Poor Solder on TSOP

I am looking for a little enlightenment with an issue that we have been seeing. We have SMT assemblies with poor solderability on TSOP and mini-QFP type devices. The solder appears to have incomplete reflow and/or grainyness to the joints. Everything else on the board such as chips, j-leads and standard QFPs look good, shiny and well wetted. We are using fresh aqueous paste (Alpha WS609) and a fairly standard profile. Is there some inverse relationship between component/lead mass and thermal absorption that I am missing here? Any inputs would be greatly appreciated. Mike McMonagle Process Engineering Supervisor K*Tec Electronics

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| I am looking for a little enlightenment with an issue that we have been seeing. We have SMT assemblies with poor solderability on TSOP and mini-QFP type devices. The solder appears to have incomplete reflow and/or grainyness to the joints. Everything else on the board such as chips, j-leads and standard QFPs look good, shiny and well wetted. We are using fresh aqueous paste (Alpha WS609) and a fairly standard profile. Is there some inverse relationship between component/lead mass and thermal absorption that I am missing here? Any inputs would be greatly appreciated. | Mike McMonagle | Process Engineering Supervisor | K*Tec Electronics Mike, I had the similar problem as you have now. WS609 aqueous paste are highly sensitive to the reflow dwell time. Max reflow temp < 210�C with dwell time above 183�C not more then 30s . Although it is not the standard profile settings, it works well for us. Try it. We performed cross sectioning and under SEM we found the intermetalic layer thickness at about 1.2 micron. Guess it is Ok.

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| I am looking for a little enlightenment with an issue that we have been seeing. We have SMT assemblies with poor solderability on TSOP and mini-QFP type devices. The solder appears to have incomplete reflow and/or grainyness to the joints. Everything else on the board such as chips, j-leads and standard QFPs look good, shiny and well wetted. We are using fresh aqueous paste (Alpha WS609) and a fairly standard profile. Is there some inverse relationship between component/lead mass and thermal absorption that I am missing here? Any inputs would be greatly appreciated. | Mike McMonagle | Process Engineering Supervisor | K*Tec Electronics Mike, WS609 paste is highly sensitive to the reflow time and it peak temperature. Try this profile: Max temperature < 210�C with time above 183�C for less then 30 sec. Although the profile looks odd, it works well for us. Under the SEM,we found that the intermetalic layer is about 1.5 micron so look OK to us. rgs, chiakl

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| | I am looking for a little enlightenment with an issue that we have been seeing. We have SMT assemblies with poor solderability on TSOP and mini-QFP type devices. The solder appears to have incomplete reflow and/or grainyness to the joints. Everything else on the board such as chips, j-leads and standard QFPs look good, shiny and well wetted. We are using fresh aqueous paste (Alpha WS609) and a fairly standard profile. Is there some inverse relationship between component/lead mass and thermal absorption that I am missing here? Any inputs would be greatly appreciated. | | Mike McMonagle | | Process Engineering Supervisor | | K*Tec Electronics | Mike, | WS609 paste is highly sensitive to the reflow time and it peak temperature. Try this profile: Max temperature < 210�C with time above 183�C for less then 30 sec. | Although the profile looks odd, it works well for us. | Under the SEM,we found that the intermetalic layer is about 1.5 micron so look OK to us. | rgs, | chiakl Mike, I suggest that you'll take a careful look on the component's leads. You may find some corrosion or bad coating. Rgds. Michael

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| | | | I am looking for a little enlightenment with an issue that we have been seeing. We have SMT assemblies with poor solderability on TSOP and mini-QFP type devices. The solder appears to have incomplete reflow and/or grainyness to the joints. Everything else on the board such as chips, j-leads and standard QFPs look good, shiny and well wetted. We are using fresh aqueous paste (Alpha WS609) and a fairly standard profile. Is there some inverse relationship between component/lead mass and thermal absorption that I am missing here? Any inputs would be greatly appreciated. | | | Mike McMonagle | | | Process Engineering Supervisor | | | K*Tec Electronics | | Mike, | | WS609 paste is highly sensitive to the reflow time and it peak temperature. Try this profile: Max temperature < 210�C with time above 183�C for less then 30 sec. | | Although the profile looks odd, it works well for us. | | Under the SEM,we found that the intermetalic layer is about 1.5 micron so look OK to us. | | rgs, | | chiakl | Mike, | I suggest that you'll take a careful look on the component's leads. You may find some corrosion or bad coating. | Rgds. | Michael TSOP components normally require Baking.Did you bake the component before you process it?

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