1. What is Ultrasonic plastic-welding?
Plastic welding is used for a huge variety of products ranging from blister packs, cartons and small consumer goods up to car fuel tanks and dashboards. It works by generating heat exactly where it is needed - at the interface between the components to be joined. The components are clamped between a vibrating sonotrode and a fixed mounting. Strangely, the vibrations are usually applied perpendicular to the contact surface, although much of this vibration may be converted to in-plane movement. This also has the advantage that the clamping pressure will keep the sonotrode in contact with the component - serrated surfaces are generally not required. Best results are achieved when the components are clamped close to the interface ("near-field" welding) but if this is not possible then the process can still work at a distance ("far-field"). Staking, or insertion, is a variation of this process in which a metal part (generally a threaded bush) is driven into a hole in a plastic component, which then solidifies around it to form a permanent join. This is a convenient method of producing strong tapped holes in a plastic part.
2. What is Chip-on-Board (COB)?
Chip-on-Board, or COB, refers to the semiconductor assembly technology wherein the microchip or die is directly mounted on and electrically interconnected to its final circuit board, instead of undergoing traditional assembly or packaging as an individual IC. The elimination of conventional device packaging from COB assemblies simplifies the over-all process of designing and manufacturing the final product, as well as improves its performance as a result of the shorter interconnection paths. The COB process consists of just three major steps: 1) die attach or die mount; 2) wirebonding; and 3) encapsulation of the die and A variant of COB assembly, the flip-chip on board (FCOB), does not require wirebonding since it employs a chip whose bond pads are bumped, which are the ones that connect directly to designated pads on the board. As such, FCOB's have their chips facing downward on the board (hence the name 'flipchip'). Aside from encapsulation, it is also necessary to 'underfill' a flip chip to protect its active surface and bumps from thermo-mechanical and chemical damage. Die attach basically consists of applying a die attach adhesive to the board or substrate and mounting the chip or die over this die attach material. Adhesive application may be in the form of dispensing, stencil printing, or pin transfer. Die placement must be accurate enough to ensure proper orientation and good planarity of the die. This is followed by a curing process (such as exposure to heat or ultraviolet light) that allows the adhesive to attain its final mechanical, thermal, and electrical properties. After curing, organic contaminants must be removed either by plasma or solvent cleaning so as not to affect the wirebonding process. The wirebonding process is similar to that used in traditional semiconductor assembly, i.e., thermosonic Au or Cu ball bonding or ultrasonic Al wedge bonding may be employed to connect wires between the die and the board or substrate. Chip-to-chip wirebonding may also be done for COB assembly. Needless to say, the bond pads of the die and the board or substrate must be free of any contaminants and defects to ensure the formation of good and reliable bonds. Finally, the die and bond wires are encapsulated to protect them from mechanical and chemical damage. Encapsulation is generally done by dispensing a liquid encapsulant material (usually epoxy-based) over the die and wires or by transfer molding. Encapsulants also need to undergo curing, the process of which depends on the type of encapsulant used.
Advantages offered by COB technology include: 1) reduced space requirements; 2) reduced cost; 3) better performance due to decreased interconnection lengths and resistances; 4) higher reliability due to better heat distribution and a lower number of solder joints; 5) shorter time-to-market; and 6) better protection against reverse-engineering.
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3. What is offset printing?
Offset printing is a widely used printing technique which is printed on PVC (PETG) or paper is made up of a combination of the 4 process colors of printing-Cyan, Magenta, Yellow, and black. The ink is spread on metal plate with etched images, and then transferred to another surface such as rubber blanket. The final stage of printing is apply the image to PVC (PETG) or paper by pressing it against the surface (such as the rubber blanket). For advantage of offset printing, there is a consistent high quality of color images and can print realistic photo images , complicated pictures(contains multiple colors). Images are also sharper and cleaner. In opposite of Screen printing, Offset printing is not unable to print out the high-definition colors. The type of printing is most efficient and economical when printing a large volume and printing the same design image. Offset printing, there is the overlay(the protection layer), can protect the proximity card from cutting, also can be used in a long time.
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4. What is Silk Screen printing?
The process is known as screen printing. A screen is made of a piece of porous, finely woven fabric (originally silk, called Silk Screen printing, but nowadays made of polyester or nylon) stretched over a wood or aluminum frame. Firstly, no using area of the screen is blocked by a non-permeable material where wont to be printed; that is, the open spaces are where the ink will appear. Secondly, the silk screen is placed above PVC sheet, Ink is placed on top of the silk screen (one color once), and use machine pressure method to push the ink evenly into the silk screen openings. Ink passes through the open of silk screen is printed onto PVC sheet. If more than one color, the process is same as above. Compare with Offset Printing, Silk Screen printing can print out high-definition colors, but not able to print like photo reality. Silk Screen printing also have the overlay to protect the proximity card surface to keep using in a long time.
