Plastic article or earthenware shaping or treating: apparatus – Distinct means to feed – support or manipulate preform stock... – Opposed registering coacting female molds
Reexamination Certificate
2000-02-02
2001-08-21
Davis, Robert (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Distinct means to feed, support or manipulate preform stock...
Opposed registering coacting female molds
C249S095000, C425S544000, C264S272150, C264S272170
Reexamination Certificate
active
06276913
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mold for resin sealing (hereinafter referred to as “resin sealing mold”) and more particularly to a resin sealing mold which can smoothly release a package and prevent resin from remaining.
2. Description of the Related Art
A package for constituting the appearance of a semiconductor device has conventionally manufactured in the following manner.
First, a resin sealing mold having a cavity is arranged on a resin sealing region of a lead frame. Thereafter, the cavity is filled with resin, and the filled resin is hardened by heating to form a package.
The surface of the cavity of such a resin sealing mold is satin-finished so that the package can be smoothly released from the cavity. The satin-finished surface can be formed by discharging processing and sandblasting for the cavity surface. The cavity having a satin-finished surface is disclosed in e.g. JP-A-6-143360.
However, in recent years, a package having a structure in which an external leads is exposed from a bottom of the sealing resin, such as “SON” (Small Outline Non-leaded) or “QFN” (Quad Flat Non-leaded) has been developed for commercial use. In such as structure, a bottom surface of the leads is exposed from the bottom surface of the package so that the bottom surface of the leads can be contacted to a wiring layer of an outer circuit such as printed circuit board. Therefore these structure has an advantage that mounting area can be reduced. However, where the package having a SON structure or QFN structure is made by resin sealing using the mold with the cavity surface satin-finished, resin remains on the exposed external leads which may lead to connection failure in packaging.
FIG. 7
is a sectional view of a conventional mold structure which shows the manner of deposition of resin on an external lead. As seen from the figure, in the case of using the conventional mold, the external lead
18
is placed on a satin-finished region
24
, and a minute space M is formed between the external lead
18
and a mold
100
. When resin sealing is executed in such a state, the sealing resin injected into the cavity
14
invades the above minute space M, i.e. areas indicated by arrow in
FIG. 2
so that the resin is deposited on the surface of the external lead
18
. Thereafter, when the mold
100
is hardened by heating, the resin deposited on the external lead
18
is also hardened as it is so that it remains on the external lead
18
after the package is released from the mold . This remaining resin may leads to connection failure in packaging.
On the other hand, the satin-finished region formed on the surface of a cavity
14
is an important component for smoothly releasing a package so that such a region as wide as possible are preferably formed. Accordingly, it is necessary to prevent the resin from being deposited on the external lead while the satin-finished region is left.
Thus, in a semiconductor device such as the SON structure or QFN having a structure in which external leads are exposed from a bottom of the sealing resin, the portion of the leads embedded into the sealing resin is relatively short so that it is difficult to assure sufficient contact between the external leads and the resin. Therefore, great force applied to the external leads when the package is released may give rise to falling out of the lead. The resin deposited on the rear face of the external leads may lead to connection failure of the package.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a reliable resin sealing mold which permits a package to be smoothly released without applying force to the lead and prevents resin from remaining on the lead.
In accordance with the first aspect of the present invention, a resin-sealing mold used for resin-sealing a semiconductor chip, having a cavity
14
for mounting a semiconductor chip
10
is loaded, is characterized in that said cavity comprises external lead placing regions
20
where external leads of said lead frame are placed; a mirror-face region
22
formed in at least said external lead placing regions; and a satin-finished region
24
formed in at least a portion of the other region than the mirror-face region
22
.
Because of these configurations according to the first aspect, it is possible to provide a reliable resin sealing mold which permits a package to be smoothly released without applying force to the lead and prevents resin from remaining on the lead.
In a second aspect of the invention, the resin-sealing mold according to the first aspect is characterized in that said mirror-face region is composed of the external lead placing regions and areas surrounding the periphery thereof.
In a third aspect of the invention, the resin-sealing mold according to the first aspect is characterized in that said mirror-face region
22
surrounds the periphery of said external lead placing regions over a width of 0.1 mm or more.
In a fourth aspect of the invention, the resin-sealing mold according to the first aspect is characterized in that said mirror-face region
22
is formed over the entire periphery of a lower surface of the cavity.
Because of these configurations according to the fourth aspect, even when external leads are formed with a minute pitch, it is possible to prevent the external leads from being brought into contact with the satin-finished region owing to misalignment.
In a fifth aspect of the invention, the resin-sealing mold according to the first aspect is characterized in that said mirror-face region
22
is formed partially over the periphery of a lower surface of the cavity.
In this configuration, since at least a portion of the periphery of the lower surface of the cavity is satin-finished, the release of a package is improved while deposition of resin is prevented.
In a six aspect of the invention, the resin-sealing mold according to the first aspect is characterized in that said cavity has a rectangular or square lower surface, and said mirror-face region
22
is formed in the other region than corners of the rectangular or square lower surface.
In this configuration, since the satin-finished region is formed at the corners, the release of a package is further improved while deposition of the resin is prevented.
In a seventh aspect of the invention, the resin-sealing mold according to the first aspect is characterized in that said resin-sealing mold is used for forming a semiconductor device with external leads which are exposed at a bottom of sealed resin.
In a semiconductor device having a structure in which are external leads are exposed from a bottom of the sealing resin, the portion of the lead embedded into the sealing resin of the lead is relatively short so that it is difficult to assure sufficient contact between the lead and the resin. The resin deposited on the rear face of the external leads may lead to connection failure of the package. The invention provides a reliable semiconductor device which permits the package to be taken out from the mold with no great force being applied and is free from connection failure.
In an eighth aspect of the invention, the resin-sealing mold according to the first aspect is characterized in that said resin-sealing mold is used for a semiconductor device having an SON structure.
In a ninth aspect of the invention, the resin-sealing mold according to the first aspect is characterized in that said resin-sealing mold is used for a semiconductor device having a QFN structure.
In a tenth aspect of the invention, the resin-sealing mold according to the first aspect is characterized in said semiconductor chip is mounted on a die pad of a lead flame and a mirror-face region is formed in said external lead placing regions and a region for placing the die pad.
In an eleventh aspect of the invention, the resin-sealing mold according to the first aspect is characterized in said semiconductor chip is placed on a part of an inner surface of the cavity and a mirror-face region is formed in the part and said external lead placing r
Mikawa Masanori
Mitsui Masanori
Davis Robert
Greenblum & Bernstein P.L.C.
Mitsui High-Tech Inc.
LandOfFree
Mold for resin sealing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Mold for resin sealing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mold for resin sealing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2454555