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MicroZED

Started by John Larkin October 19, 2013
krw@attt.bizz wrote:
> On Mon, 21 Oct 2013 12:23:13 -0700, Joerg <invalid@invalid.invalid> > wrote: > >> Jon Elson wrote: >>> John Larkin wrote: >>> >>> >>>> We prefer BGAs to leaded parts. >>> OK, well, someday, I'm sure, I will be led kicking and screaming down >>> that path. The lack of ability to examine the solder balls worries me. >> >> That's by far not the only thing that concerns me. >> >> http://www.cartoonstock.com/lowres/jfa2492l.jpg > > In all the places I've worked, we had the least trouble with BGAs. At > the PPoE the big problems were QFNs that didn't wet on the sides. BGAs > never had a problem, until they have to be replaced. ...
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ And that's exactly the problem. They don't fail initially. But they can later, on boards that are subject to lots of mechanical or thermal stress. The thermal stress is often delivered by the BGA part itself. There is a whole little industry that sprung up when BGAs were introduced. People learned re-balling and other things and then repaired game consoles, expensive laptops and such.
> ... That never goes > well locally. It's something that one has to do constantly to get > right. We send it all out at the CPoE.
Smart choice. I am also a believer in sending stuff to the pros unless you have real pros in-house. Trying to kludge it with BGAs just isn't worth it. But I don't use BGA, I prefer parts with leads that can take some stress. Leadless is ok if the part is very small, like the little DFN. -- Regards, Joerg http://www.analogconsultants.com/
On Sun, 20 Oct 2013 20:14:12 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 10/19/2013 7:11 PM, John Larkin wrote: >> On Sat, 19 Oct 2013 18:15:35 -0400, "Tom Del Rosso" >> <td_03@verizon.net.invalid> wrote: >> >>> >>> Joerg wrote: >>>> >>>> Now I really don't want to belittle community-based projects, they are >>>> excellent tools to get youngsters into tinkering again and our society >>>> really needs that. But I never use one of those products in designs >>>> that have to run for years or decades. There usually isn't much of a >>>> long term supply chain guarantee. >>> >>> If it's open-source can't you just make your own if they stop selling them? >> >> All the schematics and PCB layouts are published, open-source. Ditto >> lots of code. We could make our own if we had to... if the parts were >> still available. >> >> >Of course Avnet is showing zero stock...
They say we can have a couple in here this week. -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
John Larkin <jlarkin@highlandtechnology.com> writes:

> On Mon, 21 Oct 2013 19:11:53 -0400, krw@attt.bizz wrote: > >>On Mon, 21 Oct 2013 12:23:13 -0700, Joerg <invalid@invalid.invalid> >>wrote: >> >>>Jon Elson wrote: >>>> John Larkin wrote: >>>> >>>> >>>>> We prefer BGAs to leaded parts. >>>> OK, well, someday, I'm sure, I will be led kicking and screaming down >>>> that path. The lack of ability to examine the solder balls worries me. >>> >>> >>>That's by far not the only thing that concerns me. >>> >>>http://www.cartoonstock.com/lowres/jfa2492l.jpg >> >>In all the places I've worked, we had the least trouble with BGAs. At >>the PPoE the big problems were QFNs that didn't wet on the sides. BGAs >>never had a problem, until they have to be replaced. That never goes >>well locally. It's something that one has to do constantly to get >>right. We send it all out at the CPoE. > > We rework BGAs in-house. We had one bunch of products that kept > getting expanded functionally so we had to pull the 780-ball FPGAs and > put in compatible ones with twice the CLBs. We did about 20 boards, no > problems. > > BGAs are great. Much more reliable than fine-pitch leaded parts.
Does anyone know if it is possible to get away without solder paste, for prototyping purposes? Or do something like tin all the pads first, place, apply hot air? -- John Devereux
John Larkin wrote:

> We have an upcoming project that needs a uP, FPGA, Ethernet, DRAM, all > that stuff. It's tempting to buy a little board that has all that done > and working, running Linux out of the box.
Very nice, but not at all that micro: 10cmx5cm... :-/ Best regards, Piotr
On 22/10/2013 3:40 PM, John Devereux wrote:
> John Larkin <jlarkin@highlandtechnology.com> writes: > >> On Mon, 21 Oct 2013 19:11:53 -0400, krw@attt.bizz wrote: >> >>> On Mon, 21 Oct 2013 12:23:13 -0700, Joerg <invalid@invalid.invalid> >>> wrote: >>> >>>> Jon Elson wrote: >>>>> John Larkin wrote: >>>>> >>>>> >>>>>> We prefer BGAs to leaded parts. >>>>> OK, well, someday, I'm sure, I will be led kicking and screaming down >>>>> that path. The lack of ability to examine the solder balls worries me. >>>> >>>> >>>> That's by far not the only thing that concerns me. >>>> >>>> http://www.cartoonstock.com/lowres/jfa2492l.jpg >>> >>> In all the places I've worked, we had the least trouble with BGAs. At >>> the PPoE the big problems were QFNs that didn't wet on the sides. BGAs >>> never had a problem, until they have to be replaced. That never goes >>> well locally. It's something that one has to do constantly to get >>> right. We send it all out at the CPoE. >> >> We rework BGAs in-house. We had one bunch of products that kept >> getting expanded functionally so we had to pull the 780-ball FPGAs and >> put in compatible ones with twice the CLBs. We did about 20 boards, no >> problems. >> >> BGAs are great. Much more reliable than fine-pitch leaded parts. > > Does anyone know if it is possible to get away without solder paste, for > prototyping purposes? Or do something like tin all the pads first, > place, apply hot air? > >
I've never had anything to do with BGA's but I thought you could re-flow if you had a suspect joint but replacement of the package after removal required re-balling. https://www.google.com.au/#q=reball+bga
Glenn B <not_glenn@nowhere.com> writes:

> On 22/10/2013 3:40 PM, John Devereux wrote: >> John Larkin <jlarkin@highlandtechnology.com> writes: >> >>> On Mon, 21 Oct 2013 19:11:53 -0400, krw@attt.bizz wrote: >>> >>>> On Mon, 21 Oct 2013 12:23:13 -0700, Joerg <invalid@invalid.invalid> >>>> wrote: >>>> >>>>> Jon Elson wrote: >>>>>> John Larkin wrote: >>>>>> >>>>>> >>>>>>> We prefer BGAs to leaded parts. >>>>>> OK, well, someday, I'm sure, I will be led kicking and screaming down >>>>>> that path. The lack of ability to examine the solder balls worries me. >>>>> >>>>> >>>>> That's by far not the only thing that concerns me. >>>>> >>>>> http://www.cartoonstock.com/lowres/jfa2492l.jpg >>>> >>>> In all the places I've worked, we had the least trouble with BGAs. At >>>> the PPoE the big problems were QFNs that didn't wet on the sides. BGAs >>>> never had a problem, until they have to be replaced. That never goes >>>> well locally. It's something that one has to do constantly to get >>>> right. We send it all out at the CPoE. >>> >>> We rework BGAs in-house. We had one bunch of products that kept >>> getting expanded functionally so we had to pull the 780-ball FPGAs and >>> put in compatible ones with twice the CLBs. We did about 20 boards, no >>> problems. >>> >>> BGAs are great. Much more reliable than fine-pitch leaded parts. >> >> Does anyone know if it is possible to get away without solder paste, for >> prototyping purposes? Or do something like tin all the pads first, >> place, apply hot air? >> >> > > > I've never had anything to do with BGA's but I thought you could > re-flow if you had a suspect joint but replacement of the package > after removal required re-balling. > > https://www.google.com.au/#q=reball+bga
Thanks, I am talking about the initial soldering operation on a bare board. AFAICS I could just plonk the BGA down on its pads, without solder paste, with some flux. Heat everything up and the balls should melt and the package self-center. The point would be to avoid the initial stencil fee and full-up setup charges - and delays - when you just want to make a prototype unit. -- John Devereux
Den tirsdag den 22. oktober 2013 15.21.23 UTC+2 skrev John Devereux:
> Glenn B <not_glenn@nowhere.com> writes: > > > > > On 22/10/2013 3:40 PM, John Devereux wrote: > > >> John Larkin <jlarkin@highlandtechnology.com> writes: > > >> > > >>> On Mon, 21 Oct 2013 19:11:53 -0400, krw@attt.bizz wrote: > > >>> > > >>>> On Mon, 21 Oct 2013 12:23:13 -0700, Joerg <invalid@invalid.invalid> > > >>>> wrote: > > >>>> > > >>>>> Jon Elson wrote: > > >>>>>> John Larkin wrote: > > >>>>>> > > >>>>>> > > >>>>>>> We prefer BGAs to leaded parts. > > >>>>>> OK, well, someday, I'm sure, I will be led kicking and screaming down > > >>>>>> that path. The lack of ability to examine the solder balls worries me. > > >>>>> > > >>>>> > > >>>>> That's by far not the only thing that concerns me. > > >>>>> > > >>>>> http://www.cartoonstock.com/lowres/jfa2492l.jpg > > >>>> > > >>>> In all the places I've worked, we had the least trouble with BGAs. At > > >>>> the PPoE the big problems were QFNs that didn't wet on the sides. BGAs > > >>>> never had a problem, until they have to be replaced. That never goes > > >>>> well locally. It's something that one has to do constantly to get > > >>>> right. We send it all out at the CPoE. > > >>> > > >>> We rework BGAs in-house. We had one bunch of products that kept > > >>> getting expanded functionally so we had to pull the 780-ball FPGAs and > > >>> put in compatible ones with twice the CLBs. We did about 20 boards, no > > >>> problems. > > >>> > > >>> BGAs are great. Much more reliable than fine-pitch leaded parts. > > >> > > >> Does anyone know if it is possible to get away without solder paste, for > > >> prototyping purposes? Or do something like tin all the pads first, > > >> place, apply hot air? > > >> > > >> > > > > > > > > > I've never had anything to do with BGA's but I thought you could > > > re-flow if you had a suspect joint but replacement of the package > > > after removal required re-balling. > > > > > > https://www.google.com.au/#q=reball+bga > > > > Thanks, I am talking about the initial soldering operation on a bare > > board. AFAICS I could just plonk the BGA down on its pads, without > > solder paste, with some flux. Heat everything up and the balls should > > melt and the package self-center. > > > > The point would be to avoid the initial stencil fee and full-up setup > > charges - and delays - when you just want to make a prototype unit. >
you can get stencils that have the usual BGA sizes and many of the cheap chinese PCB prototype places now offer a stencil for something like 20$ -Lasse
John Larkin wrote:
> On Mon, 21 Oct 2013 14:25:56 -0500, Jon Elson <jmelson@wustl.edu> > wrote: > >> John Larkin wrote: >> >> >>> We prefer BGAs to leaded parts. >> OK, well, someday, I'm sure, I will be led kicking and screaming down >> that path. The lack of ability to examine the solder balls worries me. > > The great thing about inspecting all those BGA balls is that you can't > inspect them. >
That's why inspection is usually not done :-(
> Actually, there are some optical gadgets that let you peek under the > chip, from the side, and see the first 3 or 4 rows of balls fairly > well. And you can see through the entire array, for debris and such. > We just bought a good one for around $30K. >
Can it reliably detect flux residue somewhere in the middle? It's hard to clean under a large BGA and then a few years down the road something might quit working.
>> I do all my own assembly using an aging P&P machine and a modified >> toaster oven. > > People do BGAs at home, too. > > These are cool: > > http://www.stencilsunlimited.com/bga_rework_stencils_stencilquik.php > > We use them for rework, but they would be good for hand assembly, too. >
How do you get the flux back out? Do you use Kester 951 flux?
> I have overcome my fears of 1206s, 0805s, 0603s, SC70s and US8 > packages (almost), TSSOPs, and BGAs. SC79s and 0402s still terrify me. >
Those are boulders. Some time around March next year I'll have to deal with 01005. Not looking forward to that but as John Wayne said, man's gotta do what man's gotta do. As I get older and SMT becomes smaller I have found that even the Donegan 5x visor is sometimes not enough. -- Regards, Joerg http://www.analogconsultants.com/
On 10/22/2013 10:38 AM, Joerg wrote:
> John Larkin wrote: >> On Mon, 21 Oct 2013 14:25:56 -0500, Jon Elson <jmelson@wustl.edu> >> wrote: >> >>> John Larkin wrote: >>> >>> >>>> We prefer BGAs to leaded parts. >>> OK, well, someday, I'm sure, I will be led kicking and screaming down >>> that path. The lack of ability to examine the solder balls worries me. >> >> The great thing about inspecting all those BGA balls is that you can't >> inspect them. >> > > That's why inspection is usually not done :-( > > >> Actually, there are some optical gadgets that let you peek under the >> chip, from the side, and see the first 3 or 4 rows of balls fairly >> well. And you can see through the entire array, for debris and such. >> We just bought a good one for around $30K. >> > > Can it reliably detect flux residue somewhere in the middle? It's hard > to clean under a large BGA and then a few years down the road something > might quit working. > > >>> I do all my own assembly using an aging P&P machine and a modified >>> toaster oven. >> >> People do BGAs at home, too. >> >> These are cool: >> >> http://www.stencilsunlimited.com/bga_rework_stencils_stencilquik.php >> >> We use them for rework, but they would be good for hand assembly, too. >> > > How do you get the flux back out? Do you use Kester 951 flux? > > >> I have overcome my fears of 1206s, 0805s, 0603s, SC70s and US8 >> packages (almost), TSSOPs, and BGAs. SC79s and 0402s still terrify me. >> > > Those are boulders. Some time around March next year I'll have to deal > with 01005. Not looking forward to that but as John Wayne said, man's > gotta do what man's gotta do. > > As I get older and SMT becomes smaller I have found that even the > Donegan 5x visor is sometimes not enough. >
Big BGAs need underfill to reduce the stress on the balls. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Lasse Langwadt Christensen <langwadt@fonz.dk> writes:

> Den tirsdag den 22. oktober 2013 15.21.23 UTC+2 skrev John Devereux:
[...]
>> >> >> Thanks, I am talking about the initial soldering operation on a bare >> >> board. AFAICS I could just plonk the BGA down on its pads, without >> >> solder paste, with some flux. Heat everything up and the balls should >> >> melt and the package self-center. >> >> >> >> The point would be to avoid the initial stencil fee and full-up setup >> >> charges - and delays - when you just want to make a prototype unit. >> > > you can get stencils that have the usual BGA sizes > > and many of the cheap chinese PCB prototype places now offer a stencil > for something like 20$
Hi Lasse, Yes I saw those that JL posted. Still an extra cost, and need to make sure I have in stock, and need to use solder paste which always goes off by the time I need it etc. Although certainly it is an option especially if I get my assembly house to do it (using their paste). But, is paste really essential for the process to work? Aren't the solder balls already made out of - well - solder? -- John Devereux