JP3137314B2 - Liquid sealing material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid sealing material used for sealing a semiconductor.

[0002]

2. Description of the Related Art Liquid sealing materials are used for plastic pin grid array (hereinafter referred to as PPGA) type semiconductor encapsulation, but they are not sufficiently reliable in comparison with a hermetic encapsulation type using ceramics. The spread of plastic packages has been slower than that of dual in-line (hereinafter, referred to as DIP) type. The cause of the decrease in the reliability of the PPGA type semiconductor is as follows. [Moisture enters from a packaged organic printed wiring board. Unlike the transfer molding of the DIP package, the liquid sealing material flows into the package under no pressure and is molded, so that bubbles remain in the resin and cracks occur when thermal stress is applied. When thermal stress is applied due to the difference in the coefficient of linear expansion between the resin, the semiconductor chip, and the organic substrate, the resin is separated at the interface, thereby facilitating the penetration of moisture. And the like.

[0003]

SUMMARY OF THE INVENTION The present invention is directed to a liquid crystal which can greatly improve the reliability of a semiconductor even in accelerated tests such as a pressure cooker test (hereinafter, referred to as PCT) and a thermal cycle test (hereinafter, referred to as T / C). Is provided.

[0004]

Accordingly, the present invention has been intensively studied in order to solve the conventional problems as described above, and as a result, a liquid epoxy resin, an alkylated aromatic amine-based curing agent which is liquid at room temperature, have been developed. A composition obtained by blending diaminodiphenylmethane, a polybutadiene compound having an epoxy group, and a silane coupling agent with an inorganic filler having a specific particle size distribution is subjected to a pressure cooker test (hereinafter, PC).
T) and a thermal cycle test (hereinafter referred to as T / C), etc., have been found to be sealing materials that can significantly improve the reliability of semiconductors, and have completed the present invention. . That is, the present invention provides (a) a liquid epoxy resin, (b) an alkylated diaminodiphenylmethane, an aromatic amine-based curing agent which is liquid at room temperature, (c) a polybutadiene compound having an epoxy group, (d) an epoxy group, an amino group, In a silane coupling agent having at least one functional group selected from the group of mercapto groups in the molecule, and (e) a liquid sealing material mainly containing an inorganic filler having a specific particle size distribution, The mixing ratio is (c) / {(a) + (b) + (c)} = 0.03-0.
10, (d) / {(a) + (b) + (c)} = 0.02
０．１0.10 and (e) / ｛(a) + (b) + (c)
+ (D) + (e)｝ = 0.50 to 0.80,
The inorganic filler of (e) has an average particle size of 3 to 10 μm,
An inorganic filler having a particle size of 1 μm or less is 6 to 45% by weight of the total inorganic filler component, and an inorganic filler having a particle size of 30 μm or more has a particle size distribution of 25% by weight or less in the total inorganic filler component. It is a liquid sealing material, and can greatly improve the reliability of a PPGA type semiconductor using an organic printed wiring board.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid epoxy resin (a) used in the present invention contains 50% by weight or more of its components at 25 ° C.
Is preferably 10 Pa · s or less. Unless 50% by weight or more of the epoxy resin component is a low-viscosity liquid epoxy, the viscosity of the composition increases, and when the PPGA package is sealed with a liquid sealing material, bubbles are trapped or filled into corners. It is not preferable because defects easily occur and reliability is reduced. As a method of measuring the viscosity of epoxy resin, in the case of a material that is liquid at room temperature,
It is measured at 25 ° C. with an E-type viscometer manufactured by Toki Sangyo Co., Ltd. As long as the epoxy resin satisfies these requirements, it is not particularly limited, but specific examples include bisphenol A diglycidyl ether type epoxy resin, bisphenol F diglycidyl ether type epoxy resin, and bisphenol S diglycidyl ether type epoxy resin. Resin, 3,
3 ', 5,5'-tetramethyl-4,4'-dihydroxybiphenyldiglycidyl ether type epoxy resin,
4,4'-dihydroxybiphenyl diglycidyl ether type epoxy resin, 1,6-dihydroxybiphenyl diglycidyl ether type epoxy resin, phenol novolak type epoxy resin, bromine type cresol novolak type epoxy resin, bisphenol D diglycidyl ether type epoxy resin, etc. There is. These may be used alone or in combination. Further, in order to obtain a highly reliable liquid sealing material, it is preferable that the epoxy resin that can be used has as little ionic impurities as possible, such as Na ⁺ and Cl ⁻ .

The aromatic amine curing agent (b) used in the present invention is an alkylated diaminodiphenylmethane, which is liquid at ordinary temperature. Amines having no aromatic ring are poor in heat resistance and have a fatal drawback of poor storage stability because they are highly reactive even in an atmosphere of zero degree or less, and are not suitable for the present invention. In addition, in order to obtain a liquid sealing material having excellent reliability, amine-based curing agents that can withstand use include Na ⁺ and Cl ^−.
It is preferable that ionic impurities such as are as small as possible. The aromatic amine-based curing agent (b) can provide a material having extremely good fluidity by being combined with the liquid epoxy resin (a). Even when flowing into the package under no pressure and curing, no air bubbles remain, and problems with fluidity such as voids and unfilling hardly occur. The molar ratio {(a) / (b)} of the epoxy resin (a) as the main agent and the alkylated diaminodiphenylmethane of the aromatic amine-based curing agent (b) as the curing agent is from 0.9 to 1. 2 is desirable.
If the curing agent is less than 0.9 and the amount of the curing agent is too large, an unreacted amino group remains excessively, leading to a decrease in moisture resistance and a decrease in reliability. Conversely, if the ratio exceeds 1.2, that is, if the amount of the epoxy resin increases, the curing becomes insufficient, leading to a decrease in reliability.

Examples of the elastomer used in the present invention include (c) a polybutadiene compound having an epoxy group, which has good compatibility with the epoxy resin, and is expected to have low stress and toughness. In general, elastomers have a property of being poor in moldability due to bleeding after injection curing due to lack of compatibility with epoxy resins. However, by incorporating the epoxy group into a part of the molecule, the compatibility increases, and the epoxy resin partially reacts with the curing agent (b) and crosslinks.
It is considered that the bleeding property is improved, and the low stress and toughness specific to polybutadiene having an epoxy group can be exhibited. The polybutadiene compound having an epoxy group preferably has a number average molecular weight of 1,000 to 2,000. If it is less than 1000, bleeding tends to occur, and if it exceeds 2000, the viscosity becomes high, and both are not preferred. Further, the epoxy content (main chain addition mole fraction%) is preferably 3 to 10%.
If it is less than 3%, the compatibility is poor, and if it exceeds 10%, it crosslinks with the curing agent, so that a so-called sea-island structure cannot be obtained, so that a reduction in stress cannot be expected. For example, a three-point bending test can be used to confirm the reduction in stress, and a KIC measurement can be used to confirm the toughness. Excellent results can be obtained by any of the tests. By adjusting the amount of the polybutadiene compound having an epoxy group, low stress and toughness can be obtained to the maximum. (C)
/{(A)+(b)+(c)}=0.03 to 0.10, but if it is less than 0.03, the effects of lowering stress and toughening cannot be expected, and especially T / C (temperature During a cycle test), surface cracks are generated, leading to poor reliability. On the other hand, if it exceeds 0.10, the compatibility with the epoxy resin of (a) is deteriorated, which causes the oil to float on the package surface and cause bleeding, which causes a deterioration in moldability. In addition, a random copolymerized silicone-modified epoxy resin, a random copolymerized silicone-modified phenolic resin, or a polyolefin containing an epoxy group, which has a lower stress effect and is compatible with the epoxy group-containing polybutadiene compound (c). They may be combined.

As the silane coupling agent having at least one functional group selected from the group consisting of an epoxy group, an amino group and a mercapto group in the molecule (d), epoxysilane (for example, manufactured by Shin-Etsu Chemical Co., Ltd.) KBM-403) is preferred. If it is desired to enhance the adhesion to the substrate depending on the application, aminosilane and mercaptosilane may be added, if necessary, partially or entirely to the total amount of the coupling agent.

As the inorganic filler (hereinafter simply referred to as filler) of (e), for example, crystalline silica, fused silica or the like is used. The shape generally has a spherical shape, a crushed shape, a flake shape, and the like, but the linear expansion coefficient can be reduced by adding more filler, and a spherical inorganic filler is best for improving the effect. The amount of addition is (e) / ｛(a) +
(B) + (c) + (d) + (e)｝ = 0.50 to 0.8
0 is desirable. If it is less than 0.50, the above-mentioned effect of reducing the coefficient of linear expansion is small, and if it exceeds 0.80, the viscosity of the resulting liquid sealing material becomes too high, which is not a practical level. Further, by adjusting the particle size distribution of the filler, it is possible to maximize flow characteristics such as viscosity. It is generally known that a filler having a particle size distribution having a wider distribution range and a filler having a larger particle diameter tend to have a lower viscosity. However, fillers that have only a large particle size of, for example, 50 μm or more for the purpose of lowering the viscosity, have a relatively low viscosity, but a relatively heavy filler sinks during curing, and the composition above and below the cured product is reduced. So-called filler sedimentation with different ratios occurs. A disadvantage of using a filler having a large particle size is that the filler does not flow into a narrow gap. As represented by a PPGA type package, there is a tendency for packages to be multi-pin and space-saving, and as an example, the pitch between wires has recently become narrower. In order to allow the liquid sealing material to flow under no pressure and to be formed without any fluidity problems such as voids and unfilled, the filler has to have a small particle size. However, reducing the particle size also increases the problem that the fluidity is impaired. Therefore, the average particle diameter of the filler is 3 to 10 μm, which is smaller than that of the conventional liquid sealing material, and those having a particle diameter of 30 μm or more are reduced to 25% by weight or less of all the filler components. Does not impair the liquidity. In addition, the filler having a particle size of 1 μm or less is 6 to 45% by weight of the total filler component, and an appropriate amount of the fine filler is added and the particle size distribution is adjusted to suppress the sedimentation of the filler in which the fine filler easily sinks during curing. Can be. In the present invention, the particle size distribution and the average particle size are determined by a laser method (Ho
riba, LA-500). Note that the average particle diameter was a median diameter. The liquid encapsulating material of the present invention contains, in addition to the above-mentioned essential components, other resins and catalysts for promoting the reaction, if necessary, diluents, pigments, coupling agents, flame retardants, leveling agents, Additives such as foaming agents may be used.
The liquid sealing material is manufactured by, for example, dispersing and kneading each component, additive, and the like with three rolls and defoaming under vacuum.

[0010]

The present invention will be described below with reference to the following examples and comparative examples. Bisphenol F diglycidyl ether type epoxy resin: 100 parts by weight (epoxy equivalent: 155, 1.6 Pa · s / 25 ° C.) Naphthalene F diglycidyl ether type epoxy resin: (equivalent: 135, 124 Pa · s or less / 25 ° C.) Alkylated diaminodiphenylmethane curing agent: 42 parts by weight (amino equivalent 65) Polybutadiene rubber having an epoxy group: 5 parts by weight (number average molecular weight 1500, epoxy content 5 mol%) Glycidyltrimethoxysilane: 6 parts by weight Melting Silica: 350 parts by weight ・ Carbon black: 1 part by weight The above-mentioned raw materials were dispersed and kneaded with three rolls and subjected to defoaming treatment under vacuum to obtain a liquid sealing material. Using the obtained liquid sealing material, the PPGA package was sealed and cured in an oven at 165 ° C. for 3 hours to obtain a semiconductor package.

<< Evaluation Method >> Viscosity: The value measured at 2.5 rpm with an E-type viscometer (25 ° C.) was taken as a value. The higher the value, the worse. When the viscosity exceeds 50 Pa · s, workability at the time of dispensing deteriorates. -Thixo ratio: 0.5 rpm and 2.5 rpm with the above viscometer
The ratio of the viscosity in m was taken as the value. -Storage property: Time was taken for the viscosity to be twice the initial viscosity. ○: 72 hours or more, Δ: 24 to 72 hours, ×: 24 hours or less Curability: Inject liquid sealing material into PPGA package piece parts and cure at 165 ° C./3 hours under curing conditions.
The number of voids on the package surface and filler separation were observed. The number of voids on the surface of the package was observed with a microscope, and voids of several μm or more were taken as home. Unfilled packages are
Observation was performed using an ultrasonic killing machine (hereinafter referred to as SAT). For the filler separation, the cross section of the package was polished, and the thickness of the resin layer on the surface was measured. Those having a size of 5 μm or more were indicated as having filler separation. Number of evaluated PPGA packages is 1
There are zero. · Peeling after curing · Cracking Before PCT treatment (125 ° C / 2.3atm) After 720 hours T / C treatment (-65 ° C / 30 minutes ← → 150 ° C / 30)
Minutes) After 1000 cycles, the presence or absence of peeling and cracking between the semiconductor chip and the printed board interface was confirmed using SAT. The number of evaluated PPGA packages is 10
Individual.

Table 1 Shi Li Ca A B C D E F Mean particle size (μm) 5.4 4.2 7.8 2.5 3.2 7.3 1μm following weight% 30 39 20 40 48 10 wt% of 1~30μm 55 52 62 55 51 61 30μm or more wt% 15 9 18 5 1 29

Table 2 Example 1 2 3 4 5 Blended (parts by weight) Phenol F type cyclohexyl tereoxy resin 100 100 100 100 60 Naphthalene type cyclohexyl tere teroxy resin 40 Alkylated diaminodiphenylmethane 42 42 42 42 47 Polybutadiene rubber 5 5 5 5 5 Glycidyltrimethoxysilane 6 6 6 6 6 Carbon black 1 1 1 1 1 Fused silica A 350 500 350 Fused silica B 350 Fused silica C 350 Properties Viscosity (Pa · s) 30 45 36 24 38 Thixo ratio 1.2 1.2 1.3 1.1 1.3 Storage 性 ○ ○ 性 硬化 Curable Number of voids 0000 000 Unfilled 0000 000 Filler separation None None None None None Peeling after curing 0000 000 Cracking 0000 000 Peeling after PCT treatment 0 0 0 0 0 Crack 0 0 0 0 0 Peeling after T / C treatment 0 0 0 0 0 Crack 0 0 0 0 0 0

Table 3 Comparative Example 1 2 3 4 5 blended (parts by weight) Phenol F type cyclohexyl tereoxy resin 100 100 100 100 30 Naphthalene type cyclohexyl tereoxy resin 70 Alkylated diaminodiphenylmethane 42 42 42 42 45 Polybutadiene rubber 5 5 5 5 5 Glycidyltrimethoxysilane 6 6 6 6 6 Carbon black 1 1 1 1 1 Fused silica A 200 350 Fused silica D 350 Fused silica E 350 Fused silica F 350 Properties Viscosity (Pa · s) 43 54 27 17 76 Thix ratio 1.1 1.2 1.3 1.1 1.3 Preservability ○ ○ ○ ○ × Curable Number of voids 2 1500 0 3 Unfilled 1 2 0 0 20 Filler separation Yes No Yes No No Peeling after curing 0 0 0 0 Crack 0 0 0 0 0 PCT Separation after treatment 0 0 0 10 4 Crack 0 0 0 6 2 Separation after T / C treatment 0 0 0 10 0 Crack 0 0 0 0 10 0

[0014]

When the semiconductor package is sealed with the liquid sealing material of the present invention, a highly reliable semiconductor without peeling cracks can be obtained even in a pressure cooker test or a thermal cycle test. It is.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ Identification code FI H01L 23/31 (C08K 13/02 3:00 5: 541) (56) References JP-A-9-12684 (JP, A) JP-A-9-12685 (JP, A) JP-A-9-124898 (JP, A) JP-A-6-85117 (JP, A) JP-A-4-202318 (JP, A) JP-A-3-181547 (JP, A) JP-A-2-175757 (JP, A) JP-A-63-99221 (JP, A) JP-A-63-159423 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) C08L 63/00-63/10 C08L 9/00 C08G 59/50-59/60 H01L 23/29 C08K 5/541-5/5475

Claims (1)

(57) [Claims] 1. A liquid epoxy resin, (b) an alkylated diaminodiphenylmethane aromatic amine-based curing agent which is liquid at room temperature, (c) a polybutadiene compound having an epoxy group, (d) an epoxy group, an amino group, A silane coupling agent having at least one functional group selected from the group of mercapto groups in the molecule, and (e) an average particle diameter of 3 to 10
μm and a particle size of 1 μm or less account for 6% of all inorganic filler components.
-45% by weight and particle size 30μm or more are all inorganic
In a liquid encapsulating material containing, as a main component, an inorganic filler having a particle size distribution of 25% by weight or less in the filler component, the mixing ratio of each component is (c) / ｛(a) + (b) + ( c)｝
= 0.03-0.10, (d) / ｛(a) + (b) +
(C)｝ = 0.02-0.10 and (e) /
{(A) + (b) + (c) + (d) + (e)} = 0.5
Liquid sealing material characterized by being 0 to 0.80.