Cleaning Process Options Solvent Selection

Why do we Clean? We clean to ensure product reliability –remove ionic / acidic contamination and particulates that can cause problems in use of the product We clean to prepare surfaces –remove oils and flux residues that can inhibit the bonding of conformal coatings / insulation coatings –remove flux residue from underfill areas –prepare surfaces for bonding or coating We clean to meet specification requirements –because it is in the contract

Was No-Clean technology developed by Military Intelligence? The phrase “No-Clean” is incorrect. These types of fluxes and pastes correctly should be referred to as “Synthetic” Fluxes Many “Synthetic” fluxes and pastes are cleaned Steve Stach / AAT

No-Clean Fluxes really are Synthetic Fluxes Traditional fluxes are limited Rosin fluxes must contain rosin –Inherently sticky not as printable for Fine Pitch Water solubles must be water soluble –Shorter printing life, less tack harder to process -must be cleaned Synthetic Fluxes have no formulary restrictions –Can be formulated to optimize the process Printability, tack, printing life, cleaning or no clean Steve Stach / AAT

Flip Chip cleaning prior to under-fill improves reliability by preventing under-fill voids and delamination Under-fill Void traps foreign matter and concentrates physical force Delamination of under-fill will cause premature solder failure Steve Stach AAT

Lead free soldering requires stronger fluxes/cleaning or nitrogen oven inertion No-lead residues are discolored due to higher temperature profiles

Types of Cleaning Options Vapor Degreasing LENIUM GS, 3M HFEs Aqueous ALPHA 2110 HYDREX SP / SP-50 KYZEN 4520 ZESTRON AC200 Semi-Aqueous BIOACT EC-7R AXAREL 32 / 36 / 46 BIOACT SC-22 Evaporative Solvents IPA, Acetone, MEGASOLV JB, AXAREL 2200

Cleaning Technologies with Differing Benefit Trade-offs Aqueous Cleaning Evaporative Solvent Cleaning Semi-aqueous Cleaning Vapor Degreasing Out-Sourced Cleaning

Cleaning Options Aqueous –Water Wash with Water Rinse Semi-Aqueous –Hydrocarbon Wash / Water Rinse Vapor Degreasing –Heated Solvent Vapor Wash and Rinse Evaporative Solvents –Hydrocarbon Wash and Rinse Contract Cleaning –Contractor Responsible for Part Cleaning

Cleaning Trade-offs

Aqueous Cleaning Advantages –Low VOCs –Cleans Most Contamination –Chemicals Inexpensive –Equipment low to Moderately Expensive –Short process cycle - inline Disadvantages –Wastewater Treatment / Neutralization –High Energy Cost –Medium to Long Process Cycle - Batch –Government Restrictions on Water Use

Evaporative Solvents Advantages –Easy to use –Chemicals Relatively Inexpensive –Process Time Under 20 minutes –Good for Cleaning Stencils / CCAs / Misprints Disadvantages –High VOC Content –Safety concern, Flammable/combustible –Waste Disposal –Can just move dirt around

Semi-Aqueous Cleaning Advantages –High VOCs, but Low Evaporation –Cleans Most Contamination –Chemicals Moderately Expensive –Many Products are Biodegradable Disadvantages –Moderate Energy Cost –Medium to Long Process Cycle –Good Machines Are Expensive

Vapor Degreasing Advantages –Solvent is Continuously Recycled –Cleans Most Organic Contamination –Process Time Under 10 Minutes –Excellent for Cleaning Fine Pitch / BGAs / Blind Holes / Machined Parts Disadvantages –Not so good for polar soils –Low to Moderate Energy Cost –Chemicals Must Be Handled Carefully –Chemicals Expensive & volitile –Systems can can become acidic with water contamination –VOC issues

Contract Cleaning Advantages –Contract Professional Manages the Cleaning Process –No Chemicals to Buy; No Maintenance –No Permits to Meet –No Equipment to Purchase Disadvantages –Not many