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ZEBRA® connectors are composed of alternating layers of conductive and non-conductive silicone rubber. Contact density of the ZEBRA® connector is greater than the contact pad density of either the LCD or PC board, making it an ideal design choice. When placed between the LCD and PC board at least one conductive layer will connect matched contact pads and at least one insulating layer will isolate adjacent circuits.
Micro-electronics interconnect packaging applications by their very nature leave a minimum of space in which to assemble mating components. High reliability and very small interconnections, with an everincreasing number of I/O’s, are a must if design objectives are to be met. ZEBRA® connectors can be found in most product types of this nature, and continue to gain wider acceptance as product packages decrease in size. Since each style consists of integral conductors, insulators and selfsupport structures, there is generally no added componentry required for installation – thus a very important by-product of hardware and installation cost-effectiveness can be realized.
AS EASY AS 1...2...3: Using ZEBRA® elastomeric electronic connectors
requires only a brief orientation in order to assure that the components
provide the finest performance possible. The basic design steps consist
1. Layout of your package
2. Select the proper connector and size
3. Design the bezel or retainer
Pressure type contact eliminates lead straightening, hole drilling and soldering. NON-ABRASIVE CONTACTS (Zero insertion force) Contact to the LCD is made by deflecting the ZEBRA® connector between the LCD and PC board. ZEBRA® connectors are non-abrasive and will not damage indium oxide contact pads on the LCD. Repeated assembly and disassembly of package components will not affect performance.
The LCD, when mounted with a ZEBRA® rubber connector, creates a gas tight seal at the contact interface. Assures contact in chemically corrosive atmospheres while at the same time protecting the glass display from shock and vibrations.
With a ZEBRA® connector, LCD terminal overhangs can be as narrow as 8mm permitting more efficient use of glass size related to character height. (Metal pins normally require a 3.9mm glass overhang, reducing character height by as much as 6.1mm for a dual in-line LCD.)
ZEBRA® connectors are available in a variety of contact densities. The most dense allows contact pad spacing as close as 0.25mm center-to-center. This spacing can be compared to 1.3mm minimum for pins, allowing for increased capacity of LCD formats.
-55? TO +260? F/-50? C TO +125? C (-60? TO +125? C available on request)
40 amps per square inch of contact pad. (0.050A for .035 x .035 pad)
Typically 500 to 2,500 ohms.
Typically 1012 ohms.
1.5 pounds per linear inch for a 0.020” wide ZEBRA®.
100,000 hours minimum.
up to 500 per inch.
F = 9 x D x W x L x 9.8x10-3
F = 10.0 x D x W x L x 9.8x10-3
Where: F = Force (N)
H1 = Deflected height of connector (mm)
|D =||H - H1|
W = Width of connector (mm)
L = Length of connector (mm)
H = Height of connector (mm)
|R =||60 x H||= ohms|
|Ew x W|
Ew = Electrode pad width (cm)
W = Connector width (cm)
H = Connector height (cm)
|R=||H x 0.01||+ 0.10||= ohms|
|W x EW|
W = Width of ZEBRA® (mm)
Ew = Electrode pad width (mm)
H = Height of ZEBRA® (mm)
The ZEBRA® connector will provide a gas tight seal. Adverse effects of temperature, shock and vibration, atmospheric corrosion as well as harsh chemical environments will not affect LCD or PC board contacts, when sealed through use of a ZEBRA® connector.
Shown at left is a typical LCD-to-printed circuit board interconnect using ZEBRA® elastomeric connectors in a cellular telephone handset. The components are stacked and consist of only three items to be addressed:
Liquid Crystal Display (LCD)
Printed Circuit Board (PCB)
It is essential that contact mating characteristics be kept as similar to the other components as possible. Any factors restricting positive contact interface should be compensated for in the design. Some of these are as follows:
a.)Registration of contact pads between the LCD and PC board is critical in effecting contact. Contact pads of both should
ideally be of the same size and equally matched in tolerances for width and pitch.
b.)Consider carefully PC board thickness and the related flatness tolerances. Proper design should involve the control of “waviness” tolerances and board stiffness. Both elements are essential in the appropriate design and selection of the ZEBRA® connector. Connector deflection and width are important considerations in determining the size of the ZEBRA® connector to be used in order to maintain proper deflection without “bowing” the PC board.
c.)Contact pad material on the PC board, as well as the LCD, should be smooth and regular with thickness tolerances established.
d.)Consider the area on the PC board to be dedicated to the LCD and the presence of neighboring components. Location of the LCD above or on the PC board should permit free clearance on all four sides of the PC board profile of at least 6.2mm for packaging and/or fastening.
a.)Select LCD configuration, e.g., Single In-Line (SIL); Dual In-Line (DIL); or contacts on both planes. Example: Dot Matrix.
b.)Select an LCD which in its design has contact pads on the reverse side of the viewing area facing PC board). For those instances where contact pads cannot be stationed facing the PC board, a custom elastomer may be required.
c.)Pitch of LCD contact pads.
d.)Length, width, and thickness of combined front glass and back glass of LCD.
e.)Determine lip width (distance from outside edge of front glass to edge of back glass). This dimension should be at least 1.5mm and preferably 2.5mm. Ideally, contact pads should extend to the outer edge of the lip on the glass.
Consideration must be given to tolerance control on the elements that comprise the connector package. There are separate flatness and parallelism tolerances for the LCD glass, polarizers, reflectors and PC board. Materials used for the contact pads of the LCD and contact pads of the PC board also have thickness variations which must be considered. Flatness of the PC board and parallelism between the components are also factors. These tolerance values are vital criteria in determining separation variations between the LCD and PC board. The sum of the tolerances of these elements plus nominal separation determine the height (H) of the connector which will meet your design application.
ZEBRA® elastomeric connectors offer a wide variety of application possibilities, in many cases where no other type of interconnect device is possible. They require a minimum of installation hardware considerations, allowing for very small packaging structures to support low profile display and microelectronic interfacing.
When properly dimensioned, long-life performance can be assured and gas-tight connections without additional precautions can be realized.
a.)Select a ZEBRA® connector that will assure that at least one conductive layer connects
between contact pads, for example, of an LCD and PC board to be interconnected, and at least
one insulating layer is between adjacent contact pads.
b.)ZEBRA® connectors can accommodate applications with contact spacing of .254 mm center-to-center or greater. c.) The overall length should extend a minimum of 0.020” beyond the edge of the contact at each end of the connector. a.) ZEBRA® connector height is determined by the separation distance between LCD and PC board contact pads, including tolerance variations. ZEBRA® connectors can be supplied with a height of up to 25mm.
b.) ZEBRA® connector height is the most critical dimension in determining the functional performance of the connected components. Calculate the tolerance stack-up of the PC board, LCD, polarizer, and ZEBRA®. Multiply the maximum separation distance by 1.10 (adding 10% to separation distance) to establish uncompressed ZEBRA® connector height.
c.) The following example shows calculations used in determining uncompressed ZEBRA® connector height.
Example: Separation distance in this application equals 5.08mm with tolerance of +/- 0.13mm representing the tolerance stack-up from one end of the LCD and PC board separation to the other end. The minimum separation in our application equals 4.9mm; the maximum separation equals 5.2mm. Multiply the maximum separation of 5.2mm by 1.10 to develop the uncompressed ZEBRA® connector height. The resulting 5.7mm uncompressed height of ZEBRA® connector is the correct ZEBRA® connector height to assure adequate contact and achieve the minimal 4.9mm separation for assembled height of the LCD, PC board package, and to insure contacts in areas where the minimum separation of 4.9mm prevails. To achieve the 5.08mm assembled height, it is necessary to deflect the 5.7mm free height ZEBRA® connector by 10%. The design result falls within the 5%-25% deflection range recommended for effective ZEBRA® connector contact.
a.)Force deflection considerations of the ZEBRA® connector (Refer to Force Deflection formula) result in a recommendation of 0.6mm as the width for connectors of lengths between 6mm and 63.5mm. Continuous connector spans of 66mm to 203mm require a minimum 0.9mm wide connector to allow easy assembly of the ZEBRA® connector into the slot of a holder. Ideally, the ZEBRA® connector length should be limited to 63.5mm due to possible insertion difficulties of the connector in the slot of the holder.
b.)ZEBRA® connectors with a width of 0.6mm to 0.9mm require the use of a holder. (See design of ZEBRA® connector holder.) Fujipoly offers standard self-supporting ZEBRA® connectors eliminating the need for fabricating a holder for heights up to 5.08mm.