Package for Decal Applications
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
A snap-assembled decal package (SADP) is a complement assembly to the decal-on-card concept. The assembly acts as a package to house the decal and chip during shipping, storage, card assembly and general handling. The package also is optimized for thermal performance, is well-suited for surface-mount technology and has a simple design with "snap together", inexpensive parts. The package was designed so that close tolerances are not necessary.
Package for Decal Applications
snap-assembled decal package (SADP) is a complement
assembly to the decal-on-card concept. The assembly acts as a
package to house the decal and chip during shipping, storage, card
assembly and general handling. The package also is optimized for
thermal performance, is well-suited for surface-mount technology and
has a simple design with "snap together", inexpensive parts. The
package was designed so that close tolerances are not necessary.
Figs. 1 and 2
show a cross section of the package. Fig. 1 shows
a "chip up" concept and Fig. 2 illustrates a "chip down" concept.
Items 1 through 9 and 12 are equivalent parts on both diagrams with
only parts ten and eleven varying between the two.
In Fig. 1,
plastic parts 11 and 10 are snapped together (or
fabricated in one piece as shown in Fig. 2); the decal 4 is laid over
part 10 such that snap prods 10A protrude through precut holes in the
decal 4. The prods act to anchor the decal and to assure proper
orientation of the decal with respect to the package and card.
Receptacle 2, in both figures, is snapped over the prods so that the
decal is sandwiched in place and protected. In Fig. 1, the optional
heatsink 12 is doped with glue in area 13 and area 8 and is snapped
through the cap, then firmly secured until dry. Adherence will take
place at the heatsink/ cap interface and the heatsink chip interface.
Optionally, if a heatsink is not utilized, part 11 is fabricated from
a one-piece, high-conductivity metal, snapped together with plastic
part 10 for electrical isolation and is glued to the chip at area 8
with a highly-conductive adhesive. In Fig. 2, a compliant support 9
is used so that adequate pressure may be maintained when gluing the
chip to the card at area 8 during package mounting. The assembled
package (parts 2 through 10 in both figures and 11 and 12 in Fig. 1)
is seated on to the card so that the prods on part 2 protrude into
the card at predetermined, pre-oriented locations. The package is
then weighted to make firm contact between the solder balls 3 and the
lands to which they will ultimately be attached. In Fig. 2, area 8
is doped with high-conductivity adhesive prior to seating. The
entire assembly is then vapor phase soldered into place. In Fig. 2,
an optional heatsink 12 is bonded to the backside of the card at area
13 from which the chip heat flux passes through the thermal vias 14.
From a rework
standpoint, the chip-up configuration must be
heated, removed from the card and its parts salvaged or discarded as
necessary. The chip-down configuration allows for cap removal and
inspection without total package removal. A full rework, however,
will require heating to de-solder area 3 and scraping at area 8 to
remove the package. An non-curing adhesive, grease or other
high-conductivity interface material may be utilized at area 8 to
avoid rework scraping for either configuration. Alte...