JPH11243164A - Semiconductor plastic package and surface mounting method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor plastic package and a surface-mounting method thereof, wherein the semiconductor plastic package can be enhanced in temporary fixing strength to a wiring board without spoiling assembling properties. SOLUTION: Recesses 13 are provided at least to a part of a base 11a of a package main body 11, an adhesive agent 14 is applied to the part where the recesses 13 are provided, the contacting surface of the package main body 11 with the adhesive agent 14 can be improved in area, and by having the package main body 11 fixed temporarily to a wiring board 12, the package main body 11 can be improved in adhesive strength with respect to the wiring board 12. The base 11a of the package main body 11 is kept high in flatness by its part other than the recesses 13, so that the package main body 11 will not produce nonconformities a process or sure mounting properties will not be spoiled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor plastic package in which an adhesive is interposed between a package main body and a wiring board during surface mounting to temporarily fix the package main body on the wiring board and a surface thereof. Regarding implementation method.

[0002]

2. Description of the Related Art Conventionally, in mounting a semiconductor plastic package on a wiring board, a lead portion is inserted into a through hole formed in a land portion of the wiring board and soldered. There is surface mounting in which the tip of the lead portion is placed and soldered. The surface mounting has a higher mounting density than the insertion mounting, and is known as a mounting form effective for space efficiency and reduction of signal delay time.

In a surface mounting method for a semiconductor plastic package, a predetermined amount of solder paste is applied in advance to a land portion of a wiring board using a screen printing technique or the like, and a lead portion of the plastic package is mounted on the land portion. Then, this technique is to solder the land and the lead by melting the solder. Therefore, in the double-sided mounting in which the plastic package is mounted on both sides of the wiring board, in order to prevent the plastic package located on the lower surface of the wiring board from falling off the wiring board before soldering,
Usually, the bottom of the package body and the wiring board are fixed with an adhesive, and the plastic package is temporarily fixed to the wiring board.

[0004]

However, there is a problem of insufficient strength of the temporary fixing between the plastic package and the wiring board. With conventional general plastic packages, the bottom surface of the package body, which is the surface to which the adhesive is applied, is a flat surface. Therefore, the temporary fixing strength becomes insufficient.

Japanese Patent Laid-Open Publication No. Hei 4-370960 discloses FIG.
As shown in FIG.
The protruding portion 3 protruding toward the lead portion 5 is formed with a length substantially equal to that of the lead portion 5, and the contact area between the package body 1 and the adhesive 4 is increased to improve the temporary fixing strength to the wiring board 2. I have.

However, the configuration in which the raised portion 3 is provided on the package body bottom surface 1a involves various problems in assembling. That is, firstly, if a part of the raised portion 3 is damaged or dropped for some reason, the chipped portion causes dust and becomes a serious problem in the process. Second, the IC tray, carrier tape, transport surface And the like, if the package main body bottom surface 1a is not flat, it is difficult to position the package main body and high-precision processing cannot be performed. ) Cannot be ensured, and in some cases, there is a problem that contact between the lead portion 5 and the land portion 6 is hindered by the raised portion 3 during mounting, and accurate mounting cannot be performed.

The present invention has been made in view of the above problems, and has as its object to provide a semiconductor plastic package and a surface mounting method thereof capable of increasing the strength of temporary fixing to a wiring board without impairing the assemblability. .

[0008]

According to the present invention, a plurality of recesses are formed in at least a part of a bottom surface of a package body, and an adhesive is applied to a portion where these recesses are formed to form a package body and an adhesive. The temporary contact with the wiring board is performed by increasing the contact area between them, thereby increasing the adhesive strength and improving the temporary fixing strength of the package body to the wiring board. In addition, since the flatness of the bottom surface of the package body is maintained at a surface other than the above-mentioned concave portion, there is no inconvenience in the process and the reliable mountability is not impaired.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a semiconductor plastic package according to an embodiment of the present invention. The package body 11 is molded from an epoxy resin material and has a semiconductor device inside. A lead portion 15 protruding from a side peripheral portion of the package body 11 is wire-bonded to an electrode portion of the semiconductor device inside the package body 11, and the semiconductor device is connected to a land portion on a wiring board (not shown) via the lead portion 15. Make an electrical connection.

In the vicinity of the center of the bottom surface 11a of the package body 11, a plurality of circular recesses 13 having a diameter of, for example, about 0.1 mm are formed as shown in FIG. Recess 13
Can be easily formed by providing a projection on a part of the molding surface of the bottom molding die of the package body 11. The size and number of the recesses 13 can be set as appropriate, and are determined in consideration of the size and weight of the package body 11. Further, the formation area of the recess 13 is not limited to the vicinity of the center of the bottom surface 11 a of the package body 11,
It may be formed on the entire bottom surface 11a.

Therefore, as shown in FIG. 3, when the package body 11 is temporarily fixed to the wiring board 12 using an adhesive (epoxy adhesive) 14 as a temporary fixing agent, a portion where the recess 13 is formed is formed. If the adhesive 14 is to be applied, the adhesive enters the recess 13 and the bottom surface 11 of the package body 11 is formed.
The anchoring effect (anchor effect) is increased by increasing the contact area between a and the adhesive 14, and the bonding strength between the package body 11 and the adhesive 14 is improved. Thereby, it is possible to prevent the package body 11 from falling off from the wiring board 12. Further, even if fine dust and the like are present on the wiring board 12, an opportunity to store the dust and the like in the recess 13 can be given to reduce the risk of mounting failure.

Further, according to the present embodiment, since the recess 13 is formed on the bottom surface 11a of the package body 11, the bottom surface 11a can maintain the flatness on a surface other than the recess 13. Thereby, the positioning accuracy of the plastic package on the IC tray, the carrier tape, the transfer surface, and the like is not impaired, and the distance (stand-off) between the wiring board 12 and the package body bottom surface 11a is not changed at all. The mounting on the wiring board 12 can be performed in a short time, and reliable mounting can be performed.

Although the embodiments of the present invention have been described above, the present invention is, of course, not limited thereto, and various modifications can be made based on the technical concept of the present invention.

For example, in the above embodiment, QFP (Q
(Ud Flatpackage Package) type semiconductor plastic package has been described as an example.
Not limited to this, SOP (Small Outlin)
e Package) or QFJ (Quad Flatp)
For other surface mount plastic packages such as ack J-leaded package) type,
The present invention is applicable.

In the above embodiment, the shape of the recess 13 is circular. However, the present invention is not limited to this, and the same effect can be obtained by forming the recess 13 into various shapes such as a square shape or a random shape. Is possible.

[0017]

As described above, according to the semiconductor plastic package and the surface mounting method of the present invention, since a plurality of recesses are formed in at least a part of the bottom surface of the package body, these recesses are formed. By applying an adhesive to the portion to be temporarily fixed to the wiring board, the contact area between the package body and the adhesive can be increased, and the temporary fixing strength of the package body to the wiring board can be improved. it can. In addition, since the bottom surface of the package body can maintain the flatness on the surface other than the concave portion, there is no inconvenience in the process and the reliability of the mounting is not impaired.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a bottom surface of a semiconductor plastic package according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a portion A in FIG.

FIG. 3 is a sectional view showing the same operation.

FIG. 4 is a cross-sectional view showing a mounting form of a conventional semiconductor plastic package.

[Explanation of symbols]

11 Package body, 11a Bottom surface, 12
…… Wiring board, 13 …… Recess, 14 …… Adhesive, 1
5 ... Lead part.

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI H05K 7/12 H05K 7/12 M

Claims (3)

[Claims] A package body having a semiconductor device therein; and a lead portion projecting from a side peripheral portion of the package body and being surface-mounted on a wiring board arranged to face a bottom surface of the package body. A semiconductor plastic package, wherein a plurality of recesses are formed in at least a part of a bottom surface of the package body. 2. The method according to claim 1, wherein the plurality of recesses are formed by a plurality of protrusions provided on at least a part of a mold forming surface of a mold for forming a bottom surface of the package body. Semiconductor plastic package as described. 3. A package body having a semiconductor device therein, and a lead portion projecting from a side peripheral portion of the package body and being surface-mounted on a wiring board disposed to face a bottom surface of the package body, In a surface mounting method of a semiconductor plastic package, wherein an adhesive is interposed between the bottom surface and the wiring substrate to temporarily fix the package body to the wiring substrate, a plurality of portions of the bottom surface to which the adhesive is applied are provided. A surface mounting method for a semiconductor plastic package, wherein a recess is formed in advance.