Need clarification for Fabrication and Standard ??

Hi everyone,
Generally i followed IPC-6012C Class 3 to fabricate board for Manufacturer and surface finished is ENIG.but now for Surface Finished immersion Tin need to use (because for low cost and proto-type board).Let me know which Class i need to follow for Fabricator and what is the different between HASL and ENIG ?
how much cost different will come for Immersion Gold/ Immersion silver/ Immersion Tin ??

For your info, a list of ALL the major PCB related IPC specs, should be in this lot somewhere:
1601: Printed Board Handling and Storage Guidelines
2141A: Design Guide for High-Speed Controlled Impedance Circuit Boards
2152: Standard for Determining Current Carrying Capacity in Printed Board Design
2221A: Generic Standard on Printed Board Design
2222A: Sectional Design Standard for Rigid Organic Printed Boards
2223B: Sectional Design Standard for Flexible Printed Boards
2225: Sectional Design Standard for Organic Multichip Modules (MCM-L) and MCM-L Assemblies
2226: Sectional Design Standard for High Density Interconnect (HDI) Boards
2251: Design Guide for the Packaging of High Speed Electronic Circuits
2252: Design Guide for RF/Microwave Circuit Boards
2316: Design Guide for Embedded Passive Device Printed Boards
2611: Generic Requirements for Electronic Product Documentation
2612: Sectional Requirements for Electronic Diagramming Documentation (Schematic and Logic Descript
2612-1: Sectional Requirements for Electronic Diagramming Symbol Generation Methodology
2614: Sectional Requirements for Board Fabrication Documentation
2615: Printed Board Dimensions and Tolerances
3406: Guidelines for Electrically Conductive Surface Mount Adhesives
3408: General Requirements for Anisotropically Conductive Adhesives Films
4101C: Specification for Base Materials for Rigid and Multilayer Printed Boards (English)
4103: Specification for Base Materials for High Speed/High Frequency Applications
4104: Specification for High Density Interconnect (HDI) and Microvia Materials
4110: Specification & Characterization Methods for Non Woven Cellulose Based Paper for Printed Boar
4121: Guidelines for Selecting Core Construction for Multilayer Printed Wiring Board Applications
4130: Specification & Characterization Methods for Nonwoven "E" Glass Mat
4202A: Flexible Base Dielectrics for Use in Flexible Printed Circuitry
4203: Adhesive Coated Dielectric Films for Use as Cover Sheets for Flexible Printed Circuitry and F
4204: Flexible Metal-Clad Dielectrics for Use in Fabrication of Flexible Printed Circuitry
4411A: Specification and Characterization Methods for Nonwoven Para-Aramid Reinforcement
4412A: Specification for Finished Fabric Woven from "E" Glass for Printed Boards
4552: Specification for Electroless Nickel/Immersion Gold (ENIG) Plating for Printed Circuit Boards
4553A: Specification for Immersion Silver Plating for Printed Boards
4554: Specification for Immersion Tin Plating for Printed Circuit Boards
4562A: Metal Foil for Printed Board Applications
4563: Resin Coated Copper Foil for Printed Boards Guideline
4761: Design Guide for Protection of Printed Board Via Structures
4781: Qualification and Performance Specification of Permanent, Semi-Permanent and Temporary Legend
4811: Specification for Embedded Passive Device Resistor Materials for Rigid and Multilayer Printed
4821: Specification for Embedded Passive Device Capacitor Materials for Rigid and Multilayer Printe
5701: Users Guide for Cleanliness of Unpopulated Printed Boards
5702: Guidelines for OEMs in Determining Accept Levels of Cleanliness of Unpopulated Printed Boards
5704: Cleanliness Requirements for Unpopulated Printed Boards
6011: Generic Performance Specification for Printed Boards
6012C: Qualification and Performance Specification for Rigid Printed Boards
6013B: Qualification and Performance Specification for Flexible Printed Boards
6017: Qualification and Performance Specification for Printed Boards Containing Embedded Passive De
6018A: Microwave End Product Board Inspection and Test
7094: Design and Assembly Process Implementation for Flip Chip and Die Size Components
7095B: Design and Assembly Process Implementation for BGAs
7351B: Generic Requirements for Surface Mount Design and Land Pattern Standard
7526: Stencil and Misprinted Board Cleaning Handbook - FREE DOWNLOAD
9201A: Surface Insulation Resistance Handbook
9252A: Requirements for Electrical Testing of Unpopulated Printed Boards
9691A: User Guide for the IPC-TM-650, Method 2.6.25, Conductive Anodic Filament (CAF) Resistance Te
9701A: Performance Test Methods and Qualification Requirements for Surface Mount Solder Attachments
9702: IPC/JEDEC Monotonic Bend Characterization of Board-Level Interconnects
9703: IPC/JEDEC Mechanical Shock Test Guidelines for Solder Joint Reliability
9704: IPC/JEDEC Printed Wiring Board Strain Gage Test Guideline
9708: Test Methods for Characterization of Printed Board Assembly Pad Cratering
A-142: Specification for Finished Fabric Woven from Aramid for Printed Boards
A-600H: Acceptability of Printed Boards
A-610E: Acceptability of Electronic Assemblies
A-620A: Requirements and Acceptance for Cable and Wire Harness Assemblies
AC-62A: Aqueous Post Solder Cleaning Handbook
C-406: Design & Application Guidelines for Surface Mount Connectors
CA-821: General Requirements for Thermally Conductive Adhesives
CC-830B: Qualification and Performance of Electrical Insulating Compound for Printed Wiring Assembl
CF-152B: Composite Metallic Materials Specification for Printed Wiring Boards
CH-65A: Guidelines for Cleaning of Printed Boards & Assemblies
CM-770E: Component Mounting Guidelines for Printed Boards
D-279: Design Guidelines for Reliable Surface Mount Technology Printed Board Assemblies
D-325A: Documentation Requirements for Printed Boards
D-326A: Information Requirements for Manufacturing Printed Circuit Boards and Other Electronic Asse
D-422: Design Guide for Press Fit Rigid Printed Board Back Planes
DR-570A: General Specification for 1/8 inch Diameter Shank Carbide Drills for Printed Boards
DR-572A: Drilling Guidelines for Printed Boards
HDBK-005: Guide to Solder Paste Assessment
HDBK-830: Guidelines for Design, Selection and Application of Conformal Coatings
JP002: JEDEC/IPC Current Tin Whiskers Theory and Mitigation Practices Guideline
J-STD-001E: Requirements for Soldered Electrical and Electronic Assemblies
J-STD-002C: Solderability Tests for Component Leads, Terminations, Lugs, Terminals and Wires - Incl
J-STD-003B: Solderability Tests for Printed Boards
J-STD-004B: Requirements for Soldering Fluxes
J-STD-005: Requirements for Soldering Pastes - includes Amendment 1
J-STD-006B: Requirements for Electronic Grade Solder Alloys and Fluxed and Non-Fluxed Solid Solders
J-STD-012: Implementation of Flip Chip & Chip Scale Technology
J-STD-020D-1: IPC/JEDEC Moisture/Reflow Sensitivity Classification for Nonhermetic Solid State Surf
J-STD-026: Semiconductor Design Standard for Flip Chip Applications
J-STD-027: Mechanical Outline Standard for Flip Chip and Chip Size Configurations
J-STD-028: Performance Standard for Construction of Flip Chip and Chip Scale Bumps
J-STD-030: Guideline for Selection and Application of Underfill Material for Flip Chip and Other Mi
J-STD-033B: Handling, Packing, Shipping and Use of Moisture/Reflow Sensitive Surface Mount Devices
J-STD-075: Classification of Non-IC Electronic Components for Assembly Processes
MC-790: Guidelines for Multichip Module Technology Utilization
ML-960: Qualification and Performance Specification for Mass Lamination Panels for Multilayer print
MS-810: Guidelines for High Volume Microsection
QF-143: Specifications for Finished Fabric Woven from Quartz (Pure Fused Silica) for Printed Boards
S-816: SMT Process Guideline & Checklist
SA-61A: Post Solder Semi-Aqueous Cleaning Handbook
SC-60A: Post Solder Solvent Cleaning Handbook
SG-141: Specification for Finished Fabric Woven from "S" Glass for Printed Boards
SM-780: Component Packaging & Interconnecting with Emphasis on Surface Mounting
SM-784: Guidelines for Chip-on-Board Technology Implementation
SM-785: Guidelines for Accelerated Reliability Testing of Surface Mount Attachments
SM-817: General Requirements for Dielectric Surface Mounting Adhesives
SM-839: Pre & Post Solder Mask Application Cleaning Guidelines
SM-840E: Qualification and Performance Specifiation of Permanent Solder Mask and Flexible Cover Mat
T-50H: Terms and Definitions for Interconnecting and Packaging Electronic Circuits
TR-001: An Introduction to Tape Automated Bonding Fine Pitch Technology
TR-486: Report on Round Robin Study to Correlate Interconnect Stress Test (IST) with Thermal Stress
TR-579: Round Robin Reliability Evaluation of Small Diameter Plated Through Holes in PWBs
TR-583: An In-Depth Look At Ionic Cleanliness Testing
WP/TR-584A: IPC White Paper and Technical Report on the Use of Halogenated Flame Retardants in Prin
WP-008: Setting Up Ion Chromatography Capability