Value Added Design Options

Stiffeners

B e n e fit s of u s in g a s tiff e n e r
•Stiffeners are an inexpensive option for rigidizing pin areas,surface mount areas, or hole patterns for component mount- ing (provided SMT components are on one side only). Surface mount areas do not always require a stiffener, depending on component size, but a stiffener is recommended and will add very little to cost or bulk.•Stiffeners can be utilized to force a bend line in selectedareas. Minco can provide epoxy fillets for the edges of the FR-4 stiffener, where flexing occurs.•Stiffeners reinforce solder joints and increase abrasion resistance.•Circuits may be attached to a stiffener pallet (multiple parts)to provide easier handling for automated pick-and-place and component soldering. Circuits can be held together for pro- cessing on the pallet, then singulated (clipped free) after wave soldering and circuit testing.•Stiffeners can be silk-screened with component mountinglocations for rapid assembly.•Stiffeners are commonly FR-4 or polyimide material. They areusually applied with modified acrylic adhesive.•Standard FR-4 material thicknesses range from 0.003"(0.08mm) to 0.125" (3.18mm). Typical thickness for polyimide stiffeners is 0.005" (125µm), but 0.001" (25µm), 0.002" (50µm), and 0.003" (75µm) are also available. Polyimide stiffeners are less expensive than FR-4 stiffeners because they are punched on a die instead of routed with a industrial drill bit. The polyimide stiff- ener lay-up procedure is performed with alignment pins, therefore, registration is better. The polyimide stiffeners are trimmed with the cover on the final blanking procedure, which guarantees perfect outside alignment.•When using multiple stiffeners, maintaining the same stiffener thickness consistent throughout the entire construc- tion will help keep costs under control. 21