JP2000218795A - Method for electrical interconnection and charge plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for high-density electrical interconnection between a driver chip and charging electrodes controlled by the chip. SOLUTION: The method for establishing a high-density electrical interconnection between high-voltage driver chips and charging electrodes controlled by the chips is provided. The charge plate has a charging electrode density on its face, and an associated mating circuit. Alignment structure is then provided on the charge plate and/or the mating circuit. The alignment structure of the charge late and the mating circuit are mechanically engaged to ensure alignment of a mating contact pads. An interconnect is provided for the aligned mating contact pads.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to continuous ink jet printers and, more particularly, to a small, high density electrical interconnect method for ink jet print heads.

[0002]

2. Description of the Related Art In continuous ink jet printing, ink is supplied to a manifold under pressure. The orifices are arranged in a linear array along the manifold. The conductive ink is ejected from the orifice as a filament. These filaments form a stream of ink droplets. At the point where the droplet stream breaks free from the filament, the selected droplet is charged. In order to properly charge the ink droplets, the breaking of the droplets must take place in front of the charge electrode. These charged droplets are deflected from their regular trajectories. The deflected droplets are captured or aspirated on the conductive surface and recycled. Uncharged droplets travel to the print media path.

[0003] Conventional methods of charging and deflecting liquids rely on what is known as planar charging technology. The method involves a series of electrically grounded inkjet formed droplets at a controlled distance from the orifice plate. Parallel rows of charge electrodes are aligned with the inkjet. Each charge electrode must be individually connected to a separate output lead from the high voltage charge driver chip that controls the charge electrode. A Different Way to Provide Compact Electrical Interconnection Between High-Voltage Driver Chips and Associated Charge Electrodes Made by Scitex Digital Printing Inc. in Dayton, Ohio It has been used in certain state of the art printheads. In each case, the density at which the interconnects can be made determines the physical dimensions of the printhead. As the printhead width and print density (dpi) increase, the number of interconnects increases proportionately. Since a small "footprint" (ie, small outer dimensions) is always required for the printhead, the interconnect density has been kept as small as possible.

In some conventional printers, one
Charge electrodes having a 20 electrode pitch per inch (about 25.4 mm) were fanned out to provide 100 leads per inch for connection to flexible circuits. In flexible circuits, the spacing of the leads can be further increased to make the connection a commercially available connection. Even with fanned spacing of 100 connections per inch in flexible cables, it has been difficult to reliably interconnect. It is difficult to further reduce the interconnect density. Necessary techniques such as soldering, anisotropic adhesives, flexible circuit and printed circuit board manufacturing have already reached their limits.

For a charge plate as shown in US Pat. No. 4,560,991, the width of the charge plate is 2.4 times the width of the ink jet row to achieve the required interconnection. Also need to be wide. This excess width is not suitable for long rows of printheads. U.S. Pat. No. 5,475,409 shows a more compact interconnect. Connections are made between the charge plate and several flexible cables. The contacts for each flexible cable are arranged as a straight row, which row is oriented perpendicular to the jet row. This shape fills the required depth of the charge plate, but greatly reduces the width requirements. However, the leads still need to be shifted to provide room for each straight row of contacts. For this prior art, the required shift is about 0.125 inch (about 3.18 m) for each of 64 connecting straight rows.
m). Therefore, for a row of about 4 inches at 240 jets per inch, the configuration requires a charge plate width of about 5.5 inches. This is a charge plate width that is 35% or more wider than the jet train. For longer rows, this shape becomes unacceptable. The problem is exacerbated for printheads with more jets per inch.

In another conventional configuration, the leads from the charge electrodes were fanned out for direct wire bond connections to the charge driver dice. This could reduce the size of the printhead by greatly eliminating the need to fan the interconnect. However, this technique has proven to be expensive. When the charge driver electronics are mounted directly on the charge plate, if one of the components fails, both the charge plate and the driver electronics must be discarded as scrap. For longer rows with a large number of charge driver electronics, the scrap cost would be too high.

It can be seen that the need for longer inkjet arrays at higher print densities, and at the same time, the need to minimize the overall size of the printhead, requires an improved charge plate configuration. The preferred charge plate configuration allows for the formation of reliable interconnects, and preferably allows the use of devices that can cure the device in case of failure.

[0008]

SUMMARY OF THE INVENTION Problems associated with conventional interconnect devices are overcome by the arrangement according to the invention, in which a fan-shaped lead is proposed, which has a charge plate. It has areas with furnace race density higher than the charge electrode density on the surface and terminates in two-dimensional rows of contact pads per connector at intervals common in the electronics industry. Charge plate and corresponding (suitable)
By having more common electrical interconnect pitch and matching features in the flexible cable, the two elements are self (self) aligned. Clamping means for attachment to the charge plate maintain the alignment of the elements and provide the necessary pressure to ensure electrical contact.

In accordance with one aspect of the present invention, there is provided an apparatus and method for establishing a high density electrical interconnect between a high voltage driver chip and a charge electrode controlled by the driver chip. A charge plate with charge electrodes on its surface is connected to a row of contact pads. Then, a matching structure is provided on the charge plate and / or the corresponding circuit. The matching structure of the charge plate and the corresponding circuit mechanically engages to ensure the matching of the corresponding contact pads. Also, interconnects for matched corresponding contact pads are provided.

The present invention establishes a high-density electrical interconnect between a high voltage driver chip and a charge electrode controlled by the driver chip for a continuous ink jet printhead.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the above-mentioned U.S. Pat. No. 4,560,991 or U.S. Pat.
Charge plates made by the process disclosed in US Pat. No. 2,117 require that the lead wire structure be formed by an electroforming process. This electroforming process produces an excessive number of rejects when the line width or spacing is less than about 2 mils each. Defective products cause the opening of the conductive leads or the shorting of the leads.

[0012] Advances in the manufacture of charge plate circuits as described in commonly-owned U.S. Patent Application Serial No. U.S. Patent Application Ser. To Recent advances have allowed line widths and spacing to be reduced to about 1 mil. 1
Even when increasing the density of the jet train to 300 jets per inch (3.3 mil pitch), this new process allows for a higher lead density than the charge electrode density. By further increasing the lead wire density,
The space for the row of connection pads can be released without requiring extra width.

Referring now to the drawings, FIG. 1 is an enlarged view showing a portion of a charge plate pattern 10 fanned out, showing two rows 14, 16 to associated connector pads 18.
In particular, a method of fanning out the lead wire 12 to the contact point of FIG. The diagonal trace 20 shown at the bottom of FIG. 1 is the density of the charge electrode. The bends 22 in the pattern 10 for forming the vertical sections 24 reduce line width and spacing. This reduction in the width of the group of leads is due to the contact pad 1
8 and provide sufficient space for the clearance area around each pad. Thus, according to the shape of the present invention, the width required for fan-shaped expansion of a group of leads reaching a single row of contacts is equal to the width of the leads on the charge electrode surface.

Since no extra width is required for a row of contact pads when constructed in accordance with the present invention, multiple rows of contacts can be used. Furthermore, because the space required to fan out the leads to the row of contacts is very small, the present invention increases the spacing between the contacts without requiring excessive depth of the charge plate (front-back distance). be able to.

At the 25 mil contact spacing that is common in the electronics industry, optical alignment of the contact pads of the charge plate with the corresponding flexible cables is no longer necessary. Rather, the matching structures of the present invention can be formed in each device to ensure alignment.

One preferred embodiment utilizes a small matching hole in the charge plate and flexible cable. The clamp bar (not shown) has two alignment pins. These pins engage the alignment holes on both the charge plate and the flexible cable to maintain alignment of the two elements. A set of alignment structures can be used to align multiple rows of contacts. By way of example only, the preferred embodiment uses a set of alignment structures to align 20 rows (of contacts), each row having 27 contacts.

Referring now to FIG. 2, an alignment hole 32 for the charge plate is machined into the base 28 prior to laminating the electroformed charge plate coupon to the ceramic charge plate base 28. You. In addition to such alignment holes 32 in the charge plate, through holes 30 for receiving clamping screws are machined in ceramic. An additional alignment structure 26 is provided on the coupon and base to ensure proper alignment of the charge plate lead pattern with the machined alignment holes 30 in the charge plate base. As in a flexible circuit, the charge electrode leads are formed by photolithography, thus ensuring the exact position of the leads with respect to the alignment holes of the electroformed coupon.

When the contact pads of the charge plate and the corresponding circuits are matched by matching structures on both of these elements, various processes can be used to make the electrical connection. These processes include processes such as applying a solder paste or epoxy to the charge plate using a copying or screen printing process, or utilizing a conductive epoxy. Anisotropic conductive film adhesives can also be used. Of course, each of the foregoing processes is essentially a somewhat permanent connection method and does not allow the separation of the charge plate and flexible cable without damaging one or both of the components.

In addition to these processes, there are various processes that utilize pressure to hold the elements together to obtain electrical contact. These processes are more desirable in the art. This is because these processes do not damage either the charge plate or the corresponding circuits, and allow for more efficient retrofitting and reuse of the device. These pressure-related processes include the use of elevated contacts and / or anisotropic conductive elastomers.

By raising the contact pads above the surface of the substrate for interconnection, the clamping force is concentrated on the contacts and helps to ensure electrical contact. Elevated contacts for the interconnect pad area can be located on a flexible cable or charge plate. The process of forming the ridges on the charge plate interconnect pads is described in commonly-assigned U.S. Patent Application Ser. Elevated contacts on flexible cables and methods of making the same are well known in the art. But,
Some of these methods require 100 contacts per contact.
Requires large clamping forces, such as gram forces, which is undesirable. This is because mechanical stress or deformation may occur in the elements of the trap. Other configurations of raised ridges require smaller contact forces in the range of 25-40 grams force for each contact. This minimizes deformation of the elements of the trap. Therefore, care must be taken with the selection and design of the pressure-based interconnects to keep contact forces to a minimum, as excessive contact forces can deform the trap and charge plate.

The metal plate is compressed (pressed) against a formed elastomer pad that contacts a flexible circuit including the raised interconnect pads to provide and distribute the required pressure on the raised contact pads. ). The elastomeric pad includes a separate protrusion that concentrates pressure at the interconnect pad location on the flexible circuit. This plate and the elastomeric pad can be combined into a configuration known as an elastomeric clamping mechanism. The clamp mechanism is compressed against the flexible circuit by the screw. Upon connection of the charge plate, these screws pass through the through holes 30 in the charge plate and are screwed into the trap below the charge plate. In this connection, the trap is such that the contact area remains planar,
Acts as a mechanical stiffener to ensure that all contacts receive the same amount of pressure. Connections for the charge driver board include screws that pass through clearance holes in the printed circuit board and are threaded into an external board known as the opposite stiffener.

Alternatively, the pressure connection can utilize an anisotropic conductive elastomer to provide an electrical connection. This elastomer is disposed between the charge plate and the corresponding circuit (flexible circuit). A conductive filler in the material provides electrical contact between the charge plate and corresponding circuitry while maintaining isolation between adjacent electrodes on the charge plate. Since the anisotropic conductive elastomer has flexibility, the clamping mechanism does not require an elastomer pad to distribute the clamping force.

Although a single set of connections having compression pads has been described, each maintains a two-dimensional array of contacts, alignment means for aligning the contacts, and electrical connections without departing from the spirit of the invention. It should be understood that a number of connectors with means for causing them to be used can be used. But,
The preferred embodiment of the present invention uses five connectors, each with 540 electrical contacts.

Although the present invention has been described in detail with particular reference to certain preferred embodiments, it should be understood that various modifications and changes can be made within the spirit of the invention.

[Brief description of the drawings]

FIG. 1 is an enlarged view showing a part of a fan-shaped pattern of a charge plate according to the present invention.

FIG. 2 illustrates a matching configuration for the interconnect device of FIG. 1 according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Charge board fan-shaped expansion pattern 12 Lead wire 14, 16 Contact row 18 Contact pad 20 Trace 28 Charge board base

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Bruce A Bowling Lunchfield Drive, Beaver Creek, 45432, Ohio, USA 3128

Claims (10)

[Claims] 1. A method for establishing a high density electrical interconnect between a high voltage driver chip and a charge electrode controlled by the driver chip for a continuous ink jet printhead, comprising: Providing a charge plate having: at least one termination at a contact pad.
Providing at least one corresponding circuit for establishing a connection to the three high voltage drivers; providing a matching structure on the charge plate and associated circuit; and matching the corresponding contact pads. Mechanically engaging the matching structure of the charge plate and associated circuitry to assure; providing interconnects for aligned corresponding contact pads; A method characterized by the following. 2. The method of claim 1, further comprising the step of providing a lead fan flared shape having a region of trace density higher than the charge electrode density. 3. A method for establishing a high-density electrical interconnect between a high-voltage driver chip and a charge electrode controlled by the driver chip for a continuous ink-jet printhead, comprising: Providing a charge driver circuit board having a circuit connected and terminating at a contact pad; establishing a connection to at least a portion of the charge electrode and providing at least one corresponding circuit terminating at a contact pad. Providing a matching structure on the charge driver circuit board and the corresponding circuit associated therewith; and providing the charge board and the corresponding circuit associated therewith to ensure alignment of the corresponding contact pads. Mechanically engaging the alignment structure;
Providing interconnects for matched corresponding contact pads. 4. The method of claim 3, wherein providing the at least one corresponding circuit comprises using a pressure-based connector. 5. The method of claim 4, wherein using the pressure-based connector comprises using raised ridges on the charge plate or on the associated circuit. the method of. 6. The method of claim 1 wherein said step of using a pressure-based connector comprises the step of sandwiching an anisotropic conductive elastomeric material between said charge plate and a corresponding circuit associated therewith. The method according to claim 4. 7. The method of claim 4, wherein using a pressure based connector comprises using a reusable pressure based connector. 8. The method of claim 3, wherein providing at least one corresponding circuit comprises using raised contacts. 9. A means for minimizing the need to fan out a footprint for connection to high voltage drive electronics in a charge plate for an ink jet printer having a high density of charge electrodes along a charge surface. Means for preparing a fan sector expanded shape having a trace density higher than the charge electrode density. 10. The charge plate according to claim 9, wherein the fan-shaped fan-shaped expanded shape terminates in a two-dimensional row of contact pads for each connector.