| Cause |
Failure condition |
Countermeasure |
D
r
i
l
l
B
i
t
D
e
s
i
g
n |
ST Type |
Increased area of contact between the drill bit
surface and hole wall raises drilling temperature. |
UC type |
| Large margin width |
Increased area of contact between the drill bit
surface and the hole wall raises drilling temperature. |
Select suitable margin length. |
| Small chip pocket |
Low swarf evacuation causes the resin to attach
to the inner copper layers in then hole wall. |
Smaller chip pocket |
M
a
n
u
f
a
c
t
u
r
e |
Repointed drill bit which has excessive diameter
wearing at the drill tip. |
Increased drilling temperature causes smear. |
Check wearing condition. Repointing must remove
correct amount to return full diameter. |
D
r
i
l
l
i
n
g
C
o
n
d
i
t
i
o
n |
Low chipload and hit count to high |
Low chipload promotes wearing, and causes smear. |
Higher chipload |
P
W
B
S
e
t
t
i
n
g |
Low glass transition temperature (Tg) |
If the drilling temperature approaches or exceeds
Tg, causes smear. |
Use Hi-Tg material. |
| Hinge number and thickness of PWB copper layers |
High cutting resistance increases drilling temperature,
causing smear. |
Decrease PWB stack heights and hit count to reduce
drill bit damage. Use double drilling method. |
E
q
u
i
p
m
e
n
t |
Non desmearing |
Remaining smear. |
Desmear treatment |
