My house phone has an LCD to show numbers and information, but some of the LC segments do not light up making the display useless:-
Display should say FREESTYLEI thought there might be something wrong with the connection between the main board and the display, so I had a look. I was expecting a silicon zebra-stripe connector, which I've seen before, but this one uses a flexible connector that is heat bonded to the main board and the display. WARNING: be gentle with the flexible connector; it turns out the can tear quite easily 
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I thought maybe the bonding between the connector and the board had deteriorated causing some of the connections to become disconnected. So I thought I'd try rebonding the connections by using my soldering iron. I set my iron to 200oC and slowly ran the tip along the connector where it is bonded to the board. After the first attempt I noticed some of the LCD segments were back, and after a few more goes, the display was back to normal:-
a hot air gun works wonders, but one must not concentrate the heat too long or you will melt insulation and adjacent plastic. holding the nozzle back about 2 inches from the area you wish to get the connections fixed on, is a good plan, and is best done using an IR non contact thermometer pointed at the area being heated to monitor the temperature. and yes, make sure the ribbon is ‘sprung’ in a way so that it won’t ‘pop off’ the connection while being heated. A flat iron seems to be also a good plan if you use a ‘buffer’ between the iron and the ribbon to prevent too much heating. Sometimes re-visiting and testing has to happen more than one cycle so you get the affected areas fixed. a hot air gun and some ‘flux’ also are a good idea if you mask off the adjacent plastic areas to prevent melting and deforming of vulnerable plastic.