Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


External Factors to be controlled during assembly

Nankar

#17728

External Factors to be controlled during assembly | 27 September, 2001

what factors should be monitored and controlled during assembly of components on PCBs and their storage? Temperature and humidity seem obvious. Should one also watch out for any particular gases that may cause oxidation? Or dust?

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#17733

External Factors to be controlled during assembly | 27 September, 2001

All of the discussion of "environmental controls" are a matter of degree, dependent on the requirements of the product that you manufacture. For example: shops assembling under-the-hood products have different requirements than shops making garage door openers.

Continuing on your points about temperature, humidity, and dust control; J-STD-001 uses wording to the effect of: The soldering facility should be [meaning you can do it if you want to do it] enclosed, temperature and humidity controlled, and maintained at a positive pressure. Para. 3.6.2 discusses the temperature and humidity control further. Humidity control "shalls" focus on ESD control issues. Temperature control "shoulds" focus on employee comfort. Almost back handedly, para. 3.6.2 further states that more restrictive temperature and humidity controls "may be" required for process control purposes.

J-STD-001 states that eating, drinking, and use of tobacco products "shall be" prohibited from the work area.

The in a sweeping gesture, J-STD-001 states that cleanliness and ambient environment in all work areas "shall be" maintained at levels that prevent contamination or deterioration of soldering tools, materials, and surfaces to be soldered. In line with this, we keep: * Brown paper and cardboard away from boards and solderable surfaces, because some contain sulfur. Theoretically, sulfates, like the halides, can cause corrosion and metal migration when present in high enough amounts. But how high is the borderline amount? It is difficult to say, since different assemblies have differing sensitivities to various residues. Sulfate can combine with unprotected copper [cooper sulfate] and can corrode silver alloys. * Silicone away from solderable surfaces, because it covers areas to be fluxed [that might not be the correct technical term, may be someone can help explain the action better] and is virtually impossible to remove.

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Juergen

#17739

External Factors to be controlled during assembly | 29 September, 2001

Hello Dave, I was looking for the standard J-STD-001 you mentioned, but I coudn't find it. Was it withdrawn?

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#17741

External Factors to be controlled during assembly | 29 September, 2001

The current version of ANSI/J-STD-001, "Requiremnts For Soldered Electrical & Electronis Assemblies" is C [3/00]. The following sources can help you: * IPC http://www.ipc.org * SMTA http://www.smta.org * Document Center http://www.document-center.com * ANSI http://www.ansi.org

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