Lead frame for integrated circuits or the like and method of manufacture

• US 5,176,255 A
• Filed: 06/19/1991
• Issued: 01/05/1993
• Est. Priority Date: 06/19/1991
• Status: Expired due to Term

• Current Assignee: Interplex Industries, Inc. (Interplex Holdings Pte. Ltd.)
• Original Assignee: North American Specialties Corporation
• Inventors: Seidler, Jack
• Primary Examiner(s): ECHOLS, PERCY W
• Application Number:
  US07/717,681
• Time in Patent Office: 566 Days
• Field of Search: 29/827, 29/842, 29/843, 29/884, 437/220, 228/180.2, 228/212, 357/70, 206/328, 206/331, 206/330
• US Class Current: 206/724
• CPC Class Codes: H01L 21/6835 using temporarily an auxiliary support
• CPC Class Codes: H01L 23/49503 characterised by the die pad
• CPC Class Codes: H01L 23/49541 Geometry of the lead-frame
• CPC Class Codes: H01L 23/49551 characterised by bent parts
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: Y10T 29/49121 Beam lead frame or beam lead device
• CPC Class Codes: Y10T 29/49149 by metal fusion bonding
• CPC Class Codes: Y10T 29/49222 forming array of contacts or terminals

Abstract

A lead frame is provided having a number of leads to be mechanically and electrically connected to a substrate. Retaining members are also provided with the frame to hold the substrate against the leads. The retaining member is preferably disengaged from the substrate simultaneously with the trimming of the leads from the frame after connecting to the substrate.

Claims

1. A lead frame for simultaneously connecting a plurality of leads to a circuit substrate having a plurality of conductive areas, comprising:

a frame portion having an inner periphery and an outer periphery;

a plurality of conductive electrical leads having inner and outer ends, each of said leads having its outer end joined integrally with said inner periphery of said frame portion, each of said leads having its inner end free within said frame;

the positions of said inner ends relative to one another corresponding to the positions of conductive areas of said substrate relative to each other; and

retaining means joined to and integral with said frame portion for retaining said substrate in contact with said leads, said retaining means comprising at least one retaining arm integral with and extending outwardly from the outer periphery of said frame portion and in a direction away from said leads, said retaining arm being adapted to be folded over said substrate to hold said substrate in relation to said lead inner ends.

2. A lead frame as in claim 1 further comprising a solder mass held by the second end of each of said leads for soldering said second end to a conductive area of said substrate.

3. A strip of lead frames, each of said frames as in claim 1, wherein said frames are connected end to end.

4. A lead frame as in claim 1, wherein said retaining arm is formed of a resilient material such that said substrate is held against said leads with a resilient force.

5. A lead frame for simultaneously connecting a plurality of leads to a circuit substrate, comprising:

a frame portion;

a plurality of conductive electrical leads having first and second ends, each of said leads being joined integrally with said frame portion at the first ends of said leads; and

retaining means joined to said frame portion for retaining said substrate in contact with the second ends of said leads, said retaining means being integral with said frame portion;

said substrate having conductive areas, each of said leads also having its second end free, the positions of said second ends relative to one another corresponding to positions of said conductive areas relative to one another;

said retaining means being adapted to hold said substrate on said leads such that said conductive areas are juxtaposed to respective second lead ends;

said retaining means comprising at least one retaining arm extending from said frame portion, said retaining arm being adapted to be folded over said substrate to hold said substrate in relation to said leads; and

wherein a portion of said retaining arm when folded is adjacent the first end of said retaining arm when folded is adjacent the first end of at least one of said leads such that said leads and retaining arm may be severed simultaneously from said frame.

6. A lead frame as in claim 5, wherein one of said second lead ends and said conductive areas bear solder material, said retaining means being adapted to maintain the relative position of said areas with said second ends whenever said solder is in a liquid state.

7. A method for simultaneously connecting a plurality of leads to a circuit substrate having a plurality of conductive areas, comprising the steps of:

providing a frame having a plurality of leads extending inwardly of said frame, each of said leads being connected to said lead frame at a first end and having a free second end corresponding to a respective conductive area;

forming on said frame retaining means extending outwardly of said frame for holding said substrate to said leads;

providing solder on at least some of said second lead ends;

positioning said substrate on said lead frame such that said conductive surfaces are juxtaposed respectively to said second ends at the positions of said solder;

engaging said retaining means with said substrate between said leads and said retaining means to hold said substrate in said position;

heating said solder to cause it to melt; and

maintaining the relative position of said substrate and said leads by said retaining means while said solder is in a liquid state.

8. A method as in claim 7, further comprising forming said retaining means as at least one arm integral with said frame.

9. A method as in claim 8, further comprising the step of:

detaching said leads from said frame near said first ends and simultaneously detaching said retaining means from said substrate.

10. A method for simultaneously connecting a plurality of leads to a circuit substrate, comprising the steps of:

providing a frame having a plurality of leads, each of said leads being connected to said lead frame at a first end and having a free second end, said substrate having conductive areas corresponding to said free second lead ends;

forming on said frame retaining means for holding said substrate to said leads, said retaining means being arms integral with said frame;

providing solder on one of second lead ends and said conductive areas;

positioning said substrate on said lead frame such that said conductive surfaces are juxtaposed to said second ends with solder therebetween;

engaging said retaining means to hold said substrate in said position;

heating said solder to cause it to melt;

maintaining the relative position of said substrate and said leads by said retaining means while said solder is in a liquid state;

detaching said leads from said frame near said first ends and simultaneously detaching said retaining means from said substrate; and

wherein said step of engaging comprises folding said arms over said substrate.

11. A method of manufacturing a lead frame, comprising the steps of:

forming a set of leads integral with a frame, said frame having an inner periphery and an outer periphery, said leads extending inwardly of said frame from said inner periphery, said leads corresponding to conductive areas of a substrate;

forming retaining means integral with and extending outwardly from the outer periphery of said frame and in a direction away from said leads, said retaining means being adapted to retain said substrate in contact with said leads when said substrate engages said leads and said retaining means is folded over said substrate.

12. A method of joining a substrate to a lead frame, wherein said frame has inwardly extending leads corresponding to conductive areas on said substrate, said frame also having integral therewith means extending laterally outward of said frame for retaining said substrate on said leads, comprising the steps of:

placing said substrate on said leads, with solder between said conductive areas and said leads;

engaging said retaining means over said substrate to hold said leads in juxtaposition to said conductive ares with said substrate between said leads and said retaining means;

applying heat to melt said solder at a workstation;

moving said substrate and frame out of said workstation before cooling to permit insertion of another substrate and frame; and

allowing said substrate and frame to cool away from said workstation.

13. A lead frame for simultaneously connecting a plurality of leads to a circuit substrate having a plurality of conductive areas, comprising:

a frame portion having four sides, an inner periphery and an outer periphery;

a plurality of conductive electrical leads having inner and outer ends, each of said leads having its outer end joined integrally with said inner periphery of said frame portion, each of said leads having its inner end free within said frame, each side of said frame portion having at least one of said leads joined thereto;

the positions of said inner ends relative to one another corresponding to the positions of conductive areas of said substrate relative to each other; and

a retaining arm joined to an integral with one of said sides for retaining said substrate in contact with said leads, said retaining arm extending outwardly from the outer periphery of said one side of said frame portion and in a direction away from said leads, said retaining arm being adapted to be folded over said substrate to hold said substrate in relation to said lead inner ends.

14. A lead frame as in claim 13 comprising two retaining arms joined to and integral with two opposite sides of said frame portion.

15. A strip of lead frames, each of said frames as in claim 14, wherein each of said leads frames is connected to an adjacent lead frame at a side not having a retaining arm extending therefrom.