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Wafer Sort and Test | Die Separation | Die Attach and Bonding | Packaging and Encapsulation

Wafer Sort and Test

After fabrication is completed, each finished wafer undergoes a sort process where the integrated circuitry on each specific die is electrically tested with computer-controlled probes. Each wafer may contain up to hundreds of separate dies or chips which are tested. Devices that fail the test are marked with a colored dye and sorted accordingly.

The following are the potential hazards of wafer sort and testing.

Die Separation

8" wafer

After sorting and testing, the individual dies are physically separated. Diamond scribing, laser scribing, and diamond wheel sawing are used for die separation. Diamond scribing is the oldest method and involves scoring a line across the wafer surface with a diamond tip. The wafer is then bent along the line, causing a fracture and separation. Laser scribing is similar except that a laser is used to score the fracture line. Diamond sawing involves wet-cutting the substrates with a high-speed circular diamond saw. Sawing may be used to either partially cut and scribe the surface, or can be used to completely cut through the wafer.

The following are the potential hazards of die separation.

Vaporization Products - Laser

Potential Hazard

  • Possible employee exposure to vaporization products from laser scribing.

Possible Solutions

  • Identify vaporization hazards and perform appropriate exposure evaluations.
    • Perform exposure measurements for the solvents used.
    • 29 CFR 1910.1000 Table Z-1 contains permissible exposure limits for various chemicals.
  • Provide appropriate ventilation to reduce concentration levels in the air.

  • Use respiratory protection [29 CFR 1910.134] when necessary to further reduce exposure and protect employees.

Additional Information

  • Occupational Health Guidelines for Chemical Hazards. US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 81-123, (1981, January). Provides a table of contents of guidelines for many hazardous chemicals. The files provide technical chemical information, including chemical and physical properties, health effects, exposure limits, and recommendations for medical monitoring, personal protective equipment (PPE), and control procedures.

OSHA Safety and Health Topics Pages:

Die Attach and Bonding

Wire bond machine

After separation into individual dies, the functional devices are attached to a lead frame assembly. Usually the chips are attached with an epoxy material. Once attached to the lead frame, electrical connections must be provided between the integrated circuit and assembly leads. This is accomplished by attaching aluminum or gold leads via thermal compression or ultrasonic welding.

The following are the potential hazards of die attach and bonding.

Epoxy Resins

Potential Hazard

  • Possible employee exposure to epoxy resins. Epoxy resins can cause both dermal and respiratory problems.

Possible Solutions

  • Identify epoxy resin hazards and perform appropriate exposure evaluations.
    • Perform exposure measurements for the solvents used.
    • 29 CFR 1910.1000 Table Z-1 contains permissible exposure limits for various chemicals.
    • Address all dermal exposures.
  • Provide appropriate ventilation to reduce solvent concentration levels in the air.

  • Provide PPE [29 CFR 1910 Subpart I] as appropriate to prevent eye and skin contact.

  • Use respiratory protection [29 CFR 1910.134] when necessary to further reduce exposure and protect employees.

Additional Information

  • Occupational Health Guidelines for Chemical Hazards. US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 81-123, (1981, January). Provides a table of contents of guidelines for many hazardous chemicals. The files provide technical chemical information, including chemical and physical properties, health effects, exposure limits, and recommendations for medical monitoring, personal protective equipment (PPE), and control procedures.

OSHA Safety and Health Topics Pages:

Metals

Potential Hazard

  • Possible employee exposure to metal fumes from thermal compression bonding.

Possible Solutions

  • Identify metal hazards and perform appropriate exposure evaluations.
    • Perform exposure measurements for the compounds used.
    • Keep exposures below acceptable exposure levels.
  • Address all dermal exposures.

  • Provide appropriate ventilation to reduce concentration levels in the air.

  • Provide PPE [29 CFR 1910 Subpart I] as appropriate to prevent contact.

  • Use respiratory protection [29 CFR 1910.134] when necessary to further reduce exposure and protect employees.

  • Maintain adequate housekeeping to remove unwanted metals and reduce concentration levels.

Additional Information

OSHA Safety and Health Topics Pages:

Noise

Potential Hazard

  • Potential occupational exposure to high noise levels from ultrasonic welding operations. Noise exposure may lead to occupationally induced hearing loss, hearing impairment, hypertension, elevated blood pressure levels and other health hazards.

Possible Solutions

  • A safety and health program that recognizes and addresses the hazards created by noise exposure.
    • Occupational Noise Exposure Standard [29 CFR 1910.95].
    • In addition, an effective hearing conservation program [29 CFR 1910.95(c)(1)], including specific requirements for monitoring noise exposure, audiometric testing, audiogram evaluation, hearing protection for employees with a standard threshold shift, training and education, and recordkeeping must be made available whenever employee exposures equal or exceed an 8-hour TWA sound level of 85 dBA, Occupational Noise Exposure Standard [29 CFR 1910.95].
    • Some examples of engineering and work practice controls to help decrease occupational noise exposure levels are:
      • Reduce the amount of sound energy released by the noise source.
      • Divert the flow of sound energy away from the worker.
      • Protect the receiver from the sound energy reaching him/her.
      • Maintenance of equipment properly, or replace equipment.
      • Revise operating procedures.
      • Redesign equipment and enclosures.
      • Use acoustical shields and barriers.
      • Wear personal protective equipment.

Additional Information

OSHA Safety and Health Topics Page:

Other OSHA material:

Microscopes

Potential Hazard

  • Prolonged use of microscopes for inspection can lead to eyestrain and other related ergonomic problems.

Possible Solutions

  • Address ergonomics as part of a safety and health program.

  • Use automated inspection equipment when feasible.

Additional Information

OSHA Safety and Health Topics Page:

Packaging and Encapsulation

After wire bonding is completed, the combined components are placed into a molding press and encapsulated in either ceramic or plastic materials. Final computer tests are then performed to evaluate whether the product meets specifications. According to test performance, the packages are separated into low- and high-quality circuits. The finished product is then packaged, labeled, and shipped to the customer.

The following are the potential hazards of packing and encapsulation.

Plastic Resins, Hardeners, and Fillers

Potential Hazard

  • Possible employee exposure to plastic resins, hardeners, and fillers used for encapsulation.

Possible Solutions

  • Identify chemical hazards and perform appropriate exposure evaluations.
    • Perform exposure measurements for the solvents used.
    • 29 CFR 1910.1000 Table Z-1 contains permissible exposure limits for various chemicals.
    • Address all dermal exposures.
  • Provide appropriate ventilation to reduce solvent concentration levels in the air.

  • Provide PPE [29 CFR 1910 Subpart I] as appropriate to prevent eye and skin contact.

  • Use respiratory protection [29 CFR 1910.134] when necessary to further reduce exposure and protect employees.

Additional Information

  • Occupational Health Guidelines for Chemical Hazards. US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 81-123, (1981, January). Provides a table of contents of guidelines for many hazardous chemicals. The files provide technical chemical information, including chemical and physical properties, health effects, exposure limits, and recommendations for medical monitoring, personal protective equipment (PPE), and control procedures.

OSHA Safety and Health Topics Pages:

Ultraviolet (UV) Radiation

Potential Hazard

  • Possible employee exposure to ultraviolet (UV) radiation from certain types of testing equipment.

Possible Solutions

  • Identify UV hazards; perform exposure evaluations when applicable.

  • Enclose operations with UV emissions; provide shielding and interlocks as necessary.

  • Provide PPE [29 CFR 1910 Subpart I] as appropriate during operations when exposure is necessary.

  • Implement UV radiation safety programs to further identify and control UV hazards.

  • Provide adequate ventilation to control ozone concentrations, which may be generated from UV radiation.

Additional Information

OSHA Safety and Health Topics Pages:

Wafer Sort and Test | Die Separation | Die Attach and Bonding | Packaging and Encapsulation



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