Quality & InspectionFree calculatorPDF, Excel, Word exportDefense Electronics

Rolled Throughput Yield Calculator for Electronics Assembly

First pass yield at each stage can look healthy while the overall line performs poorly. Rolled throughput yield multiplies the stages together and shows the share of boards that go through everything without rework.

Your numbers

Units started

boards

Paste print and SPI yield

98.5 %

First pass yield at this stage, before any rework.

Placement yield

99.2 %

Reflow and AOI yield

97.8 %

In-circuit test yield

96.5 %

Functional test yield

98 %

Average cost per rework event

Labor, retest and handling per board needing rework.

Your results

Rolled throughput yield

90.4%

Share of boards that pass every stage the first time.

Estimated rework cost

$2,166

Boards right first time

452

Boards needing rework or scrap

Lowest stage yield

96.5%

The stage most worth attacking first.

RTY here is the product of first pass yields. It assumes stages are independent and that a board reworked at any stage counts as not passing first time. Use your own measured data for each stage.

Save results:

RTY as reflow and AOI yield changes

Sweeps Reflow and AOI yield from 90 to 100, holding your other inputs fixed.

See RTY by line from live ERP and MES data

An optional review of how stage results can be rolled up automatically.

Optional. The tool and every export work without this. No spam.

How to use the calculator

Enter the number of boards started and the first pass yield for each stage, taken from your inspection or test records over a recent period. Add a typical cost per rework event. The tool returns RTY, the number of boards touched by rework or scrap and the estimated cost. Drag a slider to see how improving one stage changes the total, and read the chart for a sweep of the reflow stage.

The formula

RTY equals the product of each stage's first pass yield. With stage yields of 98.5, 99.2, 97.8, 96.5 and 98.0 percent, the product is about 90.4 percent, so nearly one board in ten is touched even though no single stage is below 96 percent. Plants that quote only the final test yield miss this hidden factory of rework.

Use first pass yield, not final yield after rework
A stage with low yield pulls RTY down the most per point
Yield differences compound across stages

Reading the result

The lowest stage yield is the first place to look, but also compare the cost impact. A small loss at the final test stage can cost more per board than a bigger loss at print, because more value has been added. For defense work the cost of rework also includes documentation, reinspection and a possible customer notification.

Common mistakes

The usual error is using yield after rework, which hides the problem. Another is mixing board-level yield with panel-level or part-level yield. Make sure each stage uses the same unit of count. Finally, avoid comparing RTY across products without noting complexity, since a dense mixed-technology board will differ from a simple one.

Frequently Asked Questions

What is the difference between FPY and RTY?

First pass yield is the share passing a single stage first time. Rolled throughput yield multiplies the stages so it shows the share that passes every stage first time. RTY is always lower than or equal to the lowest FPY.

Is RTY the same as final yield?

No. Final yield counts boards that eventually ship, including those that were reworked. RTY counts only boards that were right first time, so it exposes the rework burden that final yield hides.

How many stages should I include?

Include the stages where you record pass and fail results. Five is common for SMT lines. More stages give a more accurate picture but need data you can trust. Add or leave out stages by setting a yield to 100 percent.

How does rework affect IPC and defense requirements?

Rework and repair must follow approved procedures and may be limited by the customer or class. Frequent rework also increases risk to the assembly, so reducing it is a reliability goal as well as a cost goal.

If your MES or ERP records stage results, Netray can calculate RTY by line and by part automatically so you do not need to re-key data each month.

Talk to an Expert Explore More Free Tools

Related Tools

Quality & Inspection

More Quality & Inspection tools

See all

Back to All Tools