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QFN Package Copper & Gold Wire Bonding Capillary

Country/Region china
Company Small Precision Tools company
Categories Lead Wire
Telephone 12345678900
ICP License Issued by the Chinese Ministry
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    QFN Package Copper & Gold Wire Bonding Capillary

    As the consumer market aggressively demands for the miniaturization of electronic products with more functionality, the requirement for small IC components has significantly increased, particularly on QFN packaging. Two major advantages of QFN over other leaded packages are - cost to manufacturer (for small, thinner, lighter in size, hence promoting more units per lead frame) and improved performance ICs (for better thermal dissipation and reduction in lead inductance).
    In general, QFN packages are available in two types - a punch type and a sawn type. A sawn type typically comes with a polyimide tape before die attach or wire bond process. The purpose of the tape is to prevent the bleeding of the resin from the molding compound into the backside of the QFN leadframe. However, the polyimide tape causes the lead to bounce when exposed to high temperature coming from the heater block.

    punch type
    Polyimide Underneath Strip

    Challenges of Bonding QFN

    QFN wire bonding has its own special characteristics as compared with other leaded packages. Looking at the wire bond process set up, QFN is much more complicated than other packages and these are highly influenced by the following three factors, as shown in Figure 1 below:

    Figure 1 Factors affecting QFN Bonding

    The QFN package tie bar width and thickness design greatly affect the wire bonding performance. Wider and thicker lead configuration are preferred as this will have lower reaction towards leads bouncing during the wire bonding process. Lead bouncing is more prominent on tape QFN where the tape actually softens” when subjected to high bonding temperature of equal or more than 200C. The softening” effect will absorb certain amount of USG power needed for better weldment of the wire to the lead surface to form the stitch.

    The effect of QFN matrix leadframe made it impossible to design a clamping system which will hold the middle fingers at the center of the bonding area
    (Figure 2). Under this condition, the best way to clamp or hold QFN matrix leadframe would be around its perimeter. Consequently, this leaves the middle of the QFN matrix leadframe area prone to micro bouncing. The micro-bouncing effect will always be inherent with the QFN bonding (with tape underneath), causing some instability issue in second bond deformation.
    In a typical stitch bonding (second bond) process, the use of lesser USG power setting is more preferred for QFN with tape underneath. This is to minimize the micro bouncing effect translated to the ball bond (first bond) causing ball neck stress or damage as shown in Figure 3.

    Figure 2
    Matrix Clamping Design
    Figure 3
    Stress Mark Above the Deformed Ball

    The introduction of thermocompression (a combination of force & temperature - Figure 4) - alleviates micro-bouncing effect on the QFN matrix leadframe, resolving ball neck stress or damage. Usually, a longer bonding time of more than 15 milliseconds with high and gradually ramping up bond force profile, ranging from more than 100g to less than 500g (depending on wire size) are pre-requisites for good thermocompression bonding. The introduction of thermocompression bonding reduces the effect of the micro bouncing providing better quality bonding and smoother bonding performance that are necessary in mass volume production environment.
    Figure 4: Use of thermocompression in QFN

    What is SPT’s new SQ capillary?

    SPT’s new SQ capillary series features a consistent surface morphology finishing used for both gold (Au) and copper (Cu) wires, specifically developed for QFN wire bonding. The SQ capillary is designed in line with thermocompression bonding concept. The uniqueness of the SQ capillary is shown in the actual bonding response in terms of higher productivity (due to improved MTBA & higher capillary touchdown) and reliability of the bonded product.

    Improved MTBA

    With SQ capillary, there will be
    Quality QFN Package Copper & Gold Wire Bonding Capillary for sale
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