How to manage composite parts

Marco Trapanese wrote on Sun, 17 March 2013 03:26

Hello,

 

sometime I have a part composed of multiple components.

Some examples:

 

- battery holder: two clips

- MCU module: two or more connectors

 

 

In the schematic is correct to have one symbol for the whole part. It

makes no sense to place two different clips (which must be placed at an

 

exact distance with the correct silkscreen info) o two different

connectors for the MCU module.

 

The downside is it's hard to manage and maintain the BOM because I will

 

get only one item rather than 2 or more. And the manufacturer code

isn't

really applied to the whole part but to the single sub-items.

 

I wonder how you would handle this.

Thank you

Marco

The following may help you to work out an approach.

For this I think the attached image of a PCB fuse with separate PCB mounted

clips is a good reference example.

The schematic requires a fuse symbol with a value for the fuse

The BOM  requires

2 x clips

1 x fuse

The assembler needs placement instructions for all the sub parts of the

schematic's 'fuse' symbol.

1 x clip loc = X1Y1 rotation = 0

1 x clip loc = X2Y2 rotation = 180

1 x fuse loc....etc etc

The sub parts have to be separate to be included in the part placement

file.

Eagle has the GATE feature but that makes for many sub-parts on the

schematic and one part on the board so that won't do here. We need to get

at least the two clips onto the board separately and ideally the fuse as

well as an element with no pads.

So three separate parts means three separate items on the schematic so the

BOM ULP can detect them as separates. The schematic representation is thus

a composite of the needed sub-parts.

The pain is that you need to move them around as a group.

The clips here need to be different devices because they have different

packages for our purpose. The left clip, say, has the pads for part but

also placement guides, on a custom layer,  for the other clip. This right

clip has the same rotation as the left clip, in the library, so that the

assembler is not driven mad. You add the 180 degrees rotation as you add it

to the board.

The right clip only has pads for itself but use its origin to land on the

marker of the left pad. Alternately the left pad has both pads and the

right clip is only documentation or tPlace layer outlines. Accurate

placement and rotation is still required for the assembler.

The fuse element on the board is no more than documentation or tPlace

layers but it is placed accurately so you can recover its coordinates for

the assembler as it may be placed by machine.

So all the needs can be met with only the schematic grouping not as nice as

we would desire.

HTH

Warren

--

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Attachments:

Il 17/03/2013 03:10, Warren Brayshaw ha scritto:

The following may help you to work out an approach.

For this I think the attached image of a PCB fuse with separate PCB mounted

clips is a good reference example.

 

The schematic requires a fuse symbol with a value for the fuse

 

The BOM  requires

2 x clips

1 x fuse

Great!

The assembler needs placement instructions for all the sub parts of the

schematic's 'fuse' symbol.

1 x clip loc = X1Y1 rotation = 0

1 x clip loc = X2Y2 rotation = 180

1 x fuse loc....etc etc

 

The sub parts have to be separate to be included in the part placement

file.

Exactly.

Eagle has the GATE feature but that makes for many sub-parts on the

schematic and one part on the board so that won't do here. We need to get

at least the two clips onto the board separately and ideally the fuse as

well as an element with no pads.

 

So three separate parts means three separate items on the schematic so the

BOM ULP can detect them as separates. The schematic representation is thus

a composite of the needed sub-parts.

The pain is that you need to move them around as a group.

It is small pain in the schematic. I'm afraid how to hold in position

the parts in the layout.

The clips here need to be different devices because they have different

packages for our purpose. The left clip, say, has the pads for part but

also placement guides, on a custom layer,  for the other clip. This right

clip has the same rotation as the left clip, in the library, so that the

assembler is not driven mad. You add the 180 degrees rotation as you add it

to the board.

 

The right clip only has pads for itself but use its origin to land on the

marker of the left pad. Alternately the left pad has both pads and the

right clip is only documentation or tPlace layer outlines. Accurate

placement and rotation is still required for the assembler.

 

The fuse element on the board is no more than documentation or tPlace

layers but it is placed accurately so you can recover its coordinates for

the assembler as it may be placed by machine.

 

So all the needs can be met with only the schematic grouping not as nice as

we would desire.

If I understand correctly you're suggesting to:

1) create three parts: left clip, right clip fuse

2) draw the package of, say, left clip with some marker to place the

other parts

3) in the layout, position the right clip and the fuses on their marks

(this is what I was trying to avoid)

4) in the schematic, group and move around the three parts.

Not very handy but it's a good drawback.

Well, I ask you another bit of patience.

Please let's consider another example.

An MCU module with two connectors and four holes.

The best would be:

- in the schematic a single part with all the pins

- in the BOM the two connectors and the 4x mechanical stuff (screws,

nuts, etc...)

I would do the following:

- two parts: one for each connector. But only one with the usual

rectangular box around the pins. The other is composed of the pins only

at the right distance to be placed over the box already placed.

- the package should be created as described above, with the reference

marker to place the other connector. A simple but powerful feature I

wish is to define a group and store it. So I can move the group without

have to redefine it every time (every CAD has this option).

- I don't know how to represent the mechanical parts! Ok, I can just put

a note on an hidden layer and then manually compile the BOM.

It's a pity a great software like EAGLE can't manage this common problem

natively.

All electrical CADs can.

Marco

Il 17/03/2013 03:10, Warren Brayshaw ha scritto:

The following may help you to work out an approach.

For this I think the attached image of a PCB fuse with separate PCB mounted

clips is a good reference example.

 

The schematic requires a fuse symbol with a value for the fuse

 

The BOM  requires

2 x clips

1 x fuse

Great!

The assembler needs placement instructions for all the sub parts of the

schematic's 'fuse' symbol.

1 x clip loc = X1Y1 rotation = 0

1 x clip loc = X2Y2 rotation = 180

1 x fuse loc....etc etc

 

The sub parts have to be separate to be included in the part placement

file.

Exactly.

Eagle has the GATE feature but that makes for many sub-parts on the

schematic and one part on the board so that won't do here. We need to get

at least the two clips onto the board separately and ideally the fuse as

well as an element with no pads.

 

So three separate parts means three separate items on the schematic so the

BOM ULP can detect them as separates. The schematic representation is thus

a composite of the needed sub-parts.

The pain is that you need to move them around as a group.

It is small pain in the schematic. I'm afraid how to hold in position

the parts in the layout.

The clips here need to be different devices because they have different

packages for our purpose. The left clip, say, has the pads for part but

also placement guides, on a custom layer,  for the other clip. This right

clip has the same rotation as the left clip, in the library, so that the

assembler is not driven mad. You add the 180 degrees rotation as you add it

to the board.

 

The right clip only has pads for itself but use its origin to land on the

marker of the left pad. Alternately the left pad has both pads and the

right clip is only documentation or tPlace layer outlines. Accurate

placement and rotation is still required for the assembler.

 

The fuse element on the board is no more than documentation or tPlace

layers but it is placed accurately so you can recover its coordinates for

the assembler as it may be placed by machine.

 

So all the needs can be met with only the schematic grouping not as nice as

we would desire.

If I understand correctly you're suggesting to:

1) create three parts: left clip, right clip fuse

2) draw the package of, say, left clip with some marker to place the

other parts

3) in the layout, position the right clip and the fuses on their marks

(this is what I was trying to avoid)

4) in the schematic, group and move around the three parts.

Not very handy but it's a good drawback.

Well, I ask you another bit of patience.

Please let's consider another example.

An MCU module with two connectors and four holes.

The best would be:

- in the schematic a single part with all the pins

- in the BOM the two connectors and the 4x mechanical stuff (screws,

nuts, etc...)

I would do the following:

- two parts: one for each connector. But only one with the usual

rectangular box around the pins. The other is composed of the pins only

at the right distance to be placed over the box already placed.

- the package should be created as described above, with the reference

marker to place the other connector. A simple but powerful feature I

wish is to define a group and store it. So I can move the group without

have to redefine it every time (every CAD has this option).

- I don't know how to represent the mechanical parts! Ok, I can just put

a note on an hidden layer and then manually compile the BOM.

It's a pity a great software like EAGLE can't manage this common problem

natively.

All electrical CADs can.

Marco