Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Assembly of plural semiconductive substrates each possessing...
Reexamination Certificate
2000-04-11
2001-10-23
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Assembly of plural semiconductive substrates each possessing...
C438S118000, C438S618000
Reexamination Certificate
active
06306682
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 fabricating a BGA (Ball Grid Array) IC package of the type having an encapsulating body, which allows the BGA IC package to be manufactured without having to use conventional organic substrate and encapsulating-body mold having cavity, so that the manufacture process can be more cost-effective to carry out than the prior art.
2. Description of Related Art
The BGA IC packaging technology allows an IC package to be made very small in size while nevertheless providing highly integrated functionality from a single IC package. A conventional method for fabricating a BGA IC package of the type having an encapsulating body is disclosed in U.S. Pat. No. 5,830,800, whose procedural steps are briefly depicted in the following with reference to
FIGS. 1A-1F
.
Referring to
FIG. 1A
, in the first step, a copper sheet
10
is prepared. Next, a dry film
20
of a predetermined pattern is formed over the copper sheet
10
. The dry film
20
can be formed by, for example, first coating a photoresist layer over the copper sheet
10
, and then removing selected portions of the photoresist layer through a masked exposure/development/etching process.
Referring to
FIG. 1B
, in the next step, an electrically-conductive material is coated over those areas over the copper sheet
10
that are unmasked by the dry film
20
to thereby form an electrically-conductive trace structure
30
over the copper sheet
10
. After this, the entire dry film
20
(
FIG. 1A
) is removed. Subsequently, an IC chip
40
is mounted over the electrically-conductive trace structure
30
.
Referring to
FIG. 1C
, in the next step, a wire-bonding process is performed to apply a set of bonding wires
50
for electrically coupling the IC chip
40
to corresponding I/O ports on the electrically-conductive trace structure
30
.
Referring to
FIG. 1D
, in the next step, an encapsulating body
60
is formed to encapsulate the IC chip
40
, the bonding wires
50
, and the electrically-conductive trace structure
30
.
Referring to
FIG. 1E
, in the next step, the copper sheet
10
is removed through an etching process. After the copper sheet
10
is removed, the bottom side of the electrically-conductive trace structure
30
is exposed.
Referring to
FIG. 1F
, in the next step, an anti-oxidation coating
70
is formed over the bottom side of the encapsulating body
60
, while uncovering the electrically-conductive trace structure
30
. After this, a plurality of solder balls
80
are bonded to corresponding points on the electrically-conductive trace structure
30
. This completes the BGA IC package fabrication.
The foregoing patented method has the benefit of allowing the overall manufacture process to be simplified without having to use thick organic substrate, so that is highly cost-effective to carry out. For this reason, it is suitable for use to manufacture those IC packages that are to be mounted on small computers and intelligent electronic devices, such as palmtop computers and mobile phones.
One drawback to the forgoing patented method, however, is that it is only suitable for fan-out design, making the overall size difficult to be further reduced. This is because that the electrically-conductive trace structure
30
can be formed only beyond, and not within, the junction region of the IC chip
40
, making the surface area of the overall package body quite large. Still one drawback is that the etching process required to remove the copper sheet
10
, if not precisely controlled, would easily cause surface damage to the bottom side of the electrically-conductive trace structure
30
and the encapsulating body
60
, which would undesirably degrade the quality of the resulted BGA IC package. Moreover, after the copper sheet
10
is removed, the bottom side of the semi-finished package configuration is only supported by the electrically-conductive trace structure
30
, which is considered weak, thus making the positioning of the solder balls on the electrically-conductive trace structure
30
quite difficult to carry out.
SUMMARY OF THE INVENTION
It is therefore an objective of this invention to provide a new method for fabricating a BGA IC package, which allows the forming of the encapsulating body to be carried out though the use of a mold with no cavity, so that the same mold can be used for the fabrication of various BGA IC packages of different sizes, so that equipment cost can be reduced to help save the overall manufacture process.
It is another objective of this invention to provide a new method for fabricating a BGA IC package, which requires no conventional organic substrate so that the manufacture process can be carried out more cost-effectively and the resulted BGA IC package can be made more compact in size than the prior art.
It is still another objective of this invention to provide a new method for fabricating a BGA IC package, which allows fan-in design as well as fan-out design so that the number of I/O ports can be increased while making the overall package configuration compact in size.
It is yet another objective of this invention to provide a new method for fabricating a BGA IC package, which requires no etching process to be performed after the encapsulating body is formed so that the finished package can be more assured in quality than the prior art.
It is still yet another objective of this invention to provide a new method for fabricating a BGA IC package, which allows the implantation of the electrically-conductive balls to be easier to carry out and more precisely controlled than the prior art so that the implantation of the electrically-conductive balls can be more assured in quality than the prior art.
In accordance with the foregoing and other objectives, the invention proposes a new method for fabricating a BGA IC package. The method of the invention comprises the following procedural steps: (1) preparing a copper piece having a first surface coated with a first photoresist layer and a second surface coated with a second photoresist layer; (2) performing a selective-removal process on the second photoresist layer; (3) coating an electrically-conductive material over those areas over the second surface of the copper piece that are unmasked by the remaining part of the second photoresist layer to thereby form an electrically-conductive trace structure; (4) removing all the remaining parts of the first and second photoresist layers; (5) coating a first solder mask over the first surface of the copper piece and a second solder mask over the second surface of the copper piece; (6) defining a plurality of solder-ball openings in the second solder mask and an encapsulating-body opening in the first solder mask; (7) with the first solder mask serving as mask, removing the unmasked part of the copper piece through the encapsulating-body opening until reaching the electrically-conductive trace structure on the opposite side of the copper piece to thereby form an encapsulating-body cavity in the copper piece; (8) mounting at least one IC chip within the encapsulating-body cavity and over the electrically-conductive trace structure and the second solder mask; (9) electrically coupling the IC chip to corresponding points on the electrically-conductive trace structure; (10) forming an encapsulating body in the combined hollow space of the encapsulating-body cavity and the encapsulating-body opening; (11) implanting a plurality of electrically-conductive balls in the solder-ball openings; and (12) cutting away the remaining parts of the copper piece.
The foregoing method of the invention is characterized in that it requires no use of conventional organic substrate and no use of mold with cavity to manufacture the BGA IC package, which allows the overall manufacture process to be easier and cost-effective to carry out, and also allows the manufactured BGA IC package to be more assured in quality. The method of the invention is therefore more advanta
Ho Tzong-Da
Huang Chien-Ping
Jao Jui-Meng
Ko Eric
Lo Randy H. Y.
Corless Peter F.
Dang Phuc T.
Edwards & Angell LLP
Nelms David
Siliconware Precision Industries Co., LTD.
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