SMT007 Magazine

78 SMT Magazine • April 2016 amount at the same setting. Calibration is nec- essary to guarantee this. Flux should be applied to the right spot. Placement accuracy of the robot and spray di- rection of the dropjet should ensure this. Robot accuracy is measured during a machine capa- bility analysis by dedicated laser sensors. The x and y positions are logged. The speed of the robot is controlled by the PLC. The software detects if the speed is not fol- lowing the setting or if the acceleration or de- celeration are out of bounds. The machine will generate an alarm. The robots have an accuracy that is significantly higher than the flux spread- ing. The dropjet mounted on the robot should spray the droplets straight to the bottom side of the assembly. This can be checked by spraying the flux through a device whereby a laser sensor verifies the straight flux flow (which can be in- fluenced by contamination). Frequency of this confirmation can be set into the software. Position and spreading are controlled; the next and most complex process parameter is the amount of flux per area measured in dry solids per inch. This parameter can be calculated since the spreading is known as well as the solids content of the flux. There are only two critical issues to be defined: 1. What is the solids content of the flux and is it homogenous in the flux solution? 2. When applied to the board, is the solids content on all areas identical? The solids content of a batch flux can be verified by taking a defined amount out of the barrel, evaporating the solvents and then mea- suring the mass of the solids remaining. The % of solids can then be calculated. This image shows the solids of an organic no-clean flux as applied to the test board. The spreading of this flux is clearly visible as well as the concentration of solids. Obviously, the solids consisTEnT conTrol ovEr ThE sElEcTivE soldErinG ProducTion ProcEss Figure 3: The Pareto chart shows that there are two main factors affecting flux spreading.

• Cover
• Featured Content — Pocess Engineering
• More Content
• Column — Taking the Gremlins out of Your Process
• Short — Are You Considering Further Automating the Control of Your Processes?
• Feature — In a Culture of Continuous Improvement, Processes Continually Improve
• Column — Cost vs. Cause: What is More Critical to EMS Profitability?
• Short — Producing Electronics without Semiconductors is Now a Reality
• Supply Lines Highlights
• Feature — Best-Practice Process Preparation for PCB Assembly
• Short — Manufacturing Method for Batteries with Organic Electrode Materials
• Column — To Outsource or Not to Outsource PCB Rework
• MilAero007 Highlights
• Feature — Benefits of Improving Reflow and Screen Printing Processes
• Column — The Importance of Being Earnest (Educated)
• Short — New Research Ensures Car LCDs Work in Extreme Cold, Heat
• EIN Market Highlights
• Feature Interview — Enabling Process Innovation through Test and Measurement Solutions
• Column — Selecting a Selective Soldering System, Part 1
• Feature — Achieving Repeatable, Consistent Control over the Selective Soldering Production Process
• Short — New Terahertz Source Could Strengthen Sensing Applications
• Article — Case Study: Working Smarter Through a Proprietary Systems Strategy
• Top Ten Recent Highlights from SMT007
• Events Calendar
• Advertiser Index and Masthead
• Back Cover