Test Strategies: In-Circuit Test or Flying Probe Test?

Deciding the best test strategy for your printed circuit board assembly (PCBA) product can be both a daunting and challenging task. Does Automated Optical Inspection (AOI) catch every manufacturing defect? Is a customized In-Circuit Test (ICT), or a flexible Flying Probe Test (FPT) better suited for your specific product? Should you utilize an automated functional test solution in order to fully test how your product will perform in-field? Or, is it a combination of one or more, that will achieve the desired test coverage and product performance?

Since every test option has both strengths and weaknesses, it’s important to discuss your options with your electronic contract manufacturer by closely analyzing each test solution’s coverage, up-front and per unit costs, development lead time, and ability to accommodate design changes.

This week we’re going to look at two popular test options, In-Circuit Test (ICT) and Flying Probe Test (FPT). Both of these testing options offer similar coverage – catching most manufacturing defects that can occur, including short and open circuits, passive and active component measurements, component orientation, and basic power-up abilities. These two solutions differ on custom tooling, non-recurring engineering (NRE) charges, per-unit cost, test cycle time, and digital logic testing.

ICT is best suited to stable products with a mature design and higher volumes. Since an ICT solution requires a custom tool to be developed specifically for your PCBA, the lead time is longer and the up-front costs are higher than an FPT option. However, once the ICT tooling is developed, the test cost per unit is lower than FPT due to the test cycle time  (usually only 1 minute per board). Here at Saline Lectronics, we perform ICT on the Agilent 3070 platform.

ICT Strengths:

• Fastest test per unit
• Tests components individually
• Tests logic functionality
• Measures tolerance of components
• Finds shorts and opens
• Power-up ability to take measurements

ICT Weaknesses:

• Longest development time
• Custom tooling required
• Programming required
• Does not test connectors or non-electrical components
• Does not test components working together

FPT is best suited to products that are still in the development/prototype stage or at low production volumes. FPT is performed on an adjustable tooling rail system and requires no custom tooling. Customization for each PCBA test is done via programming using the CAD data provided by the customer. While the up-front NRE is minimal, the unit cost tends to be higher than ICT due to the longer test cycle time per board. While this varies depending on the complexity of the product, FPT can take up to 15 minutes per board. We peform FPT on one of the most advanced platforms available on the market, the Seica Pilot 4D V8.

FPT Strengths:

• No tooling required
• Minimal programming time
• Tests components individually
• Measures tolerance of components
• Finds shorts and opens
• Power-up ability to check current

FPT Weaknesses:

• May not get 100% coverage of all nets
• Does not test connectors or non-active components
• Does not test components working together

In summary, the choice between ICT and FPT will come down to  budget, monthly volumes, and design stability of your PCBA. Still struggling? Review the infographic below to help get a visual perspective on what might be ideal for your individual product.

Stay tuned for our next review of two additional testing solutions – Automated Optical Inspection (AOI) and Functional Test (FCT).

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