U.S. patent number 3,725,671 [Application Number 05/090,209] was granted by the patent office on 1973-04-03 for pyrotechnic eradication of microcircuits.
This patent grant is currently assigned to The United States of America as represented by the Secretary of the Navy. Invention is credited to Frank Z. Keister, John B. Rust.
United States Patent |
3,725,671 |
Keister , et al. |
April 3, 1973 |
PYROTECHNIC ERADICATION OF MICROCIRCUITS
Abstract
An anticompromise pyrotechnic eradication thin film circuit
module having in films of perfluoropolymer and metal thereon in
sufficient quantity to produce a pyrotechnic reaction to cause heat
of fusion of the metals of the thin film circuit to destroy the
circuit beyond recognition and repair.
Inventors: |
Keister; Frank Z. (Culver City,
CA), Rust; John B. (Malibu, CA) |
Assignee: |
The United States of America as
represented by the Secretary of the Navy (N/A)
|
Family
ID: |
22221788 |
Appl.
No.: |
05/090,209 |
Filed: |
November 2, 1970 |
Current U.S.
Class: |
327/525; 149/37;
174/253; 174/256; 361/765; 361/779; 257/E27.009; 102/202.8; 149/87;
174/254; 338/308; 326/8; 327/564; 327/567; 257/922 |
Current CPC
Class: |
H01L
23/573 (20130101); G06K 19/07372 (20130101); C06B
43/00 (20130101); F41H 13/00 (20130101); H01L
27/02 (20130101); G06K 19/073 (20130101); C06B
27/00 (20130101); G06K 19/07381 (20130101); H05K
1/0293 (20130101); H01L 2924/15153 (20130101); H05K
2203/175 (20130101); H01L 2924/19107 (20130101); H05K
1/0275 (20130101); H01L 2224/73265 (20130101); H05K
2201/0317 (20130101); H01L 2224/48091 (20130101); Y10S
257/922 (20130101); H01L 2224/32225 (20130101); H01L
2224/48091 (20130101); H01L 2224/73265 (20130101); H01L
2224/48227 (20130101); H01L 2924/15165 (20130101); H05K
2203/1163 (20130101); H01L 2924/00014 (20130101); H01L
2224/32225 (20130101); H01L 2924/00 (20130101); H01L
2224/48227 (20130101) |
Current International
Class: |
F41H
13/00 (20060101); H01L 23/58 (20060101); G06K
19/073 (20060101); H01L 27/02 (20060101); C06B
43/00 (20060101); C06B 27/00 (20060101); H05K
1/00 (20060101); C06b 019/02 (); H03k 017/84 ();
H05k 001/18 () |
Field of
Search: |
;317/80,11CE,258
;307/298,202,299,303 ;174/68.5 ;109/33 ;149/37 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Borchelt; Benjamin A.
Assistant Examiner: Birmiel; H. A.
Claims
We claim:
1. A pyrotechnic eradication means compatible with a microcircuit
on a circuit film module comprising:
a microcircuit substrate;
a microcircuit film supported on said microcircuit substrate;
and
pyrotechnic materials coating one surface of said microcircuit film
with electrical conductors connecting said pyrotechnic materials
and said microcircuit film adapted to conduct a current to energize
said pyrotechnic material, said pyrotechnic materials being from a
group of perfluoropolymers high in fluorine content and metals
whereby said microcircuit film can be destroyed by exothermic
reaction when said pyrotechnic materials are heated to the ignition
point by electrical energization.
2. A pyrotechnic eradication means as set forth in claim 1
wherein
said pyrotechnic material coating said microcircuit film operates
as a bonding agent between said microcircuit substrate and said
microcircuit film, said perfluoropolymer material having electrical
insulating qualities for said microcircuit film.
3. A pyrotechnic eradication means as set forth in claim 1
wherein
said pyrotechnic materials coating overlies said microcircuit film,
said perfluoropolymer operating as an electrical insulating
material.
4. A pyrotechnic eradication means as set forth in claim 1
wherein
said pyrotechnic material of perfluoropolymers and powdered metals
are from the group mixtures consisting of lithium fluoride, sodium
fluoride, potassium fluoride, beryllium fluoride, magnesium
fluoride, calcium fluoride, boron fluoride, aluminum fluoride,
scandium fluoride, yttrium fluoride, silicon fluoride, titanium
trifluoride, and zirconium fluoride.
5. A pyrotechnic eradication means as set forth in claim 1
wherein
said perfluoropolymer material is of the group consisting of
polyfluoroethylene and perfluoroalkylenetriazine and said metal is
of the group consisting of aluminum and magnesium.
Description
BACKGROUND OF THE INVENTION
This invention relates to anticompromise circuits and more
particularly to self-destruct circuit modules in which the
destructive materials are mixtures or deposited film layers of
perfluoropolymer and metal to produce pyrotechnic reaction.
Circuit destruction devices are known that use explosives or
combustible materials packaged to be placed adjacent the circuit
components to be destroyed. The explosion or fire created thereby
was intended to damage or destroy the circuits beyond recognition
or repair. The disadvantages of such destruct systems were that the
destruction was usually local and the package was too bulky to
position at strategic places of the circuit where space was at a
premium. One known circuit destruct utilizes an oxidant in a
combustible thin film layer over or under a thin film circuit to
destroy the circuit when a pyrotechnic package placed somewhere on
the circuit module is ignited. Another known method of circuit
destruction lies in the use of acids which can be set free to etch
away the thin film circuit.
SUMMARY OF THE INVENTION
In the present invention a self-destruct mixture or combination of
thin film materials are made compatible with, and become an
integral part of, the thin film circuit on a module. These
self-destruct materials are taken from a group of
perfluoropolymers, having as high a fluorine content as possible,
and metals which may best be used for this purpose in powdered
form. While there are many perfluoropolymers and metals to choose
from, one good example may be polyfluoroethylene, known as Teflon,
and magnesium or aluminum powdered metals. It is accordingly a
general object of this invention to provide a pyrotechnic destruct
film coating for thin film circuit modules to destroy the circuit
beyond recognition, use, or reconstruction at will to prevent
circuit compromise with enemy forces.
DESCRIPTION OF THE DRAWING
These and other objects and the attendant advantages, features, and
uses will become more apparent to those skilled in the art as a
more detailed description proceeds when considered along with the
accompanying drawing, in which:
FIG. 1 is a cross section of a circuit module in which the
pyrotechnic material is incorporated as a die bond material between
a semiconductor chip and the microcircuit substrate;
FIG. 2 is a cross-sectional view of a thin film flat pack in which
the pyrotechnic material is used as the bonding agent between the
microcircuit and the substrate;
FIG. 3 is a cross-sectional view of a thin film circuit module with
the pyrotechnic material on top of the microcircuit; and
FIG. 4 is a cross section of a thin film circuit module in which
the pyrotechnic material is deposited directly on the microcircuit
as alternate thin film layers.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring more particularly to FIG. 1, a microcircuit substrate 10
is mounted on a substrate board or support 11. A microcircuit thin
film or thick film 12 is deposited on the microcircuit substrate 10
with a pyrotechnic material 13 of perfluoropolymer and metal
deposited or pasted on top to support a semiconductor element such
as a semiconductor chip 14. A separate circuit in the microcircuit
coupled through appropriate switch means to a voltage source is
connected by ignition wire 15 to the pyrotechnic film to produce
pyrotechnic reaction and destruction of the microcircuit whenever
it is desirable to do so.
Referring to FIG. 2, like reference characters referring to like
parts, a flatpack substrate 20 has the pyrotechnic material 13 used
to bond a thin film or thick film microcircuit 21 thereon with the
ignition wire 15 connecting it with terminals 22 on substrate 20. A
semiconductor chip 14 may also rest on the top of the microcircuit
film 21 and be electrically connected by connecting wires 23. The
microcircuit film 21 is connected to terminals, one of which is
illustrated in this figure by the reference character 24. The
pyrotechnic material 13 of perfluoropolymer and powdered metal will
destroy the microcircuit film 21 beyond recognition or use.
Referring to FIG. 3, the thin film or thick film microcircuit 21 is
deposited on the microcircuit substrate 20. An electrical
insulating film 25 is deposited over the microcircuit film 21 and
the pyrotechnic film or coating 13 is deposited over the insulating
film 25. The pyrotechnic film 13 has leads 26 adapted for
connection to the microcircuit or to an external power source, as
desired, to energize and ignite the pyrotechnic material whenever
desirable and feasible to do so to avoid compromise.
Referring to FIG. 4, the thin film or thick film microcircuit 21 is
deposited on the microcircuit substrate 20 and the pyrotechnic
material is deposited in layers. The first layer is a
perfluoropolymer film 30 with a film of aluminum 31 deposited
thereover. The aluminum thin film may be connected electrically
through a switch to a voltage source or a top layer of nichrome 32
may be deposited over the aluminum and connected to the destruct
circuit, as desired. The nichrome film will act as igniter for the
pyrotechnic films of aluminum and perfluoropolymer.
The perfluoropolymer and metal mixtures providing the pyrotechnic
reactions may be of any of the well known mixtures as listed
hereinbelow although best results are acquired where the fluorine
content is high. Two good examples of high fluorine content are
polyfluoroethylene, commonly known as TEFLON, and
perfluoroalkylenetriazine. Good powdered metal constituents are
magnesium and aluminum. The following table discloses the
pyrotechnic reaction of heat generated by several combinations of
metals and fluorides:
TABLE I
Heats of Formation of Fluorides and Enthalpy of Reaction of M +
Teflon -- Metal Fluoride Carbon. The Compounds Listed are in Their
Solid State Unless Noted Otherwise. Compound .DELTA.H.sub.f
.degree. (298.degree.K) (Kcal/mole) Reaction of Element With Teflon
.DELTA.H.degre e. (reaction 298.degree.K) (BTU/lb)
GROUP I, ALKALI METALS
LiF -146 -5492 NaF -136 -3277 KF -135 -2431 GROUP II,
ALKALINE-EARTH METALS BeF.sub.2 (Liquid) -227 -3961 MgF.sub.2 - 266
-4105 CaF.sub.2 - 290 -3853
GROUP III, BORON-ALUMINUM GROUP
BF.sub.3 - 274 -2683 AlF.sub.3 - 323 -3133 ScF.sub.3 - 367 -3313 Y
F.sub.3 - 397 -2755
GROUP IV, CARBON-TITANIUM GROUP
SiF.sub.4 - 371 -2467 TiF.sub.3 - 315 -2359 ZrF.sub.4 - 445
-2359
this table shows the standard enthalpy change for various
Teflon-metal and Teflon-nonmetal systems. Examination of this table
shows that magnesium-Teflon (-4105 BTU/lb.) and aluminum-Teflon
(-3133 BTU/lb.) are extremely efficient systems based on their high
enthalpy change of reaction (.DELTA.H.degree.). These systems are
triggered by heat and once started are self-sustaining. The
particles of the reactants should be intimately mixed, finely
divided, and preferably of colloidal dimensions.
Although Teflon is the polymer which has been emphasized, other
fluorine-containing polymers are also applicable. A polymer of
perfluoropropylene epoxide, when mixed with aluminum powder, can be
ignited and burns rapidly with intense heat. This polymer is
available as a very viscous oil. It can be easily mixed with
powdered metals and the mixture can be made into a stiff putty or
dry paste. The polymer should be high in fluorine, should be stable
in storage without any chance of spontaneous ignition, and must be
malleable so that it can be easily mixed with metal powder.
The above-noted preferred embodiments of the eradication film or
coating provide heat and flame of sufficient intensity to fuse,
vaporize, or otherwise eradicate all circuit identification. This
fusion is accomplished with a small quantity of reactant in a
compatible integral part of the microcircuit. The reliability of
the microcircuit or semiconductor devices attached to the
microcircuit is not adversely affected by the reactants prior to
eradication. These reactants are non-corrosive and are stable and
when reaction is initiated, the pyrotechnic reaction takes place
without explosion. The reaction of these destruct films evolves
with only a minimum quantity of gas so that built up pressures will
not shatter device packages or harm adjacent, non-critical
circuits.
This eradication means is applicable for electronic circuits and
electronic systems (especially those which are microminiaturized)
which are of a critical nature, such that disclosure to enemy
forces can be avoided. Should the unfriendly party threaten,
capture, or attempt to learn the identity of the circuit, the
self-destruct mode could be switched and the perfluoropolymer-metal
pyrotechnic reaction would destroy the critical portions of the
anticompromise circuit.
While many modifications may be made in the combinations of
perfluoropolymers and powdered metals and in the degree or extent
of volume, it is to be understood that we desire to be limited in
the spirit of our invention only by the scope of the appended
claims.
* * * * *