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Improved Small Outline No-Lead Packages

IP.com Disclosure Number: IPCOM000123258D
Original Publication Date: 1998-Aug-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 44K

Publishing Venue

IBM

Related People

Agranoff, N: AUTHOR [+5]

Abstract

Disclosed is a design that increases the life of the solder interconnections. The body of the SON package is essentially identical to that of a TSOP or TSOJ. (refer Figure 1) The major difference is that these latter packages have a lead-frame that extends beyond the body of the device and is then formed into a gull-wing, J-lead or some other configuration to afford some degree of compliance when the package is subsequently attached to a card. This compliance is of great importance: differential thermal expansion between the package and a card is largely accommodated by deflection of the leads rather than in deformation of the solder which, otherwise, would rapidly fatigue and fail.

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This is the abbreviated version, containing approximately 84% of the total text.

Improved Small Outline No-Lead Packages

   Disclosed is a design that increases the life of the
solder interconnections.  The body of the SON package is essentially
identical to that of a TSOP or TSOJ.  (refer Figure 1) The major
difference is that these latter packages have a lead-frame that
extends beyond the body of the device and is then formed into a
gull-wing, J-lead or some other configuration to afford some degree
of compliance when the package is subsequently attached to a card.
This compliance is of great importance: differential thermal
expansion between the package and a card is largely accommodated by
deflection of the leads rather than in deformation of the solder
which, otherwise, would rapidly fatigue and fail.

   SON packages have a lead-frame which is entirely enclosed
within the body.  The leads are molded flush with the bottom surface
to form pads that are later soldered to a card.  Although this design
allows for a very low stand-off and minimum card real estate
requirements, there is very little compliance in the package and
solder fatigue during thermal cycling can limit the application for
this type of package.  Any method reducing load on the corner most
solder joints which typically fail first, is to benefit.

   Figure 2 shows the disclosure which extends the lead and
bends it upward.  When the module is connected to a card with
solder, if forms a larger, more robust solder fillet.  This design
provides extended solder joint fatigue lif...