JPH0573235B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD This invention relates generally to printed circuits, and more particularly to flexible interconnects between parts of a display system, such as between matrix display elements and drive electronics.・Regarding ribbons and cables.

BACKGROUND OF THE INVENTION Conventional electronic device packaging technology has typically involved mounting active and passive electronic components on single or multilayer printed wiring boards (PWBs). Multiple such printed wiring boards are
Plug multiple boards into the “mother” connection panel
Connected by connecting. If space is insufficient, a flat panel can be used instead of a connection panel to interconnect the end connections of the display element to the end connections of the display drive electronics printed wiring board. - In matrix display systems, flexible ribbon cables are run straight. There are typically 500 to 6000 electrical connections between the display element and the drive electronics, resulting in substantial space requirements for the drive electronics, increased assembly costs, and ) The extent of maintenance is also limited. Connections between drive electronics and display elements
When it becomes necessary to remove the display for testing in the field or for inexpensive replacement of a failed device,
The assembly must be returned to the service center for reassembly. As a result, the display
Element and drive electronics are
It is kept in reserve as a single line replaceable unit (LRU) in the field, but it is expensive. If the components of the display system are designed to be easily removable, repair of the drive electronics can be done in the field by simply keeping relatively inexpensive spare parts or devices.

High voltage driver circuits occupy the majority of the volume required for drive electronics in matrix display systems. Packaging high voltage driver circuits into leadless chip carrier (LCC) structures
The volume of the display system can be reduced considerably. However, LCC mounted on the surface
and Dual Inline Package (DIP)
A problem arises when well-known through-board integrated circuit (IC) devices such as 1-2 are mounted on the same printed wiring board because they require two incompatible assembly techniques. And this method itself does not appreciably reduce the number of interconnections required between the display drive electronics and the display elements.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the volume of a display system while allowing parts of the display system to be easily removed for repair.

In accordance with the present invention, a flexible cable assembly is provided having a flexible insulating substrate on which a plurality of conductors are formed. A predetermined group of solder pads are electrically connected to the conductor and the solder pads are
A circuit package cage is attached to the pad. A pin inserted into one end of the flexible cable assembly provides a means of connection to the printed wiring board, and an exposed conductor with a conductive plating on the first side of the second end of the flexible cable assembly is connected to the second end of the flexible cable assembly. Provides a means for clamping to a conductor that has a . A heat sink/backing is laminated to the bottom area of the circuit package and board. A plurality of flexible cable assemblies interconnect the drive electronics module to the matrix display element within the display assembly. The circuit package consists of a high voltage driver circuit mounted within a leadless chip carrier (LCC), reducing the volume required for the drive electronics. Furthermore,
The circuit package attached to the flexible cable provides a means to reduce the number of connections required between the drive electronics and each flexible cable assembly. The flexible cable assembly provides an easily repairable display assembly in the field.

According to another aspect of the invention, a method of manufacturing a flexible cable assembly is provided, the method comprising a flexible cable having a plurality of strip conductors arranged in one or more layers formed therein. providing a flexible insulation means on each side of the plurality of conductor layers, the flexible cable having a group of solder pads arranged on a portion of the first side of the first end region thereof; a portion of the solder pad is coupled to a first portion of the strip conductor, and a second uninsulated portion of the strip conductor on a second side of a second end of the flexible cable assembly is bonded to a conductive plating. soldering a circuit device to solder pads arranged on the first side of the flexible cable; and a second side of the flexible cable below the flexible cable and the circuit device. laminating a heat sink/backing means to a portion of the flexible cable; and soldering terminal pin means on a first end of the flexible cable proximate to the circuit device, the pin means being connected to the strip conductor and the solder pad. and a step coupled to a part of the .

[Explanation of Examples] The present invention will be described in detail below with reference to Examples.

Referring to FIGS. 1, 2, and 7, a flexible cable assembly 10
is shown, and this assembly includes a flexible cable 11 in which layers of insulated strip conductors 24 and 32 are formed;
A leadless chip carrier 12 attached to one end of the cable 11, a heat sink/backing 14 attached to the flexible cable 11 below the area covered by the leadless chip carrier 12, and a display assembly 50.
a connecting device having pins 15 and strip conductor end connectors 16 at both ends of the flexible cable 11 for connecting between the sections of the flexible cable 11. Leadless chip carrier 12 provides a means for interconnecting one or more circuit chips or other devices within the carrier. Pin 15 is flexible cable assembly 10
to provide a means for electrically connecting one end of the board to a printed wiring board. Connector 16 at the other end of flexible cable assembly 10 is defined by the 1/4 inch (6.35 mm) end of strip conductor layer 32. The end connector 16 has no insulating material coating and has a conductive plating that allows it to connect to the code conductor on the display element 58 of the display assembly 50 as shown in FIG. Allows the ends of assembly 10 to be clamped. The flexible cable assembly 10 connects a portion of the drive electronics module 54 within the display assembly 50 to the display element 5.
used to interconnect parts of 8. pin 1
5 is drive electronics module 5
4, the end connector 16 is wrapped around the end of the display element 58, and its exposed strip conductor connections are aligned with matching connections on the bottom of the display element 58 (not shown). are combined. Clamp 62 connects end connector 16 to display element 58.
Fix it to the matching connection part on the top. The side view of flexible cable assembly 10 in FIG. 2 shows heat sink/backing 14 and pins 15 for connection to a printed wiring board.

3 and 4, an exploded perspective view (FIG. 3) of flexible cable assembly 10 is shown, with flexible cable 11 comprised of multiple layers of material. It should be noted that the vertical dimensions in FIG. 3 are not exact and the thickness of each layer of material is exaggerated. FIG. 4 clearly shows the layers of material used to form the flexible cable 11, which consists of two conductive layers. The base material of the flexible cable 11 forming the insulating layers 20, 28, 36 is:
Compressed (condensed) polyimide, EIduPont de
Nemours & Co. Inc. (Fairfield, CTO6433)
Kapton® polyimide manufactured by Kapton® can be used. Kapton polyimide was used because of its flexibility, high tensile strength, and excellent insulation properties when formed into 1-2 mil (0.025-0.051 mm) thick sheets. Conductors 24 and 32 are approximately 1 or 2 ounces (1.4 or 2.8
The copper foil is stretched and annealed, thereby providing relatively soft copper. Layers 22, 26, 30, 34 are coated with an acrylic adhesive, such as EIduPont de Nemours Co.
Paralux (trademark) manufactured by Inc. can be used,
Kapton insulating layers 20, 28, 36 and copper conductor layer 24,
Glue 32 together. The acrylic adhesive is used in 1 and 2 mil thicknesses. Leadless chip carrier 12, well known to those skilled in the field of microelectronics, has leadless terminals 23 disposed around its periphery and soldered to corresponding pads 25 arranged in alignment on flexible cable 11. be done. The opening 27 is
Avoid insulating the tops of solder pads 25 formed in Kapton layer 20 and projecting through mating openings 27 thereof to allow pins 15 to be inserted into flexible cable 11 and soldered. The heat sink/backing 14 may be made of epoxy glass, such as G10, which is well known to those skilled in the art, or other thermally conductive materials, such as alumina or certain
Depending on the cooling needs of the LCC, copper, amber,
It is made of a material with a matched coefficient of expansion, such as a copper laminate. Heat sink/lining 14 is the first
As shown in FIGS. 3 and 3, it can be made large enough to cover the area below the LCC 12, or it can be made large enough to cover the area around the connection pin 15. The heat sink is attached to the flexible cable 11 by adhesive. Heat sink/backing 14 ensures that input connector pins 15 remain aligned and LCC 12
the flexible cable 11 to ensure that the flexible cable 11 is in proper contact with its heat sink and that the flexible cable 11 is held in the area of the LCC 12 to prevent fatigue of the solder connections of the LCC 12.
A means of restraining the assembly 10 is provided. pin 15
are the nine plated through holes 29 in the first end of the flexible cable assembly 10.
The pins 15 provide connection means for attaching the first end of cable assembly 10 to a printed circuit board. The second end of flexible cable assembly 10, consisting of connector 16, is formed as shown in FIG. Approximately 1/4 inch (6.35 mm) of the bottom ends of the plurality of copper strip conductors of layer 32 are not insulated as described above and are gold plated, thereby allowing the conductors to be used as end connectors 16. , as shown in Figure 7.
This end of assembly 10 is clamped to a matching conductor on display element 58 by U-shaped clamp 62.

The method of manufacturing flexible cable 11 is similar to the method of manufacturing single-sided, double-sided, and multilayer printed wiring boards well known to those skilled in the art. The reason is that both methods involve copper being etched onto the insulating material. Printed wiring boards are commonly used to interconnect components, while flexible cables are commonly used to connect printed wiring boards to other printed wiring boards or other active devices. They are similar and most of the steps are the same although some of the materials are different. The method for assembling flexible cable 11 consists of the following steps.

1 Select materials, thickness and assembly method: insulating material (Kapton), adhesive (Paralux), conductor (soft copper).

2 Drill the craft holes (punch or drill): The holes match the artwork and drill tape and cover sheet thin layer for front and back alignment.

3. Drilling a through hole: Pay particular attention to the feed and speed of the drill as burrs will form in the annealed copper.

4. Remove excess adhesive: The application generates heat as the drill penetrates the copper, melting the acrylic and
This is done by applying acrylic to the copper during the drilling process.

5. Electroless and electroplating of copper on plated through holes: Used only when plated through holes are on the circuit and is the same process used for printed wiring boards.

6 Draw the conductor pattern: The flexible cable is now plated with through holes and
Copper is provided on both sides. The artwork is then coated with dry film photoresist, aligned, exposed and developed to create a positive image of the desired circuit, and the through holes are coated with photoresist for protection during further processing. covered.

7. Etching the conductor pattern: This is a typical process similar to the assembly of printed wiring boards. Chemically etch away the excess copper, leaving the desired circuit.

8. Cleaning: Cleaning is an important step in the successful manufacture of printed wiring boards, multilayer boards (MLB), or flexible cables. Providing one or several cleaning steps before each treatment allows subsequent treatments to be carried out without interference from undesired dust, oxides or residues.

9 Covering Coatings: To protect copper conductors from damage during handling and electrical short circuits, a coating is required over the conductors. The same substrate is used for the coating to maintain flexibility.
Thin using appropriate amount of acrylic glue
A Kapton layer is laminated onto the conductor. In this case, the adhesive is pre-drilled (drilled or punched) to expose the pad for soldering.

10 Laminate the heat sink/backing: Attach the heat sink/backing to the flexible cable using acrylic adhesive.

11 Solder coating: The flexible cable is solder coated after the sheath coating is laminated, since no soldering is required except for the pads. This process involves immersing it in molten solder, blowing it with hot air or hot oil to remove excess solder, or wiping it with a roller to remove excess solder.

12 Determining the geometry: Routing using templates and carbide tools can be expensive, commonly used for printed wiring boards and multilayer boards. However, flexible cables can be cut very effectively using inexpensive steel rule dies, and in small quantities, can also be cut with a knife.

3, 5 and 6, the top and bottom layers 24 and 32 of the copper conductor of the flexible cable 11 on the Kapton insulation layer 28 after the etching step of the assembly method are shown. A typical layout is shown. FIG. 5 shows the circular dots to be plated through holes 29, 31 and the copper pad arrangement 25 for attaching the leadless chip carrier 12 to the flexible cable 11.

Referring again to FIGS. 1, 2 and 3, the steps by which flexible cable 11 completes assembly of flexible cable assembly 10 will now be described.

1 First inspection: The flexible cable 11 is inspected to see if it conforms to the specifications.

2. Solder Paste Application: Solder paste is screen printed onto the solder pads 25 using conventional screening equipment.

3 LCC arrangement: leadless chip carrier 12 with pre-tinned pads 23
are placed in a suitable manner on the solder pads 25 arranged on the flexible cable 11.

4 Second inspection: Connecting to flexible cable 11
The placement of the LCC 12 is inspected to ensure that the pre-tinned pads 23 on the LCC 12 are properly aligned with the solder pads 25 on the flexible cable 11.

5 Steam state (vaporization) soldering: The flexible cable 11 with the LCC 12 attached is subjected to vapor phase reflow soldering.

6 Third inspection: Soldered assembly 10
are checked for proper solder joints (contours).

7 Cleaning: Cleaning removes solder flux and other contamination.

8 Connector pin installation: Terminal pin 15 is 9
It is inserted into each of the plated through holes 29 and soldered at the appropriate positions.

9. Cleaning: Cleaning is performed to remove flux residue from previous soldering.

10 Final Inspection: A final inspection of the flexible cable assembly shall be performed to ensure proper workmanship and compliance with assembly procedures.

Referring now to FIG. 7, there is shown a flexible cable assembly 10 connecting two portions of a flat panel matrix display assembly 50 shown in an exploded perspective view. A first end of the flexible cable assembly 10 having pins 15 proximate the leadless chip carrier 12 is inserted into the drive electronics module 54 and a flexible cable assembly 10 having an exposed strip conductor on one end of the flexible cable 11 is inserted into the drive electronics module 54 . - The second end 16 of the cable assembly 10 is a flat glass panel.
wrapped around the ends of the matrix display element 58, then the end connectors 16
The exposed conductors of display element 58
Align with the matching conductor on the edge of the bottom surface (not shown). The end connector 16 is connected to the display/
It is secured to element 58 by a U-shaped clamp 62. A plurality of flexible cable assemblies 10 are used around the drive module 54 and display element 58 of the flat panel matrix display assembly 50 to provide all necessary interconnections.
matrix display assembly 50
Also includes a controller module 52 that controls signals to the drive module 54 and thus the display element 58, a reinforced panel 56 and a frame/bezel 60 to protect and support the integrity of the display element 58. have The display element 58 is
Electro-Plasma Inc. (EPI) (Milbury, Ohio)
This can be implemented with a flat panel plasma display element, part no. PDM256512-062, manufactured by All input signals from driver module 54 to LCC 12 on flexible cable assembly 10 pass through connections formed by pins 15.
The output signal from LCC 12 to display element 58 is routed through a flexible cable end having an exposed or uninsulated strip conductor that is aligned and properly clamped with the code conductor on the peripheral edge of display element 58. Passes through connector 16. The number of connector pins 15 required for the connection between flexible cable assembly 10 and drive module 54 is greater than the number that would be required if no active LCC 12 was located on cable assembly 10. Very few. Only a small number of pins are required to handle the control drive signal input to flexible cable assembly 10, and a large group of decoded output signals from LCC 12 is formed from strip conductor layers 24, 32 and layer 32. is handled by a non-insulated end connector 16. Matrix display assembly 5
The use of flexible cable assembly 10 in 0 not only reduces the number of direct electrical connections required between drive module 54 and display element 58 but also greatly reduces the overall volume of matrix display assembly 50. decrease to Furthermore, the maintainability of the matrix display assembly 50 is improved by the driver module 54, the display
This is improved by allowing element 58 and flexible cable assembly 10 to be disassembled and reassembled at the installation site. In-field repairs of driver module 58 and flexible cable assembly 10 can then be easily performed by replacing failed circuit components with relatively inexpensive spare circuit components or devices.

Although preferred embodiments of the present invention have been described above, it will be apparent to those skilled in the art that many modifications and changes can be made within the scope of the invention. For example, a flexible cable can have one conductor layer or multiple conductor layers, and the material of the conductor layer may be copper, gold, silver, aluminum or other materials, as well as the plating on the connection end to the matrix display. Similar electrically conductive materials or compound materials can be used. The surface area of the heat sink can be small or large depending on the application, and the type of connection means at each end of the flexible cable assembly can also vary depending on the application.

[Brief explanation of the drawing]

FIG. 1 is a top view of a flexible cable assembly according to the invention having two conductor layers.
FIG. 2 is a side view of the flexible cable assembly, with the leadless chip carrier mounted on the first end of the cable assembly in line with the insertion pin, and the flexible cable and the leadless chip carrier laminated just below the leadless chip carrier. The heat sink/backing is shown. FIG. 3 is an exploded perspective view of a flexible cable assembly according to the present invention. Figure 4 shows the flexible structure shown in Figure 3.
The material layers of the cable are shown. FIG. 5 shows the layout of the top layer of copper strip conductors according to the present invention. FIG. 6 shows the layout of the bottom layer of copper strip conductors according to the present invention. FIG. 7 is an exploded perspective view of the matrix display assembly showing the flexible cable assembly interconnecting between the drive electronics and the matrix display element. (Description of symbols) 10...Flexible cable assembly, 11...Flexible cable, 12
...Leadless chip carrier, 14...Heat sink, 15...Pin, 16...Connector.

Claims (1)

[Claims] 1. A display assembly comprising: display element means for displaying a plurality of characters; a plurality of chip carrier means having a driver circuit for selecting one or more of the plurality of characters; a plurality of flexible cables having insulated strip conductors formed therein and easily connectable and disconnectable within the display assembly; and a plurality of flexible cables disposed on a portion of the first side of each of the flexible cables. , pre-installed solder pad means for attaching one of said plurality of chip carrier means, a portion of which is coupled to a portion of said strip conductor; and said flexible cable. means disposed below the chip carrier means and attached to the flexible cable at a portion of a second side of each of the chip carrier means, the means having a coefficient of expansion substantially matching the coefficient of expansion of the chip carrier; - supporting each of said flexible cables by constraining the cables to accommodate expansion of said chip carrier means;
restraining means for restraining a cable to prevent fatigue in the solder pad means of the chip carrier means and removing heat from the chip carrier means; the flexible conductor coupled to a portion of the conductor and having the first end attached to the interior of the display assembly and the second end attached to the display element;
a display assembly comprising: an attachment means for facilitating separation for repair of each of the cables; 2. The display assembly of claim 1, wherein said display element comprises a matrix display element. 3. The conductor of the flexible cable comprises a first layer and a second layer, and flexible insulating layer means is provided on each side of the first layer and the second layer, and between the conductor layer and each flexible insulating layer, A display assembly as claimed in claim 1, wherein adhesive layer means are provided. 4. The display assembly of claim 3, wherein said flexible insulation means comprises condensed polyimide. 5. A first end of each of the flexible cables proximate the chip carrier comprises a plurality of pins connecting the first ends in a manner that facilitates separation for repair within the display assembly; a second end of each flexible cable comprising an uninsulated conductive plated portion of said strip conductor, said uninsulated conductor being joined to said display element conductor by clamping means to facilitate separation for repair; A display assembly as claimed in claim 1. 6. The display assembly of claim 1, wherein said restraining means comprises a laminate backing means to reduce heat-related forces experienced at a surface of the backing means.