Benefits of using a stiffener:
Stiffeners are an inexpensive option for rigidizing pin
areas, surface mount areas, or hole patterns for
component mounting. 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 also be utilized to force a bend line in
select areas. If this is the case, Minco can provide
epoxy or silicone fillets for the edges of a FR-4
stiffener where flexing occurs.
Stiffeners reinforce solder joints and increase abrasion
Stiffeners can also provide easier handling for
soldering and automated pick-and-place. Circuits can
be soldered while still in the stiffener and the customer
can clip the circuit free after wave-soldering and
Stiffeners make parts easier to handle during
Stiffeners can be silk-screened with component
mounting locations for rapid assembly.
Stiffeners are commonly FR-4 or polyimide material,
and are usually applied with modified acrylic adhesive,
although PSA may be less expensive for small
stiffeners. Keep in mind that PSA has less resistance
than acrylic to high temperatures or solvents.
Standard FR-4 material thicknesses range from 0.003"
to 0.125". Thicknesses over 0.031" are more expensive.
In addition, the smaller a stiffener is dimensionally, the
more difficult it is to work with.
Typical thickness for polyimide stiffeners is 0.005", but
0.001", 0.002", and 0.003" are also available. Polyimide
stiffeners are less expensive than FR-4 stiffeners
because they are punched on a die instead of routed
with a drill bit. Because the polyimide stiffener lay-up
procedure is performed with pins, registration is better.
The polyimide stiffeners are trimmed along with the
cover at the final blanking procedure, which guarantees
perfect outside alignment.
Small stiffeners used to force a bend line.
Application Aid #24
Tel: (763) 571-3121 K Fax: (763) 571-0927 K www.minco.com