LM2903B: Thermal stress after reflow

Chase Jeong

Mastermind 7645 points

Part Number: LM2903B
Other Parts Discussed in Thread: NA555

Tool/software:

Dear TI experts,

My customer wants to know about the thermal stress after reflow process.

They proceed assembly process after reflow, about 230 degree of heat will be made in 30 seconds while assembly process.

Is it okay to LM2903B have such a thermal stress? (230 degree in 30 seconds after reflow)

Please check this issue. Thanks.

Best regards,

Chase

10 months ago

0 Michael Hawkins 10 months ago

TI__Intellectual 1320 points

Hi Chase,

I am in contact with the experts on this topic and will get back to you when they respond.

Thank you,

Michael

0 Chase Jeong 10 months ago in reply to Michael Hawkins

Mastermind 7645 points

Dear Michael,

Thank you for your support.

(I thought NA555 will supported by another expert but you support it too.)

Anyway please let me know if there are updates about the issue above.

Best regards,

Chase

+1 Michael Hawkins 10 months ago in reply to Chase Jeong

TI__Intellectual 1320 points

Hi Chase,

These parts are on different product lines so generally these would be managed by separate groups, so it was good to ask on both products.

MSL Ratings and Reflow Profiles

The reflow process starts on section 3 of this document. Your temp of 230 degrees for 30 seconds is fine if this is your peak temperature, just spend at most 30 seconds in this zone.

The document details Reflow profiles for the preheat, soak, reflow and cooling zones.

Let me know any other questions.

Best,

Michael

0 Michael Hawkins 10 months ago in reply to Michael Hawkins

TI__Intellectual 1320 points

Closing thread, reopen if you need further assistance.

0 Chase Jeong 10 months ago in reply to Michael Hawkins

Mastermind 7645 points

Dear Michael,

Sorry for late reply.

I already checked the document which you linked.

What I want to know is, another 230 degree for 30 seconds of heat will made "after" reflow process.

It means that 2 times of over 200 degrees of heat will made. I want to know these 2 times of heat would be okay to the device,

Please check this issue. Thanks.

Best regards,

Chase

0 Chuck Sins 10 months ago in reply to Chase Jeong

TI__Mastermind 25990 points

Chase

Thanks for your post. We are on holiday break and will review your post on Monday when we return. Sorry our delayed response.

Chuck

0 Paul Grohe 10 months ago in reply to Chase Jeong

TI__Guru 60906 points

Chase,

Is the re-flow wave dip soldering or infrared?

0 Chase Jeong 10 months ago in reply to Paul Grohe

Mastermind 7645 points

Dear Paul,

Thank you for your support.

No, neither wave dip soldering nor infrared.

It is just the process to fix PCB assembly with plastic mold. During this process, 230 degree of heat is necessary to melt plastic mold little bit.

Please check this issue. Thanks,

Best regards,

Chase

+1 Paul Grohe 10 months ago in reply to Chase Jeong

TI__Guru 60906 points

Hello Chase,

The packages are certified for three reflow ramps.

So two should not be an issue. Just keep the temperatures within the parameters shown in the reflow appnote above.

0 Chase Jeong 10 months ago in reply to Paul Grohe

Mastermind 7645 points

Dear Paul,

Thank you for your support.

Could you confirm that all the packages are certified for three reflow ramps?

because I posted another thread about same issue of other device ;

https://e2e.ti.com/support/clock-timing-group/clock-and-timing/f/clock-timing-forum/1442792/na555-thermal-stress-after-reflow

Best regards,

Chase

+1 Paul Grohe 10 months ago in reply to Chase Jeong

TI__Guru 60906 points

Hi Chase,

Three was the response back from the packaging person.

On page 5 of the above appnote, under "Customer Board Assembly Reflow Profile for Lead Free Soldering", the last paragraph states:

"The IC packages are classified according to J-STD-020 and withstand three reflow cycles."

So the appnote and verbal response seems to indicate three..

0 Chase Jeong 10 months ago in reply to Paul Grohe

Mastermind 7645 points

Dear Paul,

Thank you for your support.

I will discuss this issue with my customer, and post another thread if I have more questions.

Best regards,

Chase

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LM2903B: Thermal stress after reflow