ADHESIVE DISPENSING

Case Study 2—Process Development and Validation of an Adhesive Dispensing Station... 

There are three factors related to the set-up of the adhesive dispensing station that may impact the final bond strength. They are as follows ... 

Doyle, Daryl J. (1990). Viscosity and Its Importance to Adhesive Dispensing. Society of Manufacturing Engineers Technical Paper AD90-710, Adhesive Technology for Automotive Engineering Applications, November 1-2, 1990, Dearborn, Michigan. 

Table 4.13 Advantages and limitations of adhesive dispensing methods... 

The number of dots that can be dispensed per unit of time also depends on viscosity. The use of low-viscosity adhesives increases the number of dots that can be dispensed. However, there is a tradeoff between the speed at which the adhesive can be dispensed and the speed of device placement. Most automated component-placement equipment operate faster than adhesive-dispensing equipment. A comparison of the effect of viscosity on dispensing and placement times is shown in Table 4.19 for an 86-lead plastic-encapsulated leadless chip carrier (PLCC). ... 

Figure 4.11 Example of a needle map for Loctite 3609 adhesive dispensed from a Camalot dispenser. (Reproduced with permission from Speedline Technologies.)...

Table 4.22 Commercially available adhesive dispensing systems... 

Lewis A, Bahiarz A. Conductive adhesive dispensing considerations, Proc. NEPCON West. Anaheim, CA Feh. 1999. 

Figure 4 D5max method. Steps (1) Worker loads magnets to automatic feeder/adhesive dispenser also brings motor cans to second worker station. (2) Second worker applies activator to can housing with a semiautomatic dispenser. (3) Second worker then places can over magnets that have been previously placed into fixtures robotically. (4) Turntable cycles, engaging fixture pressure mechanism. (5) Bonded parts are automatically off-loaded to continue in production.

When using isotropically conductive adhesives, placement of components is performed by the same equipment as used for nonadhesive attachment techniques. Die bonders are similar to those used for eutectic bonding except for the type of adhesive dispenser. Surface-mounted placement machines developed for solder paste assembly can also be... 

Table 4.13. Advantages and Limitations of Adhesive Dispensing Methods... 

A needle-valve controls the amount of adhesive dispensed. Advantages of this method include lower cost and simplicity of operation compared with the auger and the linear piston types. Some disadvantages are ... 

Table 4.22. Commercially Available Adhesive Dispensing Systems... 

Lewis, A., and Babiarz, A., Conductive Adhesive Dispensing Considerations, Proc. NEPCON West, Anzhdim, CA (Feb. 1999)... 

Most adhesives dispense well and by using a small tip stringing may be eliminated. Syringe application is also the best method for filling and potting applications, with polyurethanes or silicones. 

A type III board will first be inverted, adhesive dispensed, SMDs placed on the bottom-side of the board, the adhesive cured, the board rerighted, through-hole components placed, and the entire assembly wave-soldered. It is imperative to note that only passive components and smaU active SMDs can be successfuUy bottom-side wave-soldered without considerable experience on the part of the design team and the board assembly facility. It must also be noted that successful wave soldering of SMDs requires a dual-wave machine with one turbulent wave and one laminar wave. 

---