JPS601275A - Electrically conductive resin paste - Google Patents

Abstract

PURPOSE:To provide a highly heat-resistant electrically conductive resin paste having a high initial bonding strength and suitable as mounting resin, prepd. by adding silver powder, a solvent, etc. to a polyimide resin consisting of a thermo- plastic polyimide resin and a thermosetting epoxy resin. CONSTITUTION:The resin paste is prepd. by adding silver powder, a solvent (e.g. N-methylpyrrolidone or dimethylformamide), a hardener (e.g. dicyandiamide), a curing accelerator (e.g. tertiary amine), etc. to a polyimide resin obtained by blending a thermoplastic polyimide resin (e.g. pyromelletic acid/diaminodiphenyl ether condensate type) with a thermosetting epoxy resin (e.g. epoxidized phenol novolac resin) in a blend ratio of 90-99.5:0.5-10 by weight. The paste is suitable for sealing semiconductor elements.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conductive resin paste made of silver powder and a polyimide resin solution. More specifically, the present invention relates to a highly heat-resistant resin composition for mounting. The recent remarkable development of the electronics industry has led to the evolution of transistors, ICs, LSIs, and VLSIs, and as the degree of circuit integration in these semiconductor devices has rapidly increased, mass production has become possible. Coupled with the spread of semiconductor products using semiconductors, the mass production of these products has become increasingly popular! Improving performance and reducing costs have become important issues. Conventionally, semiconductor elements were fabricated using a substrate conductor and gold foil on a lead frame.
It was common practice to make semiconductor products by bonding using the U-3i eutectic method and then sealing with a hermetic seal. On the other hand, recently, 8J using epoxy resin etc.
Along with the development of the fat sealing method, Mount 8 was also developed using an epoxy resin-based conductive adhesive for R-circle mounts (Q
↑It has come to be done using fat. In the electronics industry, low-cost, mass-produced resin sealing is the mainstream, but especially in the field of high-performance products that require high reliability, methic seals still remain. Hermetic sealing includes methods such as metal sealing, ceramic sealing, and glass sealing, but sealing with low melting point glass is performed in all processes.

Therefore, since the adhesive layer between the chip and the substrate conductor (lead frame) is exposed to a high temperature of 450° C., high heat resistance is required. Conventionally, gold foil was used as the adhesive layer A.
U-5i eutectic method.

However, due to the soaring prices of negative metals, the cost is becoming significantly lower than that of neo-l, and there is also a need to automate and streamline the process, so even with this gift, we will continue to use resin mounts. It is rapidly transitioning. Epoxy-based Q! Grease-based products are insufficient, so polyimide-based products■
Preferably, f is 1' based.

The required temporality for mounting 4 (1↑addition) is as follows.

■Mount strength °When heated at 350℃, -65~]50℃
'J+2Z after thermal shock cycle, hydrothermal treatment)
;r'T.

Power.

■ Heat dissipation properties ■ 1B, air conductivity ■ Thicketing properties, quantitative injection properties, screen printing properties, and scrubbing properties.

■Curing properties Curing properties using the two-oven method, the flat plate method, etc.

■Void: Low.

■Reliability ゛No defects in the humidity resistance current test, i.e., no silver migration, no variation in device characteristics due to gas generated from cured adhesive, no corrosion of aluminum wiring due to ionic impurities such as halogens and alkali metals, etc. thing.

■Wire bonding properties: There should be no deterioration in bonding properties due to gas generated from the double-cured material, and no contamination due to bleeding.

■Bellet crack: A good buffer against stress caused by the difference in fl'% 11 with the lead frame (especially in the case of copper alloy).

However, conventionally this calm iF! Even if the heat-resistant mounting resin No. 11 has sufficient heat-resistant adhesive strength at the end of the Q curve, it is insufficient to build up the initial adhesive strength.
(Significant improvements were required in terms of performance and reliability. The reason for this was that the thermoplastic polyimide sides themselves had poor affinity with metal surfaces and poor adhesion.

As a result of various studies on these points, the inventors found that
Thermoplastic polyimide resins and liquid epoxy resins are compatible, albeit within a very narrow range, and ■ their blends are stable at water temperatures; ■ they cure quickly when heated;
In addition, the inventors have discovered that (5) there is a large rise in the initial stage of curing, (2) the cured product is uniform, and there is almost no deterioration in heat resistance, and based on these findings, the present invention has been completed.

The present invention is a conductive resin paste consisting of silver powder, a polyimide resin, and a solvent, in which the polyimide resin is a thermoplastic polyimide hJ resin of 90 to 99.5 parts (M amount, the same applies hereinafter) and a thermosetting liquid. By using a mixture of 0.5 to 10 parts of epoxy resin and p7J:, it is intended to obtain a highly heat-resistant liquid area mounting resin with improved adhesive strength. The silver powder used in the present invention preferably contains ionic impurities such as halogen ions and alkali metal ions at 10 ppm or less. The particle size is in the range of 0.1 to 50 μm, and if necessary, a mixture of relatively coarse flakes or dendritic particles and relatively fine particles may be selected and used.

Further, when producing silver powder, a surfactant such as metal soap may be added as a additive, but in this case it is preferable to remove it in advance by washing with hot water or the like. Washing is also effective in removing contamination and activating the surface of silver particles, but
Care must be taken as the particle size distribution may change considerably. The mixing ratio of silver powder in the present invention is preferably 70 to 85% (weight content, the same applies hereinafter) to the composition. If the amount is less than this, it is undesirable because it becomes easy to settle and separate, and the conductivity becomes low. If it is used more than that, the 'Xj' TI performance does not improve much, but the cost increases significantly and the adhesive strength etc. decreases. The polyimide resin used in the present invention is of the 1,t!ν plastic type, and is a linear polymer that is soluble in a solvent such as N-methyl-2-pyrrolidone. The types of polyimide resins include bis-acid anhydrides such as pyromellitic acid, benzophenone, and tetracarboxylic acid G2, and active unsaturated groups such as nadic acid, methylnadic acid, and maleic anhydride. Acid anhydrides and diaminodiphenyl ether, diaminodiphenyl ketone,
It is obtained by a condensation reaction between diaminodiphenylmethane, etc. and an aromatic diamino compound such as a lower alkyl nucleus or a substituted derivative thereof, and has a structure in which the main chain is linearly connected by imide groups. It is a polymer. These polymers are used as a solution of 10 ft) to 25 ft (weight, hereinafter the same) using a solvent such as N-methyl-2-pyrrolidone. Note that these polymers are usually in the form of polyamic acid in a solution state, and are insolubilized by dehydration and ring closure as the solvent evaporates during heating. The epoxy resin used in the present invention may be either a normal glycysil type or an alicyclic type. In order to obtain fast curing properties, it is recommended that each molecule contains a polyfunctional compound having three or more epoxy groups. As curing agents for epoxy resins, active water such as polyhydric phenols, polybasic acid anhydrides, etc.
El (r) is relatively stable at room temperature f! A curing agent is particularly preferred, and may further contain an amine or its mome as a third curing accelerator.As the solvent used in the present invention, N-methyl -pyrrolidone, dimethylpolamide,
Dimethylacetamide and the like have a good solubility (9). However, as a secondary 6 agent, high boiling point solvents such as cellosolves and carbitolre] may be used in combination as appropriate. Mixing with polyimide resin/epoxy 'tijl l]ir in light; +, 'IJ case is 9
It is essential that the ratio is 0 to 99.5/0.5 to 10 (ratio of weight -1). Generally, epoxy resin has low compatibility with polyimide fat, so even if it is used in excess, a homogeneous mixture cannot be obtained, which is not preferable since there is a risk that the contact force will be reduced. This is not desirable because the effect of adding less surface epoxy 1.'f↑ force cannot be produced, and the effect of accelerating the rise of force and slowing down during initial contact is eliminated. Polyimide position 1 fat used in the present invention, eboxyze 11 fat, solvent,
6 [,! The powder contains ionic impurities such as chloride ions and sodium ions at 10 ppm each (1 square meter).
It is desirable that the applicant has a degree of 6 or below. Epoxy+;
Among JJJir, glycysil type ones usually contain hydrolyzable halogen groups as impurities.

It contains several hundred ppmt or more, and unlike the ionic impurities mentioned above, it can be removed by conventional methods such as washing, distillation, and recrystallization. “
・It is 11 ugly things.

For the purpose of the present invention, it is preferable that 51-5 have as few hydrolyzable halogen groups as possible. However, in the present invention, since the blending ratio of Ebogishi;+Ir'J fat is small, the hydration molecule [H]: 4 of the halogen group does not have a very large influence, and 1,000 ppm or less is sufficient. Therefore, the mounting resin composition of the present invention has a lower content of hydrolyzable halogen groups than epoxy resin-based ones, and after the cured product is pressure tested (20 hours). One of the features is that the amount of eluted chloride ions and sodium ions is extremely small.The method for testing ionic impurities is as follows.

For chlorine ions, add 15g of liquid sample to 20ml of pure water! After shaking for 2 hours, the aqueous layer is divided into 3 cores and used as the test solution. Next, collect 15 cc of the test solution with a Pall pipette, add 4 mQ of 6% iron alum aqueous iW solution, and 2 m°C of 1.0.3% thiocyanic acid/mercury ethanol solution, and dilute with pure water until it reaches 25 mF. b1) The sample solution is 4 minutes) with a 0 photometer
We measured the suction e+2>f in the waves of 6011 m, and in comparison with a blank test, we used a pre-prepared test gland to determine the chloride ion contained as an impurity.
Take it once.

In addition, epoxy (:, J fat, tit fat composition for mounting,
Among the curing agents, viscous #J), etc., was uniformly dissolved in 30 mfl of sample 15f'r+-luene, and after shaking for 2 hours, the aqueous layer was centrifuged. Fil outside and use it as a cutting liquid, and then move it to the lower shuttle. Sodium ions were measured using a frameless atomic absorption spectrometer using the above t, jA 71 J:J: Absorption C degree at a wavelength of 33 (1, 2 nm). Using Sho H, we will collect the annual production of sl., liun, and ion, which are included as li materials.

Epoxy (hydration of σI fat 1)'f+1-salt type constant-;
; [Method: 491 fat, 107 fat, 30ml, and further 0. I N KOH-Ethanol ("rr liquid 5
0m1! The solution was refluxed for 30 minutes, and then the consumed butoalkali) was titrated with 0.1N HCl.

The consumed alkaline basin and the chlorine content of 'l f(') are combined into a total of two, and are considered as hydrolyzable chlorine charge.

Note that 0. The conventional 6i11 method was to heat and reflux an I N KOH methanol solution for 15 minutes, but in this case, the hydrolyzable chlorine was 1:- and the 111 was considerably undersized.
Since t is a) J, it is not suitable for the seventh objective of the present invention.

The manufacturing process of the JnT, I, and II oxides for mounting according to the present invention is as follows.

First, in a polyimide fat bath of a given jjQi, epoxy]
J・IJI 11 years old, pre-hardening, accelerated hardening, /i;
ri'J's group, Kano Nanano, mixes up and makes it a uniform CD liquid. For this:'; a mixing i, a normal stirring tank for this, 4
'jh crusher, three rolls, ink mill, etc.] may be used in combination as appropriate. Take the prescribed Buddha shun of R, and mix the above iMi with liquid 7a (IL) to make a completely uniform paste. r:′
Use in appropriate combinations such as one roll or three rolls. Next, the paste-like resin composition is distributed into predetermined containers using a pestle V4;9, and defoamed in a vacuum chamber to obtain a product. This J! , h mounting resin j (if the thickness is 1 or 2 j, sufficient defoaming will not be possible, so it is preferable to make the layer as thin as possible. The +f+, J resin composition obtained in this way is It is necessary to store and transport the product at a temperature of 15°C or lower.

If the temperature is higher than this, the shelf life will be slightly reduced, which is not preferable.

4.1.4) hi X', Ti oxide for mounting of the present invention has the following features compared to conventional products.

(1) High purity.

The number of ionic impurities, including those that are hydrolytically decomposable, in the cured resin for mounting is extremely small. u
(Depending on the material) The Pa food has been improved to 1:, 4, and is even better than conventional products in terms of reliability.

(2) It is fast curing.

It is cured in an oven at 150° C. for 1 hour and then at 250° C. for 1 hour, but the initial adhesive strength builds up quickly at this time.

(3) Contact at high temperatures; +J force is large.

It has sufficient contact strength (mounting strength) to withstand high temperatures of 450°C during hermetic sealing.

(4) Other features such as heat dissipation, electric body centering, dispenser stripability, low voids, iron migration silicone, contamination from generated gas, and no malfunctions such as pellet cracks are inferior to conventional products. Something that doesn't exist appears.

Therefore, the i'4J fatty acids for Mav-Nt of the present invention are K
4.Cuthro-Cus a3'J, a vassal who is rapidly becoming more sophisticated.
? It is of extremely high industrial value as it meets the needs of In addition, F, y, j, by pressure cutter test,
The method for measuring water-decomposable chlorine ions is as follows.

Mounting tree) i'a is cured at 200'C for 130 minutes, and then the cured product is crushed. The prepared powder sample 122 is thoroughly immersed in a decomposition crucible by adding ethanol 3g C. Next, after adding 40 mfl of pure water, the container was completely sealed and treated at 125° C. for 20 hours. After treatment, centrifuge for 1+71 t and use the supernatant as the test solution. Chlorine ions in the test solution are transmitted 4 times, sodium ions are detected.

Examples will be described below.

Example polyimide 4iiJ Jiir kj: Pyromerite j
:ii/diaminodiphenyl needle condensation type (polyamic acid sugar 15% 01<if, same below) N methylpyrrolidone solution) 160 parts (New Year's Day, same below),
The epoxy resin is epoxidized phenol novolac (number average molecule j<I,': G 80, epoxy Todoro Jim
: 180, Number of epoxy groups: 7 molecules: 3.6, Hydrolyzable chloro group: 800 ppm) O12 part f, J,':
'I is 1゛, and the homogeneous solution is 71゛Y. Furthermore, silver powder 10
Add part 0 and watch!・In a crusher, P, π・(After 1st and 6th round, roll three rolls to make a uniform paste-like mounting tree). A) Jfj composition for paste-like mounting is liquid JIX 20v
Spread in a vat to less than n and store in a vacuum chamber at room temperature for 5 minutes.
maIIf? Pack jQ and r under high vacuum as follows. Taking it off?
The chips were applied to a capacity by screen printing or stamping onto a prepared (I) composite acid frame and the chip was mounted. ,
11・fli! Curing of ¥ is obtained by heating in an oven at 150°C for 60 minutes and then at 250°C for 60 minutes.

The performance of each detail of the mounting resin is shown in Table 1. In addition, although the above-mentioned polyimide (resin formula was made in exactly the same way as epoxy 1 except that no fat was added) l acid was produced, the initial build-up of the contact force was slow. The punchability was extremely poor and undesirable.

Table 1 Performance of resin for mounting (Note) *X10'Ωcf3 ** Director-General of the Agency 1. Indication of the case Patent Application No. 107766 filed in 1982 2. Name of the invention Conductive tH fat paste 3. Relationship with the person making the amendment Patent applicant address 1-2 Uchisaiwai-cho, Chiyoda-ku, Tokyo No. 2 No. 4, Detailed description of the invention in the specification subject to amendment.

5. Contents of correction (1) Page 10, line 15 “Combine 10B into Toluev 30ml, and add 0.IN
[0.5 g of KOIIJ is stopped in 30 ml of dioxane and further corrected to IN KOIIJ.

(2) Page 10, line 16 [50+nlJ to 15m1J
Correct to.

Supplementary Procedures for the above"r', written (self-motivated) January 59, 1980 Dear Commissioner of the Japan Patent Office 1, Indication of the case Patent Application No. 10'7766 of 1988 2, Name of the invention Conductive resin paste) 3. Relationship with the case of the person making the amendment Patent Applicant Address: Tokyo t;1;

5. Contents of amendment (1) Page 10, No. 1. '7 ``j'' ``The amount of alkali consumed (by 1,lNl-lCl'') is 1-11 of the chlorine ion produced, Q, 1
)IABNo.,'' j+u is corrected.

(2) Page 10, lines 18-11]

Claims (1)

[Claims] An electrically sensitive resin paste consisting of silver powder, a polyimide resin, and a solvent, where the polyimide resin is a thermoplastic polyimide resin and a thermosetting epoxy resin, and the blending ratio (weight) of RR polyimide resin to epoxy resin. is 90-99
．． 5/A highly resistant acute conductive resin paste with excellent initial adhesion strength, characterized by a ratio of 0.5 to 10.