@kenshirriff I worked intimately with the design and analysis of these PGA packages in my early career then.

Interesting psychology anecdote – when you had a sample and you showed it to people (eg upper management) and told them explicitly do not touch the interior, they would find it irresistible and stick their finger into the inner die-attach surface and bonding pads anyway, ruining the part. It was very weird how they couldn't control themselves. Must. Jab. Finger. In. Package.