The definition of HDI (High Density Intrerconnection) circuit board refers to the microvia (Microvia) with the hole diameter below 6mil, the hole ring diameter (Hole Pad) below 0.25mm, the contact density above 130 point...
The two-stage HDI board has a staggered hole structure and a laminated structure. The so-called staggered hole means that the two layers of laser holes are staggered. Why stagger it? Because the copper plating is not sat...