CA1292326C - Alignment of leads for ceramic integrated circuit packages - Google Patents
Alignment of leads for ceramic integrated circuit packagesInfo
- Publication number
- CA1292326C CA1292326C CA000592906A CA592906A CA1292326C CA 1292326 C CA1292326 C CA 1292326C CA 000592906 A CA000592906 A CA 000592906A CA 592906 A CA592906 A CA 592906A CA 1292326 C CA1292326 C CA 1292326C
- Authority
- CA
- Canada
- Prior art keywords
- leads
- package
- braze
- lead frame
- alignment
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
- H01L23/488—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of soldered or bonded constructions
- H01L23/498—Leads, i.e. metallisations or lead-frames on insulating substrates, e.g. chip carriers
- H01L23/49861—Lead-frames fixed on or encapsulated in insulating substrates
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/0001—Technical content checked by a classifier
- H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
Landscapes
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Lead Frames For Integrated Circuits (AREA)
Abstract
ALIGNMENT OF LEADS FOR CERAMIC INTEGRATED CIRCUIT PACKAGES
ABSTRACT OF THE DISCLOSURE
An alignment system comprising a rectangular leadframe from the interior of which extend leads to terminations arrangement for alignment and registration with the braze pads of a ceramic integrated circuit package, the alignment and registration being maintained and defined by a web bar interconnecting the leads adjacent and between those braze pads and the leadframe. The leadframe, leads and web bar are integrally formed by etching and lie in a plane.
ABSTRACT OF THE DISCLOSURE
An alignment system comprising a rectangular leadframe from the interior of which extend leads to terminations arrangement for alignment and registration with the braze pads of a ceramic integrated circuit package, the alignment and registration being maintained and defined by a web bar interconnecting the leads adjacent and between those braze pads and the leadframe. The leadframe, leads and web bar are integrally formed by etching and lie in a plane.
Description
3~i ALIGNMENT OF LEADS FOR CERAMIC INTEGRATED CIRCUIT PACKAGES
The present invention relates to the alignment o leads during brazing of these leads to connecting pads of ceramic integrated circuit (hereinafter IC) packages.
BACXGR~UND OF THE INVENTIOM
Vntil the present invention, leads to be brazed onto braze pads of leadless IC packages have been positioned by means of a leadframe, from which the leads project inwardly in the plane of the frame, over the braze pads for brazing thereto. With this cantilever arrangement of leads, a positioning tolerance of ~/-0.005 inches at the ends of the leads to be attached to the braze pads is difficult to improve upon. With fine pitch lead connections on ceramic packages, a positioning tolerance at the connection is desirably ~/-0.002 inches. One proposal to achieve this positioning tolerance is to use a removable plastic support. ~owever, such a method is relatively expensive, not totally effective and rather complex to achieve in view of the braze pad spacing on such fine lead pitch packages of only 0.025 inches center to center. In another prior ar-t proposal, a snap-off tie bar which ties all of the leads together at their very tip is proposed. At the braze pads, the tie bar extends up off the ceramic package so that it may be snapped off after brazing. Each lead is necked down at its connection with the tie har to allow the tie bar to be easily snapped off. A disadvantage of this arrangement is that the tie bar leaves only two sides of the lead e~posed for brazing onto the braze pad with the end of the lead being prevented from forming part of the brazed joint because of its connection with the tie bar. In addition this arrangement leaves "pigtails" of metal after tie bar removal leading to handling and space utilization problems. Further, the tie bar concept requires special handling for removal of the tie bar and an additional step in the production of the leadframe because of the ?2326 728~7-35 requirement that the tie bar be shaped to ex~end off of the ceramic package to facilitate its removal. The special handling for removal of the tie bar also involves additional steps.
It is known in the production of plastic IC packages, in ~hich a leadframe is used to connect leads, which e~tend through the molded plastic package to the chip housed therein, to use a dam bar interconnecting the leas in the plane of the leadframe to act as a dam to limit the flow of plastic during injection molding of the package. This is necessary as khe two molds halves are clamped together with the leads projecting through an opening between them thereby leaving gaps between the leads and the mold halves through which the plastic can extrude during molding. The dam bar prevents any significant flow of plastic resulting from this. The dam bar is then removed by punchiny operation and the small amount of extruded plastic projecting from the package is also removed.
It is an object of the present invention to provide enhanced lead alignment capable of providing the desired positioning tolerance between the ends of leads while they are brazed to braze pads of fine pitch ceramic IC packages and of improvlng dissipation of heat generated by this brazing.
SUMMARY OF TXE INVENTION
According to the present invention there is provided an intermediate product for use in ~he manufacture of a ceramic IC
component with individual fine pitch metallic leads brazed to braæe pad on a leadless ceramic IC package, which leads extend a substantial distance outwardly of said package, said product A ~ ~ ~
~ 6 72~57-35 comprising a leadless ceramic IC package having a plurality of leadless braze laid on one planar surface thereof, said braze pads being spaced 0.025 plus/minus 0.002 inch center to center, a planar self-supporting metallic lead frame, a plurality of fine metallic leads extending inwardly of said lead irame to lead terminations aligned with and brazed to said braze pads, a web bar interconnecting said fine leads adjacent to, and within about 0.06 inches of, their terminations and spaced outwardly of said IC
package, and means for aligning said lead fram~ ~ith respect to a punch tool to be used for severing said web from said leads and said leads from said lead frame.
The present invention enhances the positioning tolerance of the ends of leads for brazing to braze pads of fine pitch ceramic IC packages. It permits improved alignment of these leads with respect to the package and with respect to adjacent leads.
This improved alignment of the leads at the braze points translates to improved true-positioning or lead registration at the printed circuit board interface upon surface mounting of the finished device. Additionally, the web bar arrangement increases dissipation of heat generated by the brazing process and reduces warpage during cooling. The invention preferably provides these enhancements using a planar leadframe construction in which the frame, leads and the web bar are integral. This provides an economical 5 produced, simple, extremely effective arrangement.
BRIEF DESCRIPTION OY T~ DRAWINGS
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a plan view of a leadframe with the web ~bar of the present invention shown after brazing to a fine lead pitch ceramic IC package;
Figure 2 is an enlarged portion of one corner of the leadframe illustrated in Figure l; and Figure 3 is a sec-tion along section line 3-3 shown in Figure 2.
DESCRIPTION OF T~E PREFERRED EMBODIMENT
With reference first to the drawings, a fine lead pitch ceramic IC package 1, square in plan, carries on its 20face 2, a row of braze pads 3 adjacent each of its four edges. The braze pads are evenly spaced apart with their centers spaced by 0.025 inches plus/minus 0.002 inches.
Within the package 1 of the braze pads are connected as appropriate to the IC 9 housed therein, by connections 8 25(see Figure 3). A plurality of leads 4 terminate at and are brazed to the braze pads with each lead brazed on both of its sides and its end at its termination. The leads 4 associated with each of the four sides of the package 1 are parallel to one another, lie in a plane and extend 30normal to kheir associated side of the package. The leads are preferably a gold or nickel plated iron-nickel-cobalt alloy such as that sold under the trademark XOVAR by Westinghouse Electric Corporation. The leads are supported at their outer ends, the ends remote from those 35brazed to the braze pads, by a leadframe 5 lying in the plane o~ the lead 5. This frame 5 connects all of the lf~2326 leads from all four sides of the package 1 together to provide alignment of the leads and support during assembly including brazing to the braze pads. Adjacent the four sides of the package 1 a web bar 6 lying in the plane of 5 the leads 4 and the leadframe 5 interconnects all of the leads. Tl~e web bar comprises four portions, one for each side of the package with the four web bar portions being jointed at the corners of the package 1. The leadframe 5, leads 4 and web bar 6 are integral and are typically lOproduced by etching as an entirely separate step from the ~ceramic package producing process. The manner of producing this integral structure will be well known to those skilled in the art.
The leadframe is spaced from the braze pads by 15approximately 0.285 inches while the web bar 6 is spaced from the brazed points by approximately 0.060 inches thereby to provide an improvement in alignment and registration of the inner terminal ends of the leads 4 with respect to the braze pads.
Preparatory to the brazing operation, the integral structure comprising the leads 4, leadframe 5 and web bar 6 are brought into alignment and registration with the braze pads and held in that alignment while the inner terminal ends of the leads 4 are brazed onto the braze 25pads of the ceramic package 1 a-t a furnace temperature of bet~een 800 and 1,000 degrees C.
After brazing the web bars are mechanically removed using a punch trim tool. The trim tool is aligned with the leads for accurate removal of the web bar by means of 30tooling holes 7 in the leadframe 5. Subsequently, the leads are trimmed from the leadframe and deformed, from the plane they line in during assembly, into a gull-wing form to facilitate surface mounting of the package 1 onto a print~d circuit board.
The surface mounting of the ceramic IC package is facilitated by the accurate alignment and registration of Z~326 the formed leads relative to lands on the printed circuit boards for soldering thereto. Accurate placement of the leads to the land's provides increased surface mount yields, and consequently increased yields of the printed circuit board assemblies. Tight tolerancing oE the leads in relation to one another (true-positioning) as is provided by the present invention after forming of the leads is imperative to meet the alignment and registration requirements of printed circuit boards.
Prior to the present invention with its utilization of the web bar 6, the relationship with one lead to the next lead was specified as 0.25 inches ~/- 0.005 inches. With the web bar 6 disposed approximately 0.60 inches away from the braze pads, a highly desirable and tighter tolerance 15 o~ 0.025 inches ~- 0.002 inches is possible. The improved lead positioning at the brazed point translates to tighter tolerances at the end of the lead when the outer web bar is removed and the leads are formed for attachment to the printed circuit board.
The present invention relates to the alignment o leads during brazing of these leads to connecting pads of ceramic integrated circuit (hereinafter IC) packages.
BACXGR~UND OF THE INVENTIOM
Vntil the present invention, leads to be brazed onto braze pads of leadless IC packages have been positioned by means of a leadframe, from which the leads project inwardly in the plane of the frame, over the braze pads for brazing thereto. With this cantilever arrangement of leads, a positioning tolerance of ~/-0.005 inches at the ends of the leads to be attached to the braze pads is difficult to improve upon. With fine pitch lead connections on ceramic packages, a positioning tolerance at the connection is desirably ~/-0.002 inches. One proposal to achieve this positioning tolerance is to use a removable plastic support. ~owever, such a method is relatively expensive, not totally effective and rather complex to achieve in view of the braze pad spacing on such fine lead pitch packages of only 0.025 inches center to center. In another prior ar-t proposal, a snap-off tie bar which ties all of the leads together at their very tip is proposed. At the braze pads, the tie bar extends up off the ceramic package so that it may be snapped off after brazing. Each lead is necked down at its connection with the tie har to allow the tie bar to be easily snapped off. A disadvantage of this arrangement is that the tie bar leaves only two sides of the lead e~posed for brazing onto the braze pad with the end of the lead being prevented from forming part of the brazed joint because of its connection with the tie bar. In addition this arrangement leaves "pigtails" of metal after tie bar removal leading to handling and space utilization problems. Further, the tie bar concept requires special handling for removal of the tie bar and an additional step in the production of the leadframe because of the ?2326 728~7-35 requirement that the tie bar be shaped to ex~end off of the ceramic package to facilitate its removal. The special handling for removal of the tie bar also involves additional steps.
It is known in the production of plastic IC packages, in ~hich a leadframe is used to connect leads, which e~tend through the molded plastic package to the chip housed therein, to use a dam bar interconnecting the leas in the plane of the leadframe to act as a dam to limit the flow of plastic during injection molding of the package. This is necessary as khe two molds halves are clamped together with the leads projecting through an opening between them thereby leaving gaps between the leads and the mold halves through which the plastic can extrude during molding. The dam bar prevents any significant flow of plastic resulting from this. The dam bar is then removed by punchiny operation and the small amount of extruded plastic projecting from the package is also removed.
It is an object of the present invention to provide enhanced lead alignment capable of providing the desired positioning tolerance between the ends of leads while they are brazed to braze pads of fine pitch ceramic IC packages and of improvlng dissipation of heat generated by this brazing.
SUMMARY OF TXE INVENTION
According to the present invention there is provided an intermediate product for use in ~he manufacture of a ceramic IC
component with individual fine pitch metallic leads brazed to braæe pad on a leadless ceramic IC package, which leads extend a substantial distance outwardly of said package, said product A ~ ~ ~
~ 6 72~57-35 comprising a leadless ceramic IC package having a plurality of leadless braze laid on one planar surface thereof, said braze pads being spaced 0.025 plus/minus 0.002 inch center to center, a planar self-supporting metallic lead frame, a plurality of fine metallic leads extending inwardly of said lead irame to lead terminations aligned with and brazed to said braze pads, a web bar interconnecting said fine leads adjacent to, and within about 0.06 inches of, their terminations and spaced outwardly of said IC
package, and means for aligning said lead fram~ ~ith respect to a punch tool to be used for severing said web from said leads and said leads from said lead frame.
The present invention enhances the positioning tolerance of the ends of leads for brazing to braze pads of fine pitch ceramic IC packages. It permits improved alignment of these leads with respect to the package and with respect to adjacent leads.
This improved alignment of the leads at the braze points translates to improved true-positioning or lead registration at the printed circuit board interface upon surface mounting of the finished device. Additionally, the web bar arrangement increases dissipation of heat generated by the brazing process and reduces warpage during cooling. The invention preferably provides these enhancements using a planar leadframe construction in which the frame, leads and the web bar are integral. This provides an economical 5 produced, simple, extremely effective arrangement.
BRIEF DESCRIPTION OY T~ DRAWINGS
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a plan view of a leadframe with the web ~bar of the present invention shown after brazing to a fine lead pitch ceramic IC package;
Figure 2 is an enlarged portion of one corner of the leadframe illustrated in Figure l; and Figure 3 is a sec-tion along section line 3-3 shown in Figure 2.
DESCRIPTION OF T~E PREFERRED EMBODIMENT
With reference first to the drawings, a fine lead pitch ceramic IC package 1, square in plan, carries on its 20face 2, a row of braze pads 3 adjacent each of its four edges. The braze pads are evenly spaced apart with their centers spaced by 0.025 inches plus/minus 0.002 inches.
Within the package 1 of the braze pads are connected as appropriate to the IC 9 housed therein, by connections 8 25(see Figure 3). A plurality of leads 4 terminate at and are brazed to the braze pads with each lead brazed on both of its sides and its end at its termination. The leads 4 associated with each of the four sides of the package 1 are parallel to one another, lie in a plane and extend 30normal to kheir associated side of the package. The leads are preferably a gold or nickel plated iron-nickel-cobalt alloy such as that sold under the trademark XOVAR by Westinghouse Electric Corporation. The leads are supported at their outer ends, the ends remote from those 35brazed to the braze pads, by a leadframe 5 lying in the plane o~ the lead 5. This frame 5 connects all of the lf~2326 leads from all four sides of the package 1 together to provide alignment of the leads and support during assembly including brazing to the braze pads. Adjacent the four sides of the package 1 a web bar 6 lying in the plane of 5 the leads 4 and the leadframe 5 interconnects all of the leads. Tl~e web bar comprises four portions, one for each side of the package with the four web bar portions being jointed at the corners of the package 1. The leadframe 5, leads 4 and web bar 6 are integral and are typically lOproduced by etching as an entirely separate step from the ~ceramic package producing process. The manner of producing this integral structure will be well known to those skilled in the art.
The leadframe is spaced from the braze pads by 15approximately 0.285 inches while the web bar 6 is spaced from the brazed points by approximately 0.060 inches thereby to provide an improvement in alignment and registration of the inner terminal ends of the leads 4 with respect to the braze pads.
Preparatory to the brazing operation, the integral structure comprising the leads 4, leadframe 5 and web bar 6 are brought into alignment and registration with the braze pads and held in that alignment while the inner terminal ends of the leads 4 are brazed onto the braze 25pads of the ceramic package 1 a-t a furnace temperature of bet~een 800 and 1,000 degrees C.
After brazing the web bars are mechanically removed using a punch trim tool. The trim tool is aligned with the leads for accurate removal of the web bar by means of 30tooling holes 7 in the leadframe 5. Subsequently, the leads are trimmed from the leadframe and deformed, from the plane they line in during assembly, into a gull-wing form to facilitate surface mounting of the package 1 onto a print~d circuit board.
The surface mounting of the ceramic IC package is facilitated by the accurate alignment and registration of Z~326 the formed leads relative to lands on the printed circuit boards for soldering thereto. Accurate placement of the leads to the land's provides increased surface mount yields, and consequently increased yields of the printed circuit board assemblies. Tight tolerancing oE the leads in relation to one another (true-positioning) as is provided by the present invention after forming of the leads is imperative to meet the alignment and registration requirements of printed circuit boards.
Prior to the present invention with its utilization of the web bar 6, the relationship with one lead to the next lead was specified as 0.25 inches ~/- 0.005 inches. With the web bar 6 disposed approximately 0.60 inches away from the braze pads, a highly desirable and tighter tolerance 15 o~ 0.025 inches ~- 0.002 inches is possible. The improved lead positioning at the brazed point translates to tighter tolerances at the end of the lead when the outer web bar is removed and the leads are formed for attachment to the printed circuit board.
Claims (3)
1. An intermediate product for use in the manufacture of a ceramic IC component with individual fine pitch metallic leads brazed to braze pad on a leadless ceramic IC package, which leads extend a substantial distance outwardly of said package, said product comprising a leadless ceramic IC package having a plurality of leadless braze laid on one planar surface thereof, said braze pads being spaced 0.025 plus/minus 0.002 inch center to center, a planar self-supporting metallic lead frame, a plurality of fine metallic leads extending inwardly of said lead frame to lead terminations aligned with and brazed to said braze pads, a web bar interconnecting said fine leads adjacent to, and within about 0.06 inches of, their terminations and spaced outwardly of said IC package, and means for aligning said lead frame with respect to a punch tool to be used for severing said web from said leads and said leads from said lead frame.
2. An intermediate product according to claim 1 wherein said lead frame is rectangular and a plurality of leads extend in parallel with one another from each of four sides of said lead frame for respective alignment and registration with braze pads on each of four sides of said package.
3. An intermediate product to claim 2 wherein the web bar associated with each said plurality of leads is joined to form a rectangular web bar frame to surround a said package during attachment of said leads to said attachment points.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US16191488A | 1988-02-29 | 1988-02-29 | |
| US161,914 | 1988-02-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1292326C true CA1292326C (en) | 1991-11-19 |
Family
ID=22583341
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000592906A Expired - Fee Related CA1292326C (en) | 1988-02-29 | 1989-02-27 | Alignment of leads for ceramic integrated circuit packages |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0357759A1 (en) |
| JP (1) | JPH02501179A (en) |
| CA (1) | CA1292326C (en) |
| WO (1) | WO1989008324A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6323549B1 (en) | 1996-08-29 | 2001-11-27 | L. Pierre deRochemont | Ceramic composite wiring structures for semiconductor devices and method of manufacture |
| CN1112838C (en) * | 1996-12-30 | 2003-06-25 | 皮埃尔·L·德罗什蒙特 | Ceramic substrate having composite wiring structure and method for manufacturing the same |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4289922A (en) * | 1979-09-04 | 1981-09-15 | Plessey Incorporated | Integrated circuit package and lead frame |
| GB2079534A (en) * | 1980-07-02 | 1982-01-20 | Fairchild Camera Instr Co | Package for semiconductor devices |
| US4626478A (en) * | 1984-03-22 | 1986-12-02 | Unitrode Corporation | Electronic circuit device components having integral spacers providing uniform thickness bonding film |
| JPS613434A (en) * | 1984-06-15 | 1986-01-09 | Ricoh Co Ltd | Manufacture of semiconductor device |
-
1989
- 1989-02-22 EP EP19890903582 patent/EP0357759A1/en not_active Ceased
- 1989-02-22 JP JP50331189A patent/JPH02501179A/en active Pending
- 1989-02-22 WO PCT/US1989/000727 patent/WO1989008324A1/en not_active Application Discontinuation
- 1989-02-27 CA CA000592906A patent/CA1292326C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0357759A1 (en) | 1990-03-14 |
| WO1989008324A1 (en) | 1989-09-08 |
| JPH02501179A (en) | 1990-04-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |