Laser bonding scheme

An arrangement for providing improved efficiency in laser bonding is disclosed. In particular, at least one piece part in the arrangement is formed to include means for concentrating a beam of radiation at a predetermined attachment location (or several locations). The concentrating means may be in the form of an aperture, such as a conical or parabolic opening, which will concentrate the radiation to the area of interest. Alternatively, if the piece part is transparent to the wavelength of the radiation, the concentrating means may be in the form of a lens or grating formed on the surface of the piece part.

BACKGROUND OF THE INVENTION 
1. Technical Field 
The present invention relates to laser bonding and, more particularly, to a 
scheme for improving the efficiency of a laser bonding process. 
2. Description of the Prior Art 
Laser bonding has been successfully utilized in a number of applications to 
provide joining of piece parts. See, for example, U.S. Pat. No. 4,990,741 
entitled "Method of Laser Welding" and issued to R. J. Moores et al. on 
Feb. 5, 1991. As disclosed, first and second metallic components may be 
joined along a weld path, with the beam focused by a low turbulent flow of 
an inert shielding gas along a portion of the path. In most applications, 
the material used to form the piece part (plastic or metal, for example) 
is opaque to the optical radiation and the radiation must therefore 
impinge the material from the side of the point of contact. This 
limitation is considered to further complicate and increase the cost of 
laser welding systems. 
Thus, a need remains in the art for increasing the utility of laser sources 
in various bonding applications. 
SUMMARY OF THE INVENTION 
The need remaining in the prior art is addressed by the present invention 
which relates to laser bonding and, more particularly, to a scheme for 
improving the efficiency of laser bonding. 
In accordance with one embodiment of the present invention, at least one 
piece part is formed to include predefined features which concentrate the 
optical radiation toward predetermined locations which are to be joined. 
An advantage of the concentrating features is that the piece part itself 
may be formed of a material which is opaque to the wavelength of optical 
radiation. 
In one embodiment of the invention, a first piece part may be formed to 
include at least one aperture of a geometry (e.g., conical) which will 
provide concentration of the laser radiation at a predetermined location. 
In an alternative embodiment, a first piece part may be formed of a 
transparent material and include concentrating means, for example, an 
integral lens, to concentrate the radiation at the predetermined location. 
For an embodiment where both piece parts are transparent, an absorbing 
material (such as an epoxy) may be used at the interface between piece 
parts to absorb the radiation and become heated. 
Alternatively, a first piece part may be formed to including diffraction 
means for concentrating the radiation near the location where the piece 
parts are to be joined. 
An exemplary embodiment of the present invention may utilize conical 
apertures, with the apex of the cone located at or near the joining 
location. 
In an alternative embodiment, the apertures may comprise a parabolic shape, 
thus providing heating at a number of focii, creating a plurality of 
joints. 
Other and further embodiments and advantages of the present invention will 
become apparent during the course of the following discussion and by 
reference to the accompanying drawings.

DETAILED DESCRIPTION 
FIG. 1 illustrates an exemplary arrangement 10 for providing concentrated 
laser joining (which may be referred to hereinafter as "laser welding", 
but may also include laser tacking or bonding) in accordance with the 
present invention. Arrangement 10 includes a first piece part 12 and a 
second piece part 14, where both piece parts may comprise a material which 
is opaque to optical radiation, for example, plastic or stainless steel. 
It is to be assumed that the piece parts are to be attached at locations A 
and B as shown in FIG. 1. In accordance with the present invention, piece 
part 14 is formed to include a pair of concentrating apertures 16 and 18. 
Concentrated optical radiation impinges upon piece part 14, as shown, 
entering apertures 16 and 18. In particular, the radiation is in the form 
of a plurality of collimated beams which enter apertures 16 and 18 (the 
geometry, number and location of the apertures being arbitrary for the 
purposes of the present invention and will be discussed in greater detail 
below; attachment will occur at any predetermined number of sites). 
The radiation entering apertures 16 and 18 is illustrated as being 
continuously concentrated toward terminations 20 and 22 of apertures 16 
and 18, respectively. In general, as long as the sidewalls of apertures 16 
and 18 taper inward, a sufficient amount of radiation impinging the 
sidewalls will be re-directed back into the apertures and continue its 
propagation toward terminations 20,22. It is to be noted that terminations 
20, 22 do not necessarily have to be coincident with end surface 24 of 
piece part 14. As along as terminations 20,22 are substantially near 
surface 24, sufficient heating will occur such that laser welding at 
locations A and B is achieved. 
An alternative arrangement 30 which may utilize laser welding in accordance 
with the teachings of the present invention is illustrated in FIG. 2. A 
first member 32 is joined to a second member 34 at location 36, as shown. 
Here, aperture 38 is formed at the sidewall of second member 34, where 
sidewall 39 of aperture 38 is angled so as to direct radiation upward. 
First member 32 may also have an angled sidewall (not shown). 
Various other aperture geometries, including those illustrated in FIGS. 3 
and 4, are possible. FIG. 3 illustrates a piece part 40 including a 
concentrating aperture 42 for providing laser welding in accordance with 
the teachings of the present invention. As shown, aperture 42 includes 
inwardly curving sidewalls 44,46 which serve to direct the laser radiation 
toward weld site 48. In this particular embodiment, aperture 42 terminates 
within piece part 40 at a location separated from weld site 48. However, 
as mentioned above, the concentrating of the laser radiation at the 
terminations has been found to provide sufficient heating (as indicated by 
the dotted lines) to form a weld at site 48. Thus, the process used to 
actually form apertures need not be precisely controlled, and the 
formation of apertures at least near the depth of the weld site will 
usually be sufficient. FIG. 4 illustrates another piece part including an 
aperture terminating at a position displaced from the weld site. In 
particular, piece part 50 includes a concentrating aperture 52, in this 
case with concave curving sidewalls 54,56. Weld site 58 is also 
illustrated in FIG. 4 as being separated from the location of the 
termination of aperture 52. It is to be understood that various other 
apertures may be successfully used in the practice of the present 
invention to provide concentrated laser welding. In general, virtually any 
geometry capable of directing energy toward desired locations may be used 
in accordance with the teachings of the present invention. 
FIG. 5 illustrates an alternative embodiment 60 of the present invention 
where the re-direction of the optical radiation is provided by refraction. 
In particular, a first member 62 is to be attached to a second member 64 
at location 66. In this case, second member 64 must be sufficiently 
transparent to the wavelength of the impinging radiation. As shown, second 
member 64 comprises a lensed surface 68 which functions to concentrate the 
collimated beam of radiation toward weld site 66. If second member 64 
comprises a plastic material, lens 68 may be formed during a molding 
operation. Alternatively, if second member 64 comprises a silicon 
substrate, lens 68 may be etched. In any case, the shape of surface 68 is 
not critical, as long as a sufficient amount of radiation is concentrated 
relatively near to the desired weld site 66. 
Another embodiment of the present invention which also utilizes a 
transparent concentrating member is illustrated in FIG. 6. As shown, 
arrangement 70 includes a first member 72 and a second member 74, where 
second member 74 is sufficiently transparent to the wavelength of the 
impinging radiation. Second member 74 includes a concentrating region 76, 
shaped as illustrated in FIG. 6, to direct the radiation toward weld site 
78. In particular, concentrating region 76 is formed so as to provide for 
reflection of the radiation, since an air gap is illustrated as 
surrounding region 76. 
FIG. 7 illustrates yet another embodiment of the present invention which 
may be utilized with a transparent concentrating member. In particular, 
arrangement 80 includes a first member 82 and a second member 84, where 
second member 84 is sufficiently transparent to the wavelength of the 
impinging radiation. Second member 84 includes a diffraction grating 86 
formed on the surface thereof. In one embodiment, the diffraction grating 
may comprise a zone plate. As is well-known in the art, a diffraction 
grating may be formed so as to result in concentrating the impinging 
radiation at a desired location, in this case at predetermined weld site 
88. 
As mentioned above, a concentrating aperture may be formed to include a 
parabolic-type opening such that a pair of laser welds are simultaneously 
formed within a single aperture. FIG. 8 illustrates, in a 
three-dimensional view, an exemplary arrangement 90 wherein a first piece 
part 92 is to be joined to a second piece part 94. Second piece part 94 
includes an aperture 96 with a pair of parabolic-shaped walls in opening 
98 and 100, as shown. Therefore, an incoming collimated beam will be 
directed to the location of parabolic aperture 96, the focal lines being 
along 102 and 104 in this embodiment. Therefore, a pair of linear laser 
welds will be formed within a single aperture in accordance with this 
particular embodiment of the present invention. 
FIG. 9 illustrates an alternative embodiment 120 for providing linear laser 
welds in accordance with the teachings of the present invention. In this 
arrangement, a first piece part 122 is to be laser welded to a second 
piece part 124, where piece part 124 is sufficiently transparent to the 
wavelength of the optical radiation used to perform the welding operation. 
Sidewalls 126 of piece part 124 are formed, as shown, to comprise 
parabolic shapes so as to focus the incoming collimated radiation along 
lines 130 and 132. 
As mentioned above, various aperture geometries are suitable for providing 
laser bonding in accordance with the present invention, as long as the 
aperture provides sufficient concentration of the radiation near the bond 
location. FIG. 10 illustrates an exemplary piece part 140 including a 
plurality of various apertures which may be utilized as discussed above. 
In contrast the embodiments discussed above, the apertures of piece part 
140 are shown as terminating in geometries other than a point or straight 
line. In particular, a set of four apertures 142 are illustrated as 
terminating in arcs, which may provide for bonding around the periphery of 
a circular piece part, for example. As with the arrangements discussed 
above, the apertures are formed to include sidewalls which provide for 
concentration of the laser radiation along the apex. Aperture 144 is 
illustrated as terminating in a cross-shaped apex, another suitable form. 
In general, any desired geometry may be used to provide the desired 
results. 
It is to be understood that there exist may other arrangements suitable for 
providing concentrated laser attachment in accordance with the present 
invention. The various embodiments as discussed above are exemplary only, 
and for the purposes of explanation not limitation. Further, as mentioned 
above, the concentrating features of the present invention may be utilized 
with various types of laser-based bonding procedures, including, but not 
limited to, welding, soldering or tacking