SMD VND5N07 use in the proto area (thru hole) advice

[BigLou240sx]

I'm planning my winter upgrades (I know... late start) to my DIYPNP to include adding sequential injection. I'd like to build the injector circuits myself, but wanted to seek advice on how to use SMD packaged components in the proto area with thru holes.

What is the best practice for connecting the tabbed drain on the SMD VND5N07 package to a thru hole? Small section of discarded leg from another component (I saved all of the leftovers when I first built this unit ) or other?

I realize this is probably a very elementary question, but I'd prefer to ask and reveal my novice level of electronics than make a mistake down the road. Thanks!

[racingmini_mtl]

I'm sorry but the best practice is to use through hole components on through hole pads and SMD components on SMD pads (on boards designed for it). Anything else is a kludge in my view. It might still be an acceptable compromise for you but I think you should change "best practice" to something like "least likely to fail".

Jean

[BigLou240sx]

No need to be sorry and thanks for the feedback. I agree with you on through hole for through hole and likewise for SMD, which is what prompted me to ask the question on here.

The problem I'm running into is that there doesn't appear to be a source for through hole VND5N07 components (at least through digikey and mouser) in quantities of less than 3000 approximately. The SMD variants can be bought one at a time.

I'm trying to mimic the following board layout:

In the picture, it's clear that the INJ3/4 outputs are routed from the through holes in the proto area, but what can't be seen is how the drain is brought down to the through hole.

I agree concerning your assessment of best practice vs least likely to fail; are there any recommendations for attempting this in order to minimize the possibility of failure? I would love to use a through hole component, but am striking out. Additionally, the sequential mod for DIYPNPs is fair, but I was honestly hoping to take a more DIY approach for the purposes of learning.

[racingmini_mtl]

If you can position the part such that you can solder the tab to 3 pads, that should help. There are 2 things that would be of concern to me: heat dissipation and mechanical stability. Making sure that you have solder going through the other side of the board at the solder joints should help both. But I would still try to add a dab of hot melt glue to put less stress on the joints.

But heat is usually dissipated through the board where the copper increases the heat rejecting surface significantly. You won't have that here even with a good amount of solder on all pads. Trying to find some way of compensating for this would certainly help long term reliability.

Jean

[BigLou240sx]

Thanks again for your feedback Jean.

After examining the picture, it appears that they are only using one through hole pad to bring the drain down to the proto area. I agree with your assessment it would be best if I could grab the three pads and solder them all to the drain to aid in heat dissipation. I will be conscientious of the heat dissipation and will remember to investigate the drivers after some hard use in the summer time (assuming that high injector duty cycle for extended periods of time is worse for the drivers). If needed, maybe I can place a small heat sink from some of the connected through holes (DIYPNPs proto area connects three through hole pads unlike the V3.0 mainboard I believe) to aid in dissipation. I assume the drivers are ok to touch as long as the board is powered off/car is not running. Maybe I'll also call on a friend with an infrared thermo to take a direct reading and compare to the resident microsquirt drivers.

My plan of attack will be to fill the three through holes with solder, and perhaps tin the drain tab before trying to attach the driver to the board. Then with solder in place on the proto area (and maybe the driver), I will locate the driver on the board and start apply heat to one of the through holes (and the drain) at a time and add solder to help build the connection.

OR, would it be worthwhile (and not detrimental to the integrity of the physical connection (whatever quantity of assumed integrity I'm starting with my soldering directly to the three through holes)) to try to build a small piece of thin copper that can fit in the through holes and bridge the three through holes on the proto area, and solder the driver to that? Just thinking out loud now...

[dontz125]

If you haven't already started, perhaps consider the VNP5N07-E TO-220 through-hole version; Mouser has 1600 on the shelf at $1.68 each.

[BigLou240sx]

If you haven't already started, perhaps consider the VNP5N07-E TO-220 through-hole version; Mouser has 1600 on the shelf at $1.68 each.

Sorry for the delay in responding and thanks again. That is a good suggestion that I'm seriously taking under consideration. I've looked over the datasheets, and over all, they match identically. Only place that doesn't match, is the "Turn-on Current Slope", which is listed as 35 A/us for the VNP5N07-E and 80 A/us for the VND5N07. I'm not knowledgeable enough to know how or how much this would affect real world use... any thoughts? If going down this route, I would also use a TO-220 heat sink.

In parallel with this thread, I also was posed with another recommendation by which to use the VND5N07, which is to use an electrically conductive (tinned copper) heatsink like the attached picture. If I go this route, I will cut some of the wings of the heat sink and modify a fin to use as a through-hole connector (cut so one fin is separate and bend down towards board). I haven't exactly played with lining up the through holes in this way yet, but think I can get it to work. This should not only help in the mechanical stability (used in conjunction with hot glue) but should also provide a sufficient electrical connection and proper heat dissipation.