General Rules for Bonding and Packaging

Transcription

1 General Rules for Bonding and Packaging at the Else Kooi Laboratory

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3 3 CONTENT Rules for assembly at EKL 4 Introduction to assembly 5 Rules for Saw Lane 7 Rules for Chip Size 8 Rules for Bondpads 9 Rules for Bondwire 10 Wirebonding techniques 11 Examples of Order form Dicing, Die Bonding and Packaging 13

4 4 Else Kooi Laboratory Rules for assembly at EKL The design rules described here want to make clear to the designers of IC s, devices, and components what is allowed at EKL with respect to the assembly. Most of these rules are already available in the design manual for the bipolar process DIMES03, which could also be used for general information and explanations (e.g. what is meant by IC, IN). If you need to deviate from these rules,you first have to contact Koos van Hartingsveldt He can tell you if your requests are allowed and can be processed with success.

5 5 Introduction to assembly The typical procedure after finishing the IC-processing is as follows: 1. Electrical testing 2. Dicing 3. Die attach 4. Wire bonding 5. Encapsulation 6. Final testing [The (electrical) testing will not be discussed] Wafer dicing This is the process by which dies are separated from a wafer of semiconductor. The dicing process can be accomplished by scribing and breaking, by mechanical sawing (normally with a machine called a dicing saw) or by laser cutting (not at EKL). During dicing, wafers are typically mounted on dicing tape (foil). The adhesive tape on which the wafer is mounted ensures that the individual dies remain firmly in place during dicing. Once a wafer has been diced, the pieces left on the dicing tape are referred to as die, dice or dies. Dicing foil and frame Dicing blades Dicing a wafer Diced wafer (several dies have been moved)

6 6 Else Kooi Laboratory Die attachment This is the step during which a die is mounted and fixed to the package or support structure. Pick-and-place tool for die attach Manual wire bonder Wire bonding Wire bonding There are basically two forms of wire bonds, Wedge bonds and Ball bonds. Recent industry survey shows that about 90% of all electronic packages and assemblies are produced using ball bonds and about 10% are produced with wedge bonds. Encapsulation In the encapsulation stage, the die is encapsulated with ceramic, plastic, or epoxy to prevent physical damage or corrosion. As in other packaging stages, the customer has to take into account encapsulation requirement such as hermetic sealing, moisture contamination, physical package options, sensitivity of the dies to stress from packaging materials, height requirement of the capped devices, multi-die capability, etc. Many types of packages

7 7 Rules for saw lane The saw lane is a 160 µm wide track that is necessary for sawing the wafer into dies. This is the total width. For each die the outer 80 µm is reserved for the saw NOTE: When dicing the machine ALWAYS makes a cut over the whole wafer; the saw blade cannot be stopped somewhere half way! The saw-lane construction: rule no. meaning [µm] X X-step size chip 10,000* Y Y-step size chip 10,000* a width saw-lane 160 b half-width saw-lane, designed by the designer * Dimensions may deviate 80

8 8 Else Kooi Laboratory Rules for chip size The size of the (main) chip, called the die, is standard 10,000 x 10,000 or 15,000 x 15,000 or 20,000 x 20,000 [µm 2 ] when processed on the waferstepper, although other sizes are also possible. In case of doubt, please contact your project leader in advance. If there are several small designs, the die can be divided into smaller parts. In this way you get a multi-project chip. Example of a layout of a multi-project chip: Rule no. meaning value in µm a width of the saw-lane 160 b width of the extra saw-lane 160 X size of the die 10,000 Y size of the die 10,000 Xn X-size of the design - Yn Y-size of the design -

9 9 Rules for bondpads Rule no. meaning value in µm a bondpad size 100 or 80 b centre pad to centre pad 180 c centre saw lane to pad 110 d transition, pad to path 20 e transition, pad to path 20 f pad metal toother metal except path 40 f

10 10 Else Kooi Laboratory Rules for bondwire Rule no. meaning a max. length 3 mm b wire to bond pad centre 120 µm c wire to package pad 200 µm d NO CROSS OVERS e min. wire angle to die edge 40º

11 11 Wirebonding techniques EKL offers two different wire bonding technologies: The basic steps for both types of wire bonding include forming the first bond (normally on the chip), forming the wire loop and forming the second bond (normally on the substrate). Ball bonding One key difference is that in ball bonding, a free air ball is formed at the beginning of each bond cycle and the first bond is achieved by bonding the ball to the pad. There are fewer restrictions on the direction for looping the wire from the first to the second bond in ball bonding. This makes ball bonder looping extremely flexible. Wedge bonding In wedge bonding, the wire is bonded directly to the device using force and ultrasonic energy. Bondwires can be Al or Au: Al wire bonding is attractive for some applications because room temperature bonding is possible and because there are no Au-Al intermetallic compounds, which occasionally cause reliability concerns. Au bonding is performed at elevated temperatures (normally C); this process is called thermosonic bonding because it employs heat and ultrasonic energy. Wire bonding process: (a) wedge bonding and (b) ball bonding

12 12 Else Kooi Laboratory EKL bondwires: Type of wire Wire thickness [µm] Ball bonding (± 150º) Aluminium 17 x Aluminium 32 x Gold 32 x Wedge bonding (room temperature) Ball bond Wedge bond Capillary for ball bonding Wedge for Al wire wedge bonding