Ask the Experts
May 23, 2012 - Updated
May 15, 2012 - Originally Posted

Options to Cut Inspection Time

We are forced to correct many solder defects on the PCB bottom side (SMD glueside).The inspection and search for defects is taking too long.Our soldering waves are not new, we have tried severaltimes to prevent these defects, but with old equipment we arelimited.

Would you suggest we investigate a 3D AOI system to save inspection time? Any other suggestions?


Expert Panel Responses

Automatedinspection is amazingly fast and accurate. It enables you to get the data youneed.

Lee Levine
President, Consultant
Process Solutions Consulting Inc.
Lee Levine has been a Process Engineer and Metallurgist in the semiconductor industry for 30 years. He now operates his own company Process Solutions Consulting Inc where he consults on process issues and provides SEM/EDS and metallography services.

Thekey issue is not to decrease inspection time, but to reduce your defects thatyou are experiencing in your wave solder process. Without knowing thetypes of defects that you must repair, I would suggest that you investigate theuse of nitrogen inerting for your wave solder process. In my past andpresent experience the reduction of many types of defects, such bridging,icicles, and insufficient solder can be reduced by using an inertatmosphere. Some added benefits are dross reduction, that may be a causefor your defects and the reduction of flux required per board. Reductionin time to repair the defects, increased productivity and material costs =overall cost savings. We offer a retrofit inerting kit to introducenitrogen to the solder pot and wave area.

Gregory Arslanian
Global Segment Manager
Air Products & Chemicals, Inc.
Mr. Arslanian has been involved in electronics packaging processing and equipment since 1981 including flipchip, TAB, wirebonding and die attach. Current responsiblities include R&D, applications, marketing and customer interaction.

Without much more knowledge of your situation, my gut reactionwould be to say "no." It's almost always better to invest in preventing defectsthan in inspection and repair. That said, it may be that you have designs thatyou are not in control of (customer design) and the design may be a bigcontributor to the defects you are seeing. The first step to solving this is to figure out the root causes - why does each specific defect type happen? Is it mainly because the design isdifficult or deficient, or mainly because the soldering equipment is incapable?If the former, and you have no control over the design, then inspection may bethe only avenue. If the latter, then you can consider upgrades to the equipmentto eliminate the defects. Only after you have exhausted all resources to understand theroot causes of the defects and eliminate as many of them as possible should youconsider investments in automated inspection. Remember that the initial cost ofAOI is not the only cost. You will also be faced with the cost of programming,which may be substantial. You will also be dealing with some level of "falsepositives" which will be an ongoing cost that must be minimized by optimizationof programs. The big up-side toAOI is that it is very efficient, unlike manual inspection which willinevitably miss as many as 30% of defects. AOI also allows you to more easilylog defects into an SPC system, which can lead to much faster, easieridentification of root causes.

Fritz Byle
Process Engineer
Fritz's career in electronics manufacturing has included diverse engineering roles including PWB fabrication, thick film print & fire, SMT and wave/selective solder process engineering, and electronics materials development and marketing. Fritz's educational background is in mechanical engineering with an emphasis on materials science. Design of Experiments (DoE) techniques have been an area of independent study. Fritz has published over a dozen papers at various industry conferences.
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