US4468411A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for providing alpha particle protection for an integrated circuit die
Assignee: Motorola Solutions Inc
•
Filing: 1982-04-05
•
Granted: 1984-08-28
•
Expires: 2002-04-05
Abstract
Abstract A controlled quantity of a liquid polyimide precursor compound is deposited on the active surface of an integrated circuit die which has been prepared for packaging, and thereafter cured using a two step curing process to develop a polyimide coating of sufficient thickness to provide alpha particle protection for the die once packaged.
Inventors
- 👤 James W. Sloan
- 👤 Truoc T. Tran
- 👤 Frank T. Jones, III
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 12:12
CPC Classifications
H; H10; H10P; H10P14/00; H10P14/60; H10P14/68; H10P14/683; H10P14/63; H10P14/6326; H10P14/6342; H10P14/65; H10P14/6516; H10P14/6529; H10W; H10W42/00; H10W42/20; H10W42/25; H10W72/00; H10W72/50; H10W72/541; H10W72/5449; Y; Y10; Y10S; Y10S438/00; Y10S438/953
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
146 words
A method for providing alpha particle protection for an integrated circuit die which has been mounted for packaging and electrically connected to conductor leads integral with such packaging, comprising the steps of: depositing a selected quantity of a liquid polyimide precursor compound having a predetermined solids content and viscosity on the active surface of the die to form a liquid polyimide precursor coating thereon; curing the coating for a first time period at a first temperature selected to reduce the volatile content thereof below a predetermined level, and for a second time period at a second temperature selected to substantially complete the imidization thereof and the removal of the remaining volatile content thereof; and substantially immediately prior to packaging the coated die, dehydrating the coating for a third time period at a third temperature selected to remove moisture absorbed by the coating since the curing thereof.
Claim 2
Independent Claim
146 words
A method for providing alpha particle protection for an integrated circuit die which has been mounted for packaging and electrically connected to conductor leads integral with such packaging, comprising the steps of: depositing a selected quantity of a liquid polyimide precursor compound having a predetermined solids content and viscosity on the active surface of the die to form a liquid polyimide precursor coating thereon; curing the coating for a first time period at a first temperature selected to reduce the volatile content thereof below a predetermined level, and for a second time period at a second temperature selected to substantially complete the imidization thereof and the removal of the remaining volatile content thereof; and substantially immediately prior to packaging the coated die, dehydrating the coating for a third time period at a third temperature selected to remove moisture absorbed by the coating since the curing thereof.
Claim 3
Dependent Claim
45 words
The method of claim 1 wherein the step of curing the coating for a first time period is performed at a first temperature selected to reduce the volatile content thereof below said predetermined level sufficiently slowly to preclude the formation of significant gas bubbles therein.
Claim 4
Dependent Claim
27 words
The method of claim 2 wherein said first time period comprises until at least about 95% of the solvent content of said coating has been driven off.
Claim 5
Dependent Claim
54 words
The method of claim 1 or 2 further including the step of: inspecting the die and the coating thereon after the curing thereof to identify any significant mechanical defects in the die and coating; and wherein the step of dehydrating the coating is performed after the inspection of the die and the coating thereon.
Claim 6
Dependent Claim
64 words
The method of claim 1 or 2 wherein the step of depositing said selected quantity of said liquid polyimide precursor compound comprises the steps of: subjecting to a substantially constant, predetermined pressure a quantity of said liquid polyimide precursor compound; and directing for a fourth predetermined length of time a portion of said compound through a conduit of predetermined cross-sectional area onto said surface.
Claim 7
Dependent Claim
51 words
The method of claim 5 including the further step of: periodically dispensing one of said portions of said compound into a length of tubing of predetermined cross-sectional area and verifying that the resulting length of the column of said compound in said tubing is substantially equal to a predetermined gauge length.
Claim 8
Dependent Claim
20 words
The method of claim 1 or 2 wherein said first temperature is selected between about 100° C. and 150° C.
Claim 9
Dependent Claim
29 words
The method of claim 1 or 2 wherein said second temperature is selected between about 250° C. and 450° C., and preferably, between about 300° C. and 350° C.
Claim 10
Dependent Claim
22 words
The method of claim 1 or 2 wherein the step of curing the coating is performed in a flow of dry nitrogen.
Claim 11
Dependent Claim
22 words
The method of claim 1 or 2 wherein the step of dehydrating the coating is performed in a flow of dry nitrogen.
Claim 12
Dependent Claim
31 words
The method of claim 1 or 2 wherein the liquid polyimide precursor compound has a solids content between about 20 and 30 percent, and preferably between about 24 and 27 percent.
Claim 13
Dependent Claim
26 words
The method of claim 1 or 2 wherein the liquid polyimide precursor compound has a viscosity of the order of between about 75 and 200 centipoise.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-08-28 | 1988-02-27 | 1988-08-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-08-28 | 1992-02-27 | 1992-08-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-08-28 | 1996-02-27 | 1996-08-28 | $7700.00 | Window Closed / Lapsed |