Trying to determine if outsourcing is right for your company? Wishing you could find a contractor willing to give you advice on your options rather than just selling you “one size fits all” services? We’ve created this blog to help companies wanting to answer those questions. Our posts will include helpful tips on choosing the right outsourcing partner, information on upcoming conferences and events we participate in, success stories, and short articles on processes or technology that can save time or enhance quality. We welcome your feedback and comments.
Spectrum Assembly, Inc.’s Mydata MY500 inkjet printer helps it address customer quality challenges “on the fly.” For example, one PCBA had a QFN device that was driving solder bridging. A 2:1 ratio was used across the stencil. Even with adjustments to screen apertures that varied paste deposition by component, significant defects were occurring because solder paste height could not be reduced sufficiently under the QFN. In a panel of 36 assemblies, 26 had solder bridges using traditional screen printing. Utilizing a standard profile, the MY500 reduced solder bridges to 6 per panel. The production team reprogrammed the machine to dispense a smaller amount of paste under the QFN and completely eliminated all solder bridges.
In addition to “on the fly” programming changes, here are six more benefits of this highly flexible inkjet printer:
- Adjustable solder height
- Eliminates need for stencils
- Reduced NRE fees
- Eliminates defects that can occur from worn or clogged stencils
- Ability to print paste on PCBAs with components already mounted
- Instant changeover from leaded to lead-free.
Spectrum Assembly, Inc. will be exhibiting in Booths 302 and 304 (Bing Crosby Hall) at the Del Mar Electronics and Manufacturing Show. Access your free registration here.
Jimmy Durante Blvd, Del Mar, CA
In February, we looked at some of the common DFM mistakes that SAI helps its customers eliminate. Here are some of the common mistakes to avoid in design for assembly (DFA):
- Cable specification issues: IPC guidelines require specific wire gauges be used with specific terminal types. Use of the wrong wire gauge can result in wires coming loose or breaking off the terminal during normal use or maintenance activities. Lack of specifications such as failure to list tolerances or clarifying whether the cable length includes the connector or is simply the inside length are also issues.
- Assembly routing: The order in which cabling and tubing is assembled can impact both efficiency and product performance. An efficient routing sequences the cable harness assembly steps in a way that does not require the operator to have to work around previously installed harnesses. When tubing carrying air liquid is also involved, it is important to ensure the tubing is not accidently crimped by either its placement location in relation to harnesses or a harness tie down.
- Documentation formatting: the more complex a product, the more important electronic documentation becomes because it enables sorting and searching within the files. When documentation such as bills of materials (BOMs) are submitted as PDFs, they must be converted via optical character recognition (OCR) scanners. This can add errors to documentation. The preferred format would be an Excel file or a comma or tab-delimited text file.
- Missing BOM items: Sometimes consumables such as adhesives, zip ties or Lock-tite are not listed as a line item on the BOM. In addition to the quoting inaccuracy this can cause, it also can create confusion on the preferred product to use.
- Missing test and programming requirements: Sometimes functional test and programming requirements are listed only in the test instructions or not all steps are written down. There are often “tribal knowledge” issues that aren’t always conveyed to the contract manufacturer in testing.
Spectrum Assembly Inc. won awards for Responsiveness, Technology and Value for Price for EMS companies with revenues under $20 million at the 2018 Service Excellence Awards (SEA) for Electronics Manufacturing Services (EMS) providers. The awards program was sponsored by Circuits Assembly magazine and recognized EMS companies that received the highest customer service ratings as judged by their own customers through a third party. The ceremony was held on Feb. 27, at the IPC APEX Expo in San Diego, CA.
This is the sixth year that SAI has won one or more categories in the SEA awards.
This quarter’s newsletter focuses on ways SAI is helping one customer improve patient quality of life, Part I in a series of common mistakes to avoid in product design and our trade show activities. Read the full issue here.
SAI’s TransferAssist team works with customers to ensure their projects are ready for outsourcing. The process includes a review of fabrication and Gerber files. Afterwards, the team makes recommendations for improving the design and/or documentation to better accommodate the requirements of a volume manufacturing process optimized for increased throughput with minimal handling.
In the design for manufacturability (DFM) realm, seven common mistakes stand out:
- Panelization issues: this is an area where working with your contract manufacturer can be critical, as many contract manufacturers have specific guidelines on preferred printed circuit board (PCB) sizing and orientation for fast setups and maximum throughput. Additionally, the panelization strategy should be reviewed to determine if it is the most efficient layout in terms of minimizing wasted FR4.
- Connector placement: Edge mounts must be kept on PCBs through processing. Depaneling tools cannot be used if a right angle connector is placed on a side of the PCB containing an edge mount. The only option for that type of layout is to depanel using manual force, which can negatively impact solder joint integrity. Consequently, it is important to consider panelization strategy in PCB layout when determining connector placement.
- Documentation: Gerber files are often transferred as single-up designs instead of as a panelized design. This adds additional work during project transfer.
- Stencil paste file errors: Optimum paste deposition often requires an aperture design that varies from the component footprint. Many Gerber stencil paste files are prepared 1:1, which doesn’t account for the impact of component mass in paste deposited via the screen aperture. Component manufacturers list recommended specifications and many contract manufacturers have an aperture design preference for specific types of components. For example, SAI has found that LED diodes are best placed when a triangular shaped solder paste aperture is used. Its team reviews the parts with critical paste deposition requirements prior to ordering the screen.
- Fiducials: Fiducials are marks placed on the PCB to enable machine vision systems to understand the position of the component placement head relative to the PCB. Most PCB layout teams are good at adding fiducials to the PCB layout. However, some FR4 masking colors can make fiducials hard to read or invisible because the color of the mask is the same or lighter contrast than the fiducials. Machine algorithms can be adjusted to change fiducial brightness in most cases. Another option is to avoid masking over the fiducial. The most difficult color to compensate for is yellow. In this case, the “no mask” area should have a wide clearance for fiducials.
- PCB finish mismatch: In some cases, a designer will specify a HASL finish for use with lead-free solder. HASL finishes do not have a flat coplanarity and in a lead-free reflow process can create coplanarity issues. An ENIG finish is generally preferred for use with lead-free solder. The team at SAI most often sees this issue when working with consigned materials.
- Failure to utilize recommended pad layout size: Misalignment and other solder joint integrity issues can occur if the correct pad layout size for the specified component package is not used.
Spectrum Assembly, Inc. is experienced in placing components on wide range of substrate materials, including flex circuit assemblies. At SAI, medical and consumer products tend to be the primary users of flex circuit technology.
While SAI’s existing equipment easily accommodates flex circuit placement, strong focus must be placed on stabilizing the substrate during handling activities. Fixturing is an integral part of building high quality flex circuits. SAI utilizes 3D Solidworks, CAD or Gerber data to design carriers able to provide a rigid surface as the flex circuits go through stencil printing, pick and place and reflow. If an aqueous wash is required, a carrier must be designed for that as well. The goal is to utilize tooling holes in the fixtures to keep the substrate flat and rigid as it moves through the processes.
Understanding the end configuration, is critical to good flex circuit design. When a PCB layout designer lays out a rigid printed circuit board assembly (PCBA) it is fairly easy to understand the areas where design rules need to be followed in terms of clearances. With flex circuits, the designer needs to think three dimensionally in terms of locating points of interconnect, since the flex circuits are folded up and put in tight enclosures. If a point of interconnect is too close to a fold, it can create stress on the solder joint and result in a point of failure. Size of components may also create a design constraint. For example, a product with a long connector may be better designed as a rigid flex assembly than as a 100 percent flex assembly.
Equipment choices also matter. When rigid flex combinations or stiffeners are in use, there are two different heights which makes it impossible to screen print without specialized fixturing. Paste jet printers like the MY500 SAI uses are more adjustable and do not have that constraint because it allows us to tailor the amount of solder on individual components without the use of a stencil.
SAI’s Heller reflow ovens with KIC smart oven technology automatically verify in real-time that each assembly is processed in spec. This is critical with flex circuits because the carriers have a thermal mass impact and concomitantly increase the complexity of the reflow process.
The team at SAI also takes extra care in handling during secondary operations, since any flexing of the material puts stress on solder joints, particularly in the case of ceramic capacitors or other large ICs.