HDI PCB is High Density Interconnection PCB, It widely used in small BGA board as its more advantages:

• Increased interconnection density by miniaturization of holes,pads and conductors.
• Provides the possibility to have a via hole connect direct in the SMD or BGA pad.
• Improved signal integrity due to reduced tracklength.
• Improved possibility to maximization of ground connections.
• Opportunities of better thermal enhancement.
• Improved reliability by stepping up technology rather than compromising existing design rules.

(I) Type of HDI Blind via:

1. Micro via hole: 1+N+1, vias no need plating filling
2. Solid via hole: 1+N+1, vias need plating filling
3. Stagger via hole: 1+1+N+1+1, dislocation laser drilling
4. Stack via hole: 1+1+N+1+1, coordinate laser drilling
5. Skip via hole: Laser D13, isolation from L2.
6. Step via hole: 1+1+N+1+1,coordinate laser

(II) Type of drilling mode:

     1. Large Conformal mask: Conformal mask, ladder-shaped laser drilling

       2. Conformal Mask:Conformal mask, rectangle-shaped laser drilling

 3.Direct Laser Drill: No need conformal mask, rectangle-shaped laser drilling

(III) Definition of HDI type:

• 1+N+1: N is standard layer,1 is one time laser.

          Process: Drilling after lamination—>Add a copper to laminate—>Laser drilling

        E.g. : 1+4+1

• 1+1+N+1+1: N is standard layer, 1+1 is twice laser.Process: Drilling after lamination—>Add a copper to laminate—>Laser drilling—>Add a copper to laminate—>Laser drilling

• 1+1+1+N+1+1+1: N is standard layer,1+1+1 is three times laser

          Process: Drilling after lamination—>Add a copper to laminate—>Laser drilling—>Add a copper to laminate–           ->Laser drilling—>Add a copper to laminate—>Laser drilling

• Any Layer:

          Use one by one layer to laser drilling

(IV)HDI PCB design Rule

• 1+N+1

• 2+N+2 Stagger Via

• 2+N+2 Stack Via

Material of HDI: The material of HDI board contain RCC,LDPE,FR4

• RCC: Resin coated copper,it’sconstituted by coarse surface, heat-resisting, anti-oxidation copper and resin.it used in thickness>4mil. Resin of RCC has same performance of FR4 Prepreg. RCC is new material with no-glass fibre.It facilitate laser via ethching, retain multilayer board light and thin. Additional RCC has 12pm,18pm copper, it’s easy to fabricate.

• LEDPE
• FR4: It used in thickness<=4mil. always use PP 1080. HOZ, 1/3OZ is thepriority choice for HDI board.