Flex PCBs

Pricing

$10 per square inch, which includes three copies of your design. For example, a 2 square inch board would cost $20 and you’d get three copies of your board. You can order as many copies as you want, as long as they’re in multiples of three.

Turn Times

Orders will be sent to fabrication weekly, and ship within 21 calendar days of ordering.

You can get a quote, approve a design, and pay for an order at OSH Park.

Fabrication Specs

Common Specs

These specs apply to all our PCB services.

Spec Value  
Manufactured in the United States Yes  
Lead Free compatible Yes  
RoHS Complaint Yes  
High Temp Yes, 175 Tg or higher (see Material Specs)  
PCB Finish ENIG (Gold), compliant with IPC-4552  
Soldermask Type SMOBC (Soldermask Over Bare Copper), both sides  
Silkscreen Type High Res DLP, both sides  

Stackup

Layer Thickness Tolerance
Silkscreen 1mil (0.0254mm) +/-0.2mil (0.00508mm)
Soldermask 1mil (0.0254mm) +/-0.2mil (0.00508mm)
Top Copper 1oz (1.4mil, 35um)  
Polyimide Flexible Substrate 4mil (0.1016mm) +-0.4mil (0.0102mm
Bottom Copper 1oz (1.4mil, 35um)  
Soldermask 1mil (0.0254mm) +/-0.2mil (0.00508mm)
Silkscreen 1mil (0.0254mm) +/-0.2mil (0.00508mm)

Material Specs

Spec Value  
Substrate Panasonic Felios Polyimide Panasonic-Felios-F775 Datasheet
Board Thickness 4mil (0.1016mm) core  
Dielectric 3.2 at 1MHz  
Soldermask Color Clear Mask Datasheet
Minimum soldermask web 4 mil (0.1016mm)  
Maximum soldermask alignment 3mil (0.0762mm) Covers retraction, expansion, and shift
Silkscreen minimum line width 5 mil (0.127mm) (recommended minimum)
3 mil (0.0762mm) (short lines, text, graphics)
Silkscreen Datasheet
Maximum board size 16in (406.4mm) by 8in (203.2mm)  
Minimum board size 0.25in (6.35mm) by 0.25in (6.35mm)  

Copper Specifications

Spec Value  
Copper Layers 2  
Copper Weight 1oz  
Trace Spacing 6mil (0.1524mm)
Trace Width 6mil (0.1524mm)
Annular Ring 5mil (0.127mm)
Board Edge Keepout 15mil (0.381mm) recommended
(6mil 0.1524mm) required
Copper within 15mil (0.381mm) of a board edge will be fabbed, but may be damaged during shipping
Copper within 6mil (0.152mm) of a board edge will be removed prior to fabrication
Via Plating Thickness 1mil (0.0254mm)  

Drill Specifications

Spec Value  
Minimum Annular Ring 5mil (0.127mm)  
Minumum Drill Size 10mil (0.254mm)  
Minimum Slot Size 20mil (0.508mm) (drill slot only) Additional information on slots
Drill Size tolerance Max: +/- 2.5mil (0.0635mm)
Typical: +/- 1.0mil (0.0254)
 
Drill Positional Tolerance Max: 2mil (0.0508mm)
Typical: <1mil (0.0254mm)
 
Via Tenting Yes (filled hole and flat surface not guaranteed)  
Buried Via false  
Blind Via false  
Castellations Allowed, but not guaranteed Details and recommendations
Maximum Drill Size None Drill sizes above 250mil (6.35mm) will be fabbed, but with larger milling tolerances.

FAQ

Why isn’t it purple?

We tried! Coloring the mask results in it being too brittle, and it would crack when bent. Since this negatively impacts the performance and longevity of the boards, we opted for clear mask.

Why aren’t you using coverlay?

Cost, precision, and overall process robustness.

Mask can be used as-submitted, without any additional considerations. This is ideal for customers used to typical pcb processes, and doesn’t require design or library changes to switch to a Flex pcb.

Coverlay requires a number of additional design considerations to avoid manufacturing issues. Since most of our customers do not have design tools that can check for coverlay-specific issues, it would generate a lot of surprising fabrication issues and/or silent changes. We’d prefer to avoid both of these.

What’s the minimum width of a flex strip?

Currently, no official value. Currently, we recommend a minimum of 250mil (6.35mm) to avoid issues with our depanelization and shipping processes.

What’s the minimum bend radius?

This is design and application specific: We recommend reading flex design guidelines before planning any sharp bends, and accounting for each bend individually.

These table should help as a rough guideline to check your calculations. Due to the application specific nature of actual bending, we can make no warranty about correctness.

The bend radius depends on the board thickness of all layers passing through the bend. Multiplying the total thickness by the appropriate “bend ratio” then generates the expected bend radius. See our stackup for details on layer thicknesses. For simplicity, the following calculations include mask on both sides, and the number of copper layers listed.

A “static” bend is intended to be bent into shape and mounted, and is not intended to be bent from that point onward.

Copper Layers in bend Conservative static bend Agressive static bend
1 10:1 ratio, 74mil (1.8796mm) 6:1 ratio, 44mil (1.1176mm)
2 20:1 ratio, 216mil (5.4864mm) 12:1 ratio, 130mil (3.302mm)

A “dynamic” bend will have a bend/straighten cycle during normal operation. Estimating the “dynamic” bend radius is more complicated, and rough guidelines are harder to define. We recommend simply making dynamic bends as large as your application will allow to minimize wear. Sharper dynamic bends will result in decreasing the number of bends a PCB can survive prior to failure.

Copper Layers in bend Aggressive dynamic bend
1 10:1 ratio, 74mil (1.8796mm)
2 20:1 ratio, 216mil (5.4864mm)

Note, due to the use of soldermask instead of coverlay, our Flex PCBs are not well suited for use in applications where dynamic bends are used for operationally critical systems, such as medical and industrial.

What about stiffener layers?

Currently, stiffener layers are not available due to the complexity of our panels making it nearly impossible to properly fab them.

We’re investigating ways to handle this, so it may be an option later.

Will it fit <part number here> connector?

Probably! Check our stackup, and compare it to the datasheet for your component. There’s several common thicknesses connectors expect, and this is one of them.

If we’re missing information needed to verify your component, please email us at [email protected].

Seriously though? No purple?

We know. It pains us too.

Questions? Feedback? Suggestions?

Please send them to [email protected]