Page 32
www.us-
tech.com
August, 2014
Cleanliness of Electronic PCB Assemblies Aids Reliability of Medical Devices
By Mo Ohady and David Estes, Digicom Electronics, Oakland, CA
ponents that are mere fractions of a millimeter and have board-to-compo- nent clearances of less than 1 mil. Pick-and-place machines offer new accessories that allow placement of these almost invisible parts. Compo- nents are placed so close together that effectively cleaning under these parts would appear difficult. The use of lead-free solder in
C
electronic circuits and assemblies has necessitated new solder, new fluxes, higher processing tempera- tures, and new solder processing equipment. Many new approaches, alloys,
chemicals, and soldering processes have been developed to address these issues. Tin whisker problems have also increased dramatically. Time- delay effects, however, often will not surface until an item is being pro- duced and has been in service for even a year or more. Product devel- opment rates, with new models avail- able every year, can cover up these time-delay issues. For some electron- ic products, such as cellular tele- phones, problems may not surface since few people are using a two-to- three-year-old mobile phone. Repair
omponent manufacturers are continually developing new and smaller packages for com-
of an old mobile phones may not be considered a viable option when an upgraded feature-rich model is avail-
dressed on the manufacturing floor, but often component manufacturers, board designers, and manufacturers
ly cleaned of contaminants left over from the manufacturing process. There may also be some difficult de- sign issues for a PCB whose close quarters have resulted from the use of the advanced computer-aided-de- sign (CAD) software used to design the PCB, such as ground points too close to a power bus. Many designers have little exposure to the production issues of PCB fabrication or board as- sembly. It’s important for a board de- signer to understand how flux from the hand soldering process of a con- nector can flow to a microviahole placed near a connector pad. The de- sign of a PCB can have considerable impact on the other processing steps used to manufacture that PCB. IPC (
www.ipc.org), the Associa-
Before and after views of the result of effective cleaning.
able at a subsidized price. For medical devices, however,
the potential for failure is very real and the effects of failure can be dev- astating. Time-delay problems can be ad-
operate independently of one another and there is a lack of communication about any potential problems. Re- search shows that many failures are a result of printed circuit boards (PCBs) that have not been adequate-
REFLOW
tion Connecting Electronics Indus- tries, is a global trade association serving the PCB and electronics as- sembly industries, their customers, and suppliers. It has a task group de- voted to addressing all topics con- nected with determining the cleanli- ness levels of unpopulated (bare) printed circuit boards and has estab- lished a base standard for cleanli- ness. The IPC-TM-650 standard sets an acceptable range of 10-2 µg/in.2 of sodium chloride (NaCl). Is this stan-
Continued on next page
SOLDERING SYSTEMS
See us at
IMAPS 2014 Booth 213
FALCON ULTRA PROFILE 1200 Small Footprint • Effi cient Power Use
Consistent High Yields • Precise Temperature Gradient Organize and Reduce the Bone Pile
Do you have limited or no documentation, circuit card orphans or older legacy systems that need to be supported? The Huntron Workstation software provides the path to creating usable, repeatable, test procedures.
To learn more about repeatable test procedures, call or click, 800-426-9265 or
www.huntron.com
See at AUTOTEST, Booth 208
SIKAMA INTERNATIONAL, INC.
www.sikama.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84