Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2000-06-21
2001-12-25
Gaffin, Jeffrey (Department: 2841)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S254000, C174S255000, C361S760000, C361S792000, C361S749000, C029S832000, C029S603040, C029S603050
Reexamination Certificate
active
06333470
ABSTRACT:
FIELD OF THE INVENTION
This invention involves an assembly for chip(s) with magnetic head(s) and a process for manufacturing the assembly.
It can be applied in particular to manufacturing helicoid recording heads on magnetic tape, for example for amateur or professional video recording (home VCRs or camcorders) or also for digital data recorders which use tapes or disks. There could also be other applications for other types of recording heads (linear on tape, on cards, etc.).
The high frequencies which are possible due to the small size of the magnetic heads integrated in thin layers allow for digital recording (for example with the DVC norm for video or DDS for data recording). Tape data recording systems are for mass data storage with the highest capacities and at the lowest cost. Its computer applications are archiving of data and backups of hard disks of systems or networks for distribution of large programs or databases.
STATE OF THE ART
FIGS. 1
to
3
in appendix illustrate the structure of a magnetic head integrated in thin layers which is known from document FR-A-2 747 226. As illustrated in
FIG. 1
, the head includes two polar pieces
10
1
,
10
2
separated by a head gap
14
, two magnetic branches
16
1
,
16
2
which partly cover the polar pieces, and a magnetic piece for flux closure
18
. This set of pieces constitutes a magnetic circuit. Around the branches
16
1
,
16
2
there are conducting windings
20
1
,
20
2
for reading and/or writing of the information written and/or read on the recording support which is not shown.
FIG. 2
shows the complete head with two conducting strips
22
1
,
22
2
allowing for access to the conducting windings
20
1
,
20
2
and two electrical connection studs
24
1
,
24
2
.
The head shown in
FIGS. 1 and 2
can be made collectively using micro-electronics techniques. To obtain a chip with one or several magnetic heads from a card which includes several components or chips, the components must be separated from each other and then the front part of the components which will be next to the polar pieces
10
1
,
10
2
must be machined to give them the rounded shape needed for proper functioning of the head. In
FIG. 2
, the rounded profile is schematically represented by the line
26
.
FIG. 3
schematically shows a section view of a head along a line AA which goes through one of the conducting strips and one of the branches of the magnetic circuit as well as the head support. This figure shows a substrate
30
, silicon for example, with one of the polar pieces
10
1
or
10
2
, a magnetic branch
16
1
or
16
2
, a conducting strip
22
1
or
22
2
, and the electrical connection studs
24
1
,
24
2
. This unit is covered by a superstrate
40
, in silicon for example. At the front of the head, the surface
26
, called the bearing surface, has an appropriately rounded shape and a height h which is reduced with respect to the total thickness of the unit. At the back, the superstrate
40
is disengaged to leave the electrical connection studs
24
1
,
24
2
exposed.
The chip is mounted on a base
45
, made of brass for example, on one of the sides of which (front side or back side) there is a rigid printed circuit
46
, which is electrically linked to the chip by stranded wires
48
1
,
48
2
. The printed circuit
46
links the head to the electronic circuits which control writing and/or reading.
In an assembly of this type, four welds must be done for a chip containing a single head: two welds of the stranded wires
48
1
,
48
2
on the studs of the printed circuit
46
and two other welds on the connection studs
24
1
,
24
2
, on the back of the chip. If the chip contains a double head, there will be four connection studs on the back of the head and eight welds will be needed.
The existence of these welds increases the resistance of the overall circuit. The soldering, done manually, using ultrasound with microscope observation for example, is expensive. It also limits the speed of production and requires qualified personnel. These operations are particularly delicate when the size of the head is small: they must then be done with micro-handling tools to arrange the wires on the studs. Since the general trend is toward smaller heads, these difficulties will only become greater.
This invention aims to overcome these drawbacks.
SUMMARY OF THE INVENTION
To this end, the invention proposes a chip-base assembly which avoids the use of stranded wires. The invention also proposes a process for making this assembly, which can be automated. According to the invention, the rigid printed circuit (
46
in
FIG. 3
) is eliminated and a printed circuit with conducting tracks which have ends which come directly into contact with the connection studs of the chip is used. At their opposite ends, the conducting tracks are linked to the electronic circuit which controls the chip.
More precisely, this invention involves an assembly for chip(s) with magnetic head(s), the aforesaid chip including a rear edge equipped with electrical connection studs, the assembly also including a base with upper and lower sides as well as front and back edges, the chip being attached to the front edge of the upper side of the base, this assembly being characterised in that it also includes a printed circuit having an upper side and a lower side, a front edge and a back edge as well as an opening or a notch, this printed circuit being covered, on its lower side, by conducting tracks with front ends soldered to the electrical connection studs of the chip, the printed circuit going under the base and having its upper side against the lower side of the base, the rear part of the base and the rear part of the printed circuit being attached to each other by a means of attachment, the opening or notch of the printed circuit being crossed by the base.
The means of attachment could be glue or a screw. In the latter case, this screw could attach the printed circuit to the base and then attach both of them to a drum.
The printed circuit can be flexible and made of Mylar, Kapton, polyimide or any other material suitable for such circuits. But the printed circuit may also be rigid (for example plastic or other material). The conducting tracks may be photoetched. Their edges may be first covered with a meltable product (tin-lead for example) on the parts facing the electrical connection studs of the chip.
To facilitate the assembling of this unit, the printed circuit can preferably have a notch or opening which is crossed by the base.
The chip can have one or several magnetic heads and each base can be associated with several chips.
This invention also involves a process for making the assembly which has just been described. According to this process:
starting with a chip with at least one magnetic head and with its rear edge equipped with electrical connection studs and a base having upper and lower sides and front and rear edges,
the chip is attached to the front edge of the upper side of the base,
a printed circuit is made with upper and lower sides and front and rear edges with, on the lower side, conducting tracks. A notch or opening is made in the printed circuit with dimensions sufficient for the chip-base unit to go through it,
the chip-base unit is then passed through the notch or opening in the printed circuit and the electrical connection studs of the chip are arranged facing the ends of the conducting tracks of the printed circuit,
the electrical connection studs of the chip are electrically connected with the ends of the conducting tracks of the printed circuit,
part of the base is attached to the printed circuit.
The invention eliminates the connection wires and reduces by half the number of welds to be done for a normal integrated head, thus reducing the number of operations and parts. The electrical resistance of the circuit is also decreased.
The invention process can be automated. For this, there can be a machine with a distributor of heads already mounted on their base (revolver loader type for example) and a printed circuit distributor (pre-printed circuit rol
Albertini Jean-Baptiste
Barrois Gerard
Marillat Roger
Burns Doane , Swecker, Mathis LLP
Commissariat A l'Energie Atomique
Gaffin Jeffrey
Patel I B
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