When making ultra-fine wire, as the wire gets
finer, processing becomes more difficult. The possible
reduction per die decreases, the possible drawing speed
drops and the wire breaks more often. Furthermore, the
smaller the wire the harder it becomes to maintain uniform
wire diameter. The diameter fluctuates excessively. However,
with our "Augmented Hydrostatic Extrusion" (HYDRAW)
equipment we are able to extend beyond some limitations of
the present day
processes. Reductions up to 25% per die (even for
hyper-fine gold (Au) wire) are possible, wire breaks rarely
occur, and the wire size remains uniform. Presently we make
wire of uniform diameter down to 0.4mil. There is no
demand in the foreseeable future for wire size smaller than
State of the Art
Tanaka of Japan, is the world's major supplier of gold
bonding wire. Tanaka already makes 0.8mil (20µ) gold
bonding wire commercially. They also make 0.7mil
(17.5µ) stud bump wire commercially. Today's automated
ultrasonic bonding machines are capable of bonding wire down
to those sizes. Currently only chips for special
applications require wire below the 0.7mil size. Chips for
such applications are bonded by manually operated wire
bonding machines. This wire size slows down the rate of
production. These are special applications for military and
aerospace products only.
Flip (back to back) chips, bonded by ball bumps, are
becoming more and more popular. Wire contacts are replaced
by tiny balls (bumps) that are bonded to the chip. The chip
is then flipped onto leads, and bonded, back to back, in one
step. The bumps are produced from ultra-fine wire. Flip
chips are becoming more dense, and the current bumps are
made from 1mil wire with some applications using 0.7mil. The
vision of the major chip makers (and users) is to make the
bumps from smaller wire, down to 0.4-0.5mil.
The bulk of the current ball bumps are made from 1mil
wire. This wire size dictates a pitch of at least 100µ.
In the race to make smaller chips with a larger number of
leads, some makers have started to use bumps from 0.7mil
wire. The pads are closer, with a pitch of 70µ,
allowing a larger lead count ("denser chips").
Presently the factor limiting the density of
the chip is the size of the wire that can be produced
reliably, economically, and with uniform diameter. Because
the pad size has to be 2 to 3 times larger than the wire
from which the ball bump is made, a 0.7mil wire dictates
40µ pad size which in turn mandates a pitch of 50 to
60µ. Wire size of 0.4mil is as small as present
day technology may demand.
Research and development now focuses on the next step,
where the pads will be replaced by other means of bonding
and the need for wire will be eliminated. Such developments
are looming over the horizon, but are not yet a reality.
Furthermore, the potential uses of ultra-fine wire stretch
beyond the bonding wire market.
All the wire makers now feel the pressure to make finer
size gold bond wire, for wire bonding for standard chips and
for stud bump bonding for flip chips. Typical major
limitations for wire smaller than 2mil are:
- The possible percent reduction in area per die is
less than 4%.
- The speed is less than 1000 feet per minute.
- Uniformity of the wire becomes poorer and poorer. The
diameter fluctuates by about ±5% for a 1mil wire and
even more for smaller wire.
- Wire breaks more often into smaller lengths.
We at Metalforming Inc. can make 0.4mil gold wire
on our Hydraw machine. This wire can be used by
chip makers, as a conventional bond wire, as well as stud
ball bump wire for the flip chip.
We have used wire from three of the five major suppliers
of gold bond wire and found that their wire was not uniform
in diameter, fluctuating by as much as ±5%. Even when
we fed their (1.5 or 2mil) wire into our Hydraw machine as
raw material we were able to reduce it down to 0.4mil and
restore the uniformity of the diameter.
Comparing our capabilities with the state of the art we
- Our 1mil wire is the most uniform wire available. The
1mil wire by other wire makers was irregular in size. We
can make a much more uniform wire.
- Only Metalforming Inc. can make wire below 0.7mil
reliably and economically.
- In addition, our process offers an alternative, to
wire makers, that have problems maintaining uniformity at
any wire size.
These comparisons are tabulated below:
Reduction in Area per Die
4% or less
seldom or none
Minimum Wire Size
Window of Opportunity
The most attractive and achievable goal for Metalforming
Inc. is to enter into a partnership with a major established
fine wire manufacturer or chip maker. This manufacturer/chip
maker could supply us with the raw wire of about 2mil and
Metalforming Inc. will reduce it to the desired size. Thus,
we will only do what the Hydraw process is good for, i.e.,
reduce the wire in the range from 2mil down to 0.4mil. The
exact transition point may shift up or down from 2mil,
depending on the quality and economics of the source wire.
Both wire makers and chip makers are interested in having
more than one supplier of the small size wire.
Even if we perfect our process further, we still face the
necessity to enter into the relationship described. The
major thrust of our promotional effort should shift into
developing a strategic partner relation. Preferably, but not
exclusively, such a partner may be a wire or chip maker.
All gold bonding wire makers have smelting facilities and
technology. They also have standard wire producing equipment
and personnel. We can avert the need to develop smelting
capabilities at this time. We can enter the market as a
sub-contractor to an established wire maker, or to the
end-user, the chip maker.
Most wire makers cannot produce wire below the size of
1mil. We can produce such wire economically on their behalf.
They will supply the source wire and we would reduce it to
0.7 and even to 0.4mil wire when requested. These makers are
under pressure to come up with products that compete with
Tanaka's 0.7mil wire, and we can offer them a solution. They
are under pressure because they don't want to disappoint
their customers requiring larger diameter wire, and lose the
0.7mil niche to Tanaka. Their customers cannot tolerate,
indefinitely, a single source supply situation.
We may offer the chip makers access to the much desired
0.4mil wire, which they cannot get anywhere else. They will
provide us with a 1 or 2mil wire (which they get from their
regular source) and we will reduce it for them to 0.4mil.
Chip makers have all the remaining technologies needed to
produce chips with 50µ pitch. They wish to produce that
chip, if they could only have a reliable source for an
inexpensive 0.4mil wire.
These are our niches, or windows of opportunity,
to penetrate the market.
The time is now ripe for this step. We learned that some
wire makers are pressured by major customers to supply them
with 0.7mil wire for their flip chip. They must do it to
satisfy a good customer, but due to production or economical
considerations prefer not to assume this responsibility. We
were asked to supply chip makers with test quantities to
verify our reliability.
Standard bond wire down to
Present smallest bonding & bump wire
Expected next generation stud bump wire diameter
World consumption by year 2000 for all sizes
Potential Strategic Partnership:
Metalforming Incorporated is an enterprising company with
a deep rooted base in many traditional metalforming
processes and the progressive development of new
technologies. In addition to its sound scientific background
and accreditation, it is an entrepreneurial company ready to
consider mutually beneficial relationship with established
companies. The form of these relationships can be from
consulting, training and process optimization to new
technology licensing and limited partnerships.
The Hydraw project by Metalforming Inc. is now ripe for
implementation as a manufacturing reality. We are open to
offers of strategic partnership.
The project was presented at:
"Technology Transfer - Today for Tomorrow"
Hynes Convention Center, Boston, MA