Method for mounting component chips and apparatus therefor

A method and apparatus for mounting components on a substrate that insures that if the component, because of its shape can only be mounted if picked up in a specific area will not attempt mounting unless the component is picked up in that specific area. Various methods for setting and determining desirable pick up locations are disclosed.

BACKGROUND OF THE INVENTION 
This invention relates to a method and apparatus for mounting components 
and more particularly to an improved method and apparatus for this 
purpose. 
Various devices have been proposed for picking up small electronic 
components such as chips containing a circuit and mounting those 
components on a substrate such as a printed circuit board. Normally a 
vacuum type pick-up is employed for picking up the components to be 
mounted. Various devices have been proposed so as to recognize the 
component that is picked up and have its center aligned with the mounting 
nozzle and thus positioned appropriately on the substrate or circuit 
board. 
However, many of these types of components have a surface that may be 
irregular in shape and if an attempt is made to mount these components, a 
portion of the component may not be fully in contact with the circuit 
board. Such types of chips having abnormal shapes are MELF, ceramic 
capacitors, aluminum electrolytic capacitors, fixed inductors of the chip 
type and semi-fixed volume chips. These types of devices have curved 
corners or may be tall and unstable. Thus, with these types of components 
it may not always be desirable to pick up the component at its center for 
assembly on to the board because of the aforenoted difficulties. 
It is, therefore, a principal object of this invention to provide an 
improved method and apparatus for mounting components on a substrate. 
It is a further object of this invention to provide a method and apparatus 
for mounting irregular shaped components on a substrate or board. 
It is a further object of this invention to provide a method and apparatus 
which permits successful mounting of components on a circuit board even if 
those components have irregular shapes. 
SUMMARY OF THE INVENTION 
This invention is adapted to be embodied in a component mounting apparatus 
for mounting a component on a substrate. The apparatus comprises a 
component handling device adapted to pick up a component and mount the 
component on the substrate. Means are provided for detecting the position 
of the component when held by the component handling device. 
In accordance with an apparatus embodying the invention, means are provided 
for rejecting the mounting of the component on the substrate if the 
component is not held by the component handling device at a location where 
the component is likely to be successfully mounted on the substrate. 
In accordance with a method of practicing the invention, if the component 
is not determined to be held by the component handling device at a 
location where the component is likely to be successfully mounted on the 
substrate, the mounting process is disabled.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
Referring first to FIG. 1, an apparatus constructed and operated in 
accordance with a method for practicing the invention is illustrated. 
Certain of the components are shown schematically where their detailed 
construction forms no important part of the invention. Also, some of the 
components are shown schematically. The apparatus is designed to mount 
electronic components such as chips or the like, indicated generally at 21 
on a substrate, indicated generally at 22 which substrate may consist of a 
printed circuit board. 
The apparatus includes a conveyor 23 which delivers the components 21 to a 
pick-up station. It should be readily apparent, however, that the 
component conveyor 23 may in actual practice comprise a delivery reel on 
which the components 21 are carried as is well known in this art. Thus, 
the components are shown generally schematically since the actual 
construction of the various components used to practice the invention can 
be varied to suit particular applications as will be readily apparent to 
those skilled in the art. 
A pick-up nozzle 24, which may be of the vacuum type, is carried by a head 
25 that is mounted for movement in a preselected path and which is 
operated by a drive 26 for movement between a position in registry over 
the component conveyor 23 and a position over a circuit board conveyor 27 
on which the substrates or circuit boards 23 are presented. Between the 
component conveyor 23 and the substrate conveyor 27 there is positioned a 
recognition and determination section that includes an electronic camera 
28 and a light source 29 which are both connected with an image processor 
31 which includes certain sections, as will become apparent. There is 
further provided a position detector 32 which is juxtaposed to the 
electronic camera 28 and which sends a signal to a control 33 when the 
mounting head 25 passes it. 
The control 33 receives signals from an operator input 34 such as a key 
board or the like so as to program the control 33 so as to move the 
mounter head 25 and pick-up nozzle 24 in an appropriate position both over 
the conveyor 23 for the chips or components 21 and over the conveyor 27 so 
that the component can be mounted at the appropriate location on the 
substrate or circuit board 22. In addition, a CRT display 35 is positioned 
at the operator's station and the operator can see the component 21 
carried by the pick-up nozzle 24 before it is mounted or at any time 
during the operation, as may be desired. 
The image processor 31 includes a setting memory 36 on which information 
regarding the various chips and/or components to be mounted can be 
displayed such as the shape of the component and the acceptable pick-up 
area on the component. There is also provided a recognizing section 37 
that receives the input from the electronic camera 28 and the information 
from the memory 36 so as to indicate the actual position of the component 
on the pick-up nozzle 24 and also to determine if the component is being 
held at the acceptable pick-up area. In the event it is not, a signal is 
outputted to a section 38 which initiates the suspend mounting operation 
of the control 33 so as to prevent mounting of the improperly picked up 
component 21 from the pick-up nozzle 24. The rejected component may be 
returned back to the chip conveyor section 23 for another pick up try or 
maybe placed in a reject bin, as desired. The image processor 31 also 
outputs a picture of the view of the camera 28 to a CRT display 40. 
The apparatus further includes, in accordance with one embodiment of the 
invention, a recognition spot 39 which is placed on the mounter head 25 
for the purpose of determining the location of the mounter head 25 and 
pick-up nozzle 24 relative the electric camera 28. The recognition spot 39 
may be deleted in embodiments where the control 33 and specifically the 
driver 26 is programmed to position the mounting head 25 and chip mounter 
head 24 in the same position it is in registry with the electronic camera 
28 and such as in the embodiment of FIGS. 4 and 5. 
FIGS. 2 and 3 show the arrangement where the chip 21 is determined to be or 
not to be picked up at the acceptable pick-up area. When the position 
sensor 32 sensor senses that the mounting head 25 is in position above the 
electronic camera 28, the light source 29 is illuminated and the camera 28 
takes a picture of the above scene and this picture appears in FIG. 3 
wherein the viewing area of the camera is indicated by the area "A". The 
camera has memorized into it a fixed coordinate origin V.sub.o for 
reference purposes in its visual field "A". 
The camera will see the reference mark 39 at the point V.sub.m and from 
this can compute where the center of the pick-up nozzle 24 is. This is the 
point V.sub.n. Then the camera can recognize from the shape of the 
component and the information from the memory 36 to determine the center 
of the component V.sub.c. Once this information is determined, then the 
device computes whether the component has been picked up in an appropriate 
area since the pick-up area is readily determined from the location of the 
pick-up nozzle V.sub.n relative to the chip center V.sub.c, all of which 
are determined as aforenoted. 
The acceptable area for the chip or component 21 is determined as an area 
where, when picked up by the pick-up nozzle 24 the chip or component 21 
can be successfully mounted on the substrate 22. This determination will 
be based upon the shape of the component and specifically its lower 
surface which will come into contact with the circuit board or substrate 
22 and also its upper surface which is picked up by the nozzle 24. The 
manner in which this determination is made for various chips will be 
described later. 
FIGS. 4 and 5 show another embodiment of the invention wherein the head 23 
does not have the recognition spot 39. Rather, in this embodiment the 
control 33 and drive 26 is configured so as to always place the nozzle 
center V.sub.n centrally of the viewing area "A" of the electronic camera 
28. In this embodiment, the location of the center of the nozzle V.sub.n 
as shown in FIG. 5, will always be in the same place. Hence, when the 
image of the chip or component 21 is recorded on the electronic camera 28 
as shown in FIG. 5, then its center V.sub.c can be determined from the 
information in the memory 36 and by recognizing section 37 of the image 
processor 31. Again, this will then provide sufficient information so as 
to permit the device to determine if the chip or component 21 is 
positioned so that it can be successfully mounted on the circuit board or 
substrate 22. 
FIGS. 6 through 9 show various types of chips and the acceptable pick-up 
areas thereon so that the device can determine if the chips or components 
have been picked up at the acceptable pick-up area. In each figure the 
acceptable area is indicated by the broken line "B". In FIG. 6, the chip 
21 has its effective pick-up area "B" lying within a circle having a 
radius "R" from the chip center V.sub.c. Hence, as long as the pick-up 
nozzle V.sub.n is within the circle "B" it is determined that the chip can 
be successfully mounted. 
In FIG. 7, the effective pick-up area "B" lies within a radius "r" of the 
center pick-up nozzle V.sub.n and this is determined as being the 
effective area where mounting can be successfully completed. 
The effective area in FIG. 8 is described by a rectangle "B" having "x-y" 
coordinates relative to the chip center V.sub.m and as long as the pick-up 
nozzle V.sub.n is within this area, then mounting will be successful. 
In FIG. 9, the rectangular coordinates are described from the nozzle center 
V.sub.n with the effective area being indicated by the rectangle "B". 
FIG. 10 shows another embodiment and way in which it can determined if the 
chip 21 or component has been picked up in the acceptable pick-up area. 
The way this is done is that the camera measures the area of the chip 
within an imaginary rectangle "C" by determining the unshaded area of this 
rectangle which is indicated at "B". If the ratio of the area obscured is 
greater than a predetermined amount, it is known that the chip has been 
picked up in the acceptable area for mounting and mounting can be 
completed. 
Of course, the foregoing examples are only a few examples of ways in which 
the acceptable pick-up of the chip or component can be determined. 
One type of control routine is shown in FIG. 11 and will now be described 
by reference to that figure. When the program starts it moves to the Step 
S-a to effect picking up of the chip or component 21 from the chip or 
conveyor or pick-up station 23. The program then moves to the Step S-b to 
determine that the chip has actually been picked up by the pick-up nozzle 
24. This can be done by sensing a change in the vacuum pressure of the 
pick-up nozzle or by a position detector carried by the pick-up nozzle or 
various other manners. 
If, at the Step S-b it is determined that a chip has not been picked up 
successfully by the pick-up nozzle 24, the program moves to the Step S-c 
to add a count to a counter which will determine the number of times when 
pick up has been attempted. The program then moves to the Step S-g to 
determine if the number of attempts at picking up has exceeded a 
predetermined number of attempts. If it has not, the program returns to 
the Step S-a to again attempt a pick up. If, however, at the Step S-h the 
controller 33 determines that too many pick up attempts have been 
unsuccessfully made, the program will move to the Step S-i to sound an 
alarm or otherwise warn the operator and then will stop the program. 
If, however, at the Step S-b it has been determined that a chip has been 
successfully attracted by the pick-up nozzle 24, then the program 
continues to cause the mounting head 25 to move into proximity with the 
electronic camera 28 and, at that time, the program moves to the Step S-d 
so that the identity of the chip is determined by comparing the outline of 
the chip as seen by the camera 28 in the recognizing section 37 of the 
image processor 31 with those stored in the memory 36. If the chip is not 
appropriately identified, the program moves to the return mode at Step S-c 
to repeat a pick up of the chip because it is assumed that either a chip 
has not been properly picked up or what has been picked up is not an 
appropriate chip for mounting. Again, if too many attempts are made the 
program will sound the alarm at the Step S-i and stop the program. 
Assuming, however, at the Step S-d the chip has been recognized, the 
program moves to the Step S-e to determine if the particular chip or 
component being picked up has an effective pick up area. As noted above, 
not all components or chips are sensitive to the point at which they are 
picked up. If the chip does not have an effective pick up area (can be 
picked up effectively at any location on it) the program moves to the Step 
S-f to move the mounting head 25 into proximity with the substrate or 
circuit board 22 and mount the component 21. 
If at the Step S-e it has been determined that the component has an 
effective pick-up area, the program then moves to the Step S-g so as to 
determine if the component has been picked up in its effective area, by 
one of the recognition methods already described. If the component has, 
then it is mounted at the Step S-f. If, however, it has not been picked up 
in its effective area, then another pick up attempt is made at the Steps 
S-c, S-h and S-a so long as the number of attempts has not exceeded the 
predetermined maximum number of tries. 
It should be readily apparent from the foregoing description that the 
described embodiments of the invention are extremely effective in insuring 
that components to be mounted automatically are picked up in an area where 
they can be successfully mounted, even if those components have irregular 
shapes which dictate that they can be successfully mounted only if picked 
up in acceptable pick-up areas. Of course, the foregoing description is 
that of preferred embodiments of the invention and various changes and 
modifications may be made without departing from the spirit and scope, as 
defined by the appended claims.