Semiconductor device manufacturing: process – Making passive device – Resistor
Reexamination Certificate
2000-04-27
2004-01-06
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Making passive device
Resistor
C438S381000, C438S118000
Reexamination Certificate
active
06673690
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to integrated circuit (IC) packaging technology, and more particularly, to a method of mounting a passive component, such as a resistor or a capacitor, over an IC package substrate, such as a BGA (Ball Grid Array) substrate
2. Description of Related Art
An IC package, such as BGA (Ball Grid Array, IC package, is designed to pack an IC device therein so that the IC device can be easily handled and mounted on a circuit board. In the package, the IC device is typically mounted together with some passive components, such as resistors and capacitors, on the substrate.
FIGS. 1A-1B
are schematic sectional diagrams used to depict a conventional method of mounting a passive component over an IC package substrate. As shown in
FIG. 1A
, this IC package is a BGA type which includes a substrate
10
, an IC chip
20
, a passive component
30
, a molded compound
40
, and an array of solder balls
50
. The IC package configuration of
FIG. 1A
is conventional and well-known to those skilled in the art of IC packaging, so description thereof will not be further detailed.
FIG. 1B
shows an enlarged view of the part enclosed in the dashed circle in
FIG. 1A
where the passive component
30
is mounted. As shown, the substrate
10
has a core portion
102
and a surface-mount portion
10
b
on which a pair of solder pads
11
,
12
are provided; and the passive component
30
is mounted in such a manner that its two ends
31
,
32
are electrically bonded by means of solder
12
a
respectively to the solder pads
11
,
12
.
One problem to the mounting of the passive component
30
over the substrate
10
, however, is that a gap
13
would be undesirably left between the passive component
30
and the substrate
19
. The existence of this gap
13
would abuse the following drawbacks during the manufacture of the IC package.
First, during the process for attaching the solder balls
50
, the high-temperature condition would cause the solder on the passive component
30
to be partly melted, and the melted solder would then flow into the gap
13
through capillary effect, thus undesirably resulting in a bridged short-circuit between the two ends
31
,
32
of the passive component
30
. This bridged short-circuit may cause the internal circuitry of the IC chip
20
to be inoperable.
Second, during the compound-molding process, the gap
13
would cause the so-called popcorn effect when subjected to thermal stress, which would undesirably degrade the quality of the overall IC package configuration.
Third, during the compound-molding process, since the passive component
30
is fixed in position over the substrate
10
only by the solder applied to the two ends
31
,
32
thereof, it can he easily forced out of position by the impact from the flowing resin used in the compound-molding process. If the impact is large, it can cause dismounting and even electrically disconnection of the passive component
30
.
There exists therefore a need in the IC industry for a new method of mounting a passive component over an IC package substrate, which can help eliminate the above-mentioned drawbacks of the prior art.
SUMMARY OF THE INVENTION
It is therefore an objective of this invention to provide a method for mounting a passive component over an IC package substrate, which can help prevent the mounted passive component from being subjected bridged short-circuit.
It is another objective of this invention to provide a method for mounting a passive component over an IC package substrate, which can help prevent the overall IC package configuration from being subjected to popcorn effect.
It is still another objective of this invention to provide a method for mounting a passive component over an IC package substrate, which can help fix the mounted passive component more securely in position over the substrate.
It is yet another objective of this invention to provide a method for mounting a passive component over an IC package substrate, which can help allow the manufactured IC package to be more assured in quality and more reliable to use.
In accordance with the foregoing and other objectives, the invention proposes a new method for mounting a passive component over an IC package substrate. The method of the invention is characterized in the use of an electrically-insulative material, such as epoxy resin, to fill up the gap between the passive component and the substrate. The filling can be performed in two ways: either after or before the passive component is attached.
In the fist case (i.e., filling after the passive component is attached in position), the method of the invention comprises the following steps: (1) providing a pair of solder pads at predefined locations over the substrate; (2) soldering the passive component to the solder pads, with a gap being left between the passive component and the substrate, (3) applying a flowable and curable electrically-insulative material to the periphery of the passive component, and through capillary effect, the flowable and curable electrically-insulative material would fill into the gap between the passive component and the substrate; and (4) curing the filled electrically-insulative material into hardened state.
In the second case (i.e., filling before attaching the passive component), the method of the invention comprises the following steps: (1) providing a pair of solder pads at predefined locations over the substrate; (2) pasting an electrically-insulative material over the area between the paired solder pads to a predetermined thickness that would allows no gap to be left between the passive component and the substrate when the passive component is mounted over the substrate; and (3) soldering the passive component onto the paired solder pads.
Since the method of the invention allows no gap to be left between the passive component and the substrate, it can help eliminate the drawbacks of the prior art, including bridged short-circuit, popcorn effect, and dismounting of the passive component. The invention is therefore more advantageous to use than the prior art.
REFERENCES:
patent: 6153930 (2000-11-01), Hori
patent: 6208525 (2001-03-01), Imasu et al.
patent: 6238223 (2001-05-01), Cobbley et al.
Tummala R.R. et al.; Microelectronics Packaging Handbook Part II: Semiconductor Packaging 106-107 (2d ed. 1997).
Chuang Jui Yu
Wu Chi-Chuan
Corless Peter F.
Edwards & Angell LLP
Jensen Steven M.
Lattin Christopher W
Niebling John F.
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