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SMT Component Design Requirements

Eric Reno

#22028

SMT Component Design Requirements | 18 October, 2002

Hello All, I need some help here. Can anyone point me in the right direction on how to get SMT component design requirements? What I'm looking for specifically is how the component leads would come off the components to make contact with the SMT pad screened with solder paste. Thank you in advance for the help.

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RDR

#22031

SMT Component Design Requirements | 18 October, 2002

What kind of packages are we talking about here? If I understand your question, the leads come out of the body and bend downward resting on the board surface

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Eric Reno

#22032

SMT Component Design Requirements | 18 October, 2002

We have a connector mfg that claims that their design is good and does not contribute to the problem that we are having. The problem is evidence of poor soldering. All other components that surround this connector have very good solder joints, with the exception of the connector. Temperature profile has been confirmed as being correct and the PCB shows no evidence of warpage, discoloration and contamination (before or after SMT).

The connector was examined mechanically and was determined that the foot of the is ~ 0.02-0.06 mm above the plastic body of the connector. There spec calls out 0.1mm as a tolerance. So this means that the connector is within their spec. Now a Molex part has their leads below the plastic body by ~0.05mm. This allows the leads to make contact with the SMT pad when placed through the solder paste.

Since we had purchased 40K connectors I need to prove that these bad connectors (not Molex) are not designed for proper SMT operations. This is why I'm looking for SMT Component design requirements.

Best Regards, Eric Reno

FinePoint Innovations, Inc. Manufacturing / Production Engineer 1220 South Park Lane, Suite 1 Tempe, Arizona 85281-6940 USA Ph: 602-325-2099 (Direct Line) Ph: 602-325-2080 (Main) Fx: 480-967-9427 Email: ereno@finepointinnovations.com ereno@fpi2.com Web: http://www.finepointinnovations.com http://www.fpi2.com

_______ PRIVILEGED & PROPRIETARY _______ This material is for the sole use of the intended recipient(s) and is to be considered proprietary and privileged information. The intended recipient(s) have direct permission to use the information for the sole purpose as directed by FPI. Any unauthorized review, use, disclosure or distribution is prohibited. Modifications to any file(s) are not valid unless prior written approval from FinePoint Innovations is given. __________________________________________

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RDR

#22033

SMT Component Design Requirements | 18 October, 2002

What is the determination of poor soldering fails pull test, non-wetting, visual)?

I have never heard of an SMT component that has leads higher than the body of the component. Refer to IPC 782 3.6.1.7 it provide the guidelines for SMT standoff height (cleaning is the concern). .1mm below the body is the standard that I have seen on most all components that I have ever dealt with. However, it seems to me that this standoff height is very minimal (.02-.06mm) and I wouldn't think that this would/should cause a problem unless you are printing at 5mil or less thickness (Just an opinion, never proven out). What is the lead finish? have the leads been tested for contamination or oxidization? How big is this connector? Could it be that during cooling the part is tilting forward causing disturbed solder (I don't know if that is possible, maybe someone else could jump in here).

I would have the supplier prove to you that they can make it work on your product and then the answer will become apparent.

Russ

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