HDI PCB Technology
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:
- Micro via hole: 1+N+1, vias no need plating filling
- Solid via hole: 1+N+1, vias need plating filling
- Stagger via hole: 1+1+N+1+1, dislocation laser drilling
- Stack via hole: 1+1+N+1+1, coordinate laser drilling
- Skip via hole: Laser D13, isolation from L2.
- 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
- 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.
- FR4: It used in thickness<=4mil. always use PP 1080. HOZ, 1/3OZ is thepriority choice for HDI board.