Automation of your line is nearly complete. Chip shooters are running well, AOI has been dialed in, reflow profiles are finally settled. However there are still those few nagging parts that have to be put in by hand to complete each board. They seem to defiantly resist automation, and yet automation is the key to providing the process control needed for today's quality demands. How do you take automation all the way to the end of the line?
The first step is a open discussion between manufacturing engineering and the product design team and producing an earnest design-for-manufacturing study. Manufacturing engineers and designers have to work hand in hand to identify the outstanding parts and the reasons they cannot be automated, then find new ways to deal with those parts.
Today, component manufacturers are offering more and more odd parts with surface mount features. A review of current offerings may open some doors that weren't there a short time ago. Alternatively, some problem parts may be able to be eliminated entirely by creative circuit design.
Despite the push to surface mount technology there are still lingering odd-form and through-hole components required in many boards. The problem becomes how to automate these last straggling components. Placing parts before reflow is most desirable because it eliminates a second soldering process; namely wave solder or selective soldering. In a pin-through-paste process, parts must be placed by machine. Manual insertion into paste is unreliable. Automating these parts requires a standard Odd Form Insertion Machine, or some kind of semi-automatic automation that attempts to achieve the process goals. The number of components that need to be automated will determine the machine capacity. Typical odd form machines offer the capability lf handling 5 to 10 different part styles. Odd form systems need to offer flexibility and simple setup. The system needs to have the flexibility to handle a variety of components without extensive retooling.
In situations where the remaining odd form part count is low, the equipment needs to be relatively inexpensive in order to justify its purchase. In addition to labor costs, factors that should be taken into account for justification include yield improvement, rework costs, and consistent throughput.
The most common parts left behind for hand-assembly after automating the rest of the assembly process include connectors which need the mechanical integrity of a through-hole junction or snap-in feature, or electrolytic capacitors that are too large for auto-insertion or migration to surface mount insertion. Some components are not suitable for reflow ovens, and others simply are not packaged for automation.
Connectors become difficult to automate because of the need for a solid mechanical connection to the board. Through-hole solder connections have long provided this connection whereas surface mount generally does not. Automating connectors in a strict surface mount environment usually means fastening the component to the board with screws or rivets after reflow, which can be accomplished with a small machine dedicated to screw fastening or rivet driving.
Large electrolytic capacitors often fall into the "last to automate" category. They are too large for surface mount, and even too large for standard radial insertion machines. They can be put in by hand, but not in a pin-through-paste situation, and manual insertion has a high exposure to polarity errors. Standard feeders exist for large electrolytics, including feeders with polarity checking features. Odd form machines handle these parts well.
For parts that cannot tolerate the heat of a reflow oven, or for which the cost of the part in through-hole format is significantly less than the surface mount counterpart, the manufacturer can continue to use through-hole style parts but place them post-reflow and use selective soldering to make the connection. Odd form machines can be used to automate these components as well. Component packaging is another hurdle for automation of odd form components. Although component manufacturers offer many parts in packaging suitable for automation, there is a cost associated. In other cases, the volume of parts required does not provide the component supplier with the incentive to package for automation. The manufacturer becomes the driving force in the demand for automation packaging. If full automation of a product is important, then packaging for automation is required.
Aftermarket packaging alternatives are available, such as tape and reel services or extruded tube manufacturers. For some parts, however, bulk packaging may be the only possibility. Some of these parts are suitable for vibratory bowl feeding. Bowls make economic sense if the part will be present in the product for a long enough period to pay back. Other parts may be suitable for a flex feeding approach where parts are presented randomly on a belt and located with machine vision for automated pickup.
Many surface mount equipment manufacturers offer odd form capability within their machines, for parts that have vacuum pick up features. There are several companies that offer odd form insertion systems for through-hole components.
Two such odd form insertion systems are available from Chad Industries: the CHAD IQs for higher volumes and part mixes of 3 to 10 parts, and the CHAD IQp, designed to be a low cost system for handling those last few straggling odd components when you are trying to take automation to the very end of the line.
Contact: Chad Industries, 1565 S. Sinclair St., Anaheim, CA 92806 714-938-0080 fax: 714-938-0630 E-mail: firstname.lastname@example.org Web: http://www.chadindustries.net