Material Composition
Weight percentage ratios of polymer matrix to glass fiber reinforcement define the physical composition of prepreg and laminate substrates. Substrate resin content governs dielectric constant values and resin fill capability during lamination. Higher resin fractions reduce overall dielectric constant while increasing out-of-plane thermal expansion.
Laminate thickness calculations use resin percentage parameters to predict final pressed thickness after copper flow. Characterization bounds cover prepreg materials and cured laminate cores, ending where pure unreinforced resin systems or pure glass weaves are evaluated independently.
Flow Property
Lamination press cycles rely on controlled resin volume to fill inner layer copper features. Insufficient substrate resin content leads to resin starvation and void formation around thick copper traces. Excessive resin content increases z-axis thermal expansion, elevating microvia stress during reflow soldering.
Matching resin percentage to copper weight distributions ensures complete encapsulation without excessive panel thickness variation.
Acceptance Criteria
Quality testing standard IPC-TM-650 Method 2.3.16 uses burn-off test procedures to measure resin weight percentage in cured laminates. Differential scanning calorimetry verifies degree of cure in high resin content prepreg lots. Material data sheets specify resin content tolerances for incoming raw material inspection.
Fabricators track resin percentage across prepreg batches to maintain targeted dielectric layer thickness after pressing.
