February, 2020
www.us-
tech.com
Page 77
Improving PCBA Reliability Through Modern Cleaning Methods
By Emily Peck, Senior Chemist, MicroCare Corporation
signed, which require increased functionality in ever-smaller packages, manufacturers are looking for production methods that result in devices with greater reliability. The smaller, more densely populated circuit
T
boards required for this new generation of technolo- gy are making the issue of managing faults, quality and product longevity highly challenging. The use of miniaturized PCBs is making circuit board cleaning more difficult. Cleaning is essential to ensure a trou- ble-free performance. If not cleaned effectively, con- taminated PCBs can fail in the field, resulting in malfunctioning devices, extensive product recalls and costly warranty replacements. The risk of failure can be devas-
tating. Think critical applications like heart pacemakers or airbag sensors. If these do not work efficiently the conse- quences are catastrophic. They need to operate reliably every time without exception. These PCBs are also typical- ly used in products that must endure challenging conditions over a long peri- od of time. They need to work perfectly under any circumstances and with- stand harsh conditions that include persistent exposure to humidity, extreme temperatures and climates and continuous vibration. PCBs are often used in applica-
tions where replacing the assembly can be difficult or nearly impossible, such as electronics used in down-hole log- ging, space station communication sys- tems or implantable medical devices. These all require huge amounts of time, effort or expense to access, so it is critical that these PCBs function with- out fault. Some PCB failures occur inter-
mittently. It can come off the manu- facturing line in good working order only to lose some functionality or per- formance over a period of time. In some cases, the electronic product affected may be “throw-away.” A mobile phone, for example, is upgrad- ed frequently, keeping it from being such a problem. However, for long- lived devices, like a fetal monitor, an electric train motor or an elevator controller, the consequences of a fail- ure are much more of a concern.
PCB Cleaning Increases Reliability
One of the main reasons for PCB
failure is contamination. The smallest contaminant can form a barrier between contacts and parts. Dirty PCBs are susceptible to a whole host of problems, from electrochemical migra- tion and delamination to parasitic leakage, dendrite growth and shorting. Modern PCBs are small, multilay-
ered, complex systems with bottom ter- mination components such as BGAs, CSPs, MLFs, QFNs, and D-Paks. These new designs make effective cleaning a challenge. Being able to remove con- taminant under and around tightly- spaced components is difficult. Add to this the low standoff
between conductors, which can collect and trap contaminants like solder balls, and the challenge increases. In many instances, active fluxes or flux residue may stay on the PCB after reflow or after hand soldering. There can be other contaminants, such as ink and fingerprints, that require removal.
Meet the new MYPro Line™ The future just got smarter. With the MYPro Line, you can jet print perfect solder joints at the highest speeds. Ensure non-stop production with intelligent storage and proactive replenishment. And eliminate defects with 3D inspection systems that monitor and improve your process over time. It’s the best of Mycronic in a single integrated manufacturing solution. Now with more intuitive process controls, Hermes support and new dashboard and analysis software to simplify production scheduling and improve line effi ciency. All to put the future back where it belongs: in your control.
he drive towards miniaturization in the elec- tronics industry is relentless. As more advanced electronic applications are de -
One of the most common types of contamina-
tion directly impacting PCB performance is ionic residue, typically flux left behind during the man- ufacturing of a PCB, or after the soldering process. Another contamination culprit is no-clean fluxes. Today, the need to clean no-clean flux residue
is essential for long-term PCB performance and functionality. Designed to stay on the board, no- clean flux can leave behind a white residue when the salt activators in the fluxes come in contact with heat or other chemicals. This residue can cor- rode fragile circuits and enable dendrite growth. This can potentially create noise on the board
White residue is a common PCB contaminant. Continued on page 80
See at IPC APEX, Booth 1336
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