Characteristics of conductive strips, design and application
Liquid crystal display devices in use are connected to the most critical, about liquid crystal displays and printed circuit board (PCB) and other components together. It is different with traditional welding methods, currently used in several ways:
◆ conductive adhesive connections
◆ Hot linking
◆ shaped conductive adhesive connection
1, conductive adhesive connection
This is the typical LCD connection, try the form at the ITO electrode for leads connecting the device. ITO transparent conductive film of the outer leads can not be welded, but you can use conductive glue and liquid crystal display devices connected to circuit board;
1. Common conductive adhesive
(1) the basic structure of ordinary conductive adhesive
A typical conductive adhesive is a thin layer of conductive adhesive (conductive layer of granulated carbon) and a thin layer of rubber insulation stacked together alternating layers by hot embossing, then cut made perpendicular to a thin level finished article. Is only used to introduce the company of several common conductive adhesive.
◆ general shape of conductive adhesive
(1) half of the conductivity, half of the insulation
(2) sandwich (central, eccentric)
(3) fully insulated
(1) conductive adhesive side due to a non-insulation layer, easily affected by external moisture and invasion, are not often used in display module, we often use it for measuring seat tests;
(2) conductive adhesive 2 has insulation layer, improved reliability, greater pressure can be supported, such commonly used in the display module, but it only applies to external lead electrode transparent conductive film down LCD display, that is, under the big small LCD;
(3) there is no conductive layer of conductive rubber, usually come with the booster.
◆ common conductive adhesive material
Conductive adhesives are commonly used materials in two ways:
a. Silica gel (SILICON)
The silicone material is more resilient, but as a solid body, white is transparent, hardness of about 25 ° ~ 35 °, the middle of the sandwich due to the carbon layer, the hardness of about 65 ° ~ 75 °.
b. Silicone Foam
SILICON foam material to foam as the raw material into the hollow post-like and more flexible, will not increase the overall conductivity of the hardness of rubber, but the hardness can not be tested, usually pink.
2. Set the size of conductive adhesives
The length of plastic (L)
Its length can not be shorter than the LCD, the ITO, usually shorter than the length of LCD 1 ~ 2mm.
The width of glue (W)
Its width, the lower the ITO glass or ITO length length-0.1mm.
Plastic height (H)
Its high compression ratio H = h *
● h = [H2 (iron box from a height above the PCB board) - Loading LCD thickness - the thickness of metal frame-TI (pressure-depth article)]
● compression settings:
According to the current design of my company's products, this set is for reference only.
● H2 height if the compression ratio is 2.0 ~ 6.9mm 1.12 ~ 1.2 set for my company's products are generally set for the compression ratio is 1.1;
● H2 is 7.0 ~ 10.5mm height if the compression ratio is set to 1.07 ~ 1.13, for my company's products are generally set for the compression ratio of 1.12.
● When using the foam TYPE, H value must be the middle of the sandwich than the use of SILICON TYPE higher than 0.1mm, when the use of all insulation TYPE, H value must be the middle of the sandwich than the use of SILICON TYPE to short 0.1mm. RUBBER due to compression ratio and the characteristics of the material and the glass has certain relations, it should be fully taken into account in the design.
Conductive layer of conductive adhesive spacing (pitch)
Select size pitch conductive adhesive can be considered the best path to each PCB Road to eat at least 3 carbon layer is the best situation, in general, conductive adhesive Pitch = PCB Panel Pitch / 6.
According to PCB Panel of the actual situation, we now commonly used are 0.18mm, 0.1mm, 0.05mm three, the smaller the value the more expensive price.
The width of the conductive layer of conductive adhesive (CW)
CW conductive layer is generally not more than 1.0mm, we now commonly used are 0.4mm, 0.6mm, 0.7mm, 0.8mm, 1.0mm.
◆ conductive layer of conductive adhesive and conductive strip width of the hardness directly related to the height relationship between the choice of conductive strips, the compression ratio should give special consideration to the width of the conductive layer.
(3) conductive rubber specifications (length * height * width) standard as follows:
Second, conductive paper (Heat Seal) soft link
Conductive paper (Heat Seal) is also a popular soft-link connection
Hot Articles appearance and structure:
Conductive paper substrate is a polyester film mode, the chip is a section of graphite conductive article, printed with conductive paper clearance Insulation adhesive. Use of paper when one end of conductive stripes aligned LCD conductive outer lead end of the paste, heat, pressure, and then pressing the other end of conductive strip circuit board conductive stripes aligned side drive leads, paste , heat, pressure, then the outer lead end LCD and circuit board-side drive leads to connected. As the conductive paper substrate is soft, so the use of different structural components and assembly requirements can be a very good adaptation, but also realize the thin installation.
Heat Seat advantage is soft and easier to fold than the FPC, and the price is cheaper than the FPC, the question is if there is no standard, then the mold more expensive, as chosen by the standards of the Heat Seat.
Standard Heat Seat size PITCH are:
◆ 0.4,0.5,0.6,0.8,1.0,1.5,1.6,2.0
3, shaped conductive adhesive
We often shaped conductive strip for the YF-type conductive tape, conductive tape that is outside the lead for mixed-designed LCD displays that both electrodes outside the lead up down there. In some high-density liquid crystal display sometimes appears on three sides-out, which side of the external lead electrode upward, not toward the circuit board, which YF-profiled using conductive tape. |
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