Technical Library | 2023-04-17 21:17:59.0
The purpose of this paper is to evaluate and compare the effectiveness and sensitivity of different cleanliness verification tests for post soldered printed circuit board assemblies (PCBAs) to provide an understanding of current industry practice for ionic contamination detection limits. Design/methodology/approach – PCBAs were subjected to different flux residue cleaning dwell times and cleanliness levels were verified with resistivity of solvent extract, critical cleanliness control (C3) test, and ion chromatography analyses to provide results capable of differentiating different sensitivity levels for each test. Findings – This study provides an understanding of current industry practice for ionic contamination detection using verification tests with different detection sensitivity levels. Some of the available cleanliness monitoring systems, particularly at critical areas of circuitry that are prone to product failure and residue entrapment, may have been overlooked. Research limitations/implications – Only Sn/Pb, clean type flux residue was evaluated. Thus, the current study was not an all encompassing project that is representative of other chemistry-based flux residues. Practical implications – The paper provides a reference that can be used to determine the most suitable and effective verification test for the detection of ionic contamination on PCBAs. Originality/value – Flux residue-related problems have long existed in the industry. The findings presented in this paper give a basic understanding to PCBA manufacturers when they are trying to choose the most suitable and effective verification test for the detection of ionic contamination on their products. Hence, the negative impact of flux residue on the respective product's long-term reliability and performance can be minimized and monitored effectively.
Technical Library | 2021-07-27 14:54:26.0
Fast forward to current time. Today, our society embraces cleanliness. We expect, demand, and evaluate cleanliness in almost every aspect of our lives. We wash our cars and pets. We maintain high cleanliness standards in our hotels and public spaces. We require cleanliness in our restaurants and hospitals. We sanitize our hands throughout the day to prevent illness. We live in a clean-centric culture. While we drive clean cars, stay in clean hotels and eat clean food, there is one part of our life where we actually abandoned cleanliness. Many of the circuit assemblies that affect almost every aspect of our daily lives are no longer required to be clean. Even though our life experience confirms the link between cleanliness and reliability, happiness, health, and safety, circuit assemblies no longer maintain that "cleanliness is next to Godliness" status. This was not always the case. There was a time when virtually all circuit assemblies were cleaned. The removal of flux and other process-related contamination was commonplace. Cleaning was as normal as soldering. As we bring history into current time, one may relate the fall of Rome and its adoption of personal hygiene and the subsequent decline in human health to the large-scale abandonment of cleanliness expectations of circuit assemblies and the subsequent reliability issues it has created. How did this happen? Has history repeated itself?
Technical Library | 2014-10-23 18:10:10.0
The functional reliability of electronic circuits determines the overall reliability of the product in which the final products are used. Market forces including more functionality in smaller components, no-clean lead-free solder technologies, competitive forces and automated assembly create process challenges. Cleanliness under the bottom terminations must be maintained in harsh environments. Residues under components can attract moisture and lead to leakage currents and the potential for electrochemical migration (...) The purpose of this research study is to evaluate innovative spray and soak methods for removing low residue flux residues and thoroughly rinsing under Bottom Termination and Leadless Components
Technical Library | 2023-02-13 18:56:42.0
This paper describes the results of an intensive whisker formation study on Pb-free assemblies with different levels of cleanliness. Thirteen types of as-received surface-mount and pin-through-hole components were cleaned and intentionally contaminated with solutions containing chloride, sulfate, bromide, and nitrate. Then the parts were assembled on double-sided boards that were also cleaned or intentionally contaminated with three fluxes having different halide contents. The assemblies were subjected to high-temperature/high-humidity testing (85_C/85% RH). Periodic examination found that contamination triggered whisker formation on both exposed tin and solder fillets. Whisker occurrence and parameters depending on the type and level of contamination are discussed. Cross-sections were used to assess the metallurgical aspects of whisker formation and the microstructural changes occurring during corrosion.
Technical Library | 2020-11-04 17:57:41.0
Residues present on circuit boards can cause leakage currents if not controlled and monitored. How "Clean is Clean" is neither easy nor cheap to determine. Most OEMs use analytical methods to assess the risk of harmful residues. The levels that can be associated with clean or dirty are typically determined based on the exposed environment where the part will be deployed. What is acceptably clean for one segment of the industry may be unacceptable for more demanding segments. As circuit assemblies increase in density, understanding cleanliness data becomes more challenging. The risk of premature failure or improper function is typically site specific. The problem is that most do not know how to measure or define cleanliness nor can they recognize process problems related to residues. A new site specific method has been designed to run performance qualifications on boards built with specific soldering materials, reflow settings and cleaning methods. High impedance measurements are performed on break off coupons designed with components geometries used to build the assembly. The test method provides a gauge of potential contamination sources coming from the assembly process that can contribute to electrochemical migration.
Technical Library | 2009-09-30 23:12:29.0
Being involved in the electronics assembly industry for more than 23 years, specifically in the field of defluxing and cleanliness testing, I have seen my share of environmental regulations. Long before the debate over lead-free alloys, there was the Montreal Protocol.
Technical Library | 2021-06-28 20:43:32.0
This book is a compilation of many articles I have published on the subjects of cleaning, reliability, and cleanliness testing. Throughout these articles, I promote a common mantra: Clean is better than dirty. Less contamination is better than more contamination. Some assemblies can tolerate more contamination; others, less.
Technical Library | 2021-04-29 01:43:34.0
Since the 1980s the electronics industry has utilized ion chromatography (IC) analysis to understand the relationship of ions, and some organics, to product reliability. From component and board fabrication to complete electronic assemblies and their end-use environment, IC analysis has been the de facto method for evaluating ionic cleanliness of electronic hardware.
Technical Library | 2018-11-20 21:33:57.0
There are several industry-accepted methods for determining the reliability of flux residues after assembly. The recommended methods of test sample preparation do not always closely mimic the thermal cycle experienced by an assembly. Therefore, extraction from actual assemblies has become a popular method of process control to assess consistency of post-reflow cleanliness. Every method of post-reflow flux residue characterization will depend on the reflow process followed to prepare the coupon.This investigation will focus on the effect of thermal conditions on the remainder of active ingredients in flux residues after assembly with no-clean solder pastes.
Technical Library | 2009-07-09 17:23:07.0
Sometimes you just cannot clean with water. Good examples of this are: circuits with batteries attached, cleaning prior to encapsulation, ionic cleanliness testing, and non-sealed or other water sensitive parts. High impedance or high voltage circuits need to be cleaned of flux residues and other soils to maximize performance and reliability and, in these types of circuits; water can be just as detrimental as fluxes. When solvent cleaning is called for, Hansen solubility parameters can help target the best solvent or solvent blend to remove the residue of interest, and prevent degradation of the assembly being manufactured. In short, using this approach can time, manufacturing cost and reduce product liability.
Golden State is a contract manufacturer that makes wire harnesses, electromechanical assemblies (box builds, subassemblies, PCBAs, kits, etc.) and services (sorting, rework, value additive manufacturing engineering)
18220 Butterfield Blvd
Morgan Hill, CA USA
Phone: 5102268155
