The global AI chip industry faces a little-known supply bottleneck—a Japanese company renowned for monosodium glutamate production, Ajinomoto, dominates the market for ABF (Ajinomoto Build-up Film), a critical insulating material required for AI chip packaging. According to reports from TrendForce and other institutions, Ajinomoto controls over 95% of the global market for ABF materials used in GPU and CPU packaging substrates. Nearly all high-performance chips, ranging from Intel CPUs to Nvidia AI accelerators, rely on its supply. As an insulating film between microcircuit layers in packaging substrates, ABF consumption surges with increasing packaging complexity: traditional PC chips require only a few layers, while Nvidia's AI accelerators like Blackwell and Rubin feature 8-16 or more packaging layers, driving ABF usage per chip up by 15-18 times. Although Ajinomoto plans to invest ¥25 billion (approximately RMB 1.2 billion) to boost capacity by 50%, doubts remain about the pace of expansion amid double-digit annual growth in AI computing demand. More critically, ABF's precision manufacturing process faces rising yield risks as layer counts increase. While new techniques like semi-additive processes enhance performance, they further exacerbate yield challenges. Constrained ABF supply stands as a key factor behind TSMC's CoWoS capacity crunch and prolonged AI chip delivery lead times. Hyperscale cloud providers have already secured Ajinomoto's capacity through upfront payments and long-term contracts, underscoring the profound impact of this hidden bottleneck on the global AI supply chain.