Photonics Yield Calculator (Rolled Throughput Yield and Cost per Good Unit)
Photonics lines lose units at many small steps: component screening, assembly, active alignment, burn-in and final test. Rolled throughput yield multiplies those steps to show the real share of starts that ship, and this calculator also converts it to starts needed and cost per good unit.
Your numbers
Share of components that pass incoming inspection.
Share that pass assembly, bonding and cleaning checks.
Share that reach the coupling or beam target during active alignment.
Share that survive burn-in or environmental screening.
Share that pass final test against datasheet limits.
Average material and conversion cost sunk into each start.
Your results
Simplified model: it treats each stage as independent and charges the full cost per start to every loss. Real scrap occurs at different cost points, and rework can recover units. Use actual route costs for a financial view.
Cost per good unit vs alignment yield
Sweeps Alignment yield from 50 to 100, holding your other inputs fixed.
Stage yields from ERP and MES in one view
Optional: an expert review of pulling first-pass yield by stage and product from your existing systems.
Optional. The tool and every export work without this. No spam.
How to use the calculator
Enter the first-pass yield of each of the five stages as a percentage, using your own data from the MES or traveler records. Add the number of units started, your target number of good units and the average cost sunk into each start. The result gives the rolled throughput yield, expected good units, units lost, starts needed to hit the target and the cost per good unit. The chart varies the alignment yield, the stage that is usually the biggest lever in fiber coupled and free space assemblies, so you can see what an improvement is worth.
- Use first-pass yield per stage, excluding rework
- Use recent lots, not the best week
- Round starts needed up, since you cannot start a fraction
- Rerun after each process improvement
The formulas
Rolled throughput yield is the product of the stage yields written as fractions. Five stages at 99.2, 97.5, 92, 96 and 98.5 percent give about 84.1 percent. Good units equal starts times RTY. Starts needed equal the target divided by RTY, rounded up. Cost per good unit equals the cost of a start divided by RTY, because every good unit has to carry the cost of the starts that failed. Note that first-pass yield counts only units that pass without rework, while final yield counts units that eventually pass, so the two answer different questions.
Worked example
Using the defaults, 1,000 starts at a cost of 420 each yield about 841 good units and lose about 159. If the customer order is 800 good units, you need about 951 starts. The cost per good unit is about 499 against 420 per start, a 19 percent premium caused by yield alone. Raising alignment yield from 92 to 96 percent lifts RTY to about 87.8 percent and lowers cost per good unit to about 478. That is the type of comparison used to justify a better fixture or an automated alignment station.
Common mistakes
The usual mistake is using the final yield after rework in place of first-pass yields, which hides the cost of repeated handling. Another is applying the same cost to a unit scrapped at incoming as to one scrapped at final test, when the latter has absorbed far more labor and material. Teams also use the yield of the best shift. Finally, ignoring yield correlation, where one bad lot of components hits several stages, makes the independent model look better than reality.
Frequently Asked Questions
What is rolled throughput yield?
It is the probability a unit passes every stage first time, calculated by multiplying the first-pass yield of each stage. It is more honest than the final yield, because it counts units that needed rework as failures at the stage where they failed.
How is first-pass yield different from final yield?
First-pass yield counts only units that pass a stage without rework or retest. Final yield counts units that eventually pass after rework. A line with a high final yield but a low first-pass yield is paying hidden labor and risk.
Which stage should I improve first?
Try the chart: change each stage by a few points and compare the effect on cost per good unit. In practice the lowest yield stage and the stage with the highest cumulative cost often give the best return. Alignment and burn-in are typical targets.
Can I use it with different yields per product?
Yes, enter the yields for one product at a time. Use recent data for that product and route. Different products with different alignment tolerances can have very different yields, so do not average them.
If stage yields live in MES records, test data and ERP scrap transactions, Netray can help pull them into one view with the query shown, using on-prem models and read-only access.
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