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Die Products have been singulated and assembled into individual packages for over 40 years. During this time, standardized and formalized processes have been developed to insure that highly reliable product is assembled. The use of die products in applications previously populated by packaged product requires that consideration be given to the unpackaged die since its format is different than the packaged product. Whilst unpackaged die are robust in the proper assembly environment, improper handling has the potential to result in unreliable assemblies. In utilizing unpackaged die, consideration must be given to:
Foreign Material: among the most common are skin, hair, spittle, cosmetics, dust, dirt, fingerprints, airborne particles, machine oils and friction by-products. The effects of foreign material is often observed as electrical leakage, electrical shorts, latent failures, visual defects and corrosion. Techniques for controlling foreign material during processing include the use and implementation of proper air filtration, cleanroom smocks, face masks, gloves, hairnets, work area hoods, equipment maintenance, housekeeping and employee training. Product should be handled only in a class 10,000 or better designated clean room environment.
ESD: electrostatic discharge can have the same effects on die products as those experienced with packaged devices. The typical failure modes observed are state or level upset effects, immediate device breakdown and latent damage causing subsequent failure. Cumulative degradations effects are possible from repeated exposures to ESD events that do not cause immediate failure. Techniques for controlling ESD levels during processing include maintaining humidity levels of 30% to 60%, using of conductive or static dissipative materials, using air ionizers, providing conductive paths to ground for personnel and work surfaces, and implementing an employee training program. Standard ESD precautions and safe work environments are as defined in MIL-HDBK-263.
Picking singulated die: singulated die should not to be handled with metal tweezers. A vacuum wand with a non-metallic ESD protected tip needs to be used to insure damage free picking.
Ultraviolet Light: ultraviolet (UV) sensitive products need to be handled in a manner that minimizes the exposure of the product to UV light. (Note: Products with UV light sensitivity will be identified on the applicable die product datasheet) EPROM-based microcontrollers that have been programmed will be erased if exposed to an energy level of 15 Watt-Seconds/cm2 based upon a UV-C wavelength of 253.7 nanometers. In general, UV-C (200-280 nm) and UV-B (280-315 nm) will also result in erasure if the product is exposed to a 15 W-S/cm2 energy level.It is recommended that any manufacturing/handling environment where UV sensitive products are exposed to light be monitored for UV-C and UV-B levels to ensure that the 15 W-S/cm2 is not violated. To determine the energy exposure level multiply the irradiance (Watts/cm2) by the time of exposure (Seconds) at a given location. The summation of the calculated energy levels for each location will be the total energy level the product has been exposed to. This energy level should not exceed the 15 W-S/cm2. A typical irradiance value (Combined UV-C and UV-B spectrum) for an office area lit by overhead fluorescent lighting is ~ 0.02 microWatts/cm2. Irradiance on assembly type equipment can be on the order of ~ 1.00 microWatts/cm2. These values should not be used to determine the energy level of the manufacturing/handling area in question but as a guideline in regards to the order of magnitude for irradiance.
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