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'[EE] Board Manufacturing'
2005\10\15@100502 by Mauricio Jancic

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Hi,
       I have a board assembler guy that assembles some of my boards.
Actually, I don't do that too much, I'm mostly in developing systems, but
I'm starting to build and sell some stuff.

       Anyway, the problem I have, is that this guy is telling me that it's
better for him to have the component distribution of the board in a way such
that the PTH components are in the opposite side of the SMD components, so
he can place all the components and pass the board only one time trough the
wave soldered.

       I find that correct I think, he can assembly the board if it is
arranged some other way, but I find that its not quite right and I'd prefer
to have all my components on the same side, specially on some boards.

       What is the normal procedure for assembling boards? Do you guy just
put the components where you need them or you try to think how to simplify
assembly to lower the costs? (the components where you need them, but off
course always with no constraint violations).

       Well... That's about it. Any comments?


Mauricio Jancic
Janso Desarrollos - Microchip Consultants Program Member
spam_OUTinfoTakeThisOuTspamjanso.com.ar
http://www.janso.com.ar
(54) 11 - 4542 - 3519

2005\10\15@123252 by Ruben Jönsson

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>        What is the normal procedure for assembling boards? Do you guy just
> put the components where you need them or you try to think how to simplify
> assembly to lower the costs? (the components where you need them, but off
> course always with no constraint violations).
>
>        Well... That's about it. Any comments?
>
Hi,

Yes, I always try to put SMD components on the bottom side and through hole components on the top side. If I have to put a component, like a LED for example, on the top side I choose a trough hole instead of SMD to keep assembly cost down - SMD on one side only.

Regards / Ruben



==============================
Ruben Jönsson
AB Liros Electronic
Box 9124, 200 39 Malmö, Sweden
TEL INT +46 40142078
FAX INT +46 40947388
.....rubenKILLspamspam@spam@pp.sbbs.se
==============================

2005\10\15@150333 by Tim N9PUZ

picon face
Mauricio Jancic wrote:

>        Anyway, the problem I have, is that this guy is telling me that it's
> better for him to have the component distribution of the board in a way such
> that the PTH components are in the opposite side of the SMD components, so
> he can place all the components and pass the board only one time trough the
> wave soldered.

>        I find that correct I think, he can assembly the board if it is
> arranged some other way, but I find that its not quite right and I'd prefer
> to have all my components on the same side, specially on some boards.

>        What is the normal procedure for assembling boards? Do you guy just
> put the components where you need them or you try to think how to simplify
> assembly to lower the costs? (the components where you need them, but off
> course always with no constraint violations).

In terms of the cost of manufacturing you certainly want to have as
few passes through the equipment as possible. Even on a boart with PTH
and SMT components I always tried to keep all the parts on the same
side of the board.

The assembler where I used to work would use high temperature solder
paste and would place the SMT parts first and run the board through
the reflow oven. The the PTH parts would be either hand placed or done
with an axial insertion machine and then run through the wave solder
system.

Tim

2005\10\15@152112 by Jose Da Silva

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On October 15, 2005 07:04 am, Mauricio Jancic wrote:
{Quote hidden}

Your Board assembler guy is correct.
That is the normal way of doing it so that you only do 1 pass.
Depending on how professional the finished product is, you may want to
follow his advice, however, I have worked with a couple of amateurs
that made a mess of things and would probably recommend to you to
continue doing as you do now (SMT on top).
The normal procedure is that those components get glued to the board, so
that when they pass through the reflow machine, they won't get lost
while upside down. If your board guy is a bit amateur, you may end up
with SMT parts that aren't flat against the board, and some parts
cracked as well. If your board guy is fairly competant and provides a
nice finished product, then take his advice and put the components on
the bottom.  My suggestion is to ask him to show you a couple of
finished boards using the recommended way he suggests, then you can
decide to take his recommendation, or do without it and pay the extra
cost of sending boards through more processes just for the results of
better finish.

Cheers!

2005\10\15@161725 by Roland

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Well, I visited an assembly house on friday for my first auto place job, and was told, if possible, to keep all componenets on one side only. I have a mix of smd on top and bottom, and leaded on top, like I see on many boards.
But, if you keep all smd on one side, then they only need to stencil the solder paste once, and possibly also reduce the stencil cost. Also, if you keep all smd on the top, then there's no need for the glue on the underneath to stop components falling off during the reflow.

It's best to visit the guys first before you lay the board, to see what equipment they have, and their recommendations. No need to fight with them afterwards. Also check what size pads they require for various packages.

regards
Roland




At 06:32 PM 15/10/2005 +0200, you wrote:
{Quote hidden}

>

2005\10\15@164342 by Bob Axtell

face picon face
Right, always visit the assembly house so you can understand their process.

The automated placement of SMD components is a ONE-SIDE process for most assemblers. THis is because the stencil process is a one-side process, using gravity to keep the devices in place.

People who have components on both sides have the second side assembled by hand. Few shops can reliably mount SMD components automatically on both sides, and ever fewer are located inside the USA.

I always mount SMD on top side, then install bottom SMD manually, finally top or bottom sided thru-connectors manually, I have almost NO confidence in SMD conectors.

--Bob

Roland wrote:

{Quote hidden}

>>-

2005\10\15@221247 by Jose Da Silva

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On October 15, 2005 01:43 pm, Bob Axtell wrote:
> People who have components on both sides have the second side
> assembled by hand. Few shops can reliably mount SMD components
> automatically on both sides, and ever fewer are located inside the
> USA.

The smaller the component, the fewer assembly houses that can handle it
too. If you can go with 1206 smd, you are able to use more board houses
than if you go smd 603. Likewise, the smaller the part. Some part
placement machines will drop those tiny grain of sand sized parts, so
you will probably need more (spare) parts to stuff a board.

> I always mount SMD on top side, then install bottom SMD manually,
> finally top or bottom sided thru-connectors manually, I have almost
> NO confidence in SMD conectors.

You shouldn't have confidence in them.
You are basically relying on a blob of solder to hold the component in
place, which tends to go brittle as it is repeatedly stressed during
time... add to that, you are relying on the copper pad to stay firmly
in place, and that is not trustworthy enough considering you sometimes
need a lot of heat to remove connectors (pad can become semi-unglued
during heating).  Thru-hole is the only reliable way to go if you plan
on long-life connectors.

2005\10\16@005112 by Xiaofan Chen

face picon face
Yes it all depends on the assmebly house. For us, we have in-house
SMD pick and place machines and reflow soldering and wave soldering
machines. But we do not have automatic placement machine for
PTH components since manual insertion is still cheaper.

It is good to have less process on the SMD reflow if possible. For us, two
side reflow is esitmated to be 10% more expensive than single side
reflow.

It is good to have all the SMD components on the same side as the PTH
components if wave soldering is involved. If the SMD components are on the
opposite side of the PTH components (thus on the same side as the
leads of the through-hole components), then an extra glue process are
required since it needs to withstand the wave soldering. The SMD pads which
need to be glued and go through wave soldering process will generally be
bigger than the reflow pads so it will take more space.

Therefore if the PTH components count are not high, we normally use two
side reflow and use manual soldering for the PTH components.

SMD connectors can be difficult to deal with so we normally have
mechanical design features to protect them from being lift up.

Regards,
Xiaofan

On 10/16/05, Bob Axtell <EraseMEengineerspam_OUTspamTakeThisOuTcotse.net> wrote:
{Quote hidden}

2005\10\17@022703 by Vitaliy

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A very interesting discussion!

Xiaofan, when you say

> [...] we do not have automatic placement machine for
> PTH components since manual insertion is still cheaper.

I assume you're talking about a Chinese factory? Is an automatic placement
machine more expensive because of high operating costs, or do you mean that
in the sense that it requires a substantial initial investment?

If I remember correctly, on my visit to our contract manufacturer I was told
that their state-of-the-art pick-and-place SMT and PTH machines were $300k
apiece. Perhaps what you said would only apply to (relatively) small
factories, which are unable to use the machine to its full capacity?

We just sent the Gerbers for our latest product to the board house on
Friday. This particular PCB has SMT on both sides, with PTH LEDs, IC socket,
and sub-D connectors on the top. Although initially we were able to jam-pack
the parts on one side, the resulting number of vias was ridiculous - IIRC,
x3 or more compared to the two-sided approach.

So here's a question for people with more experience: is it better
(cost-/performance-wise) to have SMT parts on both sides, or have three
times as many vias?

Best regards,

Vitaliy

{Original Message removed}

2005\10\17@031639 by Chen Xiao Fan

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I am now in Singapore. Singapore is in Southeast Asia and the majority
of the population are Chinese but there are quite some Malay and
Indian as well.

We are doing mass production but not in the sense of mass production
in the consumer electronics. Most of our product have annual quantity
of 1k to 20k with very few product above 50kpcs per year. I am told
by the SMD/PTH department that a PTH machine is not worth the initial
investment since majority of components are SMD parts here and the
direction is going to smaller and smaller parts. We have more than 600
people in Singapore and another 300 people in a nearby subsidy
in Bintan Island, Indonesia. It is quite expensive to do manual insertion
and soldering in Singapore (of course still cheaper than in the
headquarter in Mannheim, Germany). But in Bintan (similar to China in the
aspect of cost but without the high quality work force but it is
only one hour to Singapore), the price is quite cheap.

We have quite some SMD machines though and they are not cheap especially
when the accuracy of placement is high. Most of them are Siemens Siplace
machines. They are really quite expensive. We do not have Computerized
Vision Inspections system either. Therefore we are doing manual visual
check (with microscopes) of the quality of SMD reflow soldering.

The number of vias may affect the PCB price. This is especially true when
the size of the vias is quite small. So you need to do some calculations.

However PCB price are generally more depending on the quantity and
tolerance and the number of milling and V-cut than the number of vias.
PCB price negotiation is quite difficult when the quantity is low.
We try to procure PCBs from mainland China. However, those with good
quality does not accept our order quantity and price. Those accepting
our order quantity/price does not meet our quality requirement. ;-(

Regards,
Xiaofan

----------------------------------------------
Xiaofan Chen
R&D Engineer, Photoelectric Sensor Development
Pepperl+Fuchs Singapore
http://www.pepperl-fuchs.com
Signals for the world of automation
--------------------------------------------

{Original Message removed}

2005\10\17@052358 by Vitaliy

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face
Hello Xiaofan,

>I am now in Singapore. Singapore is in Southeast Asia and the majority
> of the population are Chinese but there are quite some Malay and
> Indian as well.

Sorry, I guess I could have found that out from your signature in one of
your previous posts.. yes, I know a little bit about Singapore - we have a
distributore there, and it's a popular example in books on Economics and
International Business. The first things that come to mind are exports
exceeding GNP by something like 40%, high-tech economy, very high per capita
GNP, and Singapore's ingenious solution to traffic jams. The traffic jam
solution is my favorite, I cite it every time someone complains that we
don't have enough freeways in Phoenix. Unfortunately, free rider mentality
prevails, but that's a topic for another discussion. ;)

> We are doing mass production but not in the sense of mass production
> in the consumer electronics. Most of our product have annual quantity
> of 1k to 20k with very few product above 50kpcs per year. I am told
> by the SMD/PTH department that a PTH machine is not worth the initial
> investment since majority of components are SMD parts here and the
> direction is going to smaller and smaller parts.

Very wise. As complexity of our products continues to increase, PTH becomes
uneconomical. And since SMT is not as labor-intensive, competitive advantage
of Chinese manufacturers is greatly diminished. We're actually considering
moving production back to the States - lead times are shorter, and quality
is better.

> We have more than 600
> people in Singapore and another 300 people in a nearby subsidy
> in Bintan Island, Indonesia. It is quite expensive to do manual insertion
> and soldering in Singapore (of course still cheaper than in the
> headquarter in Mannheim, Germany). But in Bintan (similar to China in the
> aspect of cost but without the high quality work force but it is
> only one hour to Singapore), the price is quite cheap.

May I ask what would be an average worker's salary in Bintan and Singapore?
Our Chinese contract manufacturer said their engineers' and workers'
salaries are $500 and $100/month, respectively. Not sure if that's typical,
though.

> We have quite some SMD machines though and they are not cheap especially
> when the accuracy of placement is high. Most of them are Siemens Siplace
> machines. They are really quite expensive.

I can imagine!

> We do not have Computerized
> Vision Inspections system either. Therefore we are doing manual visual
> check (with microscopes) of the quality of SMD reflow soldering.

The manufacturer I mentioned in my previous message does have such a system,
and it's pretty cool to watch it in operation. :) Of course, it makes
sense - you are building small quantities of many different (and I assume,
frequently changing) devices, rather than vast quantities of the same
product. It takes time to "learn" a new circuit board.

> The number of vias may affect the PCB price. This is especially true when
> the size of the vias is quite small. So you need to do some calculations.

I realize that the answer to my original question depends on several
factors, and the best way to know for sure is to ask the manufacturer.
However, I was hoping that someone has developed a rule of thumb for
deciding whether to have lots of vias, or place SMT parts on both sides of
the boards. As far as I understand, one has to know the difference in costs
of:

1. Applying the solder paste to the second side, and running the board
through the reflow oven a second time, and
2. Number of extra vias multiplied by the cost per via.

If there aren't many extra vias, it is obviously cheaper to have parts on
one layer - since the the costs of applying the paste and running the board
through the oven remain constant, regardless of the number of components per
side.

> However PCB price are generally more depending on the quantity and
> tolerance and the number of milling and V-cut than the number of vias.
> PCB price negotiation is quite difficult when the quantity is low.
> We try to procure PCBs from mainland China. However, those with good
> quality does not accept our order quantity and price. Those accepting
> our order quantity/price does not meet our quality requirement. ;-(

You can console yourself with the thought that your direct competitors are
in the same boat. ;-)

Best regards,

Vitaliy



> {Original Message removed}

2005\10\17@062120 by Vasile Surducan

face picon face
On 10/15/05, Jose Da Silva <Digitalspamspam_OUTjoescat.com> wrote:
{Quote hidden}

Very interesting. You probably never seen then a PCB with SMT on bot
top and bottom (PTH one one side). And they are complete on the bottom
side, no dropped parts. A glue it's a glue not a joke ! The wrong
soldering profile will kill some parts and not the fact it's o the top
or on the bottom. On SMT depends how you're looking to the board.
"Top" and "bottom" are just words.
:)

cheers,
Vasile

2005\10\17@064815 by Alan B. Pearce

face picon face
>But in Bintan (similar to China in the aspect of cost
>but without the high quality work force but it is
>only one hour to Singapore), the price is quite cheap.

I had an Akai video recorder that was made in Indonesia for the UK market.
It used single sided boards with some SMD components (resistors and ICs),
but all the electrolytics, inductors, connectors, and the whole mains Power
Supply was done in PTH components, along with "millions" of jumper wires, so
they did not need to do double sided PCBs. This meant that they could use a
phenolic material which can be punched instead of fibreglass which they
would need to drill for PTH double sided.

2005\10\17@065336 by Alan B. Pearce

face picon face
{Quote hidden}

I guess it depends on what sort of reflow oven is used - even with parts on
both sides, it may still be possible to do a single pass through the oven -
especially if there are no PTH parts.

See my previous post on the video recorder. I suspect that the jumper wires
are auto inserted by a machine that cuts and bends the wire as it is
inserted, rather than hand fit them.

2005\10\17@084845 by Xiaofan Chen

face picon face
I think quite some time ago we have a formula. I am not so sure whether
it is still true or not. The German may need to work 40 hours later so
that the cost rate will be similan to an American.

In terms of cost per hour:
1 Geman = 1.5 American = 2 Singaporean = 2~3 Huangarian = 10~16
Indonesian. This is not the salary ratio but the overall cost rate (including
the administrative overhead).

The salary in mainlan China varies a lot across different region. In the
big cities like Shanghai/Beijiang/Guangzhou, the GDP per captia is about
US$5000. In the west of the country, the GDP per capita can be as low
as US$600. The national GDP per capita is about US$1200. So the
salary of US$500/US$100 per month is quite typical in cities other
than those very rich areas. In the Zhujiang Delta area near to HongKong,
the wages of the migrant workders do not really incrrease much in
the past 10 years and the working conditions are not so good as well.
Therefore some of them start to face the problem of labor shortages.
It is strange but it is true.

In terms of electronics component cost, it is actually not really
cheaper in China if your quantity is not high enough. For examples,
PICs are generally more expensive in China. However plastic parts
are much cheaper in China because of the vast number of plastic
mould/parts makers.

Regards,
Xiaofan

On 10/17/05, Vitaliy <@spam@spamKILLspamspammaksimov.org> wrote:
{Quote hidden}

2005\10\17@090717 by Vitaliy

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Hi Alan,

> I guess it depends on what sort of reflow oven is used - even with parts
on
> both sides, it may still be possible to do a single pass through the
> oven -
> especially if there are no PTH parts.

Yes, I understand that it is possible to do it in a single pass - but as
someone pointed out manufacturers often rely on gravity to hold the
components in place. So they apply the solder paste and place the components
on one side, run the board through the oven, flip it over, and repeat the
process.

Of course, if they were to glue the components to the "bottom", they could
solder them in a single pass. However, what's more expensive - gluing the
parts to the PCB (which I assume involves waiting for the glue to take), or
doing a second pass through the oven?

> See my previous post on the video recorder. I suspect that the jumper
> wires
> are auto inserted by a machine that cuts and bends the wire as it is
> inserted, rather than hand fit them.

Unfortunately, I don't think that would be an option for a high-density PCB.
It is an interesting solution, though - I too recall seeing such PCBs in old
VCRs. IIRC, they had no soldermask, and the black silkscreen was applied
directly to the light-colored PCB. I think the reason they were able to get
away with a single-sided board was the low part count to PCB area ratio.

Best regards,

Vitaliy

2005\10\17@092726 by alan smith

picon face
And thats why I get big sighs when I use 0201 size parts.....

Jose Da Silva <KILLspamDigitalKILLspamspamJoesCat.com> wrote:On October 15, 2005 01:43 pm, Bob Axtell wrote:
> People who have components on both sides have the second side
> assembled by hand. Few shops can reliably mount SMD components
> automatically on both sides, and ever fewer are located inside the
> USA.

The smaller the component, the fewer assembly houses that can handle it
too. If you can go with 1206 smd, you are able to use more board houses
than if you go smd 603. Likewise, the smaller the part. Some part
placement machines will drop those tiny grain of sand sized parts, so
you will probably need more (spare) parts to stuff a board.

> I always mount SMD on top side, then install bottom SMD manually,
> finally top or bottom sided thru-connectors manually, I have almost
> NO confidence in SMD conectors.

You shouldn't have confidence in them.
You are basically relying on a blob of solder to hold the component in
place, which tends to go brittle as it is repeatedly stressed during
time... add to that, you are relying on the copper pad to stay firmly
in place, and that is not trustworthy enough considering you sometimes
need a lot of heat to remove connectors (pad can become semi-unglued
during heating). Thru-hole is the only reliable way to go if you plan
on long-life connectors.

2005\10\17@093106 by Alan B. Pearce

face picon face
>It is an interesting solution, though - I too recall
>seeing such PCBs in old VCRs. IIRC, they had no soldermask,
>and the black silkscreen was applied directly to the
>light-colored PCB. I think the reason they were able
>to get away with a single-sided board was the low part
>count to PCB area ratio.

The parts to board area is probably a significant part of it, but I suspect
that the labour content is as well. The boards in this particular machine do
have solder mask on the copper side, plus silkscreen on both sides.

But the impression I get is that the single sided PCB, with wire links, is
used because it is so much faster to make for a mass produced product,
because the PCB "drilling" and outline is done in one 10 second punch
operation, rather than the drill one hole at a time operation that is used
for fibreglass boards. The cost of putting in the links is small compared to
the increased time costs of processing fibreglass boards.

2005\10\17@094253 by Alan B. Pearce

face picon face
>And thats why I get big sighs when I use 0201 size parts.....

And there are smaller ones than that ;)

I have heard of 01005 parts (if that is the nomenclature they use).

2005\10\17@102619 by Xiaofan Chen

face picon face
Yes it is called 01005. Luckily we do not need to use them yet.
0201 are used here but not so common. 0402/0603/0805 is the
norm here. 0402 is already not so easy to deal with when
doing the troubleshooting but it still much better than troubleshooting
the QFN parts.

SMD chip resistor datasheet example:
http://industrial.panasonic.com/www-data/pdf/AOA0000/AOA0000CE1.pdf

Regards,
Xiaofan

On 10/17/05, Alan B. Pearce <RemoveMEA.B.PearceTakeThisOuTspamrl.ac.uk> wrote:
> >And thats why I get big sighs when I use 0201 size parts.....
>
> And there are smaller ones than that ;)
>
> I have heard of 01005 parts (if that is the nomenclature they use).
> -

2005\10\17@103152 by Vitaliy

flavicon
face
> The parts to board area is probably a significant part of it, but I
> suspect
> that the labour content is as well.

Yes, I agree that the labor content is the reason why they used single
boards and wire jumpers, but my point is that this approach doesn't work
with high-density boards. There's simply no room for the jumpers if you put
all of the components on one side (I'm thinking about our latest prototype).

Since a VCR PCB can be quite large due to the physical size of the device,
and the parts are few, they can place them all on one layer and have plenty
of room left for the jumpers.

>The boards in this particular machine do
> have solder mask on the copper side, plus silkscreen on both sides.

I should have said "no solder mask on the component side." Of course, the
copper side had solder mask. And, come to think of it, "normal" single-sided
PCBs don't have solder mask on the top side. But it's late (or is it
early?), and I was thinking of the Advanced Circuits prototypes of our
single-sided boards, which had solder mask on both sides (AFAIR, it's
impossible not to have soldermask on the top layer when you order from
4pcb.com).

> But the impression I get is that the single sided PCB, with wire links, is
> used because it is so much faster to make for a mass produced product,
> because the PCB "drilling" and outline is done in one 10 second punch
> operation, rather than the drill one hole at a time operation that is used
> for fibreglass boards. The cost of putting in the links is small compared
> to
> the increased time costs of processing fibreglass boards.

Makes sense.

Best regards,

Vitaliy

2005\10\17@103437 by Xiaofan Chen

face picon face
Most of the cheaper DVD players or VCRs have PTH based power supply since those
power supply are mostly from no-name assembly houses. It is cheaper for them
to use PTH and  single side board. They often use FR2/FR1 board instead of FR4
to get cheaper PCBs.

Layout is a nightmare when using single side board and I think normally not
many people will like to use single-side board. However it is quite common
in the field of consumer electronics product.

SMD electrolytics/inductors/connectors are often more expensive than discretes.

Regards,
Xiaofan

On 10/17/05, Alan B. Pearce <spamBeGoneA.B.PearcespamBeGonespamrl.ac.uk> wrote:
{Quote hidden}

2005\10\17@105640 by alan smith

picon face
I think there are several factors involved.  If you are routing high speed GHz signals, then you want to worry about signal integrity more than anything, and via's affect that.  If you are worried about cost, weigh in over the cost of more holes vs mfg cost of double sided placement.

Generally speaking, if you can do a board in one technology or the other, thats the cheapest way but I'm starting to see more and more IC's that are SMD only.

In the last 4 years, I haven't done a high volume board that doesnt have smd on both sides.

For small run consulting projects, its been more the rule to try and place all components on one side.

>So here's a question for people with more experience: is it better
>(cost-/performance-wise) to have SMT parts on both sides, or have three
>times as many vias?



               
---------------------------------
Yahoo! Music Unlimited - Access over 1 million songs. Try it free.

2005\10\17@110220 by William Chops Westfield

face picon face
>> Your Board assembler guy is correct.
>> That is the normal way of doing it so that you only do 1 pass.
>>
This is all going to be dependent on whether your assembler does
SMT via reflow or via wave soldering, right?  If they're doing
wave soldering, they can do one solder pass if the SMT is on the
bottom side (WRT through-hole components), but they need the extra
step of gluing the SMT components on.  If they do reflow for SMT
and wave for TH, they have two soldering steps but don't need the
glue step.  (You can't do TH via reflow, can you?)  So it seems to
me that it all depends on whether they bought the glue machine or
the reflow oven?  I'd think the reflow oven would be cheaper...

If you have SMT on both sides, do you always need to glue the
components on one of the sides?  Or will they stay on OK in a
reflow oven if you flip the board over to do the other side (if
they were soldered on in a separate pass.)

No experience here; just trying to apply logic...

BillW

2005\10\17@203138 by Chen Xiao Fan

face
flavicon
face
If it is two-side reflow, gluing is not necessary.

Only for wave soldering, we need to glue the components
on one side. Some of our SMT pick and place machines can
dispense glue as well but some can not.

Because of the following reasons and board space constraint,
we normally favor manual soldering over wave soldering when
the number of discrete components are less than 10, which is
normally the case for our sensor products (Factory Automation
Division). In the interface card products (Process Automation
Division), we often use wave soldering because of the number
of discrete components involved.
1) Gluing is an extra process and it adds to the cost and
affect the throughput of the SMT line.
2) Pads for wave soldering are bigger than reflow soldering.

Regards,
Xiaofan

----------------------------------------------
Xiaofan Chen
R&D Engineer, Photoelectric Sensor Development
Pepperl+Fuchs Singapore
http://www.pepperl-fuchs.com
Signals for the world of automation
--------------------------------------------

-----Original Message-----
From: William "Chops" Westfield
Sent: Monday, October 17, 2005 11:02 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Board Manufacturing
...
If you have SMT on both sides, do you always need to glue the
components on one of the sides?  Or will they stay on OK in a
reflow oven if you flip the board over to do the other side (if
they were soldered on in a separate pass.)

No experience here; just trying to apply logic...

BillW

2005\10\17@203805 by Chen Xiao Fan

face
flavicon
face
By the way, I was told five years ago that 1206/0805 components
(especially resistors) will be obsolete. However it seems they
are still alive now even though the majority of the components
on our boards are now 0402 resistors and 0603 capacitors and
SOT23/SOT323 transistors. We still use large number of metal
film resistors for safety related application (0207/0204).

Regards,
Xiaofan

{Original Message removed}

2005\10\18@010054 by Jose Da Silva

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On October 17, 2005 03:21 am, Vasile Surducan wrote:
{Quote hidden}

Actually, yes, I have. Plus I have also repaired them and have also set
up automated test equipment such as the hp3060, 3065 or hp3070 to test
them too.  ;-)
... and to keep-you on your toes, I also used to keep in contact with
one of the panasonic smt machine sales people on the west coast who
basically pointed-out NA is about 10 years behind Japan and Asia when
it comes to placement machines.  ;-)

The previous info was about right for north american standards. If you
were to design a board using smd, you should plan on big parts like
1206 this way you tend to get the best chance of anyone/everyone being
able to stuff boards for you, whether it is multimillion dollar
operations using the latest equipment or little 1 man operations
running 10 to 20 year old equipment. The smaller the part, the fewer
board houses capable of dealing with you. Not everyone can do smd on
the bottom without making a mess sometimes.

> And they are complete on the
> bottom side, no dropped parts. A glue it's a glue not a joke !

Sorry, but disagree, because that sounds like you work in a place that
has no less than 100 workers on the manufacturing floor and does a
respectable amount of manufacturing.
Try some of the fly-by-night seat-of-the-pants, promise you everything
companys.
Make sure you use interesting parts, like glass barrel shaped smd
diodes. They will probably start by gluing glass down and then sending
them thru a reflow machine, but by the end will be hand-soldering those
little suckers in place  ;-)

> The
> wrong soldering profile will kill some parts and not the fact it's o
> the top or on the bottom.

That is a given fact of manufacturing and only one of the issues you
have to take into account. When you start dealing with the nitty-gritty
of manufacturing, you got to take even little issues to mind, for
example, if ceramic parts are placed too close to the edges of big
boards, they break due to flexing while processing, handling, and
testing etc. If you must place ceramic parts close to the edges, try to
run them parallel with the edges and not 90deg to the edge, to reduce
flexing and breakage.

> On SMT depends how you're looking to the
> board. "Top" and "bottom" are just words.

Only on the design software and the electricity flowing through them
since gravity, processing, handling, testing, affects neither.  :-)
Manufacturing is different.
Top mounted is usually stencils and solder paste since gravity holds
parts in place. Bottom mount depends on how many THP and SMD you are
working with. You are also unlikely to find BGA parts on the bottom
too.

cheers ;-)

2005\10\18@073302 by olin piclist

face picon face
Jose Da Silva wrote:
> ... and to keep-you on your toes, I also used to keep in contact with
> one of the panasonic smt machine sales people on the west coast who
> basically pointed-out NA is about 10 years behind Japan and Asia when
> it comes to placement machines.  ;-)

And the fact that his job is to get people to buy new equipment in NA has
nothing to do with that, of course.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\10\18@121435 by Jose Da Silva

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On October 17, 2005 08:02 am, William Chops Westfield wrote:
> >> Your Board assembler guy is correct.
> >> That is the normal way of doing it so that you only do 1 pass.
>
> This is all going to be dependent on whether your assembler does
> SMT via reflow or via wave soldering, right?

Right.
If there are a lot of THP, then it is most likely they will want to run
that board through a wave solder machine. This means that they may have
to tape the SMD pads (to protect from wave solder process = expensive
labour) so that they can solder them in later or that they are going to
glue the part on the board and have the wave solder process solder the
part in.
If THPs are few enough to do by hand, then the bottom layer really
depends on "how capable" your assembly guy is able to deal with the
challenge.  Some can. Some can't.


> If they're doing
> wave soldering, they can do one solder pass if the SMT is on the
> bottom side (WRT through-hole components), but they need the extra
> step of gluing the SMT components on.  If they do reflow for SMT
> and wave for TH, they have two soldering steps but don't need the
> glue step.  (You can't do TH via reflow, can you?)  So it seems to
> me that it all depends on whether they bought the glue machine or
> the reflow oven?  I'd think the reflow oven would be cheaper...

Think about what you said here.
You got THPs here. They tend to be bulkier and require a bit more heat
to get the solder to stick between the board and the part... especially
if we speak of connectors.  Now, think about the surface mount stuff on
the bottom. If you don't have glue holding the part in place, what is
going to happen to those tiny little parts when a big wave of solder
washes across them and the solder joints holding them in place?
;-)

> If you have SMT on both sides, do you always need to glue the
> components on one of the sides?  Or will they stay on OK in a
> reflow oven if you flip the board over to do the other side (if
> they were soldered on in a separate pass.)

If you have THPs and want to solder both at same time, then glue, yes.
If you are only working with SMD, you can play with temperature profiles
by having the bottom side cool while the top side is hot (relative to
the solder melting point).

> No experience here; just trying to apply logic...

No problem.
You would find it interesting to walk thru a decent sized operation.
Contract board houses would probably hold the biggest variety of "how
to do something" if you never saw manufacturing before compared to
board houses which may deal with just one or a couple of  products.

Cheers!

2005\10\18@123415 by Jose Da Silva

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On October 18, 2005 04:33 am, Olin Lathrop wrote:
> Jose Da Silva wrote:
> > ... and to keep-you on your toes, I also used to keep in contact
> > with one of the panasonic smt machine sales people on the west
> > coast who basically pointed-out NA is about 10 years behind Japan
> > and Asia when it comes to placement machines.  ;-)
>
> And the fact that his job is to get people to buy new equipment in NA
> has nothing to do with that, of course.

hehehe, good point, but actually, I worked at 2 different places at the
time he worked in those places as well, so you don't tend to put your
"sales face" on 24x7 at that point, and details like this do come out.

...besides, his info corellated with info I got from other asians from
Tiawan, mainland china and Hong Kong that didn't even know him.
...maybe they exchanged info with each other, pretended not to know each
other, and tell/feed us this mis-information as part of some master
plan to take over manufacturing  ;-P

Cheers!

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