1. This forum section is a read-only archive which contains old newsgroup posts. If you wish to post a query, please do so in one of our main forum sections (here). This way you will get a faster, better response from the members on Motherboard Point.

BGA's are killing my project

Discussion in 'Embedded' started by johnspeth@yahoo.com, Oct 13, 2006.

  1. Guest

    Hi everybody-

    My project uses several BGA parts. We're in the second board rev stage
    (rev 2). Our board manufacturer doesn't seem to be able to 100%
    reliably solder those parts down. It makes SW debugging troublesome
    because one never knows if the SW or the part is misbehaving. We've
    had 15 boards built and I estimate 20% have BGA problems.

    I'd like to hear other's experiences with and solutions to BGA
    soldering reliability problems. I have a few questions to kick off the
    discussion:

    Is it a manufacturer process problem that can be totally fixed with
    some soldering process improvement? (Corollar: Is my board builder not
    up to the task?)

    Is this a natural and expected problem that I just have to live with
    (result = reduced board yield)?

    How much does the lead-free directive contribute to the problem? (My
    rev 2 boards we're built using no-lead solder but rev 1 boards were
    built using leaded solder and had the same BGA problems.)

    Does X-ray inspection *really* identify badly soldered parts 100% of
    the time?

    What is a typical delivered board BGA solder failure rate that you guys
    will accept?

    Thanks for sharing your opinions and experiences.

    JJS
     
    , Oct 13, 2006
    #1
    1. Advertising

  2. linnix Guest

    wrote:
    > Hi everybody-
    >
    > My project uses several BGA parts. We're in the second board rev stage
    > (rev 2). Our board manufacturer doesn't seem to be able to 100%
    > reliably solder those parts down. It makes SW debugging troublesome
    > because one never knows if the SW or the part is misbehaving. We've
    > had 15 boards built and I estimate 20% have BGA problems.
    >
    > I'd like to hear other's experiences with and solutions to BGA
    > soldering reliability problems. I have a few questions to kick off the
    > discussion:
    >
    > Is it a manufacturer process problem that can be totally fixed with
    > some soldering process improvement? (Corollar: Is my board builder not
    > up to the task?)


    It's a testing and QC/QA issue.

    >
    > Is this a natural and expected problem that I just have to live with
    > (result = reduced board yield)?


    No. you have to help the board assembler to solve the problem.

    >
    > How much does the lead-free directive contribute to the problem? (My
    > rev 2 boards we're built using no-lead solder but rev 1 boards were
    > built using leaded solder and had the same BGA problems.)


    Yes, it does. Lead-free requires higher temperature and more expensive
    solder (silver).

    >
    > Does X-ray inspection *really* identify badly soldered parts 100% of
    > the time?


    Yes, it should help, together with boundary scans. Are they Jtag
    scanable?

    >
    > What is a typical delivered board BGA solder failure rate that you guys
    > will accept?


    Zero, they should go back to be oven.

    >
    > Thanks for sharing your opinions and experiences.
    >
    > JJS
     
    linnix, Oct 13, 2006
    #2
    1. Advertising

  3. Tim Wescott Guest

    wrote:

    > Hi everybody-
    >
    > My project uses several BGA parts. We're in the second board rev stage
    > (rev 2). Our board manufacturer doesn't seem to be able to 100%
    > reliably solder those parts down. It makes SW debugging troublesome
    > because one never knows if the SW or the part is misbehaving. We've
    > had 15 boards built and I estimate 20% have BGA problems.
    >
    > I'd like to hear other's experiences with and solutions to BGA
    > soldering reliability problems. I have a few questions to kick off the
    > discussion:
    >
    > Is it a manufacturer process problem that can be totally fixed with
    > some soldering process improvement? (Corollar: Is my board builder not
    > up to the task?)


    Possibly. It may be a board layout problem, as well. Assuming good
    layout then yes, the soldering process can be improved.

    I'd make sure to get together with the chip vendor to make sure that you
    (or your layout people) understand the layout requirements and are
    adhering to them, then I'd start pounding on the board house.
    >
    > Is this a natural and expected problem that I just have to live with
    > (result = reduced board yield)?


    No.
    >
    > How much does the lead-free directive contribute to the problem? (My
    > rev 2 boards we're built using no-lead solder but rev 1 boards were
    > built using leaded solder and had the same BGA problems.)


    I don't know, but from what I understand about lead-free processes your
    biggest two hurdles will be getting it tuned right to begin with, and
    tin whiskers down the road. If your assembly house can't even do it
    with leaded solder that's not the problem.
    >
    > Does X-ray inspection *really* identify badly soldered parts 100% of
    > the time?


    No. X-ray inspection just looks down through the joint -- if there's
    solder there that's not sticking it can be very difficult to tell from a
    good joint.

    It does make a difference, however, so it's not to be ignored.
    >
    > What is a typical delivered board BGA solder failure rate that you guys
    > will accept?


    I stand around with my hands in my pockets laughing at folks who
    actually have to worry about this stuff, so I don't know. But I _do_
    know that we've used them in an environment where a 2% or 5% reject rate
    for the whole board would be considered "way bad", so you can bet we're
    seeing much less than that for BGA parts.

    If I remember I'll check and let you know this evening.

    I think you need to find an assembly house who has some mileage with BGA
    parts, or you need to see your current assembly house start some serious
    discussions with your chip vendor. BGA parts have been around for
    nearly 10 years now, and they're becoming ubiquitous. Any assembly
    house worth its salt really should know how to do it.

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com

    Posting from Google? See http://cfaj.freeshell.org/google/

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at http://www.wescottdesign.com/actfes/actfes.html
     
    Tim Wescott, Oct 13, 2006
    #3
  4. larwe Guest

    Tim Wescott wrote:

    > > What is a typical delivered board BGA solder failure rate that you guys
    > > will accept?

    >
    > I stand around with my hands in my pockets laughing at folks who
    > actually have to worry about this stuff, so I don't know. But I _do_
    > know that we've used them in an environment where a 2% or 5% reject rate
    > for the whole board would be considered "way bad", so you can bet we're
    > seeing much less than that for BGA parts.


    Well, that's for production, right?

    Most of the assembly houses that do tiny runs for proto purposes
    request a 10% overage on special parts (including BGAs) and yield is
    often not guaranteed. Protos are often hand-assembled.
     
    larwe, Oct 13, 2006
    #4
  5. Arlet Guest

    wrote:

    > My project uses several BGA parts. We're in the second board rev stage
    > (rev 2). Our board manufacturer doesn't seem to be able to 100%
    > reliably solder those parts down. It makes SW debugging troublesome
    > because one never knows if the SW or the part is misbehaving. We've
    > had 15 boards built and I estimate 20% have BGA problems.


    BGA solder problems can also be related to the PCB design. Make sure
    your pads have the recommended size and shape. Vias in the pad, or very
    near the pad can also cause problems by wicking the solder away from
    the pad and into the hole.
     
    Arlet, Oct 13, 2006
    #5
  6. PeteS Guest

    Arlet wrote:
    > wrote:
    >
    >
    >>My project uses several BGA parts. We're in the second board rev stage
    >>(rev 2). Our board manufacturer doesn't seem to be able to 100%
    >>reliably solder those parts down. It makes SW debugging troublesome
    >>because one never knows if the SW or the part is misbehaving. We've
    >>had 15 boards built and I estimate 20% have BGA problems.

    >
    >
    > BGA solder problems can also be related to the PCB design. Make sure
    > your pads have the recommended size and shape. Vias in the pad, or very
    > near the pad can also cause problems by wicking the solder away from
    > the pad and into the hole.
    >

    A specific piece of board design that will _kill_ you in BGAs is the
    pad. You really _must_ use non Solder Mask Defined pads if you want high
    yield (and I define that as 100% - I don't accept failures due to failed
    soldering).

    I once worked at a company that had soldermask defined pads under a
    pretty large (768 balls) BGA, and the yield was horrendous. Went to
    non-SMD and the yields went way up.

    I would be very surprised, assuming the layout is properly done and the
    CM has edxperience with BGAs, to _ever_ see a BGA failure rate higher
    than that for TQFP for soldering issues. BGAs are _easier_ on the process.

    Cheers

    PeteS
     
    PeteS, Oct 13, 2006
    #6
  7. Jim Stewart Guest

    PeteS wrote:

    > Arlet wrote:
    >
    >> wrote:
    >>
    >>
    >>> My project uses several BGA parts. We're in the second board rev stage
    >>> (rev 2). Our board manufacturer doesn't seem to be able to 100%
    >>> reliably solder those parts down. It makes SW debugging troublesome
    >>> because one never knows if the SW or the part is misbehaving. We've
    >>> had 15 boards built and I estimate 20% have BGA problems.

    >>
    >>
    >>
    >> BGA solder problems can also be related to the PCB design. Make sure
    >> your pads have the recommended size and shape. Vias in the pad, or very
    >> near the pad can also cause problems by wicking the solder away from
    >> the pad and into the hole.
    >>

    > A specific piece of board design that will _kill_ you in BGAs is the
    > pad. You really _must_ use non Solder Mask Defined pads if you want high
    > yield (and I define that as 100% - I don't accept failures due to failed
    > soldering).
    >
    > I once worked at a company that had soldermask defined pads under a
    > pretty large (768 balls) BGA, and the yield was horrendous. Went to
    > non-SMD and the yields went way up.
    >
    > I would be very surprised, assuming the layout is properly done and the
    > CM has edxperience with BGAs, to _ever_ see a BGA failure rate higher
    > than that for TQFP for soldering issues. BGAs are _easier_ on the process.


    Could you explain the difference?
     
    Jim Stewart, Oct 13, 2006
    #7
  8. Guest

    Lead soldering of BGA's has been an almost zero defect process for our vendor. (< 0.1% error)

    Switching to no-lead has caused some yield issues early on, but thay
    seem to have straightend them selves out.

    It seems that the No-lead soldering has a lower margin for error.
    Board must be properly designed, properly plated, and clean.


    Paul




    On 13 Oct 2006 08:38:17 -0700, wrote:

    >Hi everybody-
    >
    >My project uses several BGA parts. We're in the second board rev stage
    >(rev 2). Our board manufacturer doesn't seem to be able to 100%
    >reliably solder those parts down. It makes SW debugging troublesome
    >because one never knows if the SW or the part is misbehaving. We've
    >had 15 boards built and I estimate 20% have BGA problems.
    >
    >I'd like to hear other's experiences with and solutions to BGA
    >soldering reliability problems. I have a few questions to kick off the
    >discussion:
    >
    >Is it a manufacturer process problem that can be totally fixed with
    >some soldering process improvement? (Corollar: Is my board builder not
    >up to the task?)
    >
    >Is this a natural and expected problem that I just have to live with
    >(result = reduced board yield)?
    >
    >How much does the lead-free directive contribute to the problem? (My
    >rev 2 boards we're built using no-lead solder but rev 1 boards were
    >built using leaded solder and had the same BGA problems.)
    >
    >Does X-ray inspection *really* identify badly soldered parts 100% of
    >the time?
    >
    >What is a typical delivered board BGA solder failure rate that you guys
    >will accept?
    >
    >Thanks for sharing your opinions and experiences.
    >
    >JJS
     
    , Oct 13, 2006
    #8
  9. Elan Magavi Guest

    The main problem we are having with BGAs are the houses that do not have the
    technique down yet to mount them correctly. It has been a hell of a problem.

    Phil


    <> wrote in message
    news:...
    > Hi everybody-
    >
    > My project uses several BGA parts. We're in the second board rev stage
    > (rev 2). Our board manufacturer doesn't seem to be able to 100%
    > reliably solder those parts down. It makes SW debugging troublesome
    > because one never knows if the SW or the part is misbehaving. We've
    > had 15 boards built and I estimate 20% have BGA problems.
    >
    > I'd like to hear other's experiences with and solutions to BGA
    > soldering reliability problems. I have a few questions to kick off the
    > discussion:
    >
    > Is it a manufacturer process problem that can be totally fixed with
    > some soldering process improvement? (Corollar: Is my board builder not
    > up to the task?)
    >
    > Is this a natural and expected problem that I just have to live with
    > (result = reduced board yield)?
    >
    > How much does the lead-free directive contribute to the problem? (My
    > rev 2 boards we're built using no-lead solder but rev 1 boards were
    > built using leaded solder and had the same BGA problems.)
    >
    > Does X-ray inspection *really* identify badly soldered parts 100% of
    > the time?
    >
    > What is a typical delivered board BGA solder failure rate that you guys
    > will accept?
    >
    > Thanks for sharing your opinions and experiences.
    >
    > JJS
    >
     
    Elan Magavi, Oct 13, 2006
    #9
  10. Elan Magavi Guest

    PS.. The fab houses are having a hell of a problem with the lead free
    requirements and BGA problems for us have included that issue.


    "Elan Magavi" <> wrote in message
    news:hkRXg.13781$...
    > The main problem we are having with BGAs are the houses that do not have
    > the technique down yet to mount them correctly. It has been a hell of a
    > problem.
    >
    > Phil
    >
    >
    > <> wrote in message
    > news:...
    >> Hi everybody-
    >>
    >> My project uses several BGA parts. We're in the second board rev stage
    >> (rev 2). Our board manufacturer doesn't seem to be able to 100%
    >> reliably solder those parts down. It makes SW debugging troublesome
    >> because one never knows if the SW or the part is misbehaving. We've
    >> had 15 boards built and I estimate 20% have BGA problems.
    >>
    >> I'd like to hear other's experiences with and solutions to BGA
    >> soldering reliability problems. I have a few questions to kick off the
    >> discussion:
    >>
    >> Is it a manufacturer process problem that can be totally fixed with
    >> some soldering process improvement? (Corollar: Is my board builder not
    >> up to the task?)
    >>
    >> Is this a natural and expected problem that I just have to live with
    >> (result = reduced board yield)?
    >>
    >> How much does the lead-free directive contribute to the problem? (My
    >> rev 2 boards we're built using no-lead solder but rev 1 boards were
    >> built using leaded solder and had the same BGA problems.)
    >>
    >> Does X-ray inspection *really* identify badly soldered parts 100% of
    >> the time?
    >>
    >> What is a typical delivered board BGA solder failure rate that you guys
    >> will accept?
    >>
    >> Thanks for sharing your opinions and experiences.
    >>
    >> JJS
    >>

    >
    >
     
    Elan Magavi, Oct 13, 2006
    #10
  11. DJ Delorie Guest

    "Arlet" <4all.nl> writes:
    > BGA solder problems can also be related to the PCB design. Make sure
    > your pads have the recommended size and shape. Vias in the pad, or
    > very near the pad can also cause problems by wicking the solder away
    > from the pad and into the hole.


    What about finish? I mean, HASL vs flash vs immersion vs whatever?

    Also, what about adding solder paste to the pads, or flux?

    Inquiring minds want to know...
     
    DJ Delorie, Oct 13, 2006
    #11
  12. Joerg Guest

    Hello John,

    >
    > My project uses several BGA parts. We're in the second board rev stage
    > (rev 2). Our board manufacturer doesn't seem to be able to 100%
    > reliably solder those parts down. It makes SW debugging troublesome
    > because one never knows if the SW or the part is misbehaving. We've
    > had 15 boards built and I estimate 20% have BGA problems.
    >
    > I'd like to hear other's experiences with and solutions to BGA
    > soldering reliability problems. I have a few questions to kick off the
    > discussion:
    >
    > Is it a manufacturer process problem that can be totally fixed with
    > some soldering process improvement? (Corollar: Is my board builder not
    > up to the task?)
    >
    > Is this a natural and expected problem that I just have to live with
    > (result = reduced board yield)?
    >
    > How much does the lead-free directive contribute to the problem? (My
    > rev 2 boards we're built using no-lead solder but rev 1 boards were
    > built using leaded solder and had the same BGA problems.)
    >
    > Does X-ray inspection *really* identify badly soldered parts 100% of
    > the time?
    >
    > What is a typical delivered board BGA solder failure rate that you guys
    > will accept?
    >
    > Thanks for sharing your opinions and experiences.
    >


    I don't use BGA if at all possible so I can't recommend an assembler. As
    others have said the first thing is to look whether your board layout
    and fab instructions are top notch and ideal for each BGA location.

    If they are then my suggestion would be to find an assembly house that
    has a good track record with BGA. Maybe post in sci.electronic.design,
    "Recommendations for BGA assemblers" or similar. There are a lot of
    folks who have to deal with BGA. You could also call the sales guys at
    the manufacturer of your BGA chip. They know good places and if not they
    can certainly find out via a few calls to their other clients. After all
    they have a vested interest in you sticking with their chip and not
    looking for alternatives.

    IME when there is a reliability problem with an assembler and they can't
    immediately point to QC test results and say "aha!" then chances are it
    won't get better fast enough.

    Oh, and make sure the engineers at the assembly house didn't take the
    liberty to "improve" your layout. I had that happen a month ago where
    all my prototypes failed. Every one of them. Turned out they had
    increased some clearances and inadvertantly split a power plane island
    into four floating chunks.

    --
    Regards, Joerg

    http://www.analogconsultants.com
     
    Joerg, Oct 13, 2006
    #12
  13. Joerg Guest

    Joerg wrote:

    >
    > Oh, and make sure the engineers at the assembly house didn't take the
    > liberty to "improve" your layout. I had that happen a month ago where
    > all my prototypes failed. Every one of them. Turned out they had
    > increased some clearances and inadvertantly split a power plane island
    > into four floating chunks.
    >


    I meant at board fab. That's where it happened, not at the assemblers.

    --
    Regards, Joerg

    http://www.analogconsultants.com
     
    Joerg, Oct 13, 2006
    #13
  14. PeteS Guest

    Jim Stewart wrote:
    > PeteS wrote:
    >
    >> Arlet wrote:
    >>
    >>> wrote:
    >>>
    >>>
    >>>> My project uses several BGA parts. We're in the second board rev stage
    >>>> (rev 2). Our board manufacturer doesn't seem to be able to 100%
    >>>> reliably solder those parts down. It makes SW debugging troublesome
    >>>> because one never knows if the SW or the part is misbehaving. We've
    >>>> had 15 boards built and I estimate 20% have BGA problems.
    >>>
    >>>
    >>>
    >>>
    >>> BGA solder problems can also be related to the PCB design. Make sure
    >>> your pads have the recommended size and shape. Vias in the pad, or very
    >>> near the pad can also cause problems by wicking the solder away from
    >>> the pad and into the hole.
    >>>

    >> A specific piece of board design that will _kill_ you in BGAs is the
    >> pad. You really _must_ use non Solder Mask Defined pads if you want
    >> high yield (and I define that as 100% - I don't accept failures due to
    >> failed soldering).
    >>
    >> I once worked at a company that had soldermask defined pads under a
    >> pretty large (768 balls) BGA, and the yield was horrendous. Went to
    >> non-SMD and the yields went way up.
    >>
    >> I would be very surprised, assuming the layout is properly done and
    >> the CM has edxperience with BGAs, to _ever_ see a BGA failure rate
    >> higher than that for TQFP for soldering issues. BGAs are _easier_ on
    >> the process.

    >
    >
    > Could you explain the difference?


    Not sure which difference, so I'll do both :)

    A solder mask defined pad is simply that; the pad opening is defined by
    solder mask, which covers some part of the pad. A non-SMD pad is defined
    by the pad itself, and no solder mask is in contact with it.

    On a solder mask defined pad, there is, by definition, a raised 'lip'
    through which the solder ball has to flow for soldering, and this can
    cause no connection at all to high impedance connections (which are
    really frustrating - the JTAG tests will all pass, but nothing works at
    speed).

    There are some really good app notes on this; I'll see if I have any. I
    seem to remember app notes from Xilinx, Altera, TI, Intel and Micron at
    the least.

    As to BGAs being easier on the process - on SnPb the solder ball wicking
    effect actually 'pulls' the BGA onto the pads. The placement accuracy
    for a BGA is 0.5 pad spacing because of this, which is less accurate
    than final soldered placement accuracy and very easy to achieve with
    automated pick'n'place.
    Whether this holds true in a non SnPb world has yet to be seen.

    For a TQFP, because there are pads on each side, the wicking effect
    doesn't work this way (the forces apparently cancel) so the placement
    accuracy has to be the same as the final soldered placement accuracy.
    For a highspeed part (to minimise impedance offsets) this may be as low
    as 0.1 pad spacing, which may itself be 0.5mm. That's a very tight
    tolerance, and very difficult to achieve.

    Empirically, I have also had many more problems with cold joints,
    soldersplash and solder shorts with TQFPs than with BGAs. I've
    personally designed many dozens of boards with both and I have had very
    few problems (except the non-SMD issue) with BGAs. Most of my solder
    problems are with TQFP and QFN (and that's a process issue although the
    process is harder to get right the first time for those).

    Cheers

    PeteS
     
    PeteS, Oct 14, 2006
    #14
  15. PeteS Guest

    PeteS wrote:
    > Jim Stewart wrote:
    >
    >> PeteS wrote:
    >>
    >>> Arlet wrote:
    >>>
    >>>> wrote:
    >>>>
    >>>>
    >>>>> My project uses several BGA parts. We're in the second board rev
    >>>>> stage
    >>>>> (rev 2). Our board manufacturer doesn't seem to be able to 100%
    >>>>> reliably solder those parts down. It makes SW debugging troublesome
    >>>>> because one never knows if the SW or the part is misbehaving. We've
    >>>>> had 15 boards built and I estimate 20% have BGA problems.
    >>>>
    >>>>
    >>>>
    >>>>
    >>>>
    >>>> BGA solder problems can also be related to the PCB design. Make sure
    >>>> your pads have the recommended size and shape. Vias in the pad, or very
    >>>> near the pad can also cause problems by wicking the solder away from
    >>>> the pad and into the hole.
    >>>>
    >>> A specific piece of board design that will _kill_ you in BGAs is the
    >>> pad. You really _must_ use non Solder Mask Defined pads if you want
    >>> high yield (and I define that as 100% - I don't accept failures due
    >>> to failed soldering).
    >>>
    >>> I once worked at a company that had soldermask defined pads under a
    >>> pretty large (768 balls) BGA, and the yield was horrendous. Went to
    >>> non-SMD and the yields went way up.
    >>>
    >>> I would be very surprised, assuming the layout is properly done and
    >>> the CM has edxperience with BGAs, to _ever_ see a BGA failure rate
    >>> higher than that for TQFP for soldering issues. BGAs are _easier_ on
    >>> the process.

    >>
    >>
    >>
    >> Could you explain the difference?

    >
    >
    > Not sure which difference, so I'll do both :)
    >
    > A solder mask defined pad is simply that; the pad opening is defined by
    > solder mask, which covers some part of the pad. A non-SMD pad is defined
    > by the pad itself, and no solder mask is in contact with it.
    >
    > On a solder mask defined pad, there is, by definition, a raised 'lip'
    > through which the solder ball has to flow for soldering, and this can
    > cause no connection at all to high impedance connections (which are
    > really frustrating - the JTAG tests will all pass, but nothing works at
    > speed).
    >
    > There are some really good app notes on this; I'll see if I have any. I
    > seem to remember app notes from Xilinx, Altera, TI, Intel and Micron at
    > the least.
    >
    > As to BGAs being easier on the process - on SnPb the solder ball wicking
    > effect actually 'pulls' the BGA onto the pads. The placement accuracy
    > for a BGA is 0.5 pad spacing because of this, which is less accurate
    > than final soldered placement accuracy and very easy to achieve with
    > automated pick'n'place.
    > Whether this holds true in a non SnPb world has yet to be seen.
    >
    > For a TQFP, because there are pads on each side, the wicking effect
    > doesn't work this way (the forces apparently cancel) so the placement
    > accuracy has to be the same as the final soldered placement accuracy.
    > For a highspeed part (to minimise impedance offsets) this may be as low
    > as 0.1 pad spacing, which may itself be 0.5mm. That's a very tight
    > tolerance, and very difficult to achieve.
    >
    > Empirically, I have also had many more problems with cold joints,
    > soldersplash and solder shorts with TQFPs than with BGAs. I've
    > personally designed many dozens of boards with both and I have had very
    > few problems (except the non-SMD issue) with BGAs. Most of my solder
    > problems are with TQFP and QFN (and that's a process issue although the
    > process is harder to get right the first time for those).
    >
    > Cheers
    >
    > PeteS


    FWIW, the board finish makes a lot of difference. My preferred finish
    for BGA boards is gold over nickel, and since RoHS that's the finish I
    use for all boards.

    HASL is _not_ suitable for large BGAs (or any BGAs, imo), especially
    full grid types. Many BGAs have outer rows, and a central area where
    power and ground connect, and a nice clear zone between them. Full grid
    devices have no such clear zone (See the FT256 package from Xilinx for
    an example).

    As an interesting note on solder mask defined pads, I worked with one
    device from IR (IPwr200x, ISTR) where a _solder mask defined pad_ was
    specified as a requirement. Although that was unusual, I did it that way
    and never had a failure. The ball spacing on that part was quite wide,
    however.

    Cheers

    PeteS
     
    PeteS, Oct 14, 2006
    #15
  16. Oliver Betz Guest

    PeteS wrote:

    [...]

    >As to BGAs being easier on the process - on SnPb the solder ball wicking
    >effect actually 'pulls' the BGA onto the pads. The placement accuracy


    [...]

    >For a TQFP, because there are pads on each side, the wicking effect
    >doesn't work this way (the forces apparently cancel) so the placement
    >accuracy has to be the same as the final soldered placement accuracy.


    which shouldn't be a problem, IMO.

    And I can hand solder TQFP even at 0,5mm pitch without any problem.
    And desolder it with little effort and without damaging the board.

    Try this with BGAs.

    Oliver
    --
    Oliver Betz, Muenchen (oliverbetz.de)
     
    Oliver Betz, Oct 14, 2006
    #16
  17. PeteS Guest

    Oliver Betz wrote:
    > PeteS wrote:
    >
    > [...]
    >
    >
    >>As to BGAs being easier on the process - on SnPb the solder ball wicking
    >>effect actually 'pulls' the BGA onto the pads. The placement accuracy

    >
    >
    > [...]
    >
    >
    >>For a TQFP, because there are pads on each side, the wicking effect
    >>doesn't work this way (the forces apparently cancel) so the placement
    >>accuracy has to be the same as the final soldered placement accuracy.

    >
    >
    > which shouldn't be a problem, IMO.
    >
    > And I can hand solder TQFP even at 0,5mm pitch without any problem.
    > And desolder it with little effort and without damaging the board.
    >
    > Try this with BGAs.
    >
    > Oliver


    In an automated process, things are completely different

    Have you ever been in those situations?

    Cheers

    PeteS
     
    PeteS, Oct 14, 2006
    #17
  18. Oliver Betz Guest

    PeteS <> wrote:

    [...]

    >>>As to BGAs being easier on the process - on SnPb the solder ball wicking
    >>>effect actually 'pulls' the BGA onto the pads. The placement accuracy

    >>
    >> [...]
    >>
    >>>For a TQFP, because there are pads on each side, the wicking effect
    >>>doesn't work this way (the forces apparently cancel) so the placement
    >>>accuracy has to be the same as the final soldered placement accuracy.

    >>
    >> which shouldn't be a problem, IMO.


    >> And I can hand solder TQFP even at 0,5mm pitch without any problem.
    >> And desolder it with little effort and without damaging the board.
    >>
    >> Try this with BGAs.

    >
    >In an automated process, things are completely different
    >
    >Have you ever been in those situations?


    certainly I referred to automated placement when I wrote "which
    shouldn't be a problem, IMO" - we use an several years "old" Siemens
    so I can't imagine that "current" equipment is worse.

    But I love the possibility to hand solder prototypes or to replace a
    microcontroller when I zapped it during ESD tests. All I need is a
    matching funnel (wording?) and hot air to remove the IC and a
    soldering iron with a hoof shaped tip and a magnifier to solder the
    new one. Well, some solder wick could be necessary.

    Oliver
    --
    Oliver Betz, Muenchen (oliverbetz.de)
     
    Oliver Betz, Oct 15, 2006
    #18
  19. Joerg Guest

    Hello Oliver,


    >>>>As to BGAs being easier on the process - on SnPb the solder ball wicking
    >>>>effect actually 'pulls' the BGA onto the pads. The placement accuracy
    >>>
    >>>[...]
    >>>
    >>>
    >>>>For a TQFP, because there are pads on each side, the wicking effect
    >>>>doesn't work this way (the forces apparently cancel) so the placement
    >>>>accuracy has to be the same as the final soldered placement accuracy.
    >>>
    >>>which shouldn't be a problem, IMO.

    >
    >
    >>>And I can hand solder TQFP even at 0,5mm pitch without any problem.
    >>>And desolder it with little effort and without damaging the board.
    >>>
    >>>Try this with BGAs.

    >>
    >>In an automated process, things are completely different
    >>
    >>Have you ever been in those situations?

    >
    >
    > certainly I referred to automated placement when I wrote "which
    > shouldn't be a problem, IMO" - we use an several years "old" Siemens
    > so I can't imagine that "current" equipment is worse.
    >
    > But I love the possibility to hand solder prototypes or to replace a
    > microcontroller when I zapped it during ESD tests. All I need is a
    > matching funnel (wording?) and hot air to remove the IC and a
    > soldering iron with a hoof shaped tip and a magnifier to solder the
    > new one. Well, some solder wick could be necessary.
    >


    It's usually called nozzle. As you said, you can buy square nozzles for
    stations such as Metcal that blow hot air only onto the pin rows. In our
    systems production it was never a problem to swap a flat pack, even
    large ones. The techs could do that in minutes. BGAs are a whole 'nother
    matter, a real pain to get off the board without damage.

    --
    Regards, Joerg

    http://www.analogconsultants.com
     
    Joerg, Oct 15, 2006
    #19
  20. Oliver Betz Guest

    Joerg wrote:

    [desolder TQGP]

    >> microcontroller when I zapped it during ESD tests. All I need is a
    >> matching funnel (wording?) and hot air to remove the IC and a
    >> soldering iron with a hoof shaped tip and a magnifier to solder the
    >> new one. Well, some solder wick could be necessary.

    >
    >It's usually called nozzle. As you said, you can buy square nozzles for


    thanks, nozzle is the word I didn't remember. We have one with a
    spring loaded vacuum cup, so the TQFP is lifted automatically as soon
    as the solder is molten. Really easy to use and not very expensive.

    Oliver
    --
    Oliver Betz, Muenchen (oliverbetz.de)
     
    Oliver Betz, Oct 15, 2006
    #20
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Electronic-OEM

    BGA Heatsink 23000

    Electronic-OEM, May 13, 2004, in forum: IBM
    Replies:
    0
    Views:
    331
    Electronic-OEM
    May 13, 2004
  2. Ian McBride

    Prototyping BGA's

    Ian McBride, Sep 3, 2003, in forum: Embedded
    Replies:
    2
    Views:
    623
    Myren
    Sep 12, 2003
  3. Alex Vinokur
    Replies:
    0
    Views:
    581
    Alex Vinokur
    Oct 30, 2005
  4. karthikbg
    Replies:
    2
    Views:
    363
    karthikbg
    Feb 1, 2007
  5. Mohanajeeva.D
    Replies:
    0
    Views:
    360
    Mohanajeeva.D
    Jul 2, 2010
Loading...

Share This Page