Flexible PCB Audit Checklist




SFS Buyer's Guide
Copper Laminate Standard panel sizes with saw-cut edges. This significantly reduces contamination in subsequent processes (e.g., imaging, testing, etc.)
Drilling SFS' lowest-end drilling machines are Excellon System 2000 and Century 2001 CNC drillers. All of these machines are equipped with automatic measurement systems that measure drill bit length, diameter, spindle runout, and broken drill bit detection. Essentially, these capabilities remove the human element from these drilling issues, thereby minimizing the chance of operator error. SFS also has three Mania Micronics 86 drilling machines. These machines incorporate the industry’s latest linear motion technology and 180k RPM high speed spindles. The use of linear motion increasing hole position accuracy from an industry standard of +/- 0.002” down to +/- 0.0005”, including in the Z-axis, which makes these ideal for controlled depth blind via drilling.
Image Room Class 10,000 Clean Room minimizes foreign material from creating common shorts in the imaging process. Strict temperature and humidity controls prevent distortion in customer artwork.
Imaging/Exposure Standard: SFS uses MultiLine equipped drawers for imaging. MultiLine tooling removes the human factor involved in lining up the bottom film to the top film. This results in significantly reduced off-registration issues.

Advanced (inner layers): SFS also employs the use of an Olec AX-28 automatic exposure unit that uses two cameras to align the top and bottom artwork. This machine can hold registration as tight as +/- .0005 mils front to back for inner layers.

Industry-Leading (inner and outer layers): SFS has purchased and installed four Olec AT-30 automatic alignment exposure units. These units use four cameras to align artwork top to bottom, and then use panel motion systems to automatically adjust the panel position to a best fit to the artwork. Furthermore, these units have hybrid-collimated light units that ensure exposure light attacks the panel at 90 degree angles to the artwork, which is critical for fine line resolutions.
Plated Through Hole (PTH) SFS has two plating lines installed. SFS has built a custom automatic plating line that has been designed and constructed primarily in-house. The intent was to minimize plating variation, which is the main goal of production plating. This was accomplished by including the following:

  • Houses racks that only allow panels to be plated one-high.
  • Anode-to-anode distance is 24 inches (max distance for plating).
  • Water-submerged positive cathode contact.
  • Chemical-submerged anode bars for positive contact.
  • Eductor system HV chemical flow parallel to panels for chemical agitation.
  • Mechanical agitation allows chemical to flow through holes.
  • Vibration removes air from microvias and blind microvias.
  • Dual-sided rectification equalizes Cu plating throughout rack.
  • Innovative rectifiers (2-per-rack) with 0.5% max ripple effect.
  • Reverse pulse plating reflectors for high-aspect ratios and blind via plating.
  • Panels plated at 15 ASF (industry avg: 45 ASF) ensures uniform plating.
  • High ductile plating process meets C7000 specs for 1,000 hour cycle tests.
  • Chemistry revised for high-aspect ratio plating.
  • Lines calibrated to plate 10:1 aspect ratio.
Strip-Etch-Strip
Hollmuller SES line incorporates the latest in spray technology that minimizes chemical puddling. This is line capable to accurately and uniformly etch down to 2 mil lines and spaces.
Pre-LPI Cleaning Instead of using a chemical cleaning process that may increase ionic contamination and compromise the surface finish, SFS utilizes an Aluminum Oxide Jet Scrubber. This process uses aluminum oxide slurry that is sprayed on the panels to remove copper oxidation.
LPI Soldermask Three Argus spray coating lines for less soldermask within holes and eliminates dimple marks on the board surface resulting in uniform soldermask thickness across product surface area.
LPI Image
Three Olec AT-30 automatic alignment exposure units use four cameras to align artwork top to bottom, and then use panel motion systems to automatically adjust the panel position to a best fit to the artwork. Furthermore, these units have hybrid-collimated light units that ensure exposure light attacks the panel at 90 degree angles to the artwork, which is critical for fine line resolutions.
LPI Developing SFS has conveyorized the developing, final baking, and cleaning processes into a single production line. This should improve quality through reduced handling and utilizing higher-end machinery. Our developing line is constructed of a single-chamber, stainless steel developing line.
Final Baking
SFS has installed a Bassi Tunnel oven to perform final baking. Since heat is uniformly applied to the boards and the machine controls the cycle time, quality is improved dramatically.
Cleaning SFS installed a Hollmuller conveyorized cleaning line in 2009, in line with the other major wet process upgrades we have made since 2007.
HASL
Four Lantronics TT-30 vertical hot air levelers designed with the intent of using this finish on finer pitch devices than in the past. SFS uses two of these units for SnPb HASL and another two for Nihon Superior’s SN100CL lead-free solder finish process.
HASL Post-cleaner SFS has custom fabricated a high-pressure, high-temperature post-cleaner for use after the HASL process. This is a stainless steel post-cleaner unit that runs at 150°F, sprays regular and D.I. water at 1 to 1.5 gallons per minute at 50 psi using 7.5 HP pumps (1/2 gallon per minute, 20-30 psi, 1.5 HP is the best available on the market). Furthermore, the cleaner uses 8-1” wide toothbrush-type agitating brushes versus an industry best of 4-0.5” brushes. This custom process has been proven to remove ionic contamination from the surface of PCBs to well below industry standards.
Inspection
SFS augments its visual inspection process by utilizing automated optical inspection equipment. The AOIs have been outfit with a visual final Inspection software module which can adjust the standard inspection process.
Electrical Testing SFS offers a variety of testing alternatives. First, SFS has 5 Mania double-sided, double-density grid testing machines. The fixture cost for these testers is half the cost or less than those used in more traditional clam shell testers since we build everything in-house. Also, SFS utilizes six flying probe testers for smaller and prototype orders. This allows the customer to forego the cost of a hard testing fixture and, instead, pay a modest testing fee.
Cleaning after Routing
SFS has installed a washer in its shipping department that uses de-ionized (D.I.) water to clean the boards. D.I. water results in a cleaner board, but more importantly it further removes ionic contamination that may have occurred after HASL.
Duplicate Processes All of SFS' processes incorporate duplicate equipment so that in the case of an equipment failure, SFS’ production capabilities will not be compromised.
Advanced Capabilities
In-house capabilities include laser drilling, laser routing, PTFE plasma preparation, Plasma treatment and etchback, and special project groups to assist customers with critical and technologically demanding products.
Min Hole Size .002”
Min Line/Space
.003” / .003”
Surface Finish  HASL; Lead-free HASL; Immersion Silver; Immersion Gold; OSP; Full Body Gold
Certifications
 ISO 9000:2000, TS16949, Delphi C7000, ISO14000; AS9100; ITAR
Financial Liabilities  $0 Bank Debt; $0 Accounts Payable; $0 Lease obligations