JPH04369254A - Resin sealed type semiconductor device and its sealing material - Google Patents

Abstract

PURPOSE:To provide sealing resin excellent in balance of adhesion, low moisture absorption, and heat resistance by combining epoxy resin with a hardener and a hardening accelerator which have specified chemical structure. CONSTITUTION:As a sealing agent for a semiconductor element, epoxy resin of o-cresol novolak type, bisphenol type, or the like is used, and as a hardener, phenol compound (R is CH3, and n is an integer not less than one)shown by the formula is used. Moreover, as a hardening accelerator, the adduct with phenol novolak resin of 1,8-diazabicyclo (5,4,0)-7-undecene or its derivative is used, and as inorganic filling, fused silica, crystalline silica, alumina, or the like is used. For the hardener, 0.75-1.25 equivalents are mixed to one equivalent of epoxy resin, and for the hardening accelerator, 0.1-1.0wt. part is mixed to 100wt. part of resin ingredients of epoxy resin and hardener. Hereby, solder resistance, moisture resistance, and heat-cycle resistance improve.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a resin-sealed semiconductor device, and in particular to a resin-sealed semiconductor device and a resin-sealed semiconductor device that are less susceptible to package cracking due to heating during mounting and have excellent moisture resistance and reliability. This relates to retaining materials.

0002

2. Description of the Related Art Resin encapsulation technology has been widely used as a packaging technology for protecting semiconductor elements from the external environment and facilitating mounting on printed circuit boards. However, the integration density of semiconductor devices has been increasing at a rate of four times every three years, and the size of the devices has also been increasing accordingly. Furthermore, the number of pins is increasing as devices become more sophisticated and multifunctional.

On the other hand, due to the need for smaller size, lighter weight, and higher performance of various electronic devices, there is a strong demand for high-density packaging in various semiconductor devices, and packages are becoming smaller and thinner. As a result, the sealing resin layer of resin-sealed semiconductor devices tends to become thinner and thinner. The shape of the package is DIP (Dual Inline Plasma), which is mounted by inserting pins into through holes on a printed circuit board.
tic Package), ZIP (Zigzag I
nline Plastic Package), SIP
(Single Inline PlasticPac
The so-called pin-insertion type was the mainstream. However, in recent years, in order to increase the density of implementation, SOP
(Small Outline Plastic Pa
ckage), SOJ (Small Outline)
J-lead plastic package), QF
P (Quad Flat Plastic Packa
There is a rapid increase in demand for surface-mount packages such as ge) that can be mounted on both sides and have a small package size.

[0004] The thickness of such a package is extremely important, especially when trying to reduce the thickness of devices and components. Therefore, recently, TSOP (Thin Small Outlin
e Plastic Package), TSOJ (T
hin Small Outline J-lead
plastic package), TQFP (Th
nQuad Flat Plastic Packag
An ultra-thin surface-mount package with a thickness of 1 mm or less, such as e), is being developed.

[0005]

[Problems to be Solved by the Invention] However, as chips become larger and have more pins, packages become smaller and thinner, and surface mounting becomes more common, important technologies for manufacturing resin-sealed semiconductor devices become more important. An issue has arisen. In other words, with conventional pin-insertion type packages, the entire printed circuit board was inserted into a through-hole in the printed circuit board and soldered while floating in a solder bath, so the package body was not directly exposed to high temperatures. .

However, since surface-mount packages are generally soldered using infrared reflow or vapor reflow, the entire package is soldered directly to
Exposure to high temperatures of several tens of degrees. Generally, epoxy resin-based sealants are widely used for resin sealing of such semiconductor devices. However, epoxy resin-based encapsulants generally have significant moisture permeability, so that a small amount of moisture is always present in the package. Further, the adhesion between the sealing material and the lead frame, silicon chip, gold wire, passivation film, etc. that constitute the semiconductor device is not always sufficient, and defects such as gaps and microvoids exist inside the package. Therefore,
When the moisture inside the package is heated to exceed a specified amount, the moisture evaporates rapidly, and the vapor pressure generates stress inside the package, which can cause peeling, package cracks, and metallurgy between the various components that make up the package. There is a problem in that wire breakage occurs, which impairs device characteristics and reliability after mounting.

Thermal stress generated by water vapor pressure increases as chips become larger and thinner.
Furthermore, as the sealing resin layer of the package becomes thinner, it becomes easier for moisture to enter the inside of the package, and the strength of the package becomes weaker. Therefore, as chips become larger and sealing resin layers become thinner, there has been a strong desire to solve these problems with sealants.

When semiconductor components are mounted on a printed circuit board, a method is used in which the package is dried prior to mounting in order to prevent internal peeling and cracks occurring in the package. However, this method involves complications such as moisture management in the package and drying work. Therefore, as mentioned above, there is a strong desire for a package that will not cause internal peeling or cracking even if it is mounted in a state where the package has absorbed some moisture.

[0009] As a result of studying these countermeasures, the inventors of the present invention found that the adhesiveness of the sealing material to the lead frame, silicon chip, etc. should be increased to prevent moisture from accumulating inside the package. It has been found that it is important to reduce the moisture absorption rate of the encapsulant to reduce the absolute amount of moisture that enters the inside of the package, and to increase the high-temperature strength of the encapsulant to prevent the package from being damaged by thermal stress. Ta.

Conventionally, for resin-sealed semiconductors, the epoxy resin has the formula [2]

[0011]

[Case 2]

Phenol novolac type epoxy resin or o-cresol novolac type epoxy resin represented by (R is H or CH3), as a curing agent, formula [3]

0
013]

[Chemical formula 3]

Encapsulants whose main component is a phenol novolak resin represented by the following have been widely used. In addition, as curing accelerators, amine compounds, imidazole compounds,
Phosphine compounds, ammonium compounds, phosphonium compounds, etc. have been widely used.

The physical properties of such a sealing material include the molecular weight and equivalent ratio of the epoxy resin and curing agent components, the type of curing accelerator,
It can be greatly changed depending on the curing conditions and the like. However, in general, if you try to increase the adhesiveness of the sealing material and reduce the moisture absorption rate, the heat resistance will decrease, and conversely, if you try to increase the heat resistance, the adhesiveness will decrease and the moisture absorption rate will increase. , it has been extremely difficult to balance these characteristics.

The present invention has been made in view of the above, and its purpose is to provide a package with excellent moisture resistance and reliability, which is less likely to cause peeling, cracking, or disconnection of gold wires inside the package due to heating during mounting. An object of the present invention is to provide a resin-sealed semiconductor device.

Another object of the present invention is to provide a surface-mount resin-sealed surface-mounting type resin-sealed type that is less likely to cause peeling inside the package, cracks, or breakage of gold wires due to heating during mounting, and has excellent moisture resistance and reliability. The purpose of the present invention is to provide semiconductor devices.

Still another object of the present invention is to provide the above-mentioned sealing material.

[0019]

[Means for Solving the Problems] The present inventors have conducted various studies on the relationship between the chemical structures of various epoxy resins and curing agents and the various physical properties of the cured products. It has been found that by combining a curing accelerator, the above-mentioned properties of adhesiveness, low moisture absorption, and heat resistance can be balanced. The gist of the present invention is as follows.

(1) The semiconductor element is made of (a) epoxy resin,
A resin-encapsulated semiconductor device encapsulated with an encapsulating material containing (b) a curing agent, (c) a curing accelerator, and (d) an inorganic filler, wherein the (b) curing agent component of the encapsulating material is the general formula [1]

0
021]

[C4]

(R is H or CH3, n is an integer of 1 or more), the curing accelerator (c) is 1,8-diazabicyclo(5,4,0)-7
- A resin-encapsulated semiconductor device and its encapsulating material, characterized by containing an addition reaction product of undecene or its derivative with a phenol novolak resin.

(2) The semiconductor element is made of (a) epoxy resin,
(b) a curing agent, (c) a curing accelerator, and (d) a resin-sealed semiconductor device encapsulated with an encapsulant containing an inorganic filler, wherein the (b) curing agent of the encapsulant The components have the above general formula [
1] (R is H or CH3, n is an integer of 1 or more) and the curing accelerator (c) is 1,8-diazabicyclo(5,4,0)-7- Contains an addition reaction product of undecene or its derivative with a phenol novolac resin, has a glass transition temperature of 150°C or higher, an adhesive strength (peel strength) of 600g/cm or higher to aluminum foil with a thickness of 30 μm, and saturation at 85°C/98% RH. A resin-sealed semiconductor device and its sealing material, characterized in that its moisture absorption rate is 2% by weight or less.

The epoxy resin is preferably an o-cresol novolak type epoxy resin, a bifunctional or polyfunctional epoxy resin made from bisphenol A, or a difunctional or polyfunctional epoxy resin having a naphthalene or biphenyl skeleton.

As the curing agent (b) and the curing accelerator (c), commonly used curing agents or curing accelerators may be used in combination as long as the object of the present invention is not impaired.

The curing agent (b) represented by the above general formula [1] is used in an amount of 0.75 to 1 equivalent per equivalent of the epoxy resin (a).
1.25 equivalents are blended. Further, the curing accelerator (c) is blended in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the resin components of the epoxy resin and curing agent.

(d) As the inorganic filler, fused silica, crystalline silica, alumina, etc. are used, and if necessary, a coupling agent, a mold release agent, a coloring agent, a flame retardant, and a flexibility imparting agent are used. Agents etc. may be added.

[0028] Among these components, when a large chip is sealed in a small, thin surface-mount type package, inorganic components are used to prevent package cracking and deterioration of moisture resistance reliability due to heating during mounting. The choice of filler is also important. In particular, in order to reduce thermal stress, it is preferable to mix a large amount of inorganic filler to reduce the coefficient of thermal expansion of the sealing material. For these purposes, it is effective to use fused silica, which itself has a small coefficient of thermal expansion. In addition, blending a large amount of inorganic filler reduces the amount of resin component in the sealing material, which has the effect of reducing the amount of moisture that enters the inside of the package. Furthermore, increasing the amount of inorganic filler has the effect of improving the mechanical strength of the cured product, and in particular, using an inorganic filler with an average particle size of 1 to 20 μm, preferably 3 to 10 μm, significantly increases the high temperature strength of the cured product. improved,
This is effective in preventing package cracks and deterioration of moisture resistance reliability due to heating during mounting.

[0029] Furthermore, the coupling agent increases the wettability and adhesion between the resin component and the inorganic filler, reduces internal defects in the cured product, and is effective in improving the mechanical properties of the cured product and reducing moisture absorption. . In order to maximize the effect of adding a coupling agent, it is necessary to coat the surface of the inorganic filler with the coupling agent in advance so that a monomolecular layer is formed, and then knead this with the resin component and other materials. This is desirable. On the other hand, depending on the type of flexibility imparting agent, it has the effect of reducing the elastic modulus and thermal expansion coefficient of the sealing material and increasing the elongation rate at break.
It is effective in improving the crack resistance of small and thin packages. For this purpose, silicone compounds, polybutadiene, polyacrylonitrile compounds, and the like having functional groups such as epoxy groups, amino groups, carboxyl groups, and hydroxyl groups at terminals or side chains are effective. Depending on the purpose, these flexibility imparting agents may be added in an amount of 0.1 to 5 based on the total weight of the sealing material.
It may be used in an amount of 0.5 to 2% by weight, preferably 0.5 to 2% by weight.

[0030] The sealing material of the present invention is heated at 160 to 200°C, 1
It can be cured by heating for ~10 hours, preferably at around 180°C for 5 to 6 hours.

[0031]

[Operation] The reason why the resin composition of the present invention exhibits excellent adhesiveness, heat resistance, and low moisture absorption is considered to be as follows.

In general, the adhesion of a resin composition is determined by
■ The ease with which the resin wets the object to be adhered, ■ The ease with which chemical or physical bonds are formed between the resin and the object to be adhered, ■ The internal stress of the resin (curing shrinkage rate, modulus of elasticity, coefficient of thermal expansion) It is said that the toughness of the cured resin, etc. have a strong influence.

Furthermore, the heat resistance of the cured resin is related to the network concentration (crosslinking density) of the resin molecular chains, the cohesive energy density between the molecular chains, the rigidity of the molecular chains, etc., and the hygroscopicity is related to the free concentration in the cured resin. It is said that the volume fraction, the type and concentration of polar groups remaining or generated by reaction, etc. are related. As a result of examining various physical properties of the resin composition from such a viewpoint, it was surprisingly found that the resin composition of the present invention has a lower glass transition than the conventional resin composition even though the crosslinking density is the same, as shown in Figure 1. Temperature (Tg) is high. In other words, it has become clear that the same Tg is exhibited even with a lower crosslinking density. The reason why the resin composition of the present invention exhibits such behavior is considered to be because the cohesive energy between molecules and the rigidity of molecular chains are different from those of conventional compositions.

[0034] Normally, a semiconductor encapsulating material has a T temperature of 150°C or higher.
g is required. Tg is 1 using the resin composition of the present invention.
When attempting to produce a sealing material at 50° C., the crosslinking density of the resin may be quite low. A resin with a low crosslinking density has low elasticity at high temperatures, so relaxation occurs easily and little internal stress is generated. It also has toughness because the bridging is gradual. This is considered to be the reason why it exhibits excellent adhesion.

Furthermore, the reason why the sealing material of the present invention exhibits low hygroscopicity is considered to be that the free volume in the cured resin, which has a significant effect on hygroscopicity, is small depending on the crosslinking density.

Note that the sealing material of the present invention has a Tg of 150 to 2 when considering the balance of each property, heat resistance, economic efficiency, etc.
It is preferable to adjust the temperature to 15°C, a peel strength of 600 to 2000 g/cm, and a saturated moisture absorption rate of 0.5 to 2%.

[0037]

EXAMPLES Next, the present invention will be explained in detail with reference to examples. In addition, in the following examples and comparative examples, formulas (A) to (F
) and phenolic curing agents represented by formulas (G) to (I) were used.

[0038]

[C5]

[0039]

[C6]

[0040]

[C7]

[0041]

[Table 1]

[Examples 1 to 4] Epoxy resin, curing agent, and curing accelerator shown in Table 1: 1,8-diazabicyclo(5,4,0)-7-undecene (DBU), DBU
Addition reaction product between and phenol novolac resin: DBU-
Ad (1/3 weight ratio mixture heated at 150°C for 1 hour)
The resin components consisting of were weighed in the proportions (parts by weight) shown in Table 2, quickly mixed at 130 to 140°C, and degassed under reduced pressure. .5mm x width 12.7mm x depth 6.35mm)
The mixture was poured into a container and heat-cured at 180° C. for 6 hours. After cooling,
The sample was cut into a width of 10 mm along with the container, and the adhesive strength between the cured resin and the aluminum foil was measured by a 90 degree bending peel test at a pulling speed of 1 mm/min. Furthermore, a test specimen of 1 mm x 4 mm x 30 mm was cut out from the sample after the peel test, and the temperature dependence of dynamic viscoelasticity was measured at a frequency of 10 Hz, and the glass transition temperature (Tg) was determined from the peak temperature of tan δ.
I asked for In addition, the crosslinking density was determined from the elastic modulus of the rubber region using the following equation.

[0043]

[Equation 1] ρ=E/3φRT (ρ: cross-linking density, E: elastic modulus of the rubber region (tan δ peak temperature + 40°C), φ: front coefficient, R: gas constant, T: absolute temperature.) Similarly, using a test piece cut from the sample after the peel test, 80°C/80%RH
The moisture absorption rate when the sample was left for 340 hours was measured as the saturated moisture absorption rate. These results are shown in Table 1 and Figures 1 and 2.

[Comparative Examples 1 to 12] Using the epoxy resin, curing agent, and curing accelerator: DUB, DUB-Ad, or triphenylphosphine (TPP), the resin components were blended in the proportions shown in Table 1. The adhesiveness of the cured resin, the temperature dependence of dynamic viscoelasticity (Tg and crosslinking density), and the saturated moisture absorption rate were measured in the same manner as in Example 1 above.

These results are shown in Table 1 and FIGS. 1 and 2.

As is clear from Table 1 and FIG. 2, the resin composition of the present invention has high adhesive strength and glass transition temperature, and low saturated moisture absorption.

Next, semiconductor encapsulants having the compositions shown in Table 2 were prepared using the resin compositions used in the above examples and comparative examples.

[0048]

[Table 2]

[0049] A twin-screw roll was used for kneading each material, and kneading was carried out for about 10 minutes at a roll surface temperature of 80°C. In addition, a silicon chip (6
．． 4 mm x 16.6 mm square x 0.4 mm thick) on a 42 alloy lead frame (250 μm thick) using an epoxy resin conductive adhesive, and between the inner leads and the electrodes formed on the chip surface. A semiconductor device was fabricated by wire bonding with a gold wire having a diameter of 28 μm. A schematic cross-sectional view of the semiconductor device is shown in FIG.

Next, this semiconductor device was sealed using each of the above-mentioned sealing materials using a transfer press. Sealing is performed at a mold temperature of 180℃ and a transfer pressure of 70kgf/mm.
2. The molding time was 1.5 minutes. After the sealed product was removed from the mold, it was post-cured at 180° C. for 6 hours. After that, we processed the lead and made it 7.1mm long x 22.2mm wide x
TSOP (Thin Small) with a thickness of 1.0 mm
Outline Plastic Packag
A surface-mounted package called e) was fabricated.

[0051] In order to evaluate the solder reflow resistance of each package obtained in this way, each package was dried in advance under reduced pressure at 120°C for 48 hours, and then left at 85°C/85% RH. The package you took out, 21
It was placed in a vapor reflow tank at 5°C and heated for 90 seconds. Thereafter, the inside of the cooled package was observed using an ultrasonic imaging device to check for peeling and cracks inside the package. In addition, after heating for 168 hours at 85°C/85% RH, the package was heated for 90 seconds in a vapor reflow tank at 215°C and left at 65°C/85% RH.
The corrosion resistance of the aluminum wiring on the chip surface was evaluated. Similarly, after heating for 168 hours at 85℃/85%RH, 215
Temperature cycle test of package heated for 90 seconds in a vapor reflow tank at ℃ (-50℃/10 minutes ⇔ +150℃/
10 minutes) to evaluate the crack resistance of the package. These results are shown in Table 3.

[0052]

[Table 3]

Table 3 shows that the semiconductor device sealed with the sealing material of the present invention peels off inside the package due to heating during mounting.
It can be seen that the incidence of defects such as cracks is extremely low, and that it also has excellent moisture resistance reliability and temperature cycle resistance.

[0054]

[Effects of the Invention] Semiconductor devices encapsulated with the encapsulating material of the present invention have excellent resistance to solder reflow, moisture resistance, and temperature cycle resistance, which are required for surface-mount packages, the demand for which has been rapidly increasing in recent years. It has excellent reliability and is effective in reducing the size and weight of various electronic devices and electrical equipment and improving their performance.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between crosslinking density and glass transition temperature (Tg) of various epoxy resin compositions.

[Figure 2] Glass transition temperature (T
It is a graph which shows the relationship between g), adhesiveness (peel strength) to aluminum foil, and saturated moisture absorption rate.

FIG. 3 is a schematic cross-sectional view of the TSOP of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Silicon chip, 2... Gold wire, 3... Lead frame, 4... Sealing material, 5... Adhesive.

Claims (12)

[Claims] Claim 1: A semiconductor element is made of (a) an epoxy resin, (b)
A resin-encapsulated semiconductor device encapsulated with an encapsulant containing a curing agent, (c) a curing accelerator, and (d) an inorganic filler, wherein the (b) curing agent component of the encapsulant has the general formula [1] [Chemical formula 1] (R is H or CH3, n is an integer of 1 or more) and the curing accelerator (c) is 1,8-diazabicyclo(5,4, 0) A resin-sealed semiconductor device comprising an addition reaction product of -7-undecene or its derivative with a phenol novolac resin. [Claim 2] The semiconductor element is made of (a) an epoxy resin, (b)
A resin-encapsulated semiconductor device encapsulated with an encapsulant containing a curing agent, (c) a curing accelerator, and (d) an inorganic filler, wherein the (b) curing agent component of the encapsulant is General formula [1] (
R represents H or CH3, and n represents an integer of 1 or more. ) and the curing accelerator (c) are 1
, 8-diazabicyclo(5,4,0)-7-undecene or its derivatives with a phenol novolac resin, glass transition temperature 150°C or higher, thickness 30°C.
Adhesion strength (peel strength) to μm aluminum foil
A resin-sealed semiconductor device having a saturated moisture absorption rate of 2% by weight or less at 600 g/cm or more and 85° C./98% RH. 3. The curing agent (b) represented by the general formula [1] has a content of 0.75 to 100% per equivalent of the epoxy resin (a).
Claim 1 characterized in that 1.25 equivalents are blended.
2. The resin-sealed semiconductor device according to item 2. 4. The curing accelerator (c) is an addition reaction product of 1,8-diazabicyclo(5,4,0)-7-undecene or a derivative thereof with a phenol novolac resin, which is the epoxy resin and 4. The resin-sealed semiconductor device according to claim 1, wherein the amount is 0.1 to 10 parts by weight based on 100 parts by weight of the resin component comprising the curing agent (b). 5. The inorganic filler (d) has an average particle size of 1 to 2.
5. The resin-sealed semiconductor device according to claim 1, wherein the resin-sealed semiconductor device is 0 μm fused silica and is contained in the sealing material in an amount of 60 to 85% by weight. 6. The resin-encapsulated semiconductor according to claim 1, wherein the encapsulating material contains 0.1 to 5% by weight of a rubber component made of a silicone-based or polybutadiene-based compound. Device. 7. The resin-sealed semiconductor device according to claim 1, wherein the semiconductor device has a surface-mounted package structure. Claim 8: (a) epoxy resin, (b) curing agent, (c
) A curing accelerator, (d) An encapsulating material for semiconductor encapsulation containing an inorganic filler, wherein the curing agent component (b) has the general formula [1] (R is H or CH3, and n is an integer of 1 or more). ) and the curing accelerator (c) contains an addition reaction product of 1,8-diazabicyclo(5,4,0)-7-undecene or a derivative thereof with a phenol novolac resin. A sealing material characterized by: 9. The curing agent (b) represented by the general formula [1] has a content of 0.75 to 100% per equivalent of the epoxy resin (a).
Claim 8 characterized in that 1.25 equivalents are blended.
Encapsulant described in . 10. The curing accelerator (c) is an addition reaction product of 1,8-diazabicyclo(5,4,0)-7-undecene or a derivative thereof with a phenol novolac resin, which is the epoxy resin and 10. The resin-sealed semiconductor device according to claim 8, wherein the amount is 0.1 to 10 parts by weight based on 100 parts by weight of the resin component comprising the curing agent (b). 11. The inorganic filler (d) has an average particle size of 1 to 1.
The encapsulant according to claim 8, 9 or 10, characterized in that it is 20 μm fused silica and is contained in the encapsulant in an amount of 60 to 85% by weight. 12. The sealing material according to claim 8, which contains 0.1 to 5% by weight of a rubber component consisting of a silicone-based or polybutadiene-based compound.