GB2210377A - Microencapsulated flame retardant: encapsulated semiconductor - Google Patents

Microencapsulated flame retardant: encapsulated semiconductor Download PDF

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Publication number
GB2210377A
GB2210377A GB8722614A GB8722614A GB2210377A GB 2210377 A GB2210377 A GB 2210377A GB 8722614 A GB8722614 A GB 8722614A GB 8722614 A GB8722614 A GB 8722614A GB 2210377 A GB2210377 A GB 2210377A
Authority
GB
United Kingdom
Prior art keywords
flame retardant
substance
substance according
microencapsulant
microencapsulated
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Withdrawn
Application number
GB8722614A
Other versions
GB8722614D0 (en
Inventor
Martin Trevor Goosey
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Plessey Co Ltd
Original Assignee
Plessey Co Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Plessey Co Ltd filed Critical Plessey Co Ltd
Priority to GB8722614A priority Critical patent/GB2210377A/en
Publication of GB8722614D0 publication Critical patent/GB8722614D0/en
Publication of GB2210377A publication Critical patent/GB2210377A/en
Withdrawn legal-status Critical Current

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
    • H01L23/16—Fillings or auxiliary members in containers or encapsulations, e.g. centering rings
    • H01L23/18—Fillings characterised by the material, its physical or chemical properties, or its arrangement within the complete device
    • H01L23/24—Fillings characterised by the material, its physical or chemical properties, or its arrangement within the complete device solid or gel at the normal operating temperature of the device
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K9/00—Use of pretreated ingredients
    • C08K9/10—Encapsulated ingredients
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/28—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection
    • H01L23/29—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection characterised by the material, e.g. carbon
    • H01L23/293—Organic, e.g. plastic
    • 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

Abstract

A microencapsulated flame retardant material, preferably wherein the microencapsulant has a melting point substantially at or below the ignition temperature of the body to which it is providing flame retardancy. The toxic flame retardants can be isolated during normal conditions yet released in potentially hazardous conditions. The microencapulated material has a particular application to the method of encapsulating semiconductor devices e.g. with a plastic containing capsules of brominated resin and antimony oxide microencapsulated with polyethylene-terephthalate.

Description

A FLAME RETARDANT SUBSTANCE The present invention relates to a flame retardant substance and in particular, but not exclusively, to a flame retardant substance for protecting semiconductor devices.
It is well known in the art that flame retardants comprise materials which limit the applications to which they can be applied.
One application where flame retardants have hitherto been applied is for protecting plastic encapsulated semiconductor devices. The majority of semiconductor devices are encapsulated in plastic by a transfer moulding process using materials which are almost exclusively based on epoxide resin compounds. Unfortunately, these moulding compounds are inherently flammable and so flame retardants are introduced into their composition to ensure that the plastic encapsulated semiconductor device meets the flamability requirements. The flame retardant materials normally used comprise brominated resins and oxides of antimony. The degree of flame retardancy attainable improves with increasing the concentration of the materials. However, due to these materials, the reliability of the device decreases with increasing the concentration.
A major reliability problem associated with flame -retardants using epoxide resin compounds is the gold aluminium intermetallic formation at the interface between gold wire bonds and aluminium bond pads on the device surface. The formation of these gold aluminium intermetallics has been found to be exacerbated by the presence of bromine. Thereby indicating that since the flame retardant includes bromine, the presence of this flame retardant degrades the intermetallic bond. In fact, tests have shown that the bond wires of devices encapsulated with no flame retardant have lasted up to six times longer than those encapsulated with the flame retardant. Further reliability problems include the high temperature leakage current characteristics and a decrease of the thermal stability of the moulding compounds.Also the susceptibility to corrosion of the aluminium conductors on the device surface increases with increasing the concentration of the flame retardants in the moulding compounds.
Therefore, an aim of the present invention is to provide a flame retardant substance which alleviates the aforementioned problems and enables its use in new applications where previously flame retardants were unsuitable.
According to the present invention there is provided a substance for use as a flame retardant comprising a flame retardant material having been microencapsulated. The flame retardant material is preferably microencapsulated in a microencapsulant having a melting point substantially at or below the ignition temperature of a body to which it is providing flame protection.
The flame retardant material may comprise a composition of brominated resins and oxides of antimony.
The body to which the substance aims to provide fire protection may comprise a powder or a liquid such as paint.
Alternatively, the body may comprise a semiconductor device and the melting point of the microencapsulant may then be substantially at or above 1900C The microencapsulant may be a low melting point glass or polymer, preferably polythylene terephthalate.
In addition the present invention further provides a method of encapsulating a semiconductor device comprising a transfer moulding process incorporating a substance for use as a flame retardant.
By way of example, embodiments of the present invention will now be described.
The present invention provides a means of isolating a flame retardant material from contacting a body to which it is providing flame protection. Although the flame retardant material is isolated during normal conditions, at the elevated temperatures normally associated with ignition and burning the present invention further provides a means of releasing the flame retardant material. These two requisite means are achieved by microencapsulating the flame retardant material.
Microencapsulation is a process well known in the art, whereby a comminuted substance is enclosed in capsules. Normally the capsules are spherical and of only a few microns in diameter.
The flame retardant material is microencapsulated using a microencapsulant which maintains its integrity at temperatures found under normal conditions. However, the microencapsulant has a melting point which is substantially at or below the ignition temperature of the body to which it is applied. At hazardous temperatures, therefore, the microencapsulant melts, releasing the flame retardant material thereby providing flame protection to the body.
The present invention thus provides a controlled release of the flame retardant whilst facilitating its handling in normal conditions through isolation. Furthermore, the microencapsulant used is an inert material in order to prevent any interaction with the toxic flame retardant materials or the body to which flame protection is being - provided.
The preferred embodiment of the present invention relates to the use of the flame retardant substance for protecting semiconductor devices. Semiconductor devices are encapsulated in plastic usually using a transfer moulding process. The process uses moulding compounds which normally comprise organic and inorganic elements such as resins, curing agents, fillers, mould release additives, flow controllers and catalysts in proportions tailored to suit specific applications.
The microencapsulated flame retardant material is added to the moulding compounds in the same way as the flame retardants were introduced previously. This involves dry blending of all the elements followed by mixing at the molten stage in an extruder or by roll milling.
Once the moulding compound has been formulated, it can be used as before in the transfer moulding process.
The flame retardant material is microencapsulated in glass or polymeric spheres. Typically the temperatures experienced during the moulding process can be up to 1900 C. Thus the microencapsulant used must have a melting point above these temperatures yet sufficiently low so as to melt at temperatures prior to ignition.
Particularly suitable are low melting point glasses, polymers such as polyethylene terephthalate whose melting point is approximately 2660C and other engineering thermoplastics such as polyphenylene sulphide.
This semiconductor device encapsulated in a plastic which incorporates the microencapsulated flame retardant, provides the required flame retardancy and improved reliability.
Other embodiments of the present invention include the application of the flame retardant substance to paints and powder coatings. The method of applying this substance is further facilitated by the particulate and non-toxic characteristics of the substance.
The aforegoing description of the present invention has been given by way of example only, and it would be appreciated by a person skilled in the art that modifications may be made without departing from the scope of the present invention.

Claims (16)

1. A substance for use as a flame retardant comprising a flame retardant material having been microencapsulated.
2. A substance according to Claim 1 for providing flame protection to a body, in which the flame retardant material is microencapsulated in a microencapsulant having a melting point substantially at or below the ignition temperature of the body.
3. A substance according to Claim 1 or Claim 2, in which the flame retardant material comprises a composition of brominated resins and oxides of antimony.
4. A substance according to Claim 1 or Claim 2, in which the flame retardant material comprises brominated resins.
5. A substance according to any one of the preceding claims in which the body comprises a powder thereby enabling the substance to be distributed evenly throughout the powder.
6. A substance according to any one of Claims 1 to 4, in which the body comprises a liquid.
7. A substance according to Claim 6, in which the liquid comprises paint.
8. A substance according to any one of Claims 1 to 4, in which the body comprises a plastic encapsulated semiconductor device.
9. A substance according to Claim 8, in which the melting point of the microencapsulant is substantially at or above 190or.
10. A substance according to any one of the preceding claims in which the microencapsulant comprises a glass.
11. A substance according to any one of Claims 1 to 9, in which the microencapsulant comprises a polymer.
12. A substance according to Claim 11, in which the microencapsulant comprises polyethylene terephthalate.
13. A method of encapsulating a semiconductor device, comprising a transfer moulding process incorporating a substance for use as a flame retardant in accordance with any one of Claims 8 to 12.
14. An encapsulated semiconductor device, comprising a semiconductor device encapsulated in a plastic, in which the plastic includes a substance for use as a flame retardant in accordance with any one of Claims 8 to 12.
15. A substance substantially as hereinbefore described.
16. A method substantially as hereinbefore described.
GB8722614A 1987-09-25 1987-09-25 Microencapsulated flame retardant: encapsulated semiconductor Withdrawn GB2210377A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8722614A GB2210377A (en) 1987-09-25 1987-09-25 Microencapsulated flame retardant: encapsulated semiconductor

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8722614A GB2210377A (en) 1987-09-25 1987-09-25 Microencapsulated flame retardant: encapsulated semiconductor

Publications (2)

Publication Number Publication Date
GB8722614D0 GB8722614D0 (en) 1987-11-04
GB2210377A true GB2210377A (en) 1989-06-07

Family

ID=10624382

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8722614A Withdrawn GB2210377A (en) 1987-09-25 1987-09-25 Microencapsulated flame retardant: encapsulated semiconductor

Country Status (1)

Country Link
GB (1) GB2210377A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7585443B2 (en) 2004-05-20 2009-09-08 Albemarle Corporation Pelletized brominated anionic styrenic polymers and their preparation and use

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1270990A (en) * 1968-09-30 1972-04-19 Kalk Chemische Fabrik Gmbh Preparation of flameproof self-extinguishing moulding materials, moulded components, lacquers, films, sheets and coatings from plastics which are in themselves combustible
GB1390939A (en) * 1970-12-26 1975-04-16 Kanegafuchi Spinning Co Ltd Method for the properties of textile fibres and yarns and products obtained thereby
GB1526363A (en) * 1975-06-10 1978-09-27 Rhone Poulenc Ind Flameproofed plastics compositions
GB1532592A (en) * 1976-01-12 1978-11-15 Allied Chem Composition for encapsulating semiconductors
GB2009766A (en) * 1977-12-01 1979-06-20 Pietersen A Materials having fire alarming properties
GB2168707A (en) * 1984-12-17 1986-06-25 Sandoz Ltd Microcapsules for flameproofing polymeric material
WO1987000187A1 (en) * 1985-06-26 1987-01-15 Capsalarm S.A.R.L. Microincapsulated flame retarders

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1270990A (en) * 1968-09-30 1972-04-19 Kalk Chemische Fabrik Gmbh Preparation of flameproof self-extinguishing moulding materials, moulded components, lacquers, films, sheets and coatings from plastics which are in themselves combustible
GB1390939A (en) * 1970-12-26 1975-04-16 Kanegafuchi Spinning Co Ltd Method for the properties of textile fibres and yarns and products obtained thereby
GB1526363A (en) * 1975-06-10 1978-09-27 Rhone Poulenc Ind Flameproofed plastics compositions
GB1532592A (en) * 1976-01-12 1978-11-15 Allied Chem Composition for encapsulating semiconductors
GB2009766A (en) * 1977-12-01 1979-06-20 Pietersen A Materials having fire alarming properties
GB2168707A (en) * 1984-12-17 1986-06-25 Sandoz Ltd Microcapsules for flameproofing polymeric material
WO1987000187A1 (en) * 1985-06-26 1987-01-15 Capsalarm S.A.R.L. Microincapsulated flame retarders

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Chemistry and Industry 1985 p752-756 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7585443B2 (en) 2004-05-20 2009-09-08 Albemarle Corporation Pelletized brominated anionic styrenic polymers and their preparation and use
US8067088B2 (en) 2004-05-20 2011-11-29 Albemarle Corporation Pelletized brominated anionic styrenic polymers and their preparation and use

Also Published As

Publication number Publication date
GB8722614D0 (en) 1987-11-04

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Legal Events

Date Code Title Description
732 Registration of transactions, instruments or events in the register (sect. 32/1977)
WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)