Analytical Models for Viscous Squeeze Flow Trace Swim in Multilayer Buildups
Analytical squeeze flow models predict trace swim by calculating hydrodynamic drag and side-wall pressure differentials across fine copper features during lamination.
Laminate Peel Strength
Bond Integrity
Copper foil adhesion to a dielectric substrate determines laminate peel strength during mechanical loading in multilayer circuit board fabrication. Peel resistance measures the force required to separate metallic conductors from the underlying resin matrix under a controlled pulling angle. Etched circuit traces rely on this interfacial bond during thermal excursions encountered in wave soldering and surface mount reflow cycles.
Delamination occurs when mechanical stress or thermal expansion differentials exceed the adhesive energy holding the copper layer against the glass epoxy plies. Destructive physical testing pulls anchored conductors at a fixed ninety degree angle while recording pounds per inch of width.
Resin Treatment
Pressure and temperature profiles applied during press consolidation govern the bond quality achieved between treated copper foil and prepreg sheets. Surface roughness profiles etched into the matte side of electrodeposited copper provide microscopic anchorage points for flowing epoxy or polyimide resin during high heat pressing. Bond strength drops when excessive resin flow leaves the foil surface starved of matrix material or when undercure leaves the polymer matrix insufficiently crosslinked.
Shear stress generated during high speed routing and drilling tests the limits of this interfacial adhesion before component assembly begins.
Failure Analysis
Low force readings during destructive pull testing expose chemical contamination on the copper treatment or incomplete prepreg wetout during lamination. Thermal stress screening through solder float testing induces rapid moisture vaporization inside the dielectric core, creating internal vapor pressure that pushes copper conductors away from weakened resin interfaces. Blistering and lifting along printed traces after thermal exposure indicate localized reductions in interfacial fracture toughness caused by poor press parameters.
Controlled depth milling and microsectioning reveal void distribution and resin starvation along the copper dielectric boundary following fabrication nonconformances.