GB2155843A - Promoting mold release of molded objects - Google Patents
Promoting mold release of molded objects Download PDFInfo
- Publication number
- GB2155843A GB2155843A GB08505649A GB8505649A GB2155843A GB 2155843 A GB2155843 A GB 2155843A GB 08505649 A GB08505649 A GB 08505649A GB 8505649 A GB8505649 A GB 8505649A GB 2155843 A GB2155843 A GB 2155843A
- Authority
- GB
- United Kingdom
- Prior art keywords
- mold
- titanium nitride
- coating
- cavity
- release
- 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- Withdrawn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
- 230000001737 promoting effect Effects 0.000 title abstract description 6
- 238000000576 coating method Methods 0.000 claims abstract description 19
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 claims abstract description 18
- 239000011248 coating agent Substances 0.000 claims abstract description 17
- 239000000463 material Substances 0.000 claims abstract description 9
- 238000000034 method Methods 0.000 claims description 20
- 238000000465 moulding Methods 0.000 claims description 17
- 229910001220 stainless steel Inorganic materials 0.000 claims description 8
- 239000010935 stainless steel Substances 0.000 claims description 8
- 238000004519 manufacturing process Methods 0.000 claims description 5
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical group [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 4
- 229910052719 titanium Inorganic materials 0.000 claims description 4
- 239000010936 titanium Substances 0.000 claims description 4
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 2
- 239000004065 semiconductor Substances 0.000 abstract description 8
- 239000006082 mold release agent Substances 0.000 abstract description 2
- 150000001875 compounds Chemical class 0.000 description 6
- 230000007246 mechanism Effects 0.000 description 4
- 238000009472 formulation Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000004593 Epoxy Substances 0.000 description 2
- 230000000712 assembly Effects 0.000 description 2
- 238000000429 assembly Methods 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000004381 surface treatment Methods 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
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/56—Coatings, e.g. enameled or galvanised; Releasing, lubricating or separating agents
- B29C33/60—Releasing, lubricating or separating agents
-
- 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
- B29C33/0022—Multi-cavity moulds
-
- 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
- B29C70/74—Moulding material on a relatively small portion of the preformed part, e.g. outsert moulding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2909/00—Use of inorganic materials not provided for in groups B29K2803/00 - B29K2807/00, as mould material
- B29K2909/02—Ceramics
- B29K2909/04—Carbides; Nitrides
-
- 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)
- Moulds For Moulding Plastics Or The Like (AREA)
- Encapsulation Of And Coatings For Semiconductor Or Solid State Devices (AREA)
Abstract
For facilitating the mold-release of insert-molded semiconductor packages, a thin coating of a nitride-comprising material on the working surfaces of the mold parts (1A, 1B) is provided which is effective in promoting mold-release without the necessity for special ejector apparatus and mold-release agents. Titanium nitride is especially suitable.
Description
SPECIFICATION
Method and apparatus for promoting mold release of molded objects
Background of the invention 1. Field of the invention
This invention relates generally to a method and apparatus for promoting mold release of molded objects, and, more particularly, to a method and apparatus for promoting the mold release of insertmolded semiconductor packages.
2. Brief description of the prior art
In the past, a high proportion of semiconductor devices and integrated circuits have been packaged by injection molding of a lead frame assembly comprising one or more semiconductor chips conductively coupled to the lead frame. Typically, a large number of relatively small packages are formed in a single operation by insert molding in a multi-cavity mold. Such molds are quite complex and expensive, as they are generally fabricated to protect the leads which need be free of the molding compound and runners need to be provided to allow injection of the molding compound into each individual cavity. Because of the complexity of the mold and the specialized nature of the molding compound - which has to be electronically compatible with the semiconductor chip - the molded objects are usually very difficult to remove from the mold.It is commonplace to provide special ejector pins on the mold (and an ejector mechanism on the press) and to coat the mold surfaces with specialized mold release compounds in order to effect separation of the molded semiconductor packages from the mold cavities. Such requirements are expensive both in terms of capital costs and material costs. In addition, the production rate of the molding system is adversely affected by the need for a coating step and the frequent need to manually assist the ejection process and clean the cavities after each molding operation.
Accordingly, there has been a need to provide a method and apparatus for facilitating the removal of insert-molded electronic devices from the multicavity molds used in their fabrication.
Summary of the invention
It is therefore an object of this invention to provide a method and apparatus to promote mold-release of epoxy- molded objects.
It is yet another object of this invention to provide a method and apparatus for facilitating the removal of insert-molded electronic devices from their multi-cavity molds.
It is still another object of this invention to provide a method and apparatus for mold release of epoxy-molded objects without the use of special mold release formulations or expensive ejector mechanisms.
It is yet a further object of this invention to provide a method and apparatus for the mold release of packaged electronic devices while minimizing the need for conventional cleaning methods to prepare the mold for another injection cycle.
In accordance with one embodiment of this invention, a method for facilitating mold release of epoxy-molded electronic devices is disclosed which comprises providing a nitride-comprising coating on the molding surfaces of a multi-cavity mold. In this embodiment of the invention, a stainless steel multiple cavity mold is exposed to a titanium source in a nitrogen-containing atmosphere at about 16500C to about 1850 C to provide a wearing surface with excellent release properties.All of the surfaces of the multi-cavity mold which are to be exposed to the molding compound are provided with a coating of titanium nitride having a thickness of about two microns to provide a durable surface which facilitates the release of the molded parts from the mold cavities and reduces or eliminates the need to provide special ejector pins and a mold release ejector mechanism.
In accordance with another embodiment of this invention, a mold for the fabrication of a multiplicity of epoxy-molded electronic devices having a common lead frame is disclosed which comprises a metallic multi-cavity mold portion and titanium nitride means located on the surface of the mold portion for facilitating the mold-release of the electronic devices. In this embodiment, a stainless steel multi-cavity mold having a titanium nitride layer of about two microns on its molding surfaces is used to produce a multiplicity of epoxy-molded electronic devices.
The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of the preferred embodiments of the invention as illustrated in the accompanying drawing.
Brief description of the drawing
Figure 1 is a perspective view of a two-piece multiple-cavity mold for electronic devices according to the improvement of the present invention.
Figure 2 is a perspective view of a lead frame strip containing a plurality of locating holes and showing one of a plurality of integrated circuit chips.
Figure 3 is a perspective view of a portion of a lead frame strip with finished molded integrated circuit chips.
Detailed description of the invention
Referring to Figure 1, assemblies 1 and 2 comprise two halves of a multi-cavity mold suitable for the fabrication, for example, of multiple integrated circuit packages. Subassemblies 1A and 2A contain the multiple cavity half-apertures 3A and 3B which determine the bodies of the finished molded articles. Apertures 4 and 5 comprise the gate and runner system which provides the distribution of molding compound, typically an epoxy formulation, to the multiple cavities. The mold components shown are conventionally fabricated from stainless steel.
In the case, for example, where a multileaded integrated circuit is to be fabricated, Figure 2 shows a lead frame strip 10 containing a plurality of locat ing holes 12 and a plurality of integrated circuit chips, of which one chip 14 is shown in Figure 2.
The lead frame strip 10 is mated with the mold halves 1A and 1B by means of locating pins so that each integrated circuit chip 14 is coincident with one of the cavities 3A and 3B shown in Figure 1.
Referring now to Figure 3, a portion of a lead frame strip with finished molded integrated circuit chips is shown. Molded bodies 30 enclose each integrated circuit chip 14 and a portion of the lead frame strip 10 containing the multiple leads to each device.
As may be seen from Figure 3, the finished molded assembly includes not only the numerous small molded bodies 30 but also portions 50 of hardened molded material in the gate-runner portion of the system. The entire molded assembly must be removed as a unit from the mold halves 1A and 1 B in order to avoid damage to the delicate lead frame 10. In order to help accomplish this removal, it is commonplace to coat the surfaces of the mold halves 1A and 1B with a mold-release material prior to the molding operation and to provide ejector pins (not shown) which may, for example, exert pressure on each of the finished bodies 30 to detach them from the mold. Such measures are expensive of capital, material, and mold time, and thus contribute to an increase in cost of the finished product.
According to the preferred embodiment of the present invention, mold release is facilitated by a semipermanent coating on the working surfaces of the mold portions 1A and 2A which reduces bonding or sticking to the molded material. A preferred coating is titanium nitride with a thickness of about two microns, which results in a gold-colored mold surface which not only facilitates release of the molded objects but also increases the resistance of the mold to wear and erosion. The titanium nitride coating of the mold surfaces is achieved by applying a titanium-bearing material to the stainlesssteel surfaces of the multi-cavity mold and then exposing the mold to a nitrogen-bearing atmosphere in the range of about 1650 C to about 1850 C to provide the desired surface treatment.Titanium nitride surface coatings are described, for example, in military specifications MIL-5040 and MIL-52502.
Alternative descriptions of these processes are to be found in American Machine Specifications
AMS-52755 and AMS-2753. However, titanium nitride surface coatings have not been used in the past for promoting the mold release of insertmolded semiconductor packages.
Multi-cavity mold assemblies having their molding surfaces coated with a nitride, preferably titanium nitride, are used in this application to enable the molding of intricate objects without the need for expensive ejector mechanisms or special moldrelease agents. In addition, the need for elaborate clean-up of the molds is very much reduced using the coating disclosed herein as compared with the prior art. The foregoing advantages are particualrly pronounced with frame-leaded semiconductor electronic devices having bodies molded from epoxy formulations.
While the invention has been particularly shown and described with respect to a particular embodiment thereof, it will be understood by those skilled in the art that the foregoing and other charges in form and details may be made therein without departing from the spirit and scope of the invention.
Claims (16)
1. A method for facilitating the release of molded objects from a multi-cavity mold comprising providing a nitride-comprising coating on the molding surfaces of said multi-cavity mold.
2. The method of claim 1 wherein said nitridecomprising coating comprises titanium nitride.
3. The method of claim 2 wherein said mold comprises stainless steel.
4. A method for facilitating the release of epoxy-molded electronic devices from a multi-cavity mold comprising applying a titanium-bearing material to the molding surfaces of said multi-cavity mold.
5. The method of claim 4 further comprising exposing said titanium-bearing material applied to said molding surfaces to a nitrogen-bearing atmosphere in the temperature range of about 16500C to about 18500C thereby producing a titanium nitride coating on said molding surfaces.
6. The method of claim 5 wherein said titanium nitride coating being about two microns thick.
7. The method of claim 6 wherein said mold comprises stainless steel.
8. A multi-cavity mold comprising, in combination:
a stainless steel cavity portion; and
a nitride-comprising coating on said cavity portion of said mold.
9. The mold of claim 8 wherein said nitridecomprising coating comprises titanium nitride.
10. The mold of claim 9 wherein said titanium nitride coating having a thickness of about two microns.
11. A mold for the fabrication of a multiplicity of epoxy-molded electronic devices having a common lead frame comprising, in combination:
a metallic multi-cavity mold portion; and
titanium nitride means located on the surfaces of said mold portion for facilitating the mold-release of said electronic devices.
12. The mold of claim 11 wherein said titanium nitride means comprises a titanium nitride coating.
13. The mold of claim 12 wherein said titanium nitride coating being about two microns thick.
14. The mold of claim 13 wherein said metallic multi-cavity mold portion comprises stainless steel.
15. A method of facilitating release from a mold substantially as hereinbefore described with reference to the accompanying drawings.
16. A mold substantially as hereinbefore described with reference to the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US58684284A | 1984-03-06 | 1984-03-06 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8505649D0 GB8505649D0 (en) | 1985-04-03 |
| GB2155843A true GB2155843A (en) | 1985-10-02 |
Family
ID=24347310
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08505649A Withdrawn GB2155843A (en) | 1984-03-06 | 1985-03-05 | Promoting mold release of molded objects |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS615905A (en) |
| DE (1) | DE3508007A1 (en) |
| FR (1) | FR2560812A1 (en) |
| GB (1) | GB2155843A (en) |
| NL (1) | NL8500635A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4915609A (en) * | 1987-10-16 | 1990-04-10 | Klevotec, Gesellschaft Fur Rechnergestutzte Systemanwendungen Gmbh Co. K.G. | Sintering device for blanks of foamable plastics with undercuts |
| US5092558A (en) * | 1987-11-10 | 1992-03-03 | Sumitomo Electric Industries, Ltd. | Metal mold having a ceramic coating for forming sintered part |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1415522A (en) * | 1972-04-06 | 1975-11-26 | Lucas Industries Ltd | Method of manufacturing hot pressed cermaic material based on silicon nitride |
-
1985
- 1985-03-05 GB GB08505649A patent/GB2155843A/en not_active Withdrawn
- 1985-03-06 JP JP4452085A patent/JPS615905A/en active Pending
- 1985-03-06 NL NL8500635A patent/NL8500635A/en not_active Application Discontinuation
- 1985-03-06 FR FR8503980A patent/FR2560812A1/en not_active Withdrawn
- 1985-03-06 DE DE19853508007 patent/DE3508007A1/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1415522A (en) * | 1972-04-06 | 1975-11-26 | Lucas Industries Ltd | Method of manufacturing hot pressed cermaic material based on silicon nitride |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4915609A (en) * | 1987-10-16 | 1990-04-10 | Klevotec, Gesellschaft Fur Rechnergestutzte Systemanwendungen Gmbh Co. K.G. | Sintering device for blanks of foamable plastics with undercuts |
| US5092558A (en) * | 1987-11-10 | 1992-03-03 | Sumitomo Electric Industries, Ltd. | Metal mold having a ceramic coating for forming sintered part |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS615905A (en) | 1986-01-11 |
| DE3508007A1 (en) | 1986-02-06 |
| FR2560812A1 (en) | 1985-09-13 |
| GB8505649D0 (en) | 1985-04-03 |
| NL8500635A (en) | 1985-10-01 |
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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) |