CN110729252A

CN110729252A - 0.4 mm-pitch ceramic four-side lead flat shell and preparation method thereof

Info

Publication number: CN110729252A
Application number: CN201911055678.9A
Authority: CN
Inventors: 杨振涛; 彭博
Original assignee: CETC 13 Research Institute
Current assignee: CETC 13 Research Institute
Priority date: 2019-10-31
Filing date: 2019-10-31
Publication date: 2020-01-24
Anticipated expiration: 2039-10-31
Also published as: CN110729252B

Abstract

The invention provides a 0.4 mm-pitch ceramic four-side lead flat shell and a preparation method thereof, belonging to the technical field of ceramic packaging shells and comprising a ceramic body, a plurality of bonding pads and leads, wherein the bonding pads are uniformly distributed along four sides of the upper end surface or the lower end surface of the ceramic body; the quantity of lead wire with the quantity of pad is the same, and the one-to-one is connected with the pad, and the pitch of lead wire is 0.4mm, and the lead wire includes first fixed part, second fixed part and connecting portion, and first fixed part is parallel with the pad and the periphery of the ceramic body of not salient, and the second fixed part extends and is parallel with the PCB board to the outside of ceramic body, and connecting portion slope is connected between first fixed part and second fixed part. According to the 0.4 mm-pitch ceramic four-side lead flat shell provided by the invention, the minimum pitch of the ceramic four-side lead flat shell is reduced from 0.50mm to 0.40mm, so that the requirements of circuit applications such as a network port chip memory and the like on the shell are met.

Description

0.4 mm-pitch ceramic four-side lead flat shell and preparation method thereof

Technical Field

The invention belongs to the technical field of ceramic packaging shells, and particularly relates to a 0.4mm pitch ceramic four-side lead flat shell and a preparation method thereof.

Background

At present, a 0.40mm pitch product of a Plastic Package QFP (Plastic Quad Flat Package) device is generally used, the 0.40mm pitch product mainly adopts a Plastic Package process to mount a chip on a Plastic Package substrate, finally, a molding compound is adopted to carry out encapsulation on the chip, and leads are led out from the middle part of a shell.

In order to meet the requirement of high reliability, and simultaneously, in order to be compatible with a foreign 0.40mm pitch QFP plastic package device, ceramic package is required, and in order to meet the requirement of miniaturization of the device, the requirements of continuous reduction on the size, the pitch and the like of a shell are required.

At present, the lead pitch of a packaging device of a Ceramic Quad Flat package (CQFP-Ceramic Quad Flat Pack) can only reach 0.50mm, and needs to be further improved.

Disclosure of Invention

The invention aims to provide a 0.4 mm-pitch ceramic quad flat package, and aims to solve the problem that a 0.40 mm-pitch product of a plastic-packaged QFP device is unreliable.

In order to achieve the purpose, the invention adopts the technical scheme that: the utility model provides a flat shell of pottery four sides lead wire of 0.4mm pitch, including the ceramic body that is equipped with the cavity, a plurality of edges the even pad of laying of the up end of ceramic body or the four sides of lower terminal surface and lead wire, the quantity of lead wire with the quantity of pad is the same, and the one-to-one with the pad is connected, the pitch of lead wire is 0.4mm, the lead wire including be used for with pad welded first fixed part, be used for with PCB board welded second fixed part and connect connecting portion between first fixed part and the second fixed part, first fixed part with the pad is parallel and not salient the periphery of ceramic body, the second fixed part to the outside of ceramic body extend and with the PCB board is parallel, connecting portion slope is connected first fixed part with between the second fixed part.

As another embodiment of the application, at the intersection of four corners of the ceramic body, the length of two adjacent bonding pads is smaller than that of the rest bonding pads, and two vertex angles of the two adjacent bonding pads closest to each other are provided with first chamfers; and at the intersection of four corners of the ceramic body, two vertex angles, which are closest to the first fixing parts of the two adjacent leads, are provided with second chamfers.

As another embodiment of the application, the side surface of one of the pads at the intersection is provided with an index mark.

As another embodiment of the present application, the second fixing portion and/or the connecting portion are respectively provided with a widening section.

As another embodiment of the present application, the width of the lead is 0.15 + -0.05 mm, and the thickness of the lead is 0.1 + -0.05 mm.

As another embodiment of the present application, the position degree of the lead is 0.15mm or less.

As another embodiment of the present application, the flatness of the second fixing portion connected to the PCB board is less than or equal to 0.1 mm.

As another embodiment of the present application, the number of the leads is 4-352.

As another embodiment of the application, the length of the bonding pad is greater than or equal to 1.0mm, the width of the bonding pad is 0.2-0.3mm, and the distance between two adjacent bonding pads in the same side is greater than or equal to 0.1 mm.

Another object of the present invention is to provide a method for manufacturing a ceramic quad flat package with a 0.4mm pitch, comprising:

double-sided etching is adopted;

the wall thickness of the ceramic body is more than or equal to 0.4 mm;

the thickness of the bottom of the cavity of the ceramic body is more than or equal to 0.2 mm.

The ceramic four-side lead flat shell with the pitch of 0.4mm provided by the invention has the beneficial effects that: compared with the prior art, the 0.4 mm-pitch ceramic four-side lead flat shell is formed by welding 0.4 mm-pitch leads on the basis of the four-side lead flat shell, and the minimum pitch of the ceramic four-side lead flat shell is reduced to 0.40mm from 0.50mm at present, so that the requirements of circuit applications such as a network port chip memory and the like on the shell are met; in order to realize a lead with 0.4 pitch and reduce the external dimension of the shell, the lead is divided into three parts, including a first fixing part for welding with a bonding pad, a second fixing part for welding with a PCB and a connecting part connected between the first fixing part and the second fixing part, and after the three parts are connected, the lead is in a bent shape to form a three-dimensional brazing structure; after the lead is welded with the bonding pad, good meniscus solder wrap angles can be formed at two ends of the first fixing part of the lead, so that the impact of external force on the metalized layer is relieved, the reliability of the welding strength of the lead is ensured, and the connection strength of the lead is ensured; meanwhile, under the condition of the same pin number, the pitch of 0.40mm is adopted, the external dimension of the shell can be reduced by more than 18% compared with the shell with the pitch of 0.50mm, and compared with the conventional shell, the overall dimension of the shell is effectively reduced, and the development trend of miniaturization design is met.

According to the preparation method of the flat shell with the 0.4mm pitch ceramic four-side lead, provided by the invention, double-sided etching is adopted, the side etching amount can be reduced, the minimum wall thickness of the shell can be 0.40mm, the bottom of the core cavity of the shell can reach 0.20mm, and the miniaturization of the appearance size of the shell is realized on the premise of meeting the reliability.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed for the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a 0.4mm pitch ceramic quad flat package according to an embodiment of the present invention;

FIG. 2 is a schematic top view of the structure of FIG. 1;

FIG. 3 is a schematic bottom view of the structure of FIG. 1;

FIG. 4 is a schematic view of a portion of the enlarged structure at A in FIG. 3

FIG. 5 is a schematic structural diagram of a 0.4mm pitch ceramic quad flat package according to a second embodiment of the present invention;

FIG. 6 is a schematic top view of the structure of FIG. 5;

FIG. 7 is a bottom view of the structure of FIG. 5;

FIG. 8 is a schematic structural diagram of a 0.4mm pitch ceramic quad flat package according to a third embodiment of the present invention;

FIG. 9 is a schematic top view of the structure of FIG. 8;

FIG. 10 is a bottom view of the structure of FIG. 8;

fig. 11 is a schematic structural diagram of the soldering of the 0.4mm pitch ceramic quad flat package and the PCB according to the embodiment of the present invention.

In the figure: 1. a ceramic body; 2. solder wrap angle; 3. a lead wire; 31. a second fixed part; 32. a connecting portion; 33. a first fixed part; 34. a widening section; 4. a cavity; 5. a pad; 6. index identification; 7. chamfering; 8. a bonding finger; 9. a heat sink; 10. a sealing ring; 11. a chip; 12. a cover plate; 13. and (7) a PCB board.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Referring to fig. 1 to 11, a 0.4mm pitch ceramic quad flat package according to the present invention will be described. The ceramic four-side lead flat shell with the pitch of 0.4mm comprises a ceramic body 1 provided with a cavity 4, a plurality of bonding pads 5 uniformly distributed along four sides of the upper end surface or the lower end surface of the ceramic body 1 and leads 2; the quantity of lead 2 with pad 5's quantity is the same, and the one-to-one with pad 5 connects, the pitch of lead 2 is 0.4mm, lead 2 including be used for with pad 5 welded first fixed part 33, be used for with PCB board 13 welded second fixed part 31 and connect connecting portion 32 between first fixed part 33 and the second fixed part 31, first fixed part 33 with pad 5 is parallel and not salient the periphery of ceramic body 1, second fixed part 31 to the outside of ceramic body 1 extend and with PCB board 13 is parallel, connecting portion 32 slope is connected first fixed part 33 with between the second fixed part 31.

Compared with the prior art, the 0.4 mm-pitch ceramic four-side lead flat shell is characterized in that the lead 2 with the pitch of 0.4mm is welded on the basis of the four-side lead flat shell, and the minimum pitch of the ceramic four-side lead flat shell is reduced to 0.40mm from 0.50mm at present, so that the requirements of circuit applications such as a network port chip memory and the like on the shell are met; in order to realize the lead 2 with 0.4 pitch and reduce the external dimension of the shell, the lead 2 is divided into three parts, including a first fixing part 33 for welding with the pad 5, a second fixing part 31 for welding with the PCB 13 (also known as printed circuit board, printed circuit board for short), and a connecting part 32 connected between the first fixing part 33 and the second fixing part 31, after the three parts are connected, the lead 2 is bent to form a three-dimensional soldering structure, after the lead 2 is welded with the pad 5, a good meniscus solder wrap angle 2 can be formed at both ends of the first fixing part 33 of the lead 2, the impact of external force on the metallization layer is relieved, the reliability of the welding strength of the lead 2 is ensured, the connecting strength of the lead 2 is ensured, meanwhile, under the condition of the same pin number, the external dimension with 0.40mm pitch can be as minimum 3mm multiplied by 3mm, the outer dimension of the shell with the 0.5mm pitch is 5mm multiplied by 5mm, so that the shell with the 0.50mm pitch is reduced by more than 18 percent compared with the shell with the 0.50mm pitch, and compared with the conventional shell, the overall size of the shell is effectively reduced, and the development trend of miniaturization design is met.

In the present embodiment, for further explanation that the first fixing portion 33 does not protrude from the outer periphery of the ceramic body 1, referring to fig. 1, a certain distance is provided between the first fixing portion and the outer periphery of the ceramic body, and after the lead 2 is welded to the pad 5, a good "meniscus" solder fillet 2 can be formed at both ends of the first fixing portion 33 of the lead 2.

As a specific embodiment of the flat housing with 0.4mm pitch ceramic four-side lead wires, please refer to fig. 2, 4, 6, and 9, at the intersection of four corners of the ceramic body 1, the length of two adjacent bonding pads 5 is smaller than the length of the rest bonding pads 5, and two vertex angles of the two adjacent bonding pads closest to each other are provided with chamfers 7; chamfers 7 are arranged at two vertex angles, which are closest to the first fixing parts 33 of two adjacent leads 2, at the intersection of four corners of the ceramic body 1. Because the minimum overall dimension of the flat shell of the ceramic four-side lead mainly depends on the number of pins of the shell and the pitch of the lead, when the number of pins and the pitch of the lead are fixed, the overall dimension is also basically fixed, for preparing the flat shell of the ceramic four-side lead with the pitch of 0.5mm, if the shell with the pitch of 0.4mm is prepared, the overall dimension is further reduced, the pin pads 5 on four corners of the shell can be overlapped, and the leads on the four corners can be overlapped and can not be etched, in order to avoid the four corners to be crossed, the embodiment carries out chamfer 7 treatment on the pads 5 at the four corners and the lead at the welding position, the overlapping is avoided, on the premise of ensuring the etching processing of the leads which are not crossed, under the condition that the length dimension of the pads 5 is reduced, the welding area of the leads is effectively ensured, the.

As a specific implementation manner of the embodiment of the present invention, please refer to fig. 4, a side surface of one of the pads 5 located at the intersection is provided with an index mark 6. The index mark 6 is provided to facilitate the identification of the position during welding, and the index mark mentioned later in the text is collectively referred to as 6 in the figures and is not further referred to.

Referring to fig. 2 and 3, as a specific implementation manner of the embodiment of the present invention, the second fixing portion 31 and/or the connecting portion 32 are respectively provided with a widening section 34. When ceramic package lead number exceeded 144, need carry out the post forming to lead wire 2 when using, need carry out the processing of once more bending to lead wire 2 promptly, because the lead wire 2 width of this embodiment is narrower, the easy emergence fracture of lead wire 2 when post forming, for avoiding this type of problem, this embodiment has carried out the widening to the 2 positions of lead wire that need carry out the post forming and has handled, just so can guarantee that 2 post forming of lead wire can not take place the fracture, has improved the fastness of lead wire 2 moreover.

As a specific implementation manner of the embodiment of the present invention, please refer to fig. 1, fig. 5 and fig. 8, the width of the lead 2 is 0.15 ± 0.05mm, and the thickness C of the lead 2 is 0.1 ± 0.05 mm. The lead width central value of 0.15mm of the 0.40mm pitch ceramic four-side lead flat shell is reduced by 25% compared with the lead 2 width of 0.20mm of 0.50mm pitch, the lead thickness central value of 0.1mm is reduced by 33% compared with the lead thickness of 0.15mm of 0.50mm pitch, and the shell is miniaturized by processing the size of the lead 2. Meanwhile, in order to ensure the fatigue resistance of the lead 2, the fatigue portion of the lead 2 may be widened, i.e., the widened section 34 in the above embodiment.

In the present embodiment, referring to fig. 2, the pitch B between adjacent leads 2 is 0.15 ± 0.05 mm. This does not mean the distance between the widened sections 34 of the two leads 2.

Referring to fig. 2, 6 and 9, as a specific implementation manner of the embodiment of the present invention, the position degree of the lead 2 is less than or equal to 0.15 mm. Through setting for the position deviation, guarantee that lead wire 2 welded position is accurate, and then guarantee the pitch requirement between the lead wire 2.

Referring to fig. 11, as a specific implementation manner of the embodiment of the present invention, the flatness of the second fixing portion 31 connected to the PCB 13 is less than or equal to 0.1 mm. By defining the flatness, the reliability of soldering of the lead 2 to the PCB 13 is improved.

As a specific implementation manner of the embodiment of the present invention, referring to fig. 1 to 10, the number of the leads 2 is 4 to 352, which can meet the requirements of different packaged devices.

In the embodiment, the minimum external dimension of the shell can reach 3mm multiplied by 3mm, under the condition of the same pin number, the 0.40mm pitch is adopted, the external dimension of the shell can be reduced by more than 18% compared with the shell with the 0.50mm pitch, and compared with the conventional tube shell, the overall dimension of the tube shell is effectively reduced, and the development trend of miniaturization design is met.

Referring to fig. 2, 7 and 10, the length of the bonding pad 5 is greater than or equal to 1.0mm, the width of the bonding pad is 0.2-0.3mm, and the distance between two adjacent bonding pads 5 in the same side is greater than or equal to 0.1 mm. In this embodiment, the central value of the width of the pad 5 of the 0.40mm pitch ceramic four-side lead flat housing is 0.28mm, and taking the central value of the width of the pad 5 of the 0.40mm pitch ceramic four-side lead flat housing as 0.28mm as an example, the width is reduced by 20% compared with the width of the pad 5 of 0.50mm pitch by 0.35mm, and at this time, the welding length of the lead should be lengthened as much as possible to ensure the welding strength of the lead 2. Wherein, the distance D between the centers of the adjacent bonding pads 5 is 0.4 +/-0.05 mm.

In this embodiment, referring to fig. 9, in order to identify the number of the bonding finger during bonding, the bonding finger 8 in the cavity 4 has an index mark 6 of the bonding finger 8; the alignment mark or the alignment mark is arranged in the core cavity, the alignment mark is a circular or triangular structural graph, and the alignment cavity is a positioning cavity structure with a cross or L-shaped structure, so that the chip can be conveniently and accurately mounted.

In this embodiment, referring to fig. 9, in order to facilitate position identification during automatic bonding, a cross-shaped or L-shaped alignment identification mark is added to each outermost bonding finger 8.

In this embodiment, the sealing surface has an obvious direction index mark to facilitate direction alignment during device testing and board-level mounting.

In this embodiment, the minimum width of the bonding fingers 8 can achieve 0.06mm, and the minimum distance between the bonding fingers 8 can achieve 0.06 mm. The housing provided by the embodiment has the advantages that the width of the lead, the thickness of the lead, the pitch and the center distance of the lead, the width of the pad, the pitch and the center distance of the pad, and the width and the pitch of the bonding finger are obviously reduced compared with the size of a housing with the pitch of 0.5mm of the same lead, the miniaturization of the housing is realized, the housing has the characteristics of small volume, light weight, good packaging density, good high thermoelectric performance, suitability for surface mounting and the like, and mainly relates to a Ceramic Quad Flat Package (CQFP) and a multi-chip ceramic package (MCP-multi-chip package) adopting a CQFP packaging form, a digital logic chip, an analog transceiver circuit, a memory, a passive element and the like are packaged in a cavity 4, the packaging density is higher, the system function is better, and the packaging structure is mainly applied to various high-density integrated circuit systems such as advanced communication engines, SRAM, shaft-angle converters and the like.

The shell provided by the embodiment is divided into a top-out mode and a bottom-out mode. A top leading-out mode, as shown in fig. 1 and fig. 11, secondary forming of the lead is required during board-level installation, the lead 2 has a large forming height, is easy to absorb thermal stress between the PCB 13 and the housing, and is suitable for ceramic parts with large external dimensions; the bottom lead-out mode is shown in fig. 5 and 8, the lead 2 is low in forming height and weak in stress absorption capacity, and is suitable for a structure with a small ceramic piece size. The housing provided by the embodiment mainly comprises a ceramic part 1, a sealing ring 10 (when necessary), a lead 3, a heat sink 9 (when necessary) and an insulating ceramic strip (when necessary), wherein the ceramic part is made of 90% of alumina and is manufactured by adopting a multilayer alumina ceramic tungsten metallization high-temperature co-firing process, the sealing ring 10 and the lead are made of iron-nickel alloy or iron-nickel-cobalt alloy, the heat sink 9 is made of tungsten-copper, molybdenum-copper, CPC and the like, and the ceramic part 1, the sealing ring 10, the heat sink 9 and the lead are welded by adopting silver-copper solder. The metal sealing ring is used for gold-tin sealing, parallel seam welding or laser seam welding sealing, and the heat sink is used for grounding or heat dissipation of the chip 11.

double-sided etching is adopted;

the wall thickness of the ceramic body 1 is more than or equal to 0.4 mm;

the bottom thickness of the cavity 4 of the ceramic body 1 is more than or equal to 0.2 mm.

In this embodiment, a double-sided etching method is adopted for a case with a 0.4mm pitch. The etching process belongs to a stress-free processing means, and is an engineering production technology for protecting a workpiece part by a photosensitive resist and removing unprotected metal by a strong oxidant through chemical oxidation reaction to obtain a burr-free and stress-free flat precise pattern.

For the etching process, since the essence of etching is by chemical reaction between the etching solution and the material to be etched, the wet etching is non-directional and the problem of side over-etching is inevitable.

The side excessively etches and can lead to the decline of the effective sectional area of lead wire, and lead wire edge attenuation and unsettled receive the impact of mould among the shaping process of bending, cause lead wire edge fracture, influence lead wire pulling force and lead wire fatigue performance, cause very big hidden danger to the lead wire fastness. Especially for the case with 0.40mm pitch, the lead width is reduced by 25% compared with 0.50mm pitch, the lead thickness is reduced by 33% compared with 0.50mm pitch, and the influence of side surface over etching on the firmness of the lead is more prominent.

In this embodiment, double-sided etching is employed, and the amount of side etching is reduced. However, the temperature during etching must not exceed 60 ℃ due to the limitation of high temperature resistance of the equipment, and cooling is necessary during etching in order to maintain a constant temperature. The etching is mainly controlled by the workpiece conveying speed, and the etching speed is determined by controlling the position of the workpiece, which is achieved when the workpiece is etched through in the etching machine, so as to ensure the etching precision.

In the preparation method of the embodiment, the lead is subjected to spray or sputtering double-sided etching, so that the etching acting force in the vertical direction is increased, the vertical etching speed is increased, and the lead processing is realized.

The shell prepared by the embodiment also has the following advantages: the packaging structure is provided with one or more cavities 4, the maximum number of the cavities 4 can reach 10, and a plurality of chips and various passive elements can be installed inside the packaging structure, so that the packaging requirement of high integration level of a user is met; the ceramic shell has the characteristics of multilayer wiring, high reliability, high air tightness, strong heat dissipation capacity and the like; the ceramic case may have a wiring structure of 2 to 50 layers; the encapsulation air tightness is high, and the air tightness meets the requirement of less than or equal to 1 multiplied by 10^-3Pa·cm³S, A4; the reliability is high, can satisfy temperature cycle: -65 ℃ to 175 ℃, 200 times, constant acceleration: 30000g, Y1 direction, 1 min.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

The flat shell of ceramic four sides lead wire of 1.0.4mm pitch, its characterized in that includes:

a ceramic body provided with a cavity;

the bonding pads are uniformly distributed along the four edges of the upper end surface or the lower end surface of the ceramic body; and

the lead wire, quantity with the quantity of pad is the same, and the one-to-one with the pad is connected, the pitch of lead wire is 0.4mm, the lead wire including be used for with pad welded first fixed part, be used for with PCB board welded second fixed part and connect connecting portion between first fixed part and the second fixed part, first fixed part with the pad is parallel and not salient the periphery of ceramic body, the second fixed part to the outside of ceramic body extend and with the PCB board is parallel, connecting portion slope is connected first fixed part with between the second fixed part.
2. The 0.4mm pitch ceramic quad flat package according to claim 1, wherein at the intersection of four corners of said ceramic body, the length of two adjacent pads is less than the length of each of the rest pads, and the two vertex angles of the two adjacent pads closest to each other are provided with first chamfers; and at the intersection of four corners of the ceramic body, two vertex angles, which are closest to the first fixing parts of the two adjacent leads, are provided with second chamfers.
3. The 0.4mm pitch ceramic quad flat package of claim 2, wherein a side of one of said pads at the intersection is provided with an index mark.
4. The 0.4mm pitch ceramic quad flat package of claim 1, wherein said second fixing portion and/or said connecting portion are provided with a widened section, respectively.
5. The 0.4mm pitch ceramic quad flat package of claims 1-4, wherein the leads have a width of 0.15 + 0.05mm and a thickness of 0.1 + 0.05 mm.
6. The 0.4mm pitch ceramic quad flat package of claims 1-4, wherein the lead position degree is 0.15mm or less.
7. The 0.4mm pitch ceramic quad flat package of claims 1-4, wherein the flatness of the second fixture portion connected to the PCB board is 0.1mm or less.
8. The 0.4mm pitch ceramic quad lead flat package of any of claims 1-4, wherein the number of leads is 4-352.
9. The 0.4mm pitch ceramic quad flat package of claim 1, wherein the pads have a length of 1.0mm or more and a width of 0.2-0.3mm, and the distance between two adjacent pads in a same side is 0.1mm or more.
10. A method of making a 0.4mm pitch ceramic quad flat lead package according to any of claims 1-9, comprising:

double-sided etching is adopted;

the wall thickness of the ceramic body is more than or equal to 0.4 mm;

the thickness of the bottom of the cavity of the ceramic body is more than or equal to 0.2 mm.