Flying Probe vs. Fixture Testing: Ultimate Comparison & Choosing Guide

In PCB manufacturing, testing is one of the most important steps that must take place for reliability and performance as well as customer satisfaction. In-Circuit Testing and Flying Probe Testing are two of the most common methods that offer distinct benefits in terms of board complexity, volumes of production, and cost.

Manufacturers and engineers need to understand how these two methods differ to choose the best testing method for their project. This article discusses the principles, advantages, disadvantages, and cost comparison of FPT and ICT, and offers useful information to help you decide which one meets your production needs.

What is FPT?

FPT is a fixtureless PCB testing method where the probes “fly” between the test points by means of software control. This provides an ideal solution for prototype and low-to-mid volume production because no custom fixture is required, reducing setup time and cost.

Moving probes contact different points of your PCB to check for connectivity, placement of components, and electrical performance. The software guides the probes to make the measurements of resistance, capacitance, and inductance that ensure that your circuits function. It provides the flexibility for engineers to test new designs quickly and to change test programs easily without physical retooling.

Advanced flying probe systems, such as the Seica Spa Pilot V8, can simultaneously test both sides of a PCB for faster and more reliable results. These systems also include camera-based inspections for polarity verification and advanced fault detection, including micro-shorts, high-resistance defects, and diode or IC input impedance issues.

FPT is capable of running both standard and advanced tests for:

Type of Test	What It Test
Standard	All net opens and shorts, connectivity faults; the placement of resistors and their presence in the board, capacitors, and some active devices; RLC measurements; errors in polarity.
Advanced	Small shorts and high defects, resistance, diode input defects, IC input defects, phase difference, and automatic component polarity.

In a nutshell, Flying Probe Testing offers accurate, flexible, and affordable PCB validation, especially when speed and adaptability are at the core.

Core Characteristics

Flying Probe Testing (FPT) is flexible, accurate, and requires little setup. You can simply use the PCBs to check PCB Assembly without fixtures. It’s particularly advantageous for validating prototypes and for small to mid-volume production. Through software-controlled probes, FPT ensures that all connections and components get verified properly. Test cycles may be slower than fixture-based methods. However, their flexibility and comparatively lower initial costs make them an attractive choice for many productions.

No Custom Fixtures

In contrast to ICT, FPT does not necessitate a physical test fixture, resulting in lower initial costs.

Flexibility

FPT is compatible with various designs of PCBs and is well-suited for prototypes and low to medium volume production.

Precision

The Seica Spa Pilot V8 and other advanced FPT systems can contact pads as small as 80 microns, making them suitable for HDI boards.

Test Time

Testing can take longer, often from 5 to 15 minutes per board, depending on complexity and the number of test points.

Types of Flying Probe Test Systems

Different flying probe test systems access and test your PCB in different ways. Each configuration has its own strengths depending on the complexity of the board, production volume, and footprint, etc. The right system will help you achieve speed, accuracy, and cost efficiency to meet your goals. Here, we summarize the main flying probe system types and their most suitable applications.

Class	Characterization	Advantages	Limitations	Common Uses
Single-sided	Probes are capable of reaching only one side of the PCB. Affordable and simple installation.	Perfect in simple continuity and in brief checks.	Appropriate when a low volume is to be tested. Unsuitable to test both sides at once.	Not applicable to densely populated boards or to multilayer PCBs. Single-sided boards.
Double-sided	The probes can access both sides of the board simultaneously.	Facilitates more detailed tests Quick and accurate results Supports both in-circuit and functional tests without repositioning	Higher cost and larger footprint More difficult in maintenance	Complicated and multilayer boards. Medium-high volume production.
Vertical	The setup supports the PCB vertically, depending on the model.	Saves valuable floor space	Large boards can be easily handled compared to horizontal arrangements.	Large or heavy PCBs Space-limited facilities
High-speed	The technology uses the motion control and accuracy probe to decrease the test time.	It has a significantly faster throughput. Precision was retained, and fewer board test cycles were made.	Increased maintenance and costs of capital. Demands refined software and professionals.	High-volume production Plants that have rigorous production timetables.

Each kind of system supports different requirements for PCB assembly testing. Single-sided testers, for instance, are ideal for low-volume and prototype runs. High-speed systems, meanwhile, and double-sided systems are suitable for high-volume production.

What is Fixture Testing (In-Circuit Testing)

Fixture Testing is also called In-Circuit Testing (ICT). It is a rapid, automated testing process for PCBs. Unfortunately, a “bed of nails” custom fixture is needed for testing. It checks many test points at once. It quickly detects shorts, opens, and faulty components within minutes. ICT works well if you want to produce the same PCB in high volumes. Speed and consistency are the main advantages. However, the cost of the fixture is such that ICT is not worthwhile for prototypes or low volumes.

High Throughput

ICT runs tests on all points at the same time. Each test cycle lasts about 1–2 minutes for each board.

Custom Fixtures

PCB designs need a fixture, which costs about $10,000–$20,000 for the design and build.

Comprehensive Testing

An ICT can be used to check component values, shorts, and opens. It also tests digital circuit functionality, but not complex functional tests. This is not cost-effective.

Scalability

Ideal for high-volume production where fixture costs are spread out over thousands of units.

Flying Probe vs. Fixture Testing: Cost Comparison

When assessing Flying Probe Testing (FPT) and In-Circuit Testing (ICT), which is superior, cost is often the deciding factor. FPT is cheaper to start than with ICT, while ICT is better for large-scale. Here’s a closer look at setup, operational, and maintenance cost aspects.

Setup Costs

Flying Probe Testing

FPT does not require a fixture, thus no large upfront costs. We usually create the test program from the PCB design files (Gerber, IPC-2581, ODB++). Usually, this takes a few days. The programming cost is usually $500–$2000, depending on board complexity. Although FPT (Flying Probe Test) machines can range from $100,000 to $500,000, this cost is typically absorbed by the manufacturer and not passed directly on to you.

Fixture Testing (ICT)

The costs of the ICT setup are driven by the fixture, which costs $10,000–$20,000 per design and more for complex boards. Cost of test programming can be expected to add another $1,000–$3,000, depending on the number of testpoints. Fixture fabrication and design can take away 2-4 weeks, delaying testing of new products.

Operational Costs

Flying Probe Testing

FPT tests are slower, taking around 5-15 minutes per board. Consequently, the per-unit costs rise. Also, the price range for low-volume runs is typically $5–$20. You merely need to get the probe and motor serviced from time to time. You can alter the test regime in response to design changes quickly and easily without extra hardware cost.

Fixture Testing (ICT)

Using ICT can cut down your test times to just 1 to 2 minutes per board while also reducing your per-unit costs by $1 to $5, should you have a large enough production run. Most fixtures require periodic maintenance or replacement, costing anywhere from $500 to $2,000 over time. Updates to the fixture may be needed if the PCB goes through any revision. This can take the cost up by $5,000–$15,000 per PCB revision.

Long-Term Cost Considerations

Flying Probe Testing

FPT provides you with the most cost-effective solution for prototype and low- to medium-volume (up to 1,000 units) production.

By skipping fixture costs, you save money and can quickly update tests for new designs. Still, the high costs per board make it not so feasible.

Fixture Testing (ICT)

Low volumes are often produced using electrical contacts. The initial cost of the fixture is easily justified by its low per-board cost and superior speed, especially with thousands of boards.

Advantages and Limitations

Flying Probe Testing (FPT) and In-Circuit Testing (ICT) certainly have their own strengths/trade-offs. The best choice depends on production volume, design complexity, and testing speed required. Given below are their main benefits and drawbacks.