JP3286891B2 - Liquid resin sealing and curing method - 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 resin sealing and curing method for sealing a bare chip IC using a liquid resin containing a thermosetting epoxy compound and heating and curing the same.

[0002]

2. Description of the Related Art Conventionally, when a bare chip IC is mounted on a substrate and then sealed with a liquid resin and heat-cured, the optimum curing temperature and curing time are determined according to the curing conditions of the sealing resin as shown in FIG. A thermal curing method in which a temperature required for curing is applied for a certain period of time with a simple temperature profile. FIG. 3 is a diagram in which a bare chip IC is sealed with a liquid resin by the above liquid resin sealing and curing method. Reference numeral 1 denotes a substrate, 2 denotes a bare chip IC mounted on the substrate 1 by die bonding 3, and 4 denotes a liquid resin for sealing the bare chip IC 2, which is a liquid resin containing a thermosetting epoxy compound. Reference numeral 5 denotes a diffusion prevention cell for preventing the liquid resin 4 from flowing out. Reference numeral 6 denotes a wire connecting the bare chip IC 2 and the substrate 1 and is disposed inside the liquid resin 4.

[0003]

However, in the above-described conventional liquid resin sealing and curing method, when the bare chip IC 2 is sealed on the substrate 1 with the liquid resin 4, air bubbles are generated from below the wire 6 and between the substrate 1 and the bare chip IC 2. This causes a problem that pinholes 7 occur on the surface of the cured sealing resin as shown in FIG.

There is another problem that the wire 6 is broken due to thermal expansion and contraction of the cured sealing resin.

There is another problem that the substrate 1 on which the bare chip IC 2 is mounted is warped due to thermal expansion and contraction of the cured resin.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended to prevent the occurrence of pinholes and the occurrence of wire breakage on the surface of a cured liquid resin. The aim is to get the method.

It is another object of the present invention to provide a liquid resin sealing and curing method capable of suppressing a warp of a substrate on which a bare chip IC is mounted in a process of curing a liquid resin.

[0008]

SUMMARY OF THE INVENTION A liquid resin according to the present invention is provided.
The sealing and curing method is a method of sealing and curing a bare chip IC mounted on a substrate with a liquid resin containing a thermosetting epoxy compound, wherein the liquid resin is held at a temperature at which the liquid resin is thermally cured. And a step of maintaining the glass transition temperature above and below the glass transition temperature of the substrate.

A bare chip IC mounted on a substrate
In a liquid resin encapsulation curing method of sealing and curing with a liquid resin containing a thermosetting epoxy compound, a step of maintaining the temperature of the liquid resin at a temperature at which the viscosity sharply decreases, and a temperature at which the liquid resin is thermally cured. And holding at a temperature above and below the glass transition temperature of the substrate.

[0010] In addition, there is a method in which the step of maintaining the substrate at a temperature above and below the glass transition temperature of the substrate is divided into a plurality of steps and performed stepwise.

Another method is to seal and harden a plurality of bare chip ICs on a substrate.

Further, in the method, the liquid resin contains a component containing a thermosetting epoxy novolak compound.

[0013] Further, in this method, a wire connecting the bare chip IC and the substrate is disposed inside the filler-rich layer of the liquid resin.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a diagram showing a temperature profile in the liquid resin sealing and curing method according to the first embodiment of the present invention. Generally, there is a temperature range in which the viscosity of the epoxy-based liquid resin sharply decreases when the temperature is increased by heating. FIG. 5 shows the relationship. As shown in FIG. 1, the heating temperature for the liquid sealing resin 4 is maintained for a certain time A1 (min) around a temperature T1 ° C., which is a temperature range where the resin viscosity sharply decreases, and the viscosity of the liquid sealing resin 4 is reduced. By lowering, the air bubbles existing below the wire 6 and between the substrate 1 and the bare chip IC 2 can be removed before the surface of the liquid sealing resin 4 is hardened, and the pinholes generated on the hardened sealing resin surface can be removed. Generation can be suppressed.

When the viscosity of the liquid sealing resin 4 is lowered at a curing temperature of about T1 ° C., as shown in FIG. 6, the filler, which is the basic composition of the epoxy resin in the liquid sealing resin, has a higher specific gravity than the curing agent. For this reason, the liquid sealing resin 4 is separated into two layers of a filler-rich layer 9 below the boundary line 10 and a hardener-rich layer 8 above the boundary line 10. Due to this separation, the periphery of the wire 6 is filled with a large amount of filler. Since the filler generally has a low coefficient of thermal expansion in the composition of the liquid sealing resin 4, the separation by the specific gravity results in a filler-rich state in the periphery of the wire 6. Can be further suppressed.

After the viscosity of the liquid sealing resin 4 has been reduced, the surface of the liquid sealing resin 4 is hardened. Then, the heating temperature for the liquid sealing resin 4 is kept at A2 (min) for a certain period of time to perform partial curing. After this,
Temperature TE ° C required for full-scale heat curing of liquid sealing resin 4
Step heating is performed step by step until. Accordingly, it is possible to prevent the occurrence of pinholes due to bubbles remaining in the sealing resin despite the processing in the step of maintaining the liquid resin at a temperature at which the viscosity of the liquid resin sharply decreases.

Further, the heating temperature of the liquid sealing resin 4 is maintained at TE3 ° C. for a predetermined time A3 (min), and the glass transition temperature TG ° C. of the substrate 1 is obtained in the process of cooling the heat-cured liquid sealing resin 4 to normal temperature. A4 for a certain time at T3 ° C
(Min) annealing, and then annealing for a certain time A5 (min) stepwise after T4 ° C.
It is possible to suppress the warpage of the substrate 1 on which the bare chip IC 2 is mounted, which is caused by thermal distortion caused by heat curing.

Embodiment 1 Even when a plurality of bare chip ICs 2 on a substrate 1 are sealed with a liquid resin 13 and cured by heating.
By performing the step cure and the step annealing as described above, the same effect can be obtained.

In the case where two or more different resins are cured in the same process, each resin is step-cured in the same process at a temperature at which the viscosity of each resin decreases as in the first embodiment. Thus, the same effect can be obtained. For example, it shows a case where an epoxy-based resin and a silicon-based resin are applied on the same object and then cured in the same process.

Even when the gap between the substrate and the bare chip IC is sealed around the bare chip IC 2 on the substrate 1 with the liquid sealing resin 4, the same effect can be obtained by performing step curing as in the first embodiment. can get.

In the case where the gap between the substrate and the bare chip IC is sealed around the plurality of bare chip ICs 2 on the substrate 1 with the liquid sealing resin 4, the same effect can be obtained by performing step curing as in the first embodiment. The effect of is obtained. In addition, even if a resin containing a composition containing a thermosetting epoxy novolak compound having excellent electrical insulation, heat resistance, and water absorbency is used as the liquid resin, step curing is performed as in the first embodiment. Thus, the same effect can be obtained.

[0023]

As described above, according to the present invention, there is provided a liquid resin sealing and curing method for sealing and curing a bare chip IC mounted on a substrate with a liquid resin containing a thermosetting epoxy compound. The step of holding the resin at a temperature at which the resin is thermally cured and the step of holding the resin at a temperature equal to or lower than the glass transition temperature of the substrate have an effect of suppressing the warpage of the substrate on which the bare chip IC is mounted.

A bare chip IC mounted on a substrate
Encapsulating and curing with a liquid resin containing a thermosetting epoxy compound, a step of maintaining the liquid resin at a temperature at which the viscosity of the liquid resin sharply decreases, and a step of maintaining the temperature at which the liquid resin is thermally cured And the step of holding at a temperature above and below the glass transition temperature of the substrate, thereby suppressing the occurrence of pinholes occurring on the sealing resin surface and reducing the warpage of the substrate on which the bare chip IC is mounted. It has the effect of suppressing.

Further, the step of maintaining the substrate at a temperature above and below the glass transition temperature of the substrate is divided into a plurality of steps and is performed stepwise, that is, between TE ° C and TG ° C and between TG ° C and room temperature in a plurality of steps. And then cooled, the bare chip I
This has the effect of further suppressing the warpage of the substrate on which C is mounted.

Further, by sealing and curing a plurality of bare chip ICs on the substrate, pinholes on the surface of the sealing resin and warping of the substrate on which the bare chip ICs are mounted are prevented from occurring. A plurality of bare chip ICs can be heat-cured at a time.

Further, when the liquid resin contains a composition containing a thermosetting epoxy novolak compound, the resin has an effect of improving electrical insulation, heat resistance and water absorption after heat curing.

Further, since the wire connecting the bare chip IC and the substrate is disposed inside the filler rich layer of the liquid resin, there is an effect of preventing the occurrence of wire breakage.

[Brief description of the drawings]

FIG. 1 is a diagram showing a temperature profile in a liquid resin sealing and curing method according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing a temperature profile in a conventional liquid resin sealing and curing method.

FIG. 3 is an explanatory diagram showing a configuration in which a bare chip IC is sealed with a liquid resin by liquid resin heating and curing.

FIG. 4 is an enlarged view of FIG. 3;

5 is a diagram showing a viscosity change due to temperature of the liquid sealing resin.

FIG. 6 is a view showing that a liquid resin is separated at a time of T1 ° C. for a certain period of time.

[Explanation of symbols]

1 substrate, 2 bare chip IC, 3 die bond, 4
Liquid sealing resin, 5 diffusion prevention cell, 6 wires, 7
Pinhole, 8 hardener rich layer, 9 filler rich layer, 10 boundary.

Continuation of front page (56) References JP-A-1-297831 (JP, A) JP-A-3-85736 (JP, A) JP-A-4-111388 (JP, A) JP-A-4-329110 (JP) JP-A-5-335361 (JP, A) JP-A-6-64016 (JP, A) JP-A-5-57846 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB (Name) H01L 21/56

Claims (6)

(57) [Claims] In a liquid resin sealing and curing method for sealing and curing a bare chip IC mounted on a substrate with a liquid resin containing a thermosetting epoxy compound, a step of holding the liquid resin at a temperature at which the liquid resin is thermally cured. And a step of maintaining the substrate at a temperature above and below the glass transition temperature of the substrate. 2. A liquid resin sealing and curing method for sealing and curing a bare chip IC mounted on a substrate with a liquid resin containing a thermosetting epoxy compound at a temperature at which the viscosity of the liquid resin sharply decreases. A liquid resin encapsulation and curing method, comprising: a step of holding, a step of holding at a temperature at which the liquid resin thermally hardens, and a step of holding at a temperature above and below a glass transition temperature of the substrate. . Wherein the step of holding at a temperature of up and down in which the glass transition temperature of the substrate at the boundary is divided into a plurality and performing stepwise claim 1 or a liquid resin sealing according to claim 2 Curing method. 4. A liquid resin sealing curing method according to any one of claims 1 to 3 a plurality of bare chips IC on the board, characterized in that to seal cure. 5. The liquid resin sealing curing method according to any one of claims 1 to 3 liquid resin is characterized by containing a composition component containing a thermosetting epoxy novolac compound. 6. The liquid resin sealing and curing method according to claim 2 , wherein a wire connecting the bare chip IC and the substrate is disposed inside the filler rich layer of the liquid resin.