To check the quality of PTH after the galvanic process we measure on every production panel the Cu plating thickness of several holes.
On every production panel we include test coupons. From every production batch we select some coupons and make micro sections of the PTH to check the quality of the PTH in the final PCB.
Effects that we may spot but as Eurocircuits want to avoid in production are:
- No more than 3 voids per hole in no more than 2% of the solder holes.
- The total area of voids per hole must not exceed 5% of the area of the hole.
- No voids at the pad-to-barrel interface.
- No circumferential void in excess of 90° (circumferential crack).
Acceptable on the condition that :
- The hole wall exhibits an otherwise smooth an coherent structure. (A)
- No sign of cracks around the nodule-area.(B)
- The minimum Cu-thickness is fulfilled.
Cracks are not acceptable before or after thermal stress, accept for barrel/Corner crack (D)(C) after thermal stress not extending the through plating.
Other typical cracks:
- (E) Barrel crack – not permitted before or after terminal stress.
- (F) Crack around nodule – not permitted before or after terminal stress.
- (G) Crack in inner pad or inner Cu-layer – not permitted before or after terminal stress.
- (H) Foil-crack – is permitted after thermal stress only on outer layers, provided it does not extend through plating.
Permitted if not reducing plating thickness below min
Cu burrs at the edge of the drilled hole must not have a burr height (g) of more than 50 % of the foil thickness and at most 25 micron. The burr height is understood as the dimension of the burr from foot to top (A), even if the burr is flattened (B).
Plating separation between laminate and hole wall is acceptable if extending over no more than 40 % of the PCB-thickness (t).
The separation can occur as :
- resin recession around the hole wall (C)
- hole wall pull-away (D)
Inter plane separation
Pad rotation (A)
Pink ring (B)
Glass fiber protrusion (C)
Permitted if not reducing hole diameter or Cu-thickness below minimum.
Lifted land (D)
Only allowed after thermal stress or rework simulation
- Permitted if not exceeding 100 micron (A).
- And not reducing min. conductor spacing (B).
Epoxy smear or other form of separation (d-effect) is not allowed between plated hole wall and inner pads
Permitted providing there is no evidence of separation.
Permitted providing there is no evidence of separation
Positive etch back (B)
Etch back of smear and dielectric material : max. 80 micron.
Negative etch back (C)
Smear removal and etch back of internal Cu-foil : max. 25 micron.
No heavy burned surfaces permitted