Nolan’s Notes: Finding Your Sweet Spot
Standard of Excellence: Delivering Excellence—A Daily Goal
Knocking Down the Bone Pile: Tin Whisker Mitigation in Aerospace Applications, Part 3
Book Excerpt: ‘The Printed Circuit Assembler's Guide to... Process Control,’ Chapter 3
September 13, 2023 | I-Connect007 Editorial TeamEstimated reading time: 2 minutes
Excerpt from: The Printed Circuit Assembler's Guide to... Process Control, Chapter 3
Process Control
As established, the SEC technique can be used as a process control tool. First published over 50 years ago, the SEC test was used in defining the ROSE test, that is IPC-TM-650 Method 2.3.25. There, the concept behind the test method is that of a cleanliness test, rather than a process control test. (We have already discussed its deficiency as a cleanliness test.)
GEN3 undertook a total rewrite of this test to render it suitable for optimised process control in order to fulfill Six Sigma requirements in electronic manufacturing4. The new method can be found in IEC 61189-5-504 but, given how few companies have acquired a copy of this test standard, we will deal with the extant deficiencies between PICT and ROSE. In addition, we will discuss the two commonly encountered equipment arrangements of SEC. These two variants are identified as closed loop and open loop and are shown schematically in Figure 3.1.
In IPC-TM-650 Method 2.3.25, the use of the terms static test and dynamic test are misleading. They came about originally to bypass patents that existed at the time. In truth, the test should be regarded as closed loop (static) and open loop (dynamic):
Closed Loop. The test solution in the test chamber is pumped via the ion exchange column, or regenerating filter, until it reaches a predetermined level of conductivity. A valve closes and isolates the ion exchange column from the circuit, and now the solution only circulates through the tank. The test specimen is introduced into the test chamber and the test solution begins to recirculate, bypassing the filter.
Open Loop. The test solution in the test chamber is pumped via the regenerating filter until it reaches a predetermined level of conductivity. The test specimen is introduced into the test chamber and the test solution begins to recirculate, through the filter.
Using the PICT test as a process control tool was discussed briefly above. An OE exercise using the SIR test will qualify a material set and produce the necessary SIR data that forms the OE. The material set in this context encompasses all the various materials: PCBs, solder masks, solder pastes, adhesives, coatings, etc. However, the SIR technique cannot be used to characterise the final product: board assembly. Products will include specific components each with their own unique materials, surface roughness and finish, and residue entrapment potential. Many components are incompatible with SIR testing as the internal connections short out the SIR measurement—hence, the use of dummy components in the standard test vehicles.
Some SIR testers advocate a snap-off area from the product that can be used for a quick SIR test. This sample board will not be representative of the product; it will not contain the same component set. Therefore, changes in the product, in particular component material details, will not be reflected in the snap-off sample. This snap-off board cannot track all changes in the product; hence, it is insensitive and unreliable in following changes in the product.
Share on:
Suggested Items
Driving Innovation: Direct Imaging vs. Conventional Exposure
07/01/2025 | Simon Khesin -- Column: Driving InnovationMy first camera used Kodak film. I even experimented with developing photos in the bathroom, though I usually dropped the film off at a Kodak center and received the prints two weeks later, only to discover that some images were out of focus or poorly framed. Today, every smartphone contains a high-quality camera capable of producing stunning images instantly.
Hands-On Demos Now Available for Apollo Seiko’s EF and AF Selective Soldering Lines
06/30/2025 | Apollo SeikoApollo Seiko, a leading innovator in soldering technology, is excited to spotlight its expanded lineup of EF and AF Series Selective Soldering Systems, now available for live demonstrations in its newly dedicated demo room.
Indium Corporation Expert to Present on Automotive and Industrial Solder Bonding Solutions at Global Electronics Association Workshop
06/26/2025 | IndiumIndium Corporation Principal Engineer, Advanced Materials, Andy Mackie, Ph.D., MSc, will deliver a technical presentation on innovative solder bonding solutions for automotive and industrial applications at the Global Electronics A
Fresh PCB Concepts: Assembly Challenges with Micro Components and Standard Solder Mask Practices
06/26/2025 | Team NCAB -- Column: Fresh PCB ConceptsMicro components have redefined what is possible in PCB design. With package sizes like 01005 and 0201 becoming more common in high-density layouts, designers are now expected to pack more performance into smaller spaces than ever before. While these advancements support miniaturization and functionality, they introduce new assembly challenges, particularly with traditional solder mask and legend application processes.
Knocking Down the Bone Pile: Tin Whisker Mitigation in Aerospace Applications, Part 3
06/25/2025 | Nash Bell -- Column: Knocking Down the Bone PileTin whiskers are slender, hair-like metallic growths that can develop on the surface of tin-plated electronic components. Typically measuring a few micrometers in diameter and growing several millimeters in length, they form through an electrochemical process influenced by environmental factors such as temperature variations, mechanical or compressive stress, and the aging of solder alloys.