Non Local Strain Gradient Cohesive Zone Formulation for Microvia Corner Step Debonding
Non-local strain gradient cohesive zone modeling eliminates mesh-dependent stress singularities at microvia corner steps to accurately predict reflow debonding.
HDI Substrate
Meaning
High density printed circuit board utilizes fine lines and microvias to maximize routing density in compact electronic assemblies. The hdi substrate contains microvias drilled by lasers to connect multiple layers of resin and copper foil. This component enables the integration of high pin count semiconductor packages with small footprints.
Automated manufacturing facilities in China mass produce these boards for telecommunication and automotive control units.
Structural Microvia
Blind and buried vias replace traditional through-hole connections to conserve valuable surface area on the board. In an hdi substrate, these microvias have diameters below one hundred and fifty micrometres and are filled with electroplated copper. This structure allows designers to stack vias directly on top of each other to save space.
Build Process
Sequential lamination builds up the dielectric and conductive layers one at a time through repeated pressing and drilling cycles. Each lamination cycle adds a layer to the hdi substrate, which increases both the routing options and the manufacturing complexity. Laser drilling creates precise microvias that are subsequently metallized using chemical deposition and electroplating.
This repeated process requires precise registration to align the microvias across multiple layers.
Thermal Resistance
Solder reflow temperatures impose mechanical stress on the thin dielectric layers during assembly. An hdi substrate must withstand multiple thermal cycles without experiencing delamination or via cracking. Testing labs evaluate this thermal reliability using highly accelerated stress tests.