Patent GB-1147924-A (GB)
Title: Improvements in machines for assembling articles on substrates
IPC: H01L21/00
Filed: 1966-05-23
Abstract: 1,147,924. Conveyers; gripping articles; orientating articles. INTERNATIONAL BUSINESS MACHINES CORP. 23 May, 1966 [27 May, 1965 (4)], No. 22830/66. Headings B8A, B8H and B8S. [Also in Divisions B3, F2 and H1] A machine for placing a plurality of articles at an equal plurality of predetermined positions on a substrate comprises means (5) for placing the substrate on a conveyer (1), means (17) for placing one article at each predetermined position on the substrate, means (22) for testing the substrate for the presence or absence of an article at each position and means (23) for separating substrates having an article missing from those having articles in all positions. In the specific embodiment, the article is a semi-conductor chip C (Fig. 1) containing a diode or a transistor and having pre-soldered copper balls B on one side thereof, whilst the substrate is an insulating substrate S having pre-soldered conductive lands L thereon the end portion P of each land being enlarged. Four chips are placed on a preformed substrate bearing screened resistors R, to form a computer element. The substrates having pins (38c) on their lower surfaces are fed on to a perforated stainless steel conveyer 1 at 5 with the pins through the perforations (Fig. 68A, not shown) and the end portions P embossed at 6. A flux of rosin in alcohol is deposited 9 on the end portions and this flux flattened by an air blast at 21. A semiconductor chip C is picked up by a vacuum needle on a placement head 17 from a vibratory bowl feeder 19. The orientation of the chip balls is sensed at 20 and if required the chip is re-orientated at 21 before being placed on the substrate S with the chip balls B properly aligned with the embossed end portions P. As many placement heads 17 as there are positions for chips on the substrate are provided. Each substrate is sensed at 22 to determine whether chips are missing and any substrates not having the required number of chips are removed at 23 and replaced by good substrates. The chips are subsequently bonded to the substrate by baking in an oven thereby melting the solder on balls B and lands L. At each station along the conveyer where work is performed on the substrate, a clamp (Figs. 67 and 68, not shown) is provided to hold the substrate accurately (see Specification 1,128,385 in Divisions E1-E2). The conveyer 1, shoot feeder 5, dimpler 6, flux dispenser 9, chip placement heads 17, chip sensor 22 and rework head 23 are all driven (Fig. 4, not shown) by a variable speed motor (48), each item having its own solenoid-controlled onerevolution clutch (29-33). The clamps and the conveyer are both driven by the motor through a one-revolution clutch (50), the clamps being periodically actuated by a cam mechanism (51) acting through a rod (110c) having individual members (12c) thereon to actuate each clamp whilst the conveyer is moved by an indexing mechanism (71). The electric circuits (Figs. 85-105, not shown) used to control the sequence of operations of the various items and related operations of the various items are described together with logic flow diagrams of the operations. Flow diagrams for the sequence of operations on each substrate and chip (Fig. 5, not shown), the logic flow for the initial operations of loading, dimpling, dispensing and flattening (Fig. 79, not shown), the logic flow for the chip placement head (Figs. 80 and 81, not shown), the logic flow for the chip presence sensor and rework head (Figs. 82 and 83, not shown) and the logic flow of the overall system control (Fig. 84, not shown) are given. The control circuits provide amongst other things for the following contingencies (a) if there is no substrate to be loaded the tape loader is stopped; (b) if the substrate is skew on the conveyer or four successive substrates are misloaded the machine is stopped; (c) if there is no substrate present the chip placement head is inhibited from indexing; (d) if the vacuum needle is clogged the machine is stopped; (e) if no substrate is present the chip presence sensor is inhibited; (f) is the chip sensing contacts are jammed the machine is stopped and (g) if a defective substrate is not removed from the conveyer or there is no carrier to receive it the machine is stopped. A shoot (Fig. 19) feeds substrates from 64a on to slide 68a and where the substrates are pushed by 60a on to the conveyer against stop 72a being held in position by arms 70a whilst a rod (76a, Fig. 21, not shown) pushes the legs of the substrate into the holes provided on the conveyer. The rod (76a) and pusher 60a are actuated by cams 10a and 14a on shaft 12a. A dimpler 6 and a flux dispenser 9 (Fig. 22) reciprocate vertically by the action of cam 16d on shaft 25d, the dispenser being actuated by rotation of shaft 32d. The dimpler has four punch heads (40d, Fig. 23, not shown) each head having three punches (42d, Fig. 24, not shown) and a resilient backing (48d, Fig. 25, not shown). In use a head forms a dimple and three holes in a group of three end portions P (Figs. 7-9, not shown). The dispenser has a nozzle 78d through which flux passes from the reservoir 76d when an air pressure pulse is sent through 84d thus allowing blobs of flux to touch the substrate if present at the predetermined positions (Fig. 10, not shown). If no substrate is present re-application of a vacuum through 84d will draw the flux back into the reservoir. The flux flattener 15 (Fig. 28A) is supplied with air via 12f and is provided with a curved cap 24f which shields the four nozzles 28f from the direct flow of air in the plenum chamber 16f. The nozzles are direct against raised flux portions 30f and spread it out evenly (Fig. 13, not shown). The chip placement head 17 (Fig. 30) has eight pick-up arms 30h all driven intermittently by shaft 26 each arm having a vacuum pick-up needle 90h (Fig. 32) at its end. Each needle picks up a chip containing a transistor or diode having copper balls as contact elements from the feed bowl 19 at station 32b, indexes one station to 20 where the orientation of the chip is sensed, and then indexes another station to 21 passing through chip blow-off station 27 where a blast of air (Fig. 31, not shown) will remove the chip if the sensing station 20 indicates that the chip is malformed or held on end. At station 21 the chip is re-orientated if required according to the information from station 20. On indexing to the next station a lever 132h actuates switch VD1 if a chip is missing from the needle, this switch will actuate relays that delay the departure of the substrate from placement station 34h. On indexing to station 34h the needle will place the correctly orientated chip if present on a prefluxed printed alumina substrate. Preceding and following each index the arms 30h are raised and lowered respectively. This movement and the indexing is transmitted by a Geneva mechanism (Fig. 45, also Figs. 42, 43 and 44, not shown) wherein drive from shaft 26 is fed to shaft 1i which has a cam 3i acting on rod 13i which transmits vertical reciprocation to shaft 2i and thus to the arms (30h) whilst a hemisphere 4i moves in grooves 5i thus transmitting intermittent rotation to shaft 2i. Springs 37i and 77i are provided to maintain engagement of the parts. Vacuum is supplied to the needle through a manifold 52h and a distributer 50h, the distributer 50h moving round with the arms 30h whilst the manifold 52h reciprocates axially through a cam and lever movement driven off shaft 26 (Figs. 37 and 38, not shown). The distributer and manifold have channels and openings therein to connect the line 120h to vacuum or air according to their relative dispositions (Figs. 34, 34A, 35, 36, 41, and 41a to 41d not shown). The needle 40h is constructed to draw in air through its open end and also through a side line 126h. If a chip is not present at the needle's end then only a small amount of air is drawn in through 126h and the diaphragm 154h moves upwards raising level 132h which will actuate switch VD1 (Figs. 39 and 40, not shown, illustrate the needle's construction). The upward movement of the diaphragm 154h also causes level 170h to raise the needle 40h and thus prevents it being dipped into the flux on the surface of the substrate. The chip sensing device 20 determines in which one of four possible orientations (236e- 239e, Fig. 86, not shown) the chip is held. One of four switches (36e-39e, Fig. 59, not shown) is closed by the movement of one of four sensing blade elements (45-75, Figs. 60 and 61, not shown) each carried by a pivot arm (10s, Fig. 57, not shown). Guide jaws 20s (Fig. 58) are loaded by springs 22s to correct minor misalignment of the chip. The jaws 20s are opened after a sensing operation by the action of compressed air acting on a piston 27s connected to the jaws by a rod 29s and members 26s and 24s. Should the chip become dislodged from the probe 18, air acting on the cylinder 27s acts through a duct 40s and an opening 44s in a tube 46s to blow the chip from the sensing station. The blast is delayed from acting on a normally-retained chip by the time taken for the rising piston-rod 29s to engage the tube 46s (and thus connect the opening 44s with the duct 40s). The chip orientator 21 (Fig. 65) has a T-shaped head 2t which is rotated by a stepping motor 5t having an armature (56e) and windings (52e-55e, Fig. 95, not shown) through a Geneva mechanism 14t, 16t. According to the orientation of the chip sensed at 20, the head 2t is orientated by motor 5t to one of four quadrantal positions to receive the chip from the vacuum needle 18. The head 2t re-orientates the chip to the desired orientation and the chip is restored to the needle 18. The particular one of the four quadrantal of the head 2t for receiving and restoring the chip is controlled by sensor 20 according to a set programme determined by the arrangement of the connections of terminals (A, C, E, G, to B, D, E, F, Figs. 86, and 91-99, not