Mounting an SMD connector on the Bottom layer?

Mike Wirth schrieb:

Hi folks, newbie with EagleCAD here.

 

Trying to build a simple one-sided PCB with the components on the top

and copper on the bottom, except for a surface-mount flat ribbon cable

connector, a Molex 52207-28xx, that will have to mount on the bottom.

 

I'm having lots of difficulties trying to accomplish this:

 

1. There's a similar connector in the con-molex.lbr library, a

52745-3090.  But I can't use it directly, because the lands on the top

layer (naturally and I can't figure out how to edit the package in

place to change them to the bottom.

 

2. Also when the connector is mounted on the bottom, the pin order is

reversed.  That has to be changed, too.

 

3. I finally bit the bullet and defined my own library with a new

package, "52207-28", device and symbol.  Copied the package from the

existing one, and now could move the lands to the bottom layer.  Defined

a new symbol with 28 pins, defined the device and connected the pins to

the lands.

 

So far, so good.

 

But now I got new problems:

 

A. I couldn't replace the existing device in the schematic with my new

one -- got an error message about not being able to map pin 1.

 

B. On the board, the new connector is half the size it should be. 

Sigh... (I'll go back and check the grid in the package definition.)

 

C. On the board, the new connector is rotated 90º from the definition. 

And I can't rotate it on the board -- I get a "You can't do that in the

EagleCAD light version".  (I've gotten that a lot of times when doing

device and package editing.)

 

Any hints on how to get around these specific problems, or in

accomplishing the general goal of flipping SMD components and mounting

them on the bottom?

 

TIA,

 

Mike Wirth

Palo Alto, CA

To bring a device from top to bottom use MIRROR. You can even group the

whole pcb and (all layers activated)flip over the complete thing.

There is no need to construct a new device just because you want to

mount it on the bottom side (you would have plenty work to do   ).

If one create new devices one usually checks the ref-packages library

for a suitable package, since those are the most difficult to design.

To design a new package get the datasheet of the device and set the grid

to the same measures and the alternate grid perhaps 10 times smaller.

Place the center of the body on the cross (you can do that later with

GROUP and MOVE), since this will be your orign later.

If you edit the symbol of a device do not change the grid of 0,1" since

all libraries use this value and the pins MUST stay in this grid. Use

the alternate grid to suit your drawing needs.

Do editing of devices in your own library, you may spoil the originals.

If you keep your own library open you can check existing libraries in

the control panel and with a right mouseclick copy the selected device

or package into your library for modification.

So one does not invent the wheel new but takes a suitable device and

modifies it.

For A and B I think it is a library design error.

For C:Try MOVE to pick the package and then use the right mousekey to

rotate the device by 90° every click and place it again with the left key.

General on a board you look at it from the top and "see through" the

layers. so if you mirror a device to the bottom side of the pcb you

actually see it's belly. Do that on a table with a DIL chip and put it

on it's back and notice the different position of the pins

--

Gruß / regards

Joern

Mike Wirth schrieb:

Hi folks, newbie with EagleCAD here.

 

Trying to build a simple one-sided PCB with the components on the top

and copper on the bottom, except for a surface-mount flat ribbon cable

connector, a Molex 52207-28xx, that will have to mount on the bottom.

 

I'm having lots of difficulties trying to accomplish this:

 

1. There's a similar connector in the con-molex.lbr library, a

52745-3090.  But I can't use it directly, because the lands on the top

layer (naturally and I can't figure out how to edit the package in

place to change them to the bottom.

 

2. Also when the connector is mounted on the bottom, the pin order is

reversed.  That has to be changed, too.

 

3. I finally bit the bullet and defined my own library with a new

package, "52207-28", device and symbol.  Copied the package from the

existing one, and now could move the lands to the bottom layer.  Defined

a new symbol with 28 pins, defined the device and connected the pins to

the lands.

 

So far, so good.

 

But now I got new problems:

 

A. I couldn't replace the existing device in the schematic with my new

one -- got an error message about not being able to map pin 1.

 

B. On the board, the new connector is half the size it should be. 

Sigh... (I'll go back and check the grid in the package definition.)

 

C. On the board, the new connector is rotated 90º from the definition. 

And I can't rotate it on the board -- I get a "You can't do that in the

EagleCAD light version".  (I've gotten that a lot of times when doing

device and package editing.)

 

Any hints on how to get around these specific problems, or in

accomplishing the general goal of flipping SMD components and mounting

them on the bottom?

 

TIA,

 

Mike Wirth

Palo Alto, CA

To bring a device from top to bottom use MIRROR. You can even group the

whole pcb and (all layers activated)flip over the complete thing.

There is no need to construct a new device just because you want to

mount it on the bottom side (you would have plenty work to do   ).

If one create new devices one usually checks the ref-packages library

for a suitable package, since those are the most difficult to design.

To design a new package get the datasheet of the device and set the grid

to the same measures and the alternate grid perhaps 10 times smaller.

Place the center of the body on the cross (you can do that later with

GROUP and MOVE), since this will be your orign later.

If you edit the symbol of a device do not change the grid of 0,1" since

all libraries use this value and the pins MUST stay in this grid. Use

the alternate grid to suit your drawing needs.

Do editing of devices in your own library, you may spoil the originals.

If you keep your own library open you can check existing libraries in

the control panel and with a right mouseclick copy the selected device

or package into your library for modification.

So one does not invent the wheel new but takes a suitable device and

modifies it.

For A and B I think it is a library design error.

For C:Try MOVE to pick the package and then use the right mousekey to

rotate the device by 90° every click and place it again with the left key.

General on a board you look at it from the top and "see through" the

layers. so if you mirror a device to the bottom side of the pcb you

actually see it's belly. Do that on a table with a DIL chip and put it

on it's back and notice the different position of the pins

--

Gruß / regards

Joern