Low MOSFET IDSS current

>I have found if you do not specify the incoming test, companies will ship 
>you the dregs that failed AQL at other companies. As an example, I have   
>received 16 pin HC7474 through hole parts. They were marked 74HC7474, but I 
>don't know of any 16 pin versions. Obviously someone rejected them, so they 
>sent them to us. 

'Companies'? What company was that, something from Knockturn Alley or eBay?

I've never received anything but good parts from the leading distributors. 

Sixteen-pin 74HC74s, forsooth. 

Cheers

Phil Hobbs

On Fri, 15 Dec 2017 22:58:41 GMT, Steve Wilson <no@spam.com> wrote:

>John Larkin <jjlarkin@highland_snip_technology.com> wrote:
>
>> On Fri, 15 Dec 2017 19:56:04 GMT, Steve Wilson <no@spam.com> wrote:
> 
>>>John Larkin <jjlarkin@highland_snip_technology.com> wrote:
>
>>>> OK, let's. How do you manage incoming parts quality?
> 
>>>> If you get a reel of 3000 0603 capacitors, what do you do?
> 
>>>See 6.2. Test Product for Acceptability: Lot Acceptance Sampling
>
>>>This section describes how to make decisions on a lot-by-lot basis
>>>whether to accept a lot as likely to meet requirements or reject the
>>>lot as likely to have too many defective units.
>
>>>This section consists of the following topics.
>
>>>  What is Acceptance Sampling?
>>>  What kinds of Lot Acceptance Sampling Plans (LASPs) are there?
>>>  How do you Choose a Single Sampling Plan?
>>>      Choosing a Sampling Plan: MIL Standard 105D
>>>      Choosing a Sampling Plan with a given OC Curve
>>>  What is Double Sampling? 
>>>  What is Multiple Sampling?
>>>  What is a Sequential Sampling Plan?
>>>  What is Skip Lot Sampling?
>
>>>http://www.itl.nist.gov/div898/handbook/pmc/section2/pmc2.htm     
>
>>>Other excellent references on the web. 
>
>> That's sounding like the quality-control ritual blather.
>
>The math is real. A lot of companies depend on it.
> 
>> What exactly do YOU DO when you get that reel of caps?
> 
>That's what I am setting up now. I am leaning towards automated testing and 
>logging the results. A simple reel tester shouldn't cost much to make, and 
>could be very fast.

All hat and no horse.


>
>I have found if you do not specify the incoming test, companies will ship 
>you the dregs that failed AQL at other companies. As an example, I have  
>received 16 pin HC7474 through hole parts. They were marked 74HC7474, but I 
>don't know of any 16 pin versions. Obviously someone rejected them, so they 
>sent them to us.

Marked 74HC7474? That's funny. I guess on a 16-pin part, there's more
room for text.

>
>I was hoping some mfg guys would chime in and tell us their horror stories.

Buy from authorized distributors. Real 74HC74s are so cheap, there's
no reason to buy from counterfeiters. Or to do receiving testing.


-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

pcdhobbs@gmail.com wrote:

> I'm sure they do, but my shop is about 1100 square feet and 2-1/2
> people, and there's only so much mojo to go round. The cost of the
> equipment is a nit by comparison with labour and (especially)
> opportunity cost.  

You will need more space when you go to high volume.
 
> Plus we'd have to put those parts back into reels after testing, and all
> for (very probably) no benefit. 

Why remove the parts for testing? Use heated shaft to punch two holes through 
the top cover tape. At the next station, insert two kelvin leads to measure 
the component.

You could also cut the tape after measuring to kit for assembly.
 
> No thanks. 
 
> Cheers
 
> Phil Hobbs
 

pcdhobbs@gmail.com wrote:

>>I have found if you do not specify the incoming test, companies will ship
>>you the dregs that failed AQL at other companies. As an example, I have 
>>received 16 pin HC7474 through hole parts. They were marked 74HC7474,
>>but  I  don't know of any 16 pin versions. Obviously someone rejected
>>them, so they  sent them to us. 

> 'Companies'? What company was that, something from Knockturn Alley or eBay?

I forget. It was a while ago, before ebay. The only suppliers were the big 
national brands, and we only bought from them. But they screwed up a lot.
 
> I've never received anything but good parts from the leading distributors. 

I'm sure. But there's always human error, especially when you go to higher 
volume.
 
> Sixteen-pin 74HC74s, forsooth. 
 
> Cheers
 
> Phil Hobbs
 

Den lørdag den 16. december 2017 kl. 00.06.05 UTC+1 skrev pcdh...@gmail.com:
> >>> Modern parts and procedures should be a 
> >>> lot more reliable. 
>   
> >> Maybe.  But the sheer amount of fixturing and labour involved in testing 
> >> every kind of part that we use would make the whole thing uneconomic. 
> >> Parts are cheap, but labour is expensive, and fixtures take up a lot of 
> >> space. 
>   
> >I've been thinking about that. An automated tester shouldn't be very 
> >complicated. Separate jigs for diferent size smd's. A little stepper to 
> >advance the reel to the next component. A fast precision LCR meter to 
> >measure the components. 0.1% should be good enough for most parts. 
> 
> >Perhaps a small Teensy or Arduino to log the measurements and step the 
> >reel. Some of the guys on Hackaday do fantastic work on small mechanisms.
> 
> I'm sure they do, but my shop is about 1100 square feet and 2-1/2 people, and there's only so much mojo to go round. The cost of the equipment is a nit by comparison with labour and (especially) opportunity cost.  
> 
> Plus we'd have to put those parts back into reels after testing, and all for (very probably) no benefit. 
> 
> No thanks. 
> 

afaiu at one of the places we get stuff assembled the pnp machine measures components on the way from tape to pcb

though I have no idea if it is just a coarse measurement to check direction 
of diodes and rough value of resistors and capacitors

John Larkin <jjlarkin@highland_snip_technology.com> wrote:

>>I was hoping some mfg guys would chime in and tell us their horror
>>stories. 
 
> Buy from authorized distributors. Real 74HC74s are so cheap, there's
> no reason to buy from counterfeiters. Or to do receiving testing.
 
Of course, we only buy from authorized distributors. No ebay or surplus 
houses.

If you don't do incoming inspection, how do you know they haven't sent you 
parts that failed AQL at some other company?

If you don't do AQL, how do you know the distribution of the parts?

It seems you are taking a lot for granted. I'm not so trusting.

Especially when I think it might be able to test a whole reel, perhaps in 
under ten minutes including setup.

I've been in reasonable volume production before. You have no time when it 
hits to do a proper job, and you spend a great deal of time reccovering 
from mistakes and bad or wrong parts.

The time to solve these problems is right at the beginning.

You have excellent stock inventory programs. These are invaluable, and must 
have taken time to write and debug. You know where you get the parts, how 
much they cost, and how many you have used.

But you have no idea if the parts actually meet spec, or what you are 
putting in your product.

>Why remove the parts for testing? Use heated shaft to punch two holes through 
>the top cover tape. At the next station, insert two kelvin leads to measure 
>the component. 

>You could also cut the tape after measuring to kit for assembly.

Yah, I could do a lot of other unproductive things too. But I could also spent the time designing new stuff, which is way more fun and way more lucrative than picking largely theoretical nits in production. 

Cheers

Phil Hobbs

>> Buy from authorized distributors. Real 74HC74s are so cheap, there's 
>> no reason to buy from counterfeiters. Or to do receiving testing. 
  
>Of course, we only buy from authorized distributors. No ebay or surplus 
houses. 

*cough* *splutter* You had to say that when I had a mouth full of coffee. 

An *authorized distributor* sent you 16-pin DIPs marked '74HC7474'?

Do tell. 

Cheers

Phil Hobbs

On Sat, 16 Dec 2017 00:37:35 GMT, Steve Wilson <no@spam.com> wrote:

>John Larkin <jjlarkin@highland_snip_technology.com> wrote:
>
>>>I was hoping some mfg guys would chime in and tell us their horror
>>>stories. 
> 
>> Buy from authorized distributors. Real 74HC74s are so cheap, there's
>> no reason to buy from counterfeiters. Or to do receiving testing.
> 
>Of course, we only buy from authorized distributors. No ebay or surplus 
>houses.
>
>If you don't do incoming inspection, how do you know they haven't sent you 
>parts that failed AQL at some other company?

No serious distributor would do that. They would lose their principals
ASAP.

And no parts would fail someone's incoming inspection without the
manufacturer knowing about it.

>
>If you don't do AQL, how do you know the distribution of the parts?
>
>It seems you are taking a lot for granted. I'm not so trusting.

If you divert your energy into sidetracks like this, you won't
survive. Put your energy into designing and selling and supporting
products. In the very rare case that you have a part problem, fix it.

If you don't ship, you will never have quality problems.

>
>Especially when I think it might be able to test a whole reel, perhaps in 
>under ten minutes including setup.
>
>I've been in reasonable volume production before. You have no time when it 
>hits to do a proper job, and you spend a great deal of time reccovering 
>from mistakes and bad or wrong parts.

We check one or two parts on each received reel to see if they are the
right value. We have a machine-vision thing that inspects built boards
for soldering, part number, orientation, all that. After all, you
could pick a part from a reel and put it in the wrong place, or
backwards, or something.

Our auto P+P does inspection during placement.



>
>The time to solve these problems is right at the beginning.
>
>You have excellent stock inventory programs. These are invaluable, and must 
>have taken time to write and debug. You know where you get the parts, how 
>much they cost, and how many you have used.
>
>But you have no idea if the parts actually meet spec, or what you are 
>putting in your product.

We inspect and test every production unit extensively. Bad parts will
show up there, and occasionally they do.

We trust a bunch of suppliers to do things right. *They* test every
part.

Really, we are professionals, building and shipping in volume. Our
field reliability is superb. We get awards. I don't think you have
standing to lecture us on this.



-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

On Fri, 15 Dec 2017 16:49:36 -0800 (PST), pcdhobbs@gmail.com wrote:

>>> Buy from authorized distributors. Real 74HC74s are so cheap, there's 
>>> no reason to buy from counterfeiters. Or to do receiving testing. 
>� 
>>Of course, we only buy from authorized distributors. No ebay or surplus 
>houses. 
>
>*cough* *splutter* You had to say that when I had a mouth full of coffee. 

Unlikely. This time of day, it would be gin and tonic.


-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com