Progressive Energy Dynamics: Key to Low Standoff Cleaning The Science of Cleaning PED

 Space under components is shrinking  Interconnect densities are increasing  Performance requirements are increasing  Lead-free & no-clean are harder to clean  Fluxes are fully filling small gaps 1. What’s the Problem ?

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 the surface = mass x velosity the surface 2.Fluid Flow Theory – Cleaning Small Gaps Depends on 2 things - - -

Δp = 2γ cosθ / R  Interfacial pressure differential calculation γ = surface tension R = radius meniscus Θ = contact angle of liquid at surface 2.How much energy does it take to clean tight spaces? Δp = γ cosθ / R planar cylinder 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.

 Relationship between gap size and capillary force for water on glass Planar: Cylinder: 2. Fluid Flow Theory – Small unfilled Gaps Interfacial pressure difference at equilibrium 10 1 psi 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!

(Resistors, Capacitors, LCC’s, QFN’s) Flux around 0603 Cap Flux under cap 3. Fully Filled Gaps are Much Harder

 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 3. Fluid Flow Theory – Filled Gaps

Research leading to PED

 PED Works in a standard in-line configuration Treatment system Pre- Wash Chemical Isolation Rinse Final Rinsing Dryer Wash 4. Inline Progressive Energy Dynamics Approach (PED)

 New approach to design in-line cleaner  Involves a manifold design with increasing energy at each manifold 4. Inline Progressive Energy Dynamics Approach Low Energy Jet Medium Energy Jet High Energy Jet Highest Energy Jets Pre-wash Wash 1 Wash 2 Wash 3 Heat & wet penetrate form flow erode surfaces outer layer channels flux

 Wash section equipped with progressive energy dynamics 4. Inline Progressive Energy Dynamics Approach Soften Outer Shell Create Flow Channels Erode Flux Residue

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: 4. Inline Progressive Energy Dynamics Approach 961 I/O “glass on glass” Flip Chip