Multiconductor interconnect

Details Multiconductor interconnect Multiconductor interconnect

2000-07-18

2002-10-29

Sircus, Brian (Department: 2839)

Optical waveguides

With disengagable mechanical connector

Structure surrounding optical fiber-to-fiber connection

C439S067000

Reexamination Certificate

active

06471415

ABSTRACT:

FIELD OF THE INVENTION
This invention generally relates to a multiconductor interconnect. More particularly, this invention relates to a space saving multiconductor interconnect for coupling two or more components of a particular device.
BACKGROUND OF THE INVENTION
With increased computerization, more and more sensitive and valuable information is being generated and stored. Consequently, the need for high capacity and cost effective data storage is ever increasing. Dual and single reel tape drives have become a preferred method for storing electronic data.
Referring to
FIG. 1
, using linear recording technology, a tape drive pulls tape
10
across a transducer head
12
saving and/or retrieving electronic data in multiple parallel tracks that extend along the length of tape
10
. Increasing the number of tracks on tape
10
and decreasing the space between each track increases the tape's storage capacity. However, this also increases the complexity of head
12
. Head
12
includes a number of read/write elements (not shown) formed on a thin film wafer
14
. To align the read/write elements with a particular track on tape
10
, head
12
may also include servo elements which read and possibly write alignment and position information on tape
10
. The servo information can be used to accurately position head
12
both across the width of tape
10
on a desired track and along the length of tape
10
at the start of a specified file.
To enable a drive to read and write data while reading and recording alignment information, a number of traces
16
and corresponding bond pads
18
are required to connect head
12
to the other components of the tape drive. For example, an eight track head requires eighty or more traces. Additional traces for shield connections, ground lines, and connections on thin film wafer
14
can raise that total to ninety or more.
Typically, one or more ribbon cables
20
are used to connect head
12
to the other components of a tape drive. Ribbon cable
20
consists of a series of conductors
22
on a flat flexible strip of insulative material. Conductors
22
, generally parallel to one another, extend along the length of the strip terminating at each end of the strip with bond pads
24
or some other suitable termination points. On one end of the strip, as shown in
FIG. 1
, each bond pad
24
on the ribbon cable is coupled to a corresponding bond pad
18
on thin film wafer
14
of head
12
with bond wires
26
using thermocompression, thermosonic, or ultrasonic wire bonding techniques. Bond pads
18
and
24
and bond wires
26
are then encapsulated in epoxy
28
or some other suitable encapsulating material.
Current technology allows placement of approximately
45
conductors on a 7 millimeter wide ribbon cable. However, the same number of traces require only a 3 millimeter width on thin film wafer
14
. Referring still to
FIG. 1
, one known solution for aligning bond pads
24
on ribbon
20
with the bond pads
18
on thin film wafer
14
involves fanning out traces
16
. This solution increases the size of thin film wafer
14
and, consequently, the manufacturing cost of transducer head
12
.
Referring now to
FIG. 2
, instead of fanning out the traces on transducer head
12
, a second known solution involves fanning out bond wires
26
that connect ribbon cable
20
to head
12
. However, the increased length in the outer bond wires causes a number of problems. First, the longer wires are more likely to contact adjacent wires and cause a short circuit. It is difficult to adapt a wire bond tool to the changing angles of bond wires
26
, and the longer outer wires are more likely to snag on the tooling and break before encapsulation. And, the additional length of the outer bond wires
26
increases the resistance and inductance of the connection between head
12
and the other components of a tape drive.
Referring now to
FIG. 3A
, a third known solution is revealed in U.S. Pat. No. 3,633,189 which issued to Shahbuddin Billawala in 1972. Billawala discloses a ribbon cable
20
capable of concentrating bond pads
24
into a small area. Ribbon cable
20
terminates on one end with a central portion
30
and two lateral portions
32
. Transverse portions
34
connect each lateral portion
32
to the central portion
30
. One half of ribbon cable's conductors terminate with bond pads
24
on central portion
30
while one quarter of the conductors terminate with bond pads
24
on each lateral portion
32
.
FIG. 3B
shows a slightly modified version of Billawala's cable. Each transverse portion
34
is folded over itself placing the lateral portions
32
in a plane parallel to that of central portion
30
. This places bond pads
24
in two parallel rows—the first row defined on central portion
30
and the second row defined on lateral portions
32
.
While Billawala allows ribbon cable
20
to be wire bonded to head
12
without fanning bond wires
26
or traces
16
on head
12
, the design creates a number of problems. First, the unsupported folded transverse portions
34
increase the thickness of ribbon cable
20
. The increased length of the conductors passing through transverse portions
34
increases the cable's resistance and inductance. If each conductor has different electrical characteristics, balancing the tape drive's amplifiers for the read elements and drivers for the write elements becomes more difficult. The loops in the conductors created by folding transverse portions
34
increase the cable's susceptibility to magnetic interference. The double folds also increase the risk of broken conductors. Finally, wire bonding requires accurate placement of all bond pads
18
and
24
, and Billawala fails to disclose a method for reliably aligning bond pads
28
on the lateral portions
32
with those on central portion
30
after lateral sections
34
are folded.
SUMMARY OF THE INVENTION
The present invention is directed to a space saving multiconductor interconnect. A plurality of conductors extend through the interconnect. To decrease the width of a selected portion of the interconnect, the conductors are split between two layers. One group the conductors extend along a portion of a first layer jumping to and continuing along a second layer. The remaining conductors extend only along the first layer. Consequently, the width of the interconnect where the conductors are split between the layers can be substantially reduced.
In one exemplary embodiment, the first layer is characterized by a first section having only first conductors and a second section having both the first second conductors. The first conductors in the first section of the first layer span a first width and the first and second conductors in the second section of the first layer span a second width greater than the first width. The second layer includes third conductors extending between first and second sections of the second layer. The third conductors in the first section of the second layer span a third width, and the third conductors in the second section of the second layer span a fourth width.


REFERENCES:
patent: 3214725 (1965-10-01), Derose et al.
patent: 3633189 (1972-01-01), Billawala
patent: 4682828 (1987-07-01), Piper et al.
patent: 4815990 (1989-03-01), Ristedt et al.
patent: 5042971 (1991-08-01), Ambrose
patent: 5061830 (1991-10-01), Ambrose
patent: 5130499 (1992-07-01), Dijkshoorn
patent: 5160276 (1992-11-01), Marsh et al.
patent: 5219292 (1993-06-01), Dickirson et al.
patent: 5697794 (1997-12-01), Mosquera

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