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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


SOIC FAIL

Joseph

#31085

SOIC FAIL | 26 October, 2004

Dear all, Recently our production encountered high SOIC failure during testing after reflow soldering. All solder fillets (side/heel) are acceptable as per IPC standard.The reject samples (SOIC)being sent to IC manufacturer to verify the failure. Finally result came out stated that the mechanism of SOIC failure is NOT related to an anomaly within the SOIC (the SOIC is perfect). Different solder pastes being (with higher flux activity) evaluated but result is slightly better. Can anyone share your views on these problem ? (the IC is designed for transmission purpose) Thks

Joseph

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Simon UK

#31089

SOIC FAIL | 26 October, 2004

DO you have an xray onsite?

One suggestion is to check what you can with that machine, i know it wont be able to magnify to 200nm or something, but it will show any ESD damage to the wire bonds or any major cracks of the silicon die.

P.s. Most device manufacturers are bulls*iter's (I used to work for one!) They always maintain, you are at fault and they are not!.

Check, Bake, Place, Reflow and check again, if no better reject the rest of the reel to the manufacturer and obtain a newer reel of a different date code.

Simon UK

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Paul_pmd

#31090

SOIC FAIL | 26 October, 2004

Have the SOIC tested by independant. Clarify as to weather or not you have run this board before. Check to see if the board has been rev'ed. Sometimes IC's are rated at a clock speed or by axcess time. Engneering on this board may be at the tolorance of this part. As clock rates increase some older TTL( 74 serries transistor to transistor logic ) chips cant keep up. If you have good wetting and do not have thermal shock to the components and no mechanical shock degridration, then you probably should start looking at the PCB. Maybe internal layers could be at fault. Have you replaced any failure IC's and got it working with replacement's to rule out PCB failure. Failures of IC's can also be attributed to voltage supply at the IC's. Usually they install a 0.1 cap near the IC to help supply the part with reserve power when needed. Many things can cause failure in a circuit even when all parts are good. Other circuit components can change the charistics of a given IC, Input levels and output levels can cause problems. Look at interconecting circuitry as a possable culpret. Change vendor for compairison results.

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#31098

SOIC FAIL | 26 October, 2004

More background please: * What is the condition of failure [eg, part damaged, part poorly attached, etc] * You mention heel and side fillets. What about under the component? * Are the components properly attached? Or are they floating on a bed of flux residue? * When you peel one of the leads off the board with a pair of needle nose pliers, what is the appearance of the pad? What is the appearance of the soldered portion of the lead?

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Joseph

#31105

SOIC FAIL | 27 October, 2004

Dear all,

The problematic IC being X-rays and shown excellent wetting with no solder voids. Meanwhile the samples to be sent for independent party to verify the failure, e.g. using SAM method. The condition of failure is the PCB assembly fail functional testing, with good wetting apperance on pad and IC lead even after remove it with plier.

Thks

Joseph

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