Radiation control system

• US 6,097,019 A
• Filed: 08/05/1998
• Issued: 08/01/2000
• Est. Priority Date: 07/11/1990
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Hatzakis, Michael, Lewis, David Andrew, Shaw, Jane Margaret
• Primary Examiner(s): Hoang, Tu Ba
• Application Number:
  US09/129,708
• Time in Patent Office: 727 Days
• Field of Search: 219/702-712, 219/719, 219/720, 219/750
• US Class Current: 219/750
• CPC Class Codes: B01J 19/126 Microwaves
• CPC Class Codes: B01J 2219/00191 Control algorithm
• CPC Class Codes: G01N 22/00 Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more G01N3/00 - G01N17/00, G01N24/00 take precedence
• CPC Class Codes: H05B 2206/046 Microwave drying of wood, ink, food, ceramic, sintering of ceramic, clothes, hair
• CPC Class Codes: H05B 6/6402 Aspects relating to the microwave cavity
• CPC Class Codes: H05B 6/70 Feed lines
• CPC Class Codes: H05B 6/705 using microwave tuning
• CPC Class Codes: H05B 6/806 for laboratory use

Abstract

A control system for a blind microwave radiation tool a workpiece is described. The controlled system automatically tunes the cavity containing the workpiece. The control system automatically controls the temperature of the workpiece according to a predetermined temperature versus time schedule. Control system automatically determines when the workpiece has reached a particular predetermined physical condition. To achieve these results the control system automatically monitors applied power, reflected power or current temperature and automatically controls the microwave cavity volume and shape and launch structure including antennae location, cavity short location, cavity diameter, coupling loop position, etc. in order to maintain the cavity in resonance and to determine when to exit without operator intervention. Control system can run on a small computer or an embedded controller and is useful for automatically curing polyamic acid to polyimide to a predetermined percent cure, processing preimpregnated glass cloth in a continuous manner which can be used in circuit boards and drying and partial curing of web-like materials automatically without operator intervention.

Claims

1. A system for controlling the application of radiation to a workpiece in a cavity comprising:

time tracking means for tracking current times;

means for receiving an applied power signal indicative of a magnitude of an applied intensity of said radiation;

means for receiving a reflected power signal indicative of a magnitude of a reflected intensity of said radiation;

means for receiving a temperature signal indicative of a magnitude of a temperature of said workpiece;

minimizing means for causing α

to be less than a predetermined value and for providing a signal corresponding to a current value of one of said current times, wherein α

is the ratio of said magnitude of said reflected intensity over said magnitude of said applied intensity;

said minimizing means being coupled to said time tracking means, to said means for receiving said applied power signal indicative of said magnitude of said applied intensity, to said means for receiving said reflected power signal indicative of said magnitude of said reflected intensity and to said means for receiving said temperature signal indicative of said magnitude of said temperature of the workpiece;

temperature control means coupled to said time tracking means, for producing an intensity signal indicative of said magnitude of said applied intensity of said radiation to control said temperature of said workpiece to be substantially equal to a desired temperature;

means for determining when said workpiece has achieved a final determined physical condition;

said means for determining is coupled to said time tracking means; and

means for setting desired temperature based on current physical condition;

means for producing an end signal to end operation of said system when said workpiece has achieved said final predetermined physical condition;

said means for producing is coupled to said time tracking means.

2. The system of claim 1, further including, means for producing signals corresponding to said means for receiving said applied power signal indicative of said magnitude of the applied intensity of said radiation, said means for receiving said reflected power signal indicative of said magnitude of the reflected intensity of said radiation, and said means for receiving said temperature signal indicative of said magnitude of the temperature of said workpiece, for visual display on a visual display means.

3. The system of claim 1, wherein said minimizing means produces signals to control the location of a movable volume and a movable launch device in said cavity, said system comprising:

means for receiving a signal indicative of said current value of α

;

means for generating a position signal indicative of an updated location of one member of the group consisting of said launch device and said movable volume with respect to the position of said workpiece;

means for transmitting said position signal to said one member of the group consisting of said launch device and said movable volume until said current value of α

is at a local minimum;

when said local minimum is reached, said means for transmitting said position signal transmits said position signal to the other member of said group consisting of said launch device and said movable volume; and

when said current value of α

is less than said predetermined value, said current value of α

is minimized.

4. The system of claim 1, wherein said minimizing means produces signals to control the location of a movable volume and a movable launch device in said cavity in which they are situated, said system comprising:

means for receiving a signal indicative of said current value of α

;

means for generating a position signal indicative of an updated location of one member of the group consisting of said launch device and said movable volume with respect to the position of said workpiece;

means for transmitting said position signal to said one member of the group consisting of said launch device an said movable volume until said current value of α

is at a local minimum;

when said local minimum is reached, said means for transmitting said position signal transmits said position signal to the other member of said group consisting of said launch device and said movable volume; and

when said current value of α

is less than a predetermined value, said current value of α

is minimized.

5. The system according to claim 4 in which said movable launch device in said cavity is a movable antenna.

6. The system according to claim 4 in which said movable volume is achieved by a moving short.

7. The system of claim 1 wherein said temperature control means which controls said temperature to be substantially in agreement with a predetermined temperature versus time schedule, comprises:

temperature hold determining means for producing a temperature hold signal when said temperature is to be held constant in accordance with said schedule and for producing a temperature test signal when said temperature is not to be held constant according to said schedule;

temperature test means for receiving said temperature test signal and for producing a temperature duration signal when said temperature is greater than a next hold temperature according to said schedule and for producing a heating rate determine schedule when said temperature is not greater than said next hold temperature;

means for receiving said temperature duration signal and for producing a signal indicative of a temperature hold condition;

means for receiving said signal indicative of a temperature hold condition and for producing an initial time record signal;

means for receiving said initial time record signal and for receiving said temperature hold continue signal when said current time is in a region of said schedule indicative of holding said temperature constant and for producing a temperature hold discontinue signal when said current time is in a region of said schedule indicative of not holding said temperature constant;

means for receiving said temperature hold continue signal and for producing a temperature not correct signal when said temperature is different than indicated by said schedule for said current time and for producing a temperature desired signal when said temperature is not different from that indicated by said schedule for said current time;

means for receiving said temperature not correct signal and for increasing said applied intensity when said temperature is lower than that indicated by said schedule and for decreasing said applied intensity when said temperature is greater than that indicated by said schedule, and for producing a temperature equal to the desired signal and a heating rate determining signal;

means for receiving said heating rate determining signal and for determining a current heating rate and for producing a temperature rate compare signal;

means for receiving said temperature rate compare signal and for producing a temperature rate equal to an expected signal when said temperature rate is substantially equal to that indicated by said schedule for current time and for producing a temperature rate not equal to an expected signal when said temperature rate is not equal to that indicated by said schedule for said current time;

means for receiving temperature rate not equal to expected signal and for producing a signal indicative of increasing said intensity when said current heating rate is less than that indicated by said schedule for said current time and for producing a signal indicative of decreasing said intensity when said current heating rate is greater than indicated by said schedule fir said current time and for producing a second temperature rate equal to expected signal when said current heating rate is substantially equal to said current heating rate indicated by said schedule for said current time;

means for determining when said current time is substantially equal to an end time of said schedule and for receiving said temperature equal to desired signal and for receiving said temperature not different than desired signal and for receiving said temperature hold discontinue signal and for producing a schedule end signal when said current time is not less than said end time and for producing a schedule not ended signal when said current time is less than end time.

8. The system of claim 1, wherein said means for determining when said workpiece has achieved a final predetermined physical condition comprises:

resonant generating means in said cavity for generating a signal representative of a current Q value, said Q value being the ratio of a measure of energy stored in the cavity divided by an average power lost therein;

means for executing said minimizing means to return said α

value to a minimum;

means for determining from said current Q value and said current value whether said workpiece has achieved said predetermined physical condition.

9. The system of claim 1, wherein said means for determining when said workpiece has achieved a final predetermined physical condition is selected from the group comprising:

measuring dielectric properties of said workpiece, measuring degree of conversion of said workpiece, measuring residual solvent content, and measuring residual moisture content.

10. The system of claim 8, wherein said resonant generating means generates a signal to place said α

value in a nonminimized condition to determine said current Q value for said workpiece.

11. The system of claim 9, wherein said α

value in said non minimized condition is at a value of about 0.3.

12. The system according to claim 3 where said movable launch device in said cavity is an element selected from the group consisting of a movable antenna and a movable coupling loop.

13. A system according to claim 3 where said movable volume is a moving short.

14. The system of claim 1, wherein said means for determining when said workpiece has achieved a final predetermined physical condition comprises:

means for determining a current Q for said cavity said Q value being the ratio of the measure of energy stored in the cavity divided by the average power lost therein; and

means for comparing current Q and said temperature with a predetermined Q, temperature versus degrees of workpiece physical condition schedule.

15. The system of claim 1, wherein said minimizing means comprises:

means for generating a signal to modify said cavity to vary said current value of α

;

means for determining in response to said varied current value of α

if said current value of α

is increasing or decreasing; and

means for generating a signal in response to determination of whether said current value of α

is increasing or decreasing, for modifying said cavity to minimize said current value of α

.

16. The system of claim 1, wherein said temperature control means comprises:

means for receiving specific temperature values of said temperature signal corresponding to specific time values of said current time;

means for producing a heating rate signal in response to a heating rate from said specific temperature values and said specific time values;

means for producing a comparison signal in response to a heating rate from said specific temperature values and said specific time values;

means for producing a comparison signal in response to a heating rate signal with a predetermined temperature versus time schedule; and

means for producing a signal to modify said forward power signal in response to said comparison signals.

17. A system for controlling an application of radiation to a workpiece having a position in a cavity comprising:

time tracking means for tracking current time;

means for receiving a forward power signal indicative of a magnitude of an applied intensity of said radiation;

means for receiving a reflected power signal indicative of a magnitude of a reflected intensity of said radiation;

means for receiving a temperature signal indicative of a magnitude of a temperature of said workpiece;

minimizing means for causing α

to be less than a predetermined α

value, wherein α

is a ratio of said magnitude of said reflected intensity over said magnitude of said applied intensity and wherein a current value of α

corresponding to said current time;

said minimizing means being coupled to said timetracking means, to said means for receiving said applied power signal indicative of said magnitude of said applied intensity, to said means for receiving said reflected power signal indicative of said magnitude of said reflected intensity and to said means for receiving said temperature signal indicative of said magnitude of said temperature of said workpiece;

wherein said minimizing means is accomplished by moving movable volume element and movable launch device;

means for producing an intensity signal indicative of an intensity of said radiation to control said temperature to be substantially equal to a predetermined temperature;

means for determining when said workpiece has achieved a final predetermined physical condition; and

means for producing a signal to control said predetermined temperature if said workpiece has not achieved said final predetermined physical condition;

said minimizing means which produces signals to control a location of a short and an antenna in said cavity comprises;

means for receiving a signal indicative of a current value of α

;

means for generating a position signal indicative of an updated location of one member of the group consisting of said antenna and said short with respect to a position of said workpiece, said one member being a selected member and the other member being an unselected member;

means for transmitting said position signal indicative of an updated location to said one member of the group consisting of said antenna and said short until said current value of α

is at a local minimum;

when said local minimum is reached, said means for transmitting said position signal indicative of an updated location transmits said position signal indicative of an updated location to said unselected member of the group consisting of said movable volume element and said movable launch device;

when said current value of α

is less than said predetermined α

value, said current value of α

is minimized;

a temperature control means, which controls a temperature to be substantially in agreement with a predetermined temperature versus time schedule, comprises;

temperature hold determining means for producing a temperature hold signal when said temperature is to be held constant in accordance with said schedule and for producing a temperature test signal when said temperature is not to be held constant according to said schedule;

temperature test means for receiving said temperature test signal and for producing a temperature duration signal when said temperature is greater than a next hold temperature according to said schedule and for producing a heating rate determine signal when said temperature is not greater than said next hold temperature;

means for receiving said temperature duration signal and for producing a signal indicative of a temperature hold condition;

means for receiving said signal indicative of a temperature hold condition and for producing an initial time record signal;

means for receiving said initial time record signal and for receiving said temperature hold signal and for producing a temperature hold continue signal when said current time is in a region of said schedule indicative of holding said temperature constant and for producing a temperature hold discontinue signal when said time is in a region of a schedule indicative of not holding said temperature constant;

means for receiving said temperature hold continue signal and for producing a temperature different than desired signal when said temperature is different than indicated by said schedule for said time and for producing a temperature not different than desired signal when said temperature is not different than desired;

means for receiving said temperature different than desired signal and for increasing said applied intensity when said temperature is lower than that indicated by said schedule indicative of not holding said temperature constant and for decreasing said intensity when said temperature is greater than when indicated by said schedule;

indicative of not holding said temperature constant, and for producing a temperature equal to desired signal;

means for receiving said heating rate determining signal and for determining a current heating rate and for producing a temperature rate compare signal,

means for receiving said temperature rate compare signal and for producing a temperature rate equal to expected signal when said temperature rate is substantially equal to that indicated by said schedule for said current time and for producing a temperature rate not equal to expected signal when said temperature rate is not equal to that indicated by said schedule for said current time;

means for receiving said temperature rate not equal to expected signal and for producing a signal indicative of increasing said intensity when said heating rate is less than indicated by said schedule for said current time and for producing a signal indicative of decreasing said intensity when said heating rate is greater than indicated by said schedule for said current time and for producing a second temperature rate equal to expected signal when said temperature rate is substantially equal to said rate indicated by said schedule for said time; and

means for determining when said current time is substantially equal to an end time of said schedule and for receiving said temperature equal to desired signal and for receiving said temperature not different than desired signal and for receiving said temperature hold discontinue signal and for producing a schedule end signal when said current time is not less than said end time and for producing a schedule not ended signal when said current time less than said end time;

said means for determining when said workpiece has achieved a final predetermined physical condition comprises;

means for generating a signal to place said a value in a non minimized condition to determine a current Q value for said workpiece said Q value being the ratio of the measure of energy stored in the cavity divided by the average power lost therein;

means for executing said α

minimizing means to return said a value to a minimum;

means for determining from said current Q value and said current temperature whether said workpiece has achieved said predetermined physical condition wherein said Q is the ratio of energy stored to energy lost in said cavity.

18. A system for controlling an application or radiation to a workpiece in a cavity comprising:

time tracking means for tracking current time;

means for receiving an applied power signal indicative of the applied intensity of said radiation;

means for receiving a reflected power signal indicative of a magnitude of a reflected intensity of said radiation;

means for receiving a temperature signal indicative of a magnitude of a temperature of said workpiece;

a minimizing means coupled to said time tracking means for causing α

to be less than a predetermined value, wherein α

is a ratio of said magnitude of said reflected intensity over said magnitude of said applied intensity;

said minimizing means being coupled to said timetracking means, to said means for receiving said applied power signal indicative of said magnitude of said applied intensity, to said means for receiving said reflected power signal indicative of said magnitude of said reflected intensity and to said means for receiving said temperature signal indicative of said magnitude of said temperature of said workpiece;

temperature control means for producing an intensity signal indicative of a magnitude of an intensity of said radiation to control said temperature to be substantially equal to a predetermined temperature from a predetermined temperature versus time schedule;

means for determined when said workpiece has achieved a final predetermined physical condition, said means for determining is operatively connected to said time tracking means;

means for producing a signal to modify predetermined temperature if said workpiece has not achieved said final predetermined physical condition, said means for producing is operatively connected to said time tracking means;

said minimizing means comprises;

means for generating a signal to modify said cavity to vary a value of α

;

means for determining in response to said varying said value of α

if said value of α

is increasing or decreasing; and

means for generating a signal in response to a determination of whether said current value of α

is increasing or decreasing, for modifying said cavity to minimize said current value of α

;

means for varying position of variable launch device and movable volume element which are located in said cavity;

said temperature control means comprises;

means for receiving specific temperature values of said temperature signal corresponding to specific time values of said current time;

means for producing a heating rate signal in response to determining a heating rate from said specific temperature values and said specific time values;

means for producing a comparison signal in response to comparing said heating rate signal with said predetermined temperature versus time schedule; and

means for producing a signal to modify said applied power signal indicative of the applied intensity in response to said comparison signal;

said means for determining when said workpiece has achieved a final predetermined physical condition comprises;

means for determining a current Q for said cavity wherein said current Q; and

means for comparing said current Q and said current temperature with a predetermined Q, and temperature versus degree of workpiece physical condition schedule wherein said Q is the ratio of energy stored to energy lost in said cavity.

19. A method for controlling the application of radiation to a workpiece in a cavity comprising:

using time tracking means to track current time;

measuring a forward radiation intensity applied to said workpiece at said current time;

measuring a reflected radiation intensity reflected from said workpiece at said current time;

minimizing α

, wherein α

is a ratio of a magnitude of reflected radiation intensity over a magnitude of a forward radiation intensity and wherein α

has a current value corresponding to said current time;

measuring a temperature of said workpiece at said current time;

controlling said temperature to be substantially equal to a predetermined temperature from a temperature versus time schedule;

determining when said workpiece has achieved a final predetermined physical condition; and

stopping said applied intensity when said workpiece has achieved said final predetermined physical condition;

varying said forward radiation intensity when said workpiece has not achieved said final predetermined condition so as to achieve predetermined physical condition;

said step of minimizing α

comprises;

modifying said cavity to vary said current value of α

;

determining in response to said varying said current value of α

, if said current value of α

is increasing or decreasing ; and

modifying said cavity to minimize said current value of α

said step of controlling said current temperature comprises;

monitoring specific temperature values corresponding to specific time values;

determining a heating rate from said specific temperature values and said specific time values;

comparing said heating rate with said predetermined temperature versus time schedule; and

,

modifying said forward radiation intensity in response to said step of comparing said heating;

said step of determining when said workpiece has achieved a final predetermined physical condition comprises;

determining a current Q value for said cavity, said Q value being the ratio of the measure of energy stored in the cavity divided by the average power lost therein; and

comparing the current Q and said current temperature with a predetermined Q, and temperature versus degree of workpiece physical condition schedule.