Perimeter Stitching via Pitch Selection for Circuit Board Shielding
Perimeter via pitch selection requires matching ground via spacing to less than one-twentieth of target frequency wavelength while verifying barrel plating thickness.
FR-4Tg Laminate
Substrate Specification
Flame-retardant epoxy materials graded by their glass transition temperature establish the primary thermal operating limits for standard electronic assembly. An FR-4Tg laminate represents a printed circuit board substrate with a specified glass transition temperature, above which the epoxy resin transitions from a hard, glassy state to a soft, rubbery state. This transition temperature determines how much thermal stress the substrate can withstand during lead-free soldering processes.
By selecting a material with a high glass transition threshold, engineers can ensure that the board retains its structural integrity and dielectric performance during high-temperature reflow and subsequent harsh environmental exposure.
Thermal Endurance
High-Tg laminates, typically those exceeding one hundred and seventy degrees Celsius, exhibit less dimensional change in the vertical axis during thermal excursions. This reduced expansion protects microvias and plated through-holes from cracking under the stresses of multi-layer lamination and manual rework. Low-Tg alternatives are less expensive but prone to via failure when exposed to multiple reflow cycles.
Assembly Suitability
Specifying the correct transition temperature ensures that boards do not warp or delaminate when subjected to the high temperatures of leadless assembly. The material’s electrical performance and mechanical strength remain stable across standard operating conditions, making it the industry benchmark for industrial electronics. Consequently, this laminate grade is widely used in multilayer boards that require robust plated through-holes.