GB2155395A - Apparatus for flash-free insert molding - Google Patents
Apparatus for flash-free insert molding Download PDFInfo
- Publication number
- GB2155395A GB2155395A GB08505652A GB8505652A GB2155395A GB 2155395 A GB2155395 A GB 2155395A GB 08505652 A GB08505652 A GB 08505652A GB 8505652 A GB8505652 A GB 8505652A GB 2155395 A GB2155395 A GB 2155395A
- Authority
- GB
- United Kingdom
- Prior art keywords
- mold
- metallic
- sealing means
- pair
- mold apparatus
- 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.)
- Withdrawn
Links
- 238000000465 moulding Methods 0.000 title claims abstract description 15
- 238000007789 sealing Methods 0.000 claims abstract description 32
- 239000004033 plastic Substances 0.000 claims abstract description 30
- 229920003023 plastic Polymers 0.000 claims abstract description 30
- 239000000463 material Substances 0.000 claims abstract description 21
- 239000004065 semiconductor Substances 0.000 claims abstract description 13
- 238000005538 encapsulation Methods 0.000 claims abstract description 5
- 238000000034 method Methods 0.000 claims description 9
- 230000000694 effects Effects 0.000 claims description 3
- 239000004809 Teflon Substances 0.000 claims description 2
- 229920006362 Teflon® Polymers 0.000 claims description 2
- 239000007769 metal material Substances 0.000 claims description 2
- 239000002184 metal Substances 0.000 abstract 1
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 7
- 238000010137 moulding (plastic) Methods 0.000 description 5
- 230000000740 bleeding effect Effects 0.000 description 4
- 239000012778 molding material Substances 0.000 description 4
- 239000012530 fluid Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000004593 Epoxy Substances 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000013011 mating Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000002991 molded plastic Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/14—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles
- B29C45/14639—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles for obtaining an insulating effect, e.g. for electrical components
- B29C45/14655—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles for obtaining an insulating effect, e.g. for electrical components connected to or mounted on a carrier, e.g. lead frame
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/0038—Moulds or cores; Details thereof or accessories therefor with sealing means or the like
- B29C33/0044—Moulds or cores; Details thereof or accessories therefor with sealing means or the like for sealing off parts of inserts projecting into the mould cavity
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/14—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles
- B29C45/14336—Coating a portion of the article, e.g. the edge of the article
- B29C45/14418—Sealing means between mould and article
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
- B29C70/68—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts by incorporating or moulding on preformed parts, e.g. inserts or layers, e.g. foam blocks
- B29C70/72—Encapsulating inserts having non-encapsulated projections, e.g. extremities or terminal portions of electrical components
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- B29L2031/00—Other particular articles
- B29L2031/34—Electrical apparatus, e.g. sparking plugs or parts thereof
- B29L2031/3406—Components, e.g. resistors
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
- Encapsulation Of And Coatings For Semiconductor Or Solid State Devices (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
Abstract
In an apparatus for substantially flash-free molding of metallic inserts sealing means (12) are provided as part of the surfaces of metallic mold parts (10A, 10B) to provide a very tight seal around the metallic insert. The sealing means (12) comprises a material of higher thermal coefficient of expansion than the material of the mold parts (10A, 10B). Plastics material or sort metal are disclosed as suitable sealing means. The apparatus is suitable for encapsulation of semiconductor devices having conductive leads extending from a plastics body. <IMAGE>
Description
SPECIFICATION
Method and apparatus for flash-free insert molding
This invention relates generally to the plastic molding of objects having protruding metallic inserts, and more specifically, to the plastic encapsulation of semiconductor electronic devices.
In the plastic encapsulation of a semiconductor device or integrated circuit assembled on a metallic lead frame which is used for making external electrical connections, the device and lead frame are inserted into a mold cavity with the leads extending out of the cavity. The mold is heated and the plastic is injected into the mold in liquid or semi-liquid form under very high pressure. Alternatively, the plastic is inserted into a cavity within the mold as a plurality of small plastic beads or particles and subsequently heated. Due to its fluidity, the plastic material runs out of the mold through any crevices where the sealing is imperfect.Since the metallic leadframe upon which the mold halves close does not ordinarily have very close tolerances, the variation in its thickness prevents the mold halves from closing uniformly on the desired portions of the lead frame, thus leaving areas where the high-pressure plastic will be forced out around the leads. When the plastic hardens, not only will it surround the semiconductor device or integrated circuit and the desired portions of the leadframe, but it will also cover portions of the lead frame which are desirably exposed. That is, the bleeding of the plastic from the mold cavity will leave an unacceptable plastic flashing or coating on undesired portions of the metallic lead frame or insert.
While various methods of removing this undesirable flash are known in the art, a need has existed to provide a method and mold members which result in much more nearly perfect sealing of the mold portions, especially where they clamp the metallic lead frame or inserts so that the bleeding and the resultant flash are largely obviated.
In accordance with one embodiment of this invention, it is an object of this invention to provide an improved method and apparatus for the insert molding of small objects.
It is another object of this invention to provide an improved mold apparatus for the insert molding of semiconductor electronic devices and integrated circuits.
It is a further object of this invention to provide an improved method and mold apparatus for preventing the plastic molding material from sticking to the leads extending from the object being encapsulated.
It is still another object of this invention to provide a method and mold apparatus which provides a substantially absolute seal between the mold members and portions of the insert of the molded object.
In accordance with a preferred embodiment of the present invention, the portions of the mold members which clamp the metallic lead frame or insert are provided with a seal material which is softer than but has a higher coefficient of expansion than the body of the mold. When the metallic insert is clamped in the mold and the assembly is heated up to the molding temperature, the difference in the thermal expansion between the mold and the seal material will effect an absolute seal between the mold and the metallic lead frame or insert.
In accordance with another embodiment of this invention, a plastic seal material is provided at the locations where metallic mold portions embrace the lead frame of a semiconductor electronic device or integrated circuit. Since the plastic seal is both softer and has a higher coefficient of expansion than the metallic mold portions, heating of the assembly to the molding temperature results in a nearly bleed-free seal between the mold and the metallic insert lead frame. In this manner, an undesirable flash is almost completely obviated while avoiding the necessity for close tolerance lead frames and possibly enabling somewhat looser tolerances on the molds themselves.
The foregoing and other objects, features, and advantages of this invention will be apparent from the following, more particular, description of the preferred embodiments of this invention, as illustrated in the accompanying drawings.
Figure I is a perspective view of an insertmolded object, showing a molded plastic portion and a plurality of exposed metallic leads.
Figure 2 illustrates mating mold portions of top and bottom metallic molds suitable for use as described by this invention to produce the molded object of Figure 1.
Figure 3 is a cross-sectional cutaway view showing how the mold portions of Figure 2 fit around the insert-molded (lead frame) object of Figure 1.
Referring now to Figure 1, a perspective cutaway view illustrates an insert-molded object comprising a plastic body 1 partially surrounding a metallic insert comprising a plurality of leads 3 held together during the molding operation by orthogonal portions 5 upon which the mold portions seat. In the case where the insert molded object is a semiconductor electronic device or integrated circuit, portions 3 and 5 comprise a lead frame upon which the semiconductor device itself is mounted prior to its plastic encapsulation by plastic material or body 1. Apertures 7 permit the leads 3 to be electrically isolated by cutting away portions of the metallic sealing surface 5 of the lead frame after the device has been molded.
Referring now to Figure 2, there is illustrated the top half 10A and the bottom half 10B of portions of a mold suitable for the formation of the molded assembly of Figure 1. Cavity portions 11A and 11B are machined into the top mold portion 10A and the bottom mold portion 10B, respectively. It will be understood by those skilled in the art that there will ordinarily be many such cavities in a single mold so that a multiplicity of molded objects may be produced in one operation. That is, in the case of semiconductor devices, for example, a unitary metallic lead frame will have a multiplicity of semi conductor devices or integrated circuits attached to it, all of which devices will be individually surrounded by the plastic molding portion 1 of Figure 1 during the molding operation. For simplicity, the multiple mold cavities have not been shown in Figure 2.Also not shown are the various runners and culls essential to the flow control of the fluid or semi-fluid plastic material. These are also machined into the surfaces of the mold halves during their manufacture.
Referring now to Figure 3, the mold halves 10A and 10B are shown in position surrounding the leadframe 3 comprising the metallic insert of the device to be molded. It will be recalled that 1 is the plastic body to be formed on the metallic insert by the molding operation. In Figure 3, the mold halves are shown slightly separated from the metallic insert for clarity. Prior to the actual molding operation, these mold halves must be tightly clamped to the metallic insert in order to confine the molding material substantially to the cavity portions 11A and 11 B of the mold.With a large leadframe comprising many electronic devices or integrated circuits, the thickness variation in the lead frame across the surface of the mold will result in tight clamping at some few locations and a plurality of apertures or crevices through which the high-pressure high-temperature plastic molding material may bleed out from the location where the sealing is desired. In the case of semiconductor electronic devices or integrated circuits, the plastic molding material is usually an epoxy or some other plastic formulation which adheres very strongly to the metallic lead frame in order to provide hermiticity.
In the case of undesired bleeding, the resultant tightly adhering flash is difficult to remove and results in an uneconomical process.
In accordance with the present invention, sealing means having a greater thermal coefficient of expansion than the material of the metallic mold itself are provided on the surface of the mold and surrounding the cavity to which the molding compound is desirably constrained. Preferably, the sealing means are located on the surface of each of the mold halves at the locations where any flash would be most detrimental. The sealing means are also selected to be somewhat softer than the mold itself. One suitable material for the sealing means has been found to be plastic. In Figure 2, two plastic bands 12 which flask each half-cavity 11A or 11B each mold surface.Shown somewhat schematically, these plastic bands 12 may be anchored as shown at the ends of the mold, or placed in grooves machined into the mold surfaces along with the other features. Since the sealing means are somewhat softer than the mold itself, they will wear faster and are designed to be replaceable at suitable intervals. The sealing means 12 are preferably mounted on the mold surfaces after all the cavities, culls, and runners have been machined.
Then a final machining operation may be utilized to finish off both the mold surfaces and the plastic sealing means.
In operation, the mold halves are clamped about the metallic insert or lead frame. The sealing means 12 will tightly engage the thickest portions of the lead frame. Then as the assembly is heated up to the molding operation temperature, usually in the range of 1500C to 180 C, the difference in the thermal expansion between the mold material and that of the sealing means will effect a substantially absolute seal between the mold and the insert. In this way, bleeding is largely prevented and the resulting undesirable flash is substantially obviated.
While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departure from the spirit and scope of the invention. For example, teflon may be used as the plastic bands 12. Additionally, if desired, the sealing means or bands 12 can be made of a soft metal material rather than a plastic material.
Claims (12)
1. A mold apparatus for partially surrounding a metallic insert with a plastic material, comprising, in combination:
a pair of metallic mold means including a pair of surfaces each having at least one mold cavity therein; and
sealing means attached to each of said pair of surfaces for clamping said metallic insert in said mold apparatus, said sealing means comprising a material having a higher coefficient of expansion than said metallic mold means.
2. The mold apparatus according to Claim 1, wherein said sealing means comprise a material which is softer than said metallic mold means.
3. The mold apparatus according to Claim 1, wherein said sealing means comprise plastic material.
4. A mold apparatus for the individual encapsulation of multiple semiconductor devices mounted on a unitary metallic leadframe, comprising in combination:
a pair of metallic mold members, each of said pair having a surface including a multiplicity of cavity means for surrounding said semiconductor devices; and
sealing means mounted on said surface of said each of said pair of said mold members for clamping said lead frame around each of said cavity means, said sealing means comprising a material having a higher thermal coefficient of expansion than said metallic mold members.
5. The mold apparatus according to Claim 4, wherein said sealing means comprise a material which is softer than said metallic mold members.
6. The mold apparatus according to Claim 4, wherein said sealing means comprise a plastic material.
7. The mold apparatus according to Claim 6, wherein said sealing means comprise strips of plastic material flanking each of each multiplicity of cavities.
8. A method for substantially flash-free metallic insert molding comprising the steps of:
providing a pair of metallic mold members each containing at least one cavity corresponding to the object to be molded;
mounting sealing means on the surface of each of said pair of metallic mold members proximate said cavity, said sealing means having a higher thermal coefficient of expansion than said metallic mold members;
clamping said metallic insert between said pair of metallic mold members and said sealing means; and
raising the temperature of said mold members, said sealing means, and said metallic insert to provide a substantially bleed-free seal between said cavities and the extremities of said metallic insert away from said cavities.
9. The mold apparatus of claim 1 wherein said sealing means comprises teflon.
10. The mold apparatus according to claim 1 wherein said sealing means comprises a soft metal material.
11. A method of molding substantially as hereinbefore described with reference to the accompanying drawings.
12. A mold apparatus substantially as hereinbefore described with reference to the accompanying drawings.
Amendments to the claims have been filed, and have the following effect: (a) Claims 11 & 12 above have been deleted.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US58684384A | 1984-03-06 | 1984-03-06 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8505652D0 GB8505652D0 (en) | 1985-04-03 |
| GB2155395A true GB2155395A (en) | 1985-09-25 |
Family
ID=24347315
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08505652A Withdrawn GB2155395A (en) | 1984-03-06 | 1985-03-05 | Apparatus for flash-free insert molding |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS6110420A (en) |
| DE (1) | DE3508008A1 (en) |
| FR (1) | FR2560814A1 (en) |
| GB (1) | GB2155395A (en) |
| NL (1) | NL8500636A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2253369A (en) * | 1991-02-22 | 1992-09-09 | Motorola Inc | Avoiding leakage of plastic, during encapsulation of semiconductor devices |
| WO2001084618A2 (en) * | 2000-05-02 | 2001-11-08 | Siemens Production And Logistics Systems Ag | Method and mould for encapsulating electronic circuit carriers by injection moulding |
| EP1419866A1 (en) * | 2001-08-22 | 2004-05-19 | Sony Corporation | Method and device for forming module electronic component and module electronic component |
| US20180272575A1 (en) * | 2014-10-31 | 2018-09-27 | Compagnie Plastic Omnium | Mold for producing a part made from plastic materials, comprising an optimized sealing system |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4333415C2 (en) * | 1993-09-30 | 1999-03-04 | Siemens Ag | Device for enveloping a semiconductor component and an associated heat sink with plastics |
| DE10335078B4 (en) * | 2003-07-31 | 2008-04-03 | Osram Opto Semiconductors Gmbh | A method of manufacturing a device having a leadframe formed by molding and a device having a leadframe enveloped by a molding |
| DE102004057810B4 (en) * | 2004-11-30 | 2008-08-07 | Webasto Ag | Plastic molding and method for producing a plastic molding |
| JP2009300396A (en) * | 2008-06-17 | 2009-12-24 | Nippon Soken Inc | Rotation angle detecting device |
| CN113799332B (en) * | 2021-09-17 | 2023-04-11 | 宁波固德模塑有限公司 | Flash-free mold for thin-wall injection molding product |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1221293A (en) * | 1967-02-06 | 1971-02-03 | British Industrial Plastics | Cold-press moulding equipment |
-
1985
- 1985-03-05 GB GB08505652A patent/GB2155395A/en not_active Withdrawn
- 1985-03-06 NL NL8500636A patent/NL8500636A/en not_active Application Discontinuation
- 1985-03-06 FR FR8503977A patent/FR2560814A1/en not_active Withdrawn
- 1985-03-06 JP JP4451685A patent/JPS6110420A/en active Pending
- 1985-03-06 DE DE19853508008 patent/DE3508008A1/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1221293A (en) * | 1967-02-06 | 1971-02-03 | British Industrial Plastics | Cold-press moulding equipment |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2253369A (en) * | 1991-02-22 | 1992-09-09 | Motorola Inc | Avoiding leakage of plastic, during encapsulation of semiconductor devices |
| GB2253369B (en) * | 1991-02-22 | 1994-12-07 | Motorola Inc | Method and apparatus for encapsulating a semiconductor device |
| WO2001084618A2 (en) * | 2000-05-02 | 2001-11-08 | Siemens Production And Logistics Systems Ag | Method and mould for encapsulating electronic circuit carriers by injection moulding |
| WO2001084618A3 (en) * | 2000-05-02 | 2002-02-07 | Siemens Production & Logistics | Method and mould for encapsulating electronic circuit carriers by injection moulding |
| EP1419866A1 (en) * | 2001-08-22 | 2004-05-19 | Sony Corporation | Method and device for forming module electronic component and module electronic component |
| EP1419866A4 (en) * | 2001-08-22 | 2009-07-01 | Sony Corp | Method and device for forming module electronic component and module electronic component |
| US20180272575A1 (en) * | 2014-10-31 | 2018-09-27 | Compagnie Plastic Omnium | Mold for producing a part made from plastic materials, comprising an optimized sealing system |
Also Published As
| Publication number | Publication date |
|---|---|
| NL8500636A (en) | 1985-10-01 |
| GB8505652D0 (en) | 1985-04-03 |
| FR2560814A1 (en) | 1985-09-13 |
| DE3508008A1 (en) | 1985-11-28 |
| JPS6110420A (en) | 1986-01-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |