The Science of Cleaning Green Progressive Energy Dynamics (The Key to Low Standoff Cleaning) The Science of Cleaning Green

What’s the Problem ? Space under components is shrinking Interconnect densities are increasing Performance requirements are increasing Lead free & no-clean are harder to clean Fluxes are fully fillng small gaps

Fluid Flow Theory – Cleaning Small Gaps Depends on 2 things. . . 1. Physical properties of the cleaning agent (surface tension, density and viscosity) 2. Higher energy fluid delivery (flow rate and impact velocity) Energy Delivered is dependent on equation for Kinetic Energy Kinetic Energy @ the surface = mass x velosity2 @ the surface

How much energy does it take to clean tight spaces? Interfacial pressure differential calculation NOTE: if θ is greater than 90˚, as with water on waxy surface, the force becomes negative or repulsive. If surface is wetted, force pulls the fluid into the gap. planar cylinder γ = surface tension Θ = contact angle of liquid at surface R = radius meniscus

Fluid Flow Theory – Small unfilled Gaps Relationship between gap size and capillary force for water on glass Interfacial pressure difference at equilibrium psi 10 Planar: Cylinder: 1 0.1 0.01 0 20 40 60 Gap/diameter, mils

Surface effects in tight spaces retard fluid flow (computer model of flow in 50 micron gap) Component

And that’s the easy stuff!

Fully Filled Gaps are Much Harder (Resistors, Capacitors, LCC’s, QFN’s)

Fluid Flow Theory – Filled Gaps 3 steps are required to remove a fully blocked gap: 1 Outer solvent depleted zone softened 2 Liquid jet with sufficient energy forms flow channels 3 Bulk residue is eroded & dissolved by fluid flow Steps 2 & 3 require substantial Energy

Research leading to PED

Inline Progressive Energy Dynamics Approach (PED) Treatment system 2 1 3 4 5 6 Pre- Wash Chemical Isolation Rinse Final Rinsing Dryer Wash PED Works in a standard in-line configuration

Inline Progressive Energy Dynamics Approach New approach to design in-line cleaner Involves a manifold design with increasing energy at each manifold Pre-wash Wash 1 Wash 2 Wash 3 Low Energy Jet Medium Energy Jet High Energy Jet Highest Energy Jets Heat & wet penetrate form flow erode surfaces outer layer channels flux

Inline Progressive Energy Dynamics Approach Wash section equipped with progressive energy dynamics Soften Outer Shell Create Flow Channels Erode Flux Residue

Inline Progressive Energy Dynamics Approach A Progressive Energy Design is: A fluid delivery system Recognizes the 3-step process required to clean flux-filled spaces Delivers only what is needed at each step 961 I/O “glass on glass” Flip Chip