Traditional feeder setup using tape-and-reel can drain time. There’s a quick and better way.

Tape-and-reel is the preferred method of feeding electronic components for automated SMT assembly because of ease of use and high repeatability. Everything from resistors to BGAs to odd-form components is packaged in tape-and-reel. But costs of feeder setup – some hidden – can drain profits through lost inventory and production time. Reel splicing kits can dramatically improve reel setup and changeover efficiencies to improve any PCB assembly operation’s bottom line.

SMT feeder tape is a two-piece system: The bottom tape is embossed with pockets to hold individual components, and the top tape seals the pockets to hold components in place (Figure 1). The bottom tape, known as carrier tape, has sprocket holes punched along its edge(s) for precise indexing of components to their pick positions. The top tape, or cover tape, is sealed over the pockets by either heat-activated adhesive (HAA) or pressure-sensitive adhesive (PSA).

To set up a reel of components on a pick-and-place feeder, the reel is loaded on a spindle, and the tape is threaded through a series of guides, tensioners and drive sprockets. The first 12" to 18" of cover tape are peeled back and wound onto a take-up spool. The components in the pockets under the peeled back cover tape cannot be machine-picked and are usually scrapped. High-value components may get manually placed or manually fed to the placement machine during the production run.

Loading a reel into a feeder and onto a machine takes an operator 1 to 4 min., depending on the reel configuration and placement system being used, and can de-tape between 15 and 150 components per reel, depending on their size.

Tape splicing kits eliminate production line downtime for replacing empty reels and component de-taping during reel setup. A splicing kit typically consists of a set of shims, a crimping tool and a variety of cover tapes (Figure 2). The shims interlock with the feeder tapes’ sprocket holes to join two ends of tape together, and the crimping tool secures them in place. Splicing shims and tools are universal; they work on all tape sizes from 8 to 56mm, and in all pick-and-place equipment platforms.

Cover tape sizes and styles are selected based on their application. Basic cover tape connectors are 2" lengths of PSA tape that join the cover tapes of the two reels being spliced together. They are installed after crimping the shim to the carrier tapes. Cover tape connectors may be used as singulated strips or may be combined into a one-piece unit with the shims for easy installation. Specialty one-piece units for certain smart feeders integrate an additional strip of cover tape to signal the start of a spliced reel to the machine.

Cover tape extenders (Figure 3) are longer pieces of tape that act as a leader for the take-up spool. They have adhesive only on the end that affixes to the reel’s cover tape, and are about 20" long. Extender tapes are available in one- or two-ply. Single layer extender tapes are most common; dual-layer tapes are used in situations where the original cover tape is difficult to peel. All cover tape connectors and extenders are compatible with both HAA and PSA reel cover tapes, and come in standard feeder tape widths of 8, 12, 16, 24, 32, 44 and 56mm.

Tape extenders. Cover tape extenders are extremely popular with high-mix PCB assemblers because they reduce component costs and ease kitting logistics. Frequently changing line setups can de-tape lots of components. To deal with this issue, PCB assemblers can 1) write off the inventory as setup scrap, bearing the full cost of the parts, 2) manually feed the components, stopping to load the machine for each placement and slowing overall production, or 3) hand place the components, if possible, increasing the probability of creating defects. There is a price to be paid for each option, and PCB assemblers are forced to choose. More
important than the cost, however, are the logistics of kitting the components, especially for EMS companies that perform low-volume consignment builds. Components are often kitted in exact multiples of the PCBs being built, without any allowance for setup or scrap. If the CEMs can’t hand feed or hand place the components, they must ask OEMs for extras.

Tape extenders can eliminate much of the cost and pain associated with frequent line changeovers. They can reduce scrap, maintain the productivity of automated assembly processes, and prevent logistical headaches. As lot sizes get smaller, the savings realized by using cover tape extenders get bigger.

Splicing in high-volume assembly. High-volume PCB assemblers that build larger lot sizes also save money with cover tape extenders, but achieve the greatest cost benefits by keeping production lines continuously up and running with reel splicing. High-volume manufacturing economics rely on high machine utilization rates; stopping machines to replace empty reels is an enormous drain on efficiency and profitability. While it only takes a few minutes for an operator to change a reel, those minutes add up to hours over the course of a shift, week or month. By splicing a fresh reel onto the end of a nearly empty reel before it runs out, the machines operate continuously with no stoppage.

High-volume manufacturers often employ portable splicing carts to travel around the factory floor (Figure 4). The carts are outfitted with all necessary splicing supplies, including scissors, shims, crimping tools, dispensers for the various cover tapes and storage areas for new and empty reels. They are small, rolling workbenches that boost the efficiency of the operators as they boost the efficiency of the assembly line.

Whether a PCB assembly operation is considered high mix/low volume or low mix/high volume, it can benefit from the use of tape splicing kits. Extender tapes eliminate the inventory scrap on feeder setups; reel splicing prevents machine downtime for parts replenishment. Shorter production runs realize greater benefits from tape extenders to minimize scrap rates, and longer production runs realize greater benefits from tape splicing to maximize asset utilization.

Rob Sierra is the owner and president of Sierra Electronics; rob@tapesplice.com. 

Thanks to external grants and internal execution, reshoring is becoming a big business for some smaller EMS companies.

At Firstronic, a Grand Rapids, MI-based electronics contract manufacturer, reshoring isn’t just a talking point; it has become the company’s major source of business growth. Over the past year, the company has won both onshore and offshore business. What is most significant is that the bulk of this production is being exported to other countries. Of the five programs ramping in 2013, four involve shipping product produced in Michigan to Mexico, China, Korea, or India. The sixth program involved moving work back from China. The total incremental export business that is currently ramping up will represent approximately $12 million in sales in 2013 and $30 million annually in sales longer term.

What is driving this phenomenon? The answer is twofold: a greater focus on total cost within companies outsourcing production and a strong focus on efficiency enhancements.

From an OEM standpoint, the driving focus is on cutting time in new product development and maintaining competitive advantage.

For example, Walbro originally selected Firstronic as a second source for printed circuit board assemblies. These PCBs are integrated into Walbro’s products and used by various lawn and garden power equipment manufacturers. The primary contractor was in Malaysia, but product development was in Michigan. Cost, lead-time and quality improvements led to the entire project being moved back to North America. Firstronic’s success on this initial project has led to additional business opportunities with Walbro, including assembly of an electronic fuel control module used in scooters. The largest end-markets for these new products are expected to be in emerging markets that have high-volume scooter sales, including China and India.

Economies of scale were a key benefit in expansion of an automotive control project with Dura. Models destined for China and India were combined with US production to utilize the same tooling and test platform within a single supplier.

Proximity to the development team was a selection factor on four products related to seat and shift controls from Kongsberg Automotive that ship to several locations in Mexico.

That was also a factor in AGM’s award of an LED printed circuit board assembly that will be shipped to China. Firstronic was able to support the development of a new product with local support throughout the design cycle and provide rapid responsiveness with flexibility.

In another example, the right mix of quality, cost and responsiveness led a German OEM with operations in Mexico to select Firstronic for a fuel pump controller and converter box that is shipped to Mexico.

However, it took more than responsiveness and proximity to development teams to achieve a competitive total cost equation. Firstronic’s strategy to reduce cost focused on cutting material costs and investing in automation that improved efficiency while minimizing administrative overhead.

Material cost is often 70% of total product cost. Firstronic leverages its supply base expertise as part of design for manufacturability/testability (DfM/DfT) process to develop recommendations that will lead to cost reductions. PCB fabricators may provide input on optimum layouts for boards, and test fixture suppliers may make recommendations on the best layout for test coverage. Suppliers also proactively provide updates on component lifecycle trends. This information is added to the overall recommendations the project team makes in its new product introduction process.

To minimize liability yet support variable demand, both raw materials and finished goods inventory kanbans are established. Suppliers agree to a bonded inventory based on each customer’s forecast and likely variations in demand. A finished goods kanban is also in place and is normally sized to cover one to two weeks of demand. Production builds to the forecast and pulls material on demand. In the event the demand changes radically, forecasts and bonds are revised.

The company also has automated many project management functions with an internally developed system. The Windows-based relational database system provides project team members with the ability to log on 24/7 to find out exactly what open action items need to be addressed. This “pull” system approach “force multiplies” the program management team, enabling fewer people to effectively manage more programs. However, it also has a “push” system element. The project templates that the team has created minimize the project setup activity and flag issues as they occur.

In short, the system is more diligent than a program manager alone would be because it immediately recognizes if an action or a missed deadline anywhere in the process is impacting the ability to meet the critical path deadlines established for the project. If that happens, it immediately emails the team members responsible for correcting the issue. The system also creates full documentation and a post-mortem history to facilitate process improvement.

The tool integrates fully with the company’s ERP system, Plex Online, a Service as a Software (SaaS) system that includes the ERP system, a manufacturing execution system (MES) module, EDI customer and supplier interfaces, and online quality data collection/reporting tools. The cloud-based tool enables customer and Firstronic personnel to access information remotely.

On the production floor, Lean manufacturing techniques are used to maximize flexibility, while ensuring quality. Core principles include:

• Select equipment that facilitates minimized setup and changeover time.
• Produce entire product families with a single setup.
• Schedule smaller batches and work toward minimal work-in-process (WIP).
• Focus on high yield to drive high throughput.
• Fixture to enable a variety of panels to be processed and scanned through the wave solder or reflow processes.

Firstronic has received state assistance in reducing overhead expenses. In recognition of its success in proving that “Made in USA,” and specifically, “Made in Michigan,” is a cost-competitive option, the company has been awarded a State Export Trade Now (STEP) grant via the Michigan Economic Development Corp.’s Pure Michigan Export Program. The grant helps offset marketing expenses. This is the second year the company has participated in the program. MEDC grants in 2012 helped offset the cost of trade missions to Germany and Romania, which resulted in project wins representing 50% of the 2013 export revenue. An additional grant-funded trade mission to Mexico also resulted in another $5 million of this year’s export revenue. The company has also become part of the West Michigan Medical Device Consortium (WMMDC), which provides a Michigan-based supply chain solution to medical customers.

Done strategically, outsourcing can be a highly cost-competitive option that preserves domestic jobs. Companies that evaluate the true cost benefits associated with speed of project launch, schedule flexibility, ease of communication and superior quality quickly recognize that nearshoring critical components closer to their core team saves money. In this case, the fully ramped business will create an additional 100 US jobs.

John Sammut is CEO of Firstronic; jsammut@firstronic.com.

Pick the right standard and know what it is that needs testing.

Long-term product reliability is a concern for any production manager responsible for the plastic-encapsulated microcircuits (PEMs) going on printed circuit boards used in military, aerospace or medical applications. Similar concern for reliability is exercised in manufacturing some commercial products, especially where competition is intense and a word-of-mouth reputation for field failures can be harmful.

It is widely understood that images of internal anomalies made by acoustic micro imaging can be used to evaluate component reliability before assembly, and thus help to predict product reliability in the field. Typically the required quantity of a given component is imaged, and evaluation of each image is performed according to one of the limited number of existing standards. One of the functions of Sonoscan’s laboratory division, known as SonoLab, is the screening of large and small lots of components. The components involved may be lead-frame-based or substrate-based PEMs, ceramic IC packages, various types of flip chips, ceramic chip capacitors, or other types. This article discusses PEMs.

The ultrasonic pulse that an acoustic micro imaging system’s transducer sends into a component is reflected to the transducer by the material interfaces it encounters and converted into a pixel whose brightness depends on the amplitude of the return echo. Internal defects – the conditions that may destroy field reliability – are generally material gaps such as delaminations, cracks or voids. More information about the gap comes from the polarity constituent of the echo. Even if a gap is 0.01µm thick, the interface between the gap and the solid material above it reflects effectively all the ultrasonic pulse. The transducer scanning a tray of components sends thousands of pulses per second into the sample and produces acoustic images that show well-bonded material interfaces in medium tones and gaps as bright white or brightly colored features.

Selecting and modifying a standard. A great deal of the predictive value that can be gained from acoustic micro imaging is determined in the early stages of planning. The basic problem is that none of the various standards (Table 1) for acoustic inspection is likely to be perfect for achieving reliability for a given component in a given application. Those involved need to define precisely what is to be acheived. Acoustic micro imaging will tell the size and location of internal defects. Typically, the goal is to have the highest possible field reliability by removing defective or questionable components before assembly. With careful planning, that goal will probably be reached. If an inspection standard is chosen at random, it may fall short.

[Ed.: To enlarge the figure, right-click on it, then click View Image, then left-click on the figure.]

There are significant differences among the standards listed in Table 1. MIL-STD-883 Method 2030 is limited to die attach evaluation; PEM-INST-001 mentions die attach, but gives no standard. A defect may be called a crack in one standard and a delamination in another. The trick is to find the standard that can best fit a particular component. Often, a standard gives the best results if it is modified to match the component being imaged.

The lots of parts arriving at one of the three SonoLabs are typically destined for use in military, aerospace automotive or medical applications. Some will wind up in high-end commercial products such as servers, in competitive retail products such as cellphones, and in other commercial or retail products where competition or the application demands high reliability. Parts are scanned in trays. Depending on the volume of parts and customer needs, the parts may be scanned on a manual or partly automated C-mode scanning acoustic microscope (CSAM), or on a fully automated tray scanner.

Those who want to classify a part for a certain moisture sensitivity level using J-STD-020 in order to predict reliability may be in for a disappointment. J-STD-020 is really a manufacturing specification. It gives plenty of information about the component, but tests between moisture uptake, baking and reflow may not be what are needed to determine whether components will survive in the field. It’s not safe to assume that acceptable moisture sensitivity level (MSL) information will lead straight to field reliability.

If a key concern is the possibility of field failures caused by defects in the die attach material, the better standard may be MIL-STD-883 Method 2030. This standard wasn’t designed for PEMs; its original purpose was the inspection of power devices in ceramic packages for military applications. More recently, Method 2030 was rewritten to be made more generic and more easily applied to PEMs. The method defines as rejectable any die attach that has voids covering more than 50% of the intended bond area, a single void covering more than 15% of the intended bond area, or a single corner void covering more than 10% of the intended bond area.

J-STD-020 has a similar definition (“No delamination/cracking >50% of the die attach area in thermally enhanced packages or devices that require electrical contact to the backside of the die”) for metal leadframe-based PEMs, but has a different overall purpose. J-STD-020 also requires “no delamination/cracking change >10% through the die attach region” for substrate-based PEMs from before soak until after reflow.”

Method 2030, by itself, might give adequate field reliability for the aforementioned component. The actual danger levels, however, are likely to differ from the percentages in 2030. How long a given PEM will function when it has a particular percentage of delamination in the die attach depends on many factors: the physical characteristics of the die attach material and the substrate material, the rate at which heat is dissipated from this particular package design, and (especially for power devices) the precise locations of hot spots on the die itself. This component might, in the environment in which it will be used, survive for the desired lifespan with 50% of the die attach area voided, or even with 70% of the area voided. But it might also fail in service if only 10% of the die attach area is voided. An acoustic overlay is sometimes made for power devices. When placed over a map of the die, the overlay shows whether any voids lie directly beneath hot spots. Some find a better fit by using MIL-STD-883 Method 2012, which was written for x-ray inspection, but the failure criteria are relevant to acoustic micro imaging. Among its failure criteria: 50% or more total die attach delamination, or a single largest delamination >10% of the die attach area.

To achieve the best results, standards may be modified in other ways. Method 2030 and other standards become more useful when their criteria are modified according to the user’s experience with a particular component. Users may be encouraged to make such modifications in order to prevent the pass/fail criteria from resting solely on definitions that may have been written to pass judgment on a very different component. The three components in Figure 1 have not only varying areas of voids in the die attach area; they have varying distributions of those voids, especially in part C, where most of the 18.43% void area is in a single large void. For one component these percentages and distributions might be acceptable; for another,  especially an application where no single void >10% of the die attach area is permitted, part C might be a reject. The user’s judgment, based on experience with the parts being screened, is critical.

Some of the user’s knowledge about a given component may come from previous field failure data. It is often worthwhile for the customer to conduct life tests in order to examine in detail how various defects change as the component ages and goes through temperature cycles. Customers bringing PEMs to a SonoLab often wind up using Method 2030 as the standard, but they often acquire additional information to refine the criteria.

Figure 2 shows acoustic images of a PEM before life testing (left) and after 1000 cycles (right). Before testing, there are several delaminations (red) on or near wire bonds on the lead fingers. After 1000 cycles, some of these delaminations have grown, and a few new ones have appeared. But the die paddle surrounding the die is now largely delaminated from the mold compound. In service, this delamination might grow to extend under the die.

Other standards are also available for screening components to improve long-term reliability. One is J-STD-035. Unlike J-STD-020, this standard does not address moisture sensitivity. Instead, it simply creates very generic definitions for the anomalies that may appear when transducer pulses ultrasound into the circuit side or the non-circuit side of the package. The seven anomalies are shown in Figure 3.

The evaluation of some defects is essentially cast in stone. Die face delaminations are practically always a cause for rejection, and are thus at the head of the list. Delaminations near lead finger wire bonds are surely risky, but the wire bond is typically a wedge bond, and may, in a particular package, be somewhat better at enduring a delamination.

There is no quantitative definition of the area of an anomaly in J-STD-035. Type 5, for example, seen in Part #7 in Figure 4, simply defines any delamination of the encapsulant from either surface of a lead finger. But the two sides are not equally risky. A delamination on the top side could allow corrosion of the circuit or may expand until it reaches a wire bond, but a delamination on the bottom side is relatively innocuous, unless it somehow propagates to the top side.

J-STD-020 is more comprehensive and rejects any component having an “internal crack extending more than 2/3 the distance from any internal feature to the outside of the package.” This definition encompasses lead finger delaminations, as well as delaminations along tie bars and heat sinks. The relative length of a lead finger delamination may be modified, for example, if the component being imaged has a small die, long wires, and very short lead fingers. The usual modification in this case is to consider a lead finger delamination of any length as cause for rejection.

Some customers use PEM-INST-001, a standard written by NASA before IPC/JEDEC put together J-STD-020. The two standards are similar but not identical. For example, PEM-INST-001 lists as a cause for rejection “Delaminations extending more than 2/3 the length of the internal part of the leads.” J-STD-020 calls such an anomaly an “internal crack extending more than 2/3 the distance from any internal feature to the outside of the package.”

Acoustic micro imaging is most successful at predicting reliability and identifying components likely to fail when engineers 1) select an inspection standard that is well-suited to the part; and 2) modify the standard according to the data they have from life testing, field failures and other sources.

Tom Adams is a consultant to Sonoscan (sonoscan.com); tom100adams@comcast.net.