# Wafer Probe Throughput and Test Cell Capacity Calculator

> Source: https://netray.co/tools/wafer-probe-throughput-and-test-cell-capacity-calculator
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Estimates wafers per hour and wafers per week for a probe cell from dies per wafer, multi-site count, test time, index time and retest rate.

## Category

electronics

## Industry

Semiconductors

## Audience

- Test engineer
- Capacity planner
- Operations manager

## Tool

**Kind:** calculator

**Inputs:**

#### Dies per wafer

**Key:** dies

**Type:** number

**Default:** 1200

**Min:** 1

**Step:** 10

**Unit:** dies

**Help:** Gross die tested per wafer.

#### Parallel test sites

**Key:** sites

**Type:** slider

**Default:** 4

**Min:** 1

**Max:** 64

**Step:** 1

**Unit:** sites

**Help:** Dies probed in each touchdown.

#### Test time per touchdown

**Key:** test_s

**Type:** number

**Default:** 1.5

**Min:** 0

**Step:** 0.1

**Unit:** s

#### Prober index time

**Key:** index_ms

**Type:** number

**Default:** 300

**Min:** 0

**Step:** 10

**Unit:** ms

**Help:** Move time between touchdowns.

#### Wafer load and align overhead

**Key:** load_s

**Type:** number

**Default:** 45

**Min:** 0

**Step:** 1

**Unit:** s

#### Retest rate

**Key:** retest

**Type:** number

**Default:** 5

**Min:** 0

**Max:** 100

**Step:** 1

**Unit:** %

**Help:** Share of touchdowns repeated.

#### Prober and tester cells

**Key:** testers

**Type:** number

**Default:** 3

**Min:** 1

**Step:** 1

**Unit:** cells

#### Calendar hours per week

**Key:** hours

**Type:** number

**Default:** 168

**Min:** 1

**Max:** 168

**Step:** 1

**Unit:** h

#### Cell utilization

**Key:** util

**Type:** number

**Default:** 75

**Min:** 1

**Max:** 100

**Step:** 1

**Unit:** %

**Help:** Share of time spent testing after downtime, setup and idle.

**Outputs:**

#### Touchdowns per wafer

**Key:** touchdowns

**Expr:** ceil(dies / sites)

**Format:** integer

#### Seconds per wafer

**Key:** sec_per_wafer

**Expr:** touchdowns * (1 + retest / 100) * (test_s + index_ms / 1000) + load_s

**Format:** decimal

#### Wafers per hour per cell

**Key:** wafers_per_hour

**Expr:** 3600 / sec_per_wafer

**Format:** decimal

**Primary:** true

#### Wafers per week, all cells

**Key:** wafers_per_week

**Expr:** wafers_per_hour * hours * util / 100 * testers

**Format:** integer

**Primary:** true

#### Dies tested per hour per cell

**Key:** dies_per_hour

**Expr:** wafers_per_hour * dies

**Format:** integer

**Chart:**

#### Wafers per hour vs parallel sites

**Type:** line

**X:** sites

**From:** 1

**To:** 32

**Steps:** 32

**Series:**

- wafers_per_hour

**Disclaimer:** Simplified model. Real throughput also depends on probe card cleaning, edge die partial touchdowns, wafer map handling, temperature soak and prober specific timing. Measure on the real cell to calibrate.

## Content

**Intro:** This calculator estimates how many wafers a wafer probe cell can test per hour and per week, based on dies per wafer, parallel sites, test time, prober index time, load overhead and retest rate. It is built for test engineers and capacity planners who need a quick answer before spending on probe cards or testers.

**Sections:**

#### How to use it

**Body:** Enter the die count per wafer and the number of parallel sites your probe card supports. Add the test time per touchdown, the prober index time and the wafer load overhead, then set a retest rate and utilization. The result is wafers per hour per cell and total weekly capacity across all cells. The chart shows how adding sites changes throughput.

**Bullets:**

- Use measured test time from the real test program
- Keep utilization realistic after downtime and setup
- Compare multi-site options on the chart

#### The formula

**Body:** Touchdowns per wafer is dies divided by sites, rounded up. Time per wafer is touchdowns times one plus the retest fraction, times the sum of test time and index time, plus the wafer load overhead. Wafers per hour is 3600 divided by that time. Weekly capacity multiplies by the hours, utilization and number of cells.

#### Worked example

**Body:** With 1,200 dies, 4 sites, 1.5 s test time and 300 ms index, there are 300 touchdowns. With a 5 percent retest rate, the touch time is 300 times 1.05 times 1.8 s, or 567 s, plus 45 s load for 612 s per wafer. That is about 5.9 wafers per hour per cell, and roughly 2,200 wafers per week for three cells at 75 percent utilization.

#### Common mistakes

**Body:** Assuming perfect multi-site efficiency overstates throughput, because edge dies and partial touchdowns waste sites, and parallel test time can grow with site count. Another mistake is using calendar capacity as if utilization were 100 percent. Finally, do not forget extra time for temperature tests, where thermal soak can dominate.

**Cta:** If you want capacity and WIP questions answered from your ERP and test data in plain language, Netray can set that up on-prem.

**Faq:**

#### What is a touchdown in wafer probing?

**Answer:** A touchdown is one contact of the probe card with the wafer. With multi-site probing, one touchdown tests several dies in parallel, so fewer touchdowns are needed per wafer.

#### Why is edge die handling not modeled?

**Answer:** Edge dies create partial touchdowns where not all sites are used. This tool uses a simple ceiling of dies divided by sites. For precise numbers, use the prober's actual touchdown map.

#### How do I reduce wafer probe cost per die?

**Answer:** Increase parallel sites, shorten test time through test program optimization, reduce retests and improve utilization. Each affects the time per wafer shown in this model.

#### Does test time grow with more sites?

**Answer:** Often yes, a little, because tester resources are shared and some tests are serialized. Use a measured test time at the target site count rather than the single site time.

## Search terms

wafer probe throughput calculator, wafer sort capacity calculator, multi site test time calculation, prober index time, wafers per hour probe, test cell capacity planning, touchdown count per wafer

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