JPH0740391A - Manufacture of base for small electronic parts whose warp is reduced - Google Patents

Abstract

PURPOSE:To provide a manufacture enabling a reduction of a warp to be generated at the time of manufacturing of a base for small electronic parts of a thin flat plate molded product. CONSTITUTION:To obtain a manufacture of a base plate which has reduced a warp and is for small electronic parts wherein the base plate is manufactured by making use of a film gate by injection-molding a liquid crystal polymer and a mold possessing a runner which is allowed to branch off into two pieces or not less than that is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing method capable of reducing warpage that occurs when manufacturing a substrate for a small electronic component which is a thin flat plate molded product.

[0002]

2. Description of the Related Art Conventionally, when a thin flat plate molded article is manufactured from an engineering plastic such as a polycarbonate resin, the resin is injected into a cavity by a film gate having one runner so as to reduce the warp. . When manufactured by this method, the resin flows out from the film gate almost at the same time, so that the temperature distribution and the pressure distribution are uniform in the cavity, so that the amount of warpage can be reduced.

Substrates for small electronic components are manufactured by the same method as described above. A conventional technique for manufacturing a substrate for a small electronic component will be described with reference to FIG. When manufacturing a substrate for small electronic parts using liquid crystal polymer or liquid crystal polymer containing reinforcing material, it is necessary to consider the orientation direction of molecules and the orientation direction of reinforcing material in addition to the uniform temperature distribution and pressure distribution. There is. this is,
In the case of a liquid crystal polymer, the shrinkage rate varies greatly depending on the orientation direction of the molecule and the orientation direction of the reinforcing material. Therefore, if the orientation direction of the molecule and the orientation direction of the reinforcing material become non-uniform, the maximum shrinkage direction is This is because the molded product does not shrink in a similar shape and the amount of warpage increases as a result.

For the above reasons, the conventional substrate for small electronic components is manufactured by using the film gate having one runner to make the temperature distribution and the pressure distribution uniform, and the molecular orientation direction and the reinforcing material orientation direction are made uniform. I was trying to make it uniform. That is, the liquid crystal polymer is injected into the small electronic component substrate 1 from the runner 21 and the thick portion 3 through the film gate 4. However, when a substrate for small electronic components, which is a thin flat plate molded product, is manufactured by the conventional technique of injecting a liquid crystal polymer from the film gate 4 having one runner 21,
The problem is that the warp becomes large.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art and to provide a substrate for a small electronic component in which the amount of warpage is reduced.

[0006]

The inventors of the present invention have conducted extensive studies on a method of manufacturing a substrate for a small electronic component, and as a result, as a means for injecting a liquid crystal polymer into a cavity, two or more runners are used. The present invention has been completed by finding that the amount of warpage can be reduced by using the film gate that the present invention has. That is, the present invention is a method of manufacturing a substrate using a film gate by injection molding a liquid crystal polymer.
A method for manufacturing a substrate for a small electronic component, characterized in that a die having a book or a runner branched into more than two is used. Further, in the present invention, a die having a thickness of the film gate of 0.1 to 3.0 mm is used, and a die having the same branch length and the corresponding cross-sectional shape at the same flow distance is used. Is a method of manufacturing a substrate for a small electronic component.

To facilitate understanding of the present invention, description will be given with reference to the accompanying drawings. FIG. 1 shows a substrate and a runner portion for a small electronic component obtained by manufacturing a liquid crystal polymer. A film gate 4 is provided on the substrate 1 for small electronic components, and liquid crystal polymer is injected from the two runners 21 and 22 and the thick portion 3 through the film gate 4. FIG. 2 is a sectional view taken along line AA of FIG. Figure 3 shows four runners
A small electronic component substrate and a runner portion obtained by injecting a liquid crystal polymer from a film gate 4 having 21, 22, 23, and 24. FIG. 4 shows a conventional method, which is a small electronic component substrate and a runner portion obtained by injecting a liquid crystal polymer from a file gate having one runner.

In the present invention, the number of runners for injecting the liquid crystal polymer into the film gate is two or more. Here, the number of runners depends on the film gate width and thickness. For example, in the case shown in Fig. 1, when the film gate length is 150 mm and the gate thickness is 1.0 mm, the number of runners is 2 to 4
Is preferred. As the number of runners increases, the warp can be reduced.

In the film gate having one runner shown in FIG. 4, when a thin flat plate molded article is manufactured by using ordinary engineering plastics, it is possible to reduce the warpage, though it is possible to reduce the warpage. It is considered that the reason why the amount of warp becomes large even if the substrate for a small electronic component made of a liquid crystal polymer is produced by the method is due to the characteristic property of the liquid crystal polymer. At the temperature at the time of melt molding, the liquid crystal polymer has a higher shear rate dependence of the viscosity than ordinary engineering plastics, and the viscosity rapidly increases as the shear rate decreases.
Further, the liquid crystal polymer has a smaller specific heat and a higher thermal conductivity than ordinary engineering plastics, and therefore has a high cooling rate. Due to the above properties, once the liquid crystal polymer has a reduced flow velocity in the cavity, the viscosity of the liquid crystal polymer increases rapidly even if there is no temperature decrease, making it difficult to flow. Due to the peculiar properties of this liquid crystal polymer, it is considered that the warpage was large even if it was manufactured using the conventional technique of injecting the liquid crystal polymer from a film gate having one runner.

That is, when manufactured by using the conventional technique shown in FIG. 4, after the liquid crystal polymer is injected from the runner 21 into the thick portion 3, the thick portion 3 has a higher pressure loss than the film gate 4. Since it can progress even if there is little, it preferentially progresses in the lateral direction of the thick portion 3. At this time, the flow velocity of the liquid crystal polymer near the film gate 4 at the tip of the runner 21 decreases, and the viscosity remarkably increases. On the other hand, at the left and right ends of the film gate 4 which are separated from the runner 21, the flow velocity of the liquid crystal polymer is kept high, and the decrease in viscosity is extremely small.
A large amount of the liquid crystal polymer is injected into the cavity from a portion distant from the runner 21, and less is injected from a portion corresponding to the tip of the runner 21. In other words, the progress direction of the liquid crystal polymer in the cavity is slower in the central part and faster in both ends with respect to the film gate. As a result, the molecular orientation direction and the reinforcing material orientation direction are not uniform. Furthermore,
Since the flow velocity is reduced in the vicinity of the film gate 4 in the central portion, which is the tip of the runner 21, the shear heat generation is reduced in the central portion of the molded product, and the liquid crystal polymer flows once in the cooled state, so the temperature becomes low and the small electronic The temperature distribution on the component board becomes non-uniform. From the above reason, it is considered that the warp amount becomes large.

On the other hand, when the number of runners supplying the liquid crystal polymer to the film gate of the present invention shown in FIGS. 1 and 2 of the accompanying drawings becomes two, the liquid crystal polymer exits the runners 21 and 22 and the film gate 4 As the thickness decreases as the
The flow velocity near the film gate at the tips of 21 and 22 decreases, and spreads preferentially left and right along the thick portion. However, since the number of runners is two, the runner interval is short and the time required for filling the thick portion 3 immediately before the film gate with the liquid crystal polymer is short. As a result, the time for the liquid crystal polymer to approach the vicinity of the film gate is shortened, and the difference in the arrival time of the liquid crystal polymer in each part of the film gate is reduced. This makes it possible to suppress a decrease in the shear rate of the liquid crystal polymer near the runner and prevent an increase in viscosity due to a decrease in temperature of the cooling time difference, and as a result, the viscosity of the entire film gate becomes uniform. Therefore, the flow front shape of the liquid crystal polymer in the cavity is parallel to the film gate, so the molecular orientation direction and the reinforcing material orientation direction are uniform, and the temperature distribution and pressure distribution are also uniform. It has been found that it is possible to reduce.

As shown in FIG. 3, when the number of runners is increased to 4, the time required for filling the thick portion just before the film gate with the liquid crystal polymer is further shortened, and the liquid crystal polymer in each portion of the film gate is shortened. Since the arrival time difference is small, it is possible to suppress the decrease in the shear rate of the liquid crystal polymer near the runner and prevent the increase in the viscosity due to the decrease in the cooling time difference temperature. As a result, the viscosity of the entire film gate is It is possible to make it more uniform than 2.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments will be described below with reference to the drawings. Example 1 FIG. 1 shows a small electronic component substrate and a runner obtained by producing a liquid crystal polymer by the production method of the present invention. The shape of small electronic components is 160 mm × 75 mm × 1.1 mm. FIG. 2 is a sectional view of the first embodiment. The film gate thickness is 1.0 mm. Molding conditions are: initial resin temperature 380 ℃, mold temperature 80
℃, filling time 0.4 seconds. When manufactured by the manufacturing method of the present invention, the warp in the longitudinal direction of the substrate after anneal at 150 ° C. for 20 minutes was 2.1 mm on average, which was sufficient accuracy.

Comparative Example 1 FIG. 4 shows a small electronic component substrate and runner obtained by manufacturing a liquid crystal polymer by a conventional manufacturing method. The shape and molding conditions of the substrate for a small electronic component are the same as in Example 1.
The substrate for a small electronic component manufactured by the conventional method had an average warpage of 3.6 mm under the same conditions as in Example 1.

[0015]

As a means for producing a substrate for a small electronic component with a liquid crystal polymer having a large anisotropy, a high shear rate dependence of viscosity, a small specific heat and a large thermal conductivity, When using the manufacturing method of injecting from the film gate having the gate of, the orientation direction of molecules, the orientation direction of the reinforcing material, the temperature distribution and the pressure distribution become uneven at each point on the small electronic component substrate which is a thin flat plate molded product. Therefore, there is a problem that the warp amount is large. On the other hand, the manufacturing method according to the present invention uses a manufacturing method in which a liquid crystal polymer is injected from a film gate having two or more runners, whereby a molecular orientation direction, a reinforcing material orientation direction, a temperature distribution and a pressure distribution are obtained. It is possible to reduce the warp by making uniform.

[0016]

[Brief description of drawings]

FIG. 1 is a perspective view showing a substrate and a runner for a small electronic component in the case where the number of runners is 2 in Embodiment 1. FIG.

FIG. 2 is a cross-sectional view showing a cross section of a substrate for a small electronic component according to a first embodiment.

FIG. 3 is a perspective view showing a small electronic component substrate and a runner when the number of runners is four.

FIG. 4 is a perspective view showing a conventional small-sized electronic component substrate and runner of Comparative Example 1.

[Explanation of symbols]

 1: Substrates for small electronic components 21, 22, 23, 24: Runner 3: Thick part 4: Film gate

Claims (3)

[Claims] 1. A method of manufacturing a substrate using a film gate by injection-molding a liquid crystal polymer, wherein a mold having two or more branched runners is used. Reduced manufacturing method for substrates for small electronic components 2. The thickness of the film gate is 0.1 to 3.0 mm
The method for manufacturing a substrate for a small electronic component according to claim 1, wherein a mold that is 3. The method for manufacturing a substrate for a small electronic component according to claim 1, wherein a mold having the same sectional shape at the same run length and the length of the branched runner is used.