Glass substrates hype is ramping up

While most people focus on TGV, Metallization is the hardest step in building a glass substrate and the one actually holding back yields right now
TGV is essentially solved: the lasers are qualified, and the process is under control
$LPK CEO told me as much directly
What isn’t fully solved is filling those holes with copper while maintaining structural integrity
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Here’s how the process works
Once the vias are drilled, using TGV technology like $LPK LIDE, they’re still empty holes in glass
Metallization is the set of steps that turns them into conductive copper interconnects and plates the copper routing around them
It splits into three problems:
→ Void-free fill. You have to fill a deep, narrow hole with copper and leave no gaps inside.
→ Copper-to-glass adhesion. Copper doesn’t naturally stick to smooth glass. Without the right surface chemistry, the metal lifts off. Organic substrates don’t have this problem; glass does.
→ Surviving thermal cycling. Copper expands about five times more than glass when heated, so every power cycle stresses the glass around each via and can crack it. A substrate that passes electrical testing can still fail after a few thousand heat cycles
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Now onto the companies solving this:
→ Atotech (part of $MKSI). Its VitroCoat and CupraTech chemistries are the reference for both copper-to-glass adhesion and void-free fill
→ Okuno Chemical (private). Its TOP LUCINA GCS additives are built specifically for void-free full-fill of glass-core through-holes
→ Koto Electric (private). Its proprietary GWC process plates copper directly onto glass without roughening the surface
→ TRUMPF (private). Before a via can be filled, its sidewalls need a thin, continuous copper layer all the way down, and ordinary line-of-sight sputtering shadows out in a deep hole. TRUMPF’s HiPIMS ionizes the copper so it can be driven to the bottom, at a claimed double the deposition rate of rivals
→ SCHMID ($SHMD). Its InfinityLine covers panel plating, wet processing steps, and CMP. On plating, it competes against $AMAT and $LRCX. On CMP, it is up against $AMAT and Ebara, which own 90%+ of that market
→ The glass makers: AGC, Corning, SCHOTT, and NEG. These companies are central to the third problem. They tune the glass’s expansion toward silicon and strengthen it through ion exchange, which is what lets a filled via survive thermal cycling
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While metallization has been the toughest step, and still is, $LPK CEO told me it is also now largely solved, which is why we're seeing a timeline acceleration by the two companies achieving the best yields, which we can assume refers to Absolics and SEMCO