BGA soldering quality with Kayo reflow RF630 vs RF835

[rishibhanot]

Hi there,
I am very new to this forum in fact this is my very first post. In the last few days i read many pages here around re flow ovens and general recommendations.
And in hardware manufacturing (smt line) i do not have any first hand experience till now. Our product which we do around 3-5K per year is done at big bangkok PCBA factory. Befreo my question our PCB board have eMMC (which is BGA package) and .4mm pitch MCU.

Now we are planning to move it in house if possible. I  started researching reflow ovens and came across KAYO RF630 and have read few positive comments about it. 

When i was talking to Kayo representative she said for BGAs its better to have RF835 model which have 8 heating zones up and down and tunnel length is 3200mm in comparison to RF630 which have 6 zones up and down and 2200mm length.

Based on my current understanding heating tunnel length probably determines number of boards per hour, i mean longer the length more boards per hour which mean higher productivity. Really I do not care for speed.
So my question is anybody using RF630 can confirm if are are able to do BGAs and .4mm pitch chips successfully. May be Kayo representative was saying just from the sales perspective to push for upper version. And cost is also not very different i mean 6K for 630 and 8K for 835 (with PC and rail guide options).

Please if some expert can suggest, can tunnel length affect the quality of BGA soldering and or .4mm  pitch chips?

I am sorry English is not my native language so i hope i can explain my confusion and question clearly.

Thanks,Rishi

[SMTech]

The more zones you have, the easier it is to adjust the profile of your board so it get somewhere close to hitting all the various targets different parts will have. Chunky parts will heat slower than small ones for instance. With more zones you can really focus on having a TAL (time above liquidous) that is as optimal as possible, the fewer zones you have the more of the zones in your oven you might need to set to higher temps to get everything/everywhere on your board into the process window, that in turn means you can easily push the limits of your TAL time or find it more difficult to solder more sensitive parts* as you can get a balance between what they want and what your larger parts need. Increasing tunnel length does indeed also improve throughput and almost always means you get more zones at the same time.

That said I wouldn't have said an eMMC module itself was really much of a concern in of itself, it really depends on what else is on the board/panel. 3.2meteres process length is a good size and is far preferable over 2.2.

I can't speak for the reliability of a Kayo oven, but this was not a road I cared to tread when we bought one, very few of the cheap Chinese brands have a good reputation outside China, but they do have a reputation for failing fans and heaters. I have a 7 zone Heller, it costs 4-5 times as much, but it also handles bigger boards, has lifetime warranty on the heaters/blowers, pin-edge and mesh conveyor, battery backup and pretty decent software for the built-in profiling (KIC). It was was also competitively priced against its mainstream competition (Ersa/BTU/ITW) and only a little more than the more trusted Chinese brands like Folungwin or SunEast. However if thats your budget and you get some spares in at the same time as the oven or are prepared to have to wait for them if an issue crops up.. can't hurt, much, to try.

*e.g some LEDS or surface mount transformers

[Styno]

The more zones you have, the easier it is to adjust the profile of your board so it get somewhere close to hitting all the various targets different parts will have.

Some ovens have two or more cooling zones. What’s the benefit of that?

[SMTech]

The more zones you have, the easier it is to adjust the profile of your board so it get somewhere close to hitting all the various targets different parts will have.

Some ovens have two or more cooling zones. What’s the benefit of that?

It's all about control, very fast cooling can cause thermal shock, too slow and you get weaker joints. That said lots and lots of ovens heave no cooling zones at all - its basically just the exit and for many applications the cooling rate is within spec. Controlled cooling is an option on our Heller for instance but its not fitted and so far not required.

[asmi]

I would be much more worried about placement accuracy for 0.4 mm pitch than oven.

[SMTech]

I would be much more worried about placement accuracy for 0.4 mm pitch than oven.

Well printing first and placement second, BGA, like QFN can be quite forgiving of poor placement, neither are all that forgiving of poorly stored/mixed/old paste or inconsistent printing. If that technology was on every board I made, categorically the board would be printed with an automatic printer with solder paste inspection. If you're talking to Kayo anyway, they do at least claim the A4/6/8 machines can handle that pitch and as the OP is talking about a single product that removes a good chunk of the downsides of the software/setup side of that class of machine. There are a couple of Kayo users/fans on here who I'm sure have run fine pitch ICs thru them.

[rishibhanot]

Regarding placement  Kayo sales representative was pushing for A6 instead of A4(suggesting placement accuracy of A6 will be better for .4mm pitch).
But again based on my limited knowledge acquired over this forum seems likes A4 and A6 uses identical hardware and software except number of heads.
Although they have another 6 head model called S600 , i have no idea whats different in this model. Specifications seems pretty much same.
Regarding printing i was thinking KAYO 5088 semi automatic model.

If somebody is using 5088 and or A6/S600 please shed some light based your practical experiences regarding .4mm pitch components.
Thanks for all your time.

[Mangozac]

I'm not sure what the A6 is. Their 6 head model is the 1706? I have a 1706 and it works well but the S600 is worth the premium. It is their next generation of machine, so is more advanced in all aspects, especially the software, which has a lot of improved features. If I were purchasing now I would pay the extra for the S600. The S600 has an individual Z-axis control for each head, so in theory it can do simultaneous part pickup if your design and program is optimised for it. All of their other machines share one stepper motor between two heads with a cam arm system, so Z-axis control is a bit arbitrary.

The 1706 with their latest software will place 0.4mm pitch parts OK but you have to keep an eye on it. The accuracy for super fine pitch parts like that isn't perfect so we don't get 100% yield. The S600 uses the same nozzle design and vision subsystems though so it's probably not a lot different.

[SMTech]

I'm not sure what the A6 is. Their 6 head model is the 1706? I have a 1706 and it works well but the S600 is worth the premium. It is their next generation of machine, so is more advanced in all aspects, especially the software, which has a lot of improved features. If I were purchasing now I would pay the extra for the S600. The S600 has an individual Z-axis control for each head, so in theory it can do simultaneous part pickup if your design and program is optimised for it. All of their other machines share one stepper motor between two heads with a cam arm system, so Z-axis control is a bit arbitrary.

The 1706 with their latest software will place 0.4mm pitch parts OK but you have to keep an eye on it. The accuracy for super fine pitch parts like that isn't perfect so we don't get 100% yield. The S600 uses the same nozzle design and vision subsystems though so it's probably not a lot different.

The EU site ( which I think is technically their distributor rather than Kayo themselves) lists an A6 between A4 and A8 as well as the S600, could be a regional variant to do with CE marks or outdated information or just another name for the 1706? My experience with Essemtec that technically easily handles 0402 is that to get truly good results, the board needs to be clamped & supported very securely and be nice and flat so the place height is exactly where it should be; as well as having a good print in the first place.  From that I would suggest that any machine with a slightly variable z-axis placement is going to put itself at a disadvantage from the start. I'm guessing the reason Kayo gets away with it for most other components is the spring loaded Juki nozzles they use. The shared Z-motor is interesting, I would certainly avoid it, on bigger machines its quite common to share a theta motor but that's much less restrictive.

[Mangozac]

I'm guessing the reason Kayo gets away with it for most other components is the spring loaded Juki nozzles they use.

Yes, the spring loaded Juki style nozzles definitely let you get away with a lot of imprecision on the Z-axis and as you say also help with countering any warp in the clamped PCB. I feel like regardless of the design of the rest of the machine the spring loaded nozzles are the best option, as they will account for the variability that can come from so many areas that would otherwise have to be accounted for in the design (component height tolerance, how the tape sits in the feeder, tape type, PCB flatness, etc.).

Of course, a good print is the cornerstone of good SMT assembly. Depending on the OP's anticipated volume I would strongly recommend an automatic printer. I know plenty of small shops are using the semi-automatic printers but for fine pitch boards they're not ideal. Automatic cleaning every x panels is the biggest advantage.