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Determining The Cost Of Wave Soldering Defects At Your Facility

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There are numerous increases to production costs and very serious financial losses caused directly by wave solder failures such as bridges and insufficients.

SCRAPPING:  How many boards are scrapped per week or per month?  What are the direct materials costs of the boards scrapped?  For example, a plant that scraps 7 boards per week with a direct materials cost of $41.00 and 4 boards per week at $106.00, is losing at least $711.00 per week due to scrapping alone, or about $35,550.00 annually.

TOUCH-UP:  How many boards are handled per week for the purpose of touch-up?  Better yet, combine that with how many joints are touched up, on average per board.  For example, if a plant assembles 2000 printed circuit boards per week and 5% are touched up, that means 100 boards are at issue weekly.  If there is an average of three joints in need of touch-up on each of these boards, that means that 300 joints are touched up weekly.  Using the convention that the direct cost of touch-up per joint is $4.00, the plant is losing $1,200.00 per week due to touch-up alone, or about $60,000.00 annually.

TOUCH-UP STAFF:  Another approach to assessing the cost of wave solder failures is to estimate the cost to the plant of touch-up staff.  For example, if a plant has three wave machines running every shift two shifts per day five days per week, and one touch-up person is assigned to each machine per shift, that means there are six full-time employees (three per shift) just for this purpose.  While salary ranges do vary, this plant pays its touch-up people an average annual salary of $15,000.00 (about $7.25 per hour).  That’s a total of $90,000.00 for all six of the touch-up staff.  If a full 25% of their time is spent on activity that is actually desirable, like hand soldering, then 75% of their time is spent performing touch-up.  75% of $90,000.00 is $67,500.00 annually as the direct cost of performing the touch-up function at this plant.  It’s very important to note that the real cost of touch-up is much, much higher, as this calculation does not include the cost to the plant of benefits like health care, disability insurance and retirement plans, nor the large costs to the facility for payroll taxes, social security, workman’s compensation and the like.  It does not even include the cost of floor space, or the purchase of workdesks, training costs, the investment in hand soldering equipment and the consumables that go along with it, or management energy and time.

REWORK:  On a per joint, per chip and per board basis, rework is far more expensive than even touch-up.  If the sample plant discussed here performs rework on only 1% of its boards, that means that 20 boards per week (2000 boards x 1%) are experiencing rework, or 1000 boards annually.  Using the convention that the direct cost of rework per joint is $12.00, the plant is losing $240.00 per week due to rework alone, or about $12,000.00 annually.

MORE COSTS:  The weakness in all of these calculations of financial loss is that they do not even begin to take into account the true cost of wave solder defects.  This includes the reduction in throughput, management and engineering time fighting wave solder problems, downtime, the aggravation and staff distraction that entails, and the cost of ineffective or partial attempts to improve the wave solder process.  Further, joints that have gone through touch-up and rework are weaker than joints that are wave soldered properly in the first place, thus being prone to fail sooner in the field.

FUTILITY OF INSPECTION:  One of the most obvious points is that at normal levels of solder joint inspection the inspector is at best sampling the quality of the joints on each board and, from the external appearance of the joints, assessing the chances that a satisfactory result has been achieved on all of them.  This assessment of each and every joint is obviously ridiculous; all defects can never be identified before boards leave the plant.  Therefore, the responsibility for high quality PCBs lies with the assembly process, not with inspection.

FIELD FAILURES:  This combined triple threat of touch-up, rework and inspection by sampling leads to failure at test and – most damaging of all – product failures in the field.  As an OEM you’re servicing an internal customer.  As a contract manufacturer you’re competing to retain customers and competing to attract new ones.  The damage and the cost of quality problems and field failures are incalculable to your relationship with your customers, job security and position in the marketplace.

When all factors are put together and the calculation correctly done, even a very tiny increase in yield will result in important cost savings.  Wave solder defects are very, very expensive.  Anything that will reduce the number of defects will show a cost savings.

“We thought we had tried everything possible to eliminate a bridging problem.  Using the Optimizer, in only a couple of minutes we got rid of the bridging completely by adjusting the dwell time.”

– Alfred Santilla, Wave Solder Supervisor, Universal Lighting

“Prior to investing in the Optimizer, we relied on a thermal profiler but we could not solve our skipping and insufficients problems.  In fact, those defects were not due to improper temperatures at all but instead to how our boards run through our solder waves.”

– Ricardo Soto, Process Engineering Manager, Tyco

“The Optimizer identified the root cause of chronic skipping on our boards.  We eliminated the disparallelism it measured.  This had an immediate, positive effect on board quality.”

– Aldrina Paredes, Training manager, Bose Electronics

“Your company walked in here and quickly showed my staff how to reduce defects that we’ve had to live with for a long time.”

– Dennis Herrick, Director of Operations, Condor

“Many of our voids and insufficients were assumed to be design defects.  Your training instructor used our Optimizer’s measurements to make adjustments easily and now we should never see these defects in our production again.  What a relief!”

– Enda Moran, manufacturing Manager, CEL

“Our main problem was recurring insufficients.  We made many attempts to address the problem, to no avail.  By using the Optimizer to graph our immersion depth, we identified and corrected turbulence in our main wave.  This has benefited our production process.”

– Jose Martinez, Maintenance Engineering Supervisor, Rain Bird

“The proactive nature of your methodology, which allows us to identify board defects and production issues before they happen, is critical for raising yields.”

– Luis Lopez, Operations Manager, Benchmark Electronics

“In all my years in PCB assembly, I have never seen such an enthusiastic response to a training program.  Other vendors never really improved our problems like you have.”

– Luis Velazquez, Engineering Manager, Plexus

“Using the Optimizer’s techniques every day on one board type, we saved 257 hours of touch up and rework per month.  This saved our facility over $50,000 in 12 months on this one board type alone.”

– John Lanferman, Process Characterization Group Leader, Celestica

“Your instructor solved our excessive solder and bridging by adjusting our process based on our Optimizer’s data, and showed us how we can easily do this by ourselves.”

– Gary Wirth, Production Supervisor, Honeywell

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