US 3428954 A
Description (OCR text may contain errors)
Feb. 18. 1969 c. A. M. DAVID ELEMENT FOR RESISTIVE PERMANENT MEMORY Sheet Filed March 7, 1966 MEI H 2 A A A Fig.1
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W.- Mmwmwfi .BY 3%)? Feb. 18, 1969 c. A. M. DAVID ELEMENT FOR RESISTIVE PERMANENT MEMORY Z of 5' Sheet Filed March 7, 1966 Feb. 18, 1969 c. A. M. DAVID 3,428,954
ELEMENT FOR RESISTIVE PERMANENT MEMORY Filed March 7, 1966 Sheet :3 of
United States Patent Ofice 3,428,954 ELEMENT FOR RESISTIVE PERMANENT MEMORY Charles Antoine Marius David, Charenton, France, as-
signor to Societe Industrielle Bull-General Electric (Societe Anonyme), Paris, France Filed Mar. 7, 1966, Ser. No. 532,172
Claims priority, appliclatiogsl rance, Apr. 2, 1965,
US. Cl. 340-173 7 Claims Int. Cl. H01f 40/00 This invention relates to improvements in resistivecoupling permanent memories, which improvements concern the structure of these devices and the manner in which they are produced.
In data-processing equipment and in telecommunications, constantly increasing use is being made of devices adapted to store or code constant or fixed data, which are permanently stored in the design of these devices. The latter must meet various requirements; short access cycle time, high storage capacity, low cost of manufacture and maintenance and acceptable reliability.
The invention has for its object to improve the construction of a permanent store comprising resistors, the principle of which is known, for the purpose of reducing its cost by almost entirely mechanising its manufacture. It follows that mass production becomes possible, with the further advantage that the danger of code errors inherent in hand production are completely eliminated.
Another object of the invention is to provide a permanent memory device of limited overall dimensions, which lends itself to the modification of word codes in cases where a small quantity of stored characters must be modified in the course of the period of development of a model or prototype, i.e. before mass production.
Within the scope of the storage capacities usually necessary, it is standard practice to build up a permanent memory device from a number of memory planes, each plane having a matrix structure. Such a plane will also be referred to as a storage element in the following.
In accordance with the invention, therefore, there is provided a resistive-coupling permanent memory element which comprises a plurality of parallel word conductors extending in one direction, a plurality of bit conductors extending in a direction perpendicular to the aforesaid direction, their number being equal to the maximum number of bits per word, and resistors which are individually connected between conductors belonging to the said two pluralities of conductors, the said element consisting of a plate of insulating material, which plate comprises (1) A number of rows of holes, which extend in a first one of the said directions,
(2) A number of rows of resistive elements disposed on one side of a first face of the plate, each of these elements being composed of an insulating support on which there are deposited conductive films and a number p of electrically resistive films, so arranged that one end of each resistor is connected to a common longitudinal conductive film, as also a number p+2 of conductive wires, with p wires having one end connected to the other end of a resistor, and two wires connected to the ends of the common conductive film, all of these wires passing through holes in the plate and emerging on the second face, and,
(3) Elements of printed conductor circuits attached to the second face of the plate, these elements comprising groups of bit conductors extending in the second direction between the columns of holes, as also welding studs each surrounding one hole in the plate, some of these welding studs being electrically connected to the adjacent printed conductors in each group in accordance with the configurations of a particular binary value in the stored 3,428,954 Patented Feb. 18, 1969 words, and other soldering studs permitting the connection of the end wires belonging to two neighbouring resistive elements, so that in one row of elements the longitudinal conductive films form an uninterrupted conductor.
It is to be noted that the resistive films mentioned in the foregoing preferably have a fixed or ohmic resistance, but that the principles of design underlying the invention could also be advantageously applied in the case of a device based upon the use of non-linear resistances, and even resistances dependent upon the polarity of the applied voltages, that is to say, of semiconductor diodes. It is sufiicient that it should be possible to produce the latter in the form of deposits of small volume.
Fora better understanding of the invention and to show how it may be carried into effect, the same will now be described, by way of example, with reference to the accompanying drawings, in which:
FIGURE 1 is the electric circuit diagram of a permanent memory comprising resistors, which will enable the principle of operation of the said memory to be recalled;
FIGURE 2 is a fragmentary view of a permanent memory device according to the invention, for example as seen from the front;
FIGURE 3 is a fragmentary view of the same device as seen from the opposite side;
FIGURES 4A, 4B and 4C are element;
FIGURE 5 is a view of a detail, drawn to an enlarged scale, of the deposited films constituting a resistive element, and
FIGURE 6 is a fragmentary view, drawn to an enlarged s l:ale, of the printed circuits on a plate forming a memory p ane.
FIGURE 1 will serve to recall the principle on which a resistive-coupling permanent memory device, which may also be regarded as a coding device, is based. The horizontal lines 10 represent word conductors. The vertical lines such as 11 represent bit conductors. A resistor such as 12 corresponds to each crossing of a word conductor (with a bit conductor. In all the horizontal rows, each resistor has one end connected to a word conductor. The other end of some of the resistors is connected to a bit conductor, for example as may be seen at 13. It may be agreed that, in any word of a horizontal row, each bit conductor is allocated to a binary position or storage position or bit. In addition, a binary l is stored in any binary position provided with a connection 13, and com sequently a binary nought is stored in the positions not provided with such a connection.
An output amplifier 14 is connected to each bit conductor 11. During operation, voltage is selectively applied to a single word conductor by means of any appropriate selecting system. In FIGURE 1, only one group of members provided to feed a single word conductor is shown, in order to simplify the drawing. These members comprise a switch 15, a diode 16 and a transformer 17, the secondary winding of which is connected to a word wire. The terminal 18 may be connected to a voltage source or to a pulse generator. When a switch 15 is closed, the associated Word conductor may receive a voltage pulse. An output pulse will be supplied by each of the amplifiers 14 of the binary positions in which a 1 is stored in the selected word. The signal-to-noise ratio is very satisfactory provided that the input resistance of each output amplifier is sufliciently low in relation to the ohmic resistance of a resistor 12. This resistance may be between 1000 and 1500 ohms, for example.
In practice, the storage capacity of a usual permanent memory is much greater than that which would correthree views of a resistive spond to the diagram of FIGURE 1, which has been intentionally limited. For example, it may be necessary to store 512 words of 64 bits each. The permanent memory device may be constructed in the form of a number of memory planes, which are connected together on the one hand by securing means and on the other hand by electrical links. Thus, a capacity of 512 words may be obtained by means of 8 memory planes, each with M=64 words of N :64 bits, for example.
It is possible by means of the invention to produce such memory planes with a small volume and by almost entirely mechanised methods of manufacture. FIGURES 2 and 3 show fragmentary views of a permanent memory device. In order to simplify the drawing, only three memory planes 19 have been shown. Each memory plane is composed of a rectangular base plate 20. Since each base plate has a vertical axis of symmetry and a horizontal axis of symmetry, the fragmentary views are sufficient for their representation. It will thus be readily understood that each of the four corners of a plate 20 is formed with a hole 21 (see FIGURE 6), by virtue of which the plates may be secured together by means of bolts 22 and distance rings 23.
It may be agreed that that face of the plates 20 which is visible in FIGURE 2 is the front face AV. Resistive elements 24 are disposed on each side of each plate 20. The said resistive elements are distributed in 64 horizontal rows, each row comprising eight elements 24 in all, which are aligned at a small distance apart. Each plate 20 also serves as a support for the diodes and the transformers, a pair of which is shown in FIGURE 1. There are therefore thirty-two diodes 16 and thirty-two transformers 17 on each of the right-hand and left-hand vertical sides of a plate 20. Each transformer is constructed essentially around a high-frequency toroidal ferrite core.
FIGURE 3 also shows only one corner of three memory planes and that face of the plates 20 which is visible is the rear face AR. This face comprises printed circuits which will hereinafter be considered in greater detail.
The construction of a resistive element 24 may be explained with reference to FIGURES 4A to 4C. It has been chosen to include in such an element eight resistors, one end of which must be connected to a common conductor, which constitutes a section of a word conductor.
The member constituting the supporting equipment of a modular resistor element is a thin plate 25 of elongate form consisting of insulating material, i.e. glass or ceramics, which offers good resistance to the temperatures encountered during welding operations. The eight resistors 26 are each represented by a thick line. In the deposited conductors 27 (hatched surfaces), there may be distinguished a longitudinal strip 28 and two vertical strips 29 which form with two end lugs 30 a common conductor. In addition, ten junction wires such as 311 and 31B are provided. The upper end of each of these wires is soldered to a lug 30.
The cost of such resistive elements may be very low if they are produced on a large scale. Of all the possible methods of manufacture, there may be mentioned two which give excellent results:
(a) Deposition or spraying of a thin layer of a body or mixture whose resistivity is adapted to the resistance to be finally obtained, with the contour shown in solid lines in FIGURE 5, through a mask or stencil.
(b) Sticking of a thin insulating strip covering the eight intermediate small strips over the width H, which is bounded by the dash-dotted lines.
(c) Metallisation of that part of the resistive layer which is not masked by the insulating strip, this part then forming a conductor of substantially zero resistance (dipping into a molten tin bath).
(a) Deposition (spraying, evaporation in vacuo, etc.,) of a thin layer of a conductive metal (copper, nickel, etc.,) through an appropriate mast, with the solid-lined contour of FIGURE 5, except for eight interruptions of height H, between the dash-dotted lines.
(b) Deposition of the eight resistive elements over a height greater than H in order to connect them electrically to the corresponding ends of the small vertical conductive strips.
One or other of these methods, by which resistances differing at most by or -20% of the nominal value may be obtained, may he succeeded by the following phases of operation.
(a) Application of a thin insulating strip over the whole length of the element and over a width defined by the lines A and B in FIGURE 5.
(b) Soldering of the ends of the wires 311, 31E to the lugs 30, for example by dipping into a molten tin bath.
(c) Coating of the element with a protective insulating material limited substantially to the height of the plate 25.
Before assembly on a memory plane 19, each resistive element 24 is tested to check that the value of each resistor 26 is acceptable. If only one of the resistors is defective, the element is rejected. It will be obvious that the number of resistors 26, i.e. eight, which has been shown, has no limiting character, since it is possible to provide a larger number of such resistors, for example 16, in a modular resistive element provided that increased fragility is not to be feared by reason of the increase in the length of an element, and that the percentage of rejected elements is low.
The structure of a memory plane 19 may be examined with reference to FIGURE 6, which shows only one lower right-hand corner of the rear face of the said plane, this designation being valid only with respect to the view of FIGURE 2.
The base plate 20, which may be a glass-epoxy resin sheet having a thickness of 0.8 mm., is formed with a large number of holes or perforations 32. These holes are arranged in horizontal rows and vertical columns, thus forming a grid, for example with a unifom spacing of 2.54 mm. These holes may be pierced or punched on an automatic machine provided for this purpose.
In each horizontal row, there must first be provided eighty holes, since each of the eight resistive elements 24 comprises ten wires or stems 311, "31E. Other holes are necessary in the present case, for mounting other components on a memory plane.
The printed circuits disposed on the rear face of the plate 20 are represented by thick black lines. There will be seen the vertical conductors 33, which correspond to the bit conductors 11 of FIGURE 1. They are distributed in groups of eight. Each conductor 33 is termi nated by a soldering section 34. In each pair of conductors 33, one has a section 34 situated on the side of the upper edge and the other a section 34 situated on the side of the lower edge of the plate 20. Each soldering section 34 coincides with a small recess 35 in one edge of the plate 20. There may be passed through this recess and soldered a wire such as 44 (FIGURE 3) serving for electrically connecting the soldering sections of the eight memory planes in the corresponding binary positions.
There exist 4096 soldering studs such as 36, each surrounding a hole for the passage of the wires of the resistive elements. They are situated close to a conductor 33. Some of the studs 36 are connected to the neighbouring conductor 33 by a simple link such as 37. These links, which correspond to those shown at 13 in FIGURE 1, must exist in the binary positions containing a 1 for the word row under consideration.
Provided between the groups of conductors 33 are soldering studs having two holes, such as 38. Each of these studs is intended to establish the connection of the end wires 31E (FIGU-RE 4A) belonging to two neighbouring resistive elements 24. It follows that, after soldering, there is obtained an uninterrupted conductor which corresponds to one of the word wires shown in FIG- URE 1.
The soldering studs 39, 40 and 41 serve to connect the diodes 16 and the transformers 17. These soldering studs are alternately disposed to the right or to the left, depending upon whether the corresponding row is of even or odd order.
Each stud 39 has a hole for the passage of a first wire of a diode 16. It is intended to be connected by means not shown to a selecting switch such as (FIGURE 1). In each two-holed stud 40, the left-hand hole allows the passage of the second wire of a diode 16, while the wire of a first end of the primary winding of a transformer 17 passes through the right-hand hole in the said stud. The wire of the second end of the primary winding of the said transformer passes through a neighbouring hole surrounded by the vertical common conductor 42.
In each two-holed stud 41, the right-hand hole is used for the passage of and end wire 31E of the first element 24 of the row, while the left-hand hole is used for the passage of a wire from a first end of the secondary winding of the transformer 17. The Wire of the second end of the secondary winding of the said transformer passes through a neighbouring hole surrounded by the vertical common conductor 43.
The construction just described for the memory planes lends itself to a succession of automatic operations performed on appropriate machines. These operations may commence with the mechanised production of the block which will be employed for the photogravure of the printed circuits. Thus, a drawing machine may proceed with the selection of elemental blocks. There may be one elemental block for a stud 36 beside a conductor portion 33, another for a stud 36 with a link 37 to a conductor portion 33, two other blocks for portions of two-holed studs 38, and so on. The selection of the appropriate elemental blocks may be controlled in step with the intermittent movements of the reproduction sheet, by a magnetic tape or punched tape, on which are previously recorded the various words which are to constitute the contents of the permanent memory.
When the printed circuits have been obtained by any appropriate method, all the components, including the 512 elements 24, are situated on the side of the front face of the memory plane 19 by introducing the ends of the wires 31 into the appropriate holes. With the aid of a special machine, the ends of the wires extending beyond the rear face may be cut at a uniform distance from this face and thereafter all bent over in the same direction, i.e. in a direction parallel to the conductors 33. This explains the elongate and asymmetrical form of the studs 36.
Finally, the soldering of the wires of the components to the soldering studs of the circuits printed on the rear face of a memory plane may be carried out with a molten tin bath by the known surge method, in which a wave on the surface of the bath moves in the direction of the conductors 33.
The construction just described is completely suitable for a permanent memory whose access cycle time is about 0.35 microsecond. When an even shorter cycle time is required in use, for example 0.15 microsecond, an additional step may be resorted to. This step consists in providing the front face of each memory plane with a thin layer of a metal which is a good conductor, for example copper, this sheet being connected to earth. Of course, to each location of a hole for the passage of a wire of a resistive element or other component, the
earth sheet must have a hole of sufficient diameter to prevent any undesirable contact.
It will readily be appreciated that, since the links 37 (FIGURE 6') are positioned during the production of the photogravure block on an automatic programmecontrolled machine, there is no longer any possibility of errors in respect of the configurations of 1 and of O in the stored words. Despite this safety, the construction according to the invention affords the advantage that, where necessary, these links 37 may be modified by manual means, after the printed circuits have been produced. It is possible to remove a link 37 by scratching the copper layer between a vertical conductor 33 and the stud 36 in the position concerned. Conversely, a link 37 may be added by depositing a drop of solder in the required place. It is clear that these modifications will be of no interest unless they are few in number, since otherwise it is more advantageous to produce a fresh block.
If it is found that a relatively large portion of a word comprises only zeros, one or more simplified elements 24 may be used. In this case, there Will be no resistive element 26 (FIGURE 4A), so that there remains only the longitudinal strip 28, the small strips 29 and the end lugs 30, to which two end wires 31E are soldered. Thus, such an element is a little less costly than a normal resistive element and it nevertheless makes it possible to ensure continuity of the word conductor of which it forms part.
If the diodes 16 and the transformers 17 were not mounted on memory planes, the printed circuit elements such as 42, 40, 43 (FIGURE 6) could be omitted and the soldering studs 41 replaced by the studs 39.
It is to be noted that the principles of construction defined in the foregoing retain their advantages with any form of matrix element including a large number of members involving a resistive effect. It is of little importance whether each coupling member has a purely ohmic resistance or a non-linear resistance, or a resistance varying with the direction of flow of the current through it. It is sufficient for each member to have the required characteristics when it is constructed in the form of one or more deposits whose dimensions are appropriate to the constitution of resistive elements of relatively small volume.
On the other hand, the terms word conductor and bit conductor must not be interpreted in a restrictive sense. Thus, referring to FIGURE 1, all the resistors in each resistor column 12 could have one end connected to a vertical wire 11, and the connections of the other ends, depending upon the word codes, could affect the horizontal wires 10. This obviously does not change the operation of the memory, but affects only the programming which controls the production of the photogravure block.
What is claimed is:
1. As an article of manufacture, a constructional element for a resistive coupling permanent memory, which has a first set of M word conductors extending in a first direction, a second set of N bit conductors extending in a second transverse direction and resistive couplings at some cross-points of these conductors, said constructional element comprising:
an insulating plate bearing on a first face printed circuit parts, the latter including a number N of printed conductive strips extending in said second direction and arranged in several groups each of p strips, a number M N of printed soldering studs grid-like arranged, so that each column of M studs is adjacent to one of said strips, each single stud surrounding a hole through said plate, and M series of printed double soldering studs disposed between said groups of strips, each double stud surrounding two holes through said plate;
a number M of groups of resistive elements disposed on the side of the second face of said plate, each resistive element including p resistive deposits on an insulating slab, p-I-Z parallel conductive wires soldered so that there are p wires connected each to a deposit end and the two other extreme wires are connected in common to the other end of said deposits, one extremity of each of said extreme wires passing through a hole and being soldered to a double stud, and one extremity of each of said p wires passing through a hole and being soldered to a single stud,
and some of said single studs being electrically connected to an adjacent strip at each point where a resistive coupling is to be made.
2. A constructional element according to claim 1, wherein each of said resistive elements comprises several deposited conductive elements, one of which extends on the length of said slab and is soldered to said extreme wires.
3. A constructional element according to claim 2, wherein one at least of said resistive elements is devoid of resistive deposits at places where there is no need of resistive couplings with p corresponding strips.
4. As an article of manufacture, a permanent memory block unit composed of a plurality of stacked memory planes, which has a first set of M word conductors extending in a first direction, a second set of N bit conductors extending in a second transverse direction and resistive couplings at some cross-points of these conductors, each of said memory planes comprising:
an insulating plate bearing on a first face printed circuit parts, the latter including a number N of printed conductive strips extending in said second direction and arranged in several groups each of p strips, a number M N of printed soldering studs grid-like arranged so that each column of M studs is adjacent to one of said strips, each single stud surrounding a hole through said plate, and M series of printed double soldering studs disposed between said groups of strips, each double stud surrounding two holes through said plate;
a number M of groups of resistive elements disposed on the side of the second face of said plate, each resistive element including p resistive deposits on an insulating slab, p+2 parallel conductive wires soldered so that there are p wires connected each to a deposit end and the two other extreme wires are connected in common to the other end of said deposits, one extremity of each of said extreme wires passing through a hole and being soldered to a double stud, and one extremity of each of said p wires passing through a hole and being soldered to a single stud,
and some of said single studs being electrically connected to an adjacent strip at each point where a resistive coupling is to be made.
5. A memory block unit according to claim 4, wherein on each memory plane, each of said strips extends up to an edge of said plate and terminates in a terminal printed stud, and wherein corresponding terminal studs of several memory planes are connected together by a soldered conductor wire.
6. A memory block unit according to claim 4, wherein each of said resistive elements comprises several deposited conductive elements, one of which extends on the length of said slab and is soldered to said extreme wires.
7. A memory block unit according to claim 6, wherein one at least of said resistive elements is devoid of resistive deposits at places where there is no need of resistive couplings with p corresponding strips.
References Cited UNITED STATES PATENTS 5/1967 Beelitz 17468.5 7/1968 Garcia 317-101 X