HDI Stackup

Connection Layering

High density interconnection designs utilize thin dielectrics and microvias to increase the number of components that fit on a single circuit board. The hdi stackup organizes these layers into a specific order that allows for complex routing between fine-pitch integrated circuits. This arrangement typically includes multiple lamination cycles where new layers are added to a central core.

Density Configuration

Advanced mobile and computing devices rely on these compact structures to manage thousands of pins in a small surface area. An hdi stackup is defined by the number of sequential lamination steps, often expressed as a numerical code like 1 plus N plus 1 or 2 plus N plus 2. These codes indicate how many layers of microvias are stacked or staggered on each side of the main board core.

Using microvias instead of through-holes saves substantial space and reduces the inductance of the electrical paths.

Sequential Processing

Fabrication begins with a standard core which is then augmented with additional dielectric and copper layers through repeated plating and etching. The hdi stackup requires precise registration to ensure that the tiny holes on the outer layers align perfectly with the pads on the inner layers. Failure to maintain alignment results in open circuits or weak connections that may fail during the assembly process or in the field.

Alignment is verified through x-ray inspection at each stage of the build.

Integrated circuit rests centered on clear plastic component trays beside a spool of solder and a small cardboard package at a workstation.

Pinless Lamination Resin Rheology Panel Scaling

Registration Vector Analysis in Sequential High Density Core Lamination

Sequential core lamination registration requires X-ray target vector mapping and dynamic affine drill scaling to maintain zero breakout microvia alignment.

Two identical hybrid microelectronic subassemblies with soldered axial resistors lie on a striped metallic background in a digital illustration.

Thermal Expansion Interfacial Shear Stress Thermal Shock Testing

Quantifying Thermomechanical Shear Stress Distribution across Non Uniform Copper Density Distributions in Sequential Lamination Stackups

Copper density gradients across sequential lamination stackups drive severe shear stress during reflow, requiring thieving and balance rules to protect yield.