Apparatus for forming wire bonds from circuitry on a...

Details Apparatus for forming wire bonds from circuitry on a... Apparatus for forming wire bonds from circuitry on a...

2001-03-02

2002-11-05

Elve, M. Alexandra (Department: 1725)

Metal fusion bonding

Process

Using high frequency vibratory energy

C228S173500

Reexamination Certificate

active

06474532

ABSTRACT:

TECHNICAL FIELD
The invention pertains to methods and apparatuses for forming semiconductor chip assemblies. In particular aspects, the invention pertains to methods and apparatuses for forming wire bonds in board-on-chip packages.
BACKGROUND OF THE INVENTION
A prior art method of forming a board-on-chip package (which can be generally referred to as a die package) is described with reference to
FIGS. 1-5
. Referring first to
FIG. 1
, such illustrates a fragment of an assembly
10
comprising an insulative material substrate
12
. Substrate
12
can comprise, for example, a circuit board.
Substrate
12
comprises a top surface
13
and slits
18
extending therethrough. Circuitry
16
is formed on top of surface
13
. Circuitry
16
and slits
18
form repeating patterns across top surface
13
. The repeating patterns define separate units
19
,
21
and
23
, each of which ultimately forms a separate board-on-chip package.
Referring to
FIGS. 2-4
, an enlarged segment of substrate
12
, corresponding to unit
21
, is shown in three different views.
FIG. 2
is a top view similar to the view of
FIG. 1
,
FIG. 3
is view along the line
3
—
3
of
FIG. 2
, and
FIG. 4
is a view along the line
4
—
4
of FIG.
3
. Substrate
12
is inverted in the view of
FIG. 3
relative to the view of
FIGS. 1 and 2
. Accordingly, surface
13
(referred to as a top surface in referring to
FIGS. 1 and 2
) is a bottom surface in the view of FIG.
3
. In referring to
FIG. 3
, surface
13
will be referred to as a first surface.
Substrate
12
comprises a second surface
15
in opposing relation relative to first surface
13
. A semiconductive material-comprising chip (or die)
14
is adhered to surface
15
via a pair of adhesive strips
20
. Strips
20
can comprise, for example, tape having a pair of opposing surfaces
22
and
24
, with adhesive being provided on both of such opposing surfaces. Strips
20
typically comprise insulative material. Wire bonds
28
(only some of which are labeled in
FIG. 2
) extend from circuitry
16
and through slit
18
to electrically connect circuitry
16
to bonding pads
25
(only some of which are labeled in
FIG. 2
) associated with chip
14
, and to accordingly electrically connect circuitry
16
with circuitry (not shown) comprised by chip
14
. Chip
14
comprises a surface
17
which faces surface
15
of substrate
12
. The bonding pads are on surface
17
. (The wire bonds and bonding pads are not shown in
FIG. 4
for purposes of clarity in the illustration.)
FIG. 5
illustrates further processing of the assembly
10
. Specifically,
FIG. 5
illustrates units
19
and
21
of
FIG. 1
after a first encapsulant
40
is provided over wire bonds
28
, and a second encapsulant
42
is provided over chips
14
associated with units
19
and
21
. First and second encapsulants
40
and
42
can comprise the same material and typically comprise an insulative material, such as, for example, cured epoxy.
Conductive balls
31
are formed over portions of circuitry
16
(shown in
FIGS. 1 and 2
) to form a ball grid array over circuitry
16
. Such array can subsequently be utilized to form a plurality of interconnects from circuitry
16
to other circuitry (not shown). Conductive balls
31
can be formed of, for example, tin, copper or gold.
Substrate
12
is subjected to a singulation process which separates units
19
and
21
from one another, and thus forms individual board-on-chip packages from units
19
and
21
. The singulation process can include, for example, cutting through encapsulant
42
and substrate
12
.
Difficulties can occur in the formation of the wire bonds associated with a board-chip-package. Among the methods commonly utilized for forming such wire bonds are a TESSERA™ process and a so-called tab bonding process. In either of such processes, the wires utilized for wire-bonding initially have one end bonded to circuitry
16
. The wires are provided to extend at least partially across slit
18
so that a second end (which is not bonded to circuitry
16
) extends over or past slit
18
. A rod is then utilized to individully and sequentially push each wire into slit
18
and to hold the wire against chip
14
during an ultrasonic welding process. The ultrasonic welding individually and sequentially adheres the second end of each wire to a bonding pad
25
.
It would be desirable to develop alternative methods for forming wire bonds.
SUMMARY OF THE INVENTION
In one aspect, the invention encompasses a method of forming a semiconductor chip assembly. A substrate is provided. Such substrate has a pair of opposing surfaces and circuitry formed on one of the opposing surfaces. A semiconductor chip is joined to the substrate. The semiconductor chip has bonding regions thereon. A plurality of wires join to the circuitry and extend over the bonding regions of the semiconductor chip. The wires are pressed down to about the bonding regions of the semiconductor chip with a tool. The tool is lifted from the wires, and subsequently the wires are adhered to the bonding regions of the semiconductor chip.
In another aspect, the invention encompasses an apparatus for forming wire bonds from circuitry on a substrate to a semiconductor chip joined to the substrate. Such apparatus comprises a support for supporting the substrate and the semiconductor chip. The apparatus further comprises a pressing tool movably mounted relative to the substrate, and which has a deflecting surface configured to press the wires into a slit of the substrate when the pressing tool is moved toward the substrate. The deflecting surface is substantially planar, and has a sufficient length to extend within a predominate portion of the slit.


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