Taiwan Semiconductor Manufacturing Co. has now been on the block long enough for Apple Inc. to turn to the world’s largest chip foundry firm to diversify its supply lines for its most critical device component, the AP processor chip.

But the real question now is whether TSMC ― which is still struggling to improve its yield and offer satisfactory chip characteristics ― will be able to deliver what Apple wants, industry watchers said.

Yield, which measures the percentage of chips in a finished wafer that pass all tests and function properly, is essentially a gauge of a chipmaker’s technological prowess and is seldom publicly revealed.

“It’s all about the yield and the sophistication of TSMC’s technology, which we don’t see as being up to standard yet,” said one expert, declining to be identified.

He added, however, that money is one of the main factors behind pulling up the capacity and yield.

Those who believe TSMC won’t be able to meet Apple’s demands, especially for customized chips, continued to express their doubt.

“TSMC has not been able to pull off manufacturing AP chips yet, at least not satisfactorily. And it’s still reportedly struggling with advanced 28-nanometer technology, with the yield not up to Apple’s standards,” said another industry observer, also speaking on the condition of anonymity.

Recent reports said that TSMC will be supplying the processor chips used in next year’s iPhone models that are scheduled to be launched in the second half of 2014.

Experts are skeptical, noting that AP chips also require a certain amount of memory capacity, but because TSMC has never manufactured memory chips, the Taiwanese foundry firm is likely to commit errors.

TSMC, on the other hand, claims that the 28 nm generation “represents its most energy-efficient and high-performance method of manufacturing to date.”

Experts note that Apple has, from early on, tried to diversify its supply line from other rivals ― namely TSMC, which was perceived as a potential replacement for Samsung due to its breadth and capacity.

Its technological sophistication, however, was not up to par, forcing Apple to continue relying on Samsung for some time. It paid Samsung up to $10 billion a year not just for memory chips but for displays as well.

Samsung, which in the past had been satisfied with supplying memory and logic chips for Apple’s devices, has now become the world’s largest smartphone manufacturer, beating Apple at its own game.

Despite what Apple may want ― which is most likely to reduce its dependence on the South Korean electronics giant amid an ongoing patent infringement lawsuit ― just how satisfactory a partner TSMC proves to be is a significant factor in giving Apple its way.

“For the time being, Apple will want to stabilize its chip supply lines. After it gets TSMC on the proper way so that it can manufacture the type and quality of chips to its liking, Apple will certainly choose to get rid of Samsung,” said an executive in the local semiconductor industry.

TSMC spokesperson Elizabeth Sun was unavailable for comment as of press time.

By Kim Ji-hyun  (jemmie@heraldcorp.com)