Technical Library | 2009-01-06 00:06:30.0
To prevent malfunctions in high-power electronics, flux residues must be removed from flip chip components prior to subsequent processes. As a result, integrating a suitable cleaning application into the manufacturing process of flip chip components is often required. Solvent based applications have re-emerged, and with that, an overall process solution is necessary.
Technical Library | 2020-11-04 17:49:45.0
OEMs and CMs designing and building electronic assemblies for high reliability applications are typically faced with a decision to clean or not to clean the assembly. If ionic residues remain on the substrate surface, potential failure mechanisms, including dendritic growth by electrochemical migration reaction and leakage current, may result. These failures have been well documented. If a decision to clean substrates is made, there are numerous cleaning process options available. For defluxing applications, the most common systems are spray-in-air, employing either batch or inline cleaning equipment and an engineered aqueous based cleaning agent. Regardless of the type of cleaning process adopted, effective cleaning of post solder residue requires chemical, thermal and mechanical energies. The chemical energy is derived from the engineered cleaning agent; the thermal energy from the increased temperature of the cleaning agent, and the mechanical energy from the pump system employed within the cleaning equipment. The pump system, which includes spray pressure, spray bar configuration and nozzle selection, is optimized for the specific process to create an efficient cleaning system. As board density has increased and component standoff heights have decreased, cleaning processes are steadily challenged. Over time, cleaning agent formulations have advanced to match new solder paste developments, spray system configurations have improved, and wash temperatures (thermal energy) have been limited to a maximum of 160ºF. In most cases, this is due to thermal limitations of the materials used to build the polymer-based cleaning equipment. Building equipment out of stainless steel is an option, but one that may be cost prohibitive. Given the maximum allowable wash temperature, difficult cleaning applications are met by increasing the wash exposure time; including reducing the conveyor speed of inline cleaners or extending wash time in batch cleaners. Although this yields effective cleaning results, process productivity may be compromised. However, high temperature resistant polymer materials, capable of withstanding a 180°F wash temperature, are now available and can be used in cleaning equipment builds. For this study, the authors explored the potential for increasing cleaning process efficiency as a result of an increase in thermal energy due to the use of higher wash temperature. The cleaning equipment selected was an inline cleaner built with high temperature resistant polymer material. For the analysis, standard substrates were used. These were populated with numerous low standoff chip cap components and soldered with both no-clean tin-lead and lead-free solder pastes. Two aqueous based cleaning agents were selected, and multiple wash temperatures and wash exposure times were evaluated. Cleanliness assessments were made through visual analysis of under-component inspection, as well as localized extraction and Ion Chromatography in accordance with current IPC standards.
Technical Library | 1999-08-27 09:27:10.0
Conformal coating is a material that is applied to electronic products or assemblies to protect them from solvents, moisture, dust or other contaminants that may cause harm. Coating also prevents dendrite growth, which may result in product failure. This paper will discuss the variables that affect the application of conformal coatings, and review in detail those variables that impact the process of selective coating of printed circuit boards.
Technical Library | 2009-07-01 09:24:25.0
During the last 5 years, the processes to remove flux residues especially for lead-free and challenging geometries have demonstrated new cleaning obstacles which have to be overcome.i A new methodology has been recently developed to further increase the propensity for successful cleaning.ii At the core of this method is the thermal identification of the residue matrix. Thermal energy changes the physical state, i.e. transitions between liquid, solid and gas phases. By taking advantage of such specific information during phase transitions, the cleaning process can be tailored to such settings, which in turn increases the cleaning success significantly.
Technical Library | 2009-09-18 14:42:37.0
In recent years, various studies have been issued on cleaning under low standoff components; most however, with incomplete information. It is essential to revisit and describe the latest challenges in the market, identifying obvious gaps in available information. Such information is crucial for potential and existing users to fully address the cleanliness levels under their respective components. With the emergence of lead-free soldering and even smaller components, new challenges have arisen including cleaning in gaps of less than 1-mil.
Technical Library | 2017-12-07 10:35:50.0
Electronics manufacturers protect their circuit boards with conformal coatings. Conformal coatings serve as a barrier from environmental hazards and internal shorts, tin whiskers, and corrosion at the board level. Within conformal coatings different material chemistries specialize in shielding from an array of hazards and can be applied by multiple methods. The most common method is atomized spray which disperses the material into a fine mist. Alternatively, non-atomized coating controls the materials' dispense shape while maintaining the original liquid form. While some applications demand atomized spray and other scenarios overlap between atomized and non-atomized coating, this paper focuses on the circumstances where materials are ideally suited for non-atomized, selective coating.
Technical Library | 2013-09-25 20:57:24.0
Conformal coating is an enabling process that allows for the ruggedizing of electronic devices and modules. As the process increases the durability of electronics that are subjected to various end-use environmental conditions, it adds value to the product. While it does add value, consumers and manufacturers expect the electronics to work when subjected to dirt, humidity, moisture, corrosive materials, and various other contaminants. This expectation results in a drive to minimize the cost of the process. The lowest cost of ownership for a conformal coating process occurs by utilizing automated selective conformal coating equipment.
Technical Library | 2008-10-01 14:02:27.0
This paper proposes an integrated system for film application process than consists of closed loop mass calibration to assure film thickness, a noncontact fast jetting process with high edge definition capable of applying films for highly selective areas and patterns. A system to obtain homogeneity of the solid-fluid mix is described and results are shared.
Technical Library | 2021-01-03 19:24:52.0
Reflow soldering is the primary method for interconnecting surface mount technology (SMT) applications. Successful implementation of this process depends on whether a low defect rate can be achieved. In general, defects often can be attributed to causes rooted in all three aspects, including materials, processes, and designs. Troubleshooting of reflow soldering requires identification and elimination of root causes. Where correcting these causes may be beyond the reach of manufacturers, further optimizing the other relevant factors becomes the next best option in order to minimize the defect rate.
Technical Library | 1999-05-09 13:05:12.0
This Technical Note discusses the construction of solder tips, the various failure modes associated with tip plating (cracking, wear, corrosion, and dewetting), how to diagnose those failure modes, and specific practices that can be taken to minimize or eliminate each one.