US3600553A

US3600553A - Method and apparatus for heating a plurality of closely spaced discrete zones by a single energy source

Info

Publication number: US3600553A
Application number: US858291A
Authority: US
Inventors: Bernard J Costello
Original assignee: Argus Engineering Co Inc
Current assignee: Argus International
Priority date: 1969-09-16
Filing date: 1969-09-16
Publication date: 1971-08-17
Anticipated expiration: 1988-08-17

Abstract

Radiant energy heating apparatus for heating a plurality of discrete, closely spaced zones through the use of a single radiant energy source. The radiant energy is focused upon the discrete zones by a reflector assembly of elliptical shape which is split at its apex into at least two halves, which halves are rotated relative to one another by an amount sufficient to locate the resulting plurality of focal points coincident with the zones being heated.

Description

United States ate nt [72] Inventor Bernard J. Costello Rlngoes, NJ.

[21] Appl. No. 858,291

22 1 Filed Sept. 16, 1969 [45] Patented Aug. 17, 1971 [73] Assignee Argus Engineering Co., Inc.

Hopewell, NJ.

[54] METHOD AND APPARATUS FOR HEATING A PLURALITY OF CLOSELY SPACED DISCRETE ZONES BY A SINGLE ENERGY SOURCE 9 Claims, 4 Drawing Figs.

[52] US. Cl 219/348,

[51] Int. Cl H05b 1/00,

A F2411 9/02 [50] Field of Search 219/347, 348, 349, 85; 350/296; 240/4137, 44.1, 103

[56] References Cited UNITED STATES PATENTS 2,354,658 8/1944 Barber 219/349 2,771,001 11/1956 Gretener 350/296 3,099,403 7/1963 Strawick.... 219/348 3,169,709 2/1965 Goodbar 240/103 3,457,386 7/1969 Costello 219/349 3,469,061 9/ 1969 Costello 219/85 OTHER REFERENCES Projectionist Vol. 25, issue 12, pages 24 & 25, published Dec. 1950 Primary Examiner-J. V. Truhe Assistant Examiner-L. H. Bender Attorney-Ostrolenk, Faber, Gerb & Sotfen METHOD AND APPARATUS FOR HEATING A PLURALITY F CLOSELY SPACED DISCRETE ZONES BY A SINGLE ENERGY SOURCE The present invention relates to heating apparatus and more particularly to a novel method and apparatus for heating a plurality of discrete closely spaced zones through the use of a single radiant energy source.

Conventional focused radiant heating systems, for example, of the' type described in copending application Ser. No. 561,1 l2 filed June 28, 1966 by the instant inventor, now US. Pat. 3,469,061, issued Sept. 23, 1969, are typically comprised of an energy source positioned at the primary focus of an elliptical reflector. The region of the device being heated is positioned at the focal point of the reflector which produces an image which is approximately of the size and shape of the energy source. All prior art systems to date have been capable of producing only one image, which systems hereinafter will be referred to as single image systems.

There exist a number of applications wherein it is desired to heat two or more discrete areas which lie in close proximity to one another. in order to employ single image systems for such applications it becomes necessary to irradiate both of the discrete areas which are desired to be heated, as well as the intervening area lying between the two desired areas. in many instances, heat sensitive elements may be positioned within the intervening area resulting in damage or destruction of such heat-sensitive elements as a result of the irradiation. in order to prevent irradiation in such intervening areas, it becomes necessary to provide a mask to protect the intervening area. Such masking devices are described in the above-mentioned copending application.

An alternative method of irradiating two or more discrete, closely spaced areas consists of positioning the single image system so as to form an image satisfactory for irradiating one of the two areas desired to be irradiated and then moving the single image system by an amount sufficient to irradiate the second discrete area.

Still another method for irradiating two discrete, closely spaced areas is that in which an image system employing a simple reflector and two radiant energy sources. Whereas the system has been found to produce two images, it was nevertheless found to exhibit several significant disadvantages, namely:

1. The sources cannot be placed at the true focus of the reflector in the case where the reflector has an elliptical configuration;

2. The spacing between the radiant energy sources, and therefore the minimum spread of the images was found to be limited by the diameter of the radiant energy source envelopes;

3. The fact that the source cannot be placed precisely at the primary focus resulted in poor resolution and distortion in the image;

4. The radiant energy sources, when positioned in close proximity to one another are caused to overheat, thereby seriously affecting their operation and reliability.

The disadvantages of the above-mentioned approaches are overcome by means of a novel imaging system (hereinafter referred to as a multi-image system) characterized by its capability of producing two or more distinct closely spaced images through the use of a single radiant energy source.

The present invention is comprised of a radiant energy source which may, for example, be an elongated filament heater whose central axis is positioned substantially in alignment with the primary focus of 'a highly polished elliptical reflector. The reflector is cut or otherwise separated at its apex, thereby forming two reflector halves." The reflector halves are then rotated so that the furthest removed edges are still further separated from one another to produce respective focal points or images which are separated from one another by an amount commensurate with the spacing between the discrete zones which are to be heated. Three discrete closely spaced focal points may be obtained by cutting or otherwise separating the elliptical-shaped reflector in two discrete locations and rotating each of the resulting sections by amounts commensurate with the spacing between the three zones to be heated.

The resulting multi-image system is characterized by providing several important advantages being, among others 1. enabling the attachment of leads to opposite edges of heat sensitive ceramic substrates without damaging the substrates;

2. attachment of leads to devices having axially aligned leads where a multiple number of such devices are to be soldered simultaneously;

3. applique soldering of large profile integrated circuits (also referred to as dual in line" packages) to printed circuitboards or similar surfaces;

4. any application requiring more than one area to be heated where the discrete areas are too close together to permit more than one system to be used.

it is, therefore, one primary object of the present invention to provide a novel, multi-image system for heating discrete, closely spaced areas through the use of a single radiant energy source.

Another object of the present invention is to provide novel means for heating discrete, relatively closely spaced areas through the use of a single radiant energy source in which the radiant energy is focused by a plurality of elliptical-shaped reflector sections each being aligned so as to focus the radiant energy at respective focal points which are spaced to coincide with the discrete, closely spaced regions to be heated.

These as well as other objects of the present invention will become apparent when reading the accompanying description and drawings in which:

FIGS. 1a and lb are perspective views showing two types of devices which may be joined to peripheral circuitry through the apparatus of the present invention;

FIG. 2 is a diagrammatic view of the multi-image system of the present invention showing the manner in which the multiimage system is derived from a single image system; and

FIG. 3 shows another preferred embodiment of the multiimage system of FIG. 2.

FIG. 1 shows a large profile integrated circuit 10 which is comprised of a main body 11 having a plurality of leads 12 projecting outwardly from the body 11 for connection to peripheral circuitry through the conductive coatings 13, each associated with one of the terminals 12 and which may, for example, be provided upon an insulating substrate 14 of a printed circuitboard. The outermost ends of the terminals 12 may be aligned generally horizontally, as shown at 120, so as to rest upon one of the associated conductive coatings 13 provided upon the printed circuit insulating substrate 14.

The large profile integrated circuit body 11 is preferably formed of a suitable insulating material and has encapsulated therein an integrated circuit which may be comprised of a number of active and/or passive elements such as, for example, semiconductor devices and impedance devices, respectively. It is most preferable that the leads extending from opposite sides of the integrated circuit body 11 be simultaneously soldered to the associated conductive coatings in a single soldering operation.

The single image systems presently in use may be adjusted to focus radiant energy over the entire region occupied by the integrated circuit body 11, the leads 12 and the regions of the conductive coatings 13 engaged by the ends 12a of the leads. Although this will enable simultaneous soldering of all of the leads on the opposite sides of the circuit body 11, the circuit body will also be irradiated, causing undue heating and damage or even destruction of the integrated circuit components housed therein, thereby necessitating the use of a masking means for shielding the body 11 against the radiant energy. Alternatively the leads on one side of body 11 may be irradiated and the single image system is then moved relative to the body 11 to irradiate the remaining leads on the opposite side of body 1 l.

FIG. 1b shows another typical circuit structure which may be soldered to associated leads through the use of the present invention. The assembly 20 of FIG. lb is comprised of a ceramic substrate 23 having a circuit deposited upon its surface and being provided with a plurality of terminal pads 24 along the opposite edges thereof. A pair of

lead assemblies

25 and 26 each provided with a plurality of spaced substantially parallel leads 27 and 28, respectively, are arranged relative to the ceramic substrate 23 so that their free ends are each aligned above an associated terminal pad 24 provided along opposite edges of the ceramic substrate. After completion of the soldering operation, the main body portions of the

assemblies

25 and 26 may be cut away from the leads along the phantom lines 29 and 30, enabling each of the groups of

leads

27 and 28 to be subsequently connected to peripheral circuitry. Soldering of the groups of

leads

27 and 28 to the terminal pads 24 in a simultaneous operation may be performed by conventional single image systems which would result in exposure of the entire ceramic substrate and the circuitry deposited thereon to radiant energy. It would again be neces sary to provide masking means for shielding the highly heatsensitive circuit deposited upon the ceramic substrate against the radiant energy, or alternatively require two separate heating operations.

It should be understood that the above-described circuit devices are merely exemplary of the types of devices which may be joined to peripheral circuitry through the present invention wherein the basic objective is to irradiate discrete, closely spaced zones with radiant energy without exposing the intervening regions to high levels of radiant energy. I

The single image system shown in FIG. 2 is comprised of a source and an elliptical-shaped reflector. The source is positioned at the primary focal point f of the reflector whose contour is represented by the elliptical shaped curve AOB. The reflector comprises that portion of an imaginary ellipse which lies to one side of the minor diameter represented by dotted line 37. Typically, the reflector is an elongated member of ellipticalshape cross section in which the concave surface (i.e., the surface confronting the radiant energy source) is highly reflective. The radiant energy source may, for example, be an elongated or long line" filament lamp extending approximately the length of the reflector having its longitudinal axis coincident with the primary focus of the reflector represented by the point f,. The radiation may typically lie in the infrared range. With this arrangement, radiation emitted from the energy source and striking the reflector is reflected, and impinges upon the secondary focus f of the elliptical'reflector. Typically, the image produced by the reflector at the secondary focal point f is approximately of the size and shape of the energy source. The joining operation is performed by positioning the associated leads of the devices being joined in the immediate region of the secondary focus, usually by positioning the devices upon a supporting surface.

Designating the apex of the elliptical reflector as point the portions to the left and right of the apex as sections A0 and OB, respectively; the incident rays on each side as a and b, respectively; and the reflected rays as a and b, respectively, the reflector is cut or otherwise separated at the apex O and the resulting sections A0 and OB oi the reflector are rotated clockwise and counterclockwise, respectively, to positions A'O and B'O through angles 6, and 0 which angles are defined by the line segments ffand f f f respectively. As a result of this rotation, two new focal points, f and f are produced.

With this configuration, two images of the source are produced, which images are capable of heating two distinct areas arranged in close proximity to one another. Obviously, the angles of rotation are chosen so that the resulting pair of focal points will be aligned with the two discrete regions being irradiated.

After rotation of the reflector sections A0 and OB, respectively, the adjacent edges of the reflector sections located in the vicinity of the apex 0 may he rejoined so as to form a substantially continuous reflector assembly. Alternatively, the

reflector sections may be mechanically joined to pivotally mounted brackets 31 and 32 arranged to pivot about

points

33 and 34, respectively, to facilitate rotation of the reflector sections through the desired angles. The pivotal connections may be slidably mounted within

guide channels

35 and 36, respectively, so as to enable the reflector sections to be moved toward one another or away from one another, substantially in a horizontal direction, if desired. It should further be noted that the angles of rotation experienced by the reflector sections need not be equal and may preferably be varied to produce any displacement c from the simple focus f which may be required.

An extension of the embodiment of FIG. 2 to three or more images is also possible. For example, FIG. 3 shows an embodiment capable of irradiating three relatively closely spaced, discrete zones in which the reflector is divided into sections AB, BC and CD, respectively. In one example, with the radiant energy source located at the primary focus f,, the reflector section BC may be held stationary so that the ray a from source f, will be reflected as ray a and thereby be collected at the secondary focal point f the reflector section AB may be rotated to the position represented by the dotted line AB' causing ray b to be reflected downwardly as reflected ray b' to impinge upon a surface in the immediate region of the secon dary focal point f and the reflector section CD is rotated to the position represented by dotted line C'D to cause rays such as the ray 0 from source j to be reflected as ray c which is directed to the third focal point f It should be noted that the angles through which the reflective sections AB and CD are rotated need not be equal to one another. In addition thereto, whereas the embodiment of FIG. 3 has been described such that the reflector section BC is held stationary while the remaining two sections are rotated, it should be understood that all three of the sections may be rotated independently of one another, depending only upon the relative spacing between the three zones to be irradiated, which result is accomplished by alignment of the image focal points f f and f The concept described herein may be further extended to develop more than three images.

The total available energy at each image is less than that which would be available in a single image system. For example, the energy available in each zone of a dual image system is equal to one-half the energy available in the single zone of a single image system. Similarly, the energy available at each zone of a three-image system is equal to one-third the energy available in the single zone of a single image system. To compensate for this, it is possible to employ an energy source capable of generating a greater magnitude of energy than energy sources employed in conventional single image systems or, alternatively, to increase the time periods during which the elements being joined are irradiated.

It can be seen from the foregoing description that the present invention provides a novel multiple image radiant heating system capable of heating discrete relatively closely spaced zones simultaneously through the use of a single radiant energy source. The advantages derived from this system are, among others:

I. The ability to heat multiple zones allows the use of more simple locating devices for the workpiece and a significant reduction in the mechanisms required to position and/or move the heating system.

2. Since the multiple zones may be heated simultaneously the elapsed time of the heating operation is significantly shorter than conventional methods in which the zones are successively heated, resulting from the fact that the transfer time between the heating of successive zones is completely eliminated.

3. Screens or masks which would otherwise be required to shield those regions between adjacent zones being heated are no longer necessary.

Devices having a plurality of leads on opposite sides thereof may be either joined (i.e., soldered) or desoldered in a single operation, thus facilitating the assembly and repair, respectively, of such devices without damage.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims. I

I claim:

' 1. Apparatus including only a single radiation source and a single reflector assembly for irradiating a plurality of discrete closely spaced areas separated by intervening regions for which irradiation is to be avoided comprising:

asource of radiant energy;

a single reflector assembly comprised of a plurality of reflector sections;

each of said sections having a predetermined curvilinear cross section and being arranged adjacent to one another to define a single curved line partially surroundingsaid source;

the concave surfaces of said sections being highly reflective;

said sections sharing a common focal point;

said source of radiant energy being positioned at the common focal point to direct rays of radiant energy upon the concave reflective surfaces of all of said reflector sections;

said reflector sections each being aligned relative to said energy source and having a cross-sectional configuration adapted to direct radiation reflected therefrom to a different one of the discrete areas and thereby substantially reduce the radiant energy impinging in the regions lying between said discrete areas,-the radiation being reflected from each of said reflector sections being separated in the region between the reflector sections and the irradiated areas.

2. The apparatus of claim 1 wherein said reflector sections each have a curvilinear cross section which defines adifferent portion of the same ellipse,

3. The apparatus of claim -2 wherein said reflector sections are rotatably mounted independently of one another and arranged to rotate about the common focal point coincident with the center of said radiant energy source to permit displacement of the focal images of such section to increase the separation distance between their focal images and align the focal images to coincide with an associated one of the discrete areas to be irradiated.

4. Apparatus for simultaneously irradiating the leads of a circuit body which are arranged in first and second groups on opposite sides of the circuit body comprising:

a reflector assembly comprised of first and second reflector sections each having a cross-sectional configuration of elliptical contour, said sections being aligned to share a common primary focal point;

the concave surfaces of said sections being highly reflective;

a source of radiant energy coincident with the common primary focal point to direct rays of said radiant energy upon the reflective surfaces of said reflector sections;

said reflector sections each being positioned relative to said energy source to direct radiant energy reflected from said sections toward associated focal images which are separated from one another by a distance substantially equal to the distance between the groups ofleads extending from opposite sides of said circuit body whereby the reflected rays of radiant energy irradiate said groups of leads and the circuit body lies in the area between said focal images so as to be relatively free of radiant energy.

5. Apparatus for heating a plurality of discrete closely spaced areas comprising:

a reflector assembly comprised of a member having a cross section configuration which defines that portion of an ellipse, which portion lies on one side of the minor diameter;

said member being divided into a plurality of sections;

the concave surfaces of said sections being highly reflective;

a source of radiant energy substantially coincident with the focal point of said ellipse closest to said reflector sections to direct radiant energy upon the concave reflective surfaces of all of said reflector sections; said reflector sections being selectively positioned relative to the imaginary ellipse to focus rays of radiant energy impinging upon said reflective surfaces at different image focal points wherein the selected positions are chosen to cause each image focal point to coincide with an associated one of said discrete areas and whereby the regions between said discrete areas are relatively free of radiant energy.

6. The apparatus of claim 5 wherein said energy source is comprised of means for generating infrared rays.

7. The apparatus of claim 5 being further comprised of means for rotatably mounting each of said reflector sections to permit independent rotational movement of said reflector sections for adjustably varying the displacement between and among said image focal points.

8. Apparatus for simultaneously irradiating all of the leads of a circuit body which are arranged in first and second groups on opposite sides of the circuit body comprising:

a reflector assembly comprised of an elongated member having a cross section configuration which defines that portion of an ellipse, which portion lies on one side of the minor diameter;

said member being divided into first and second sections;

the concave surfaces of said sections being highly reflective;

a line source of radiant energy having its longitudinal axis coincident with the focal point of said ellipse closest to said reflector sections to direct radiant energy upon the concave reflective surfaces of all of said reflector sections;

said reflector sections being selectively positioned to focus rays of radiant energy impinging upon said reflective surfaces at first and second image focal regions respectively wherein the selected positions are chosen to align each image focal region with an associated one of said first and second groups of leads and whereby the circuit body is relatively free of radiant energy.

9. A method for heating two discrete zones along a surface, which zones are arranged at spaced intervals from one another so as to define an intervening space therebetween, comprising the steps of:

providing an omnidirectional source of radiant energy;

collecting a portion of the energy directed away from said surface and focusing the collected radiation upon one of said zones;

collecting a second portion of the energy directed away from said surface and focusing the collected radiation upon the remaining one of said zones whereby the focused radiant energy portions do not overlap one another and whereby the intervening region between said discrete zones is exposed to a level of radiation significantly less than the radiant energy irradiating said discrete zones.

Claims

1. Apparatus including only a single radiation source and a single reflector assembly for irradiating a plurality of discrete closely spaced areas separated by intervening regions for which irradiation is to be avoided comprising: a source of radiant energy; a single reflector assembly comprised of a plurality of reflector sections; each of said sections having a predetermined curvilinear cross section and being arranged adjacent to one another to define a single curved line partially surrounding said source; the concave surfaces of said sections being highly reflective; said sections sharing a common focal point; said source of radiant energy being positioned at the common focal point to direct rays of radiant energy upon the concave reflective surfaces of all of said reflector sections; said reflector sections each being aligned relative to said energy source and having a cross-sectional configuration adapted to direct radiation reflected therefrom to a different one of the discrete areas and thereby substantially reduce the radiant energy impinging in the regions lying between said discrete areas, the radiation being reflected from each of said reflector sections being separated in the region between the reflector sections and the irradiated areas.

2. The apparatus of claim 1 wherein said reflector sections each have a curvilinear cross section which defines a different portIon of the same ellipse.

3. The apparatus of claim 2 wherein said reflector sections are rotatably mounted independently of one another and arranged to rotate about the common focal point coincident with the center of said radiant energy source to permit displacement of the focal images of such section to increase the separation distance between their focal images and align the focal images to coincide with an associated one of the discrete areas to be irradiated.

4. Apparatus for simultaneously irradiating the leads of a circuit body which are arranged in first and second groups on opposite sides of the circuit body comprising: a reflector assembly comprised of first and second reflector sections each having a cross-sectional configuration of elliptical contour, said sections being aligned to share a common primary focal point; the concave surfaces of said sections being highly reflective; a source of radiant energy coincident with the common primary focal point to direct rays of said radiant energy upon the reflective surfaces of said reflector sections; said reflector sections each being positioned relative to said energy source to direct radiant energy reflected from said sections toward associated focal images which are separated from one another by a distance substantially equal to the distance between the groups of leads extending from opposite sides of said circuit body whereby the reflected rays of radiant energy irradiate said groups of leads and the circuit body lies in the area between said focal images so as to be relatively free of radiant energy.

5. Apparatus for heating a plurality of discrete closely spaced areas comprising: a reflector assembly comprised of a member having a cross section configuration which defines that portion of an ellipse, which portion lies on one side of the minor diameter; said member being divided into a plurality of sections; the concave surfaces of said sections being highly reflective; a source of radiant energy substantially coincident with the focal point of said ellipse closest to said reflector sections to direct radiant energy upon the concave reflective surfaces of all of said reflector sections; said reflector sections being selectively positioned relative to the imaginary ellipse to focus rays of radiant energy impinging upon said reflective surfaces at different image focal points wherein the selected positions are chosen to cause each image focal point to coincide with an associated one of said discrete areas and whereby the regions between said discrete areas are relatively free of radiant energy.

8. Apparatus for simultaneously irradiating all of the leads of a circuit body which are arranged in first and second groups on opposite sides of the circuit body comprising: a reflector assembly comprised of an elongated member having a cross section configuration which defines that portion of an ellipse, which portion lies on one side of the minor diameter; said member being divided into first and second sections; the concave surfaces of said sections being highly reflective; a line source of radiant energy having its longitudinal axis coincident with the focal point of said ellipse closest to said reflector sections to direct radiant energy upon the concave reflective surfaces of all of said reflector sections; said reflector sections being selectively positioned to focus rays of radiant energy impinging upon said reflective surfaces at first and second image focal regions respectively wherein the selected positions are chosen to align each image focal region wIth an associated one of said first and second groups of leads and whereby the circuit body is relatively free of radiant energy.

9. A method for heating two discrete zones along a surface, which zones are arranged at spaced intervals from one another so as to define an intervening space therebetween, comprising the steps of: providing an omnidirectional source of radiant energy; collecting a portion of the energy directed away from said surface and focusing the collected radiation upon one of said zones; collecting a second portion of the energy directed away from said surface and focusing the collected radiation upon the remaining one of said zones whereby the focused radiant energy portions do not overlap one another and whereby the intervening region between said discrete zones is exposed to a level of radiation significantly less than the radiant energy irradiating said discrete zones.