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Future: 0603 versus 0402 parts

Discussion in 'Electronic Design' started by Joerg, Mar 13, 2007.

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  1. Joerg

    Joerg Guest

    Ok, have to decide whether to default to 0603 or 0402 for resistors and
    stuff on a new design. Wow, this time I am not size constrained.

    Looking at Digikey it comes up with 143 pages (has risen) for 0402
    resistors and 218 pages for 0603. Looking at prices 0603 still has a leg
    up, around $0.003 for a 10K while its 0402 counterpart runs about twice
    that. Is 0603 going to be a good choice for the next years? Or better
    stick to 0402?

    Of course from a debug point of view I hate to deal with 0402. With
    chips the situation seems to be more clear cut. Things definitely seem
    to be going TSSOP there.
     
  2. John Larkin

    John Larkin Guest

    My production people hate 0402's... they tombstone a lot. We still use
    0805's when there's plenty of room, 0603's for tight stuff, occasional
    0402's for picosecond stuff where it matters.

    You can still buy lots of 1206's and 2010's and such. They're not
    going away.

    Looks like some parts are appearing only in those drecky
    leadless/chipscale packages. Yuk.

    John
     
  3. dalai lamah

    dalai lamah Guest

    Un bel giorno Joerg digitò:
    I have to say that it's easier than I thought. They are still relatively
    easy to hand solder; of course you need a microscope, but I wasn't able to
    solder 0603 without it either. The problem with 0402 is the production: a
    lot of assembliers still have problems with very close 0603 components,
    with 0402 it will be even worse.
    I think that very soon BGA (and hidden pins in general) will be the default
    for all the ICs, not only the hundreds-pinned. You can already see this
    trend, there are already a lot of logic ICs - even with few pins - with BGA
    and/or flipchip package options. This worries me a lot more than discrete
    components; 0402 can still be handled, but BGA means that you have to
    change completely your procedures (design, PCB routing, prototyping,
    testing...).
     
  4. Joerg

    Joerg Guest

    Hmm, I never had tombstoning with those. OTOH nearly all my clients
    contract out circuit board stuffing so they don't have to bother with
    that. Sometimes even the whole production. Sometimes I have a chat with
    the contract producers and they'd tell me if they weren't happy with
    parts of a design. Like when zeners began to miss data sheet limits I
    had an instant email from China about it.

    Good to know, thanks.

    I really hate it when there is a cooling pad that must be soldered, on
    parts that consume less than 20mW. Arrgh. I have begun to shun parts
    that don't come in TSSOP. Too much trouble. And when they stop the
    migration path for a part at the SOIC level that is a red flag in terms
    of remaining product life.
     
  5. Joerg

    Joerg Guest

    I use 3x glasses and do it sans microscope. Unless the client has a
    camera-monitor setup.
    Hmm, haven't seen that trend yet. Most of my stuff (analog and logic) is
    migrating towards TSSOP.
     
  6. Eeyore

    Eeyore Guest

    Why exactly ?

    Graham
     
  7. Joerg

    Joerg Guest

    Concerns about production life. Same back in the days when SO came out.
    Stuff that wasn't migrated in due course had a tendency to become
    unobtanium ;-)
     
  8. Brian

    Brian Guest

    As a "board stuffer", I'll say a few things.

    As you get smaller, assembly houses have to be better to do it. 0603
    is a "knee" level for that right now. As the placement is needs to be
    more accurate for smaller parts, more will be off one pad and
    tombstone. However, with better equipment, the difference isn't as
    bad.

    Bigger parts are more robust in many ways. Thermal transfer,mechanical
    strength, etc. Board contamination, water, etc., is less likely to
    cause an issue with larger parts.

    I say use the biggest parts you can fit in the required space, all the
    way up to 1206 (the price is not that big a difference). There is no
    real good reason to go smaller if you do not need the space. If your
    cost of 0805 vs 0603 is killing your margins, you are better off
    examining new markets or products. Yours are dead.

    Yes, I know about high-speed and using smaller caps. But whenever I
    here this, I see 0201's on a board running 20Mhz or less. No, you are
    not improving anything then.
     
  9. dalai lamah

    dalai lamah Guest

    Un bel giorno Joerg digitò:
    And at the end of the day you can still find the way home? ;)
    Same here, SOIC is becoming quite a rarity in my designs, almost everything
    is TSSOP. But more and more frequently, when you open the datasheet of some
    logic IC, you can find the microscopic BGA package options like VFBGA and
    WCSP, or perhaps when you are lucky the (still annoying to hand solder)
    QFN:

    http://focus.ti.com/logic/docs/generalcontent.tsp?templateId=5985&navigationId=11373&contentId=4139
    http://focus.ti.com/pdfs/logic/packcard7.pdf
     
  10. Joerg

    Joerg Guest

    Nope. Client brings me to the hotel. Then I only have to find the way to
    a local pub :)))
    BGA is a pain. You can't see whether it's soldered right. Luckily all
    the chips I need come in TSSOP. I was extremely glad when they even
    ported the old CD4000 series to TSSOP.
     
  11. Joerg

    Joerg Guest

    It's always good to hear from the folks who actually have to produce
    what we design. You guys really know what works and what doesn't.


    Well, looks like I should stay with 0603 then. 0805 would become a bit
    tight on this board but I shall see when the schematics are done.
    Nope. I have designed on the cutting edge in terms of cost for a couple
    of decades now. Most others cannot understand how a human being can
    possibly enjoy doing that. But I do. Then there are the devices that
    just have to be small. Medical disposables, for example. On many of
    those a SOT-23 would look like a boulder. I remember not being able to
    use a TLV431 because it didn't come any smaller than SOT-23 at that time.

    I promise I won't do that unless necessary :)

    BTW, do you mind sharing the name or web site of your company? My
    clients are always on the lookout for good SMT prototype assembly.
     
  12. Brian

    Brian Guest

    Use the largest you have room for, even if it is a 1206. Smaller is
    not "better" unless you need the room (yes, I know, small caps at high
    speed, but whenever I hear that, its on a sub 12Mhz design). A better
    machine is needed to place 0402 vs 0603, and those can be "limits" for
    certian places, meaning even those sizes may be marginal on placement.
    If you see alot of green on your board, why not use larger components
    the human eye can see? Why make it harder, potentially less reliable
    and dificult to repair?

    If a few tenths of a cent is going to break your profit margin, your
    market is too old and ready to die. Reevaluate your products and
    markets instead of shaving pennies.
     
  13. Brian

    Brian Guest

    Sorry for the semi "double" post. Google groups sucks, but my ISP has
    no newsserver :( Seemed to not go thru the first try, then shows up
    later. Go figure.
     
  14. DJ Delorie

    DJ Delorie Guest

    I use 2x and 3.5x mag visors, and after a while with the 3.5x on, I
    can't focus on regular things any more. It takes a few minutes to
    re-adjust. So, I try to use the *weakest* lens that works for the
    part sizes I'm working with.
    My last design (still debugging it ;) is primarily 0603 and tssop,
    with sot-323 transistors. The occasional ssop (0.65mm pitch) seems
    big to me now. I had SOICs on my last board, but only because it was
    a RAM array and I wanted to run traces between the pins without
    horrendously expensive fab costs, and it was a 5v design which limited
    chip selection.

    But, I've done boards by hand with tvssop (0.4mm pitch) and 01005
    parts. It can be done, and it puts the larger (hah) parts in
    perspective.
     
  15. I saw some 0402 tombstoning on a fairly recent batch of boards from a
    China assembly facility (SnPb process). Zero problems with the 0805s
    (no 0603s on that design).
    You may not like the price, though.



    Best regards,
    Spehro Pefhany
     
  16. Joerg

    Joerg Guest

    One of the problems with a mixed design (where there are also some large
    devices on the PCB) seems to be the paste. Too much and you get
    tombstoning, too little and the big parts won't solder reliably. Like
    those pellet stoves where they haven't figured out how to automate
    intake air. Throttle too high and it'll go out on "1". Throttle too low
    and it'll smoke on "3" or higher.
    Actually a 1ohm 1206 costs roughly the same as a 10K in 0402, around
    $0.007. A 2010 size can pop to several cents. Still, I don't see a
    reason for anything larger than 0603 unless it is in a current sense
    path or RF bridge.

    [...]
     
  17. Joerg

    Joerg Guest

    That was for larger quantities.
     
  18. Joerg

    Joerg Guest

    Interesting. 0402 caps in my case would only be 0.01uF and smaller
    though, the rest would be mostly 0805. But as Brian said, it may be best
    to keep it as large as practical. 0603 for resistors and 0805 for most
    caps is certainly in the cards on this design, maybe even 0805 for
    everything.
     
  19. MassiveProng

    MassiveProng Guest

    Both will remain in use and production for years to come.

    Even 0805 will.
     
  20. Joerg

    Joerg Guest

    Yeah, lots of people have that issue. I feel blessed. My ISP changed
    hands twice, PacificBell -> SBC -> AT&T, but they always kept a nice NG
    access. Even binaries are allowed which is really helpful for schematics
    and photos.
     
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