As a result of this expansion the substrate, the die, or the wire bonds could be damaged. The damage is often invisible and requires X-ray equipment to conduct a proper analysis. When the anti-static bag is opened and the ICs are exposed to ambient conditions, the moisture in the air is trapped inside the device. This means that during the PCB assembly process e. The bags shall be heat sealable. Desiccant shall be dustless, non-corrosive, and absorbent to amounts specified in the standard.
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Arajind Already Subscribed to this document. This standard is also available to be included in Standards Subscriptions. Blister onset temperature is dependent upon several factors, including wall thickness, percentage of moisture in the part, speed of connector heating, and peak temperature of the reflow process. You can download and open this file to your own computer but DRM prevents opening this file on another computer, including a networked server. Standards Subscriptions from ANSI provides a money-saving, multi-user solution for accessing standards.
Proceed to Checkout Continue Shopping. Please first log in with a verified email before subscribing to alerts. Many Asian OEMs, who have been converting to the lead-free solder process for the last few years, require that their connectors be packaged to minimize moisture absorption for this reason. Minimizing Effects of Lead-free SMT Assembly on Connector Housing Resins They were subjected to two different storage conditions: For standard MBB sizes used for shipping connectors loose or on reels the amount of desiccant required is less than two units.
Many connector suppliers are eliminating, or have already eliminated, lead from their contact plating process. For ease of use, the halogen moisture analyzer was considered the best. The vapor pressure of moisture and other gases trapped inside the walls of a plastic connector increase rapidly when the connector is exposed to the high temperatures of solder reflow. The key parameter in blistering of connector housings is the control of moisture absorption tsd the molded parts. Approved options include clay and silica gel.
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These methods help avoid damage from moisture absorption and exposure to solder reflow temperatures that can result in yield and reliability degradation. We have no amendments or corrections for this standard. The next phase will be lead-free solder compliance for board assembly. If all moisture absorption precautions are taken and connectors are still exhibiting some delamination during SMT assembly, measuring the amount of moisture in the parts to determine the steps required to solder without connector blistering may be required.
The company has analyzed the types of bags that are available for connector packaging and come up with some recommendations based upon WVTR ratings Table 2. As the voice of the U. All techniques provided similar moisture percentages in parts. MBBs in two different thicknesses 0. Table 3 shows that, at the storage conditions of an air-conditioned warehouse in Southeast Asia Condition 1even the thinnest s LDPE bag would provide enough moisture protection to keep the connectors below the blister threshold level for 90 days.
This standard is not included in any packages. Effectiveness of desiccant on moisture absorption of packaged connectors. Board assemblers have focused on handling more expensive ICs but have failed to take similar precautions with board connectors. Subscription pricing is determined by: Your Alert Profile lists the documents that will be monitored.
The higher the peak temperature, the lower the moisture content can jeedec before blistering. Lead-free solders result in higher peak temperatures, meaning more blistering. The higher preheat temperatures typical in lead-free solder profiles may provide more safety from blistering for thinner-walled parts than current tin-lead solder profiles due to the direct relationship between moisture desorption rate and temperature. In this stage, the higher liquidus temperatures required for lead-free solders may have a profound effect on the connector insulator housings.
But the problems listed previously for connectors in these hot oven environments can also result in board rework. Figures 1 and 2.
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