with a mono-aminosilane. 2. A polyamic acid derivative according to claim 1, characterized in that 10-40% of the carboxyl groups present in the polyamic acid are reacted with a mono-amino silane. Polyamic acid derivative according to claims 1 or 2, characterized in that the carboxyl groups are reacted with a roomo-aminosilane corresponding to the formula OAlk i Rj - Si - R2 - NH2 (1) OAlk where Alk is an alkyl group of 1-4 carbon atoms, Rj is an alkoxy group of 1-3 carbon atoms, an alkyl group of 1-3 carbon atoms or a benzyl group, and R2 is a bivalent organic radical corresponding to the formula - (CH2) ^ -, where m = 1-4, or to the formula_ ^ ^ ^ 4. Process for the manufacture of the polyamic acid derivative 20 as defined in claim 1, 2 or 3, characterized in that a solution of polyamic acid in an organic solvent is treated with the mono-amino silane. 5. Process according to claim 4, characterized in that a polyamic acid corresponding to the formula 25 - -HN-OCL COOH ^ / R4 \ (2) HO ^ 'CCHNH-Rr-L' in which R ^ is a bivalent organic radical is selected from the group consisting of: * O · 0-0 · \ and / \ - NHC0i 8202688 PHN 10.389 8 4 where is a bivalent organic radical selected from the group consisting of: - (CH0), where m = 1-4, 2 m —CO—, - 0 -, —SO —, —SO2—, and —CCNH—, and Rg is a hydrogen atom or a —CCNH2 group, R ^ is a tetravalent organic radical selected from the group consisting of: 10 '' where Ry is a bivalent organic radical selected from the group consisting of: - {CHO - -, where m = 1-4, 2 m —CO—, - 0 -, —SO—, and - SO2 - 15 and n is at least equal to 15, is treated with a mono-aminosilane of the formula OAlk R. - Si - R ~ - NH «1 | 2Alk 20 wherein Alk, R 1 and R 2 have the meaning as defined in claim 3. 6. Polyimide derivative obtained by imidization of the polyamic acid derivative as claimed in claim 1, 2 or 3. 25 30 35 3202688