Miniature, Precision Connectors
• complex parts, particulate removal
• materials compatibility/parts deformation
• sharp production ramp-up
• implemented hydrofluoroether in automated, contained, airless cleaning system
Light oils
and particles must be removed from precision connectors to assure acceptable
performance. The process is high throughput; the
product has a high
value; and there are a large number of products and materials of construction.
The components are complex with many different materials of construction
and blind holes. Materials compatibility with the proposed cleaning
process and
temperature sensitivity resulted in major challenges during process development.
Materials changes during process development resulted in rejection of
an initially-promising class of cleaning agents.
Regulatory permits for this East Coast facility initially were so stringent
as to prohibit the desired growth. On communicating with the local agencies,
it was determined that allowable cleaning agent usage could be increased
sufficiently to meet expansion requirements of the company.
Several process options were identified. After preliminary evaluation of cleaning agent and cleaning equipment performance, a hydrofluoroether was selected. A number of cleaning systems were evaluated in terms of initial costs, operating costs, process consistency, reliability/robustness of equipment and process, and environmental considerations. An airless (vacuum) cleaning system was selected in order to:
• minimize solvent usage
• minimize solvent costs
• maximize process consistency
• avoid potential future regulatory problems
Given the somewhat longer process time required in using airless systems, careful attention was given to appropriate sizing of the equipment to allow for anticipated future growth.
High-volume Lead Frame Assemblies
• precision metals cleaning
• microelectronics/ wafer fabrication assembly
• high solids flux, heavy lard oil, particulates
• fast-track to process selection
• low-flash point system adopted, cyclohexane/isopropyl alcohol azeotrope
High precision processes for removing heavy lard oil and very high solids flux were developed and incorporated into a complex assembly system. The assembly facility is located in Mexico. In this instance, overall regulatory requirements were more stringent than would be found in many areas of California.
The project required coordinating the activities of manufacturing
facilities in Mexico and in the United States. Because
there had been extensive
attempts at process development by various groups within
the company and because the
soils are very difficult to remove, a team including
engineering, production, safety/environmental, management, and facilities
management was set up
to coordinate process development. Despite the difficulty
in soil removal, several promising
processes were found.
Once the more promising processes were found, larger-scale
pilot performance studies were conducted at the facilities
of potential
equipment suppliers.
Equipment options were evaluated in terms of costs
and reliability. The company chose a low-flash point solvent
system using a
cyclohexane /isopropyl
alcohol
azeotrope with a highly-automated low flash point system.
Process selection was accomplished within 4 months
of the start of
the coordinated project.
The process has been successfully in place for a number
of years; and several process
lines of the same type have been added to accommodate
increased production.
Reference:
Malella. M., Teccor, Inc, et al., "Integrating Precision De-Oiling and Defluxing Processes in High Volume Manufacturing Systems," IPC Presentation and Proceedings, San Diego, CA, May, 1995.
Evaluation of Biobased Solvents for Ink Removal
A small company wanted to eliminate the use of
acetone for removal of a specialty ink from metal
and composite
mesh tooling.
They
required
an aqueous or a VOC-exempt
option. The initial information provided by the
company was that a relatively simple ester-based
ink was
routinely used;
soy methyl
esters would be
a promising option; aqueous cleaning was also
a possibility. Unfortunately, after inspection
of the actual process, it was determined that
a two-part epoxy-like ink was used. The temperature
and time
required to use aqueous
resulted in
the inks
curing before they could be removed. Parameters
for using Biobased materials were determined;
somewhat elevated
temperature and
ultrasonic cleaning
were required.
Inertial Navigation Systems Sub-Assemblies
• low-volume, high value assemblies; multi-step assembly
• complex components, beryllium, other metals & non-metals
• process time reduced by over 40%
• cleaning agent usage reduced to one-third
Assembly of inertial navigation systems involves exacting, multi-step cleaning of complex subassemblies. The product is very high value; the processes are very low-volume. Each sub-component of a system may require various cleaning steps; each performed by skilled assemblers. Fluxes, oils, and flotation fluids must be removed from an array of materials of construction including a wide assortment of metals (including beryllium), plastics, and epoxies. The diversity of metal and non-metal materials of construction is extensive. For the given product application, soil residues, cleaning agent residues, and water are not acceptable. In addition to meeting stringent customer, performance, and regulatory requirements, the processes had be practical and reliable.
After extensive evaluation, 1,1,1-trichloroethane was initially replaced
by a multi-step process involving high-boiling
solvents followed by perfluorinated solvents and volatile
methyl siloxanes. While the
process provided acceptable
cleaning, it was very time-consuming.
Further, there
was ongoing concern with
potential for cleaning agent residue.
Therefore, as a second phased, the
company evaluated other options that
were not
available early on
in the phase-out
of ozone depleting
chemicals.
Optimizing
the processes involved coordination
among engineers, chemists, environmental
health
and safety specialists,
and vendors.
A range of cleaning agents
was evaluated including co-solvent
systems, fluorinated solvents, and
brominated
solvents.
The company tested and implemented
alternative cleaning sequences
involving an aggressive
solvent with final
cleaning in a perfluorinated
material.
The new processes were determined
to provide effective, reliable
cleaning. As indicated
below, cleaning process time was
reduced
by over 40% and cleaning agent
usage was reduced
to one
third of
its original
volume
over the interim
process. The
original processes were typically
6 to 18 steps, required three or
more
different
solvents,
and took up to several
hours to
complete. Process
improvements are
summarized as follows:
Typical Process |
Cleaning
Time (Min) |
Cleaning
Steps |
Solvent
Usage (Gal/week) |
Interim
Process |
35 |
4 |
45 |
New Process |
20 |
3 |
15 |
References:
1) Carter, M., et. al., “Cleaning High Precision Inertial Navigation Systems, A Case Study and Panel Discussion,” presentation and proceedings, CleanTech ’99, Rosemont, IL, May, 1999.
2) B. Kanegsberg, B. et al., "Development and Implementation of Non-Ozone Depleting, Non-aqueous High Precision Cleaning Protocols for Inertial Navigation Subassemblies," Microcontamination '93 Proceedings, San Jose, CA, October, 1993.
Precision Cleaning; Mixed Substrates (metal and non-metal)
