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simple doubt about reflow profile

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campos

#47575

simple doubt about reflow profile | 12 February, 2007

Hi all,,

I running SMQ230 solder paste with a time above = 40sec with peak temperature = 239 degrees .. the complete reflow takes almost 6 min with a slope (150to190) close to .60 degrees/sec .. may I have some concern about that or it's ok??

tks..

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#47576

simple doubt about reflow profile | 12 February, 2007

Does this meet the SMQ230 recommended time above liquidous? Do you have any parts that cannot withstand 239 degress C? If meet SMQ230's recommended time and temps and your parts are rated for this temp, then you should be OK. The real proof is reflowing a real board and taking the time to look at it.

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CK the Flip Guy

#47577

simple doubt about reflow profile | 12 February, 2007

Looks good at first glance. Couple of questions, though:

Time Above _____. Fill in the blank. Is Liquidous 183C (Tin-Lead) or 217C to 220C (Lead Free)?

The "soak" of 150-190, at 0.6*C per second ramp up looks good, weather it's lead or lead-free.

As for 239*C Peak... If it's Tin-Lead, that's pretty good, but I wouldn't recommend going anywhere more than that. If it's Lead-Free paste, 239*C is a little on the low-side. You should aim for 250*C to 260*C-ish.

Keep in mind, your Indium paste is very sensitive to profiles. They have near-exact requirements for things like ambient-to-peak times, etc... I would get in contact with one of their tech. support guys as well.

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campos

#47581

simple doubt about reflow profile | 12 February, 2007

Tks for the answers,, My concern is about the intermetalic layer,,I run SMQ230 LEAD FREE paste.. its liquidous at 217C..the oven have 7 zone, but I run in 5 zones also with a more agressive profile (due to the line rate)..I would like to know if running this way I may have any problem with the intermetalic layer...tks again..

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dave

#47588

simple doubt about reflow profile | 12 February, 2007

250-260ish seems a little on the high side ?

Depending on the board density and components 230-245 should suffice.

Again time above is usually preferred between 30-90secs but again it really depends on the PCB

Dave

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#47628

simple doubt about reflow profile | 13 February, 2007

Campos, This is a direct reply I recieved from Indium, (thanks to Rich Brooks), in late 2004 regarding SMQ230. I have followed these guidelines with good results using ENIG finish. Same also applies to Indium 5.1 apply to both alloys (SAC 387 and 305) 1. A ramp of 0.5 to 2.0 seconds is fine. I personally like a ramp from 1.5 to 2 sec.

2. Ramp rate can be taken anywhere.... but mainly you want to look at the ramp when the flux is doing its job. For the Indium paste, I would set a ramp rate of 100 to 200 (or 120 to 210).. somewhere in that range should provide the best results. 3. The flux activation will occur between 80 and 210 (can start a room temp)... BUT there are NO set times and temperatures. If you can shoot for a time of 60 to 100 seconds between 100 to 200 C, this should give you good results.... but this is a guideline. You can even have a long soak time of 200 seconds (bet 100 and 200) and still get good results. 4. Cool down rate is only critical from PEAK down to solid state. But you can measure from peak to 200 or even down to 150.... NOTE: The cool down rate is not as critical for Pb-free solder joints, as it was for SnPb. The grain sizes do not differ is size in the Pb-free bulk solder until you get to a cool down rate much greater than 6 degrees per second. I would attempt to get a cool down rate between 2 and 4 degrees C per second. 5. Do not worry about cooling, if you cannot get better than 2 degrees per second it is not a problem ...see question 4. The soak areas can be a lot different then what is suggested (again these are only guidelines). The only critical areas are time above liquidus and peak temperature... PEAK TEMP - attempt to stay between 232C and 240C (for best results) TIME ABOVE LIQ - attempt to stay between 60 and 85 seconds. I like to stay above liquidus for a longer time than SnPb solders because the Pb-free solders do not wet as good as SnPb (means materials do not go into solution as quickly as they do for SnPb solders)

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#47733

simple doubt about reflow profile | 16 February, 2007

Hi Darby,

Where did you get the info. that cooling rate is not-as-critical for lead-free? I'm not doubting you, and I actually want this to be the case. We don't have chillers on our ovens, and on fast profiles, we only achieve 2 to 2.5 deg. / s cooldown rates, tops.

My lead-free literature, which says that lead-free paste needs a more aggresive cooldown rate, somewhere on the order of 4 to 6 deg. C / s, is a little old (about 2 years), so maybe something has changed.

Thanks in advanced.

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#47796

simple doubt about reflow profile | 18 February, 2007

As I stated, the reply was direct from Indium, (thanks to Rich Brooks). The information regarding cool down rates should come from your paste supplier; not an oven supplier; not a generic article on lead free. I just went through the data sheets from the following pastes. AIM NC254 SAC. "Cool down should be controlled within 4 deg/ sec" What does this actually mean? KOKI ECO-PLUS S3X58.... Cool down not mentioned. HERAEUS F640. Cool down not mentioned. AVANTEC 305/405. Cool down not mentioned. AMTECH SYN TECH. -6.0 deg to -0.1 deg over 20 sec. COBAR XM3/5s. Cool down not mentioned. KESTER EM907. Cool down not mentioned. ASAHI V349. Cooling rate 2 to 4 deg/sec. Indium 5.1. Cooling rate 1 to 4 deg/sec

The 4 to 6 range - I think you are probably venturing into CTE mismatch country. Stick with Rich!

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#47802

simple doubt about reflow profile | 19 February, 2007

Darby, thanks for the good info. I actually read an article is Circuits Ass'y that a more rapid cooling rate results in "better diffused tin rich clusters" resulting in better grain structure. But...this article was written by an Oven manfuacturer who wants people to upgrade their ovens.

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#47804

simple doubt about reflow profile | 19 February, 2007

That's why you have to read between the lines of any article. Even with data from a paste manufacturer, it's still a bit fuzzy on how their paste will actually work. Not many companies have their data that solid, so it's better to experiment and measure results..... like an engineer!

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#47884

simple doubt about reflow profile | 21 February, 2007

I here alot of guys at my place talking about cold spots in the oven. You may want to check for them in yours.

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#47900

simple doubt about reflow profile | 22 February, 2007

Those guys didnt suggest you get in there and check did they Mr Wavemaster?

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