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reflow / soldering temperature



reflow / soldering temperature | 5 April, 2001

I would like to have the opinion about the reflow / soldering temperature (smt product with 63:37 alloy):

In the smt business there is different approach:

1st ==> use a solder join temperature of 200/210� whatever the pcb used (tin lead coated or osp or gold fash).

2nd ==> to adapt the temerature to the pcb used:

- Reflow (200-210�) for tin lead coated pcb's (in this case we have just to reflow the solder on the pcb and the tin/lead of the components leads.

- up to 227 � when we use OSP coated on copper pcb's (to rise the eutectic temparature of the Tin/Copper alloy)

- Up to 232 � when we use gold flash on nickel pcb's (to rise the eutectic temparature of the Tin/Ni alloy)

In both case the target is to obtain an eutectique alloy more stable than any intermetalic ones.

What do you think about this, and what is the best way to obtain a good solder join ?

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reflow / soldering temperature | 5 April, 2001

Per our staff here at ACI......... Higher Temperatures maybe necessary to achieve good solder process results. The alloy formed when HASL coating protects the copper is the same as that when OSP provide protection. Temperatures may be increased to improve solder characterization because the flux must react with the OSP to reach the copper. As for Ni, Su reacts more slowly with Ni compared to Cu. More energy is required - more heat or time.

WORD OF CAUTION***Careful with component temperatures as they me sensitive.


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reflow / soldering temperature | 5 April, 2001

I concur with your second approach. A profile needs to be tailored to the design of the board, the components, and the solder paste.

Your first approach seems to try to balance lower quality soldering with a lower process complexity.

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reflow / soldering temperature | 9 April, 2001

CAL's word of caution is right on. We tend to stay in the 220C-225C max. temp. on our profiles, and that's because the last heads up from engineering came on a part with a spec. of 230C max. temp.

We just found out that one of our old SOIC's is spec'd. at a max. of 220C/15 secs. SURPRISE! They haven't been failing, but the other vendor's version of the same part has been failing at a rate of about 4%. Back to the drawing board.

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