Shinko's 22-layer glass substrate turns the AI packaging race into a heat problem

Shinko Electric Industries has built a 22-layer glass substrate by stacking 11 copper wiring layers on each side of a glass core, and says it has suppressed "seware" - the internal cracking and delamination that glass suffers under heat - even after thermal loading ^[1][2][3]. That result moves the Korea-Japan glass substrate contest off the question of who can pattern glass and onto a narrower one: who can mass-produce glass that survives a reflow oven ^[4].

The reason anyone cares is package size. AI chips are being built by integrating multiple logic and memory dies into a single package, and conventional organic substrates warp as their area widens ^[5]. Glass is rigid and barely deforms thermally, which is why substrate makers are treating it as the next platform rather than a variant ^[6]. Shinko's fix was materials, not lithography: a polymer-based protective material applied to the substrate edges to disperse the stress that concentrates in specific areas when heat is applied ^[7].

Samsung Electro-Mechanics is coming at the same problem through structure. Last month it signed a definitive agreement to form GlaSSEM with Dongwoo Fine-Chem, the Korean subsidiary of Sumitomo Chemical, capitalized at 482.1 billion won, about $346 million, split 66% to Samsung Electro-Mechanics and 34% to Dongwoo ^[8]. The division of labour is explicit: Dongwoo brings large-area glass processing and production, Samsung Electro-Mechanics brings high-layer-count, high-density substrate design and mass-production know-how, and the venture owns glass core development through to sales ^[9]. On its second-quarter call the company said it is co-developing large-area, high-layer-count glass substrates for data centres with global big tech firms and running technology approval and sample evaluation with some customers ^[10]. It is targeting mass production two years out ^[11].

The industry read, based on disclosed results, is that Japan is a step ahead ^[12]. Shinko has both through-glass-via process technology and the multilayer insulation and copper stacking that sits on top of it ^[13]. Dai Nippon Printing built a TGV pilot line in Saitama Prefecture last December, has shipped samples since early this year, and plans full mass production in 2028 ^[14]. Samsung Electro-Mechanics' two-year target lands in the same year ^[1].

The revenue pool, for now, is small. Persistence Market Research projects the global glass core substrate market at $128.1 million this year rising to $1.036 billion in 2033, a 34.8% compound growth rate ^[15] - roughly 8.1 times over seven years ^[2]. GlaSSEM's capitalization alone is about a third of that projected 2033 market ^[3]. Nobody is committing that capital for substrate margins; they are committing it to hold position in AI packaging, next to an FC-BGA business Samsung Electro-Mechanics already mass-produces at high margin ^[16].

Two things to watch. First, whether Shinko's 22-layer result survives customer qualification rather than internal test, since thermal reliability claims tend to degrade once a substrate is populated with dies and reflowed at scale. Second, yield on large-area glass at GlaSSEM, which is the variable Dongwoo was brought in for and the one that decides whether the 2028 dates from Tokyo and Suwon mean the same thing ^[9][14][11].