Solder Paste Inspection – Hmmm…is that really enough?

In the early days of electronics, quality manufacturing of electronic assemblies meant a steady hand with a soldering iron, sufficient flux and of course a spool of SnPb solder, all coming together with a keen eye or aided by the helpful view of a visual magnifier. Oh, the glory days of leaded capacitors, resistors, and integrated circuits, may they rest in peace!

The drive to make products smaller sparked an electronics manufacturing revolution requiring all component footprints to be reduced, initially driving passive components from leaded devices to surface mount. This allowed circuit boards to shrink substantially bringing with it a flurry of new consumer products that were more portable than ever! This, however, was only the beginning as soon afterwards, all component packages, including semiconductors, became the victims of an insatiable appetite for downsizing. As previously mentioned, leaded passives gave way to typically sized 1210/1206/0805 surface mount packages. In short order they shrunk further to 0603, then 0402, and stopping for now at “grain of salt” 01005 sized bodies!! ICs jumped into the fray moving from DIPs, TSOPs and SOICs to bottom contact devices such as QFNs/DFNs and more. ICs eventually shed their package bodies altogether moving to Chip-On-Board for products requiring the absolute smallest component footprints possible. Hearing aids are just one great example of a medical product employing the ultra-miniaturization of electronic components for the benefit of humankind!

The downside, however, of an ever-shrinking component landscape is the continuing challenge to assemble electronic circuit boards utilizing such minute devices. Thankfully such challenges drive innovation, but the advent of new automated assembly equipment capable of placing these uber-tiny components is only part of the solution. Automated component placement is of course the first requirement, but what about the unforgotten hero in this saga, “solder paste,” which after solder-reflow secures them onto the bare PCB itself?

Dispensing solder paste is by no means a glamorous part of the assembly process yet it’s likely the most critical. Not only is location of solder paste deposition important, but dispensing the correct amount is vital to ensuring a properly formed solder fillet. With reduced footprints come reduced solder stencil windows from which the paste is screened into. 0201 passives, which have been shown to be somewhat problematic in the first case, have an increased occurrence of inadequate paste being screened into the very small stencil windows. So how is this potential quality issue best mitigated? – by NPI Services assembly operation, with the implementation of solder paste inspection utilizing an advanced 3D solder paste inspection station TR7007QI, manufactured by Test Research Inc. The TR7007QI employs TRI’s latest 3D projector technology combined with advanced inspection accuracy while maintaining competitive inspection speed. Innovative SmartWarp technology automatically compensates for local board warpage and local fiducial marks help eliminate any impact of manufacturing tolerances.


Inspection of low solder paste bridge under 30μm ensures no printing defects are missed and guarantees accurate results under any conditions.

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Shadow free inspection technology is achieved through a quad/dual digital projector design coupled with intelligent software ensuring completely shadow-free inspection results and eliminating image noise issues.

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Multi-phase color lighting guarantees accurate inspection results on any PWB color and finish combination at high inspection speed. After solder inspection is complete, NPI’s assembly operation is confident that an accurate amount of solder paste is deposited at every solder pad, ensuring a reliable solder connection can be formed.

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In summary, early defect detection, 98% rework cost reduction, stable and reliable results that yield enhanced 100% defect coverage are the benefits of utilizing such state-of-the-art equipment and why your project deserves to be serviced by NPI’s competent and thorough project managers. Quality is top of mind at NPI Services and the TR7007QI is just another weapon in NPI’s assembly arsenal to hit the mark of TOTAL customer satisfaction!

Whether you’re pushing the limits of flight or space, delving into the depths of the oceans, developing state of the art medical devices or creating products that support America’s industrial revolution, the KEY to successful prototyping is to partner with a Quick Turn Manufacturing Service whose core competency is Project Management, such as NPI Services, as it’s truly the backbone of every successful prototype run.

“When Quick Turn Matters”, turn to NPI Services, a certified ITAR, AS9100, ISO 9001, ISO 13485, NIST compliant, WOSB. NPI has excelled in supporting quick turn electronic circuit card assembly requirements (qtys 1 to 1,000) of R&D engineering prototypes, preproduction runs, and low volume scheduled production since 1998. NPI’s capabilities include Engineering Design (Electronic/Mechanical), PWB Layout (Allegro/Mentor/Altium), PWB Fabrication, Component Kitting, and Full Turn-Key Assembly. Additional services include basic Functional Test, Conformal Coat, Environmental Test and Precision CNC Machining. NPI’s expertise encompasses managing and building simple to complex PCB assemblies, including Box Builds.