PDIP-16 package in a PCB design

Thread Starter

Tesla86

Joined Oct 25, 2016
34
Dear colleagues,

I have to include an H-bridge in one of my PCB designs; this H-bridge presents a PDIP-16 package like the following one:

http://shannonstrutz.com/wp-content/uploads/2012/02/20-16-dip.jpg

My question is if you recommend me to use a socket like this:

http://techdelivers.com/40-pin-IC-base-socket-wide

or it is better to solder the chip directly on the PCB. One issue is that four of the 16 pins have to act as a heatsink, dissipating heat through a ground-plane with vias.

The IC I refer to is here:

http://www.ti.com/lit/ds/symlink/sn754410.pdf


Thanks in advance.
 

ericgibbs

Joined Jan 29, 2010
18,766
hi T86,
I have used that type of IC socket for many years without any problems.
Also for the price of socket compared to ruining an expensive PCB if a soldered in IC has to be replaced is the best option.

E
 

AlbertHall

Joined Jun 4, 2014
12,345
With the correct tools desoldering is not a problem.
Presumably if you are replacing the IC then damage to the IC doesn't matter and then, lacking good tools for desoldering multi-pin packages from plated through holes, I would cut all the pins close to the IC and then remove the pins individually. This method reliably preserves the board, and the plating through the holes.
 

jpanhalt

Joined Jan 18, 2008
11,087
I have used those sockets and they work, but I prefer sockets with machined pins like this:
upload_2016-11-22_6-58-58.png

For a commercial board, I agree with those who suggest not using a socket. The failure rate should be low, and if the IC is bad, removing it is quite easy. Now, if it is a pre-programmed memory that will need to be removed for updates, that is a different story.

John
 

Thread Starter

Tesla86

Joined Oct 25, 2016
34
Dear colleagues,

Regarding heat dissipation, my H-bridge drives currents up to 380mA (peaks), and each IC hadles with two lines, so maximum currents in each IC is around 760mA (for peaks). I'm not sure whether the use of a socket may give rise to a poor dissipation in this scenario...
 

ErnieM

Joined Apr 24, 2011
8,377
Since the device is using the ground pins as a thermal path to get heat out of the device you need to carefully evaluate how much thermal impeadance you are adding with a socket... or bite the bullet and install the thing directly, no socket.

Removing a DIP device is not very difficult as long as you do not mind sacrificing the part: just clip each lead from the body then extract each pin in turn. Solder suck or wick up and extra solder and insert the replacement.
 

AnalogKid

Joined Aug 1, 2013
10,986
IC pins are wide flat rectangles. Sockets that make contact with both wide flat surfaces (like AMP Diplomate) will move much more heat that sockets that make contact with the pin edges (like many machined contacts). If you don't know the internal construction of the machined pins, I'd go with the less expensive but known-better performing flat side contact. Also, even on a good day a socket moves less than 50% of the heat compared to direct soldered contact with a ground plane or other pc board radiating surface.

ak
 

mcgyvr

Joined Oct 15, 2009
5,394
A socket is used when easy (tool-less) replacement of the chip is needed/wanted..
If its not.. Don't use a socket..
Its added cost.. added thermal resistance,etc...
each and every "connection" is a resistor in a thermal model..

You need to determine if that added "thermal resistance" and cost,etc.. is acceptable for your needs based on many details not provided here..
 

Thread Starter

Tesla86

Joined Oct 25, 2016
34
hi T86,
I have used that type of IC socket for many years without any problems.
Also for the price of socket compared to ruining an expensive PCB if a soldered in IC has to be replaced is the best option.
E
Dear Ericgibbs,

I'm doing some test on this IC and I have a question. When disabling ENABLE pin (applying LOW level), my 12V-motor (connected to pin 3 and pin 6) doesn't rotate, which is normal. Is also normal that, when enabling (applying HIGH leve), the motor rotates as expected. The problem is that when DISCONNECTING ENABLE pin, I find also 12V between pin 3 and pin 6. Is this a normal behaviour?

In addition, I've realized that when disabling ENABLE (LOW voltage), voltage between pin 3 and pin 6 is around -60mV. Does it mean circuit is consuming power also when IC is disabled?

Thanks in advance.
 

AlbertHall

Joined Jun 4, 2014
12,345
Is that 60mV with the motor disconnected? If so all you are measuring is the leakage current.
If you leave enable floating it will enable the outputs. From the datasheet:
upload_2016-11-23_22-33-21.png
 

hp1729

Joined Nov 23, 2015
2,304
Dear colleagues,

I have to include an H-bridge in one of my PCB designs; this H-bridge presents a PDIP-16 package like the following one:

http://shannonstrutz.com/wp-content/uploads/2012/02/20-16-dip.jpg

My question is if you recommend me to use a socket like this:

http://techdelivers.com/40-pin-IC-base-socket-wide

or it is better to solder the chip directly on the PCB. One issue is that four of the 16 pins have to act as a heatsink, dissipating heat through a ground-plane with vias.

The IC I refer to is here:

http://www.ti.com/lit/ds/symlink/sn754410.pdf


Thanks in advance.
I think it needs the good mechanical contact for the heat sink. I say solder it to the board.
 
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