replacement triac for BGA welder

[Cornboats]

I have a Puhui BGA infra red welder. Its in pieces as there are so many things wrong with it I'm doing an upgrade so its usable again. Its poor quality and I wouldn't buy again-Puhui have gone bust anyway, but we are where we are so an upgrade is better than scrapping altogether. There are 2 identical triacs on the small circuit board, both BT139's. 1 is for the IR lamp- 20v AC and 1 is for 240V 800w pre-heater, it draws 10 amps so is nearer 1250 watts. The IR triac went down so I swopped the triac heater over just to establish everthing works and it does. So now I need a substitute triac as the BT139 800 is no longer available. The BT139 800 triac is 16A 600V.
I have in my stock new TIC246M triacs also rated at 16A 600V. Thats where the similarity ends. The Tic only operates in 1-3 quandrants, the BT in all 4 quadrants. I have no idea what that means-just got it off the spec sheets. Also gate current and gate holding voltages slightly different. Again I do not have the knowledge to know if this should be taken into account hence my post here.
Am I going to do irepairable damage by trying a Tic and would it be better operating the IR lamp or heater?

[petehall347]

Re: replacement triac for BGA welder

does rs components have anything suitable ?

[petehall347]

Re: replacement triac for BGA welder

they have then in stock . RS Stock No. 484-2814

[redwire]

Re: replacement triac for BGA welder

It's not a critical circuit, I would say you could drop in the TIC246M in place of BT139. The heating element is mostly a resistive load (it does have little inductance), so a 4-quadrant triac will work OK, the board also has snubbers anyhow.

One problem is the triac has a small heatsink? it will dissipate about 3-5W of heat at 800W/240VAC full on. The heatsink ends up hazardous live (connected to triac middle pin). Some triacs have isolated tab to make life easier.

Careful with these chinese boards- the heatsink can't be right on top of pcb traces, I use a strip of Kapton tape or an air gap so it doesn't short out to anything. It has to be clean because the PCB has small clearance between mains traces/pads and the low voltage side. Use IPA and q-tip to clean off the flux, no solder splats.

[Cornboats]

Re: replacement triac for BGA welder

Thanks for your replies. If I use the tic246m, would it be better switching the infra red light or the heater? I was going to fit independent heat sinks to both triacs and also install an additional fan, theres 1 already in the heater bay.

[Cornboats]

Re: replacement triac for BGA welder

Just an update. I fitted TIC246M triacs to both IR lamp and heater circuits. added an additional fan to keep circuit board cooler.
Works ok but haven't tested doing a reflow yet.
The 2 temperature displays read 10c different with similar probes into same heat source.
Thanks for those who replied.

[sam_sam_sam]

Re: replacement triac for BGA welder

Just an update. I fitted TIC246M triacs to both IR lamp and heater circuits. added an additional fan to keep circuit board cooler.
Works ok but haven't tested doing a reflow yet.
The 2 temperature displays read 10c different with similar probes into same heat source.
Thanks for those who replied.

Has your repair keep working or there other issues

[Cornboats]

Re: replacement triac for BGA welder

I haven't had an opportunity to test by reflowing yet. The only problem is the innacurate readout given by the 2 digital heat sensors. Theres a 10 degree c difference between the 2, using identical thermocouples sensing the same heat source.

[Deusjevoo]

Re: replacement triac for BGA welder

I haven't had an opportunity to test by reflowing yet. The only problem is the innacurate readout given by the 2 digital heat sensors. Theres a 10 degree c difference between the 2, using identical thermocouples sensing the same heat source.

You can use iced (0c) and boiling (100c) water to verify them.

[Cornboats]

Re: replacement triac for BGA welder

Update on the BGA welder repair. I've reflowed 2 bga's now and the pre heat element and ifa red lamp are working fine except theres no temperature control. I have to turn off the heat manually - but thats no big deal.
There is a wide difference in temperature measurement between the 2 on board temperature detectors. I have changed both 2 wire thermocouples so maybe I've used the wrong type. I based the replacement on what had been in before ie 2 wire red & black.