Non-Fabrication Processing
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.
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:
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:
Accessibility Assistance: Contact the OSHA Directorate of Technical Support and Emergency Management at (202) 693-2300 for assistance accessing PDF materials.
*These files are provided for downloading.
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