FR2686475A1 - LASER FORMED ELECTRICAL COMPONENT AND MANUFACTURING METHOD. - Google Patents

Abstract

An electrical component includes a set of overlapping ferrite layers (34, 44, 53, 64), with a spiral conductive coil (70) printed on each layer. The conductive coil is formed by first printing a sheet of conductive material on the ferrite layer, and then exposing the sheet of conductive material to a laser energy pulse focused by a mask in a predetermined pattern, which cuts the coil in the sheet of conductive material.

Description

LASER-FORMED ELECTRICAL COMPONENT

AND MANUFACTURING METHOD

  The present invention relates to an electrical component formed by laser and a method of manufacturing this component. The present invention relates more precisely to a multilayer electrical component, comprising superimposed layers of insulating material alternating with printed patterns of spiral coils, formed at go

  of an electrically conductive material.

  Many electrical components using coils have been manufactured in the form of chips, with

  various alternating layers of ferrite and conductors.

  However, several drawbacks result from the known methods for manufacturing these devices.

  most coils formed in this way do not

  do not have a complete coil, having more than one turn in each superimposed layer Instead, in known devices, a part of each coil is placed on different layers, and these parts are connected

  so as to form a complete coil having several turns.

  Certain known devices do in fact

  a whole coil, having more than one turn, on each layer of ferrite; however, the possibilities of miniaturization of such devices are limited, because of the constraints of the printing techniques which are used. The known methods for forming the coils.

  conductive on each layer usually do

  the printing of the conductive material on the ferrite layer Most of the techniques for printing these layers do not allow the lines to have a width much less than 0.20-0.25 mm, and do not allow the spaces between - s lines are much less than 0.20-0.25 mm This minimum dimension of lines and spaces places a limit on the level of miniaturization

  which can be reached with coils of this type.

  Lasers have been used in the field of resistors, to adjust these and to form them. However, in the laser processes which are used at present, one must follow with a

  laser beam the pattern of the particular conductor desired.

  This is a time consuming task that does not allow

  to form this conductor quickly or instantaneously

tanned.

  A main object of the present invention is therefore to provide an electrical component formed by laser of an improved type, and a method for manufacturing this component. A further object of the present invention is to provide an electrical component formed by laser of an improved type, which can be produced in a smaller size than the devices of the prior art, while simultaneously obtaining an identical inductance value. or higher than what is currently available. A further object of the present invention is to provide a method and means for manufacturing electrical components which make it possible to reduce, compared with prior devices, the width of the lines of inductors and the width of the spaces.

between the lines of these coils.

  An additional object of the present invention

  is to provide a device and method the use of which

  be economical, operate efficiently and

that are reliable.

  The present invention uses an excimer type laser system which is capable of directing a pulse of laser energy through a mask structure. The mask can be a metal plate from which the desired pattern has been cut. The mask, acting at the like a stencil, ensures that the image of the desired pattern is focused through a lens on a substrate carrying a layer of conductive material The image burns and removes part of the conductive layer, leaving the desired pattern, such as a coil or other path

conductor of electricity.

  Inductance coils can be made so that they have alternating layers of

  ferrite and conductive coils Conductive coils

  trices are formed by printing a layer of material

  conductive layer, such as silver, on the upper surface of a ferrite layer The laser is then used to project a negative image onto the conductive layer, so as to remove the conductive material which corresponds to the negative image This leaves the conductive coil formed on the top surface of the layer

of ferrite.

  Pairs of additional layers can be similarly formed, and can be stacked on top of each other, to produce a laminated chip having a complete conductive coil having more than one complete turn in each layer Holes are formed in the layers of ferrite to connect in series with each other the various conductive coils in the

  multilayer chip, in order to obtain the desired inductance.

  We currently have Excimer laser systems that are capable of projecting an image over an area of 5 to 10 square millimeters. This allows multiple chips to be formed simultaneously. It is therefore possible to make a single layer for a group of chips with

  a single pulse of laser energy The individual layers

  are made separately, and they are then stacked on top of each other and subjected to a heat treatment, so as to transform them into a single group of superimposed layers. Diamond saws are then used to cut the stacked layers into

individual chips.

  The invention will be better understood on reading

  the following description of an embodiment,

  given by way of nonlimiting example The continuation of the

  description refers to the accompanying drawings in which

  Figure 1 is a perspective view of the

  laser system which is used with the present invention

tion.

  Figure 2 is a schematic representation showing the manner in which the laser system

  directs the laser beam on the treated object.

  Figure 2A is a plan view of a mask

  used in the present invention.

  Figure 3 is a view showing the multiple layers of stacked chips which are formed in accordance with

the present invention.

  Figures 4 A-4 C are top plan views of a single chip showing the first step in forming a first layer of ferrite and a coil

conductive of electricity.

  Figures 5 A-5 C, 6 A-6 C and 7 A-7 C are views similar to Figures 4 A-4 C, and show the steps for forming pairs of additional layers

for the multilayer chip.

  Figure 8 shows the final layer which is

placed on the multilayer chip.

  FIG. 9 is a perspective view of a single multilayer chip, with parts of the layer

upper cut.

  Figure 1 shows an Exci- laser system

  sea 10 which can be used for the present invention.

  Systems of this type are currently available for use in the manufacture and marking of electrical components. However, these systems have not been used for the process contemplated by

  present invention An example of such a system is made

  qué by Lambda Physik, Inc, 289 Great Road, Acton,

  Massachusetts 01720 under the brand "Lambda Mark".

  The system produces a pulse of laser light which is represented by the line 11 in FIG. 2 The laser light It is directed firstly through a mask structure 12, which comprises a mask or a stencil in which the pattern is formed desired After passing through the mask, the laser beam has the shape corresponding to the desired image, and is deflected downwards by a mirror structure 14, containing a mirror 16, so as to pass through a lens 18 The lens 18 can reduce the dimensions of the image several times, so

  to intensify the image and produce a more focused image

  The image is then directed towards a work surface 20 on which an object to be treated is placed. With regard to the present invention, a mask 13 is used which contains a negative coil pattern 15 The pattern 15 consists of an opening at through the mask 13 which corresponds, in negative, to the shape of the coil which it is desired to form. Consequently, the resulting coil will finally have the shape of the solid part 17 which is shown in FIG. 2 A.

  Referring to Figure 3, we see a stack-

  ment 22 of sheets 23, 24, 25, 26, 27 The upper sheet

  lower 23 is constituted by a material of the ferrite type,

  commonly used in the manufacture of industrial chips

  monolithic tances The remaining sheets 24-27 are also ferrite sheets, but various conductive coils 28 are printed on these sheets.

  coils 28 which are on each sheet are identical

  ticks to each other, but the coils differ from sheet to sheet, as will be explained below

more completely.

  The dotted lines 30 represent break lines which are finally formed with a

  diamond saw, to cut each of the empi-

  lées in individual chips containing a set of coils 28 Figure 3 is not drawn to scale, to illustrate the various components of the invention However, at actual scale, the layers 23-27 are thin as

  paper, and the lines of the bobbins 28 measure approximately

  0.25 mm wide, the spaces between the lines inside the coils also measuring approximately

0.25 mm.

  Figures 4-8 illustrate the structure of each individual chip, but in actual practice, the layers for a set of chips are printed on each of the ferrite layers 23-27, as shown in Figure 3 A first layer of ferrite 34 constitutes the lower layer of the chip This ferrite layer 34 represents one of the chips found in the layer to

  multiple chips 27 which is represented in FIG. 3.

  FIG. 4B shows a first layer of continuous conductor 36 which is printed on the upper surface of the ferrite layer 34 The conductor 36 is preferably silver, commonly used in printed components of this type The layer 36 comprises a connection pad 38 which extends to the outer edge of the ferrite layer 34 FIG. 4 C shows the conductive coil 40 finished The conductive coil 40 is formed by exposing the conductive layer 36 to a pulse of laser light which has everything first passed through the mask 13 and which was then reflected downwards by the mirror 16, through the lens 18 Consequently, the pattern of

  the negative image 15 is focused on the conductive layer

  trice 36, burns and removes parts of the layer 36, so as to leave the conductive coil 40, as shown in Figure 4 C The coil 40 includes a pad

central 42.

  It should be noted that the conductive coil 40 comprises

  takes at least two full turns of the coil on a surface In addition, the width of the conductor 40 can be reduced, up to 0.25 mm, the spaces between the lines of the conductive coils measuring approximately 0.25 mm This is significantly smaller than what is normally obtained with prior devices, and allows to obtain a maximum inductance value in a

minimum space.

  An example of a preferred method for manufacturing the conductive coil 40 which is shown in FIG. 4 will be described below. A laser system Excimer 10, such as the system manufactured by Lambda Physik, is used to produce the conductive coil. Inc, 289 Great Road, Acton, Massachusetts 01720 under the brand "Lambda Mark" This particular device has several parameters of

  setting that can be set to produce the result

  desired state The factors involved in these para-

  meters are as follows: 1 Various surface materials for the layer

  conductive 36 produces different results.

  2 The size of the chip is variable. 3 The size of the stencils in the mask

is variable.

  4 The reduction ratio in the mask holder structure is an adjustment of the device, which is variable. The focusing lens that is used

  by the machine and its micrometric position, are varied

  wheat. 6 The laser power setting, which corresponds to the DC voltage setting in the system, is

another variable.

  An example of a preferred system setting is as follows:

  1 Surface material: silver type ink-

  uncooked palladium, manufactured by Du Pont / under the designation

tion of product 7711.

  2 Pattern size: 1.27mm to 1.63mm square

next to.

  3 Pattern size in the mask: square of

12.7 mm side.

  4 Reduction ratio: between 10: 1 and 7.8: 1.

  Focusing lens and micrometric position: SPLF 20/10 lens, placed at a position of

56 centimeters.

  6 Laser power adjustment: 8.8 to 7.5

volts (direct voltage).

  The system is then turned on to produce a pulse of laser light which is projected onto the layer 36 and which forms a coil 40 by burning and removal of material, as shown in FIG. 4 C. The duration of exposure is estimated at a value between 0.5 millisecond and 2 milliseconds We cannot however determine the exact duration precisely,

  the fact that the system which is used employs a discharge

  of the capacitor to produce the light, and that the specific duration of exposure to light cannot be

precisely determined.

  Other systems can be used to produce the same result, and other settings can also be used to produce different types of electrical components. FIGS. 5 A, 5 B and 5 C illustrate the second superimposed layer which is formed by the use of a layer of ferrite 44 The individual chip comprises a second layer of ferrite 44 having in its center an opening 46, aligned at the above the central stud 42 of the first conducting coil 40 A second conducting layer 48 is printed on the ferrite layer 44, the desired image being transmitted through a mask similar to that which is represented in FIG. 2 A. However, the particular shape of the mask is defined so as to produce the second conductive coil pattern 50, represented in FIG. 5 C The coil pattern 50 comprises a second central stud 51, in vertical alignment with the opening 46, and comprises a second stud 52 The conductive material of the central stud 51 projects downward through the opening 46, so as to establish electrical contact with the central stud 42 of the coil 40 The coils 40 and 50 s have

  thus electrically connected in series with each other.

  FIGS. 6 A-6 C show a third superimposed layer which consists of a third layer of ferrite 53 in which a connection hole 54 is formed; a third conductive layer 56; and a third reel

  conductive 58, formed by a focused laser image

  read, in a similar way to that according to which the coils 40 and 50 are formed The opening 54 makes it possible to connect the third end pad 62 of the coil 58 to the end pad 52 of the coil 50, which places mutually in series the coils 40, 50 and 58 The coil

58 includes a central stud 60.

  FIGS. 7 A-7 C show a fourth superimposed layer comprising a fourth layer of ferrite 64 in which an opening 66 is formed; a printed conductive layer 68 on which an end pad 74 is formed; and a fourth conductive coil 70 on which a central stud 72 is formed. The coil 70 is

  formed by a focused laser image in a similar way

  the method used to form the coils 40, 50 and 58 The central stud 72 projects through the opening 66 so as to establish electrical contact with the central stud 60 of the third conducting coil 58 This places the series mutually in series. set of four coils

40, 50, 58 and 70.

  A final ferrite layer 76 is placed on the multilayer block, so as to produce the configuration

  which is shown in Figure 9.

  The chip 78 which is represented in FIG. 9 is one of those of the set of chips formed by cutting along the dotted lines 30 of the stack of sheets 23-27 of FIG. 3 The ferrite layers 34 , 44, 53, 64 and 76 are formed from the respective sheets 27, 26, 25, 24 and 23 of Figure 3 The sheets 23-27 are formed individually and are then placed together in a stacked manner, as shown in the figure 3 More precisely, in accordance with the method of the present invention, each layer 23-27 is printed individually, by printing the conductive layers 36, 48, 56 and 68 on the respective layers. The printed conductors are then allowed to dry. The printed conductors are then exposed. to images from the laser system 10 Each sheet 23-27 is exposed individually, but each sheet includes a set of identical sub-elements After the sheets 23-27 have been exposed tormer image to the coils 40, 50, 58 and 70, 23-27 sheets are stacked as shown in Figure 3 and are pressed together while they are pressed, they are subjected to a heat treatment for it

  that they join together in one block.

  After the heat treatment, the superimposed sheets 23-27 are cut using a diamond saw,

  along the lines 30, so as to form chips

  individual lines such as the chip 78. The present invention makes it possible to miniaturize the

  more chips than in prior art devices

  Since the chips are miniaturized, it is possible to place more than one complete turn of the coil on each layer, whereas with devices of the prior art, it was necessary to place less than one complete turn on each layer The coils of the present invention can be miniaturized to the point at which the conductors are about 0.25 mm wide, while

  the spacing inside the coil is also

  about 0.25 mm wide Can be incorporated

  as many stacked layers in the chip as necessary

  or the chip can be formed by a single coil and a layer. Because the dimensions of the laser image are reduced, the laser cutting can be many times finer than that which is carried out by screen printing, and the corresponding inductance values can be much higher than what is currently possible. So we can see that the device

  achieves at least all of its stated objectives.

Claims (4)

  1 electrical component (78) characterized in that it comprises: a support element (34) having a support surface; a conductive electrical element (40) mounted on the element support surface   (34) and having a predetermined shape; this elective element   conductive stick (40) being formed by printing a continuous layer (36) of conductive material on the support surface, and then using a single pulse of laser light focused in a negative image of the predetermined shape to burn and remove all parts of the continuous layer other than those corresponding to the predetermined shape.   2 electrical component according to claim   1, characterized in that the predetermined shape of the element   electrical is the shape of a spiral coil.   3 electrical component according to claim 2, characterized in that the support element is in ferrite (34).   4 electrical component according to claim 1, characterized in that the conductive electrical element is formed by passing a pulse of laser light   through a mask (15) in which an opening is formed   stencil shape in the shape of the negative pattern and through a lens 7 placed so as to project   on the conductive material a corresponding focused image in the negative pattern.   Electrical component according to claim 1, characterized in that the laser light pulse has   between 0.5 and 2.0 milliseconds.