In-Circuit Pin Testing: An Excellent Potential Source of Value Creation

Reading time ( words)

In-circuit pin testing (ICT) is a common method of inspecting electronic assemblies to measure the effectiveness of the assembly process and to predict electrical functionality. Test probes are put in contact with dedicated test points along the surface of an assembly, checking for electrical functions such as resistance, capacitance inductance and signal timing. Some circuit assemblers use functional testing for quality assurance as a substitute for ICT. In this example, the entire assembly either works or it doesn’t.

Unlike printing paste, placing components and reflowing solder, ICT is considered a non-value added process. In fact, ICT increases the cycle time of the assembly process. If the ICT is a fail, but the circuit being tested is actually good (known as a false negative), even more time is wasted trying to determine whether or not a good assembly will function properly.

The two basic types of ICT are commonly referred to as clamshell and flying probe. The clamshell ICT simultaneously tests dozens of points on a single board. One laboratory type of clamshell ICT device uses three types of pins and four different forces. A test vehicle is placed in the clamshell fixture. The clamshell is closed, and electrical resistivity is measured at each of the test pins.

Although clamshell devices are commonly used, they are somewhat impractical for testing solder paste and flux’s ability to be probed. Typically, there can be a 15-minute cycle time per test. Pin residue build up generally occurs after hundreds of tests. Cleaning flux build-up from pins is time-consuming, but necessary to minimize false negative readings.

Clamshell fixtures are quite expensive. A customized fixture must be fabricated for each unique assembly. This cost is only justified for the testing of high-value or high-volume assemblies.

Flying probe testing is also commonly used for lower value or lower volume assemblies. Flying probes test sequences are determined by easily changeable programming inputs. Clamshell fixtures are not required. Therefore, this type of test method is more suited for high mix circuit assembly applications.

In a common laboratory flying probe procedure, one pin type and one force are used, but the test runs for a total of 4,000 strikes. Flux build-up on the pins is an important part of the test. In addition, one common laboratory test vehicle contains four different types of pads. In this example, pad A is a 40 mil (1mm) square pad without vias, pad B is a 40 mil (1mm) square pad with 13 mil (0.33mm) vias, pad C is a 28 mil (0.7mm) round pad without vias, and pad D is a 28 mil (0.77mm) round pad with 13 mil (0.33mm) vias. There are 1,000 opportunities for each pad type.

Read The Full Article Here

Editor's Note: This article originally appeared in the June 2015 issue of SMT Magazine.


Suggested Items

VJ Electronix: Automating the X-ray Inspection Process

05/04/2022 | Nolan Johnson, I-Connect007
VJ Electronix's Brennan Caissie shares the benefits of a new inspection tool that can be used on a variety of boards, with an automated system that takes the pressure off the manufacturing floor operators and can provide feedback all the way to the design process.

Dave Hillman on Living Your Passion

03/29/2022 | Barry Matties, I-Connect007
Barry Matties leads this engaging retrospective conversation with Dave Hillman, a Fellow, Materials and Process engineer at Collins Aerospace, who talks about mentorship, pandemic changes, and solder. “Soldering is soldering,” Dave says. “But how we do that keeps evolving in response to the new technologies and smaller packages.” What’s the key to his success and longevity? “Find your passion.” Here’s how he’s done it.

IPC’s Dieter Bergman Fellowship Award Presented to Bev Christian, HDPUG

03/14/2022 | Patty Goldman, I-Connect007
The Dieter Bergman IPC Fellowship Award is given to individuals who have fostered a collaborative spirit, made significant contributions to standards development, and have consistently demonstrated a commitment to global standardization efforts and the electronics industry. Bev Christian is a facilitator for the High Density Packaging User Group (HDPUG) and an adjunct associate professor in the Department of Mechanical and Mechatronics Engineering of the University of Waterloo, Waterloo, Ontario, Canada. In the past 31 years he has held positions at Nortel, BlackBerry, and CALCE; all in the areas of materials and failure analysis. Bev has never missed an IPC APEX EXPO since its inception. He is a member of 27 IPC committees and attends as time and the lack of clones allow.

Copyright © 2022 I-Connect007. All rights reserved.