GB2059187A - Electrical connector - Google Patents

Abstract

A connector for electrically mating closely spaced parallel electrical conductors (12,16) on rigid (14) and flexible (10) substrates is has many finely dimensioned conductors (12,16) on one substrate accurately mated with preselected ones (16,12) on the other substrate by means of interdigitated elements (18,24,26,28) on one or the other or both of the substrates which ensure accurate connection and yet permit a visual alignment at assembly. The interdigitated elements on one substrate are situated in or aligned with gaps between the conductors on the one substrate and fit between the conductors of the other substrate or between further interdigitating elements (28) aligned with the conductor on the other substrate. <IMAGE>

Description

SPECIFICATION High density electrical connector Technical field The present invention relates to connectors for joining high density electrical conductors of the type having a spacing of about 39.4 per cm (100 per inch) or finer. These densely packed conductors have been used in applications such as cash registers, computers, thermal printers and the like, where leads from miniaturized circuit elements require connection to other elements of the device. Due to the very close spacing of the conductors, simple apparatus and assembly techniques for making electrical connections have been sought for some time. Particularly, the need to very accurately registertiny mating conductors has been felt.

Background art Numerous attempts have been made to solve the problem of making such connectors, which typically are only a few thousandths of a centimeter in height, in addition to being closely packed. For example, Joyce discloses in U.S. Patent No. 3,421,961 a type of connector in which a flexible element having a plurality of closely spaced conductors is glued into place on a rigid thermal print head having a corresponding plurality of conductors. Special jigs are required to ensure proper mating of the conductors. Niemirovich disclosed another high density connector in U.S. Patent No.3,894,329 for which a complex manufacturing process is required. Cook shows a technique for self-aligning integrated circuits in U.S. Patent No. 4,056,681; however, the density of the connector is rather low.

Disclosure of the invention The present invention concerns a very simple structure for mating high density electrical conductors. First and second substrates are provided with pluralities of essentially parallel electrical conductors. Interdigitating elements are located on at least one of the substrates in position to fit between the conductors on the other substrate when the two are pressed together. Simple visual alignment is possible since the interdigitating elements ensure proper mating of the conductors.

Brief description of the drawings Figure 1 shows an embodiment of the invention in which interdigitating elements are provided on only one substrate, located between and axially spaced from the conductors.

Figure 2 shows another embodiment of the invention in which the interdigitating elements extend at least partially between the conductors.

Figure 3 shows yet another embodiment of the invention in which the interdigitating elements are formed from the conductors on both substrates, one set of interdigitating elements being aligned with the conductors and one being between the conductors.

Figures 4 and 5 show schematic side views of modes of assembling the connector of Figure 1.

Figure shows a schematic side view of a mode of assembling the connector of Figure 2.

Figure 7 shows a schematic side view of a mode of assembling the connector of Figure 3.

Figure 8 shows a sectional view taken along lines 8-8 in Figures 4,5 and 6.

Figure 9 shows a sectional view taken along lines 9-9 in Figure 7.

Figure 10 shows a sectional view taken along line 10-10 in Figure 7. - Best mode for carrying out the invention The following is a detailed description of the preferred embodiment of the invention, reference being made to the drawing in which like reference numerals identify like elements of structure in each of the several Figures.

Figure 1 shows a plan view of the two major structural elements comprising the electrical connector according to the present invention. A first electrically insulating substrate 10 is provided which may be made from a flexible plastic film such as Mylar (Registered Trade Mark) or Kapton. A plurality of elongated, essentially parallel electrical conductors or tracks 12 are deposited on substrate 10 by means such as plating, conventional photolithographic techniques, silk screening and the like. Conductors 12 are very small in dimension, being spaced approximately at from 40 to 80 conductors per centimeter (100 to 200 per inch). Where the spacing is about 40 per centimeter, conductors 12 are typically in the range of 0.00254 to 0.00762 centimeters in height and approximately 0.0127 centimeters wide with equal spcing between adjacent conductors.

A second substrate 14 is provided which may be made from the same material as substrate 10.

Preferably, however, 14 is made from a rigid material such as ceramic, Forsterite or porcelainized steel.

A plurality of essentially parallel conductors 16 is provided on substrate 14, conductors 16 typically being identical to conductors 10 in both dimension and material, though different materials may be used. Also provided on substrate 14 are a plurality of interdigitating elements or tracks 18. Elements 18 are approximately 0.625 centimeters in length; are spaced axially from conductors 16 at a distance of 0.127 to 0.254 centimeters; and are located just opposite the open spaces between conductors 16.

Elements i8 8 are made from a ceramic material or other electrically insulating material which is supplied or deposited on substrate 14 by means such as silk screening, vapor deposition and the like. Elements 18 are sized to fit fairly snugly between conductors 12 when the connector is assembled as shown in Figures 4, and 8 and have a height of from 0.008 to 0.01524 cm.

Due to the presence of interdigitating elements 18, substrate 10 and substrate 14 may be visually aligned during assembly by simply inverting one substrate, preferably the flexible one; placing it on top of the other substrate with the outermost of conductors 12 and 16 visually aligned; and the pressing along interdigitating elements 18 to force them between conductors 12 and thus secure the connection. The plastic film used in the connector typically is transparent to light so that visual alignment of conductors 16 and 16 is facilitated. Where additional assurance of proper alignment is desired, means such as a dot 20 and circle 22 may be provided on the substrates 10 and 14, alignment being assured by placing dot 20 within circle 22 as viewed through the transparent plastic film.

Once the two elements have been manually assembled as just described, they preferably are mechanically clamped as indicated schematically at 30 in Figure 4. As indicated in Figures 4 and 5, substrates 10 and 14 may be joined with their end portions aligned as shown in Figure 4 or with their end portions faced in opposite directions as shown in Figure 5. The embodiment in Figure 5 requires a somewhat different clamp as indicated schematically at 32. Figure 8 shows a sectional view through an assembled connector according to the invention indicating howinterdigitating elements 18fitin between conductors 12 and 14 and how conductors 12 and 14 are brought into appropriate conducting contact.Though simple mechanical contact is adequate for most applications, those skilled in the art will appreciate that the conductors may also be tinned or otherwise prepared to ensure proper contact.

Figure 2 illustrates a further embodiment of the invention in which interdigitating elements 24 are provided which extend from a space axially beyond the ends of conductors 16 to a location physically between the conductors 16. This embodiment is assembled in the same manner as the embodiment of Figures 1,4 and 5 and provides an added advantage of somewhat better electrical insulation between the conductors 12 and 16 in the assembled joint. The connector shown in Figure 2 may be assembled in accordance with the schematic illustration of Figures 5 and 6.

Figure 3 shows a further embodiment of the invention in which interdigitating elements are provided on both substrate 10 and substrate 14. The interdigitating elements 26 on substrate 10 are spaced axially from conductors 12 in a manner similar to that of elements 18 shown in Figure 1 and are also located just opposite the open spaces between conductors 12. Elements 28, on the other hand, are also spaced axially from the conductors 16 but are aligned with conductors 16. In this embodiment, interdigitating elements 26 and 28 may be made from electrically insulating ceramic material as in the case of the embodiments of Figures 1 and 2; however, it is preferred that they be made from the same material as conductors 12 to thereby simplify the manufacturing process.The connector shown in Figure 3 is assembled and clamped by an appropriate means 30 as illustrated in Figure 7 so that elements 26 and 28 interdigitate as illustrated in Figure 10 to provide an appropriate electrical contact between elements 12 and 16 as shown in Figure 9.

Because elements 26 and 28 are made from the same material as conductors 12 and 16, the conductors and interdigitating elements may be deposited or otherwise applied to their substrates in a single manufacturing step.

Industrial applicability The present invention is particularly suited for all applications where high density electrical interconnections must be made. Particularly, the connectors according to the invention are well-suited for use in thermal printing apparatus in which a large number of small thermal stylii are provided for creating alpha-numeric or analog images on a suitable heat sensitive medium. In this, and similar applications, a large number of very small conductors must be quickly and reliably connected to leads coming from other circuitry such as driver circuits for the thermal printer. Also, the circuit according to the present invention is advantageous since it easily can be assembled and dis-assembled thereby facilitating the replacement or repair of parts during use of the associated equipment.

Claims (11)

1. A high density electrical connector, comprising: a first electrically insulating substrate; a first plurality of elongated essentially parallel electrical conductors afixed to said first substrate; a second electrically insulating substrate; a second plurality of elongated, essentially parallel electrical conductors afixed to said second substrate; interdigitating means located on at least one of said substrates and positioned to fit in the spaces between said conductors on the other of said substances for causing preselected ones of said first plurality to establish electrical contact with preselected ones of said second plurality of conductors when said first and second substrates are pressed into contact.

2. A connector according to Claim 1, wherein said first substrate is a flexible plastic film and said second substrate is rigid.

3. A connector according to Claim 1,wherein said first and second substrates are flexible plastic films.

4. A connector according to Claim 1, wherein said interdigitating means comprises a plurality of electrically insulating elements positioned to fit between said conductors.

5. A connector according to Claim 4, wherein said insulating elements are elongated and essentially parallel.

6. A connector according to Claim 5, wherein said interdigitating elements are located on said first substrate and are axially spaced from said first plurality of conductors.

7. A connector according to Claim 5, wherein said interdigitating elements are located on said first substrate and extend axially beyond the ends of said first plurality of conductors.

8. A connector according to Claim 1, wherein said interdigitating elements comprise a plurality of electrically conductive elements positioned on said first substrate spaced from and in axial alignment with said first plurality of conductors; and a fourth plurality of electrically conductive elements positioned on said second substrate between but axially spaced from said second plurality of conductors.

9. A connector according to Claim 1, wherein said first and second pluralities of electrical conductors comprise metal tracks deposited on said substrates, said metal tracks having a height of up to 0.00762 cm and said interdigitating means comprise ceramic tracks deposited on at least one of said substrates, said ceramic tracks having a height of up to 0.01524 cm, said metal and ceramic tracks being spaced at a pitch of at least 40 per cm.

10. Aconnector according to Claim l,further comprising means for maintaining said electrical contact.

11. The invention substantially as shown and described in the foregoing specification and claims.