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PG Enterprises
Servicing the Semiconductor Industry Since 1976

Material and Design

In order to achieve maximum efficiency with the use of ultrasonic wire bonding, the die, the package and the wire must be compatible with the bonder as well as each other. Here we will show some guidelines to be followed.

Material
The materials we are talking about are those materials that are in direct contact with the wire. There are some materials that will not bond to aluminum wire no matter how much care is taken. There are also materials that can produce good bonds under certain conditions and usually the quality is dependent on the purity of the material or the process to which it is applied. Materials that are recommended for ultrasonic wire bonding are those that have always produced good results.

Selected Bond Pad Material for Aluminum Wire
BEST CONDITIONAL POOR
Aluminum Palladium Silver Tin
Nickel Palladium Gold Stainless
Gold (plated) Platinum Solder
Gold (thin film) Platinum Silver Iron
Copper Platinum Gold Ceramic
Silicon Gold (thick film) Brass
Metal on PC Boards Plastic
Anodized Aluminum
Silver
Zinc
Carbide
Kovar
Constantin

Wire specifications
The next step in designing a product is to determine the amount of current to be carried through the device. Once the current is known, the minimum wire size is easily derived through a formula.

Bond pad considerations
After the wire size is known the next step is to design the die to accommodate the wire. The width of the pad must be twice the diameter of the wire and the length should be between 3 to 3.5 times the diameter of the wire.

 

 

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Gold is the most malleable and ductile of all metals.

Silver tarnishes more these days because of sulfur pollution from power plants. Before the Industrial Revolution, silver hardly tarnished at all.

Aluminum is the third most abundant element in the earth's crust. However, since it's never found in a pure state the refining process makes it one of the more expensive metals. Aluminum is everywhere -- many gemstones, for example ruby and sapphire, are mainly crystalline aluminum oxide (Al2O3). In addition, many of the world's top performance vehicles, like the Ferrari 360 Modena and the Audi A8, are 100% aluminum, since it's lighter than steel but at least twice as strong.

Lead - Pb, as in plumbum which is Latin for "lead". The Ancient Romans made their plumbing out of lead.

Letter J - The only letter in the alphabet NOT appearing in the Periodic Table of the Elements