Buying Used Wafer Prober : Key Factors to Check Before You Purchase

I. Introduction

Wafer probers are essential machines used in semiconductor manufacturing to test wafers before they are cut into individual chips. 

Buying a used or refurbished wafer prober is a smart option for many companies. It’s cost-effective, often faster to get than new equipment, and many used models still offer excellent performance. However, choosing the wrong machine—or one in poor condition—can lead to delays, failures, and wasted money.

This article explains what you need to check before purchasing a used wafer prober, based on real-world experience in the semiconductor equipment industry.

II. Start With Your Requirements

Before looking at specific machines or brands, it's important to know exactly what your application needs. A mismatch between tool capability and your production goals can cause serious problems later.

Things to Consider:

• 1. Wafer Size
  Most probers are made for specific wafer sizes—6", 8", or 12". Make sure the tool supports the size you need.

• 2. What Kind of Chips You’re Testing
  Are you working with analog ICs, RF chips, power devices, or MEMS? Different types may require different chuck temperatures, alignment systems, or probing pressure.

• 3. Testing Environment

  • Lab or R&D use: Semi-automatic or manual models are usually fine.

  • Mass production: You’ll need full automation and cassette handling.

• 4. Tester Compatibility
  Will this prober work with your current test system? Check physical dimensions, alignment interfaces, and communication protocols (GPIB, TCP/IP, etc.).

III. Choose the Right Brand and Model

Some brands and models are better supported than others. Choosing a well-known brand with wide availability of spare parts and support options can save time and money in the future.

Comparison of Popular Brands:

IV. Check Mechanical Condition

A wafer prober needs precision movement to align the wafer with the probe card. Any damage, misalignment, or wear can lead to bad contact, test failures, or tool downtime.

Inspect These Mechanical Parts:

1. 1. Chuck Table (Wafer Holder)

   • Should be flat and clean

   • Vacuum must hold wafers securely

   • Must rotate and move accurately

2. 2. X-Y Stage & Z-Lift Mechanism

   • Must move smoothly

   • Should return to exact positions during repeat operations

   • Look for unusual noise, vibration, or slippage

3. 3. Loader and Unloader Systems

   • Make sure arms and sensors work properly

   • Check cassette handling and tray positioning

   • In auto tools, simulate multiple load/unload cycles

4. 4. Prober Arm

   • Should raise/lower accurately and consistently

   • Must align with the probe card without lateral shift

V. Inspect the Electronics and Controls

The control system manages everything: moving the wafer, operating the chuck, aligning vision, and communicating with your tester. It must be in good working order.

Key Areas to Review:

• Controller System

  • Does the system boot up reliably?

  • Is the operating system old (e.g., Windows NT)?

  • Are replacement parts for the controller available?

• Motion Controllers and I/O Boards

  • Motors should respond instantly and precisely

  • No lag, overheating, or reset errors during operation

• Communication Interfaces

  • Is the tool compatible with your tester’s protocol (e.g., GPIB or TCP/IP)?

  • Can it connect to your MES or automation system?

• Safety Systems

  • Make sure emergency stops and interlocks work

  • Check for any grounding or power supply issues

VI. Check the Vision and Alignment System

Most wafer probers use a camera and alignment system to make sure the probe card lines up correctly with the wafer pads. If the vision system is damaged, dirty, or outdated, alignment problems will happen—and those cause failed tests or probe damage.

What to Look For:

1. 1. Camera Quality

   • The image should be sharp and stable

   • No flickering, missing pixels, or delays

   • Autofocus must work correctly

2. 2. Lens and Mirrors

   • Should be clean and scratch-free

   • Foggy lenses or cracked mirrors need replacing

3. 3. Lighting

   • Backlight and coaxial light should be bright and even

   • You should be able to adjust brightness as needed

4. 4. Alignment Accuracy

   • Test if the system consistently finds the same target

   • Ask for repeat alignment demo with test wafers

VII. Check Thermal Chuck and Environmental Controls

If you're testing chips under different temperatures (cold or hot), then your wafer prober will need a thermal chuck—a platform that can heat or cool the wafer during testing.

What to Inspect:

• Temperature Range
  Can the chuck reach your required test temperatures (e.g., –40°C to +125°C)?

• Temperature Stability
  Once it reaches the target, does it hold it steady (within ±1°C)?

• Cooling/Heating Speed
  Check how long it takes to move between temperature setpoints.

• Vacuum and Seals
  Make sure the chuck holds the wafer tightly and there are no leaks.

VIII. Software and Compatibility Checks

Even if the hardware looks great, the software must also work well and be compatible with your lab or factory setup. Outdated software or missing licenses can stop you from using the prober altogether.

Key Things to Verify:

• Control Software Version
  Is it still supported? Are there any known bugs?
  Can it run on your current computers or network?

• User Interface
  Easy to use? Does it support recipe creation and alignment?
  Can it export data like bin maps?

• Communication Drivers
  Does it connect properly with your test system and MES?
  Is it using GPIB, RS232, or something else?

• Licenses and Access
  Are all needed software licenses included in the sale?
  Can you get future updates or support?

IX. Spare Parts and Service Availability

Like any machine, wafer probers need maintenance. Some older models may no longer have OEM parts available, so you need to be sure you can find what you’ll need to keep it running.

Parts to Ask About:

• Motors and belts

• PCB controller boards

• Optical components (lights, camera, mirrors)

• Thermal chuck modules

• Vacuum pumps and valves

Service Questions:

• Can the OEM still support this model?

• Are third-party repair services available in your region?

• Can you buy a spare parts kit along with the tool?

X. Final Acceptance and What to Ask Before Buying

Before making a purchase, you should have a final checklist to confirm the prober is working properly and that you’re getting everything you need.

Run These Tests Before Accepting:

• Full-axis movement and alignment test

• Auto wafer loading/unloading (if available)

• Vision system pattern recognition

• Thermal chuck ramp-up test

• Probe card docking simulation

Make Sure You Get These Documents:

• Operation and service manuals

• Software license information

• Test reports (vision, chuck, alignment)

• Spare parts list and BOM

• CE certificate or safety documents (if needed)

Suggested Purchase Terms:

• 30–90 day warranty period

• On-site training option

• Spare parts package (if possible)

• Factory Acceptance Test (FAT) or Site Acceptance Test (SAT) requirement