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Moisture Sensitive part - baking

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Moisture Sensitive part - baking | 24 August, 2007

I have an MSL3 part (a relay) supplied in tape and reel. From what I am able to determine, these parts require baking at 257 degrees F for a minimum of 8 hours once the integrity of the seal is broken for over 168 hours.

How are parts baked at this temperature without melting the reel, the embossed tape and totally hosing the parts?

Been here, done it ... got the shirt. Need some advice!!!

Thanks! Pete

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Moisture Sensitive part - baking | 24 August, 2007

Oh, for a second there I thought it was 257 C, not F. Solder temperature! Still, one WEEK at 257 F seems way extreme. Maybe this is to bake out a part that has been underwater for a week.

Is this a military part? I can't imagine any commercial-grade part with plastic case that could handle this kind of long-term heat. Maybe automotive parts for under-hood use.


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Moisture Sensitive part - baking | 25 August, 2007

We're unfamiliar with such component dryout requirements. Commonly, tape & reel cover tape will seperate at 60*C. So, even if your baking on a metal reel, your should keep the bake temperature ~40*C.

Sure makes you want to use these parts during the shift that you open them doesn't it?

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Moisture Sensitive part - baking | 25 August, 2007

If plastic Carrier Tape (CT)/ emboss tape, is made by:

a)Polycarbonate material, it can withstand temperature around 120C� or may be more mantaining original dimension.

b)Polystirene material, at max 45�C-50C� the CT starts to change dimensions and get damaged.

So in case of a) you could make a dry-off/backe(ie. by using Oven air convection), setting temp max 110�C for a 16 h max 24h . For sure you have to remove CT (and Relays) from reel. Reel gets damaged after 50 to 60 C�.

In case of b) you have to remove relays from CT, removing cover tape first and be careful do not damage leads of relays (are them SMD Relays ?) then put them on a tray or a flat metal sheet, then load inside oven set at 110/125�C for 16 h to 24h max. After dry-off, relays must be tape and reeled again.

OVEN + VACUUM By using an oven with vacuum, you can dry-off relays by setting temperature at 45-50�C , and a not so high vacuum level ( ie. 350 mmHg can be enough, more vacuum value could damage the CT and component leads) for about 12-24 hours. In this case no matter about plastic material (Carrier Tape and Reel)

If you have plenty of time available, and a Dry Box or Dry Cabinet, with 2% or 5% RH inside the cabinet, you can put the Reel inside(Relay and CT as they are), and leave it for 4 wks or longer (it depend wich kind and size is the relay and if 2% or 5% RH are available.

If you have plenty of time available but not dry box available, you can use an oven (dry-air), set it at 45�C max, put the reel inside and leave it "cooking" for at least 4 wks or longer (again it depends from type end size of relay).

Have a good luck.

Best Regards....GSx

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Moisture Sensitive part - baking | 30 August, 2007

According to J-STD-033 Table 4-1, the bake out time to restore the clock to zero is not only determined by the MSL level, but the package thickness as well. Section 4.2.2 states "SMD packages shipped in low temperature carriers may not be baked in the carriers at any temperature greater than 40�C"

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