Week #13: Soldering, Surface Mount Components & RoHS Compliance

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rjagodowski
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Joined: Fri Sep 04, 2015 6:59 pm

Week #13: Soldering, Surface Mount Components & RoHS Compliance

Post by rjagodowski »

NOTE: Our class time for Week #13 was lost due to the schedule change around the Patriot's Day Holiday observance on 4/18. This time will be made up during the next few weeks so the Week #'s of the forum topics might not exactly align to the calendar.

We'll begin this weeks discussion finishing up from Week #11 & #12 on shielding and EM Compatibility.

This week we will discuss the topics of Soldering (through-hole and surface mount) and RoHS Compliance with special emphasis on lead-free solder and its related issues.

For Soldering Fundamentals, Through-Hole soldering and RoHS, the content is posted here in Week #11 & #12 of EET-265.

Surface mount content is posted below:

Acronyms: SMT = Surface Mount Technology
SMD = Surface Mount Device
PCB = Printed Circuit Board

First and foremost, surface mount devices are smaller than through-hole mount components and therefore require much greater care and precision when constructing and repairing SMT circuit boards. A good magnifying glass, possibly even a microscope, with strong light is important to be able to see minute solder bridges or unsoldered connections on surface mount boards. The plus side is that the SMT construction lends itself to automated PCB assembly processes.

For automated processes, components are commonly held in place and then soldered using solder paste. Note, this is not the same as solder flux, which is used with conventional solders to aid in creating a quality solder joint. Solder paste is a thick flux which contains very small beads of solder. When heated, the flux melts cleaning the surfaces to be soldered and keeping oxygen away from the heated metals to get a high quality connection.

Here's an article about Solder Paste from Wikipedia.

Circuit Board Assembly at SMA's German Factory (8:21) shows great views of automated assembly of modern electronic circuit boards.

SMA-America Solar Inverters home page.

The next several links all come from Electronics-Notes.com which has numerous articles on electronics and radio circuits. Overall, it's a very good resource technically, but sometimes grammatical and spelling errors crop up.

Surface Mount Technology..

Surface Mount Components and Packages, sizes & details.

Here's a resistor code calculator for SMT resistors.

Suface Mount Resistor Codes These components are too small for color codes. Even reading the lettering is difficult enough.

SMD Quad Flat Pack (QFP) (common SMD form factor).

Ball-Grid Array (BGA) Packages (pins are UNDERNEATH the chip) .

Plastic Leaded Chip Carrier (PLCC) ("J" lead folds under the chip requiring less space and these may be used with PLCC sockets for applications where updated chips might need to be added).





Surface mount video content is posted below:

Master Soldering: IPC-J-STD-001 Soldering Techniques (2:57)

Surface Mount - Fine Pitch with solder bridge correction. (4:00)

SMD Soldering using Solder Paste and a Hot Air Soldering Tool. (2:49) If you don't have to do a lot of SMD soldering this method allows you to solder most types of components using the hot-air soldering tool.
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