Impractical Stencil Aperture Designs to Enable M0201 Assembly
Effectiveness of I/O Stencil Aperture Modifications on BTC Void Reduction
Microalloyed Sn-Cu Pb-Free Solder for High Temp
Selective Reflow Rework Process
Impact of Thermal Loading on the Structural Intergrity of 3D TSV Package
Design and Fabrication of Ultra-Thin Flexible Substrate
Influence of PCB Surface Features on BGA Assembly Yield
Last Will and Testament of the BGA Void
Latest Industry News
Print These Electronic Circuits Directly Onto Skin
Compal increasingly asked to diversify production bases
Intel's margins tumble as customers shift to cheaper chips, shares slide 10%
From Foldable Phones to Stretchy Screens
6 Considerations for Integrating Sensors in Vehicles
Bill Gates Says Unhappy Customers Are Good for Your Business. Here's Why.
iPhone 12 review: Upgrade for the camera, not 5G
Apple's shifting supply chain creates boomtowns in rural Vietnam

Mysterious Drop In Production Yield

Mysterious Drop In Production Yield
A factory manufactured membrane switches. After installing exhaust fans the yield dropped. What was causing this decrease in production?
Mysteries of Science


A factory manufactured membrane switches, flat control panels found on microwave ovens and other appliances. Business was booming, and more capacity was needed. Analysis showed a bottle neck was applying the clear over coat giving the desired level of gloss. All of these coatings required several minutes in the oven.

The factory decided to try Rad-Cure, a new process for radiation curing.  Using this method the coating could be applied and cured within seconds using a small UV processor unit.

Everything seemed to be running well during two months of testing and the decision was made to set up a full UV process line. The new process was set up and running well except for one minor problem. The UV coating had a very strong acrylic odor that bothered the workers. A bigger exhaust fan on the roof eliminated the odor.

Two months later during a quality audit the coating yield which should have been higher was now only 90%, although the scrape rate was only 1%. 

What was causing this decrease in production?

Here's the rest of the story.

One operator found some of the membrane switches in the parking lot. She mentioned that every so often she heard a fluttering in the exhaust pipe.

The strong exhaust fan was occasionally sucking a membrane switch up from the conveyor and blowing it through the roof. The fix was to extend the "draw" area to pull exhaust before and after the UV processor to reduce the air velocity. The lesson is to localize the problem zone and carefully observe.


No comments have been submitted to date.

Submit A Comment

Comments are reviewed prior to posting. You must include your full name to have your comments posted. We will not post your email address.

Your Name

Your Company
Your E-mail

Your Country
Your Comments

Board Talk
Causes of Blowholes
Tips When Moving a Reflow Oven
Assembling Boards with BGAs on Both Sides
Larger Stencil Apertures and Type 4 Paste
5 vs 8-Zone Ovens
Component Moisture Question?
BGA Components and Coplanarity
How To Verify Cleanliness After Rework and Prior to Re-coating?
Ask the Experts
Initial Screen Print Test Board
HASL Surface Finish and Coplanarity
Legend Marking Discoloration
Cleanliness Testing
Stencil Cleaning Frequency
Exposed Copper Risk
Spotting After DI Water Cleaning
ESD Grounding - 1 Meg Ohm Resistor