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December 20, 2006

Component baking issues

We have a big problem and could use your help for MSD components baking issue. If we follow IPC J-STD-033B standard, 3 level baking of 125 degree, 90 degree and 40 degree can be chosen, for Tray package MSD, it is not a problem to bake as the standard. But for reel and tube package MSD, they can't bake at 125 & 90 degree because most of the packages can't endure the high temperature and will deform. So we can only apply low temperature 40 degree baking but the lead time is so long and conflicts with our production schedule.

Based on our experiences, we prefer to use 70 degree baking, for reel and tubes which is much more convenient and effective. But our customers have challenged us on it due to it not an industry standard.

Could you give us some advice? If we want to apply 70 degree baking, how long the baking time is appropriate? Thanks and I await your feedback!

TH Liang

Experts Comments

I responded to a similar question a few months ago. My experience has been with circuit boards more than reel and tubes, but I have a suggestion that might be helpful.

A simple and straightforward way to get an indication of moisture is to measure weight gain. In circuit boards, the weight gain due to moisture can be a few percentage points, depending on the humidity. I'm not sure what it would be in the components you have. Here's what I would suggest:

1) take a sample of your components and weigh them prior to baking. You have to pick a size so the total weight matches the range of the scale (lab balance) you are using. For example, if you have an electronic balance with a capacity of 100 g, you might want to take a sample of 50 g to 80 g. In fact, you should probably get several samples and weigh them independently.

2) Treat your samples according to the IPC standard, allow them to cool in a dry environment (dry box)?

3) Re-weigh the samples. Assume that the weight difference is moisture. With a little luck, you will have enough weight difference to document. Multiple samples help give you a good statistical number.

4) Repeat the test with your desired temperature profile. You can use this test to find out how much time is required at this temperature.

Again, I don't know if there is enough moisture content to weigh, but this is a good way to provide documentation for your desired process if it works.

Alan Lewis
Director of Application Engineering
Mr. Lewis worked for The Aerospace Corporation for 6 years before joining Asymtek in 1993. He holds multiple patents in dispensing technology for electronics assembly and packaging. He has a Master's Degree in Mechanical Engineering from University of Missouri-Rolla.
NOTE: Mr. Lewis is no longer working at Asymtek.
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