Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Chip mounted on chip
Reexamination Certificate
2000-12-08
2003-04-22
Lee, Eddie (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Chip mounted on chip
C257S778000, C257S779000, C257S739000, C257S738000, C257S786000, C257S459000, C257S625000, C438S666000, C438S613000, C438S612000, C438S108000
Reexamination Certificate
active
06552436
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to semiconductor devices, and more particularly, to a semiconductor device having a ball grid array and method therefor.
BACKGROUND OF THE INVENTION
In some semiconductor manufacturing processes, such as for example, “flip chip”, bumps are fabricated on pad areas of a semiconductor die in order to interconnect the die to a package or to a substrate. The substrate is used to interface the electrical circuits of the semiconductor die to a printed circuit board. In some instances, the semiconductor die may be attached directly to the printed circuit board.
An integrated circuit manufactured using “flip chip” technology may have hundreds of these solder bumps. In solder ball, or solder bump, technology, various techniques may be used to define the area on the pads for receiving the solder balls. One technique provides a solder ball connection area called a soldermask defined (SMD) bonding pad. Another technique provides a solder ball connection area known as a non-soldermask defined (NSMD) bonding pad.
FIG. 1
illustrates a soldermask defined bonding pad in accordance with the prior art. A SMD bonding pad is provided on both a substrate
12
and on a printed circuit board
22
. The SMD bonding pad on substrate
12
includes a metal bonding pad
14
formed on substrate
12
. Substrate
12
is generally used to interconnect, or interface a semiconductor die (not shown) with printed circuit board
22
. A soldermask coating
16
is formed over substrate
12
and covers a portion of bonding pad
14
. A portion of the metal bonding pad
14
is left exposed. A solder ball
24
is then attached to bonding pad
14
. When connecting substrate
12
to printed circuit board
22
, a bonding pad
20
is formed on the surface of printed circuit board
22
. A solder mask
18
is formed over the surface of printed circuit board
22
and overlaps a portion of bonding pad
20
to form another SMD bonding pad. The openings in the soldermask coatings
16
and
18
define the area of the bonding pads to which the solder attaches for making electrical contact between the substrate
12
and printed circuit board
22
. Also, the soldermask prevents liquid solder from flowing over areas where it is not wanted, such as for example, along a metal trace. In addition, the soldermask functions to shape the solder ball
24
after it is reflowed.
FIG. 2
illustrates a non-soldermask defined bonding pad in accordance with the prior art. An NSMD bonding pad is illustrated on both a substrate
32
and a printed circuit board
42
. The NSMD bonding pad on substrate
32
includes a metal bonding pad
34
. As described above in connection with
FIG. 1
, substrate
32
is used to interconnect, or interface a semiconductor die (not shown) with printed circuit board
42
. A soldermask coating
36
is formed over substrate
32
and has an opening that does not typically contact or overlap bonding pad
34
. A solder ball
44
is attached to bonding pad
34
. Likewise, a bonding pad
40
is formed on the surface of printed circuit board
42
where it is intended to connect to bonding pad
34
. A solder mask
38
is formed over the surface of printed circuit board
42
and has openings that do not typically cover or overlap any of bonding pad
40
. The shape and size of the bonding pads function to determine the shape of the solder ball after solder reflow.
SMD bonding pads are known to provide greater reliability in applications where the printed circuit board is subjected to high bending loads, such as for example, a cellular telephone that includes push buttons on the same printed circuit board as the integrated circuits. However, SMD bonding pads are not known for providing high reliability in those applications that subject the printed circuit board to thermal cycling, such as for example, in an automotive application. In contrast, NSMD bonding pads are known to provide high reliability in extreme temperature applications, but not high reliability when subjected to bending loads.
Therefore, a need exists for a technique to attach a semiconductor device to a printed circuit board that provides improved bending reliability as well as improved reliability when exposed to temperature cycling.
REFERENCES:
patent: 5668405 (1997-09-01), Yamashita
patent: 5859475 (1999-01-01), Freyman et al.
patent: 5872399 (1999-02-01), Lee
patent: 5990545 (1999-11-01), Schueller et al.
patent: 6201305 (2001-03-01), Darvaeux et al.
patent: 6210992 (2001-04-01), Tandy et al.
Burnette Terry E.
Koschmieder Thomas H.
Mawer Andrew J.
Hill Daniel D.
Lee Eddie
Motorola Inc.
Nguyen Joseph
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