Segment
Test and assembly: proving a chip works before shipping it
A finished wafer is a claim, not a product. Between the last process step and a part in a customer's hands sits a chain of measurement and electrical testing that decides which dies are sold, at what specification, and which are scrapped.
In one sentence
Test and assembly covers the measurement of wafers during and after fabrication, the electrical testing of dies and packaged parts, and the packaging services that turn tested dies into shippable components.
There are two different activities under this heading. Metrology and inspection happen during fabrication, feeding back to keep the process centred and to find defect sources — it is how yield improves. Electrical test happens after, and it is how good parts are separated from bad ones and sorted into performance grades.
Assembly has become strategically important in a way it was not. When packaging was placing a die in a plastic body, outsourcing it was obvious. Now that packaging determines whether a high-end product can exist, the outsourced assembly and test firms have moved from the end of the value chain toward its centre.
How this breaks down
Split by when it happens — during the process, after it, and who performs it.
- Test and assemblythis page
- Test interface hardwareThe custom hardware that makes electrical contact with a die or a package, thousands of times over.Definition page
- Metrology and testMeasuring features too small to see optically, and probing dies before they are packaged.Definition page
- Final testExercising a finished chip at speed and temperature to grade and qualify it.Definition page
- OSATThe firms that package and test other people's chips, and why their role has changed.Definition pageChokepoint
What this depends on
Technology dependencies are solved by engineering; supply dependencies are solved by building something, which takes years.
- Technology
Test coverage in the design
A chip must be designed to be testable — scan chains, built-in self-test — or the test step cannot reach most of it.
Physical design
Companies across Test and assembly
Every company named on a step below this page, ordered by how many of those steps it appears at. Compiled from the pages themselves rather than written separately, so the two cannot disagree. Not a ranking and not a recommendation.
- Chroma ATETaiwan1 step
10 more companies appear at a single step each; they are named on the pages for those steps.
How these pages are written
Each page explains one technology in plain language, states what it depends on, and names companies by what they supply at that step. Company roles are described qualitatively and deliberately carry no market shares, revenue figures or rankings — those change faster than an explainer can, and a stale number is worse than none. Ticker links point at company pages on this site and are provided for reference only.
Nothing here is investment advice, a recommendation, or a forecast. A company named on a page about a technology is not thereby a good investment, and the chokepoints described are structural facts about supply chains rather than predictions about prices. Technology moves; where a page describes something as unresolved or in development, that was true when it was written.
Plutux is not an investment adviser. Market data and AI-generated analysis are for information and education only, not investment advice. Disclaimer