JP2771838B2 - Resin sealing method for electronic components, molding die for resin sealing, and electronic component sealing molded product - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a resin-encapsulated molded product of an electronic component, a mold for encapsulation for producing the same, and a resin-encapsulating method. The present invention relates to a technique that is extremely useful for reducing defects in a manufacturing process of a sealed molded product.

[Conventional technology]

Generally, in the manufacturing process of a resin-encapsulated molded product of an electronic component, an electronic component, a lead frame, and the like, which are sealed between an upper mold and a lower mold of a molding die, are sandwiched so as to fit in the cavity, and one part of the cavity is formed. The package is formed by injecting a resin as a sealing material from a gate opened on a side wall and solidifying the resin to form a package.

Here, epoxy resin which is a thermosetting resin is often used as a resin as a sealing material, and a so-called transfer molding method or the like is employed as a manufacturing method. Often used. In the case of using a thermoplastic resin, an injection molding method is generally employed.

[Problems to be solved by the invention]

However, each of such prior arts has a problem. Hereinafter, the problem will be described using a thermoplastic resin sealing step as an example.

In the encapsulation molding step, the molten thermoplastic resin starts to be cooled at the same time as being injected into the mold, the viscosity increases, and finally reaches solidification, and as it approaches the center of the flow path, It is in a flowable state without solidification until the latest.

On the other hand, in the filling process, an injection pressure of usually about 200 kgf / cm ² is set in the molding machine as a pressure for filling the resin, but it is accompanied by the flow before the filling of the resin into the mold cavity is completed. There is a pressure drop, and the pressure near the tip of the substantially flowing resin is much lower than the set pressure of the injection molding machine.

When the filling is completed, the process starts to compress the resin. In this process, the resin is supplemented by the compressed volume in the process of the resin being compressed to the set pressure of the molding machine from the side near the gate in the resin flow path in the mold. That is, the resin flows at a pressure much higher than the resin pressure before the completion of the filling. In the subsequent pressure-holding process, the volume contraction due to the solidification of the resin is also compensated. In this dwelling process, a relatively high pressure is required to prevent sink marks and voids. Since these fillings are performed at a high pressure, the resin which has been cooled to a certain extent and which has increased the viscosity is caused to flow, and is performed through the resin passage, ie, the center of the cavity, where cooling is most delayed.

Since the electronic component to be sealed is generally placed at the center of the cavity, the electronic component is deformed / destructed, displaced, and the bonding wire falls due to the resin pressure and the flow of the thickened resin in the above-described refilling process. In many cases, defects such as wire breakage and disconnection occurred.

[Means for solving the problem]

In view of the problems of the prior art, the present inventors have made intensive studies and as a result, have found that in a mold for obtaining a sealed molded product, the formerly uniform cavity depth is partially changed. By providing a step or a core in a part of the cavity for the purpose, by controlling the location and direction of resin flow and resin pressure at the time of resin supplement, products with few defects such as misalignment and broken bonding wire Was obtained, and the present invention was completed.

That is, the present invention provides a step or a core at a part of a resin inflow path in a cavity to a gate side end surface of an electronic component installed in a molding die cavity when resin sealing an electronic component. A resin sealing method for electronic components, characterized by controlling the solidification rate of the sealing resin, the distribution of resin pressure, and the inflow path, a resin sealing molding die used directly in the method, and Electronic component encapsulation molded product to be obtained.

 The present invention will be described below with reference to the accompanying drawings.

FIG. 12 shows a process of flowing resin into the cavity.

A one-dot chain line 11 in FIG. 12 represents the leading end of the flow of the molten resin, and the molten resin advances from the gate 3 side to the opposite gate side.

In the filling process, the electronic component (IC chip 6) to be sealed receives a force in the resin inflow direction 9a, and this force is the resin pressure applied to the gate-side end surface 6a of the electronic component. Here, in the filling process, assuming that a material having a sufficiently low viscosity in a molten state is selected, the resin pressure is small as described above, and no displacement of the electronic component occurs.

After the filling is completed, the electronic component receives the high injection pressure and the holding pressure set in the injection molding machine as described above as the resin pressure from all directions around the electronic component, but as shown in FIG. Considering this, the resin pressures applied to the symmetrically filled portions like 6c and 6d cancel each other out, so that defects such as displacement do not occur. On the other hand, in the case of the gate-side end surface 6a and the counter-gate-side end surface 6b of the electronic component, the resin inflow paths from the gate to them are different, and the degree of cooling is also different. There is a difference between the resin pressure applied to the side end surface 6a and the resin pressure applied to the non-gate side end surface 6b, which causes a defect such as displacement.

As described above, a step or a core is provided in a part of the cavity, particularly in a part of the resin inflow path to the gate side end surface 6a of the electronic component to which a high resin pressure is applied, whereby the flow path in that part is provided. By narrowing the pressure, the pressure loss is increased, the cooling is promoted, the magnitude of the resin pressure on the opposite end face and the time of application can be balanced, and the displacement and the like can be prevented.

Also, by providing a step or a core to narrow the flow path, the resin inflow path itself can be changed, and the sealed electronic component can be placed in a place where the thickened resin can flow from the resin compression process to the pressure holding process. It can also be considered not to put in. Further, it is possible to exert an effect on a material having a different resistance depending on the direction of the force, such as a broken wire of a bonding wire. When viewed as a simple model, the bonding wire 7 is an arch-shaped bent beam with both ends fixed or hinged, and is weak against a force in a direction of being laid down like 9b in FIG. Since it shows stronger resistance to the forces 9c, 9d and the lifting force 9e, by changing the resin inflow path by providing a step or a core and filling the resin from the direction like 9c, 9d, it is possible to reduce the collapse fault. Can be reduced.

The shape and position of the core and the step provided in the mold cavity according to the present invention are not particularly limited. For example, even if a single protrusion is formed in the longitudinal direction as in Example 1 described later, A concave portion may be formed in the cavity, a circular core may be formed, or a plurality of cores may be formed in one cavity.

Further, the sealing resin used in the present invention is not particularly limited,
A melt-processable polyester (liquid crystalline polyester) capable of forming an anisotropic molten phase, especially an aromatic polyester or an aromatic polyester amide containing an aromatic hydroxycarboxylic acid group or an aromatic hydroxyamine group as at least one component of the resin component; Polyarylene sulfide represented by polyphenylene sulfide, polyamide, polyether sulfone, polysulfone, polyether imide,
Thermoplastic resins such as polyetheretherketone are exemplified. These thermoplastic resins can be used alone or in combination of two or more.

These thermoplastic resins may be supplemented with other thermoplastic resins.

The thermoplastic resin used in this case is not particularly limited, but examples thereof include polyethylene, polyolefin such as polypropylene, polyethylene terephthalate, aromatic dicarboxylic acid such as polybutylene terephthalate and aromatic polyester comprising diol or oxycarboxylic acid and the like. , Polyacetal (homo or copolymer), polystyrene, polyvinyl chloride, polyamide, polycarbonate, ABS, polyphenylene oxide, fluororesin and the like. These thermoplastic resins can be used as a mixture of two or more kinds.

The molding material suitable for the present invention has a mechanical strength and can be molded at a low pressure, and as described above, can be filled with a large amount of an inorganic filler in order to make the linear expansion coefficient as close as possible to that of a metal. It is preferable that the melt viscosity is as low as possible. From these points, a melt-processable polyester (liquid crystalline polyester) capable of forming an anisotropic molten phase, particularly an aromatic polyester having an aromatic hydroxycarboxylic acid group or an aromatic hydroxyamine group as at least one component of the resin component or Polyarylene sulfide represented by aromatic polyester amide and polyphenylene sulfide is most preferably used.

The thermoplastic resin for electronic component sealing used in the present invention,
Various inorganic and organic fillers can be contained in order to improve the strength and the like within a range not to impair the object of the present invention. For example, a substance to be added to a general thermoplastic resin, that is, a fibrous, powdery, or plate-like filler is used.

Examples of the fibrous filler include inorganic fibers such as glass fiber, asbestos fiber, silica fiber, silica / alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, and titanium fibrous material. Substances. In addition, high-melting-point organic fibrous substances such as wholly aromatic polyamide fibers, aromatic liquid crystalline polyester fibers, and phenolic fibers can be used in the same manner as the inorganic fibrous filler.

On the other hand, the powdery fillers include carbon black, silica, quartz powder, glass beads, glass powder, calcium silicate, aluminum silicate, kaolin, talc, clay,
Silicates such as diatomaceous earth, wollastonite, oxides of metals such as iron oxide, titanium oxide, zinc oxide and alumina, carbonates of metals such as calcium carbonate and magnesium carbonate, metals such as calcium sulfate and barium sulfate Sulfate, silicon carbide, silicon nitride, boron nitride and the like.

Examples of the plate-like filler include mica and glass flake.

These inorganic fillers can be used alone or in combination of two or more.

When using these fillers, it is desirable to use a sizing agent or a surface treatment agent if necessary. This example is a functional compound such as an epoxy compound, an isocyanate compound, a silane compound and a titanate compound. These compounds may be used after being subjected to a surface treatment or a convergence treatment, or may be added at the same time as the preparation of the material. 95% by weight of resin used for inorganic and organic fillers
Hereinafter, it is preferably 20 to 75% by weight.

Further, in order to improve various properties such as mechanical, electrical and chemical properties and flame retardancy, various additives and reinforcing agents can be added as needed.

〔The invention's effect〕

As described above, according to the present invention, it is possible to obtain a product having few defects such as displacement, deformation, and broken bonding wire of the electronic component to be sealed.

〔Example〕

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.

Example 1 and Comparative Example 1 Hereinafter, an example of the present invention will be described with reference to FIGS.

FIG. 1 is a perspective view showing a state where a printed board 2 on which an electronic circuit to be sealed is formed is inserted into a lower mold 1a using a conventional sealing mold. FIG. 2 is a sectional view taken along the line AA of FIG.
FIG. 3 is a sectional view taken along line BB of FIG. 1. The dimensions of this mold in the longitudinal direction of the cavity are 20 mm, the width direction is 7 mm, and the depths of the lower and upper mold cavities 4a and 4b are both
3 mm, and the gate 3 is opened in the lower mold.

When a resin composition in which 30% by weight of glass fiber was blended with a liquid crystalline polyester A described later as a sealing material was used to perform actual sealing molding with the above-mentioned mold, the lower cavity was slightly filled. In advance, the position indicated by 10a in FIG. 2 is filled last, and the process of compressing and filling the resin is performed along the arrow 9f, so that the printed board 2 is pushed up toward the upper mold. The force caused by this force caused a displacement.

The following countermeasures were taken for this mold based on the present invention.
That is, FIGS. 4 and 5 correspond to FIGS. 2 and 3, respectively, and as shown therein, the lower mold 4a has a length of 20 mm, a width of 4 mm,
A step (convex portion) 8 having a height of 1 mm was formed, and the product was designed to have a groove. As a result, the filling of the resin at the portion 10b in FIG. 5 precedes and the filling method is such that the resin flows into the lower surface of the printed board from both surfaces as indicated by the arrow 9g, and the filling is performed similarly. became. That is, since the compression of the resin on the lower surface of the print substrate is delayed and balanced with the compression of the resin on the upper surface of the print substrate, the displacement does not occur.

Example 2 and Comparative Example 2 Except for using a resin composition in which 40% by weight of glass fiber was blended with polyphenylene sulfide resin (manufactured by Kureha Chemical, Fortron KPS) instead of the liquid crystalline polyester in Example 1 and Comparative Example 1. Do exactly the same test,
Exactly the same results were obtained.

Embodiment 3 Next, another embodiment according to the present invention will be described with reference to FIGS.

FIG. 6 shows a conventional encapsulation mold, in which an IC is encapsulated.
FIG. 3 is a top view of a lower mold in a state where a lead frame on which the information is loaded is inserted. The cross-sectional view taken along the line CC and the line DD in FIG. 6 are shown in FIG. 7 and FIG. 8, respectively. The dimensions of this mold in the longitudinal direction of the cavity are 20 mm, the width direction is 7 mm, the depth of the lower mold cavity 4a is 2 mm, and the depth of the upper mold cavity 4b is 3 mm, and the gate 3 is opened in the upper mold.

As in Example 1, the encapsulation molding was performed using a resin composition in which 50% by weight of silica was mixed with the liquid crystalline polyester B described later.
In the figure, the portion 10c was filled last, and the resin was compressed and supplemented along the arrow 9h. Here, the IC chip 6 and the bonding wire 7 which are sealed as shown in FIG. 7 are located on the path 9h for compressing and refilling the resin, so that the bonding wire is broken, or severely broken, and furthermore, the IC chip is broken. Was swept away from the gate side. FIG. 9 shows a situation in which the bonding wire is bent in this mold. In this case, resin flows in from the left side of the figure. Such an inversion leads to a short circuit between adjacent wires.

FIGS. 10 and 11 show the result of taking measures against this mold according to the present invention, and FIGS.
Corresponding to the figure, in this case a part of the upper mold cavity
A core (convex portion) 8 having a size of 5 mm, a width of 10 mm, and a height of 2 mm was provided.

This gives priority to filling the lower mold cavity,
The 10d portion shown in FIG. 10 is filled at the end, and the resin is compressed and supplemented along the arrow 9i, so that the IC chip 6 and the bonding wire 7 to be sealed are moved from their path 9i. Disconnection and displacement of the IC chip have been eliminated, and the collapse of the bonding wire has been reduced.

The liquid crystalline polyester used in Examples and Comparative Examples has the following structural units.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a conventional molding die used in the production of an electronic component encapsulation molded product, in which a printed circuit board on which an electric circuit to be encapsulated is formed is inserted. It is. FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG.
It is BB sectional drawing of a figure. 4 and 5 show the sealing mold of FIG. 1 which has been subjected to measures according to the present invention. FIG. 4 is FIG. 2 and FIG. 5 is FIG. Each corresponds. FIG. 6 is a top view of a lower mold in a state where a lead frame on which an IC to be sealed is mounted is inserted in a conventional molding die for molding, similarly to FIG. FIG. 7 is a sectional view taken along line CC of FIG. 6, and FIG.
It is DD sectional drawing of the figure. FIG. 9 is the same top view as FIG. 6, but shows a state in which the bonding wire is bent by the resin flowing during the encapsulation molding. FIGS. 10 and 11 show the sealing mold of FIG. 6 subjected to the measures according to the present invention. FIG. 10 is shown in FIG. 7, and FIG. Corresponding. FIG. 12 is a perspective view schematically showing a state in which a resin is filled into a mold cavity in which an electronic component to be sealed is inserted, and FIG. 13 is a perspective view showing a periphery of a bonding wire. 1a Lower mold 2b Upper mold 2 Printed substrate to be sealed 3 Gate 4a Lower mold cavity 4b Upper mold cavity 5 Lead 6 IC chip 6a to 6d … IC chip side surface 7… Bonding wire 8… Core or step (convex portion) 9 a to 9 i… Arrows showing resin filling, compression and filling paths 10 a to 10 d… Part of cavity 11… Inflow One-dot chain line indicating the tip of the resin

Claims (4)

(57) [Claims] When a resin is sealed in an electronic component, a step or a core is provided in a part of a resin inflow path in the cavity to a gate-side end surface of the electronic component installed in a molding die cavity. A resin sealing method for an electronic component, comprising: controlling a solidifying speed, a distribution of a resin pressure, and an inflow path of the sealing resin. 2. The method according to claim 1, wherein the sealing resin is a liquid crystalline polyester or a polyarylene sulfide. 3. An electronic component molded article manufactured by the method according to claim 1. 4. A step or a core for controlling a solidifying speed, a resin pressure distribution and an inflow path of a sealing resin in a molding die cavity, a gate of an electronic component installed in the molding die cavity. A molding die for resin sealing of an electronic component provided on a part of a resin inflow path in a cavity to a side end surface.