The document discusses manufacturing processes for creating custom injection-molded enclosures with a focus on keypads and cabling solutions to enhance reliability and reduce risks. It provides insights into material selection, prototyping, ingress protection, and design considerations for electronic assemblies. Key recommendations include the use of 3D printing for prototyping, understanding certifications, and the importance of guarding against environmental ingress.

1. Manufacturing That Eliminates Risk & Improves Reliability
Adding Keypads and Cables to Your
Injection-Molded Enclosure
08.18.23

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Agenda
 Enclosure Materials and Options
 Keypad and Cabling Considerations for Enclosures
 Ingress Protection & Shielding
 Examples and Design Solutions
 How To Get Started With Your Custom Build

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Enclosure Materials and Options

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Injection Molding with Thermoplastics
 Why Injection Molding?
 Types of Products
– Box-builds with PCBAs
– Test apparatus
– Industrial control equipment
 Most common materials
– ABS/PC/PP/PE
– Brand names and equivalent materials
• Covestro, Sabic
Top and Bottom
Enclosure Lids

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Injection Molding with Thermoplastics
 Benefits
– High strength to weight
– Low cost
– UL-recognized materials
– Flammability
 Additional considerations
– Solid modeling
– .STP file is required
– Hard tooling
– Not appropriate for rapid proto
Solid Model of
Enclosure Concept
FEA Stress
Analysis

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When to Use 3D Printed Enclosures ?
 Early and often
 Inexpensive and readily available
 Additive manufacturing process
– No hard tooling
 Common materials
– PLA filament
– PC, ABS, Nylon
For 3D printing, the cosmetics and surface finish will differ from inj molding

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Prototyping Silicone Elastomers
 Keypads, gaskets, grommets
 3D printing “rubber” is an option
– Does not behave like silicone elastomer
 Ideal for agile methodology
– Reduce risk for necessary material changes
 Consider hobbyist materials
– Under $100 in materials
– A few days’ samples can be molded
Still need to design and 3D print a mold

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Keypad Considerations for Enclosures

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Membrane Switch & Keypad Options
 Membrane Switches
– A momentary switch device in which at least one
contact is on, or made of, a flexible substrate-
ASTM
– LEDs, dome switches, and adhesive
 Silicone Rubber Keypads
– Compression-molded silicone elastomer
– 40-60 Shore A hardness
– Pair with dome switch or conductive carbon pill
 High-Reliability & Low Cost
 LEDs for Backlighting
– LED windows
– Uniform backlighting
Silicone Overlay With Circuit
LED Locations

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Keypad - How Does It Attach?
 Most keypads are affixed with only
adhesive
 Use the brand name adhesives
– 3M467, VHB
 Mechanical attachment
– Backplate and fasteners
– Thru holes
Mounting Hole
Locations

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Routing the ZIF Tail
 Not all keypads use ZIF tails
– Some use terminals + housing
 Enclosure must have recessed slot
 Keep the shape simple
– Easier to define
Route ZIF Tail Through Slot In
Enclosure

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Keypads - Backlighting Options
 LEDs are most common
– 0603 is smallest package size
 Light pipes to illuminate key features
 Light Guide Film (LGF)
Use Bi-Colored LEDs to
Achieve Dual Color
Backlighting

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Cabling Considerations for Enclosures

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Don’t Reinvent The Wheel
 What is the cable for?
– Power - 120VAC, 28VDC
– Data - USB, GPIO
– Video - HDMI, Dsub9
 Research existing off-the-shelf options
 Many have IP ratings and are UL-listed
 Cobble something together

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Typical Conductor Design Options
 “Internal wiring of appliances”
– Extremely common
– Hook-up wire
– Single-conductor
– Multi-conductor
 Flammability ratings are critical
 Shielding options
– Braided shield
– Metalized foil
– Drain wire
 Specifications
– Voltage
– Temperature
– Jacket Thickness
– Shielding
– Flammability
 Materials
– PVC
– XLPE
– PFTE
– FEP
– Silicone

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Custom Extrusion Options
 Low Cost
– Not available “off-the-shelf”
– Must meet minimum order qty
 Complete Customization
– +50 conductor cross-sections
– Mix and match wire sizes
– Vary the shielding
 Maintaining UL Compliance
– Some customization may violate UL
Non-UL Custom Extrusions Can Be Made In 3 Weeks

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Adding Overmolds to UL Cables
 Overmold will not violate UL rating
 Primary overmolding concerns
– Material compatibility
– Flammability
 Additional levels of customization
– Ruggedization
– Adding artwork or logos
House Tooling Is Readily Available With $0 NRE Expense
Epec House Tooling
M12 x 4 Pin Connector
UL2517 Wire
RJ45 Overmold
Phono Plug Overmold

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Ingress Protection & Shielding

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EMI & Shielding Considerations
 Radiated Emissions and Susceptibility
– Shielding must be added
– LVDS cables, noisy components
– PCBAs and keypads
– Application Specific
– Specifications
• UL, CSA, EN, IEC
• Federal  Consumer Product Safety Commission
• Medical  IEC 60601
• Mil-aero  MIL-STD-810, RTCA/DO-160, MIL-STD-461
Metallized
Coating for
EMI Shielding

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Ingress Protection
 Water, dust, salt
 Sealing surfaces can be added to keypads
 Additional gasketing may be necessary
 Mechanical fasteners or adhesives are used
Leak tests must be performed at system level to represent actual conditions
1mm Lip Sealing Surface
Dust Contamination On Contacts

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Understanding The Test Results
 Does ingress constitute a failure?
 Clear pass/fail criteria
– Is system performance impacted?
 Isolate the sealing surfaces
 IP67 is a difficult test to pass

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Examples and Design Solutions

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Adding Cable Strain Relief
 How will the cable pass through the wall?
 Use an off-the-shelf cord grip
 Epec can recommend standard strain
relief designs and shapes

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Adding Cable Strain Relief
 Engineer the interface
– Study the tolerances and process limitations
 Note critical dimensions and tolerances

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Custom Strain Relief for Enclosures
Size the Overmold to the
Enclosure Slot

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Keyboard with Rigid PCB - Ways to Mount
 Multilayer rigid PCBs
– Include fasteners
– Headers
 Off-the-shelf tactile switches
 Hard keycaps + silicone rubber
 Injection mold the keycaps
– Pad print markings

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Enclosure with SPST Switch & PCBA
 Use an off-the-shelf switch
 Develop way to mount switch
 Electrically connect to PCBA
 Need clearance to assemble

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Heavy Duty Power Cable & Enclosure
 Indoor use only
 Drop testing
 EMI/EMC requirements
 Operate at 220VAC 30A

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Heavy Duty Power Cable & Enclosure
 Ultrasonic welded lid
 Overmolded strain relief
 Enclosure slots for venting

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How To Get Started With Your Custom Build

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Taking the Design First Steps
 What industry and agency approvals?
 Where will this be sold?
– Globally recognized
– Additional testing required for Korea, Taiwan,
South Africa, Chile, and Argentina
 Initial certification
– Product safety
– Environmental qualification
 Establish system requirements

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Build Prototypes Before Initial Production
 It doesn’t have to be perfect
 There is a lot you can learn once built
 Use 3D Solid Modeling software
 Model every component and wire
 Partnership with one vendor helps reduce
integration challenges
Use Solid Modeling to flush out design issues
Interference Between Standoffs
and Rubber Keypad Webbing

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Strategically Use 3D Printing
 Fast, inexpensive, and everywhere
 3D printing is wildly helpful
– It’s not the Holy Grail
 How many samples and when?
– What testing is being performed?
 Understand the process limitations
Be weary of test results using 3D printed members

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Epec Inquiry Form
 When starting a project with Epec,
we ask if you could please fill out our
Inquiry Form
 This allows us to capture all the
information of your design upfront,
eliminating guess work
 Also allows us to provide you with an
accurate quote

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Technical Data & Development Budget are Required
 We require a statement of work
 Manufacturability assessment
 Performance requirements
 Where will this product be used?
 We create the engineering data
Give Us The Requirements and We Will Figure Out How To Build It

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Summary

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Summary
 Plan for several rounds of prototypes for fit checks and testing
 Leverage readily available materials
 Add customization where it makes sense
 Spend time understanding ingress protection requirements
 Invest in development PCBAs for integration and beta testing
 Ultimate goal is to build production worthy samples as fast as possible

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Our Products
Battery Packs Flex & Rigid-Flex PCBs Cable Assemblies Printed Circuit Boards
CNC Machining User Interfaces Flexible Heaters EC Fans & Motors

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Q&A
 Questions?
– Enter any questions you may have
in the control panel
– If we don’t have time to get to it, we
will reply via email

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Thank You
Check out our website at www.epectec.com.
For more information email sales@epectec.com.
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