Startseite » Allgemein »

Polishing a raw process diamond

Odd-form assembly is still a reservoir for further automation
Polishing a raw process diamond

There are profound reasons to automate odd-form placement in high-volume board assembly. Today’s most advanced high-speed lines do indeed use the technology as a matter of necessity. Historically, the industry’s first attempts for the odd-form automation were slow, costly and inflexible. Changing products on such a line was labor-intensive, difficult to set-up and almost impossible to optimize.

Peter Chan, director, PMJ, England

After years spent basking in the sun of booming wireless-phone sales, growing demand for all kinds of electronic gadgetry and increasing manufacturing productivity, OEMs and contract manufacturers (CEMs) are finding their industry to be a suddenly cloudy place. Demand for many products has plummeted as the market reaches saturation. With consumers and corporations less eager to spend money on latest electronics appliances, the resulting price wars have cut into profits.
It’s not all doom and gloom: such an industry shakeout was certain to happen. A quick look at the major contract manufacturers shows that in spite of economic worries and industry shifts, business remains strong and sometimes profitable. The demand for smaller, faster and cheaper appliances continues – although which products will push next-generation demands can only be guessed at: Bluetooth solutions, PDAs, wireless internet appliances (WAPs), or perhaps a revolutionary technology that has yet to be conceived, maybe UMTS-based.
No matter the product, three things are certain: size and time-to-market will continue to shrink; any productivity gains that were achieved through frontend automation (from placement machines, printers and ovens) have reached their apex; and narrow profit margins will mandate higher levels of productivity and first-pass yields. And there’s a fourth requirement: for those whose products and livelihoods depend upon high-volume, low cost manufacturing, nothing short of total automation – front to back – will suffice if product quality, cost and manufacturing speed are the measures of success. And make no mistake, these three factors are what determine ultimate profitability. What then are the options for OEMs and CEMs? It may sound contradictory, but along with improved supply-chain management, the single key to greater productivity remains automation – but not where the industry has traditionally looked. Manufacturers have done a first-rate job squeezing productivity out of advanced frontend assembly processes. In many ways, the dream of the ”lights out” factory is approaching.
But the industry’s traditional way of doing things coupled with less than optimal first-generation products have created a blind spot of sorts: segments of backend processing that doggedly cling to manual methods. As remnants of an older, slower, less pressure-filled era, end-of-line (EOL) backend tasks – from odd-form placement to final assembly, selective soldering and test handling – remain a major bottleneck to high-speed assembly; not only slowing throughput but lowering quality, and raising overall manufacturing costs.
Of all so-called EOL processes, the most critical is odd-form assembly. Manual odd-form assembly is particularly labor intensive, slow and becoming next to impossible as components are shrinking beyond the ability to handle them. It is nonsensical to grind high-speed production lines to a halt while odd-form components are manually placed and clinched. Worse, manual assembly wastes time – in an age when time is arguably the one commodity manufacturers have the least of.
The changing face of odd-form placement
In the last decade, automated odd-form assembly technology has evolved to amazing levels of speed and accuracy. Robotics has added flexibility, and software advances have made so greatly improved programming that it delivers accuracy and flexibility equivalent to any automated machinery on high-speed lines. Today’s odd-form placement machines are light-years ahead of single-task, robotic-based systems, using advanced vision capabilities and enhanced grippers to easily insert a wider variety of odd-form components and do so accurately. For those manufacturers whose volume and product mix cannot tolerate manual operation, the addition of automated odd-form assembly makes a substantial difference in bottom line profitability.
What exactly constitutes odd-form? In its broadest definition, odd-form components can be any devices that cannot be easily handled by surface-mount placement machines. Obvious examples include connectors, headers, transformers, coils, DIPs, SIMM and DIM sockets, as well as axial and radial passive components.
The problem with odd-form components
It’s ironic that as the number of odd-form parts is decreasing on many of today’s assemblies, the importance of implementing automated insertion continues to increase. Given the cost of labor and the demand for faster time to market, manual placement of the remaining odd-form components represents an increasingly significant proportion of the manufacturing cost. Moreover, when the costs of labor, of training, of additional floor space are factored into the equation, manual odd-form placement for sophisticated assemblies no longer makes sense.
What makes automated odd-form assembly so challenging is the wide range of parts that may need to be inserted, and the varying shapes that could be encountered. For accurate and automated assembly, a general purpose, flexible machine is needed – one that can quickly adapt to a changing product mix. Because of varying tolerances and inevitable component defects, an automated odd-form assembly cell must be capable of inspecting parts and monitoring the process to verify correct operation. As the use of odd-form assembly equipment has increased and technology has improved, various techniques and off-the-shelf tools have been developed to solve once tremendous problems.
Feeders: handling diverse packages
There is a wide variety of packaging forms including: radial and axial tape, single and multi-lane tube, trays (various forms and sizes), continuous strip and loose batches. Machine vendors have developed a range of feeders to handle these different packaging forms. In addition, they have tried to make feeders highly flexible, so that they can be quickly exchanged, and can be easily adjusted to accommodate different tube length and width, tray size, etc. However, odd-form feeders are relatively expensive compared to SMD feeders, especially tray or bowl feeders that are often used for loose components. And there are limited packaging standards for tubes or trays. To overcome this problem, a standard interlocking tape specifically for odd-shaped parts has been developed. Because components can be located on the leads, the result is accurate and simple feed of components. However, there are extra costs associated with using this special packaging.
Another development that is simplifying feeding is the move to packaging certain odd-form components, especially connectors, in deep pocket tape. With this technique, the placement system needs to locate the component after pickup, since the parts are not accurately positioned in the feeder.
Grippers are flexible
Odd-form cells need to handle components with widely differing sizes and shapes. In order to do this with any degree of accuracy, gripping needs to be highly flexible. Various techniques have been used to provide this flexibility: multi-head gripper, pneumatic/vacuum-actuated gripper with head change, servo gripper with and without finger changer. Multi-head grippers can provide efficient cycle times since the head does not need to move from feeder to PCB for each pick&place operation. However, the flexibility of this system is limited. Changing components can require major mechanical modifications of the head.
To achieve flexibility, one alternative is to use a single pickup head, but to use an automatic head change system. In addition, while this approach provides flexibility – in that any shape or size of component can be handled – capacity can be severely compromised since a head change is required for almost each different size and shape of part. Using a servo gripper that can be programmed to handle different component sizes provides greater flexibility. However, limitations can arise with differently shaped parts, since the fingers used are not automatically interchangeable. Systems with servo gripper and automatic finger change provide the greatest flexibility, since any size or shape of devices can be handled automatically.
After feeding and inserting the part, the final stage in the assembly process is to ensure that it is retained in the PCB. Some parts, such as connectors, can use retention devices. For other devices, lead clinching is required. There are two basic techniques for doing this: dedicated clinching/shuttle plate, and programmable clinching units.
Sensing systems
Being able to feed, pick&place and clinch components is the only element of odd-form assembly. One of the main payback benefits for automating this is the potential improvement in product quality; but this benefit will only be achieved if the system can ensure that the assembly process has been carried out correctly. If, however, the automated process is carried out blindly, then end-of-line defects can increase compared to manual assembly. Tolerances in the assembly process which require sensing include the following: board size, feeding of components, body-to-lead, lead-to-lead and lead integrity (bent leads). Many parts cannot be correctly inserted without some form of sensing to accommodate for tolerance build up. A small percentage of components will not fit into the PCB, and the system needs to sense and reject these parts to ensure product quality.
There are several techniques for accommodating these tolerances, including floating head grippers, vision inspection, sensing during the insertion process, and the patented LeadScan of PMJ. Vision inspection is the most widely used sensing technique. It can be employed, with varying degrees of success, to compensate for the tolerances mentioned. The method of operation is similar to standard vision techniques used on SMD placers. There are, however, limitations of using standard vision that are specific to odd-form parts. First, inspection on-the-fly is severely compromised because of the wide range of shape and sizes of components. Second, inspecting the position of leads can be a daunting prospect, even for sophisticated vision systems. Wide variation of part shapes and sizes, lead forms, and body colors make vision inspection hard to set up and challenging to apply.
The LeadScan technique was developed to compensate for all the tolerances associated with thru-hole parts. The system consists of a laser and optical sensor positioned between the feeder and PCB, and a set of hard and software that monitors the Y-axis encoder (being the direction from feeder to PCB). And because this technique is generally applicable and carried out on-the-fly, it can be applied to almost all odd-form thru-hole parts. This is especially important in pin-in-paste applications where only one chance at successful insertion is permitted. This ability to carry out 100% inspection greatly improves the overall acceptance of odd-form machines, making their performance much more like that of SMD placement gear.
An outlook
The increasing complexity of electronic appliances coupled with reduced profit margins and shortened product life cycles mandate that manufacturers use very advanced technologies for each step of the assembly process. When speed, accuracy and cost are essential, manual assembly is no longer viable. The latest generation ofautomated odd-from insertion cells provides accurate and consistent handling ofa wide range of parts and offers high fle-xibility – enabling manufacturers to respond quickly when customer demands change and without long lead times, extended changeovers and complex software programming.
Automating odd-form assembly helps to reduce labor and rework costs – which are a major portion of electronics manufacturing expenses. Reducing these costs means that companies can offer higher quality and lower prices, and speed overall time to market. The best automated equipment can achieve throughputs close to that of standard pick&place machines. The result is a streamlined, cost effective process that increases yield, improves product quality and ultimately lowers costs.
 
EPP 167
Zusammenfassung
Automatisierung in der Elektronikfertigung ist speziell in westeuropäischen Ländern und deren Kostensituation (damit die Produkte global wettbewerbsfähig sind) eine bekannte Grundbedingung. Doch bisher hat man am Beginn der Produktionskette automatisiert. Im Bereich von EOL (End-of-Line), also beim Testhandling, Exotenbestückung, Verpacken usw., schlummern noch erhebliche Reserven. Schnelle Erfolge verspricht hier die rationalisierte Exotenbstückung.
Résumé
L’automatisation dans la fabrication électronique est une condition indispensable connue, notamment dans les pays d’Europe occidentale compte tenu de la situation en matière de coûts (afin d’assurer la compétitivité globale des produits). Mais l’automatisation a porté jusqu’à présent sur le début de la chaîne de production. Au niveau EOL (End-of-Line), donc au niveau des tests, du placement de composants exotiques, de l’emballage, etc., les possibilités sont encore nombreuses. La rationalisation du placement de composants exotiques permet d’espérer des succès rapides.
Sommario
La necessità di automatizzazione della produzione di componenti elettronici é una prerogativa ben nota soprattutto nei paesi dell’Europa occidentale mirata alla riduzione dei costi (al fine da mantenere concorrenziali i prodotti a livello mondiale). Sino ad oggi, però, l’automatizzazione ha avuto luogo solo all’inizio della catena produttiva. Nel settore EOL (End-of-Line), dunque nel test-handling, nella produzione di particolari „esotici“, nell’imballaggio etc. sono nascoste ancora molte riserve. La razionalizzazione nel montaggio di componenti esotici promette i maggiori successi.
Unsere Webinar-Empfehlung
INLINE – Der Podcast für Elektronikfertigung

Doris Jetter, Redaktion EPP und Sophie Siegmund Redaktion EPP Europe sprechen einmal monatlich mit namhaften Persönlichkeiten der Elektronikfertigung über aktuelle und spannende Themen, die die Branche umtreiben.

Hören Sie hier die aktuelle Episode:

Aktuelle Ausgabe
Titelbild EPP Elektronik Produktion und Prüftechnik 1
Ausgabe
1.2024
LESEN
ABO
Newsletter

Jetzt unseren Newsletter abonnieren

Webinare & Webcasts

Technisches Wissen aus erster Hand

Whitepaper

Hier finden Sie aktuelle Whitepaper

Videos

Hier finden Sie alle aktuellen Videos


Industrie.de Infoservice
Vielen Dank für Ihre Bestellung!
Sie erhalten in Kürze eine Bestätigung per E-Mail.
Von Ihnen ausgesucht:
Weitere Informationen gewünscht?
Einfach neue Dokumente auswählen
und zuletzt Adresse eingeben.
Wie funktioniert der Industrie.de Infoservice?
Zur Hilfeseite »
Ihre Adresse:














Die Konradin Verlag Robert Kohlhammer GmbH erhebt, verarbeitet und nutzt die Daten, die der Nutzer bei der Registrierung zum Industrie.de Infoservice freiwillig zur Verfügung stellt, zum Zwecke der Erfüllung dieses Nutzungsverhältnisses. Der Nutzer erhält damit Zugang zu den Dokumenten des Industrie.de Infoservice.
AGB
datenschutz-online@konradin.de