Page 64 - ChipScale_Mar-Apr_2021-digital

gets smaller, a stronger electrical
field is applied in between the Cu
wires, and they get more susceptible
to electrical shorting. As discussed
in prior sections, the original PID
includes chloride ion as an impurity,
because of the conventional chemical
process to synthesize epoxy-acrylate
resin. Therefore, a new synthesis
of acid-modified resin was studied
to eliminate the chloride impurity.
Fi rst, al k ylene - oxide was added
Figure 9: BHAST test coupon a) (left) overview, and b) (right) magnified image. to the phenolic resin, followed by
dehydration between the alcoholic
group and the acrylic acid. Then acid
dehydrate reacted with the molecule
to complete the reaction (Figure 8).
Unlike the epichlorohydrin-based
synthesize route, this new synthetic
route does not have any chloride
i mpu r it y. So, no ch lor ide ion is
expected in the new resin.
To va l i d a t e t h i s h y p o t h e s i s ,
ion chromatography analysis was
conducted to detect chlor ide ion
contents in the conventional acid-
Figure 10: a) (left) Cross-section SEM image, and b) (right) EDS Cu mapping image of 2µm L/S structure after mod if ie d e p oxy-a c r ylat e a nd i n
300 hours of BHAST. the new acid-modif ied resins. As

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