TWI233195B - Method of distributing conducting adhesive to lead frame - Google Patents

Abstract

The present invention disclosed a method of distributing adhesive on a lead frame and a structure of halftone used for distributing conducting adhesive to the lead frame. In order to overcome the bulge of the package leg on the vacuum tray and the lead frame under the slot of the vacuum tray, the resent invention form a plurality of slots on the halftone by etching to accept the bulge of the package leg, and drilling or etching a plurality of hole for the conducting adhesive going down to the lead frame during halftone printing. This method uses halftone printing to form multiple of conducting adhesive on the lead frame in one printing, thus increasing uniformity and quality, also decreasing process time and need not use more precise equipments, then decreasing production cost and increasing production efficiency.

Description

1233195, one-two -------------- five, description of the invention (1) 1 · Technical field to which the invention belongs The present invention relates to an improvement of a power transistor packaging method. It is related to the method of applying conductive adhesive to the power transistor when die chip bonding is performed. A screen having grooves is used to receive the pins, and a conductive adhesive is applied to a plurality of lead frames by printing on the lead frame of the wafer at a time for wafer bonding. 2 · Previous technology Power components are widely used in control circuits, power circuits, peripheral circuits and other fields. Most of their manufacturing methods have matured and become traditional industries. , Its importance is still irreplaceable. Therefore, how to reduce costs and increase competition ’is the goal pursued by the industry. Figure 1 is a perspective view of a gate fluid J-type package of the prior art. The lead frame 106 of the lower pin 114 is coated with a conductive paste 11 (), such as a silver paste, for bonding the crystal 7. The chip 102 is placed on the conductive adhesive 1 (1) of the lead frame 丨 06 and bonded to the lead frame 丨 06 by hot pressing. The lead frame 106 is surface mounted to the circuit board through the lower pin. Due to the large current when energized, the conductive knee needs to have low resistance. Generally, silver glue is used as an adhesive, which not only has low resistance but also has a high thermal conductivity. Large, suitable for conducting large current and heat dissipation. However, it can be replaced by other materials. To reduce costs. After the chip is adhered, the upper pin 104 is fixed, and then sealed with plastic 108, and then the pins 2 and 11 4 are bent.

1233195, V. Description of the invention (2) J ~ type pins, or L-type, I-type, etc. required for packaging, as required. Figure 2 is a schematic diagram of the prior art bonding a chip to a lead frame. Firstly, as shown in Fig. 2 (a), apply silver or other conductive glue 11 0 on the lead frame 106. Generally, the lead frame 1 06 needs to be bent down to a vertical distance, and the pin 11 4 has a thickness b, which causes the surface to be uneven, and can not be coated by printing. Two needs to be coated one by one with a robotic arm, which requires a lot of machinery and equipment. The labor and time in one mile increase the manufacturing cost; and the coating is uneven. Bad negative. After the conductive adhesive 11 is coated, the wafer 102 is bonded to the lead frame by hot pressing, as shown in the second figure (b). Therefore, the coating method of the conductive paste of the prior art causes a bottleneck in manufacturing and the quality is not good. And as man-hours increase, costs also increase. Therefore, the present invention is directed to the shortcomings of the prior art, and proposes a method. ^ Apply conductive adhesive to a plurality of lead frames at once on a neatly arranged lead frame. ^ However, the method of gluing green stalks is to use a screen with grooves to make the lead frame as high as pin I — when the wood is not on the same plane, screen printing can be used to increase the production capacity. A second object of the present invention is to provide a method for applying lead frame glue to a company, using

Page 8 V. Description of the invention (3) V. Description of the invention (3) Manual and expensive machinery and equipment on a neatly arranged lead frame. A method for gluing a lead frame, using the glue to make the distribution even, to improve a piece of screen with grooves and-, force + plus U, small holes, and screen printing to apply electric glue such as Mulena π to save Yet another aspect of the present invention is to provide a

Screen quality with grooves for screen printing quality. Point A, the first purpose of the present invention, and other objectives, and to improve the lack of the previous technology, the viewpoint of providing a conductive adhesive on the lead frame # '2-έΓ Λ Ϊ thin metal plate It includes at least: a plurality of bows of the lead frame recessed on the surface of the vacuum chuck; a plurality of 20% steel scrapers are pushed into the surface of the lead frame through a small hole to form a uniformly distributed conductive adhesive, which is used for wafer adhesion. use. A second aspect of the present invention teaches that applying glue to a lead frame includes at least the following steps: (a) arranging the wafer in a groove having a chuck holding a guide frame so that the pins remain on the surface of the vacuum chuck; (b) = ^ The screen with grooves for the leads of the lead frame is placed on top of the vacuum chuck and fastened, aligning the small holes with the central part of the lead frame, that is, the part to be glued, and the pins in the grooves of the screen. (C) Apply a conductive adhesive on the screen; (press the conductive adhesive with a steel scraper to make the conductive adhesive enter each small hole to form a conductive adhesive column, the tip of which contacts the conductive frame and attaches to the lead frame. (^) Remove the screen, so that the conductive glue remains on each lead frame to form a uniformly distributed conductor 1233195

V. Description of the invention (4) The above and other objects and advantages of the present invention can be more fully understood by referring to the following description of the reference factory and the preferred embodiment. 4. Implementation Mode The content of the present invention can be disclosed through the following embodiments in conjunction with the description of its related drawings. Referring to FIG. 3, FIG. 3 is a schematic diagram of a solid lead frame 106 placed on a vacuum chuck 302 according to one of the present invention. FIG. 3 (technical): = view; FIG. 3 (b) is along the 3rd Figure (a) is a cross-sectional view taken along line A-a. As shown in (a), a plurality of lead frames 106 are placed on the vacuum chuck ^ with the grooves 304, and the lead frames 106 are bent downward and are at a vertical distance d from the pins 114 in the grooves 304. The pin Π4 is on the surface of the vacuum chuck 302, and the complex position is higher than the lead frame 106. Generally, the depth of the groove 30 is determined as the thickness of the lead frame 06, and then the surface of the lead frame 106 is exactly flush with the surface of the vacuum chuck 3 02. If the width of the lead frame is large downward, the groove The depth of 304 is also b, shi compared to the thickness of the wire frame. As shown in the second figure *, the groove 30 / wood is… to accommodate the lead frame therein; if the lead frame 10 6 and the pin force 1 η β are equal to the vertical distance d, the depth of the groove is b + d. For example, wire = plus = thickness 0.2 draws 1 so that the depth of the groove 304 is also 0.2 dirty; but if the guide = sound is the vertical distance 4 from the lead 114 is 0.2 mm, then the groove 304 plus = von 0.2 surface + 0.2 surface = 0.4 surface. The lead frame is moved by a robotic arm to the vacuum suction cup of the straight-line two process to vacuum suck the lead frame to the real suction cup 302 for the glue coating process. The surface of the vacuum chuck 302, except for the pin 114, has no other

Page 10 V. Description of the invention (5) The protruding object is glued on the empty suction cup 3 02. Screen printing, but because of the pin 丨 i 4 the general screen printing can not be used to distinguish convex conductive from the reference with reference to Figure 4 (a) and (b) 'Figure 4 (Example of the screen version The structural plan, Figure 4 is a cross-sectional view taken along the line of solid line of two = month. The suitable BB of stainless steel screen plate 40 will not be deformed to a degree, generally about 0.35 to 0.5. = 0. 8 mm area to maximize the use of screen printing machine (not shown in Figure 1 is appropriate to increase efficiency. On the network territory with 2: 4 ΐ m unetched convex 4 ° 4 can reach the vacuum suction cup 3 〇2: groove: the surface of the wire plus ΐ106. Therefore, if the thickness of the lead frame is b, the vertical distance between ί 14 is d; then the ice degree of groove 408 is b + d, and the groove of the welding disk The depth of 304 is the same. Probably, = the conductive plastic falls, so it is preferably b + d -... where Ad is about: 1_ to 0 · 3_, for example, b = (K2mm, deduction 〇1_, Δ (ΐ = 〇 · ΐιηιη, then b + d-△ d = 0.2mm + 0.2mm-〇.imm = (K3mm, then drill a small spot on the unetched convex portion 404 directly opposite the lead frame 10 on the known connection plate 3202 Hole 406, its position is about 0.35mm to 4mm, depending on the crystal Its size is to be able to press a wafer during, the amount of conductive adhesive contact the wafer is completely adhesion degree, as of FIG. 4 (&). And (b), 1,233,195

V. Description of the invention (6) Brushing machine (if you have a picture, use a specially designed screen version, and then use the improved custom screen printing. According to this post: Another: The effect of the present invention is shown. Figure 5 shows The picture of the element. Clips = The practice of using a screen plate to apply glue to the lead frame by using a screen plate * Bug: Batch t > Test 5 (a), the screen plate 40 with the groove 408 to the true ^ Apply glue II, align the small hole 406 with the central part of the lead frame 106, that is, hemp position, and position the pin 11 4 in the groove 408 of the screen 402, and push on the guide plate * Apply a conductive adhesive tape 4. Then open it inside the steel scraper 502. Push left to right in the figure i to make the conductive adhesive enter the small holes 406 and glue columns 506 (refer to Figure 5 (b)), where The U wire frame m of the conductive rubber pillar is in contact with the lead frame and is attached to the lead frame = Re: The screen 402 is removed, and the conductive glue is left on the conductive glue U of the lead frame U cloth, and the coating process of the conductive glue is completed. This is not too much i. Female Jun, sealant and pin bending process, although the present invention is disclosed as an example above, but as long as the present invention, anyone who is familiar with this ... The accompanying Patent application Yasushi ore n: 々, the scope of the present invention this sense j < A defined Patent girth out whichever asked.

1233195 Schematic illustration 5. Schematic illustration: Figure 1 is a perspective view of the thyristor J-type package of the prior art. FIG. 2 is a schematic diagram of the prior art bonding a chip to a lead frame. FIG. 3 is a schematic view of a lead frame 106 placed on a vacuum chuck 3 202 according to an embodiment of the present invention, and FIG. 3 (a) is a top view; FIG. 3 (b) is a view along FIG. 3 (a ) Of the AA section.

Fig. 4 (a) is a plan view of the structure of a screen according to an embodiment of the present invention, and Fig. 4 (b) is a sectional view taken along line B-B of Fig. 4 (a).

Symbol description: 102 chip 106 lead frame 108 plastic 110 conductive adhesive 112 pin 114 pin 302 vacuum chuck 304 groove 402 stainless steel screen 404 projection 406 small hole 408 groove 502 steel to knife 504 conductive glue 5 06 conductive glue column

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Claims (1)

1233195 1. A screen structure for applying conductive adhesive to a lead frame, made of a thin metal plate, including at least: M a plurality of grooves to accommodate the lead pins protruding from the surface of the vacuum chuck; wood A plurality of small holes allow the conductive adhesive to enter the surface of the lead frame through a small hole under the push of a steel scraper to form a uniformly distributed conductive adhesive for wafers. 2) If the screen structure of item 1 of the patent application scope, the metal plate is a stainless steel sheet. 3. The screen structure according to item 2 of the patent application, in which the thickness of the stainless steel sheet is between 30 mm and 0.5 mm. 4 · As for the screen structure in item 1 of the patent application scope, the depth of the groove is the thickness b of the lead frame. 5 · If the screen structure of item 1 of the scope of patent application, the depth of the groove is b + d-△ (!, where b is the thickness of the lead frame, d is the vertical distance between the lead and the lead frame, which is one The distance is less than the thickness of the conductive frame. 6 · If the screen structure of the first patent application scope, the depth of the groove is about 0.2mm to 0.3mm. Page 14 1233195 VI. Scope of patent application 7. For example, the stencil structure of item 1 of the scope of patent application, wherein the hole diameter is about 0.3 5mm to 4mm. 8. — A method of applying glue to the lead frame, including at least the following steps: (a) arranging the wafer in a groove having a vacuum chuck for holding the lead frame, leaving the pins on the surface of the vacuum chuck; (b) having The screen of the groove that contains the lead of the lead frame is placed on the vacuum chuck to align the small hole with the central part of the lead frame, that is, the part to be glued, and the pin is in the groove of the screen; (c) Applying a conductive adhesive on the screen; (d) Pushing the conductive adhesive with a steel scraper, so that the conductive adhesive enters each small hole to form a conductive adhesive column, the tip of which is in contact with the conductive frame and adheres to the lead frame. (E) Remove the screen, so that the conductive glue remains on each lead frame to form a uniformly distributed conductive glue. Page 15