Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Dennis Xiong

#12464

Unwetting leads of Palladium Plated Pins | 1 March, 1999

Hello! SMT professionals,

I do not know if anyone posted this question before. Last week, I reflowed our newly designed thin Rigid-Flex pcb with 0.040" thickness. I found all of pins of a TQFP48 ic did not get wetted. I could see on the heel side of pin foot there is a clear unwetting line between pin and solder. Other components including bigger IC and heavy thermal mass parts on the board are soldered very good. I found this TQFP48 is made by Texas Instruments, and is Palladium Plated leads.

Does anyone have this unwetting problem on Palladium Plated leads? How do you solve the problem? I thank for any help, advise and suggestion you could give.

By the way, I am using a Vitronics Unitherm520 air convection oven with 5 heat zone. The profile gets peak temp. of 225 degree c.

Regards,

Dennis

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justin medernach

#12465

Re: Unwetting leads of Palladium Plated Pins | 1 March, 1999

| Hello! SMT professionals, | | I do not know if anyone posted this question before. | Last week, I reflowed our newly designed thin Rigid-Flex pcb with 0.040" thickness. I found all of pins of a TQFP48 ic did not get wetted. I could see on the heel side of pin foot there is a clear unwetting line between pin and solder. Other components including bigger IC and heavy thermal mass parts on the board are soldered very good. I found this TQFP48 is made by Texas Instruments, and is Palladium Plated leads. | | Does anyone have this unwetting problem on Palladium Plated leads? How do you solve the problem? I thank for any help, advise and suggestion you could give. | | By the way, I am using a Vitronics Unitherm520 air convection oven with 5 heat zone. The profile gets peak temp. of 225 degree c. | | Regards, | | Dennis | Dennis, Palladium requires a higher reflow temperature to solder well. However, I suggest you check the activity of your flux system to make sure it has enough "muscle" to solder the palladium. It should. Typically, a 15 degree increase is enough to get good solderability. Also, make sure the paste used to solder that device wasn't past its' stencil life. If the paste was on the stencil too long, the flux would have evaporated enough that there wasn't a sufficient amount to solder the palladium but the tin/lead would still reflow fine.

Regards, Justin Medernach

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#12466

Re: Unwetting leads of Palladium Plated Pins | 1 March, 1999

| Hello! SMT professionals, | | I do not know if anyone posted this question before. | Last week, I reflowed our newly designed thin Rigid-Flex pcb with 0.040" thickness. I found all of pins of a TQFP48 ic did not get wetted. I could see on the heel side of pin foot there is a clear unwetting line between pin and solder. Other components including bigger IC and heavy thermal mass parts on the board are soldered very good. I found this TQFP48 is made by Texas Instruments, and is Palladium Plated leads. | | Does anyone have this unwetting problem on Palladium Plated leads? How do you solve the problem? I thank for any help, advise and suggestion you could give. | | By the way, I am using a Vitronics Unitherm520 air convection oven with 5 heat zone. The profile gets peak temp. of 225 degree c. | | Regards, | | Dennis | Let's not carry that "professionals" thing to far Dennis. TI has addressed some of your concerns. Check the link below. TTYL Dave F

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