Forums

MLCC soldering and dielectric cracking damage

Started by Mr.CRC October 23, 2011
On 10/23/2011 07:03 PM, Mr.CRC wrote:
> Hi: > > I frequently assemble PCBs by hand soldering MLCCs of the 0603, 0805, > 1206, and a few larger ones (and other parts too--as those > capacitor-only circuits aren't much fun!). > > My hand soldering technique is to use 0.015" wire solder, > 1. first adding a tiny bit of solder to one pad. > 2. Then I flux both pads, and tack the part to the pad with the added > solder. > 3. Sometimes at this point, I put my tweezers on top of the part to > create a downward force, and reflow the tacked joint to make the part > seat squarely on the pads. > 4. Then I solder the other pad-to-part joint. > 5. If necessary to make it look nicer, I add flux and reflow the tacked > joint. > > The question is this: How much should I worry about thermal stress > cracking or otherwise damaging the MLCC dielectrics? > > I have heard that using a pre-heated PCB, and soldering the MLCCs both > joints at once using hot air is the preferred approach, to avoid damage. > > Also, that MLCCs with thinner dielectrics are more susceptible, like > high values in small sizes. > > Yet in practice, I've never noticed a bad part. Then again, since most > of them are bypass caps, it's hard to notice a bad part. > > Any experiences with soldering causing MLCC damage? > > How about board flexing? What amount of flex causes trouble? Ordinary > fondling? Assembling CPU coolers onto PC motherboards is always a > treacherous experience! I wonder how many MLCCs survive that experience.
When working with some RF prototypes, built on 0.8 mm FR4 boards, we had some failures due to (suspected) flexing causing capacitor end caps to become loose. This might be called ordinary fondling. We even resorted to stiffening these prototypes soldering some thin strips of ordinary board perpendicular to the board along the long side. Pere
langwadt@fonz.dk wrote:
> On 23 Okt., 19:12, Joerg <inva...@invalid.invalid> wrote: >> Mr.CRC wrote: >>> Hi: >>> I frequently assemble PCBs by hand soldering MLCCs of the 0603, 0805, >>> 1206, and a few larger ones (and other parts too--as those >>> capacitor-only circuits aren't much fun!). >>> My hand soldering technique is to use 0.015" wire solder, >>> 1. first adding a tiny bit of solder to one pad. >> Why not soldering the part onto that pads right away? That how I do it. >> >>> 2. Then I flux both pads, and tack the part to the pad with the added >>> solder. >> I never use extra flux when soldering such SMT parts. The solder I use >> it 0.015" Kester 8806 No-Clean, leaded. >> >>> 3. Sometimes at this point, I put my tweezers on top of the part to >>> create a downward force, and reflow the tacked joint to make the part >>> seat squarely on the pads. >> Tweezers are metal, can scratch and stress the part. I use a toothpick, >> usually. A fresh one :-) >> >>> 4. Then I solder the other pad-to-part joint. >>> 5. If necessary to make it look nicer, I add flux and reflow the tacked >>> joint. >> Suggest to try to practise until they look good without re-fluxing. >> >>> The question is this: How much should I worry about thermal stress >>> cracking or otherwise damaging the MLCC dielectrics? >> IME it becomes a concern for packages larger than 1812. This goes for >> normal PCB thickness. >> >>> I have heard that using a pre-heated PCB, and soldering the MLCCs both >>> joints at once using hot air is the preferred approach, to avoid damage. >>> Also, that MLCCs with thinner dielectrics are more susceptible, like >>> high values in small sizes. >>> Yet in practice, I've never noticed a bad part. Then again, since most >>> of them are bypass caps, it's hard to notice a bad part. >>> Any experiences with soldering causing MLCC damage? >> I've seen failed parts but (so far) never on boards I hand-assembled. >> >>> How about board flexing? What amount of flex causes trouble? Ordinary >>> fondling? ... >> Fondling? Hey, that can get you in trouble with the laws :-) >> >>> ... Assembling CPU coolers onto PC motherboards is always a >>> treacherous experience! I wonder how many MLCCs survive that experience. >> That one I don't understand. How can such coolers stress the caps? >> > > they are usually attached to the board with some contraption made of > springs clips > and standoffs that need to snap into holes in the board, it can take > scary amount > of force and bending of the board to make it happen >
Interesting. Is that done on "economy class" PCs? I only know the ones that get screwed into place. Similar to this one: http://media.photobucket.com/image/cpu%20cooler%20-%20foxconn/disiniaje3/FOXCOON%20COOLER/Foxconn-CPU-Cooler-NBT-CMI77512S3-C.jpg?o=1 -- Regards, Joerg http://www.analogconsultants.com/
"krw@att.bizzzzzzzzzzzz" wrote:
> > What do you expect from AlwaysWrong?
Absolutely nothing. -- You can't have a sense of humor, if you have no sense.
On 24 Okt., 18:50, Joerg <inva...@invalid.invalid> wrote:
> langw...@fonz.dk wrote: > > On 23 Okt., 19:12, Joerg <inva...@invalid.invalid> wrote: > >> Mr.CRC wrote: > >>> Hi: > >>> I frequently assemble PCBs by hand soldering MLCCs of the 0603, 0805, > >>> 1206, and a few larger ones (and other parts too--as those > >>> capacitor-only circuits aren't much fun!). > >>> My hand soldering technique is to use 0.015" wire solder, > >>> 1. first adding a tiny bit of solder to one pad. > >> Why not soldering the part onto that pads right away? That how I do it=
.
> > >>> 2. Then I flux both pads, and tack the part to the pad with the added > >>> solder. > >> I never use extra flux when soldering such SMT parts. The solder I use > >> it 0.015" Kester 8806 No-Clean, leaded. > > >>> 3. Sometimes at this point, I put my tweezers on top of the part to > >>> create a downward force, and reflow the tacked joint to make the part > >>> seat squarely on the pads. > >> Tweezers are metal, can scratch and stress the part. I use a toothpick=
,
> >> usually. A fresh one :-) > > >>> 4. Then I solder the other pad-to-part joint. > >>> 5. If necessary to make it look nicer, I add flux and reflow the tack=
ed
> >>> joint. > >> Suggest to try to practise until they look good without re-fluxing. > > >>> The question is this: =A0How much should I worry about thermal stress > >>> cracking or otherwise damaging the MLCC dielectrics? > >> IME it becomes a concern for packages larger than 1812. This goes for > >> normal PCB thickness. > > >>> I have heard that using a pre-heated PCB, and soldering the MLCCs bot=
h
> >>> joints at once using hot air is the preferred approach, to avoid dama=
ge.
> >>> Also, that MLCCs with thinner dielectrics are more susceptible, like > >>> high values in small sizes. > >>> Yet in practice, I've never noticed a bad part. =A0Then again, since =
most
> >>> of them are bypass caps, it's hard to notice a bad part. > >>> Any experiences with soldering causing MLCC damage? > >> I've seen failed parts but (so far) never on boards I hand-assembled. > > >>> How about board flexing? =A0What amount of flex causes trouble? =A0Or=
dinary
> >>> fondling? ... > >> Fondling? Hey, that can get you in trouble with the laws :-) > > >>> =A0 =A0 =A0 =A0 =A0... Assembling CPU coolers onto PC motherboards is=
always a
> >>> treacherous experience! =A0I wonder how many MLCCs survive that exper=
ience.
> >> That one I don't understand. How can such coolers stress the caps? > > > they are usually attached to the board with some contraption made of > > springs clips > > and standoffs that need to snap into holes in the board, it can take > > scary amount > > of force and bending of the board to make it happen > > Interesting. Is that done on "economy class" PCs? I only know the ones > that get screwed into place. Similar to this one: > > http://media.photobucket.com/image/cpu%20cooler%20-%20foxconn/disinia... >
I believe it is the standard intel cooler, it looks similar but instead of screws and a bracket it has four snap in plastic things like this: http://www.youtube.com/watch?v=3Dp6hrV1yMRKo -Lasse
langwadt@fonz.dk wrote:
> On 24 Okt., 18:50, Joerg <inva...@invalid.invalid> wrote: >> langw...@fonz.dk wrote: >>> On 23 Okt., 19:12, Joerg <inva...@invalid.invalid> wrote: >>>> Mr.CRC wrote: >>>>> Hi: >>>>> I frequently assemble PCBs by hand soldering MLCCs of the 0603, 0805, >>>>> 1206, and a few larger ones (and other parts too--as those >>>>> capacitor-only circuits aren't much fun!). >>>>> My hand soldering technique is to use 0.015" wire solder, >>>>> 1. first adding a tiny bit of solder to one pad. >>>> Why not soldering the part onto that pads right away? That how I do it. >>>>> 2. Then I flux both pads, and tack the part to the pad with the added >>>>> solder. >>>> I never use extra flux when soldering such SMT parts. The solder I use >>>> it 0.015" Kester 8806 No-Clean, leaded. >>>>> 3. Sometimes at this point, I put my tweezers on top of the part to >>>>> create a downward force, and reflow the tacked joint to make the part >>>>> seat squarely on the pads. >>>> Tweezers are metal, can scratch and stress the part. I use a toothpick, >>>> usually. A fresh one :-) >>>>> 4. Then I solder the other pad-to-part joint. >>>>> 5. If necessary to make it look nicer, I add flux and reflow the tacked >>>>> joint. >>>> Suggest to try to practise until they look good without re-fluxing. >>>>> The question is this: How much should I worry about thermal stress >>>>> cracking or otherwise damaging the MLCC dielectrics? >>>> IME it becomes a concern for packages larger than 1812. This goes for >>>> normal PCB thickness. >>>>> I have heard that using a pre-heated PCB, and soldering the MLCCs both >>>>> joints at once using hot air is the preferred approach, to avoid damage. >>>>> Also, that MLCCs with thinner dielectrics are more susceptible, like >>>>> high values in small sizes. >>>>> Yet in practice, I've never noticed a bad part. Then again, since most >>>>> of them are bypass caps, it's hard to notice a bad part. >>>>> Any experiences with soldering causing MLCC damage? >>>> I've seen failed parts but (so far) never on boards I hand-assembled. >>>>> How about board flexing? What amount of flex causes trouble? Ordinary >>>>> fondling? ... >>>> Fondling? Hey, that can get you in trouble with the laws :-) >>>>> ... Assembling CPU coolers onto PC motherboards is always a >>>>> treacherous experience! I wonder how many MLCCs survive that experience. >>>> That one I don't understand. How can such coolers stress the caps? >>> they are usually attached to the board with some contraption made of >>> springs clips >>> and standoffs that need to snap into holes in the board, it can take >>> scary amount >>> of force and bending of the board to make it happen >> Interesting. Is that done on "economy class" PCs? I only know the ones >> that get screwed into place. Similar to this one: >> >> http://media.photobucket.com/image/cpu%20cooler%20-%20foxconn/disinia... >> > > I believe it is the standard intel cooler, it looks similar but > instead of > screws and a bracket it has four snap in plastic things > > like this: http://www.youtube.com/watch?v=p6hrV1yMRKo >
Ouch! I don't think I'd want to buy a PC with such a motherboard. Judging from the groans of the guy the installation must require quite some force. I like this text under the video: "avec installation du heatsink". Oh, if the French language police would ever see that :-) -- Regards, Joerg http://www.analogconsultants.com/
On 24 Okt., 21:24, Joerg <inva...@invalid.invalid> wrote:
> langw...@fonz.dk wrote: > > On 24 Okt., 18:50, Joerg <inva...@invalid.invalid> wrote: > >> langw...@fonz.dk wrote: > >>> On 23 Okt., 19:12, Joerg <inva...@invalid.invalid> wrote: > >>>> Mr.CRC wrote: > >>>>> Hi: > >>>>> I frequently assemble PCBs by hand soldering MLCCs of the 0603, 080=
5,
> >>>>> 1206, and a few larger ones (and other parts too--as those > >>>>> capacitor-only circuits aren't much fun!). > >>>>> My hand soldering technique is to use 0.015" wire solder, > >>>>> 1. first adding a tiny bit of solder to one pad. > >>>> Why not soldering the part onto that pads right away? That how I do =
it.
> >>>>> 2. Then I flux both pads, and tack the part to the pad with the add=
ed
> >>>>> solder. > >>>> I never use extra flux when soldering such SMT parts. The solder I u=
se
> >>>> it 0.015" Kester 8806 No-Clean, leaded. > >>>>> 3. Sometimes at this point, I put my tweezers on top of the part to > >>>>> create a downward force, and reflow the tacked joint to make the pa=
rt
> >>>>> seat squarely on the pads. > >>>> Tweezers are metal, can scratch and stress the part. I use a toothpi=
ck,
> >>>> usually. A fresh one :-) > >>>>> 4. Then I solder the other pad-to-part joint. > >>>>> 5. If necessary to make it look nicer, I add flux and reflow the ta=
cked
> >>>>> joint. > >>>> Suggest to try to practise until they look good without re-fluxing. > >>>>> The question is this: =A0How much should I worry about thermal stre=
ss
> >>>>> cracking or otherwise damaging the MLCC dielectrics? > >>>> IME it becomes a concern for packages larger than 1812. This goes fo=
r
> >>>> normal PCB thickness. > >>>>> I have heard that using a pre-heated PCB, and soldering the MLCCs b=
oth
> >>>>> joints at once using hot air is the preferred approach, to avoid da=
mage.
> >>>>> Also, that MLCCs with thinner dielectrics are more susceptible, lik=
e
> >>>>> high values in small sizes. > >>>>> Yet in practice, I've never noticed a bad part. =A0Then again, sinc=
e most
> >>>>> of them are bypass caps, it's hard to notice a bad part. > >>>>> Any experiences with soldering causing MLCC damage? > >>>> I've seen failed parts but (so far) never on boards I hand-assembled=
.
> >>>>> How about board flexing? =A0What amount of flex causes trouble? =A0=
Ordinary
> >>>>> fondling? ... > >>>> Fondling? Hey, that can get you in trouble with the laws :-) > >>>>> =A0 =A0 =A0 =A0 =A0... Assembling CPU coolers onto PC motherboards =
is always a
> >>>>> treacherous experience! =A0I wonder how many MLCCs survive that exp=
erience.
> >>>> That one I don't understand. How can such coolers stress the caps? > >>> they are usually attached to the board with some contraption made of > >>> springs clips > >>> and standoffs that need to snap into holes in the board, it can take > >>> scary amount > >>> of force and bending of the board to make it happen > >> Interesting. Is that done on "economy class" PCs? I only know the ones > >> that get screwed into place. Similar to this one: > > >>http://media.photobucket.com/image/cpu%20cooler%20-%20foxconn/disinia..=
.
> > > I believe it is the standard intel cooler, it looks similar but > > instead of > > screws and a bracket it has four snap in plastic things > > > like this:http://www.youtube.com/watch?v=3Dp6hrV1yMRKo > > Ouch! I don't think I'd want to buy a PC with such a motherboard. > Judging from the groans of the guy the installation must require quite > some force. >
yep and because they are either in or out you cannot do like with screws and tighten them slowly in criss cross pattern
> I like this text under the video: "avec installation du heatsink". Oh, > if the French language police would ever see that :-) >
lol -Lasse
langwadt@fonz.dk wrote:
> On 24 Okt., 21:24, Joerg <inva...@invalid.invalid> wrote: >> langw...@fonz.dk wrote:
[...]
>>> I believe it is the standard intel cooler, it looks similar but >>> instead of >>> screws and a bracket it has four snap in plastic things >>> like this:http://www.youtube.com/watch?v=p6hrV1yMRKo >> Ouch! I don't think I'd want to buy a PC with such a motherboard. >> Judging from the groans of the guy the installation must require quite >> some force. >> > > yep and because they are either in or out you cannot do like with > screws > and tighten them slowly in criss cross pattern >
When I see technically inferior "solutions" such as this I have no qualms taking the angle grinder to it. Whirrrrr ... zzzzrrring ... thwack ... gone. Then I'd relace them with screws. [...] -- Regards, Joerg http://www.analogconsultants.com/
On Mon, 24 Oct 2011 10:11:28 -0500, "krw@att.bizzzzzzzzzzzz"
<krw@att.bizzzzzzzzzzzz> wrote:

>On Mon, 24 Oct 2011 17:47:19 +0800, "Dennis" <jon.dough@ithemorgue.com> wrote: > >> >>"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message >>news:urv9a7tqav37835ple7sor2o41flq3t3bl@4ax.com... >>> On Mon, 24 Oct 2011 12:22:48 +0800, "Dennis" >>> <jon.dough@ithemorgue.com> wrote: >>> >>>> >>>>"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in >>>>message >>>>news:nlo9a7pd96q3nctj0teifeviq27r0u5qj5@4ax.com... >>>>> On Sun, 23 Oct 2011 20:48:55 -0700, TheGlimmerMan >>>>> <justaglimmer@thebarattheendoftheuniverse.org> wrote: >>>>> >>>>>>On Sun, 23 Oct 2011 20:38:57 -0700, John Larkin >>>>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>>>> >>>>>>>Our field failure rates are healthy multiples of Bellcore >>>>>>>calculations. Ceramic cap failures are rare. >>>>>> >>>>>> None of your production boards are hand soldered, you retarded twit. >>>>> >>>>> As I noted, some are. >>>>> >>>>> John >>>>> >>>> >>>>Black list the idiot John. I only see his crap when people reply to him. >>>>;) >>>> >>> >>> I usually do, but he said some silly stuff about soldering caps. >>> >>> John >>> >> >>The work enviroments I've been in I've always hand soldered SMD parts mainly >>for prototypes but also some low vol production. Never had a problem (thats >>not to say that will always be the case!) > >Repair, and debug, also. > >What do you expect from AlwaysWrong?
Of all the discreet parts one can solder onto a board, the MLCC part has the greatest susceptibility to have its 'manufactured as' value get floated by a thermal shock to some unknown value. It makes no difference that your fucking assembly still worked. Not only are you too dumb to know that the thermal shock alters the part, but you are too dumb (obviously) to know why, and far too dumb to ever be able to detect it or make any sort of valid rebuttal. All you mealy mouthed twits can do is meaningless bird chatter. The bacteria in my ass chad has more on the ball than all you fucktards put together.
"TheGlimmerMan" <justaglimmer@thebarattheendoftheuniverse.org> wrote in 
message news:ml4ca7hb2dhhkjgvaohs3u4b9r757g45u0@4ax.com...
> On Mon, 24 Oct 2011 10:11:28 -0500, "krw@att.bizzzzzzzzzzzz" > <krw@att.bizzzzzzzzzzzz> wrote: > >>On Mon, 24 Oct 2011 17:47:19 +0800, "Dennis" <jon.dough@ithemorgue.com> >>wrote: >> >>> >>>"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in >>>message >>>news:urv9a7tqav37835ple7sor2o41flq3t3bl@4ax.com... >>>> On Mon, 24 Oct 2011 12:22:48 +0800, "Dennis" >>>> <jon.dough@ithemorgue.com> wrote: >>>> >>>>> >>>>>"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in >>>>>message >>>>>news:nlo9a7pd96q3nctj0teifeviq27r0u5qj5@4ax.com... >>>>>> On Sun, 23 Oct 2011 20:48:55 -0700, TheGlimmerMan >>>>>> <justaglimmer@thebarattheendoftheuniverse.org> wrote: >>>>>> >>>>>>>On Sun, 23 Oct 2011 20:38:57 -0700, John Larkin >>>>>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>>>>> >>>>>>>>Our field failure rates are healthy multiples of Bellcore >>>>>>>>calculations. Ceramic cap failures are rare. >>>>>>> >>>>>>> None of your production boards are hand soldered, you retarded >>>>>>> twit. >>>>>> >>>>>> As I noted, some are. >>>>>> >>>>>> John >>>>>> >>>>> >>>>>Black list the idiot John. I only see his crap when people reply to >>>>>him. >>>>>;) >>>>> >>>> >>>> I usually do, but he said some silly stuff about soldering caps. >>>> >>>> John >>>> >>> >>>The work enviroments I've been in I've always hand soldered SMD parts >>>mainly >>>for prototypes but also some low vol production. Never had a problem >>>(thats >>>not to say that will always be the case!) >> >>Repair, and debug, also. >> >>What do you expect from AlwaysWrong? > > Of all the discreet parts one can solder onto a board, the MLCC part > has the greatest susceptibility to have its 'manufactured as' value get > floated by a thermal shock to some unknown value. It makes no difference > that your fucking assembly still worked. > > Not only are you too dumb to know that the thermal shock alters the > part, but you are too dumb (obviously) to know why, and far too dumb to > ever be able to detect it or make any sort of valid rebuttal. > > All you mealy mouthed twits can do is meaningless bird chatter. > > The bacteria in my ass chad has more on the ball than all you fucktards > put together.
ass chad = santorum?
VioletaPachydermata wrote:
> On Sun, 23 Oct 2011 10:03:52 -0700, "Mr.CRC" > <crobcBOGUS@REMOVETHISsbcglobal.net> wrote: > >> Hi: >> >> I frequently assemble PCBs by hand soldering MLCCs of the 0603, 0805, >> 1206, and a few larger ones (and other parts too--as those >> capacitor-only circuits aren't much fun!). >> > > The whole key is temperature soakings and keeping them and their degree > to a minimum. ANY reflowing of chip caps detaches end terminations and > the chip may read correctly but not perform to spec or even fail in use. > > >> My hand soldering technique is to use 0.015" wire solder, >> 1. first adding a tiny bit of solder to one pad. > > The tinier the better, but you must be able to hit the bead with the > chip in place, *without* hitting the chip with the iron. > >> 2. Then I flux both pads, and tack the part to the pad with the added >> solder. > > Only reflow the bead long enough to seat the part square and flat and > allow seizure. Reflux that pad, and then solder the OTHER pad first,very > quickly, only adding heat to the PCB pad, not the chip termination 'end > cap' (of whatever variety). Never go back to that pad again. It is done. > Now solder the other pad to the right fillet size to match the first. > Never reflow either pad. The key is to add no further heat OR thermal > stress to the part internals or the solder terminations. That heat > transfers directly into the chip. These failure modes are very easy to > illustrate with HV caps (MLCCs) They read correct and act correct at low > voltage after thermal damage, but at higher operating voltages, they fail > from end termination detachment issues. > >> 3. Sometimes at this point, I put my tweezers on top of the part to >> create a downward force, > > It must be VERY light force, and the tweezer "noses" must form a flat, > NOT pointed face to press on the chip with, or you can introduce tiny > micro-fractures in the chips. > >> and reflow the tacked joint to make the part >> seat squarely on the pads. > > your first bead should be so tiny that you can place it out of the way > of the squarely placed part, so that when you reflow that tiny bead, it > and the flux and the capillary attraction will lock it down. Only add > heat for the 'moment' of that reflow act, and avoid contact with the > actual terminations of the chips themselves. You are making it tack > down, not be integral yet, so add no more heat than needed to perform > that function. Heat kills chips. > >> 4. Then I solder the other pad-to-part joint. > > That is the correct process step order. > >> 5. If necessary to make it look nicer, I add flux and reflow the tacked >> joint. > > if the tack is small enough, it *should* be your second joint anyway, > just to make the proper electrical connection. The 'tacking' process step > should have been minimal in both solder and the heat infused to do it. > >> The question is this: How much should I worry about thermal stress >> cracking or otherwise damaging the MLCC dielectrics? > > A lot. That is why you take serious steps to develop and follow a strict > process like that which I iterated to you. You may want to differ from > what I gave you, but that is your choice. The killer is heat. Theprocess > is where it gets introduced. One solder joint construction flow (for > effect) is all these chips should be subjected to (there is a severe > shock). They are meant for automated processes where the temp > differential at reflow time is a mere 20 or 40 degrees and the > terminations do not flex to their breakage point. > > So, a hot air reflow (done quickly) with solder paste is an option as > well, but adjacent peripheral components get heated as well. > > For hand assembly, short of preheating the board to a couple hundred > degrees and the chips in a hot pot... if you are soldering them cold, as > it were, the shock *will* be severe, so you have to perform the ops very > quickly and only once, if possible. >> I have heard that using a pre-heated PCB, and soldering the MLCCs both >> joints at once using hot air is the preferred approach, to avoid damage. > > Yes, but do NOT try to do "both joints at once" using soldering irons. > You are actually doing the exact thing you do NOT want to do at that > point. > >> Also, that MLCCs with thinner dielectrics are more susceptible, like >> high values in small sizes. > > It took them many years to be able to even make them. Pretty likely > that they are easier to break or cause to shift from stated specs. > >> Yet in practice, I've never noticed a bad part. > > ceramic caps always appear fine on metrological inspection. > > "At voltage" is when it counts though. HV caps MUST be "good". When a > multiplier cap in an HV circuit fails, one typically replaces all of them > because the time savings is cheaper than trying to find which "good > reading" cap is "really bad". > >> Then again, since most >> of them are bypass caps, it's hard to notice a bad part. > > Unless they cause a problem in that location. > >> Any experiences with soldering causing MLCC damage? > > MLCC damage is usually from soldering. If you strike and break one from > physical contact, it has nothing to do with a normal electronic industry > process. It was some dumb dope who should learn some material handling > practices before he (or she) handles delicate components again. > >> How about board flexing? > > Solder joint physics area different animal. Depends on the pad/fillet > shape, and the type of terminations the part you buy has. > >> What amount of flex causes trouble? > > If your post process assemblies are warped, you have a process issue > other than broken terminations when a stupid tech or manager flexes a > warped, solid board back toward its proper design shape. He needs to > learn some physics. They need to be held FLAT while they are still hot, > all the way until they cool, and if they are still warping, then the PCB > maker has induced it in their MFG process and it needs to be addresses > even further upstream.
Well so far, that was a lot of interesting input.
>> Ordinary >> fondling? > > If you grab a board and flex the fucking thing, you lack knowledge and > experience about soldering, solder creep, and PCB assembly practices. > If it is warped, it is a failure, if it does not fit form fit and > function *WITHOUT* attempting to "undo" the flexure and warpage. > > That is so decidedly NOT "ordinary", by any measure. In some circles, > you would be looking for a new position. > >> Assembling CPU coolers onto PC motherboards is always a >> treacherous experience! > > Not really. Could be an aptitude thing. > >> I wonder how many MLCCs survive that experience. > > Do you walk down the aisle of a crowded train car, shoving folks out of > your way with your elbows as you tromp toward the exit door? > > You one of those asshole dock workers that/who toss packages full of > electronic devices up on the dock because they are too dumb to understand > what the term FRAGILE means? > > You do not assemble electronic assemblies with FORD tools, idiot. In > this case that references your brain. You MUST be a Ford owner! You > sport a Ford owner mentality!
Then you really went off the rails! -- _____________________ Mr.CRC crobcBOGUS@REMOVETHISsbcglobal.net SuSE 10.3 Linux 2.6.22.17