Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame
Reexamination Certificate
2002-07-10
2003-09-16
Ho, Hoai (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
C257S692000, C257S735000, C257S676000, C257S690000
Reexamination Certificate
active
06621150
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an art of configuring the leads of a Lead Frame used in packaging integrated circuits, particularly for LOC (Lead on Chip) packages.
BACKGROUND OF THE INVENTION
In conventional processes of packaging an IC (integrated circuit), a lead frame
1
as shown in
FIG. 1
usually includes a plurality of leads separated into two groups respectively represented by reference numerals
11
and
12
, the group represented by reference numeral
11
including a line of outward ends represented by reference numeral
13
and a line of inward ends represented by reference numeral
15
, the group represented by reference numeral
12
including a line of outward ends represented by reference numeral
14
and a line of inward ends represented by reference numeral
16
, the leads in the two groups stretching to the outside of the lead frame
1
in opposite directions. The two lines of inward ends
15
and
16
, in order to match the size of an IC (under the lead frame
1
, not shown in the figure), must be inside a quadrilateral region
17
, and opposite to each other with a space
18
therebetween so that bonding wires
20
can be connected between bonding pad
100
of the IC and inward ends
15
or
16
. As shown in
FIG. 1
, the two lines of inward ends
15
and
16
are inside a quadrilateral region
17
which is located in the central portion of lead frame
1
, and are evenly dispersed between two parallel edges
171
and
173
of quadrilateral region
17
in two lines both perpendicular to the edges
171
and
173
while separated from each other by a distance
18
. The distance
18
is to let bonding wire
20
pass therethrough so that the inward ends
15
and
16
can be connected to bonding pads
100
of an IC.
For more information about structures of a conventional lead frame used in Lead on Chip packages, reference to U.S. Pat. Nos. 5,545,920 and 5,872,398 shall be made.
To keep pace with the tendency of minimizing the size of an IC, the space available for accommodating leads
11
and
12
(also inward ends
15
an
16
) in lead frame
1
is decreasing. For example, the pitch of bonding pads of an IC is reduced as a result of size reduction of the IC, and the pitch of leads as well as the gap
191
between adjacent inward ends of leads must be reduced accordingly, resulting in significant difficulty in packaging an IC subject to the tendency of minimizing the size of the IC, leading to higher failure rate and higher manufacturing cost. To respond to the tendency of minimizing the size of ICs (integrated circuits), the present invention provides schemes of changing the configuration of inward ends
15
and
16
, so that the difficulty in the process of packaging ICs of smaller size arising from the requirement of smaller pitch of leads
11
or
12
(also smaller gap between adjacent inward ends
15
or
16
) of a lead frame
1
can be avoided.
To keep pace with the tendency of increasing number of electrical connections with an IC, the space of a lead frame must be capable of accommodating more leads, resulting in significant difficulty in packaging an IC due to the inevitable reduction of inner lead pitch of a lead frame if size remains on the same scale, leading to higher failure rate and higher manufacturing cost. To respond to the tendency of requiring more electrical connections with an IC, the present invention provides schemes of changing the configuration of inward ends
15
and
16
, so that the difficulty in the process of packaging an IC providing more electrical connections can be avoided.
SUMMARY OF THE INVENTION
An object of the present invention is to provide new configurations of a lead frame by which bigger inner lead pitches can be achieved without need of increasing the size of the lead frame, thereby the failure rate and manufacturing cost in the process of packaging ICs can be lowered, particularly the difficulty in packaging ICs of smaller size can be significantly eased.
Another object of the present invention is to immunize an IC packaging process against the difficulty resulting from smaller size of the lead frame or the IC to be packaged, or from larger number of leads/electrical connections of the lead frame or the IC to be packaged.
The present invention is characterized by arranging the inward ends of leads of a lead frame in unprecedented ways in order to realize bigger inner lead pitch (or bigger gap between adjacent inward ends) of a lead frame compared to a conventional one of equivalent size.
The word “IC” in this disclosure means “integrated circuit”, and the word “ICs” means “integrated circuits”.
What is represented by the words “lead frame” in this disclosure is not limited to the popularly known lead frame. The lead frame in this disclosure represents any means capable of providing or supporting electrical conduction between at least an IC in a package and any device outside the package. A bonding surface of an IC in this disclosure means a surface from which the IC is electrically connected. For example, a bonding surface of an IC in the form of a chip is a surface having bonding pads thereon for electrical connection with the IC. What is represented by the word “disperse” in this disclosure includes the meaning of “be disposed”.
A first aspect of the present invention may be represented by a lead frame for a process of packaging at least an IC, which comprises: a first group of leads; a second group of leads; and an IC corresponding region enclosed by a polygon (a quadrilateral corresponding to the pattern of an IC, or equivalent to the size or shape of a bonding surface of an IC, for example); wherein the lead includes at least an outward end and an inward end, the inward end being inside the IC corresponding region, the inward ends of the first group of leads facing and being spaced from the inward ends of the second group of leads; and wherein the first edge of the polygon is perpendicular to the second edge of the polygon, the third edge of the polygon parallels the first edge of the polygon, the inward ends disperse one by one between the first edge of the polygon and the third edge of the polygon (i.e., disperse one by one from the first edge of the polygon to the third edge of the polygon, or from the third edge of the polygon to the first edge of the polygon) in such a way that the further an arbitrary one of the inward ends is from the first edge of the polygon than another one of the inward ends, the nearer the arbitrary one of the inward ends is from the second edge of the polygon than the another one of the inward ends.
It can be seen the gap between any adjacent two of the inward ends of leads of either the first group or the second group in the lead frame according to the first aspect of the present invention can be significantly bigger than a corresponding gap (
191
in
FIG. 1
) in a conventional lead frame of the same size scale, and the inner lead pitch of leads of either the first group or the second group according to the present invention can thus be significantly bigger. It is obvious the inner lead pitch of any two arbitrary leads of either the first group or the second group can be bigger than or at least equal to the gap between the inward ends of the two arbitrary leads.
If used in LOC packages, the inward ends of the first group of leads in the lead frame according to the first aspect of the present invention are spaced from those of the second group of leads by distances adequate for making electrical connection between the IC and the leads of the lead frame. For example, the bonding wires connecting the bonding pads of the IC and the leads of the lead frame must pass the space between the inward ends of the first group of leads and those of the second group of leads, therefore the distances between the inward ends of the first group of leads and those of the second group of leads are usually adequate for the bonding wires to be connected between the inward ends of the leads and the bonding pads of the IC. The distances between the inward ends of the first group
Huang Chien-Ping
Lee Yvonne
Pu Han-Ping
Ho Hoai
Huynh Andy
Klarquist & Sparkman, LLP
Siliconware Precision Industries Co. Ltd.
LandOfFree
Lead frame adaptable to the trend of IC packaging does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Lead frame adaptable to the trend of IC packaging, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lead frame adaptable to the trend of IC packaging will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3060743