Semiconductor package

Details Semiconductor package Semiconductor package

1998-09-15

2003-01-28

Feild, Lynn D. (Department: 2835)

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

C361S772000, C361S760000, C361S818000, C361S820000, C174S250000, C174S255000, C174S260000, C174S262000, C174S266000, C257S698000, C257S734000, C257S737000, C257S738000

Reexamination Certificate

active

06512680

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a semiconductor package particularly such as a ball grid array package to which a countermeasure for cross talk noise between signal lines is applied.
2. Related Background Art
In recent years, in the tendency of IC toward more pins and smaller size, a narrower pitch in a surface mounting package such as a shrink small out package (hereinafter abbreviated as SSOP) or a quad flat package (hereinafter abbreviated as QFP) has been advanced more and more.
Particularly, as a narrower pitch, for example, QFP of 0.5 mm is often used in handy instruments.
However, when packaging cost is taken into account, further narrowing of the pitch has become limited from various viewpoints such as a packaging apparatus, a packaging material and packaging control, and as an answer to the desire for more pins, there is adopted a method of solving without making the body size of the package larger, i.e., a pin grid array (hereinafter abbreviated as PGA) as a two-dimensional pin arrangement instead of a conventional one-dimensional pin arrangement or a ball grid array (hereinafter abbreviated as BGA). Particularly PGA, as a simple answer to the tendency toward more pins rather than its size, has utilized sockets since long ago and has often been used in the CPU, gate arrays and the like of personal computers.
Generally, PGA often handles many pins and high-speed digital signals and the package thereof is often expensive. On the other hand, BGA, unlike PGA, is a package for surface mounting at first and moreover, has a chip placed on a printed substrate or the like including a flexible printed substrate and has solder balls disposed at a relatively rough pitch in the form of a grid on the back thereof. Accordingly, in spite of the rough pitch, many pins can be secured for a package size, and relatively low-cost packaging is possible by the self position modifying effect or the so-called self alignment effect by the solder balls.
However, BGA is a planar (two-dimensional) pad arrangement and therefore, it is the premise thereof to receive it by a mother board which is a multi-layer substrate, but since highly dense pads are disposed on a narrow area, the cross talk between signals increases, and also when wiring is drawn out in the mother board, so-called cross talk which is the electrical leakage of signals is increased by the capacity coupling by the grade separation between drawn-out lines.
Also, as described above, QFP is known as the typical semiconductor package, but in recent years, with the higher density of semiconductor elements, the number of electrodes (for example, power source pins and signal pins) has also increased rapidly, and the tendency of semiconductor elements toward more pins has advanced.
On the other hand, compactness and thinness have been required of the types of machines using semiconductor elements, and the downsizing of semiconductor packages has been required to package semiconductor elements more highly density.
As the result, OMPAC (over-molded plastic array carrier) has been proposed as a new semiconductor package.
FIG. 13
of the accompanying drawings shows OMPAC. As the typical construction of OMPAC, a semiconductor element
101
is carried on a printed substrate
102
, and the wiring pattern of the printed substrate
102
and the electrode portion of the semiconductor element
101
are connected together by wire bonding
103
. Also, this wiring pattern is connected to the pertinent electrode land
106
of a plurality of electrode lands formed in a matrix-like form on the back side of the printed substrate
102
, and further this electrode land melts a solder ball and forms the protruded electrode portion
105
of the solder ball.
Also, the upper surface portion of the semiconductor element
101
is molded by a transfer mold
104
, whereby the semiconductor element
101
is hermetically sealed.
The thus constructed OMPAC permits electrodes to be formed in a matrix-like shape on the back of the substrate and therefore, providing more pins is possible even when the space between adjacent electrodes is as wide a pitch as 1.0 to 1.5 mm.
Accordingly, when this semiconductor package is to be packaged, it is not necessary to print cream solder with a minute pattern, and solder balls excellent in strength become the electrodes of the semiconductor package and therefore, this semiconductor package can be made into a semiconductor package easy to handle and having many pins. Such a semiconductor package of many pins is called BGA (ball grid array) and has become widely adopted.
As a substrate for carrying the BGA package thereon, use has in recent years been made of not only a printed substrate but also a ceramic substrate, a tape substrate or the like.
The packaging of such a BGA package is easily solder-connected to a parent substrate called a mother board, and electronic parts electrically connected to the BGA package are also mounted and disposed on the mother board proximate to this BGA package.
FIG. 14
of the accompanying drawings is a diagram showing an example of the connection between an IC chip enclosed in the BGA and additional elements around it. The reference numeral
110
designates an. MPU (micro-processing unit) which is an IC chip, the reference numeral
111
denotes a bypass capacitor connected between a power source terminal (VCC) and a GND terminal (VSS) for preventing the malfunctioning of the IC chip by the fluctuation of a power source, and the reference numerals
112
and
113
designate capacitors for a charge pump constituting a charge pump circuit, and connected between charge pump terminals CP
1
and CP
2
and the GND terminal (VSS) as shown, and making a voltage twice or thrice as great as a certain reference voltage which is used chiefly as a liquid crystal driving voltage.
The reference numeral
114
denotes an XTAL (crystal) oscillator for the low speed operation of the IC chip and liquid crystal drive timing, and the opposite ends of the element are connected to oscillation terminals (XTAL
1
and XTAL
2
).
The reference numeral
115
designates a high speed oscillator, and an element of three terminals containing an oscillation capacitor therein is often used for the high speed operation of the IC chip, and this high speed oscillator is connected between oscillation terminals (XTAL
3
and XTAL
4
) and the GND terminal (VSS).
The above-described elements
112
to
115
all constitute a high impedance circuit, and are liable to be affected by the noise from outside and the cross talk noise of proximate lines, thus causing the malfunctioning of the IC chip or the problem that the IC chip does not operate at all. Therefore, it is necessary that the IC chip
110
, the bypass capacitor
111
and the elements
112
to
115
added to the high impedance circuit be disposed at locations as proximate as possible to one-another, and the connection thereof must be done with the cross talk noise sufficiently taken into account.
FIG. 15
of the accompanying drawings shows a prior-art BGA package and the surrounding elements described above with reference to
FIG. 14
as they are mounted, and a BGA package
120
formed with an IC chip
110
enclosed therein is solder-connected to and mounted on a parent substrate
122
called a mother board through the solder ball portion shown in FIG.
13
.
The connection to the surrounding elements is effected by the patterning in the multi-layered mother board
122
, and must be done with the problem of cross talk noise or the like fully taken into account.
Also, the aforedescribed multi-layering of the mother board
122
is limited in using the element mounting surface in the connection with the other elements than the above-mentioned surrounding elements from the BGA package terminals of many pins, according to a construction in which as in the aforedescribed example of the prior art, elements are disposed around the BGA package
120
, and such a limitation is caused because a digital signal and an analog signal including the aforementioned

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